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Impact of Vanadium(IV)-Oxy Acetylacetonate and Vanadium(III) Acetylacetonatel on the DPPC Liposome Membranes: EPR Studies

100%
Man D., Mrówka I., Wójcik A., Pytel B.
Acta Physica Polonica A
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2017
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vol. 132
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issue 1
52-56
EN
The effect of vanadium (IV)-oxy acetylacetonate (V4) and vanadium(III) acetylacetonate (V3) on the liposome membranes formed of synthetic lecithin (DPPC) was presented in this paper. Liposomes were formed during the sonication of DPPC lecithin in an aqueous medium. The concentration of the vanadium compounds changed in the range of 0% to 2.4% in molar ratio to the lecithin. The EPR technique made use of three spin probes penetrating the different areas of the membrane (as follows: TEMPO, 16-DOXYL stearic acid methyl ester, stearic acid 5-DOXYL methyl ester). TEMPO probe penetrates the interphase water-lipid (partition parameter F), the probe 16-DOXYL locates in the middle of the lipid bilayer (rotational correlation time τ), the probe 5-DOXYL gives a picture of membrane fluidity (the order parameter) just below the polar head groups. The results of our research showed the following conclusions. The change of membrane fluidity, as a function of admixture concentration, was dependent on the type of additives. TEMPO probe recorded an increase in liquidity interphase water-lipid for both admixtures: V3 and V4. 16-DOXYL probe indicated that the admixture V3 increases the fluidity in the center of the lipid bilayer. Admixture V4 significantly less impacted on the change of the membrane middle. The 5-DOXYL probe did not influence on the membrane surface portion, there were not observed significant changes under the impact of admixtures. V3 showed stronger impact on membrane fluidity.
2
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Impact of Plesiomonas Shigelloides Strain CNCTC 144/92 Lipopolysaccharide on DPPC Liposome Membranes: EPR Method

100%
Man D., Pytel B., Pisarek I.
Acta Physica Polonica A
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2017
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vol. 132
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issue 1
77-80
EN
Membrane fluidity measurements were performed for synthetic DPPC liposomes sonicated in aqueous solution and doped by Plesiomonas shigelloides strain CNCTC 144/92 (serotype O74:H5) lipopolysaccharide (LPS) extracted from the phenol (LPS_{PhOH}) and water (LPS_{H₂O}) phases. Concentrations of LPS in relation to DPPC ranged from 0 to 1.4% (molar ratio). The EPR spin probe method was used to describe physicochemical properties of different regions of the lipid bilayer. Since TEMPO spin probe dissolves both in the hydrophobic region of the membrane and in an aquatic environment it is possible to determine the spectroscopic partition parameter F, indicating the changes that occur in the water-lipid interface. The 16-DOXYL probe distributed in the middle of the lipid bilayer makes it possible to obtain the rotational correlation time τ parameter, which provides information about fluidity changes in the liposome membrane. Here we report that increasing concentrations (mainly in the range of 0.4-0.8%) of investigated LPS_{PhOH} and LPS_{H₂O} significantly influence spectroscopic parameters (F and τ). The surface area of the DPPC liposomes membranes was affected predominantly by LPS_{H₂O} while the lipid bilayer was most influenced by LPS_{PhOH}.
3
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Effect of Neutron Irradiation on the EPR Spectra of CuGeO_{3}

88%
Mosiniewicz-Szablewska E., Gładczuk L., Dąbkowska H., Pytel B., Szymczak H.
Acta Physica Polonica A
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2000
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vol. 97
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issue 5
897-900
EN
The influence of neutron irradiation on the electron paramagnetic resonance spectra of the spin-Peierls compound CuGeO_{3} was investigated in the wide temperature range 2-300 K. It was found that the irradiation induced appreciable changes in the EPR signal intensity, resonance line width and g-factor of this material. It was also shown that the irradiation leads to a decrease in the spin-Peierls transition temperature. For higher irradiation doses, an antiferromagnetically ordered phase can be observed at lower temperatures. This phase coexists with the spin-Peierls phase. The observed decrease in the spin-Peierls transition temperature after irradiation may be associated with some changes in topological and chemical short-range order or with the transmutation of the fraction of ^{63}Cu in the ^{63}Cu(n,α)^{60}Co reaction.
4
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The Influence of Fast Neutron Irradiation on the Magnetostriction of Ceramic YBa_2Cu_3O_{7-δ} Sample

88%
Nabiałek A., Vasiliev S., Pytel B., Chabanenko V., Piechota S.
Acta Physica Polonica A
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2004
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vol. 106
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issue 5
739-744
EN
We investigated the magnetostriction of ceramic YBa_2Cu_3O_{7-δ} sample both before and after fast neutron irradiation with the fluency of 7.55×10^{17} n/cm^2 and energy of above 0.5 MeV. We have found that after irradiation the widths of both transverse and longitudinal magnetostriction hysteresis loops at a given temperature and at a given external magnetic field increased several times. At 4.2 K and in 10 tesla the widths of the magnetostriction hysteresis loop of the irradiated sample are of an order of 10^{-5}. The results can be understood in the framework of the model of the magnetostriction induced by the pinning forces, assuming the stress in the sample to be induced mainly by the intragrain screening currents.
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