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1
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Structural Changes of DPPC Bilayers Induced by Gemini Surfactant

100%
Kida W., Kozak M.
Acta Physica Polonica A
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2012
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vol. 121
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issue 4
893-898
EN
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_Cl_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
2
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Low Resolution Structure of RAR1-GST-Tag Fusion Protein in Solution

81%
Taube M., Jarmołowski A., Kozak M.
Acta Physica Polonica A
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2010
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vol. 117
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issue 2
307-310
EN
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.
3
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SAXS Study of Influence of Gemini Surfactant, 1,1'-(1,4-butanediyl)bis 3-cyclododecyloxymethylimidazolium di-chloride, on the Fully Hydrated DMPC

81%
Pietralik Z., Taube M., Skrzypczak A., Kozak M.
Acta Physica Polonica A
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2010
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vol. 117
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issue 2
311-314
EN
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-alkylo-xyme-thyli-mida-zolium 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.
4
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The SAXS and Rheological Studies of HEWL Amyloid Formation

81%
Szymańska A., Ślósarek G., Hornowski T., Kozak M.
Acta Physica Polonica A
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2008
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vol. 114
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issue 2
447-454
EN
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.
5
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Spectroscopic Studies of Poly(ε-Caprolactone)/Sodium Montmorillonite Nanocomposites

81%
Krzaczkowska J., Fojud Z., Kozak M., Jurga S.
Acta Physica Polonica A
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2005
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vol. 108
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issue 1
187-196
EN
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(ε-caprolactone)/sodium montmorillonite nanocomposites. We observed a correlation between the concentration of poly(ε-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(ε-caprolactone) intercalation into a clay structure. ^{27}Al 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(ε-caprolactone) chains in the nanocomposites depend on the concentration of poly(ε-caprolactone).
6
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Structure and Morphology of Gold Nanoparticles in Solution Studied by TEM, SAXS and UV-Vis

81%
Murawska M., Skrzypczak A., Kozak M.
Acta Physica Polonica A
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2012
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vol. 121
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issue 4
888-892
EN
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.
7
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Structural Studies of Selected DSPC-Surfactant Model Systems of Biological Membranes

61%
Szpotkowski K., Kozak M., Kozak A., Zieliński R., Wieczorek D., Jurga S.
Acta Physica Polonica A
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2009
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vol. 115
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issue 2
561-564
EN
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 CH_2 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.
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