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1
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Bound Water Structure on the Surfaces of Usnea antarctica as Observed by NMR and Sorption Isotherm

100%
Harańczyk H., Pietrzyk A., Leja A., Olech M.
Acta Physica Polonica A
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2006
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vol. 109
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issue 3
411-416
EN
Hydration courses and proton free induction decays are recorded at 30 MHz for Usnea antarctica thalli hydrated from gaseous phase. NMR data combined with gravimetry allow one to distinguish two fractions of tightly bound water, and loosely bound/free water pool. No water fraction "sealed" in thallus structures is present in U. antarctica.
2
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The Effect of Water Accessible Paramagnetic Ions on Subcellular Structures Formed in Developing Wheat Photosynthetic Membranes as Observed by NMR and by Sorption Isotherm

100%
Harańczyk H., Leja A., Strzałka K.
Acta Physica Polonica A
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2006
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vol. 109
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issue 3
389-398
EN
The rehydration from the gaseous phase of the developing native or EDTA-washed from unbound and loosely bound paramagnetic ions wheat thylakoid membrane lyophilizate was investigated using hydration kinetics, sorption isotherm, and high power proton relaxometry. Hydration time courses are single exponential for all target humidities. The sorption isotherm is well fitted by the Dent model, with the mass of water saturating primary binding sites equal toΔ M/m_ 0=0.024 and 0.017 for native and EDTA-washed membranes, respectively. Proton free induction decays distinguish: (i) a Gaussian component, S_0, coming from protons of solid matrix of lyophilizate; (ii) a Gaussian component, S_1, from water bound to the primary water binding sites in proximity of water accessible paramagnetic ions; (iii) an exponentially decaying contribution, $L_1$, from water tightly bound to lyophilizate surface; and (iv) exponentially decaying loosely bound water pool, L_2. Sorption isotherm fitted to NMR data shows a significant contribution of water "sealed" in membrane structures (Δ M_s/m_0=0.052 for native and 0.061 for EDTA-washed developing membranes, respectively).
3
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Impact of Vanadium(IV)-Oxy Acetylacetonate and Vanadium(III) Acetylacetonatel on the DPPC Liposome Membranes: EPR Studies

80%
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.
4
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Impact of Plesiomonas Shigelloides Strain CNCTC 144/92 Lipopolysaccharide on DPPC Liposome Membranes: EPR Method

80%
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}.
5
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A virtual instrumentation based protocol for the automated implementation of the inner field compensation method

41%
Mereuta L., Luchian T.
Open Physics
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2006
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vol. 4
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issue 3
405-416
EN
One influential parameter which mediates interactions between many types of molecules and biological membranes stems from the lumped contributions of the transmembrane potential, dipole potential and the difference in the surface potentials on both sides of a membrane. With relevance to cell physiology, such electrical features of a biomembrane are prone to undergoing changes as a result of interactions with the aqueous surrounding. Among the most useful tools devoted to exploring changes of electrical parameters of a lipid membrane induced by certain extracellular ions, lipid composition, and embedded membrane peptides and proteins, are spectroscopic imaging and the inner field compensation (IFC) method. In this work we layout the principles of a fully computerized version of the IFC method, which makes it more readily available to users. As a direct application, we deployed this improved version of the IFC method to time-resolve changes induced by alamethicin monomers upon membrane dipole potential, following their aggregation within an artificial lipid membrane. Intriguingly, even prior crossing the membrane core, the membrane-bound alamethicin monomers are shown to significantly increase the dipole potential of the monolayer they reside in. Such data further emphasize the yet less-explored interplay between membrane-based protein and peptides, and the membrane dipole potential.
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