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The fusing capacity of lipid membranes of a synthetic 23-member peptide was studied. This hydrophobic peptide represents an analog of a predicted functional site ("fusion peptide") of the GP2 envelope protein of the Lassa virus (family Arenaviridae). Fusion of small monolayer liposomes was detected by the method of resonance energy transfer between the fluorescent derivatives of the lipid, NBD-PE (donor) and Rd-PE (acceptor). Using this peptide, the pH-dependent fusing activity was found in liposomes having different phospholipid composition. The rate and efficiency of liposome fusion increased with a decrease in pH and the lipid/peptide ratio as well as with a temperature increase. The increase in the ionic strength and Ca2+ concentration in the reaction mixture led to the inhibition of the peptide-induced fusion of liposomes. Neither the phospholipid charge, nor the transmembrane proton gradient of liposomes had any appreciable effect on the kinetics of the peptide-induced fusion. Neutralization of the medium in the course of the fusion reaction sharply decelerated, whereas repeated acidification activated this process. This finding suggests that peptide protonation plays a role in fusion reactions. It was suggested that acidification causes conformational changes in the peptide structure, thus activating the peptide-induced fusion of liposomes. The fusing capacity of the predicted Lassa virus fusion peptide is similar to that of viruses characterized by a pH-dependent step at the initial stages of the viral infection.

It has been shown that low-density plasma lipoproteins in patients with ischemic heart disease and hypertriglyceridemia are heavier in density, smaller in size, more negatively charged and more inclined to peroxide modification and aggregation than in healthy persons. The protein in the composition of such lipoproteins deviates towards the water phase, which may result in the masking of the domen, recognized by the BE-receptor and may lead to hyperlipidemia of a retaining character.

A new method of EPR-spectroscopy--the recombination of free radicals appearing as a result of indirect radiolysis of biological molecules after a low temperature irradiation--is applied to the study of molecular dynamics of phosphatidylcholine dimyristoyl in mass and in the structure of liposomes above and below the transition temperature. It was shown, that the mobility of lipid molecules in crystalline liposomes is higher than in the structure of liquid-crystalline liposomes. The addition of cholesterol in liposome membranes decreases the lateral molecular motion of lipids in crystalline and liquid-crystalline state, in the latter case the effect of cholesterol addition is more pronounced. The activation energy for the displacement of the fragments of lipid molecules and the lipid molecule as a whole was estimated, and it was shown, that lipid matrix possesses a high degree of heterogeneity.

A decay of fluorescence probe 1-anilino-8-naphtalene sulfonate (ANS) sorbed on low density lipoproteins (LDL) surface obtained from human plasma was described. It was demonstrated that on the LDL surface the ANS probe is allocated among two pools of molecules with the time of fluorescence decay 4-7 ns and 12-16 ns. One may conclude that 75-90% of the probe is connected with lipid LDL matrix.

The study has shown that the ratio of elements in the secondary structure of LDL protein from patients with the coronary heart disease from health subjects is similar. However LDL protein is displaced by 0.5 nm towards the water phase in patients with CHD comparing with healthy subjects. It is likely that such differences are a result of the lower stability of LDL protein in CHD. It is supposed that the damage of lipoprotein particles (premodification) in CHD becomes atherogenic in the vessel wall after the action of additional factors.

Binding of Central Asia cobra venom cytotoxin with model membranes prepared from mixture of dilauroylphosphatidylcholine and cardiolipin, having different values of the molar ratio of the latter in the buffer medium with low (0.01 M NaCl) and high (2.0 M NaCl) ionic strength was studied using fluorescent probe ANS (1-anilinonaphthalene-8-sulfonate). The results obtained show that the binding of cytotoxin molecule with the membrane depends not only upon its surface charge but on lipid composition as well, which determines the structural organization of the membrane.

Fluorescent probe I-aniline-8-naphthalene sulfonate was used to evaluate the LDL surface potential values in patients with coronary artery atherosclerosis. The more negative charge was found on the LDL surface in patients with atherosclerosis of three coronary arteries as compared with that of healthy persons.