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The Influence of Natural and Model Forms of Humic Acids on the Dynamic Parameters of Model Membranes

Pisarek I., Pytel B., Filipiak A., Engel G., Olchawa R., Man D., Najwer K.

Ecological Chemistry and Engineering. S

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2016

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Vol. 23, nr 4

695--708

EN

In this paper the influence of humic acid concentrations extracted from Histosols (HA-A) and their model forms (HA-B) separated from humic substances commercially produced by Carl Roth GmbH + Co.KG on the dynamic properties of liposome membranes was determined. Differences in the quality of the humic acids (HA-A and HA-B) were determined by the 1HNMR and FTIR methods. Liposomes from the sonication of egg yolk lecithin (EYL) in an aqueous solution and synthetic Dipalmitoylphosphatidylcholine (DPPC) were used. Fluidity of liposome membranes was determined by the EPR technique with spin probes (TEMPO, 16DOIXYL). The electrical parameters of membranes were found using a Keithley 6517 electrometer. Our study showed significant differences in the influence of HA-A and HA-B on the membranes. In the bilayer membranes of the liposomes of HA-A admixture there was slightly more stiffening of the interior of the membrane in comparison to HA-B. A similar effect was observed in the surface layer of the liposome membranes. This difference is particularly evident for DPPC liposomes, however, the EYL liposomes admixture with HA-B slightly increased the fluidity of the surface layer. Electrical study confirmed this effect. The study shows that natural and model forms of humic acids differ in their effects on the activity of tested membrane models. The strong differences in the interaction of HA-A and HA-B on parameter F in DPPC liposomes can be result from the transport of humic acids connected to the metal ions inside the membranes (xenobiotics present in the environment).

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The dynamics of the surface layer of lipid membranes doped by vanadium complex : computer modeling and EPR studies

Olchawa R., Man D., Pytel B.

Nukleonika

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2015

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Vol. 60, No. 3, part 1

395--398

EN

Penetration of the liposome membranes doped with vanadium complex formed in the liquid-crystalline phase from egg yolk lecithin (EYL) by the TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) spin probes has been investigated. The penetration process was followed by 360 hours at 24◦C, using the electron spin resonance (EPR) method. The spectroscopic parameter of the partition (F) of this probe indicated that a maximum rigidity of the membrane was at 3% concentration of the vanadium complex. Computer simulations showed that the increase in the rigidity of the membrane corresponds to the closure of gaps in the surface layer of the membrane, and indicates the essential role of the membrane surface in transport processes.

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Impact of humic acids on EYL liposome membranes : ESR method

Pytel B., Filipiak A., Pisarek I., Olchawa R., Man D.

Nukleonika

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2015

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Vol. 60, No. 3, part 1

455--459

EN

In this paper, the effects of model (commercial) and natural (extracted from peat) humic substances on the membrane of liposomes formed with egg yolk lecithin (EYL) are presented. In our research, mass concentrations of fulvic and humic acids were used, which in relation to lecithin varied from 0% to 13%. To study membrane fluidity, electron spin resonance (EPR) was used with two spin probes, penetrating various regions of the lipid bilayer. The effects of model and natural humic substances (humic acids – HAs and fulvic acids – FAs) on the lipid membrane in different regions were researched: the lipid-water interphase, and in the middle of the lipid bilayer. It was shown that FA and HA impact the fluidity of liposome membranes in different ways. Increased mass concentrations of HAs decreased membrane fluidity in both acids: extracted from peat and the model. However, increased mass concentration of FAs extracted from peat, decreased membrane fluidity in the surface region, at the same time stiffening the central part of the bilayer. Increasing the concentration of FAs extracted from peat had the opposite effect when compared to model FA. This effect may be related to the complexation of xenobiotics present in the soil environment and their impact on biological membranes.

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The influence of selected amino acids on the dynamic properties of the liposome membranes : ESR study

Man D., Broda M., Buczek A., Kawecka A., Siodłak D.

Nukleonika

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2013

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Vol. 58, No. 3

443--446

EN

In this work the changes in the fluidity of liposome membranes caused by alanine and butyrine derivatives (Ac-Ala-NMe2 and Ac-Abu-NMe2) were investigated. Liposomes were obtained in the process of egg yolk lecithin (EYL) sonication. The concentration of the admixture in the proportion to EYL varied from 0 to 25% mole. The electron spin resonance (ESR) spectroscopy was used with two different spins probes. Each spin probe penetrates different regions of liposome membrane. The TEMPO probe occurs both in the hydrophobic part of the membrane and in the water environment what allows to determine the spectroscopic parameter F of division of this probe into the membrane and its water surrounding. DOXYL is localized in the central part of the lipid bilayer and is used to obtain the spectroscopic parameter τ – rotation correlation time – whose value gives information about fluidity changes in the middle of the lipid bilayer. The study indicated that the tested as admixtures N-methylated model peptides significantly changed the fluidity of liposome membranes. The dynamic of this process depends both on amino acids derivative and on the membrane region. Both studied compounds increased the fluidity of the surface layer of liposome membrane. At the same time, butyrine derivative caused the stiffening of the middle part of liposome bilayer, but alanine derivative slightly increased the fluidity of this region.

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The impact of humic substances on the liposome structures : ESR method

Man D., Pisarek I., Braczkowski M.

Nukleonika

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2013

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Vol. 58, No. 3

439--442

EN

In this paper the changes of membrane fluidity of liposome with additions of humic substances (humic and fulvic acids) were examined. Liposome were done by the sonication of lecithin EYL. Concentrations of humic substances in attitude to EYL varied between 0–10% of weight. The technique of electron spin resonance (ESR) were used for the examination followed by three spin probes with a variety placement of the membrane located. TEMPO probe melted in the hydrophobic membrane and in the aquatic solution which allowed to determine the spectroscopic partition parameter (F), indicating the changes that occur in water-lipid interphase. Probe 5-DOXYL placed directly under the heads of polar lipids and the order parameter measuring by the TII showed the changing of membrane fluidity at surface area. 16-DOXYL probe penetrated the middle of the lipid bilayer membrane and allowed to determine the rotational correlation time τ parameter, which gives us information about changing of the liquidity lipid bilayer. Studies showed that the tested humic substances significantly changed the membrane fluidity of liposome. The dynamics of this process depends on both: the fraction of humic substances and its quality and quantity as well as the placement area of the membrane.