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od 2020-09-20

Prof. dr hab. Maciej Kozak  | 1999-10 - obecnie

Kierownik Zakładu Fizyki Makromolekularnej od 2016-10-01
Prodziekan ds. organizacji i rozwoju

   WF UAM pokój: 136      +48 61-829-5266       mkozak@amu.edu.pl

  0000-0003-3312-6518     7102680957  

Zainteresowania naukowe:
Badania strukturalne układów biologicznych i polimerów, niskokątowe rozpraszanie promieniowania rentgenowskiego (SAXS), krystalografia białek

Publikacje      Projekty      Doktorzy      Magistrowie      Licencjusze      Seminaria


142.

Szutkowski K., Kołodziejska Ż., Pietralik Z., Zhukov I., Skrzypczak A., Materna K., Kozak M.

Clear distinction between CAC and CMC revealed by high-resolution NMR diffusometry for a series of bis-imidazolium gemini surfactants in aqueous solutions The aggregation behavior in the transition region was studied for a series of dicationic surfactants 3,3'-[alpha,omega-(dioxaalkane)]bis(1-dodecylimidazolium)dichlorides with varied spacer length from two to twelve carbon atoms. We employed Nuclear Magnetic Resonance diffusometry and Bayesian DOSY analysis to obtain the aggregate size distribution in the transition region. The critical concentrations CC were independently obtained from surface tension, electric conductivity, UV-Vis and NMR methods. The micelle aggregation numbers were estimated from the self-diffusion coefficients and were independently confirmed using steady-state fluorescence quenching. The morphology of the aggregates was characterized by small-angle scattering of synchrotron radiation and molecular dynamics simulations. The obtained CC values are identified as critical aggregation concentrations CAC. A broad transition region was observed, and stable micelles were obtained at much higher concentrations than CAC. The accurate CMC values could not be identified for the systems in the study. We indicated that the distribution of aggregate size becomes small and the system becomes homogeneous at much larger concentrations than CAC (typically 15-20 mM). The existence of a slow exchange between two environments, an aggregate and aqueous environment, was confirmed by H-1 NMR and 2D HSQC NMR spectroscopy.

RSC Advances, 8(67), 38470-38482 (2018)

DOI: 10.1039/c8ra07081d   (Pobrane:  2019-03-21)


141.

Neunert G., Tomaszewska-Gras J., Siejak P., Pietralik Z., Kozak M., Polewski K.

Disruptive effect of tocopherol oxalate on DPPC liposome structure: DSC, SAXS, and fluorescence anisotropy studies alpha-Tocopherol oxalate (TO), a tocopherol ester derivative, was investigated for its effect on the structural changes of fully hydrated 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) liposomes, as a function of concentration and temperature, by applying differential scanning calorimetry (DSC), small angle X-ray scattering (SAXS), and DPH fluorescence anisotropy methods. The DSC and DPH anisotropy data indicated that TO embedded into DPPC membrane lowered the enthalpy (Delta H-m) and temperature (T-m) of the main phase transition as well its cooperativity. Fluidization of the membrane at a lowered temperature was accompanied by formation of mixed structures of tocopherol-enriched domains. SAXS studies showed the formation of various ordered structures in DPPC gel-phase during incorporation of TO into the bilayer, as evidenced by the existence of lamellar phases with repeat distances (d) of 6.13 and 6.87 nm, assigned to TO-enriched domains and a lamellar, liquid-ordered DPPC phase with d = 8.45 nm at increasing TO concentrations with lowering and broadening of the Bragg peaks, and diffuse scattering, characteristic of a fluid L-alpha phase, were observed. In DPPC fluid-phase, the increasing presence of TO at low concentrations resulted in the appearance of a liquid-ordered phase with repeat d = 6.9 nm coexistent with a lamellar structure with d = 9.2 nm, assigned to liquid-disordered structures. An increasing repeat distance observed with raising the TO amount in the DPPC bilayer evolved from an increasing interlamellar water layer of increasing thickness. Presence of TO facilitated penetration of water molecules into the acyl chain region which decreased van der Waals interactions in the bilayer. The DSC, SAXS, and fluorescence anisotropy data established that TO exhibited pronounced disruptive activity in DPPC membranes compared to a-tocopherol. The driving force of the observed action was attributed to electrostatic and dipole interactions of the acidic moiety with the polar head group of phospholipids in the interface region of the bilayer.

Chemistry and Physics of Lipids, 216, 104-113 (2018)

DOI: 10.1016/j.chemphyslip.2018.10.001   (Pobrane:  2019-03-21)


140.

Paczkowska M., Mizera M, Salat K., Furgała A., Popik P., Knapik-Kowalczuk J., Krause A., Szymanowska-Powałowska D., Fojud Z., Kozak M., Paluch M., Cielecka-Piontek J

Enhanced pharmacological efficacy of sumatriptan due to modification of its physicochemical properties by inclusion in selected cyclodextrins The study focused on the pharmacological action of sumatriptan, in particular its antiallodynic and antihyperalgesic properties, as an effect of cyclodextrinic inclusion of sumatriptan, resulting in changes of its physicochemical qualities such as dissolution and permeability through artificial biological membranes, which had previously been examined in vitro in a gastro-intestinal model. The inclusion of sumatriptan into beta-cyclodextrin and 2-hydroxylpropylo-beta-cyclodextrin by kneading was confirmed with the use of spectral (fourier-transform infrared spectroscopy (FT-IR); solid state nuclear magnetic resonance spectroscopy with magic angle spinning condition, H-1 and C-13 MAS NMR) and thermal (differential scanning calorimetry (DSC)) methods. A precise indication of the domains of sumatriptan responsible for its interaction with cyclodextrin cavities was possible due to a theoretical approach to the analysis of experimental spectra. A high-performance liquid chromatography with a diode-array detector method (HPLC-DAD) was employed to determine changes in the concentration of sumatriptan during dissolution and permeability experiments. The inclusion of sumatriptan in complex with cyclodextrins was found to significantly modify its dissolution profiles by increasing the concentration of sumatriptan in complexed form in an acceptor solution compared to in its free form. Following complexation, sumatriptan manifested an enhanced ability to permeate through artificial biological membranes in a gastro-intestinal model for both cyclodextrins at all pH values. As a consequence of the greater permeability of sumatriptan and its increased dissolution from the complexes, an improved pharmacological response was observed when cyclodextrin complexes were applied.

Scientific Reports, 8, 16184 (2018)

DOI: 10.1038/s41598-018-34554-w   (Pobrane:  2019-03-19)


139.

Chrabąszczewska M., Maszota-Zieleniak M., Pietralik Z., Taube M., Rodziewicz-Motowidło S., Szymańska A., Szutkowski K., Clemens D., Grubb A., Kozak M.

Cyclic trimer of human cystatin C, an amyloidogenic protein - molecular dynamics and experimental studies Human cystatin C (HCC) is a cysteine protease inhibitor that takes a series of oligomeric forms in solution (e.g., dimers, trimers, tetramers, decamers, dodecamers, and other higher oligomers). The best-known form of cystatin C is the dimer, which arises as a result of a domain swapping mechanism. The formation of the HCC oligomeric forms, which is most likely due to this domain swapping mechanism, is associated with the aggregation of HCC into amyloid fibrils and deposits. To investigate the structure of a specific HCC oligomer, we developed a covalently stabilized trimer of HCC. An atomic model of this HCC trimer was proposed on the basis of molecular docking and molecular dynamics simulations. The most stable model of the HCC trimer obtained from the molecular dynamics simulations is characterized by a well-preserved secondary structure. The molecular size and structural parameters of the HCC trimer in solution were also confirmed by Small Angle Neutron Scattering and Nuclear Magnetic Resonance Diffusometry. Published by AIP Publishing.

Journal of Applied Physics, 123(17), Article Number: 174701 (2018)

DOI: 10.1063/1.5023807   (Pobrane:  2019-03-21)


138.

Wilkowska M., Andrzejewska W., Zieliński R., Kozak M.

Abstrakt lub materiały konferencyjne, albo abstrakt publikacji
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Amyloid beta peptide aggregation process in the presence of sugar-based surfactants- conformational and structural studies The progression of Alzheimer's Disease (AD) is caused by aggregation process of amyloid β peptide (Aβ) [1]. The aggregation mechanism of Aβ peptides is still under discussion, because the process of Aβ oligomerization is relatively fast and it can be affected by many variables [2]. The control of Aβ aggregation is very hard to achieve, but use of selected specific surfactants may contribute to a better understanding of this process. The aim of this study was characterization of the structure and conformational changes in β-amyloid peptides induced by the presence of zwitterionic, sugar-based surfactants comprising a lactose moiety. Several different variants of β-amyloid peptides were selected for the study. The effect of surfactant concentration in solution was tested on Aβ1-42 peptide and its shorter variants. Selected solutions of tested β-amyloid peptides with surfactants were subjected to a series of solution scattering experiments using the synchrotron radiation (SR-SAXS). The SAXS data for these surfactants were collected on P12 beam line of EMBL (DESY). SR-SAXS studies exhibited the structure of various mixed (peptide-surfactant) assemblies. In our study we analyzed also the secondary structure of Aβ peptide in solutions with different concentrations of surfactant, using FTIR spectroscopy and circular dichroism (CD) methods. Atomic force microscopy (AFM) was used to characterize the morphology of Aβ assemblies. Particular attention was paid to analysis of small soluble oligomers that are currently believed to initiate development of brain disfunction in AD.

[1] J. Hardy and D. J. Selkoe, Science, 2002.
[2] J. A. Loureiro, S. Rocha, and M. do C. Pereira, J. Pept. Sci. Off. Publ. Eur. Pept. Soc., 2013.

Acknowledgments: The study was supported by research grant, Grant Diamentowy’’ from Ministry of Science and Higher Education (Poland) - DEC: 0011/DIA2015/44.

Biophysical Journal, 114(3) S1, 221A (2018)

DOI: 10.1016/j.bpj.2017.11.1233   (Pobrane:  2020-07-21)


137.

Razew M., Warkocki Z., Taube M., Kolondra A., Czarnocki-Cieciura M., Nowak E., Łabędzka-Dmoch K., Kawińska A., Piątkowski J., Golik P., Kozak M., Dziembowski A., Nowotny M.

Structural analysis of mtEXO mitochondrial RNA degradosome reveals tight coupling of nuclease and helicase components Nuclease and helicase activities play pivotal roles in various aspects of RNA processing and degradation. These two activities are often present in multi-subunit complexes from nucleic acid metabolism. In the mitochondrial exoribonuclease complex (mtEXO) both enzymatic activities are tightly coupled making it an excellent minimal system to study helicase-exoribonuclease coordination. mtEXO is composed of Dss1 3'-to-5' exoribonuclease and Suv3 helicase. It is the master regulator of mitochondrial gene expression in yeast. Here, we present the structure of mtEXO and a description of its mechanism of action. The crystal structure of Dss1 reveals domains that are responsible for interactions with Suv3. Importantly, these interactions are compatible with the conformational changes of Suv3 domains during the helicase cycle. We demonstrate that mtEXO is an intimate complex which forms an RNA-binding channel spanning its entire structure, with Suv3 helicase feeding the 3' end of the RNA toward the active site of Dss1.

Nature Communications, 9, 97 (2018)

DOI: 10.1038/s41467-017-02570-5   (Pobrane:  2020-07-21)


136.

Mieloch A.A., Kręcisz M., Rybka J.D., Strugała A., Krupiński M., Urbanowicz A., Kozak M., Skalski B., Figlerowicz M., Giersig M.

The influence of ligand charge and length on the assembly of Brome mosaic virus derived virus-like particles with magnetic core Virus-like particles (VLPs) have sparked a great interest in the field of nanobiotechnology and nanomedicine. The introduction of superparamagnetic nanoparticles (SPI-ONs) as a core, provides potential use of VLPs in the hyperthermia therapy, MRI contrast agents and magnetically-powered delivery agents. Magnetite NPs also provide a significant improvement in terms of VLPs stability. Moreover employing viral structural proteins as self-assembling units has opened a new paths for targeted therapy, drug delivery systems, vaccines design, and many more. In many cases, the self-assembly of a virus strongly depends on electrostatic interactions between positively charged groups of the capsid proteins and negatively charged nucleic acid. This phenomenon imposes the negative net charge as a key requirement for the core nanoparticle. In our experiments, Brome mosaic virus (BMV) capsid proteins isolated from infected plants Hordeum vulgare were used. Superparamagnetic iron oxide nanoparticles (Fe3O4) with 15 nm in diameter were synthesized by thermal decomposition and functionalized with COOH-PEG-PL polymer or dihexadecylphosphate (DHP) in order to provide water solubility and negative charge required for the assembly. Nanoparticles were characterized by Transmission Electron Microscopy (TEM), Dynamic Light Scattering (DLS), Zeta Potential, Fourier Transformed Infrared Spectroscopy (FTIR) and Superconducting Quantum Interference Device (SQUID) magnetometry. TEM and DLS study were conducted to verify VLPs creation. This study demonstrates that the increase of negative surface charge is not a sufficient factor determining successful assembly. Additional steric interactions provided by longer ligands are crucial for the assembly of BMV SPION VLPs and may enhance the colloidal stability.

AIP Advances, 8(3), 035005 (2018)

DOI: 10.1063/1.5011138   (Pobrane:  2020-07-21)


135.

Kucharczyk K., Weiss M., Jastrzębska K., Łuczak M., Ptak A., Kozak M., Mackiewicz A., Dams-Kozłowska H.

Bioengineering the spider silk sequence to modify its affinity for drugs Background: Silk is a biocompatible and biodegradable material, able to self-assemble into different morphological structures. Silk structures may be used for many biomedical applications, including carriers for drug delivery. The authors designed a new bioengineered spider silk protein, EMS2, and examined its property as a carrier of chemotherapeutics. Materials and methods: To obtain EMS protein, the MS2 silk monomer (that was based on the MaSp2 spidroin of Nephila clavipes) was modified by the addition of a glutamic acid residue. Both bioengineered silks were produced in an Escherichia coli expression system and purified by thermal method. The silk spheres were produced by mixing with potassium phosphate buffer. The physical properties of the particles were characterized using scanning electron microscopy, atomic force microscopy, Fourier-transform infrared spectroscopy, and zeta potential measurements. The MTT assay was used to examine the cytotoxicity of spheres. The loading and release profiles of drugs were studied spectrophotometrically. Results: The bioengineered silk variant, EMS2, was constructed, produced, and purified. The EMS2 silk retained the self-assembly property and formed spheres. The spheres made of EMS2 and MS2 silks were not cytotoxic and had a similar secondary structure content but differed in morphology and zeta potential values; EMS2 particles were more negatively charged than MS2 particles. Independently of the loading method (pre- or post-loading), the loading of drugs into EMS2 spheres was more efficient than the loading into MS2 spheres. The advantageous loading efficiency and release rate made EMS2 spheres a good choice to deliver neutral etoposide (ETP). Despite the high loading efficiency of positively charged mitoxantrone (MTX) into EMS2 particles, the fast release rate made EMS2 unsuitable for the delivery of this drug. A faster release rate from EMS2 particles compared to MS2 particles was observed for positively charged doxorubicin (DOX). Conclusion: By modifying its sequence, silk affinity for drugs can be controlled.

International Journal of Nanomedicine, 13, 4247-4261 (2018)

DOI: 10.2147/IJN.S168081   (Pobrane:  2020-07-21)


134.

Andrzejewska W.J., Wilkowska M., Peplińska B., Kozak M.

Abstrakt lub materiały konferencyjne, albo abstrakt publikacji
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Selected polycationic surfactants as sirna carriers for gene therapy So far many drug delivery systems for transfer of nucleic acids in gene therapy have been proposed but there is no universal system for transfer of genetic material into cells. The largest problem in the design of new nucleic acids delivery vehicles is finding a carrier which fulfill such criteria as: stability in complexes with nucleic acids, non-toxicity, non-immunogenicity, ability to safe degradation and easy preparation protocol.

A certain group of polycationic surfactants are able to meet these requirements. Their amphiphilic nature, structure flexibility and the ability to bind to siRNA or DNA oligomers are just some of the advantages. Our past research on selected dicationic compounds as DNA or siRNA delivery systems, indicated that an increase in the number of surfactant subunits is a promised direction to develop new efficient carriers of short nucleic acids.

In this work we present results of the studies of the complexes based on selected novel polycationic surfactants (eg. oligomeric imidazolium derivatives) with a model system - double stranded 21-bp siRNA oligomer. By the use of biophysical methods (electrophoresis, circular dichroism, small angle scattering of synchtorton radiation and cryo-transmission electron microscopy) we examined their complexation capacity, nanostructure of lipoplexes, conformational changes in bound siRNA oligomers and micromorphology of complexes. Our studies have shown the formation of stable systems with promising transfection properties. These systems exhibit various morphologies in frozen state.

Acknowledgments: The study was supported by research grant “PRELUDIUM” from National Science Center (Poland) - UMO-2016/23/N/ST4/01637.

Biophysical Journal, 114(3) S1, 438A (2018)

DOI: 10.1016/j.bpj.2017.11.2424   (Pobrane:  2020-11-05)


133.

Hołubowicz R., Wojtas M., Taube M., Kozak M., Ozyhar A., Dobryszycki P.

Effect of calcium ions on structure and stability of the C1q-like domain of otolin-1 from human and zebrafish Otolin-1 is a collagen-like protein expressed in the inner ear of vertebrates. It provides an organic scaffold for otoliths in fish and otoconia in land vertebrates. In this study, the expression and purification procedure of C1q-like domain of otolin-1 from human and zebrafish was developed. The structure and stability of the proteins were investigated. The results of sedimentation velocity analytical ultracentrifugation and small-angle X-ray scattering indicated that the C1q-like domain of otolin-1 forms stable trimers in solution in the presence of calcium ions. It was also observed that calcium ions influenced the secondary structure of the proteins. C1q-like domains were stabilized by the calcium ions. The human variant was especially affected by the calcium ions. The results indicate the importance of the C1q-like domain for the assembly of the organic matrix of otoliths and otoconia.

FEBS Journal, 284(24), 4278-4297 (2017)

DOI: 10.1111/febs.14308   (Pobrane:  2018-04-03)


132.

Murawska M., Szymańska A., Grubb A., Kozak M.

Overall conformation of covalently stabilized domain-swapped dimer of human cystatin C in solution Human cystatin C (HCC), a small protein, plays a crucial role in inhibition of cysteine proteases. The most common structural form of human cystatin C in crystals is a dimer, which has been evidenced both for the native protein and its mutants. In these structures, HCC dimers were formed through the mechanism of domain swapping. The structure of the monomeric form of human cystatin C was determined for V57N mutant and the mutant with the engineered disulfide bond (L47C)–(G69C) (known as stab1-HCC). On the basis of stab1-HCC, a number of covalently stabilized oligomers, including also dimers have been obtained. The aim of this study was to analyze the structure of the covalently stabilized dimer HCC in solution by the small angle X-ray scattering (SAXS) technique and synchrotron radiation. Experimental data confirmed that in solution this protein forms a dimer, which is characterized by the radius of gyration RG = 3.1 nm and maximum intramolecular distance Dmax = 10.3 nm. Using the ab initio method and program DAMMIN, we propose a low resolution structure of stabilized covalently cystatin C in solution. Stab-HCC dimer adopts in solution an elongated conformation, which is well reconstructed by the ab initio model.

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 411, 136-140 (2017)

DOI: 10.1016/j.nimb.2017.02.090   (Pobrane:  2017-12-13)


131.

Nowakowski M., Czapla-Masztafiak J., Kozak M., Zhukov I., Zhukova L., Szlachetko J., Kwiatek W.M.

Preliminary results of human PrPC protein studied by spectroscopic techniques Neurodegenerative diseases are one of the malfunctions of human nervous system, being a class of complex and prominent pathologies. The human prion Protease Resistant Protein (PrP) is protein regulating copper metabolism in mammalian cells through binding of Cu(II) ions to specific fragments. Nowadays misfolding of this protein is associated with development of prion diseases. Therefore, it is crucial to obtain structural information about coordination of Cu(II) by PrP protein. Herein, we report X-ray absorption spectroscopy (XAS) measurements, carried out on SuperXAS beamline (SLS, PSI Villigen) on PrPC-Cu(II) complexes. Obtained results were compared with theoretical predictions done by FEFF 9.6 software. Complementary to XAS data, Atomic Force Microscopy (AFM) measurements were conducted to obtain low resolution structural information about prepared sample that allow to develop protocol of fixing PrPC molecules on solid substrate used for further experiments. It has been established that folded C-terminal domain of PrPC protein has around 5 nm in diameter. Presented results showed that both XAS and AFM methods are useful tools in detailed examination of complexes of human PrPC either with Cu(II) or with other divalent metal ions.

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 411, 121-128 (2017)

DOI: 10.1016/j.nimb.2017.06.022   (Pobrane:  2017-12-14)


130.

Piosik A., Żurowski K., Pietralik Z., Hędzelek W., Kozak M.

Structural studies of degradation process of zirconium dioxide tetragonal phase induced by grinding with dental bur Zirconium dioxide has been widely used in dental prosthetics. However, the improper mechanical treatment can induce changes in the microstructure of zirconium dioxide. From the viewpoint of mechanical properties and performance, the phase transitions of ZrO2 from the tetragonal to the monoclinic phase induced by mechanical processing, are particularly undesirable. In this study, the phase transitions of yttrium stabilized zirconium dioxide (Y-TZP) induced by mechanical treatment are investigated by the scanning electron microscopy (SEM), atomic force microscopy (AFM) and powder diffraction (XRD). Mechanical stress was induced by different types of drills used presently in dentistry. At the same time the surface temperature was monitored during milling using a thermal imaging camera. Diffraction analysis allowed determination of the effect of temperature and mechanical processing on the scale of induced changes. The observed phase transition to the monoclinic phase was correlated with the methods of mechanical processing.

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 411, 85-93 (2017)

DOI: 10.1016/j.nimb.2017.07.024   (Pobrane:  2017-12-08)


129.

Tarczewska A., Kozłowska M., Bystranowska D., Jakob M., Taube M., Kozak M., Czarnocki-Cieciura M., Ozyhar A.

European Biophysics Journal with Biophysics Letters, 46(S1), S177-S177 (2017)

   (Pobrane:  2018-04-03)


128.

Dobies M., Iżykowska J., Wilkowska M., Woźniak-Braszak A., Szutkowski K., Skrzypczak A., Jurga S., Kozak M.

Dispersion of water proton spin-lattice relaxation rates in aqueous solutions of multiwall carbon nanotubes (MWCNTs) stabilized via alkyloxymethylimidazolium surfactants Carbon nanotubes and a number of other carbon nanomaterials have a tendency to aggregate, which often resulted in difficulties of dispersion of these nanomaterials in aqueous solutions. The ability of dicationic (gemini) surfactants to disperse multiwall carbon nanotubes in water and the dynamic processes taking place at the water-MWCTs interface are studied. Stable dispersions of multi-wall carbon nanotubes with selected gemini surfactants (1,1’-(1,6-hexanediyl)bis(3-alkyloxymethylimidazolium) dichlorides) were prepared and characterized by nuclear magnetic relaxation dispersion (NMRD), NMR diffusometry, scanning and transmission electron microscopy, and Fourier transform infrared spectroscopy. The addition of multiwall carbon nanotubes to aqueous solutions of studied gemini surfactants leads to significant paramagnetic enhancement of the spin-lattice relaxation processes, which gets more pronounced with increasing concentration of well-dispersed MWNTs in water. The dominant role of outer sphere (OS) relaxation mechanism in total observed R1, governed by two-dimensional diffusion of water on the carbon nanotube surface in the vicinity of paramagnetic centers incorporated in the MWCNTs side-walls (mainly of iron origin), was assumed to explain NMRD data. The NMR diffusion experiments confirm the existence of restricted water diffusion in the studied supernatants. The NMR diffusion results are consistent with the FTIR and NMR proton spin-lattice relaxation dispersion in which the more effective R1 dispersion noticed for the sample with IMIC6C12 was ascribed to the better accessibility of water molecules to the surface of the MWCNTs.

The Journal of Physical Chemistry, 121(21), 11839-11850 (2017)

DOI: 10.1021/acs.jpcc.7b01801


127.

Andrzejewska W., Wilkowska M., Chrabąszczewska M., Kozak M.

The study of complexation between dicationic surfactants and the DNA duplex using structural and spectroscopic methods Dicationic (also known as gemini or dimeric) bis-alkylimidazolium surfactants belong to a group of non-viral transfection systems proposed for the successful introduction of different types of nucleic acids (i.e., siRNA, DNA oligomers, and plasmid DNA) into living cells. Our studies reveal the formation of complexes composed of dicationic (gemini) surfactants, 3,3′-[α,ω-(dioxaalkane)]bis(1-dodecylimidazolium)chlorides, and 21 base pair deoxyribonucleic acid duplexes (dsDNA). The studied dsDNA and its complex formation process was analysed by small-angle X-ray scattering (SAXS), molecular modelling (dsDNA), agarose gel electrophoresis (AGE) and circular dichroism spectroscopy (CD). We observed the formation of stable complexes for charge ratio values of p/n > 2. Moreover, we noted conformational changes similar to those observed during the transition of B-DNA to C-DNA, X-DNA, and Z-DNA in several spatial structures (i.e., micellar, hexagonal and cubic) formed in mixtures. The surfactants used in this study were investigated for the influence of dioxaalkane spacer length and the presence of an imidazolium moiety on the complexation process. The complexes formed were stable, and the complexation process was reproducible and efficient. Toxicity tests done on HeLa cells allowed for the determination of non-toxic concentrations of studied surfactants. Transfection tests have confirmed that the studied surfactant systems are effective DNA carriers.

RSC Advances, 7(42), 26006-26018 (2017)

DOI: 10.1039/c6ra24978g   (Pobrane:  2020-10-23)


126.

Moliński A., Zaręba J., Iżykowska J., Skupin M., Andrzejewska W., Jurga S., Kozak M.

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C-60 fullerenes as contrast agents - structural, spectroscopic and nano-toxicity studies Recently, C60 fullerenes have been proposed as contrast agents for MRI method [1]. Especially promising for in vitro and in vivo NMR imaging are their complexes with gadolinum (containing Gd3+ ions entrapped inside the fullerene cage) known also as gadofullerenes [2]. The general problem of carbon nanomaterials is their toxicity towards living cells [3]. The aim of our study is to devise fullerene-based suspensions characterized with low toxicity, which could later be developed into metallofullerene contrast agents. We want to achieve that goal using C60 fullerenes, pluronics to lower the toxicity and phosphatidylcholine derivatives (DMPC or DPPC) to enhance biocompatibility of fullerenes and to stimulate the cellular absorption. In this work we would like to present results of toxicity studies of C60 fullerene systems pluronic modified C60 fullerene systems towards HeLa cells, along with results of structural analyses by AFM and SEM microscopies, FTIR and SAXS. This study was supported by Ministry of Science and Higher Education (Poland), within the project, Najlepsi z najlepszych!”

Biophysical Journal, 112(3) S1, 593A (2017)

DOI: 10.1016/j.bpj.2016.11.3191   (Pobrane:  2020-11-05)


125.

Skupin M., Iżykowska J., Andrzejewska W., Dobies M., Jurga S., Kozak M.

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Interactions of carbon nanotubes stabilized by selected gemini surfactants with model biomembranes Thanks to the extraordinary mechanical strength and high electrical conductivity multiwalled carbon nanotubes are currently used in electronics, medicine (as biomedical sensors, transporters or drugs) as well as in the production of lightweight and durable construction. The aim of this study was to determine the possibility to use different cationic gemini surfactants with different spacer lengths or alkyl chain lengths in more efficient systems for dispersing nanostructures in aqueous solutions. The most important advantages of these systems are their non-immunogenic, biocompatible properties and generally low toxicity . Therefore nanotubes, surrounded by surfactants, have the potential to interact with biological membranes. For this purpose we studied the influence of dispersed CN solution on the phase behavior of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) - a phospholipid most often present in membranes of nerve cells. The microstructure of the stable suspension of carbon nanotubes was investigated using high-resolution Transmission Electron Microscopy and Atomic Force Microscopy. Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC) were used to analyze the influence of surfactants studied, used for CN dispersion, on the phase behavior of DMPC bilayers. A series of measurements of toxicity of these systems were performed in HeLa and fibroblast cell cultures. This work was supported by the Ministry of Science and Higher Education, within the project “Najlepsi z najlepszych!” dec.

Biophysical Journal, 112(3) S1, 77A (2017)

DOI: 10.1016/j.bpj.2016.11.460   (Pobrane:  2020-11-05)


124.

Kozak M., Gielnik M., Taube M., Zhukov I.

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Spectroscopic and SAXS studies of human prion protein variants complexed with divalent cations Neurodegenerative diseases are probably the most difficult diseases to find for them a successful treatment strategy. The discovery of new potential drugs, which can be useful in the treatment of neurodegenerative diseases, require full structural characterization of all proteins involved in development of these diseases. One of the human neurodegenerative disorders is Creutzfeldt-Jakob disease (CJD). This disease is caused by misfolded (pathogenic) form of prion protein (PrP), which is a membrane protein exposed into synaptic cleft [1]. So far, the structures of several variants of prion proteins from various organisms (hamster, bovine or human) have been solved by protein crystallography and NMR. The molecule of cellular form of human PrP protein is composed of two domains: unstructured and flexible N-terminal domain containing four tandem octarepeats and structured C-terminal domain [2]. The aim of our study was to obtain the structural information for several complexes of the human prion protein. As an object of the study presented here we have chosen the cellular form of human prion protein PrPC (23-231) and its mutant form (H61A). The low resolution structures of both forms complexed with divalent cations were characterized by SAXS technique. The conformational changes of proteins studied were also detected by spectrofluorimetry, circular dichroism and NMR. This work was supported by the funds from the National Science Centre (Poland) granted on the basis of decision no. No. 2014/15/B/ST4/04839

Biophysical Journal, 112(3) S1, 190A (2017)

DOI: 10.1016/j.bpj.2016.11.1053   (Pobrane:  2020-11-05)


123.

Andrzejewska W.J., Skupin M., Skrzypczak A., Kozak M.

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Dicationic and tricationic surfactants as transgene carriers - comparison of their ability to dsdna and sirna binding In last decades, many different compounds have been tested as potential delivery systems of nucleic acids in gene therapy. Compounds subjected for delivery of nucleic acids should be characterized by low toxicity and high ability to form stable complexes with nucleic acids. In practice they should support efficient transfer of therapeutic material (transgene) to the pathological cells. Introduced transgene by interaction with the corresponding cellular genome induce a permanent curative effect. Our previous study indicated, that good transfection properties, have three-dimensional structures formed by self-organized compounds which are structurally similar to the natural lipids. Particularly, new oligomeric amphiphiles, dicationic and tricationic surfactants, seems to be quite promising. The physicochemical properties of these compounds promote their ability to create a stable, biocompatible complexes with dsDNA and siRNA. In this work we present results of structural studies of the complexes formed on the basis of selected novel dicationic or tricationic surfactants with short nucleic acid oligomers (dsDNA and siRNA, 21 bp). These systems were examined by the use of atomic force microscopy (AFM), small angle scattering of synchrotron radiation (SR-SAXS), circular dichroism (CD) and gel electrophoresis. We performed also toxicity tests on HeLa cells. Studies have shown formation of stable systems with the desired biological and chemical properties.

Biophysical Journal, 112(3) S1, 214A (2017)

DOI: 10.1016/j.bpj.2016.11.1183   (Pobrane:  2020-11-05)


122.

Iżykowska J., Skupin M., Andrzejewska W., Dobies M., Jurga S., Kozak M.

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Carbon nanostructures of different spatial geometry: their dispersion and influence on model biological systems The discovery of carbon nanostructures (CN) in the last century has revolutionized science, opening new research opportunities in biophysics, material sciences, biomedicine and pharmacology [1]. Unfortunately, carbon nanomaterials show a strong tendency towards aggregation and poor stability in solutions. Such properties, especially the suspension stability, are critical for bio-applications of carbon nanostructures [2]. Surface functionalization of nanocarbons improves the dispersing properties in water solutions but it may also influence their physicochemical properties [3]. For preparation of biocompatible CN samples we used novel dicationic surfactant (gemini) with imidazole head groups. Nanocarbon suspensions were investigated in the context of their anticancer activity, as well as their application as multimodal contrast/drug delivery agents. Different spatial geometries of CN may be of key importance for designing of the efficient anti-cancer system. Such systems were subjected to the cytotoxicity tests on HeLa cell cultures. The structural properties of selected, the most effective systems based on CN suspensions were characterized by the use of SEM, AFM and NMR methods. This study was supported by the Ministry of Science and Higher Education (Poland), within the project “Najlepsi z najlepszych!”

Biophysical Journal, 112(3) S1, 156A (2017)

DOI: 10.1016/j.bpj.2016.11.857   (Pobrane:  2020-11-05)


121.

Zaręba J., Iżykowska J., Skupin M., Moliński A., Dobies M., Jurga S., Kozak M.

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The influence of surfactant structure and geometry on nanotoxicity and dispersion of carbon nanotubes Graphene, nanotubes and fullerenes, also known as carbon nanomaterials (CN), because of the their unique properties have potential applications not only in preparation of new composite materials or in electronics, but they can be also components of drug delivery systems. However, the applications of CN in life sciences or biomedicine require stable dispersions of these materials in water. The hydrophobic nature of CN causes serious problems with their separation in water solutions. Our study is aimed to find a way of dispersing such CN systems in water, by the use of non-covalent surface modification via different surfactants. In this work we focused on the use of trimeric, dimeric and monomeric surfactants fornon-covalent surface modification of selected carbon nanotubes. The toxicity of these systems (aqueous solutions of CN with surfactants and surfactants solutions) towards selected cell cultures (e. g. HeLa cells) was also tested. The surfactants studied can interact with carbon nanotubes in a number of different modes: hydrophobic interactions (surfactant chains with CN side walls) or π-π interactions (aromatic rings of surfactants with CN surface). Infrared spectroscopy and atomic force microscopy were used for characterization of the systems studied. Finally, we focused on mechanical properties of cells exposed to surfactants and CN. This study was supported by the Ministry of Science and Higher Education (Poland), within the project “

Biophysical Journal, 112(3) S1, 156A (2017)

DOI: 10.1016/j.bpj.2016.11.858   (Pobrane:  2020-11-05)


120.

Gospodarczyk W., Kozak M.

The severe impact of in vivo-like microfluidic flow and the influence of gemini surfactants on amyloid aggregation of hen egg white lysozyme The formation of amyloid plaques is being intensively studied, as this process underlies severe human diseases, including Alzheimer's disease, and the exact mechanism of this specific aggregation has not been resolved yet. The investigation of its formation is accompanied by the search for substances inhibiting this aggregation process. Here we studied the process of hen egg white lysozyme (HEWL) amyloid aggregation process in bulk solution within a time scale of about a week. We also examined the influence of four dicationic (gemini) surfactants, including 3,3′-[1,6-(2,5-dioxahexane)]bis-(1-dodecylimidazolium) dichloride (oxyC2), as well as selected reference sulfobetaines, on the aggregation process and found that at certain concentrations gemini surfactants remarkably inhibited amyloidogenesis. A microfluidic system was designed to mimic the in vivo-like conditions of flow in order to assess the influence of flow on the amyloid formation process. The flow was found to induce severe amyloid formation in just a few hours of exposition to the conditions which without flow would induce amyloidogenesis within a few days. The results shed light on the mechanisms responsible for the amyloid aggregation process and make an important contribution to understanding of the process.

RSC Advances, 7, 10973-10984 (2017)

DOI: 10.1039/c6ra26675d   (Pobrane:  2021-01-10)


119.

Kolonko M., Ożga K., Hołubowicz R., Taube M., Kozak M., Ożyhar A., Greb-Markiewicz B.

Intrinsic disorder of the C-terminal domain of drosophila methoprene-tolerant protein Methoprene tolerant protein (Met) has recently been confirmed as the long-sought juvenile hormone (JH) receptor. This protein plays a significant role in the cross-talk of the 20-hydroxyecdysone (20E) and JH signalling pathways, which are important for control of insect development and maturation. Met belongs to the basic helix-loop-helix/Per-Arnt-Sim (bHLH-PAS) family of transcription factors. In these proteins, bHLH domains are typically responsible for DNA binding and dimerization, whereas the PAS domains are crucial for the choice of dimerization partner and the specificity of target gene activation. The C-terminal region is usually responsible for the regulation of protein complex activity. The sequence of the Met C-terminal region (MetC) is not homologous to any sequence deposited in the Protein Data Bank (PDB) and has not been structurally characterized to date. In this study, we show that the MetC exhibits properties typical for an intrinsically disordered protein (IDP). The final averaged structure obtained with small angle X-ray scattering (SAXS) experiments indicates that intrinsically disordered MetC exists in an extended conformation. This extended shape and the long unfolded regions characterise proteins with high flexibility and dynamics. Therefore, we suggest that the multiplicity of conformations adopted by the disordered MetC is crucial for its activity as a biological switch modulating the cross-talk of different signalling pathways in insects.

PloS ONE, 11(9), 598-606 (2016)

DOI: 10.1371/journal.pone.0162950


118.

Andrzejewska W., Pietralik Z., Skupin M., Kozak M.

Structural studies of the formation of lipoplexes between siRNA and selected bis-imidazolium gemini surfactants Dicationic (gemini) surfactants are agents that can be used for the preparation of stable complexes of nucleic acids, particularly siRNA for therapeutic purposes. In this study, we demonstrated that bis-imidazolium gemini surfactants with variable lengths of dioxyalkyl linker groups (from dioxyethyl to dioxydodecyl) and dodecyl side chains are excellent for the complexation of siRNA. All of these compounds effectively complexed siRNA in a charge ratio range (p/n) of 1.5-10. The low resolution structure of siRNA oligomers was characterised by small angle scattering of synchrotron radiation (SR-SAXS) and ab initio modelling. The structures of the formed complexes were also analysed using SR-SAXS, circular dichroism studies and electrophoretic mobility tests. The most promising agents for complexation with siRNA were the surfactants that contained dioxyethyl and dioxyhexyl spacer groups.

Colloids and Surfaces B: Biointerfaces, 146, 598-606 (2016)

DOI: 10.1016/j.colsurfb.2016.06.062   (Pobrane:  2016-10-11)


117.

Jastrzębska K., Felcyn E., Kozak M., Szybowicz M., Buchwald T., Pietralik Z., Jesionowski T., Mackiewicz A., Dams-Kozłowska H.

The method of purifying bioengineered spider silk determines the silk sphere properties Bioengineered spider silks are a biomaterial with great potential for applications in biomedicine. They are biocompatible,biodegradable and can self-assemble into films, hydrogels, scaffolds, fibers, capsules and spheres. A novel, tag-free, bioengineered spider silk named MS2(9x) was constructed. It is a 9-mer of the consensus motif derived from MaSp2- the spidroin of Nephila clavipes dragline silk. Thermal and acidic extraction methods were used to purify MS2(9x). Both purification protocols gave a similar quantity and quality of soluble silk; however, they differed in the secondary structure and zeta potential value. Spheres made of these purified variants differed with regard to critical features such as particle size, morphology, zeta potential and drug loading. Independent of the purification method, neither variant of the MS2(9x) spheres was cytotoxic, which confirmed that both methods can be used for biomedical applications. However, this study highlights the impact that the applied purification method has on the further biomaterial properties.

Scientific Reports, 6, 28106, 1-15 (2016)

DOI: 10.1038/srep28106


116.

Skupin M., SobczaK, K., Zieliński R., Kozak M.

The system with zwitterionic lactose-based surfactant for complexation and delivery of small interfering ribonucleic acid-A structural and spectroscopic study Systems suitable for the effective preparation of complexes with siRNA (small interfering RNA) are at the center of interest in the area of research work on the delivery of the RNA-based drugs (RNA-therapeutics). This article presents results of a study on the structural effects associated with siRNA complexation by a surfactant comprising a lactose group (N-(3-propanesulfone)-N-dodecyl-amino-beta-D-lactose hydrochloride, LA12). The double stranded siRNA oligomer (21 base pairs) used in this study is responsible for silencing a gene that can be important in the therapy of myotonic dystrophy type 1. The obtained siRNA/LA12 lipoplexes were studied using the methods of small angle scattering of synchrotron radiation, circular dichroism spectroscopy, Fourier transform infrared spectroscopy, and electrophoretic mobility tests. Lipoplexes form in solution stable lamellar or cubic phases. The surfactant selected for the study shows much lower cytotoxicity and good complexation abilities of siRNA than dicationic or polycationic surfactants.

Applied Physics Letters, 108, 213701 (2016)

DOI: 10.1063/1.4952589


115.

Pietralik Z., Skrzypczak A., Kozak M.

Dicationic surfactants with glycine counter ions for oligonucleotide transportation Gemini surfactants are good candidates to bind, protect, and deliver nucleic acids. Herein, the concept of amino acids (namely glycine) as counter ions of gemini surfactants for gene therapy application was explored. This study was conducted on DNA and RNA oligomers and two quaternary bis-imidazolium salts, having 2,5-dioxahexane and 2,8-dioxanonane spacer groups. The toxicity level of surfactants was assessed by an MTT assay, and their ability to bind nucleic acids was tested through electrophoresis. The nucleic acid conformation was established based on circular dichroism and infrared spectroscopic analyses. The structures of the formed complexes were characterized by small-angle scattering of synchrotron radiation. Both studied surfactants appear to be suitable for gene therapy; however, although they vary by only three methylene groups in the spacer, they differ in binding ability and toxicity. The tested oligonucleotides maintained their native conformations upon surfactant addition and the studied lipoplexes formed a variety of structures. In systems based on a 2,5-dioxahexane spacer, a hexagonal phase was observed for DNA-surfactant complexes and a micellar phase was dominant with RNA. For the surfactant with a 2,8-dioxanonane spacer group, the primitive cubic phase prevailed.

ChemPhysChem, 17, 2424-2433 (2016)

DOI: 10.1002/cphc.201600175


114.

Skupin M., Kozak M.

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Study of molecular mechanisms of amyloid beta-peptid variants aggregation in presence of surfactants It is estimated that in 2050 at least 1.25 % of population might have Alzheimer's disease. It is supposed that the most critical changes relevant for the progress of this disease are related to development and deposition of amyloid plaque whose main components are amyloid β-peptides (Aβ).
The aim of this study was characterization of the structure and conformational changes of β-amyloid peptides in the presence of a wide group of surfactants. The kinetic study of the aggregation behavior of different peptides in solution was also undertaken. Four groups of surfactants (cationic, dicationic, tricationic and zwitterionic) and different β-amyloid peptides were selected for the study. The surfactant concentration effect was tested on 1-42 Aβ peptide and its shorter variants (N-terminal with hydrophilic properties and hydrophobic C-terminal fragment).
Analysis of the secondary structure of Aβ peptide in the presence of different concentrations of surfactants as well as a function of temperature, was carried out using FTIR spectroscopy and circular dichroism method. The kinetics of aggregation processes of the peptides and formation of plaques was studied using fluorescence spectroscopy and Thioflavin T assay. The size distribution of aggregates of Aβ peptide was evaluated on the basis of gel electrophoresis.
Results of our study showed different impact of surfactants studied on the conformations of beta-amyloid peptides. Preliminary examination of the cytotoxicity of selected surfactants on HeLa cells was conducted in order to verify their suitability for therapeutic purposes.

Biophysical Journal, 110(3) S1, 533A (2016)

DOI: 10.1016/j.bpj.2015.11.2855   (Pobrane:  2020-10-23)


113.

Pietralik Z., Murawska M., Szymańska A., Kumita J.R., Dobson C.M., Kozak M.

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Structural studies of the oligomerization process of human cystatin C variants Human cystatin C (HCC), an inhibitor of cysteine proteases, is also involved in amyloidogenic processes within the human body. In the crystal structure, as in solution, wild-type (WT) cystatin C dimerizes via a domain swapping mechanism. The same process has also been shown to be important for protein oligomerization. Aggregation of HCC results in a heterogeneous mixture of species, both oligomeric and fibrillar, with varying shapes, sizes and molecular weights.
The goal of our study was to characterize the assembly process of potentially neurotoxic oligomers of WT and variant HCC in solution. The oligomerization processes of several point mutation variants of HCC (V57N, V57P, V57D, V57G and L68V), with specific dimerization properties [3], were compared to the WT protein. Prepared oligomers were purified by size-exclusion chromatography and using TEM and AFM studies, we observed characteristic donutlike structures along with fibrils and we determined the size distribution of cystatin C oligomers obtained from the WT and variant forms. Independently, the oligomerization process was analyzed by fluorescence spectroscopy and visualized by native electrophoresis. Additionally, induced secondary structure changes were characterised by circular dichroism (CD) and infrared (FTIR) spectroscopies. Finally, the structural studies were supplemented with the modelling of the larger HCC oligomers using molecular dynamics simulations, allowing the identification of the most stable oligomeric forms of HCC to be determined.

Biophysical Journal, 110(3) S1, 26A (2016)

DOI: 10.1016/j.bpj.2015.11.205   (Pobrane:  2017-12-08)


112.

Andrzejewska W.J., Skupin M., Skrzypczak A., Kozak M.

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Structural characterization of dsDNA nanocomplexes based on ammonium gemini surfactants One of the most intensively studied groups of chemical compounds are gemini surfactants, because of their specific and attractive properties, especially the capability of stable binding of the nucleic acids, formation of spatial structures with high symmetry and relatively low cytotoxicity. They have found a broad range of applications in medicine, chemical technology, pharmaceutical industry. These complexes can be applied as nonviral transfection delivery systems in gene therapy, a novel and most promising method for the treatment of a broad range of genetic diseases. Dicationic surfactants allow introduction of a transgene without inducing natural immunological response, and release it undamaged inside the cell. However, the successful completion of this process is difficult, because of the need for many studies in order to determine all necessary parameters.
In our study we analysed nanocomplexes of cationic gemini surfactants(1,n-dodecanebis[(oxymethyl)alkyldimethylammonium]chlorides) with DNA oligomers using synchrotron radiation of small angle X-ray scattering, circular dichroism spectroscopy, agarose gel electrophoresis, polarization microscopy and transmission electron microscopy. We also analysed the cytotoxicity of our systems using MTT colorimetric assay on model cell cultures.
We observed the formation of complexes, their morphology, spatial nanostructure, conformation of nucleic acid inside them and influence on the cells. The systems studied were found to be stable and the process of their formation was reproducible.

Biophysical Journal, 110(3) S1, 403A (2016)

DOI: 10.1016/j.bpj.2015.11.2178   (Pobrane:  2020-11-05)


111.

Zalewski P., Skibiński R., Szymanowska-Powałowska D., Piotrowska H., Kozak M., Pietralik Z., Bednarski W., Cielecka-Piontek J.

The radiolytic studies of cefpirome sulfate in the solid state The possibility of applying radiation sterilization to cefpirome sulfate was investigated. The lack of changes in the chemical structure of cefpirome sulfate irradiated with a dose of 25 kGy, required to attain sterility, was confirmed by UV, FT-IR, Raman, DSC and chromatographic methods. Some radical defects with concentration no more than over a several dozen ppm were created by radiation. The antibacterial activity of cefpirome sulfate for two Gram-positive and three Gram-negative strains was changed. The radiation sterilised cefpirome sulfate was not in vitro cytotoxic against fibroblast cells.

Journal of Pharmaceutical and Biomedical Analysis, 118, 410-416 (2016)

DOI: 10.1016/j.jpba.2015.11.008


110.

Pietralik Z.. Kołodziejska Ż., Weiss M., Kozak M.

Gemini surfactants based on bis-imidazolium alkoxy derivatives as effective agents for delivery of nucleic acids: A structural and spectroscopic study The success rate of gene therapy depends on the efficient transfection of genetic material into cells. The golden mean between harmlessness and high effectiveness can be provided by synthetic lipid-like molecules that are similar to the components of biological membranes. Cationic gemini surfactants are one such moiety and because of their favourable physicochemical properties (double positive electric charge, reduced toxicity, low values of critical micelle concentration), they show great potential as delivery system components for genetic material in gene therapy. The aim of this study was to investigate the process of the complexation of cationic gemini surfactants with nucleic acids: double-stranded DNA of different sizes (21 bp, ~185 bp, ~20 kbp) and siRNA (21 bp). The tested series of dicationic surfactants consists of bis-imidazolium quaternary salts with varying lengths of hydrophobic side chains (m = 5, 6, 7, 8, 9, 11, 12, 14, 16). On the basis of the data obtained by circular dichroism spectroscopy and electrophoresis, we concluded that the studied gemini surfactants with long side chains effectively bind nucleic acids at low concentrations, which leads to the formation of stable lipoplexes. Images obtained by atomic force microscopy also confirmed the formation of vesicular structures, i.e., complexes between DNA and surfactants. The cytotoxicity of selected surfactants was also tested on HeLa cells. The surfactant toxicity significantly depends on surfactant geometry (the length of hydrophobic chain).

PloS ONE, 10(12), 1-22 (2015)

DOI: 10.1371/journal.pone.0144373


109.

Balcerzak M., Pietralik Z., Domka L., Skrzypczak A., Kozak M.

Adsorption of dimeric surfactants in lamellar silicates The adsorption of different types of cationic surfactants in lamellar silicates changes their surface character from hydrophilic to hydrophobic. This study was undertaken to obtain lamellar silicates modified by a series of novel dimeric (gemini) surfactants of different length alkyl chains and to characterise these organophilised materials. Synthetic sodium montmorillonite SOMASIF® ME 100 (M) and enriched bentonite of natural origin (Nanoclay - hydrophilic bentonite®) were organophilised with dimeric (gemini) surfactants (1,1′-(1,4-butanediyl) bis(alkoxymethyl)imidazolium dichlorides). As a result of surfactant molecule adsorption in interlamellar space, the d-spacing (d001) increased from 0.97 nm (for the anhydrous structure) to 2.04 nm. A Fourier transform infrared spectroscopy (FTIR) analysis of the modified systems reveals bands assigned to the stretching vibrations of the CH2 and CH3 groups and the scissoring vibrations of the NH group from the structure of the dimeric surfactants. Thermogravimetric (TG) and derivative thermogravimetric (DTG) studies imply a four-stage process of surfactant decomposition. Scanning electron microscopy (SEM) images provide information on the influence of dimeric surfactant intercalation into the silicate structures. Particles of the modified systems show a tendency toward the formation of irregularly shaped agglomerates.

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 364, 108-115 (2015)

DOI: 10.1016/j.nimb.2015.07.135   (Pobrane:  2017-12-08)


108.

Gospodarczyk W., Kozak M.

Interaction of two imidazolium gemini surfactants with two model proteins BSA and HEWL Gemini surfactants and their interactions with proteins have gained considerable scientific interest, especially when amyloidogenic proteins are taken into account. In this work, the influence of two selected dicationic (gemini) surfactants (3,3'-[1,8-(2,7-dioxaoctane)]bis(1-dodecylimidazolium) chloride and 3,3'-[1,12-(2,11-dioxadodecane)]bis(1-dodecylimidazolium) chloride) on two model proteins, bovine serum albumin (BSA) and hen egg white lysozyme (HEWL), have been investigated. A pronounced and sophisticated influence on BSA structure has been revealed, including a considerable change of protein radius of gyration as well as substantial alteration of its secondary structure. Radius of gyration has been found to rise significantly with addition of surfactants and to fall down for high surfactants concentration. Similarly, a remarkable fall of secondary structure (alpha-helix content) has been observed, followed by its partial retrieval for high surfactants concentration. A strong aggregation of BSA has been observed for a confined range of surfactants concentrations as well. In case of HEWL-gemini system, on the other hand, the protein-surfactant interaction was found to be weak. Molecular mechanisms explaining such behaviour of protein-surfactant systems have been proposed. The differences of properties of both studied surfactants have also been discussed.

Colloid and Polymer Science, 293(10), 2855-2866 (2015)

DOI: 10.1007/s00396-015-3671-z


107.

Pietralik Z., Kumita J.R., Dobson C.M., Kozak M.

The influence of novel gemini surfactants containing cycloalkyl side-chains on the structural phases of DNA in solution Very important to gene therapy is the delivery system of the nucleic acids (called a vector), which will enhance the efficiency of the transport of new DNA into cells whilst protecting against damage. A promising alternative to the currently used viral vectors are the systems based on amphiphilic compounds - lipoplexes. Among them, gemini surfactants, which consist of two hydrophobic chains and two cationic heads connected by a linker spacer group, appear to be promising candidates. The subject of this study involves two gemini surfactants, alkoxy derivatives of bis-imidazolium quaternary salts, differing in the length of their spacer groups and how they interact with two types of salmon sperm DNA (low and high molecular weight (MW)) or plasmid DNA (pDNA). The mixtures of gemini surfactants with nucleic acids of differing p/n ratios (positive-to-negative charge ratio) were characterised by small angle X-ray scattering (SAXS) of synchrotron radiation, dynamic light scattering (DLS), circular dichroism (CD) spectroscopy, atomic force microscopy (AFM), transmission electron microscopy (TEM) and gel electrophoresis techniques. This analysis allows for the selection of the most suitable and promising candidates for non-viral vectors in gene therapy, determination of the conditions needed to form stable complexes, identification of conformational changes in the DNA molecules upon interactions with gemini surfactants and in some cases, determination of the structures formed in these lipoplexes.
(C) 2015 Elsevier B.V. All rights reserved.

Colloids and Surfaces B: Biointerfaces, 131, 83-92 (2015)

DOI: 10.1016/j.colsurfb.2015.04.042   (Pobrane:  2015-07-24)


106.

Wolak J., Skupin M., Pietralik Z., Andrzejewska W., Kozak M.

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Studies of zwitterionic lipoplexes - nanosystem based on phospholipids and surfactants as innovative delivery systems for gene therapy The gene therapy is the one of the most promising method of treatment in contemporary medicine. This way of therapy is very useful in the treatment a dozen of incurable or fatal diseases. This method of treatment is leaned on implement a gene into patient's cells with the use of dedicated delivery systems (vectors). The main problem of gene therapy is to find the best vector which will be effective and will be not toxic for human cells. A good approach seems to be use of non-viral vectors like delivery system based on lipid-surfactant mixtures.

The aim of this study was to examine the possible application of selected amphoteric surfactants (zwitterionic alkyl derivatives of sulfobetaine) as complexing agents (with and without helper lipid) for nucleic acids (siRNA, low and high-molecular weight DNA).

The studies of DNA conformation in selected DNA - zwitterionic surfactant lipoplexes were performed using the circular dichroism (CD) spectroscopy. CD spectra were recorded in the spectral range 350 - 200 nm by using J-815 spectrometer (Jasco). The results obtained indicate that the DNA maintains the B-form for wide range of surfactant concentrations in the solution. The structure and organization of lipoplexes was also independently analyzed by the Fourier transform infrared spectroscopy. The absorption spectra for lipoplexes were collected by using FTIR spectrometer BRUKER Tensor 27 in the temperature range 2-40°C. The phase transitions in examined systems were studied by using the differential scanning calorimetry (DSC). Ability of creating of stable complexes in DNA-surfactant systems studied was confirmed using electrophoresis on agarose gel. For all formed stable lipoplexes the complete reduction of electrophoretic mobility was observed. Finally the transfection efficiency of selected systems were also tested on HeLa cells.

Biophysical Journal, 108(2) S1, 545A (2015)

DOI: 10.1016/j.bpj.2014.11.2989   (Pobrane:  2020-11-05)


105.

Kozak M., Pietralik Z., Szymańska A., Taube M.

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Spectroscopic and SAXS studies of human cystatin c mutants - early stages of amyloid formation process Human cystatin C (HCC) is a cysteine protease inhibitor. This protein in pathological conditions, forms dimers via a “domain swapping” mechanism. HCC is also associated with two types of amyloid deposition diseases - hereditary amyloid angiopathy (related to the Leu68Gln mutation) and wild-type cystatin C co-precipitation.

The aim of our studies was the characterisation of the self-assembling properties of native and mutated (at positions 57 or 68) forms of human cystatin C in solution. The structure, overall conformation and secondary structure changes in solution were studied by Fourier transformed infrared spectroscopy (FTIR), circular dichroism spectroscopy (CD), dynamic light scattering (DLS) and time resolved small angle scattering of synchrotron radiation (TR-SAXS).

SAXS data for native and mutated HCC were subjected to analysis by using SVD and MCR-ALS methods as well as the low resolution structure determination. Besides the monomeric forms of human cystatin C, also dimers and higher oligomers were formed even after short (50-ms) exposure on synchrotron radiation. In addition we observed for first time, formation of domain swapped dimers of human cystatin C induced by irradiation. The spectroscopic studies confirmed conformational changes.

Authors acknowledge also the partial support by HARMONIA3 grant (Project No. 2012/06/M/ST4/00036) from National Science Centre (Poland).

Biophysical Journal, 108(2) S1, 516A (2015)

DOI: 10.1016/j.bpj.2014.11.2827   (Pobrane:  2020-11-05)


104.

Andrzejewska W.J., Skupin M., Murawska M., Skrzypczak A., Kozak M.

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The study of complexation process between cationic gemini surfactants and dna using structural and spectroscopic methods Dicationic (gemini) surfactants are intensively studied group of chemical compounds, because of the broad range of applications in medicine, chemical technology or pharmaceutical industry. In solution they can form with nucleic acids the complex structures (lipoplexes), which can be used as drug delivery systems in nonviral transfection. Lipoplexes in gene therapy offer efficient introduction of a therapeutic material to the living cells. Gemini surfactants also allow introduction of a transgene without inducing natural immunological response and release it inside the cell. In our study, we analyzed the process of complexation of cationic gemini surfactants (3.3'- [1,6- (2,n-dioxyalcane)] bis(1-dodecyloxyimidazolium dichlorides)) with DNA, using small angle X-ray scattering, circular dichroism spectroscopy and gel electrophoresis. Surfactants which have been used had of variable length of the spacer group. We observed the formation of stable complexes in these systems and the process of complex formation was reproducible, efficient and immediate.

Biophysical Journal, 108(2) S1, 392A (2015)

DOI: 10.1016/j.bpj.2014.11.2152   (Pobrane:  2020-11-05)


103.

Skupin M., Wolak J., Kozak M.

Abstrakt lub materiały konferencyjne, albo abstrakt publikacji
z dodatkowymi numerami DOI

Nanosystem based on phospholipids and surfactants as innovative delivery system for gene therapy Amphiphilic dicationic surfactants, known as gemini surfactants, are currently studied for gene delivery purposes. The biggest advantages of these systems are that they are non-immunogenic and generally have low toxicity. One of the most important advantages of these systems is improved transfection efficiency. The aim of this study was to determine the possibility to use amphoteric surfactants (zwitterionic derivatives of sulfobetaine with carbohydrate moiety) and sulfobetaine/gemini surfactant mixtures as complexing agents for nucleic acids, with potential applications for gene delivery to reduce the toxicity and improved transfection. Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC) were used to a7nalyze influence of surfactants on the phase behaviour of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) bilayers with the presence of different DNA forms (small DNA oligomers, cDNA, low and high-molecular mass DNA). The influence of different concentrations of sulfobetaine and sulfobetaine/gemini surfactant mixtures with the presence of DNA on creating stable complexes was investigated using circular dichroism (CD) spectroscopy and electrophoresis. A series of measurements of toxicity and transfection of these lipoplexes were performed in HeLa cells. These compounds appear to be excellent for creating complexes with DNA. Thanks to their construction this DNA carrier molecules might be able to deliver genes to the cells of almost any DNA mo7lecular size, unattainable when using viral gene delivery systems.

Biophysical Journal, 108(2) S1, 245A (2015)

DOI: 10.1016/j.bpj.2014.11.1357   (Pobrane:  2020-08-10)


102.

Andrzejewska W., Pietralik Z., Taube M., Skrzypczak A., Kozak M.

Structural and spectroscopic studies on the formation of lipoplexes between DNA and cationic gemini surfactants The process of complex formation between cationic gemini surfactants, 3,3'-[α,ω-(dioxaalkane)]bis(1-dodecylimidazolium) dichloride, with deoxyribonucleic acid (DNA) was studied. The study was performed for ten surfactants having spacer groups of different lengths used in 6 concentrations (5 mM, 2 mM, 1 mM, 0.5 mM, 0.2 mM, 0.1 mM) and a 6.5 μM DNA solution. The complex formation was verified by circular dichroism spectroscopy and gel electrophoresis. The complexes were found to be stable and the process of complex formation was reproducible, efficient and immediate.

Polimery/Polymers, 59(7-8), 569-574 (2014)

DOI: 10.14314/polimery.2014.569
WWW: http://www.ichp.pl/spektroskopowe-badania-procesu-formowania-lipopleksow   (Pobrane:  2021-01-10)


101.

Gospodarczyk W., Szutkowski K., Kozak M.

Interaction of Bovine Serum Albumin (BSA) with novel gemini surfactants studied by synchrotron radiation scattering (SR-SAXS), circular dichroism (CD) and nuclear magnetic resonance (NMR) The interaction of three dicationic (gemini) surfactants-3,3'-[1,6-(2,5-dioxahexane)]bis(1-dodecylimidazolium) chloride (oxyC2), 3,3'-[1,16-(2,15-dioxahexadecane)]bis(1-dodecylimidazolium) chloride (oxyC12), and 1,4-bis(butane)imidazole-1-yl-3-dodecylimidazolium chloride (C4)-with bovine serum albumin (BSA) has been studied by the use of small-angle X-ray scattering (SAXS), circular dichroism (CD), and H-1 nuclear magnetic resonance diffusometry. The results of CD studies show that the conformation of BSA was changed dramatically in the presence of all studied surfactants. The greater decrease (from 56 to 24%) in the alpha-helical structure of BSA was observed for oxyC2 surfactant. The radii of gyration estimated from SAXS data varied between 3 and 26 nm for the BSA/oxyC2 and BSA/oxyC12 systems. The hydrodynamic radius of the BSA/surfactant system estimated from NMR diffusometry varies between 5 and 11 nm for BSA/oxyC2 and 5 and 8 nm for BSA/oxyC12.

Journal of Physical Chemistry B, 118(29), 8652-8661 (2014)

DOI: 10.1021/jp5047485


100.

Taube M., Pieńkowska J.R., Jarmołowski A., Kozak M.

Low-resolution structure of the full-length barley (Hordeum Vulgare) SGT1 protein in solution, obtained using small-angle X-ray scattering SGT1 is an evolutionarily conserved eukaryotic protein involved in many important cellular processes. In plants, SGT1 is involved in resistance to disease. In a low ionic strength environment, the SGT1 protein tends to form dimers. The protein consists of three structurally independent domains (the tetratricopeptide repeats domain (TPR), the CHORD-and SGT1-containing domain (CS), and the SGT1-specific domain (SGS)), and two less conserved variable regions (VR1 and VR2). In the present study, we provide the low-resolution structure of the barley (Hordeum vulgare) SGT1 protein in solution and its dimer/monomer equilibrium using small-angle scattering of synchrotron radiation, ab-initio modeling and circular dichroism spectroscopy. The multivariate curve resolution least-square method (MCR-ALS) was applied to separate the scattering data of the monomeric and dimeric species from a complex mixture. The models of the barley SGT1 dimer and monomer were formulated using rigid body modeling with ab-initio structure prediction. Both oligomeric forms of barley SGT1 have elongated shapes with unfolded inter-domain regions. Circular dichroism spectroscopy confirmed that the barley SGT1 protein had a modular architecture, with an alpha-helical TPR domain, a beta-sheet sandwich CS domain, and a disordered SGS domain separated by VR1 and VR2 regions. Using molecular docking and ab-initio protein structure prediction, a model of dimerization of the TPR domains was proposed.

PLoS ONE, 9(4), e93313 (2014)

DOI: 10.1371/journal.pone.0093313


99.

Borek D., Kozak M., Pei J., Jaskólski M.

Crystal structure of active site mutant of antileukemic l-asparaginase reveals conserved zinc-binding site The periplasmic enzyme l-asparaginase type II from Escherichia coli (EcAII) converts l-asparagine to l-aspartate and ammonia. EcAII is an important drug in the treatment of childhood acute lymphoblastic leukemia, the most common malignancy in children. Leukemic blast cells lack the ability to synthesize l-asparagine and rely on other sources of l-asparagine for protein synthesis. EcAII injections deplete extracellular levels of l-asparagine, disrupting protein synthesis and inducing apoptosis in the malignant cells. The detailed mechanism of l-asparaginase catalytic action, the molecular mechanisms of its anticancer activity and the side effects associated with the treatment, including resistance to therapy, are not fully understood despite over 40 years of research. Here, we present X-ray structures of EcAII with an active site mutation, D90E, in three crystal forms. The region of the mutation is well ordered, allowing precise functional analysis of the consequences of the replacement of Asp90. In all three structures, the mutant protein exhibits an open conformation of the active site. In one of the structures, a zinc cation has been detected. The zinc cation is coordinated in a region of the protein that is implicated in the immunological response to EcAII treatment. A combined sequence-structure analysis of bacterial-type l-asparaginases reveals that the metal coordination may play a role in the response to asparaginase treatment. The observation of a zinc-binding site in antileukemic l-asparaginases provides new insight, with consequences for acute lymphoblastic leukemia therapy.

The FEBS Journal, 281(18), 4097-4111 (2014)

DOI: 10.1111/febs.12906


98.

Buszewski B., Olszowy P., Pikus S., Kozak M.

Electropolymerized nanoporous polymeric SPME coatings: preparation and characterization by small angle X-ray scattering and scanning electron microscopy Polymeric polypyrrole and polythiophene solid phase microextraction (SPME) coatings were prepared using electropolymerization with a linear sweep voltammetry technique. Physicochemical properties were measured using different methods, in particular small angle X-ray scattering and scanning electron microscopy. By using innovative approaches for pore size measurement, we were able to calculate a maximum of the pore size range from 80 to 90 nm. Additionally, film thicknesses measured from 90 to 150 mu m. Using scanning electron microscopy, we describe the characteristics of polymer growth on the support surface.

Monatshefte fur Chemie, 145(3), 527-531 (2014)

DOI: 10.1007/s00706-013-1115-3


97.

Murawska M., Wiatr M., Nowakowski P., Szutkowski K., Skrzypczak A., Kozak M.

The structure and morphology of gold nanoparticles produced in cationic gemini surfactant systems Potential applications of gold nanoparticles (GNP) are strictly connected with their size and shape. The influence of different dicationic (gemini) surfactants, alkyloxymethylimidazolium derivatives derivatives, on the structure and morphology of GNP was studied. The synthesis of nanoparticles was performed in the presence of various gemini surfactants-dodecyloxymethylimidazolium nitrate (IMI_NO3_C4_C12), propionate (IMI_PROP_C4_C12) and 3,3'-[1,9-(2,8-dioxanonane)]bis-(1-nonyloxymethylimidazolium) chloride (IMI_Cl_oxyC7_C9), used as stabilizers and templates for obtaining different size and shape of gold nanoparticles. The samples obtained were examined using transmission electron microscopy (TEM), small angle scattering of synchrotron radiation (SAXS), UV-vis spectroscopy and NMR PFG spectroscopy. For the obtained solutions of nanoparticles the plasmon resonance was observed at the wavelengths corresponding to the presence of gold nanoparticles of sizes ranging from 5-100 nm, with a significant shift towards higher wavelength for the samples prepared with addition of dicationic surfactants. TEM images evidence the presence of gold nanoparticles with tetrahedral and spherical morphology in solutions prepared with the surfactants IMI_PROP_C4_C12, IMI_NO3_C4_C12, and those of spherical morphology, but strongly aggregated, in the solution with the cationic surfactant IMI_Cl_oxyC7_C9.
(C) 2013 Elsevier Ltd. All rights reserved.

Radiation Physics and Chemistry, 93, 160-167 (2013)

DOI: 10.1016/j.radphyschem.2013.05.024


96.

Kwiatek W.M., Kozak M., Paszkowicz W.

SOLARIS: Waiting for the first light Proceedings of XI International School and Symposium on Synchrotron Radiation in Natural Science 2012, Krakow, Poland

Radiation Physics and Chemistry, 93, 1-3 (2013)

DOI: 10.1016/j.radphyschem.2013.08.003


95.

Wypych A., Szpotkowski K., Jurga S., Domka L., Kozak M.

Interactions of a cationic surfactant - (benzyloxymethyl) dodecyldimethylammonium chloride with model biomembrane systems Phospholipids are the main components of biological membranes. The aim of the present study was to determine the influence of a cationic surfactant on phospholipid structure and dynamics. Fourier transform infrared (FTIR) and dielectric relaxation (DRS) spectroscopies as well as small-angle Xray scattering (SAXS) with synchrotron radiation have been used to analyse the structure of fully hydrated 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) in the presence of a quaternary ammonium surfactant: (benzyloxymethyl) dodecyldimethylammoniumchloride (BzMDDAC). The presence of the surfactant caused changes in the temperature of the DMPC phase transition, as revealed using FTIR and DRS measurements. This change results from the disappearance of the multilamellar phase of DMPC and the formation of the unilamellar (most likely bicellar) phase, as indicated by the SAXS results.
(C) 2013 Elsevier B.V. All rights reserved.

Colloids and Surfaces B: Biointerfaces, 108, 212-218 (2013)

DOI: 10.1016/j.colsurfb.2013.03.010   (Pobrane:  2021-01-20)


94.

Östner G., Lindström V., Christensen H.P., Kozak M., Abrahamson M., Grubb A.

Stabilization, characterization and selective removal of Cystatin C amyloid oligomers The pathophysiological process in amyloid disorders usually involves the transformation of a functional monomeric protein via potentially toxic oligomers into amyloid fibrils. The structure and properties of the intermediary oligomers have been difficult to study due to their instability and dynamic equilibrium with smaller and larger species. In hereditary cystatin C amyloid angiopathy, a cystatin C variant is deposited in arterial walls and cause brain hemorrhage in young adults. In the present investigation, we use redox experiments of monomeric cystatin C, stabilized against domain swapping by an intramolecular disulfide bond, to generate stable oligomers (dimers, trimers, tetramers, decamers, and high molecular weight oligomers). These oligomers were characterized concerning size by gel filtration, polyacrylamide gel electrophoresis, and mass spectrometry, shape by electron and atomic force microscopy, and, function by assays of their capacity to inhibit proteases. The results showed the oligomers to be highly ordered, domain-swapped assemblies of cystatin C and that the oligomers could not build larger oligomers, or fibrils, without domain swapping. The stabilized oligomers were used to induce antibody formation in rabbits. After immunosorption, using immobilized monomeric cystatin C, and elution from columns with immobilized cystatin C oligomers, oligomer-specific antibodies were obtained. These could be used to selectively remove cystatin C dimers from biological fluids containing both dimers and monomers.

Journal of Biological Chemistry, 288(23), 16438-16450 (2013)

DOI: 10.1074/jbc.M113.469593


93.

Pietralik Z., Krzysztoń R., Kida W., Andrzejewska W. and Kozak M.

Structure and conformational dynamics of DMPC/dicationic surfactant and DMPC/dicationic surfactant/DNA systems Amphiphilic dicationic surfactants, known as gemini surfactants, are currently studied for gene delivery purposes. The gemini surfactant molecule is composed of two hydrophilic "head" groups attached to hydrophobic chains and connected via molecular linker between them. The influence of different concentrations of 1,5-bis (1-imidazolilo-3-decyloxymethyl) pentane chloride (gemini surfactant) on the thermotropic phase behaviour of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) bilayers with and without the presence of DNA was investigated using Fourier transformed infrared (FTIR) and circular dichroism (CD) spectroscopies, small angle scattering of synchrotron radiation and differential scanning calorimetry. With increasing concentration of surfactant in DMPC/DNA systems, a disappearance of pretransition and a decrease in the main phase transition enthalpy and temperature were observed. The increasing intensity of diffraction peaks as a function of surfactant concentration also clearly shows the ability of the surfactant to promote the organisation of lipid bilayers in the multilayer lamellar phase.

International Journal of Molecular Sciences, 14(4), 7642-7659 (2013)

DOI: 10.3390/ijms14047642


92.

Marciniec B., Stawny M., Olszewski K., Kozak M., Naskrent M.

Analytical study on irradiated methylxanthine derivatives The effect of ionising radiation on the physico-chemical properties of three derivatives of xanthine: caffeine, theophylline and theobromine, has been studied. The above-drugs in the solid phase have been irradiated with E-beam of the energy 9.96 MeV with the doses varied from 25 to 400 kGy. The effects of the irradiation have been examined by differential scanning calorimetry (DSC), electron paramagnetic resonance (EPR) and high-performance liquid chromatography (HPLC). The results have shown that the methylxanthine derivatives studied are resistant to ionising irradiation in the doses usually used for sterilisation (< 50 kGy), which means that they are relatively radiochemically stable and can be sterilised by irradiation.

Journal of Thermal Analysis and Calorimetry, 111(3), 2165-2170 (2013)

DOI: 10.1007/s10973-012-2774-8


91.

Zienkiewicz-Strzałka M., Pasieczna-Patkowska S., Kozak M., Pikus S.

Silver nanoparticles incorporated onto ordered mesoporous silica from Tollen's reagent Noble metal nanostructures supported on mesoporous silica are bridge between traditional silica adsorbents and modern catalysts. In this work the Ag/SBA-15 mesoporous materials were synthesized and characterized. Various forms of nanosilver supported on ordered mesoporous template have been successfully obtained via proposed procedures. In all synthesized materials, Tollen's reagent (diammine silver complex [Ag(NH3)(2)](+)) was used as a silver source. Silver nanoparticles were prepared by reduction of ammoniacal silver complex by formaldehyde in the solution of stabilizer. After reduction, Ag nanoparticles could be deposited on SBA-15, or added during traditional synthesis of SBA-15 giving silver or silver chloride nanoparticles in the combination with porous silica. Silver nanostructures as nanoparticles or nanowires were also embedded onto the SBA-15 by incipient wetness impregnation of silver ions. Absorbed silver ions were next reduced under hydrogen at high temperature. There are many advantages of utilized ammoniacal silver complex as a silver source. Proposed method is capable to synthesis of various metal nanostructures with controlled composition and morphology. The silver ammonia complex is composed of two ions surrounding and protecting the central silver ion, so it is possible to obtain very small nanoparticles using simple approach without any functionalization of external and internal surface of SBA-15. This approach allows obtaining greatly small silver nanoparticles on SBA-15 (4 nm) or nanowires depending on the metal loading amount. Moreover, the colloidal silver solution prepared from Tollen's reagent, in the presence of triblock copolymer, remains stable for a long time. Reduction of Tollen's reagent to silver colloidal solution seems to be efficient, fast and interesting approach for the preparation of supported silver nanostructures Obtained samples were characterized by powder X-ray diffraction, small angle X-ray scattering (SAXS), UV-vis spectroscopy, transmission electron microscopy (TEM), nitrogen adsorption-desorption isotherms and photoacoustic spectroscopy (PAS).
(C) 2012 Elsevier B.V. All rights reserved.

Applied Surface Science, 266, 337-343 (2013)

DOI: 10.1016/j.apsusc.2012.12.021


90.

Saini R., Szpotkowski K., Kozak M., Jaskolski M., Davis S.J.

Biochemical and structural studies of plant circadian clock proteins Circadian clocks are biochemical oscillatory mechanisms that co-ordinate with a 24h period predicting the daily diurnal changes in the environment to regulate various metabolic, developmental and physiological processes in the organisms. The plant circadian clock represents a network of interconnected multiple feedback loops at the core of which lie two Myb-like transcription factors, Circadian Clock Associated 1 (CCA1) and Late Elongated Hypocotyl (LHY), that express in the morning, and an evening expressing Timing of CAB Expression 1 (TOC1). Other components important for the clock are Early Flowering 3 and 4 (ELF3 and ELF4) and Lux Arrhythmo (LUX) that accumulate in the evening (Harmer, 2009). Previous studies have shown these to be part of an evening complex that is important for the regulation of the core oscillator (Nusinow et al., 2011; Herrero et al., 2012). Loss-of-function mutation studies of these components demonstrate arrhythmia under constant conditions of light (LL) and in darkness (DD) (Kolmos et al., 2009; Thines and Harmon, 2010). Recently, it has been shown (both in vivo and in vitro) that ELF3 and ELF4 interact physically with each other to perform their regulatory function (Herrero et al., 2012). Here, using various in silico and experimental approaches, we have tried to understand the structural aspects of these two evening expressing plant clock proteins (ELF3 and 4). Due to the instability of the ELF4 and ELF3 proteins, crystallization and Small Angle X-ray Scattering (SAXS) measurements were carried out for recombinant variants tagged with fusion (MBP or NusA) proteins.

Biotechnologia, 94(1), 40-41 (2013)

DOI: 10.5114/bta.2013.46435   (Pobrane:  2020-10-23)


89.

Makrocka-Rydzyk M., Wegner K., Szutkowski K., Kozak M., Jurga S., Gao H.

Morphology and NMR self-diffusion in PBA/PEO miktoarm star copolymers Morphology and NMR self-diffusion of two miktoarm star copolymers differing in fraction of poly(n-butyl acrylate) and poly(ethylene oxide) (PBA and PEO) arms were under investigation. Structural characteristics of copolymers was obtained on the basis of Small Angle X-Ray Scattering (SAXS) investigations. The phase separated nanoscale morphology of the miktoarm star copolymer with a high fraction of PEO arms was confirmed by Scanning Probe Microscopy (SPM) studies. The modified Avrami approach was used to obtain the information on the non-isothermal crystallization kinetics of the studied systems. It was observed that the crystallization in the system with a higher content of PBA, occurring at higher undercooling, was characterized by a higher crystallization rate. It was also found that increase in PBA arms fraction leads to the reduction in the size of PEO domains. The activation energy of the crystallization process, estimated with Kissinger's method, is lower for miktoarm star copolymer with higher PBA content, which results from facilitation of the transport of PEO chains in the direction of the growing crystal due to the presence of mobile PBA arms. The self-diffusion studies of miktoarm star copolymers melts, carried out with the Pulsed-Gradient STimulated-Echo (PGSTE) Nuclear Magnetic Resonance (NMR) technique, reveals the existence of at least two types of diffusion mechanisms in these systems.

Zeitschrift für Physikalische Chemie, 226, 1271-1292 (2012)

DOI: 10.1524/zpch.2012.0300   (Pobrane:  2020-10-23)


88.

Marciniec B., Dettlaff K., Naskrent M. Pietralik Z., Kozak M.

DSC and spectroscopic studies of disulfiram radiostability in the solid state The effect of ionising radiation on the physicochemical properties of disulfiram (Antabuse, Esperal, bis-diethylthiocarbamoil disulphide) has been studied by DSC, FTIR, EPR, MS, TLC and HPLC. Sterilisation was carried out in the solid state, at room temperature and normal air humidity using the electron beam of 9.96 Mev from accelerator. All the measurements were made simultaneously for the irradiated and nonirradiated substance. It has been found that the drug studied in solid phase when subjected to an electron beam corresponding to the irradiation in the doses 10-100 kGy shows the presence of free radicals (EPR), and a change in colour from white to pale green-grey that disappears after solution in water or methanol. After the irradiation with the dose of 100 kGy, its melting point and enthalpy slightly decreased. Also the content of the active substance decreases (HPLC -1.5%, UV -3.6%, iodometric titration method -2.7%) and trace amounts of the radiolysis products appear (HPLC). The substance irradiated with the doses 10-50 kGy does not show changes in the melting point, in the content and presence of the radiolysis products. The EPR results have shown that free radicals disappear after about a year and the discolouring disappears with them. The results of this study have shown that disulfiram can be subjected to sterilisation by irradiation with no deterioration of its physico-chemical properties, but a long time of storage needed to remove free radicals and discolouration questions the economic justification for this type of sterilisation.

Journal of Thermal Analysis and Calorimetry, 108(1), 33-40 (2012)

DOI: 10.1007/s10973-011-1810-4   (Pobrane:  2012-10-16)


87.

Kida W., Kozak M.

Structural changes of DPPC bilayers induced by gemini surfactant The phospholipid-gemini surfactant systems are promising agents for construction of lipoplexes for DNA delivery systems in gene therapy. In this work the influence of a gemini surfactant - 1,1'-(1,6-hexan)bis3-octyloxymethylimidazolium di-chloride) (IMI_C1_C6_C8) on the structure and phase behaviour of aqueous suspensions of the fully hydrated phospholipid - 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) were characterised using small angle scattering of synchrotron radiation (SAXS), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). The surfactant studied caused a destabilisation of the lamellar phase typical of DPPC. Addition of the surfactant also shifted to lower temperatures and extended the range of the main phase transition

Acta Physica Polonica A, 121(4), 893-898 (2012)

DOI: 10.12693/APhysPolA.121.893
WWW: http://przyrbwn.icm.edu.pl/APP/PDF/121/a121z4p207.pdf   (Pobrane:  2021-01-10)


86.

Murawska M., Skrzypczak A., Kozak M.

Structure and morphology of gold nanoparticles in solution studied by TEM, SAXS and UV-VIS Gold nanoparticles have a great number of applications, among others in material sciences, biology and medicine. A method for the synthesis of gold nanoparticles in solution with the use of gemini surfactant was proposed and the nanoparticles obtained were subjected to thorough characterisation. The method proposed is a modification of the Turkevich method, based on reduction of tetrachloroauric acid in the presence of trisodium citrate and a dicationic (gemini) surfactant - 1,1'-(1,4-butan)bis(3-dodecyloxymethylimidazolium) di-propionate. Morphology and size distribution of gold nanoparticles obtained were examined by the transmission electron microscopy (TEM), UV-Vis spectroscopy and small angle scattering of synchrotron radiation (SAXS). The plasmon resonance of the nanoparticles obtained was observed in the wavelength range corresponding to the presence of gold nanoparticles with sizes ranging from 5 to 100 nm. TEM images confirmed that the spherical shape of nanoparticles was dominated in reference solutions prepared of sodium citrate and tetrachloroauric acid. In the solutions prepared with addition of gemini surfactant, the gold nanoparticles of triangular morphology were observed.

Acta Physica Polonica A, 121(4), 888-892 (2012)

DOI: 10.12693/APhysPolA.121.888
WWW: http://przyrbwn.icm.edu.pl/APP/PDF/121/a121z4p206.pdf   (Pobrane:  2021-01-10)


85.

Kozak M., Rypniewski W., Jaskólski M.

Koncepcja budowy linii pomiarowej MX/SAXS/XRD w NCPS SOLARIS In December 2011 the construction of the rst Polish synchrotron | The National Syn-chrotron Radiation Centre SOLARIS | was initiated in Krakow. The energy parameters of SOLARIS (1:5 GeV) allow planning of a beam line utilising the synchrotron radiation (hard X-rays range), that can be used in biocrystallography and material science. The planned beam line has three end-stations | for biocrystallography (MX), small-angle X-ray scattering (SAXS) and di raction of synchrotron radiation on polycrystalline materials (XRD).

Synchrotron Radiation in Natural Science, 11(1-2), 5-9 (2012)


84.

Makrocka-Rydzyk M., Wypych A., Szpotkowski K., Kozak M., Jurga S., Gao H.F., Cho H.Y., Matyjaszewski K.

Structural studies of poly(butyl acrylate) - poly(ethylene oxide) miktoarm star polymers Structural behavior of miktoarm star polymers comprising poly(butyl acrylate) (PBA) and poly(ethylene oxide) (PEO) arms was studied by means of Differential Scanning Calorimetry (DSC), Wide Angle X-Ray Scattering (WAXS), Polarized Optical Microscopy (POM) and Fourier Transform Infrared Spectroscopy (FTIR) methods. The aim of this study was to correlate changes in the composition of the arms of the PBA/PEO miktoarm star polymers with their structures. As a consequence of increasing PBA content, the decrease in crystallinity of the studied PBA/PEO heteroarm star copolymers was observed. Regardless of the copolymer composition, fraction of oxyethylene units in the crystalline PEO phase was similar in all investigated systems. The POM images showed spherulitic morphology of the materials having low PBA content, while an increase in PBA arms fraction leads to the formation of less ordered structures. The analysis of FTIR vibrational spectrum indicates helical conformation of PEO chains in the crystalline phase. Isothermal crystallization studies carried out using the FTIR technique suggest the existence of isolated domains in the nanoscopic scale of investigated materials.

Polymer, 52(24), 5513-5520 (2011)

DOI: 10.1016/j.polymer.2011.09.020   (Pobrane:  2020-10-23)


83.

Kozak M., Paszkowicz W., Piszora P.

Synchrotron radiation studies in Poland The 10th International School and Symposium on Synchrotron Radiation in Natural Science (ISSRNS)

Radiation Physics and Chemistry, 80(10), 999-1000 (2011)

DOI: 10.1016/j.radphyschem.2011.06.003


82.

Pietralik Z., Taube M., Kozak A., Wieczorek D., Zielinski R., Kozak M.

MAX-Lab Activity Report 2010, , 286-288 (2011)

WWW: https://www.maxlab.lu.se/sites/default/files/MAX_AR2010_web_0.pdf   (Pobrane:  2011-10-18)


81.

Kozak M., Lewandowska A., Ołdziej S., Rodziewicz-Motowidło S., Liwo A.

Combination of SAXS and NMR techniques as a tool for the determination of peptide structure in solution: conformation of the 28-43 fragment of the B3 domain of immunoglobulin binding protein G from Streptococcus The biological activity of peptides is largely determined by their spatial structure in solution. Because of flexibility of these molecules, the NMR technique, commonly used to determine the solution structures, usually provides only the information of the local geometry of peptide chains. On the other hand, small-angle X-ray scattering (SAXS) gives interatomic distance distribution in the molecule, thereby defining the shape of a molecule. In this work we carried out a SAXS study of the 28-43 sequence fragment of the B3 domain of immunoglobulin binding protein G from Streptococcus, IG(28-43). We fitted the conformational ensembles obtained in our previous work by using the NMR-restrained molecular dynamics simulations to the distance distribution obtained from SAXS measurements. Only two clusters of conformations with shape bent in the middle out of 11, consistent with NMR data had nonzero statistical weights. Thus, SAXS and NMR provide complementary structural information and appear to be an excellent tool for peptide structure determination when combined.

Journal of Physical Chemistry Letters, 1(20), 3128-3131 (2010)

DOI: 10.1021/jz101178t   (Pobrane:  2020-10-23)


80.

Barczak M., Dąbrowski A., Pikus S., Ryczkowski J., Borowski P., Kozak M.

Studies of the structure and chemistry of SBA-15 organosilicas functionalized with amine, thiol, vinyl and phenyl groups SBA-15 organosilicas containing amine, thiol, vinyl and phenyl pendant groups were synthesized by co-condensation of tetraethoxysilane and appropriate alkoxysilanes in the presence of Pluronic P123 surfactant. The obtained materials have usually well-developed porous structure-values of specific surface area are in the range 820-950 m(2)/g. Sizes of the ordered mesopores are in the range 7.5-9.1 nm while the interconnecting pores are 2.3-3.1 nm in size. It was establish that size of the mesopores strongly depends even on small amounts of co-monomers co-condensing with tetraethoxysilane. Several instrumental techniques such as infrared spectroscopy, X-ray diffraction, nitrogen sorption measurements, elemental analysis, transmission electron microscopy. FT-IR photoacoustic spectroscopy (FT-IR/PAS) was used to determine chemical composition of the final materials and to monitor the efficiency of the template removal.

Adsorption - Journal of the International Adsorption Society, 16(4-5), 457-463 (2010)

DOI: 10.1007/s10450-010-9250-1


79.

Marciniec B., Kozak M., Naskrent M., Hofman M., Dettlaff K., Stawny M.

DSC and EPR analysis of some radiation sterilized alkaloids The effect of ionising radiation on the physico-chemical properties of salts of three alkaloids has been studied: codeine phosphate (COD), papaverine hydrochloride (PAP) and pilocarpine hydrochloride (PIL). These compounds in the solid state were irradiated with an e-beam of the energy of 9.96 MeV to achieve doses ranging from 25 to 400 kGy, and then they were subjected to organoleptic analysis, thermal analysis (differential scanning calorimetry, DSC), electron resonance (EPR) spectroscopy, scanning electron microscopy observations and X-ray diffraction study. The most informative were the results provided by the EPR and DSC methods. The EPR spectra revealed the presence of long-lived radicals whose concentration was directly proportional to the dose of irradiation for all the compounds studied. (PIL 2.14 x 10(16) spin/g, COD 6.85 x 10(15) spin/g, PAP 2.50 x 10(14) spin/g-for the dose of 100 kGy). The DSC results revealed a decrease in the melting point by 5.9 A degrees C for COD and by 0.8 A degrees C for PIL after irradiation with 200 kGy, which is indicative of products of radiolysis, of which at least one is non-white, and changes the colour of the compounds. PAP, for which no decrease in the melting point and no colour change was observed and for which the concentration of free radicals was the lowest, was found to be most stable from among the compounds studied. It will probably be suitable for radiation sterilisation. The other two compounds COD and PIL show much lower radiochemical stability and should be subjected to more detailed examination to establish the mechanism of radiolysis and the possibility of radiation sterilisation. Our results have confirmed the earlier reports on high radiochemical stability of PAP, but do not confirm the resistance to ionising radiation of COD and PIL.

Journal of Thermal Analysis and Calorimetry, 102(1), 261-267 (2010)

DOI: 10.1007/s10973-009-0445-1


78.

Pikus S., Celer E. B., Jaroniec M., Solovyov L. A., Kozak M.

Studies of intrawall porosity in the hexagonally ordered mesostructures of SBA-15 by small angle X-ray scattering and nitrogen adsorption Ordered mesoporous silicas (OMSs) such as SBA-15 (p6mm symmetry group) synthesized in the presence of block copolymers containing poly(ethylene oxide) blocks possess irregular complementary pores in the walls of ordered mesopores. The X-ray scattering caused by this complementary porosity contributes to the background of the SAXS patterns. This work shows the possibility of using the SAXS data for the study of intrawall channels interconnecting ordered cylinders in SBA-15. The proposed SAXS analysis was tested by using a series of SBA-15 samples obtained at different temperatures of hydrothermal treatment (from 60 to 180 degrees C). The structural modelling of the SAXS patterns recorded for a series of SBA-15 samples was performed by using the continuous density function (CDF) technique in combination with the derivative difference minimization (DDM) method of full-profile refinement. This method is well suited for extraction of the background curves from the SAXS patterns. The resulting smooth background curves were analyzed by the well-known method in the SAXS theory used for evaluation of heterogeneity distributions, which in this case characterize the intrawall complementary porosity. A relatively good agreement has been observed between the data obtained by SAXS and nitrogen adsorption analysis. The SAXS analysis is sufficiently sensitive for examination of heterogeneous microporosity in SBA-15 materials. The average diameter of intrawall pores for the SBA-15 sample obtained at 60 degrees C was only about 1.4 nm. However, this diameter increased with the increasing temperature of hydrothermal treatment; namely, it was 1.5, 1.8, 2.6, 2.6, 3.5 and 5.2 nm for the SBA-15 samples hydrothermally treated at 80, 100, 120, 140, 160 and 180 degrees C, respectively.
(C) 2009 Elsevier B.V. All rights reserved.

Applied Surface Science, 256(17), 5311-5315 (2010)

DOI: 10.1016/j.apsusc.2009.12.068


77.

Kozak M., Wypych A., Szpotkowski K., Jurga S., Skrzypczak A.

Structural and spectroscopic studies of DMPC/cationic surfactant system Aqueous suspension of a mixture of 1,2-dimyrilstoyl-sn-glycero-3-phosphocholine (DMPC) and (dodecyloxymethyl)dodecydimethylammonium (DDMDDAC) has been investigated by Fourier transform infrared spectroscopy (FTIR), small angle scattering of synchrotron radiation (SAXS) and dielectric spectroscopy (DS). The introduction of surfactant to DMPC water solution probably induces formation of discoidal (bicellar) phase, as revealed by SAXS studies. The presence of the surfactant has been found to decrease the main phase transition temperature, i.e., from rippled gel to liquid crystalline phase, as indicated by the DS and FTIR results. The small steps in the real part of dielectric permittivity plot vs. temperature can be related to the: planar gel to rippled gel (L(beta') -> P(beta')) and rippled gel-liquid crystal (P(beta') -> L(alpha)) phase transitions, which is supported by the temperature dependencies of the symmetric and anti-symmetric CH(2) band frequencies from FTIR measurements.
(C) 2010 Elsevier B.V. All rights reserved.

Journal of Non-Crystalline Solids, 356(11-17), 747-753 (2010)

DOI: 10.1016/j.jnoncrysol.2009.07.043


76.

Taube M., Jarmołowski A., Kozak M.

Low resolution structure of RAR1-GST-Tag fusion protein in solution RAR1 is a protein required for resistance mediated by many R genes and function upstream of signaling pathways leading to H(2)O(2) accumulation. The structure and conformation of RAR1-GST-Tag fusion protein from barley (Hordeum vulgare) in solution was studied by the small angle scattering of synchrotron radiation. It was found that the dimer of RAR1-GST-Tag protein is characterized in solution by radius of gyration R(G) = 6.19 nm and maximal intramolecular vector D(max) = 23 nm. On the basis of the small angle scattering of synchrotron radiation SAXS data two bead models obtained by ab initio modeling are proposed. Both models show elongated conformations. We also concluded that molecules of fusion protein form dimers in solution via interaction of GST domains.

Acta Physica Polonica A, 117(2), 307-310 (2010)

WWW: http://przyrbwn.icm.edu.pl/APP/PDF/117/a117z211.pdf


75.

Pietralik Z., Taube M., Skrzypczak A., Kozak M.

SAXS study of influence of gemini surfactant, 1,1'-(1,4-butanediyl)bis 3-cyclododecyloxymethylimidazolium di-chloride, on the fully hydrated DMPC The study has been performed on model systems of biological membranes obtained on the basis of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and cationic gemini surfactant derivative of 1,1'-(1,4-butane)bis 3-alkyloxymethylimidazolium chlorides with cyclic chains. The small angle X-ray scattering SAXS results implied a gradual disappearance (as a function of surfactant concentration) of the lamellar phase typical of DMPC and formation of unilamellar phase - probably a bicellar phase.

Acta Physica Polonica A, 117(2), 311-314 (2010)

DOI: 10.12693/APhysPolA.117.311
WWW: http://przyrbwn.icm.edu.pl/APP/PDF/117/a117z212.pdf   (Pobrane:  2021-01-10)


74.

Dobies M., Kozak M., Jurga S., Grubb A.

The dispersion of water proton spin-lattice relaxation rates in aqueous human protein HC (α1 - microglobulin) solutions The H-1 NMR Fast Field Cycling relaxometry was applied to study the molecular dynamics of the human protein HC (alpha(1)-microglobulin), its hydration and aggregation in solution state. The H-1 NMRD data have revealed the complex nature of the water/protein HC system resulting from the co-existence of monomer and dimer forms of the protein in solution as well as the presence of oligosaccharides linked to the polypeptide chain. A comparison of the average correlation time values obtained from the model-free fits with the values predicted on the basis of hydrodynamic tau(r) theory, suggests that the dynamics in solution state is governed mainly by the dimer form of the protein HC (the dominant contribution to the water proton-spin lattice relaxation comes from exchanging protons from the surface of the dimer). The existence of small number of oligomeric forms of the protein HC in solutions is postulated because of the two-step shape of water proton spin-lattice relaxation rate dispersion profiles.

Protein and Peptide Letters , 16(12), 1496-1503 (2009)

DOI: 10.2174/092986609789839241


73.

Kozak M., Włodarczyk A., Dobek A.

Synchrotron radiation small angle scattering studies of d(TTAGGG)4 oligomer in solution Telomeric DNA sequences play a crucial role in maintaining chromosome stability and integrity. In human chromosomes telomeres are composed of tandem (TTAGGG)(n) repeats. The structural parameters and low-resolution structure of a synthetic d(ITAGGG)(4) oligomer in solution has been studied in the absence and in the presence of potassium cations, with the use of the small angle scattering of synchrotron radiation. The radii of gyration R-G, calculated for d(TTAGGG)(4) oligomer (in 10 mM Tris/HCl pH 7.3) was 1.42 nm, while R-G, (in 10 mM Tris/HCl pH 7.3; 0.1 mM KCl) was 1.32 nm. The pair distance distribution function, P(r), yielded a maximum dimension of 4.55and 4.35 nm for solutions in the absence and the presence of potassium cations. On the basis of SAXS data, the low-resolution structure in solution has been reconstructed using ab inito methods.
(C) 2009 Elsevier Ltd. All rights reserved.

Radiation Physics and Chemistry, 78(10), S134-S136 (2009)

DOI: 10.1016/j.radphyschem.2009.04.028


72.

Kozak M., Taube M.

SAXS-WAXS studies of the low-resolution structure in solution of xylose/glucose isomerase from Streptomyces Rubiginosus The structure and conformation of molecule of xylose/glucose isomerase from Streptomyces rubiginosus in solution (at pH 6 and 7.6; with and without the substrate) has been studied by small- and wide-angle scattering of synchrotron radiation (SAXS-WAXS). On the basis of the SAXS-WAXS data, the low-resolution structure in solution has been reconstructed using ab inito methods. A comparison of the models of glucose isomerase shows only small differences between the model in solution and the crystal structure.
(C) 2009 Elsevier Ltd. All rights reserved.

Radiation Physics and Chemistry , 78(10), 125-128 (2009)

DOI: 10.1016/j.radphyschem.2009.03.085


71.

Kozak M., Szpotkowski K., Kozak A., Zieliński R., Wieczorek D., Gajda M.J., Domka L.

The FTIR and SAXS studies of influence of a morpholine derivatives on the DMPC-based biological membrane systems Fourier transformed infrared (FTIR) spectroscopy and small-angle scattering of synchrotron radiation have been used to analyze the influence of two zwitterionic surfactants of the sulfobetaine structure (3-(N-decylmorpholine)-1-propansulfonate and 3-(N-tetradecylmorpholine)-1-propansulfonate) on the conformational dynamics of CH2 and O-P-O groups of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and the structure of phospholipid bilayers. The presence of the surfactant causes changes in the DMPC phase transition temperature. Our small-angle X-ray scattering (SAXS) data analysis implies a gradual disappearance of the lamellar phase typical of DMPC and a probable formation of the bicellar phase or cubic phase in DMPC/surfactants system.
(C) 2009 Elsevier Ltd. All rights reserved.

Radiation Physics and Chemistry, 78(10), S129-S133 (2009)

DOI: 10.1016/j.radphyschem.2009.03.090


70.

Kozak M., Szpotkowski K., Kozak A., Zieliński R., Wieczorek D., Gajda M.J.

The effect of selected zwitterionic surfactant on the structure of hydrated DMPC Differential scanning calorimetry, Fourier transformed infrared (FTIR) spectroscopy and small angle scattering of synchrotron radiation have been used to analyse the influence of zwitterionic surfactant (3-(N-hexylmorpholine)-1-propansulfonate) on the conformational dynamics of CH(2) and CH(3) groups of 1,2-dimyrilstoyl-sn-glycero-3-phosphocholine (DMPC) and the phase behaviour of phospholipid bilayers. The surfactant causes changes in the DMPC phase transition temperature and promotes a gradual disappearance of the lamellar phase of DMPC and a probable formation of the bicellar phase.
(C) 2009 Elsevier Ltd. All rights reserved.

Radiation Physics and Chemistry, 78(10), S112-S115 (2009)

DOI: 10.1016/j.radphyschem.2009.04.029


69.

Marczewski A.W., Derylo-Marczewska A., Skrzypek I., Pikus S., Kozak M.

Study of structure properties of organized silica sorbents synthesized on polymeric templates Mesoporous silica materials were synthesized by applying Pluronic type polymers as pore creating agents. The composition of a reacting mixture and the process conditions were changed in a synthesis procedure. These changes differentiated the characteristics of porous structure of obtained sorbents. The parameters characterizing the pore structure were estimated and the changes of pore arrangement of obtained materials being a result of different synthesis conditions were investigated. The small-angle XRD results indicate that F cubic structure was formed what con- firms the cage-like ordering of the synthesized silicas.

Adsorption, 15(3) , 300-305 (2009)

DOI: 10.1007/s10450-009-9183-8


68.

Banachowicz E., Kozak M., Patkowski A., Meier G. and Kohlbreche J.

High-pressure small-angle neutron scattering studies of glucose isomerase conformation in solution Small-angle neutron scattering (SANS) of solutions of glucose/xylose isomerase from Streptomyces rubiginosus was measured as a function of pressure. It is shown that the structure of the enzyme in solution as seen by SANS is practically the same as that in the crystal and does not change with pressure up to 150 MPa. This reflects the unusually high structural stability of this material, which makes it extremely interesting to use as a secondary standard for pressure-dependent SANS experiments. This lack of pressure dependence of the SANS data also indicates that any possible change in hydration of the protein induced by pressure is not visible in the SANS curves. An appropriate correction procedure must be used for the SANS data in order to account for the distortion of the intensity curve due to hard-sphere and electrostatic interactions. After this correction, the isomerase can be readily used as a secondary standard for SANS measurements.

Journal of Applied Crystallography, 42, 461-468 (2009)

DOI: 10.1107/S0021889809007456


67.

Szpotkowski K., Kozak M., Kozak A., Zieliński R., Wieczorek D., Jurga S.

Structural studies of selected DSPC-surfactant model systems of biological membranes Fourier transform infrared spectroscopy was used to analyse the influence of a cationic surfactant from the group of morpholine derivatives on the conformational dynamics of CH2 group in acyl chain of DSPC. The presence of the surfactant causes a decrease in the DSPC phase transition temperature. This result suggests that the surfactant interactions with phospholipid molecules disturb the lipid layers. The Fourier transform infrared measurements were supplemented with tests of the environmental toxicity of the surfactant used.

Acta Physica Polonica A , 115(2), 561-564 (2009)

DOI: 10.12693/APhysPolA.115.561
WWW: http://przyrbwn.icm.edu.pl/APP/PDF/115/a115z225.pdf   (Pobrane:  2021-01-10)


66.

Derylo-Marczewska A., Marczewski A.W., Skrzypek I., Pikus S., Kozak M.

Effect of addition of pore expanding agent on changes of structure characteristics of ordered mesoporous silicas A series of mesoporous silica materials were synthesized by applying two types of Pluronic copolymers as pore creating agents. Differentiation of pore structure of the obtained sorbents was attained by changing the amount of trimethylbenzene as pore expander introduced to a reacting mixture. The parameters characterizing porous structure were estimated from nitrogen adsorption/desorption isotherms. The changes of pore arrangement in the synthesized materials were investigated by using X-ray diffraction. The structural transformations were found at the TMB/polymer ratio of 0.8 and 1. Correlations between the values of structure parameters and the content of TMB were found.
(C) 2008 Published by Elsevier B.V.

Applied Surface Science, 255(5), 2851-2858 (2008)

DOI: 10.1016/j.apsusc.2008.08.026   (Pobrane:  2020-10-21)


65.

Szymańska A., Hornowski T., Kozak M., Ślósarek G.

The SAXS and rheological studies of HEWL amyloid formation We performed small angle X-ray scattering and rheological experiments in order to analyze the aggregation and denaturation processes of hen egg white lysozyme initiated by the presence of ethanol molecule. At low ethanol concentrations (below 60% (v/v)) we did not observe any change of the radius of gyration of lysozyme and no drastic changes in viscosity of the protein solution. With the increase in ethanol concentration up to the final concentration of 85% (v/v) the viscosity of protein solution dramatically increased. For high ethanol concentration a pseudoplastic behavior of lysozyme solution was observed, indicating a process of aggregation and reorientation of the protein molecules. Similar effects were observed in small angle X-ray scattering experiments. We assume that the analysis of the aggregation processes of the hen egg white lysozyme could contribute to our understanding of the mechanism of lysozyme amyloid formation.

Acta Physica Polonica A, 114(2), 447-454 (2008)

DOI: 10.12693/APhysPolA.114.447
WWW: http://przyrbwn.icm.edu.pl/APP/PDF/114/a114z216.pdf   (Pobrane:  2021-01-10)


64.

Marciniec B., Stawny M., Kozak M., Naskrent M.

The influence of radiation sterilization on thiamphenicol The effect of ionising radiation, applied in the form of an electron beam, in the doses of 25, 100 and 400kGy on the physical and chemical properties of thiamphenicol in solid phase has been studied by organoleptic analysis (form, colour, smell, solubility, clarity) and spectroscopic methods (UV, IR, EPR), chromatography (TLC), SEM observations, X-ray diffraction, polarimetry and thermal method (DSC).
The above-discussed results have proved that on irradiation with a dose of 25 kGy no significant changes appear in thiamphenicol, apart from the formation of free radicals of the lifetime of over 352 days. On irradiation with much higher doses (100 and 400 kGy) no changes were observed in the IR spectra but the UV line intensities slightly increased at lambda(max) = 266 and 273 nm, the colour of the powder changed, the radiolysis products appeared as detected by TLC, changes were also observed in the XRD, SEM pictures, the melting point values (DSC) and optical rotation.
On the basis of DSC results a linear relation was found between the irradiation dose and the decrease in the melting point and increase in the enthalpy of melting, characterised by high correlation coefficients of r = 0.9839 and 0.9622, respectively. Moreover, a linear relation was established between the optical rotation angle and the irradiation dose, alpha(D) (degrees) =f(dose), characterised by the correlation coefficient r = 0.9874.
The results obtained indicate that thiamphenicol can be safely subjected to radiation sterilization by the standard dose of 25 kGy.
(C) 2007 Elsevier B.V. All rights reserved.

Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy, 69(3) , 865-870 (2008)

DOI: 10.1016/j.saa.2007.05.038   (Pobrane:  2020-10-21)


63.

Kozak M., Kempka M., Szpotkowski K., Jurga S.

NMR in soft materials: A study of DMPC/DHPC bicellar system The DMPC/DHPC bicellar system at the molar ratio of 2.8:1 has been characterised by measurements of self-diffusion coefficient (using PFGSE and PFGSTE NMR sequences), differential scanning calorimetry (DSC) and small angle scattering of synchrotron radiation (SAXS). The DSC curve shows only one endothermic peak characterised by the peak temperature T-peak = 295.7 K and the onset temperature T-onset = 290.1 K. This peak can be assigned to the nematic to smectic phase transition. Below the phase transition temperature, NMR diffusion experiments indicate a two-exponential decay of the spin echo amplitude allowing two diffusion coefficients D, and D-2 to be extracted from the experimental data. The maximum size (D-max) of the bicelle determined from SAXS data using the pair distance distribution function p(r) is 11.2 nm and the bilayer thickness is 5 nm.
(C) 2007 Published by Elsevier B.V.

Journal of Non-Crystalline Solids, 353(47-51), 4246-4251 (2007)

DOI: 10.1016/j.jnoncrysol.2007.02.068   (Pobrane:  2020-10-21)


62.

Kozak M., Domka L., Jurga S.

The effect of selected surfactants on the structure of a bicellar system (DMPC/DHPC) studied by SAXS The stabilizing or disturbing effect of different surfactants on the bicellar phase of phospholipids significantly depends on their type. The effect of different surfactants on the bicellar structure made of a mixture of phospholipids 1,2-dimyristoyl-sn-glycero-3-phosphocholine and 1.2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC/DHPC) has been studied by the small angle scattering of synchrotron radiation. The study has been performed for three surfactants: dodecyldimethyl-(hexyloxymethyl)ammonium chloride, n-undecylammonium chloride and t-octylphenoxypolyethoxyethanol (Triton X-100) introduced into a bicellar solution of DMPC/DHPC (2.8:1). The bicellar phase has been disturbed in the shortest time in the presence of dodecyldimethyl-(hexyloxymethyl)ammonium chloride in this system a transition from the bicellar to lamellar structure has been directly visible. The changes have been less pronounced in the presence of undecylammonium chloride and practically not noted in the presence of Triton X-100.
(C) 2007 Elsevier B.V. All rights reserved.

Journal of Molecular Structure, 846(1-3), 108-111 (2007)

DOI: 10.1016/j.molstruc.2007.01.038


61.

Kozak M., Grubb A.

SAXS studies of human protein HC (alpha1-microglobulin) Protein HC is a low molecular weight heterogeneous glycoprotein widely distributed in human body fluids and belonging to the lipocalin superfamily. The monomer contains a single (183 amino acid residues long) peptide chain with 3 cysteine residues (2 of which form a disulfide bridge) and is glycosylated. The molecular mass of the glycosylated protein is about 27 kDa. Native gel electrophoresis results revealed partial oligomerisation of protein HC, which therefore was analysed by gel filtration. Two forms (monomer and dimer) of the protein HC were isolated. The SAXS data were recorded on an X33 camera using synchrotron radiation (lambda=0.15 nm) at X33 beamline at the DORIS storage ring of DESY (Hamburg, Germany). Solution scattering results permitted determination of the structural parameters of both forms of the protein studied. The monomer of protein HC is characterised by a radius of gyration R-G = 2.20 nm and D-max =63 nm and the dimer by R-G=2.99 nm and D-max = 9.5 nm.

Protein and Peptide Letters, 14(5), 425-429 (2007)

DOI: 10.2174/092986607780782830


60.

Kozak M., Domka L., Jurga S.

Interactions of cationic surfactants with DPPC The effects of different cationic surfactants (n-undecylammonum chloride, UDACl and dodecyldimethyl (dodecyloxymethyl) ammonium chloride, DDMDDACl) on fully hydrated 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) vesicles have been studied. In the studied systems the molar ratio (x) of DPPC/surfactant ranged between x=0.0164-0.82 and from x=0.0352-1.76 for DPPC/DDMDDACl and DPPC/UDACl, respectively. For both systems, the enthalpy associated with the phase transition significantly decreases even at the lowest surfactant concentration. Also the main phase transition temperature is shifted towards lower temperatures. The structural parameters of the phases have been characterised by small angle X-ray scattering (SAXS). The SAXS results have proved that UDACl at x=0.0352 molar ratio significantly influences the DPPC lamellar structure, while its total disappearance was observed for x=0.176. The presence of DDMDDACl causes a total disappearance of the DPPC lamellar structure already at the lowest molar ratio (x=0.0352). Each surfactant in the system with DDPPC leads to a mixed micellar phase formation.

Journal of Thermal Analysis and Calorimetry, 88(2), 395-399 (2007)

DOI: 10.1007/s10973-006-8061-9


59.

Marciniec B., Kozak M., Naskrent M., Dettlaff K., Ogrodowczyk M., Stawny M., Wachowski L.

Thermal study of four irradiated imidazoline derivatives in solid state Four imidazoline derivatives: antazoline (AN), naphazoline (NN), tymazoline (TM), xylometazoline (XM), in the form of hydrochlorides in solid phase have been subjected to high energy e-beam irradiation from an accelerator (similar to 10 MeV) at a dose varied from 25 to 200 kGy. The effects of the irradiation have been assessed by DSC, X-ray diffraction, FTIR, EPR and TLC. The standard sterilisation dose of 25 kGy has been found to produce changes in the properties of one derivative (XM), two other ones (AN and TM) have been found sensitive to doses > 100 kGy, whereas NN has been resistant to irradiation in the whole range studied (25-200 kGy). EPR results indicated that the changes taking place in the therapeutic substances studied are related to radical formation. The irradiation induced changes in colour, a decrease or increase in the melting point, changes in the XRD pattern, small changes in the shape of FTIR peaks and the presence of radiolysis products. The XM compounds cannot be sterilised by irradiation because of the radiation induced changes in its physico-chemical properties.

Journal of Thermal Analysis and Calorimetry, 88(2), 337-342 (2007)

DOI: 10.1007/s10973-006-8060-x


58.

Pikus S., Solovyov L.A., Kozak M., Jaroniec M.

Comparative studies of p6m siliceous mesostructures by powder X-ray diffraction and nitrogen adsorption Two-dimensional mesostructures with p6m symmetry such as MCM-41 and SBA-15 are the subject of intensive studies by using nitrogen and argon adsorption, transmission electron microscopy, and powder X-ray diffraction/scattering techniques. The latter may involve the X-ray diffraction (XRD) or small angle X-ray scattering (SAXS) measurements. The XRD/SAXS patterns for the aforementioned ordered mesostructures often exhibit four or more reflections, the most intensive one, 1 0 0 peak, and three less intensive peaks, 1 10, 2 0 0, 2 1 0. So far, analysis of these patterns was usually limited for the evaluation of the unit cell parameter and the identification of the observed peaks. In this work we present an attempt to analyze the XRD/SAXS patterns by including not only the position of observed peaks but also their intensity. It is shown that the intensity of these peaks, especially I 1 0 peak, depends on the ratio of the pore diameter to the unit cell parameter. In particular, this dependence was studied for the intensity ratio of 1 10 and 2 0 0 peaks assuming 2 0 0 peak as a reference reflection because of its nearness to I 10 peak (which minimizes the influence of other factors than the structural ones on the 1 1 0/2 0 0 intensity ratio analysis) and similar intensity to that of 1 1 0 peak. The values of the 1 1 0/2 0 0 intensity ratio were determined for many MCM-41 and SBA-15 samples and analyzed in relation to the pore width/ unit cell ratio, where the pore width was estimated on the basis of nitrogen adsorption data or by the XRD/SAXS structure modeling. Comparative analysis of this intensity ratio for numerous MCM-41 and SBA-15 samples allows for a quick estimation of the pore width and provides some information about hexagonality of mesopores in these materials.
(C) 2007 Elsevier B.V. All rights reserved.

Applied Surface Science, 253(13), 5682-5687 (2007)

DOI: 10.1016/j.apsusc.2006.12.043   (Pobrane:  2020-10-21)


57.

Kozak M., Domka L., Jurga S.

SAXS study of selected cationic surfactant influence on the DSPC-based model phospholipid system The phase behaviour of lipid bilayer systems prepared with 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) with dodecyldimethyl(benzyloxymethyl)ammonium chloride (BzMDDAC) (at concentrations 0.1, 1 and 5%) has been studied by small angle X-ray scattering and differential scanning calorimetry. The SAXS and DSC results of the hydrated 10% DSPC revealed one typical phase transition corresponding to melting of the hydrocarbon chains at 5 5 degrees C. In the system of 10% DSPC - 0.1% BzMDDAC the main transition was somewhat shifted towards lower temperatures, while at 1% concentration of BzMDDAC in the mixture, the lamellar phase disappeared, as evidenced by SAXS and DSC. The increase in BzMDDAC concentration to 5% in the mixture with 10% DSPC resulted in formation of a new lamellar phase.

Solid State Phenomena, 130, 257-262 (2007)

DOI: 10.4028/3-908451-40-x.257   (Pobrane:  2021-01-10)


56.

Kozak M.

Synchrotron radiation small angle scattering studies of thermal stability of xylanase XYNII from Trichoderma Longibrachiatum Xylanase XYNII from Trichoderma longibrachiatum is a small protein of the molecular weight 21 kDa, belonging to the family I I of glycosyl hydrolases, which catalyses hydrolysis of xylan. This article reports thermal stability study of xylanase XYN II conformation in the temperature range 15-65 degrees C by the small angle synchrotron radiation scattering. The study has been performed at different pH conditions: at pH 4.0 (below the physiological optimum of the enzyme activity) at pH 5.8 close to the optimum for enzymatic activity and at pH 8.0. The radius of gyration and the pair distance distribution function p(r) have been analyzed to characterize the changes of the enzyme conformation on heating. In the environment of the pH close to that of the optimum for the enzymatic activity, xylanase shows the greatest thermal stability and undergoes denaturation only above 55 degrees C. In the acidic and basic environments, the enzyme stability is much lower and denaturation begins at 45 degrees C. On the basis of the SAXS data, the shape of the Xylanase molecule in solution in different temperatures has been reconstructed using ab initio method and program DAMMIN. The shape of the xylanase molecule at room temperature is similar to the right hand, which is typically observed for xylanase crystal structure. In higher temperatures (close to the enzyme activity optimum), the conformation of the right hand is loosened and half opened.
(C) 2006 Wiley Periodicals, Inc.

Biopolymers, 83(6), 668-674 (2006)

DOI: 10.1002/bip.20605


55.

Król P., Król B., Pikus S., Kozak M.

Polyurethane anionomers synthesised with aromatic, aliphatic or cycloaliphatic diisocyanates, polyoxyethylene glycol and 2,2-bis-(hydroxymethyl)propionic acid Small angle X-ray scattering and differential scanning calorimetry methods were employed to characterise the internal order of structural phases present in polyurethane coatings obtained as a result of water evaporation from anionomer dispersions. Those anionomers were produced in the reaction of aromatic, cycloaliphatic and aliphatic diisocyanates with polyoxyethylene glycol, 2,2-bis-(hydroxymethyl)propionic acid and 1,6-hexamethylenediamine. The decisive effects were found from ionic and polar structures within the rigid urethane and urea segments on the ordered arrangement degree of the supermolecular structures in the obtained anionomers. That becomes apparent in differential scanning calorimetry thermograms and contributes to improved thermal stability of the produced polyurethane coatings.

Colloid and Polymer Science, 285(2), 169-175 (2006)

DOI: 10.1007/s00396-006-1543-2   (Pobrane:  2021-01-20)


54.

Kozak M.

Solution scattering studies of conformation stability of xylanase XYNII from Trichoderma Longibrachiatum Xylanase (endo-1,4-beta-xylanase; EC 3.2.1.8) is an enzyme that catalyzes the hydrolysis reaction of xylan. The structure of the xylanase H (XYNII) molecule from Trichoderma longibrachoatum (formerly Trichoderma reesei) in a solution and at different pH values has been studied by small- and wide-angle scattering of synchrotron radiation (SAXS-WAXS). Analysis of the radius of gyration that characterizes xylanase has confirmed the stability of the above enzyme structure (the radius of gyration varied from 1.65 to 1.74 nm). On the basis of the SAXS data, the low-resolution structure of the xylanase molecule in solution has been reconstructed by using ab initio methods and programs DALAI_GA and DAMMIN. The full SAXS-WAXS data set (0.15 > s > 9.5 nm(-1)) fed to the program GASBOR permitted us to construct a chain-like spatial distribution of a dummy residues model of the xylanase molecule. The shape of the model molecules is similar to that of xylanase molecule in the crystal and shows the characteristic asymmetry that makes the molecule to resemble a right hand.
(C) 2006 Wiley Periodicals, Inc.

Biopolymers, 83(1), 95-102 (2006)

DOI: 10.1002/bip.20531


53.

Kozak M., Domka L., Foltynowicz Z., Jakubiak P., Jurga S.

Studies on the structure of polyethylene-modified bentonite nanocomposites LDPE modified with vinyltriethoxysilane and lactic acid and a natural bentonite organophilized with hexadecyltrimethylammonium bromide were used to extrude biodegradable nanocomposites contg. 4% bentonite and 30% lactic acid. Elongation-at-break and stretching strength were improved by 29% and 12% as compared with the starting composites. Microstructure examn. showed the polymer matrix to be more compact with the nanofiller added. The m.p. and the m. enthalpy of the nanocomposite were 114.7 degrees C (higher by 2 degrees C) and -134.2 J/g (higher by similar to 10 degrees/6), resp.

Przemysł Chemiczny, 85(8-9), 840-843 (2006)


52.

Kozak M., Domka L., Malicka A.

Preparation and physicochemical analysis of layered silicates modified with silane coupling agents Natural Na bentonite contg. 65% montmorillonite and synthetic Na montmorillonite were mixed 2 hrs. in aq. 50% EtOH with 2 wt. parts of 3-chloropropyl (I) or 3-methacryloxypropyl trimethoxysilane (II). The av. particle size of modified montmorillonite was 10-15 lm vs. the 10 in the original. The II-modifted bentonite had particles up to 60 lm. The interlayer distance in Na montmorillonite was changed by I only slightly, 1.244 vs. 1.265 nm, and likewise in bentonite, regardless of the coupler type. Up to 1000 degrees C, wt. loss was 1%. In I- or II-moditled montmorillonite, the loss was 2.8 and 4.7% and the DTG peaks at 390-460 and 345-465 degrees C, resp., were attributed to the decompg. silanes. Only the silane surface was affected and penetration of silane mols. into the interlayer space was insignificant.

Przemysł Chemiczny, 85(8-9), 844-846 (2006)


51.

Grudzień R.M., Grabicka B.E., Kozak M., Pikus S., Jaroniec M.

Effect of polymer-to-silica ratio on the formation of large threedimensional cage-like mesostructures This work shows the influence of polymer-to-silica ratio on the formation of cage-like ordered mesoporous silica, FDU1, having a three-dimensional face-centered cubic symmetry. The FDU1 samples studied were synthesized from tetraethyl orthosilicate (TEOS) under acidic conditions in the presence of poly(ethylene oxide)-poly(butylene oxide)-poly(ethylene oxide) (EO39BO47EO39) triblock copolymer. The molar ratio of triblock copolymer to TEOS in the reaction mixture was varied from 0.0037 to 0.0148. Small angle X-ray scattering, argon adsorption-desorption and high resolution thermogravimetry studies indicate that an optimal EO39BO47EO39/TEOS ratio, which led to a high-quality FDU1 material with uniform cage openings, narrow pore size distribution and high specific surface area, was about 0.0074. The FDU1 silicas obtained for lower and higher ratios than the aforementioned value possessed non-uniform cage entrances, broader pore size distributions, lower BET specific surface areas and smaller mesopore diameters.

New Journal of Chemistry, 30, 1071-1076 (2006)

DOI: 10.1039/b603436e


50.

Marciniec B., Stawny M., Kozak M., Naskrent M.

The effect of ionizing radiation on chloramphenicol No significant changes relative to the unirradiated sample were observed as a result of irradiation with the dose of 25 kGy - a standard dose for radiation sterilization, besides free radicals generation. Higher doses were found to produce a change in colour, increase in absorbance (UV), changes in the XRD spectra and appearance of products of radiolysis. The presence of the radiolysis products was confirmed by the TLC method, indirectly by DSC showing a decrease in the melting point from 0.2 to 4.5 degrees C and enthalpy from 3.8 to 23.3 J g(-1), respectively. A linear relationship was obtained between the irradiation dose (25-400 kGy) and the melting point of chloramphenicol, characterised by the correlation coefficient r=0.9968. The EPR signal intensity increased with increasing dose of irradiation and the lifetime of the free radicals was longer than 6 months. No changes were detected in SEM and IR spectra. As follows from our results, the DSC method is most suitable for a fast monitoring of the drugs subjected to sterilization by irradiation as it permits detection of changes occurring even on irradiation with low doses and their quantitative description.

Journal of Thermal Analysis and Calorimetry, 84(3), 741-746 (2006)

DOI: 10.1007/s10973-005-7545-3


49.

Ślósarek G., Kozak M., Gierszewski J., Pietraszko A.

Structure of N-6-furfurylaminopurine (kinetin) dihydrogenphosphateStructure of N-6-furfurylaminopurine (kinetin) dihydrogenphosphate The crystal structure of kinetin dihydrogenphosphate has been determined at 115 and 293 K. Kinetin dihydrogenphosphate undergoes a polymorphic phase transition at 291.1 K. In both phases the crystal belongs to the triclinic system with the symmetry described by the space group P (1) over bar . In the low-temperature phase, the unit cell is doubled along the a axis. There is a dynamic equilibrium between different tautomeric forms of the adenine residue, determined by the distribution of H atoms within the network of hydrogen bonds.

Acta Crystallographica Section B - Structural Science Crystal Engineering and Materials, 62(1), 102-108 (2006)

DOI: 10.1107/S010876810502673X


48.

Deryło-Marczewska A., Marczewski A.W., Skrzypek I., Pikus S., Kozak M.

The effect of aging temperature on structure characteristics of ordered mesoporous silicas A series of mesoporous silica materials were synthesized by applying Pluronic type polymers as pore creating agents. In order to differentiate the characteristics of porous structure of the obtained sorbents the temperature of aging process was changed in the synthesis. The parameters characterizing the pore structure were estimated from nitrogen adsorption/desorption isotherms. The changes of pore arrangement of the obtained materials being a result of different synthesis conditions were investigated by using a small angle X-ray scattering method. Correlations between the values of structure parameters and aging temperature were found.
(C) 2005 Elsevier B.V. All rights reserved.

Applied Surface Science, 252(3), 625-632 (2005)

DOI: 10.1016/j.apsusc.2005.02.081   (Pobrane:  2020-10-21)


47.

Kozak M.

Direct comparison of the crystal and solution structure of glucose/xylose isomerase from Streptomyces rubiginosus Glucose isomerase (D-xylose ketol-isomerase, EC 5.3.1.5.) catalyses the isomerization reaction of glucose and xylose. The small angle X-ray scattering (SAXS) data of glucose/xylose isomerase from Streptomyces rubiginosus were recorded for protein solution using synchrotron radiation. The experimental data were compared with theoretical scattering calculated on the basis of the known crystal structure (PDB code: 10AD). The radius of gyration measured by SAXS (R-G=3.30 nm) was almost identical and the maximum dimension in the distance distribution function was by about 2.5 % lower than the corresponding values calculated on the basis of the crystal structure.

Protein and Peptide Letters, 12(6), 547-550 (2005)

DOI: 10.2174/0929866054395851


46.

Krzaczkowska J., Fojud Z., Kozak M., Jurga S.

Spectroscopic studies of poly(epsilon-caprolactone)/sodium montmorillonite nanocomposites Polymer-layered silicate nanocomposites belong to a new class of hybrid materials consisting of organic-synthetic polymer matrix and inorganic filler-layered structure clay minerals. The paper presents the results of FTIR, NMR, and SAXS studies of poly( epsilon -caprolactone)/sodium montmorillonite nanocomposites. We observed a correlation between the concentration of poly( epsilon -caprolactone) in nanocomposite samples and structural changes both of the clay mineral and the intercalated polymer. Stiffening of the clay structure appears as a result of poly(epsilon -caprolactone) intercalation into a clay structure. 27Al NMR studies indicated in nanocomposites two non-equivalent sites of aluminium ions, i.e. in octahedral and tetrahedral coordination, whereas in the montmorillonite clay structure the aluminium ions are located in the interlayer space too. We found also that the temperatures of structural changes and softening process of poly( epsilon-caprolactone) chains in the nanocomposites depend on the concentration of poly( epsiv -caprolactone).

Acta Physica Polonica A, 108(1), 187-196 (2005)

DOI: 10.12693/APhysPolA.108.187
WWW: http://przyrbwn.icm.edu.pl/APP/PDF/108/a108z124.pdf   (Pobrane:  2021-01-10)


45.

Kozak M.

Glucose isomerase from Streptomyces Rubiginosus - potential molecular weight standard for small-angle X-ray scattering Stability of solutions of glucose isomerase from Streptomyces rubiginosus on long-term storage and on exposure to synchrotron radiation has been studied by the small-angle X-ray scattering (SAXS) method. The values of the radii of gyration and forward scattering do not change significantly on storage and on exposure to synchrotron radiation. The mean value of the radius of gyration characterizing glucose isomerase is R-G = 3.27 ± 0.02 nm. For comparison, a SAXS study of monodispersive and aggregated bovine serum albumin (BSA) has been carried out. The results show that glucose isomerase could be a more stable molecular weight standard for SAXS than BSA.

Journal of Applied Crystallography, 38(3), 555-558 (2005)

DOI: 10.1107/S0021889805010472   (Pobrane:  2020-10-25)


44.

Kozak M., Jurga S.

SAXS study of lipid bilayer model systems. The phase diagram of n-undecylammonium chloride/water system Alkylammonium halides belong to cationic surfactants. In water solutions they can form bilayer systems whose properties mimic those of the lipid membranes. The n-undecylammonium chloride (C11H23NH3Cl; UDACl)/water system was studied by small angle X-ray scattering (SAXS) at the concentrations of UDACl from 15 to 70% and in temperature range from 20 to 70 ºC. The results permitted our drawing a fragment of phase diagram for this system. Three main phases: isotropic, lamellar and hexagonal were observed and characterized

Fibres and Textiles in Eastern Europe, 13(5), 93-95 (2005)

WWW: http://www.fibtex.lodz.pl/53_22_93.pdf


43.

Janowski R., Kozak M., Jankowska E., Grzonka Z., Jaskólski M.

Two polymorphs of a covalent complex between papain and a diazomethylketone inhibitor The three-dimensional structure of two polymorphs of a ZLFG-CH2-papain covalent complex has been determined by X-ray crystallography. The structures indicate that: (i) the methylene carbon atom of the inhibitor is covalently bound to the S atom of Cys25 of papain; (ii) the hydrophobic S2 pocket formed by Pro68, Val133, Val157, and Asp158 is occupied by the inhibitor's phenylalanyl P2 side chain; (iii) extensive hydrogen bonding and hydrophobic interactions are responsible for the interaction of the inhibitor with the enzyme. Comparison with similar structures suggests that in covalent complexes preservation of main chain-main chain interactions between the enzyme and the inhibitor may have higher priority than the P-S interactions

Journal of Peptide Research, 64, 141-150 (2004)

DOI: 10.1111/j.1399-3011.2004.00181.x


42.

Pikus S., Olszewska E., Kozak M.

SAS characterization of organic film deposited on porous silicas The small angle scattering methods can be used to investigate the density scattering profile at phase boundaries; in the following paper SAXS method was used for the characterization of organic film deposited on porous inorganic carriers. The existence of organic film on the surface of the porous carrier causes the changed in scattering; negative and positive deviations from Porod’s law can occurred. Significant differences in Porod’s plot of hydrated and dehydrated ZrO2 samples coated by bromododecanol were observed. These differences suggest considerable differences in alcohol molecules orientation on the two kinds of surface and confirm that the SAXS method can be used in determination of the structure of organic phase deposited on the porous surface.

Applied Crystallography, , 351-354 (2004)

DOI: 10.1142/9789812702913_0069   (Pobrane:  2020-10-23)


41.

Kozak M., Foltynowicz Z., Jakubiak P., Fojud Z., Domka L., Jurga S.

Preparation and structural study of the composites of polyethylene with modified bentonite The paper reports a study on obtaining and characterisation of organophilised bentonite. Modification of the bentonite studied has been confirmed by SEM, XRD and NMR results. The organoplilised filler has been used for preparation on nanocomposites based on polyethylene or polyethylene modified with vinyltriethoxysilane and lactic acid. The best mechanical parameters have been obtained for the composites on the basis of the modified polyethylene containing 4% of organophilised bentonite and 50% of lactic acid.

Mat. VI Konferencji Naukowo-Technicznej "Polimery i Kompozyty Konstrukcyjne", , 69-74 (2004)

   (Pobrane:  2021-01-08)


40.

Kozak M.

Direct comparison of the crystal and solution structure of xylanase from Trichoderma Longibrachiatum The small angle X-ray scattering (SAXS) data of xylanase XYNII (endo-1.4-beta-xylan xylanohydrolase EC 3.2.1.8) From Trichoderma logibrachiatum, an enzyme catalysing the reaction of accidental hydrolysis of beta-1.4-D-xylosidic linkages of xylan, were recorded for protein solution using synchrotron radiation. The experimental data were compared with those of theoretical scattering calulated on the basis of the known crystal structure. The radius of gyration measured by SAXS (RG=1.7 nm) was about 3.5% larger and the maximum dimension in the distance distribution function about 5% larger than the corresponding values calculated oil the basis of the crystal structure.

Protein and Peptide Letters, 11(4), 301-306 (2004)

DOI: 10.2174/0929866043406779


39.

Kozak M., Danch A., Osoba W., Domka L., Stelzer F., Jurga S.

Relationship between filler loading and morphology of the interphase in polyethylene-chalk composites Mineral fillers such as kaolin or chalk have been commonly used in the polymer industry as additives to improve polymer mechanical properties and, at the same time, reduce the cost of raw materials. The problem is that the hydrophilic surface of the filler hinders its introduction into the polymer matrix. The paper reports a study of low density polyethylene (LDPE) composites with a natural chalk content of up to 40% wt. The morphology of the filler molecules and the microstructure of the composites were determined by scanning electron microscopy (SEM). The distribution of the filler molecules was estimated by light scattering. The mean diameter of the filler particles was 926.3 nm and their polydispersity was 0.101. The thermal and mechanical properties of the composites were characterised by differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA). The enthalpy of melting, DeltaH(m)*, decreased by about 8% when the amount of filler was 10 wt% in the sample (PE10). However, no difference was recorded between the DeltaH(m) value of the sample with 40 wt% content of filler (PE40), and the value for PE10. In LDPE composites with 40% of chalk,the free space in the interphase is reduced, slightly increasing the chain mobility in comparison with that in the composite with 10% of chalk.

Polymers and Polymer Composites, 12(5), 409-416 (2004)

DOI: 10.1177/096739110401200505   (Pobrane:  2021-01-10)


38.

Kiersnowski A., Kozak M., Jurga S., Pigłowski J.

Structure and crystallization behaviour of poly(epsilon-caprolactone)/clay intercalated nanocomposites Nanocomposites of poly(epsilon-caprolactone)/M-HTAB were obtained by polymerization of caprolactone with various amounts (10, 30, 50 and 64 weight ratio) of montmorillonite organophilized with hexadecyltrimethylammonium bromide (HTAB). The microstructure of nanocomposites was studied by small angle X-ray scattering (SAXS). Additionally, the melting enthalpies (DeltaH(m)), the crystallinities and the half-time of isothermal crystallization were evaluated by differential scanning calorimetry (DSC). As a result of SAXS experiments for the composite PCL/M-HTAB 90/10, in the temperature range from 313 to 283 K, a rapid change in the interlamellar distance from 3.1 nm to 2.72 nm was observed. Similar scattering curves were obtained for the nanocomposite PCL/M-HTAB 70/30. In the composites containing 50% and 64% wt of M-HTAB, the decrease in interlayer distance was less pronounced in the same temperature range (d(001) 3.15 - 3.2 nm). DSC results clearly showed that the crystallization is divided into two separate processes: primary crystallization in the PCL matrix, and secondary crystallization.

Polymers and Polymer Composites, 12(8), 727-737 (2004)

DOI: 10.1177/096739110401200809   (Pobrane:  2021-01-10)


37.

Kuśmia S., Kozak M., Szcześniak E., Domka L., Jurga S.

Studies of water penetration into LDPE-calcium lactate composite Penetration of water into low-density polyethylene-calcium lactate composite is studied with NMR techniques. The presence of filler speeds up the water uptake by the polymer matrix and facilitates polyethylene degradation. Spatial distribution of absorbed water molecules within the composite visualised with MRI corroborates differences in dynamical behaviour of the absorbed water molecules revealed by T-2 measurements.
(C) 2003 Elsevier Inc. All rights reserved.

Solid State Nuclear Magnetic Resonance, 25(1-3), 173-176 (2004)

DOI: 10.1016/j.ssnmr.2003.03.027   (Pobrane:  2020-10-21)


36.

Dobies M., Kozak M., Jurga S.

Studies of gelation process investigated by fast field cycling relaxometry and dynamical rheology: the case of aqueous low methoxyl pectin solution The Fast Field Cycling Relaxometry and the dynamical rheology were applied to study the gelation process in aqueous low methoxyl pectin solution in the presence of divalent cations from the calcium chloride. The model-free approach to the analysis of H-1 NMRD data was used to separate the information on the static and dynamic behaviour of the system provided by the dispersion profiles of the systems tested. Mechanical spectroscopy was applied as a complementary method to probe the network formation. The structural changes were most pronounced for the concentration of calcium chloride between 10 and 15 mM (the static parameter beta was found to vary from 0.936 x 10(7) to 1.27 x 10(7) 1/s(2)) revealing the sol-gel transition on visual inspection. The presence of the gel network was confirmed by the rheological measurements. All mechanical spectra exhibited the gel like character, and the solid like response was more evident at higher concentrations of calcium cations. The mean correlation time increased with increasing salt concentration, but remained unchanged for the concentrations above 15 mM. The dynamical changes were most significant at the phase transition from the sol to the gel state.
(C) 2003 Elsevier Inc. All rights reserved.

Solid State Nuclear Magnetic Resonance, 25(1-3), 188-193 (2004)

DOI: 10.1016/j.ssnmr.2003.03.019   (Pobrane:  2020-10-21)


35.

Marciniec B., Kozak M., Ogrodowczyk M.

DSC study of radiostability of 1,4-dihydropyridine derivatives The effect of sterilisation by irradiation has been studied for the seven most often used in medicine derivatives of 1,4-dihydropyridine (nifedipine, nisoldipine, nicardipine, nitrendipine, nimodipine, felodipine and amlodipine). The sterilisation was performed for the compounds in the solid phase with an electron beam of the energy 10 MeV, at room temperature, using the irradiation doses from 20 to 400 kGy. The effects of the irradiation were studied by the methods SEM, DSC, XRD and TLC. The sterilisation with doses 20-100 kGy was found to cause no changes in the physico-chemical properties of the compounds, while the irradiation with higher doses (200-400 kGy) was found to induce changes in the colour, DSC spectrum and TLC picture. As follows from the TLC results, the main product of radiolysis of the compounds studied was a pyridine nitrozoderivative, which indicates the same mechanism of decomposition as in the process of photodegradation. The results prove that the 1,4-dihydropyridine derivatives being highly sensitive to visible and UV radiation are generally resistant to ionising radiation and thus can be subjected to sterilisation by irradiation.

Journal of Thermal Analysis and Calorimetry, 77(2), 581-596 (2004)

DOI: 10.1023/B:JTAN.0000038996.14324.34


34.

Marciniec B., Kozak M., Dettlaff K.

Thermal analysis in evaluation of the radiochemical stability of some fungicidal drugs Four azole derivatives showing antimycotic activity (Miconazole, Ketoconazole, Clotrimazole, Fluconazole) in solid phase were exposed to beta irradiation at the dose of 20–200 kGy and then alterations in the physicochemical properties of the above derivatives were studied using the methods: scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and X-ray diffraction (XRD) analysis. It was found that the compounds irradiated with sterilising doses (20–50 kGy) showed no significant alterations in their physicochemical properties, while application of doses >50 kGy resulted in small changes in the X-ray diffraction patterns and in the course of DSC curves, including a decrease in the melting points and enthalpy of the process. For Miconazole and Fluconazole, a linear and relatively strong correlation was found (from r =0.9782 to r =0.9003) between the size of the dose of irradiation and the decrease in the melting point and enthalpy value.

Journal of Thermal Analysis and Calorimetry, 77(1), 305-317 (2004)

DOI: 10.1023/B:JTAN.0000033215.77806.b0


33.

Marciniec B., Kozak M., Wachowski L., Ogrodowczyk M.

Evaluation of radiostability of some steroid derivatives The effect of ionising radiation (15-100 kGy) on the physico-chemical properties of 6 steroid derivatives in solid state (Hydrocortisone, Hydrocortisone acetate, Prednisolone, Prednisolone acetate, Dexamethasone and Fludrocortisone acetate) was studied by differential scanning calorimetry (DSC), differential thermal analysis (DTA), scanning electron microscopy (SEM), UV spectrophotometry, high-performance liquid chromatography (HPLC), X-ray powder diffraction and polarimetry. DSC and DTA results revealed that the irradiated compounds undergo phase transitions at lower temperatures, show lower melting points and lower enthalpy of the melting process their non-irradiated analogues. The results of HPLC measurements proved a loss in the active substance content after irradiation ranging from 0.5 to 2.88%. No significant effect of irradiation was detected by the UV spectrophotometry or polarimetry in the course of the UV spectrum, absorbancy or optical rotation, as well as in the SEM photographs and X-ray patterns. For some compounds studied a correlation was found between the irradiation dose and the shifts in DSC curves and the loss of content determined by the HPLC method. Similar, but not so much pronounced relations were established in or earlier studies of the derivatives of nitroimidazole and 1,4-dihydropyridine. In general the results have shown relatively high radiochemical stability of the compounds studied and have proved that the DSC method is a sensitive detector of irradiation-caused changes in drugs in solid phase.

Journal of Thermal Analysis and Calorimetry, 73, 473-485 (2003)

DOI: 10.1023/A:1025465726691


32.

Kozak M., Domka L.

Adsorption of the quaternary ammonium salts on montmorillonite Sodium montmorillonite SOMASIF((R)) ME 100 (M) has been subjected to modification through ion-exchange reaction by a number of (alkyloxymethyl)dodecyldimethylammonium chlorides with the general formula [C12H25N+(CH3)(2)CH2OR]Cl-. The modified samples were studied by X-ray diffraction (XRD) technique, Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM), and thermogravimetric analysis. The basal spacing of unmodified montmorillonite, determined by XRD, was 1.227 nm and after modification it increased up to 1.557 nm (montmorillonite modified with dodecyldimethyl(dodecyloxymethyl)ammonium chloride). The FTIR studies revealed structural differences between the modified and unmodified montmorillonite samples. The IR spectra of the modified montmorillonite showed the C-C stretching bands (1468 cm(-1)) and C-H vibrations (near 2930 and 2856 cm(-1)). Results of the SEM study revealed a tendency towards lump formation and agglomeration of the organophilised particles of montmorillonite.
(C) 2003 Elsevier Ltd. All rights reserved.

Journal of Physics and Chemistry of Solids, 65(2-3), 441-445 (2003)

DOI: 10.1016/j.jpcs.2003.09.015   (Pobrane:  2020-10-21)


31.

Domka L., Foltynowicz Z., Jurga S., Kozak M.

Influence of silane modification of kaolins on physico-mechanical and structural properties of filled PVC composites The paper presents the results of a study of the potential of modified kaolin as a filler for PVC. Kaolin from Maria III deposits in Poland was used. Aminosilanes and mercaptosilanes were used to modify the surface. Basic physicochemical parameters, such as the absorption capacity of the plasticiser, the heat of immersion in hydrophobic and hydrophilic solvents, and the morphology of particles of the modified filler were characterised. The modified kaolins clearly improved the physico-mechanical properties of PVC, in particular, they increased the elongation of PVC, when used at 10% and 15% w/w levels in the composite. Some studies of the microstructure of the filled composites were also performed using small angle X-ray scattering (SAXS) and scanning electron microscopy (SEM) techniques.

Polymers and Polymer Composites, 11(5), 397-406 (2003)

DOI: 10.1177/096739110301100505   (Pobrane:  2021-01-10)


30.

Domka L., Wąsicki A., Kozak M.

The microstructure and mechanical properties of new HDPE-chalk composites Increasing demands on the quality and specific properties of polymers imply increasing demands on the mineral fillers used in composite materials. They are expected not only to reduce the cost of production but also improve the mechanical properties of the composites or endow them with new features, e.g. thermostability. The paper presents a method for obtaining polyethylene composites with chalk modified by two new 1-alcoxymethyl-3-hydroxypyridinium chlorides: 3-hydroxy-1-octyloxymethylpyridinium chloride (salt 1) and 3-hydroxy-1-octadecyloxymethylpyridinium chloride (salt 2) and gives a characterisation of the composites obtained. Introduction of chalk modified with ammonium salts results in an increased values of MFI of the composites. The MFI changes are the most pronounced for the PE composites containing the filler in concentrations from 0.05 to 2.0% wt. Addition of the chalk modified with the ammonia salts causes greater changes in some mechanical properties of the composites (Young modulus) than addition of unmodified chalk, while changes in some other properties (stress at break) was practically the same.

Physicochemical Problems of Mineral Processing, 37(1), 141-147 (2003)

WWW: http://www.minproc.pwr.wroc.pl/journal/pdf/2003/141-147.pdf
ISSN: 1643-1049   (Pobrane:  2021-01-13)


29.

Kozak A., Kozak M., Domka L.

Chemistry for Agriculture, 4, 410-414 (2003)


28.

Kiersnowski A., Kozak M., Jurga S., Pigłowski J.

Badania SAXS i DSC nanokompozytów poli(epsilon-kaprolakton)/organofilizowany montmorylonit Nanokompozyty otrzymano na drodze interkalacyjnej polimeryzacji kaprolaktonu w obecności 10% i 50% wag. syntetycznego montmorylonitu sodowego organofilizowanego bromkiem heksadecylotrimetyloamoniowym (HTAB). Badania strukturalne uzyskanych nanokompozytów przeprowadzone techniką małokątowego rozpraszania promieni X przeprowadzone w zakresie -50˚ ± 70˚ dowiodły, że odległość międzypłaszczyznowa d0001 oraz stopień uporządkowania układu rosną wraz ze wzrostem temperatury. Aby wyjaśnić naturę obserwowanych przemian, próbki przebadano techniką różnicowej mikrokalorymetrii skaningowej (DSC). W oparciu o wyniki eksperymentów SAXS i DSC stwierdzono, że skok wartości d001 obserwowany w zakresie 0-45 ˚C spowodowany jest procesem krystalizacji PCLw matrycy oraz w obrębie galerii krzemianu. Zmiany poniżej i powyżej tego zakresu są efektem rozszerzalności termicznej polimeru zawartego w przestrzeniach międzypłaszczyznowych montmorylonitu.

Prace Naukowe Instytutu Technologii Organicznej i Tworzyw Sztucznych Politechniki Wrocławskiej, 52, 381-384 (2003)

   (Pobrane:  2020-10-25)


27.

Domka L., Jesionowski T., Morawska A., Kozak M.

Influence of pyridinium chlorides on the physicochemical character, morphology and particle size distribution of natural chalk Studies on the surface modification of natural chalk from the Sobkow deposits (Poland) were conducted using cationic surfactants for the modification. Newly synthesized 1-alkoxymethyl-3-hydroxypyridinium chlorides were employed as the modifiers. The unmodified and the modified chalk were subjected to physicochemical evaluation. The surface modification was analysed by differential scanning calorimetry (DSC). Bulk density and the capacity to absorb water, dioctyl phthalate and paraffin oil were also evaluated. Studies on dispersion and particle morphology were conducted using scanning electron microscopy (SEM) and dynamic light scattering (DLS). The results obtained made it possible to conclude that chalks modified with pyridinium salts may find broad application in construction, plastics processing and many other branches of industry.

Tenside Surfactants Detergents, 39(3), 33-39 (2002)


26.

Kozak M., Jurga S.

A comparison between the crystal and solution structures of Escherichia Coli asparaginase II The small angle X-ray scattering (SAXS) pattern of the homotetrameric asparaginase II from Escherichia coli was measured in solution in conditions resembling those in which its crystal form was obtained and compared with that calculated from the crystallographic model. The radius of gyration measured by SAYS is about 5% larger and the maximum dimension in the distance distribution function about 12% larger than the corresponding value calculated from the crystal structure. A comparison of the experimental and calculated distance distribution functions suggests that the overall quaternary structure in the crystal and in solution are similar but that the homotetramer is less compact in solution than in the crystal.

Acta Biochimica Polonica, 49(2), 509-513 (2002)

DOI: 10.18388/abp.2002_3810
WWW: http://www.actabp.pl/pdf/2_2002/509.pdf   (Pobrane:  2021-01-10)


25.

Kozak M., Borek D., Janowski R., Jaskólski M.

Crystallization and preliminary crystallographic studies of five crystal forms of Escherichia Coli L-asparaginase II (Asp90Glu mutant) L-Asparaginase II from Escherichia coli with an Asp90Glu mutation in the active site has been crystallized in five polymorphic forms. Crystals of all polymorphs suitable for X-ray diffraction experiments were obtained by the vapour-diffusion method. Crystals of form I belong to the monoclinic system (space group C2), have unit-cell parameters a = 73.1, b = 133.1, c = 62.6 Angstrom, beta = 108.8 degrees and diffract to 2.27 degrees resolution. Three of the crystal forms are orthorhombic, with unit-cell parameters a = 225.4, b = 128.0, c = 62.6 Angstrom (form II, P2(1)2(1)2), a = 59.9, b = 71.2, c = 130.6 Angstrom (form III, primitive cell) and a = 73.8, b = 122.1, c = 124.2 Angstrom (form IV, P2(1)2(1)2(1) or P2(1)2(1)2); the crystals diffract to 2.33, 3.5 and 1.7 Angstrom, respectively. Polymorph V is trigonal, space group P3(1)21, with unit-cell parameters a = 123.1, c = 83.8 Angstrom; the crystals diffract to 2.65 Angstrom resolution.

Acta Crystallographica Section D-Biological Crystallography, 58, 130-132 (2002)

DOI: 10.1107/S0907444901016663   (Pobrane:  2020-10-23)


24.

Głowinkowski S., Kozak M., Nowaczyk G., Domka L., Jurga S.

Facultatis Chemiae Universitatis Studiorum Mickiewiczianae Posnaniensis Annales II, , 73-78 (2002)


ISSN: 1644-6364    (Pobrane:  2021-01-13)


23.

Domka L., Kozak M., Jurga S.

Facultatis Chemiae Universitatis Studiorum Mickiewiczianae Posnaniensis Annales II, , 65-72 (2002)


ISSN: 1644-6364    (Pobrane:  2021-01-13)


22.

Kozak M., Domka L., Skrzypczak A.

Adsorption of the quaternary ammonium salts on bentonite Sodium bentonite was subjected to the effect of two new homologue series of chlorides (alcoxymethyl) dimethyloctyloamonium chlorides and 3-alcoxymethyl-1-octylimidazole chlorides with the hydrophobic substituents of the same length. Morphology of the obtained modified bentonite was studied under scanning electron microscope [SEM] and the degree of adsorption of the ammonium salts was determined by two-phase titration. The results allowed an assessment of the influence of the length of the hydrophobic substituents and the site of the quaternary nitrogen atom on the adsorption of chlorides.

Physicochemical Problems of Mineral Processing, 36(1), 299-306 (2002)

WWW: http://www.minproc.pwr.wroc.pl/journal/pdf/2002/s299-306.pdf
ISSN: 1643-1049   (Pobrane:  2021-01-13)


21.

Domka L., Kozak M., Kozak A.

Chemistry for Agriculture, 3, 131-134 (2002)


20.

Kozak M.

Facultatis Chemiae Universitatis Studiorum Mickiewiczianae Posnaniensis Annales II, , 155-160 (2002)


ISSN: 1644-6364    (Pobrane:  2021-01-13)


19.

Marciniec B., Plotkowiak Z., Wachowski L., Kozak M., Popielarz-Brzezińska M.

Analytical study of beta-irradiated antibiotics in the solid state This paper reports results of the study on the influence of beta-irradiation on the physical and chemical properties of selected salts of beta-lactam antibiotics in solid state (sodium salt: ampicillin, azlocillin, benzylpenicillin, carbenicillin and piperacillin; potassium salt of benzylpenicillin, ampicillin anhydricum, ampicillin trihydricum, amoxicillin trihydricum and bacampicillin hydrochloride). The source of irradiation was a linear accelerator of electrons, and the irradiation effects were checked on the basis of the following: determination of mass, melting point and water contrent, and spectrophotometric (UV, IR) chromatographic and thermal (DTG, DSC) studies.

Journal of Thermal Analysis and Calorimetry, 68(2), 423-436 (2002)

DOI: 10.1023/A:1016027416521


18.

Domka L., Krysztafkiewicz A., Kozak M.

Silane modified fillers for reinforcing polymers Some white natural fillers (kaolin and talc) and synthetic mineral ones (precipitated silica, sodium-aluminium silicate, zinc silicate, calcium silicate) together with waste materials (cement dusts and post-fluor silicas) were subjected to surface modification and characterised. Various types of silane coupling agents (amino-, mercapto-, methacryloxy- and ureidosilanes) were used for surface modification. The modified fillers were mixed with butadiene-styrene rubber, polyurethane and PVC. Good physico-mechanical properties were obtained for PVC containing talcs and kaolins modified with methacryloxy- and ureidosilanes. The strength of polyurethanes was increased most by modification of the fillers with mercapto- and aminosilanes.

Polymers and Polymer Composites, 10(7), 541-552 (2002)

DOI: 10.1177/096739110201000706   (Pobrane:  2021-01-10)


17.

Foltynowicz Z., Jakubiak P., Judek Ł., Kozak M., Kuśmia S., Fojud Z., Domka L., Jurga S.

Polietylen modyfikowany mleczanem wapnia W pracy przedstawiono metodę otrzymywania polietylenu modyfikowanego mleczanem wapnia oraz pochodną krzemoorganiczną mleczanu wapnia. Stosowano różne ilości napełniacza. Uzyskane tworzywa biorozpraszalne poddano badaniom mechanicznym.

Mat. V Konferencji Naukowo-Technicznej "Polimery i Kompozyty Konstrukcyjne", , 61-65 (2002)


16.

Grzonka Z., Jankowska E., Kasprzykowski F., Kasprzykowska R., Łankiewicz L., Wiczk W., Wieczerzak E., Ciarkowski J., Drabik P., Janowski R., Kozak M., Jaskólski M., Grubb A.

Structural studies of cysteine proteases and their inhibitors Cysteine proteases (CPs) are responsible for many biochemical processes occurring in living organisms and they have been implicated in the development and progression of several diseases that involve abnormal protein turnover. The activity of CPs is regulated among others by their specific inhibitors: cystatins. The main aim of this review is to discuss the structure-activity relationships of cysteine proteases and cystatins, as well as of some synthetic inhibitors of cysteine proteases structurally based on the binding fragments of cystatins.

Acta Biochimica Polonica, 48(1), 1-20 (2001)

DOI: 10.18388/abp.2001_5108
WWW: http://www.actabp.pl/pdf/1_2001/1.pdf   (Pobrane:  2021-01-10)


15.

Foltynowicz Z., Wienskowski K., Kozak M., Domka L., Jurga S.

Commodity Science in Global Quality Perspectives. Products - Technology, Quality and Envir, , 353-358 (2001)


14.

Domka L., Domka L., Kozak M.

Utilisation of asbestos wastes The fibrous structure of asbestos, the ubiquitous material in the environment and exhibiting multiple applications, has proven to constitute hazards for human health. For this reason at present utilisation of asbestos has to be stopped, its resources have to be neutralised and reutilised in a safe way. In this paper we shall present studies on asbestos utilisation with the use of selected fluxes in order to alter its fibrous character but preserving fire resistance of the new material.

Physicochemical Problems of Mineral Processing, 35(1), 83-90 (2001)

WWW: http://www.minproc.pwr.wroc.pl/journal/pdf/2001/s83-90.pdf
ISSN: 1643-1049   (Pobrane:  2021-01-13)


13.

Nozirov F., Kozak M., Domka L., Jurga S.

NMR relaxation studies of polyhydroxybutyric acid (PHB) biodegradation by Escherichia Coli In the paper the biodegradation process of polyhydroxybutyric acid (PHB) copolymer, induced by Escherichia coli bacteria is monitored using nuclear magnetic resonance (NMR) and scanning electron microscopy (SEM).

Molecular Physics Reports, 33, 102-105 (2001)

WWW: http://www.ifmpan.poznan.pl/mol/
ISSN: 1505-1250   (Pobrane:  2021-01-07)


12.

Jaskólski M., Kozak M., Lubkowski J., Palm G., Wlodawer A.

Structures of two highly homologous bacterial L-asparaginases: a case of enantiomorphic space groups Quasi-enantiomorphic crystals of the Y25F mutant of Escherichia coli L-asparaginase and of the native Erwinia chrysanthemi L-asparaginase were obtained in the hexagonal space groups P6(5)22 and P6(1)22, respectively. The structures of these highly homologous enzymes were solved by molecular replacement and were refined with data extending to 2.2-2.5 Angstrom. These structures were compared with each other, as well as with other L-asparaginase structures previously observed with different crystal packing. It is concluded that the observed phenomenon, which is rare, was most likely to have arisen by chance.

Acta Crystallographica Section D-Biological Crystallography, 57, 369-377 (2001)

DOI: 10.1107/S0907444900020175


11.

Kozak M., Hayward B., Borek D., Bonthron D.T., Jaskólski M.

Expression, purification and preliminary crystallographic studies of human ketohexokinase Ketohexokinase (KHK; E.C. 2.7.1.3) catalyses the (reversible) phosphorylation of fructose to fructose-1-phosphate. KHK is the first enzyme in a specialized catabolic pathway metabolizing dietary fructose to the glycolytic intermediate glyceraldehyde-3-phosphate. Mutations inactivating KHK underlie the metabolic disorder essential fructosuria. The primary structure of KHK shows no significant homology to other mammalian hexokinases. It is most similar to prokaryotic ribokinases, but catalyses a distinct phosphorylation reaction. Recombinant human KHK has been crystallized in the orthorhombic form (space group P2(1)2(1)2 or P2(1)2(1)2(1)). Single crystals of this polymorph suitable for X-ray diffraction have been obtained by vapour diffusion using 2-propanol and MPD as precipitants (pH 7.5). The crystals have unit-cell parameters a = 93.4, b = 121.5, c = 108.4 Angstrom. Diffraction data were collected to 4.3 Angstrom resolution. The asymmetric unit contains four protein molecules.

Acta Crystallographica Section D-Biological Crystallography, 57(4), 586-588 (2001)

DOI: 10.1107/S0907444901001007   (Pobrane:  2020-10-23)


10.

Janowski R., Kozak M., Jankowska E., Grzonka Z., Grubb A., Abrahamson M., Jaskólski M.

Human cystatin C, an amyloidogenic protein, dimerizes through three-dimensional domain swapping The crystal structure of human cystatin C, a protein with amyloidogenic properties and a potent inhibitor of cysteine proteases, reveals how the protein refolds to produce very tight two-fold symmetric dimers while retaining the secondary structure of the monomeric form. The dimerization occurs through three-dimensional domain swapping, a mechanism for forming oligomeric proteins. The reconstituted monomer-like domains are similar to chicken cystatin except for one inhibitory loop that unfolds to form the 'open interface' of the dimer. The structure explains the tendency of human cystatin C to dimerize and suggests a mechanism for its aggregation in the brain arteries of elderly people with amyloid angiopathy, A more severe 'conformational disease' is associated with the L68Q mutant of human cystatin C, which causes massive amyloidosis, cerebral hemorrhage and death in young adults. The structure of the three-dimensional domain-swapped dimers shows how the L68Q mutation destabilizes the monomers and makes the partially unfolded intermediate less unstable. Higher aggregates may arise through the three-dimensional domain-swapping mechanism occurring in an open-ended fashion in which partially unfolded molecules are linked into infinite chains.

Nature Structural Biology, 8(4), 316-320 (2001)

DOI: 10.1038/86188


9.

Domka L., Skrzypczak A., Kozak M.

Czwartorzędowe sole amoniowe i obszary ich zastosowania, , 248-252 (2001)

WWW: http://www.itd.poznan.pl/pl/index.php?id=108
ISBN: 83-909723-7-9


8.

Kozak M., Jaskólski M., Rohm K.H.

Preliminary crystallographic studies of Y25F mutant of periplasmic Escherichia Coli L-asparaginase Periplasmic Escherichia coli L-asparaginase II with Y25F mutation in the active-site cavity has been obtained by recombinant techniques. The protein was crystallized in a new hexagonal form (P6(5)22). Single crystals of this polymorph, suitable for X-ray diffraction, were obtained by vapor diffusion using 2-methyl-2,4-pentanediol as precipitant (pH 4.8). The crystals are characterized by a = 81.0, c = 341.1 Angstrom and diffract to 2.45 Angstrom resolution. The asymmetric unit contains two protein molecules arranged into an AB dimer. The physiologically relevant ABA'B' homotetramer is generated by the action of the crystallographic a-fold axis along [1, -1, 0]. Kinetic studies show that the loss of the phenolic hydroxyl group at position 25 brought about by the replacement of Y with F strongly impairs k(cat) without significantly affecting K-m.

Acta Biochimica Polonica, 47(3), 807-814 (2000)

DOI: 10.18388/abp.2000_3998
WWW: http://www.actabp.pl/pdf/3_2000/807.pdf   (Pobrane:  2021-01-10)


7.

Kozak M., Jaskólski M.

Crystallization and preliminary crystallographic studies of a new crystal form of Escherichia Coli L-asparaginase II (Ser58Ala mutant) Periplasmic Escherichia coli L-asparaginase II with an Ser58Ala mutation in the active-site cavity has been crystallized in a new orthorhombic form (space group P2(1)2(1)2). Crystals of this polymorph suitable for X-ray diffraction have been obtained by vapour diffusion using two sets of conditions: (i) 1% agarose gel using MPD as precipitant (pH 4.8) and (ii) liquid droplets using PEG-MME 550 (pH 9.0). The crystals grown in agarose gel are characterized by unit-cell parameters a = 226.9, b = 128.4, c = 61.9 Angstrom and diffract to 2.3 Angstrom resolution. The asymmetric unit contains six protein molecules arranged into one pseudo-222-symmetric homotetramer and an active-site competent dimer from which another homotetramer is generated by crystallographic symmetry.

Acta Crystallographica Section D-Biological Crystallography, 56(4), 509-511 (2000)

DOI: 10.1107/S0907444900000081   (Pobrane:  2020-10-23)


6.

Domka L., Kozak M.

Quarry-Laboratory-Monument, 1, 287-292 (2000)


ISBN: 88-7830-311-9   (Pobrane:  2021-01-13)


5.

Kozak M., Jankowska E., Janowski R., Grzonka Z., Grubb A., Fernandez M.A., Abrahamson M. Jaskólski M.

Expression of a selenomethionyl derivative and preliminary crystallographic studies of human cystatin C Human cystatin C, a protein with amyloidogenic properties and a potent inhibitor of papain-like mammalian proteases, has been produced in its full-length form by recombinant techniques and crystallized in two polymorphic forms: cubic and tetragonal. A selenomethionyl derivative of the protein, obtained by Escherichia coli expression and with complete Met-->Se-Met substitution confirmed by mass spectrometry, amino-acid analysis and X-ray absorption spectra, was crystallized in the cubic form. A truncated variant of the protein, lacking ten N-terminal residues, has also been crystallized. The crystals of this variant are tetragonal and, like the two polymorphs of the full-length protein, contain multiple copies of the molecule in the asymmetric unit, suggesting oligomerization of the protein.

Acta Crystallographica Section D-Biological Crystallography, 55(11), 1939-1942 (1999)

DOI: 10.1107/S090744499901121X


4.

Czaplewski C., Grzonka Z., Jaskólski M., Kasprzykowski F., Kozak M., Politowska E., Ciarkowski J.

Binding modes of a new epoxysuccinyl-peptide inhibitor of cysteine proteases. Where and how do cysteine proteases express their selectivity? Papain from Carica papaya, an easily available cysteine protease, is the best-studied representative of this family of enzymes. The three dimensional structure of papain is very similar to that of other cysteine proteases of either plant (actinidin, caricain, papaya protease IV) or animal (cathepsins B, K, L, H) origin. As abnormalities in the activities of mammalian cysteine proteases accompany a variety of diseases, there has been a long-lasting interest in the development of potent and selective inhibitors for these enzymes. A covalent inhibitor of cysteine proteases, designed as a combination of epoxysuccinyl and peptide moieties, has been modeled in the catalytic pocket of papain. A number of its configurations have been generated and relaxed by constrained simulated annealing-molecular dynamics in water. A clear conformational variability of this inhibitor is discussed in the context of a conspicuous conformational diversity observed earlier in several solid-state structures of other complexes between cysteine proteases and covalent inhibitors. The catalytic pockets S2 and even more so S3, as defined by the pioneering studies on the papain-ZPACK, papain-E64c and papain-leupeptin complexes, appear elusive in view of the evident flexibility of the present inhibitor and in confrontation with the obvious conformational scatter seen in other examples. This predicts limited chances for the development of selective structure-based inhibitors of thiol proteases, designed to exploit the minute differences in the catalytic pockets of various members of this family. A simultaneous comparison of the three published proenzyme structures suggests the enzyme's prosegment binding loop-prosegment interface as a new potential target for selective inhibitors of papain-related thiol proteases.
(C) 1999 Elsevier Science B.V. All rights reserved.

Biochimica et Biophysica Acta - Protein Structure and Molecular Enzymology, 1431(2), 290-305 (1999)

DOI: 10.1016/S0167-4838(99)00053-9   (Pobrane:  2020-10-21)


3.

Kozak M., Jaskólski M.

Crystallography and Drug Design, , 71-76 (1999)


2.

Schluckebier G., Kozak M., Bleimling N., Weinhold E., Saenger W.

Differential binding of S-adenosylmethionine S-adenosylhomocysteine and Sinefungin to the adenine-specific DNA methyltransferase M.TaqI The crystal structures of the binary complexes of the DNA methyltransferase M.TaqI with the inhibitor Sinefungin and the reaction product S-adenosyl-L-homocysteine were determined, both at 2.6 Angstrom, resolution. Structural comparison of these binary complexes with the complex formed by M.TaqI and the cofactor S-adenosyl-L-methionine suggests that the key element for molecular recognition of these ligands is the binding of their adenosine part in a pocket, and discrimination between cofactor, reaction product and inhibitor is mediated by different conformations of these molecules; the methionine part of S-adenosyl-L-methionine is located in the binding cleft, whereas the amino acid moieties of Sinefungin and S-adenosyl-L-homocysteine are in a different orientation and interact with the active site amino acid residues (NPPY.108)-N-105 Dissociation constants for the complexes of M.TaqI with the three ligands were determined spectrofluorometrically . Sinefungin binds more strongly than S-adenosyl-L-homocysteine or S-adenosyl-L-methionine, with K-D=0.34 mu M, 2.4 mu M and 2.0 mu M, respectively.
(C) 1997 Academic Press Limited

Journal of Molecular Biology, 265(1), 56-67 (1997)

DOI: 10.1006/jmbi.1996.0711   (Pobrane:  2020-10-21)


1.

Kozak M., Kozian E., Grzonka Z., Jaskólski M.

Crystallization and preliminary crystallographic studies of a new crystal form of papain from Carica papaya A new crystal form of papain from the latex of Carica papaya, complexed with an inhibitor (Z-Arg-Leu-Val-Gly-CHN2) was obtained by the vapor-diffusion method using a methanol/ethanol mixture as a precipitant. The slat-like crystals are monoclinic, space group P2(1), with unit cell parameters a = 42.6 Angstrom, b = 49.8 Angstrom, c = 50.5 Angstrom, beta = 111.9 degrees, and contain one molecule in the asymmetric unit. The crystals are stable in the X-ray beam and diffract beyond 1.8 Angstrom. A molecular model has been placed in the unit cell by molecular replacement.

Acta Biochimica Polonica, 44(3), 601-606 (1997)

WWW: http://www.actabp.pl/pdf/3_1997/601.pdf


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