[Changes in charge density of cholesterol-enriched erythrocyte membranes]

Application of potentiometric titration and fluorescent probes showed that density of negative charges of erythrocyte membranes decreases with their cholesterol enrichment by different methods (keeping animals on a diet causing hypercholesterinemia, application of cholesterol-lecithin liposomes in experiments in vitro). These effects are largely due to cholesterol-induced in accessibility for titration of a definite amount of carboxylic, imidazole and secondary phosphate groups of the membrane components and to an increase in the number of titrated epsilon-NH2-groups resulted from the weakening of electrostatic interaction of the membrane charges. The found shifts of pK groups dissociating in the region of pH neutral values and shifts in the fluorescence peaks of a positively charged probe of astraphloxin towards the spectral short-wave region with cholesterol enrichment of the membranes evidence for changes in microenvironment of the studied polar groups. A separate quantitative expression of the cholesterol-induced effects of viscosity increase and a density decrease of negative charges of membranes affecting the processes of astraphloxin binding is shown to be possible.