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

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.