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The efficiency of alpha-tocopherol as a 7-etoxycumarine deethylase protector in rat liver microsomes damaged by phospholipase A2 at various levels of vitamin E was studied. No selective damage of cytochrome P-450 isoforms possessing a catalytic activity towards 7-etoxycumarine under vitamin E deficiency was observed. Phospholipase A2 decreased the deethylase activity of cytochrome P-450, the efficiency of the damaging action being dependent on vitamin E content in the liver. Exogenous alpha-tocopherol exerts an antiphospholipase effect and protects 7-etoxycumarine deethylase; the protective action is inversely proportional to vitamin E level in the liver. Under normal conditions the damaging effect of phospholipase A2 on cytochrome P-450 is mainly provided for by lysophospholipids, while under vitamin E deficiency both lysophospholipids and free fatty acids exert a damaging action. A possible mechanism of the stabilizing effect of alpha-tocopherol may consist in the interaction of the chromanol nucleus in the vitamin E molecyule both with lysophospholipids and with free fatty acids.

UV spectrophotometry and high-resolution NMR spectrometry have demonstrated the formation of the complexes of ionol and fatty acids. This formation occurs as a result of the two types of interactions: 1/hydrogen bond formation between ionol OH-group and the carboxylic group of a fatty acid; 2/van der Waals interactions between the hydrogen chain of a fatty acid and tret -butyl groups of ionol. The latter interaction becomes more powerful with increase in fatty acid unsaturation. The molecular structure of the complexes of ionol with fatty acids is suggested.

Using ESR-spin probes and 1H-NMR-spectroscopy methods the effect of alpha-tocopherol on liposome microviscosity has been studied. alpha-Tocopherol has been shown to remove the chaotropic action of free fatty acids on bilayer. The stabilization effect found has a common nature and does not depend on the chemical structure of the phopsholipid functional polar groups, the unsaturation degree of free fatty acids as well as fatty acids residua entering into phospholipid composition. Analog of alpha-tocopherol without phytol chain 2,2,5,7,8-penthamethyl-6-oxychroman does not show the stabilizing effect on the microviscosity of lipid bilayer under the action of free fatty acids. It indicates that both chromanol nucleus and phytol chain of alpha-tocopherol molecule are necessary for stabilizing action. The data obtained allow to suppose that the interaction of alpha-tocopherol with free fatty acids may be one of the molecular mechanisms of lipid bilayer microvicosity stabilization.

Using fluorescent probes it has been shown that free fatty acids cause depolarization of synaptosomes isolated from the rat brain. At the same time free fatty acids stimulated 45Ca2+ transport into synaptosomes. It has been demonstrated that synaptosomes isolated from the brain of E-deficient rats were more sensitive to the action of free fatty acids. Depolarization of synaptosomes isolated from the brain of both control and E-deficient rats were reduced by the addition of exogenous alpha-tocopherol.

Using 1H-NMR high resolution spectroscopy it was demonstrated that alpha-tocopherol modifies the character of phase transition in the membrane lipid bilayer. Injection of 5 mol% tocopherol into the lipid bilayer from dipalmitoylphosphatidylcholine (DPPC) decreased the temperature and increased the width of the phase transition. Similar action was produced by injection into the bilayer from DPPC of 15-20 mol% linoleic acid. Injection of an equimolar amount of alpha-tocopherol into the bilayer from DPPC predestabilized by linoleic acid exerted a stabilizing action, the mode of phase transition being similar to that observed for pure DPPC. It is assumed that the stabilizing effect of alpha-tocopherol in question is a mechanism via which alpha-tocopherol protects the membrane from the damage-inducing action of free fatty acids.

Stereoconfiguration of alpha-tocopherol-linoleic acid complex was studied using high resolution IH-NMR-spectroscopy. The addition of a fatty acid (linoleate) to alpha-tocopherol solution in CDCl3 resulted in the broadening of IH-NMR lines for OH- and phe-CH3-alpha-tocopherol groups. No changes in chemical shift values of IH-NMR lines for linoleic acid were observed after the addition of alpha-tocopherol to linoleic acid solution in CDCl3. It is concluded that in the complexes formed linoleic acid is located in the phenolic ring plane of alpha-tocopherol. The conclusion is supported by the data obtained on molecular models.

Using the high resolution 1H-NMR spectroscopy and spin-probes the influence of alpha-tocopherol on lipid bilayer microviscosity has been studied. It has been established that alpha-tocopherol shows the cholesterol-like action on the physical state of lipid bilayer: alpha-tocopherol increase microviscosity of unsaturated bilayers and decrease microviscosity of saturated bilayers. The character of alpha-tocopherol action is determined by the fatty acidic lipid composition but does not depend on the polar group structure of phospholipid molecule as cholesterol-like action of alpha-tocopherol is found itself in liposomes prepared both from phosphatidylcholine and phosphatidylethanolamine. Analog of alpha-tocopherol without phytol chain 2,2,5,7,8-penthamethyl-6-oxychroman does not show the cholesterol-like action as it is not able to disorder the saturated bilayers.

Changes in potential-dependent fluorescence were studied, using fluorescent probe di-S-C3-(5), in synaptosome suspensions exposed to phospholipase A2, alpha-tocopherol and its derivatives. Phospholipase A2 increased potential-dependent fluorescence, i.e. depolarization of synaptosome membranes. The damaging phospholipase A2 effect was prevented and/or abolished by alpha-tocopherol added to synaptosome suspensions before and after phospholipase A2. Alpha-tocopherol derivatives (2,2,5,7,8-pentamethyl-6-hydroxychromane and alpha-tocopheryl-acetate as well as 4-methyl-2,6-di-tert-butylphenol) failed to exert a protective effect on synaptosome membranes modified by phospholipase A2. It is suggested that alpha-tocopherol effect is determined by its interaction with fatty acids, with 6-hydroxy groups of chromanol nucleus and phytol chain being essential for the complex formation.

Introduction of factors D1 isolated from the culture fluids of B. cereus and Ps. carboxydoflava into cytoplasmic membranes of M. lysodeikticus resulted in a higher microviscosity of the lipid phase. Factor d1 changes the ion permeability of an artificial bilayer membrane as well as reduces the content of free water in the bacterial paste. It is assumed that registered structural changes may result from the interaction of the factor molecules with membrane lipids and be the main reason of changes in the functioning of membrane-bound enzymes and dehydration of the microbial cell as well.

High-resolution 1H-nmr spectroscopy and UV spectrophotometry have demonstrated the formation of alpha-tocopherol and phosphatide acid complexes. The complex formation occurs at the expense of two types of interactions: polar interaction of the OH-group of alpha-tocopherol with a keto group of phosphatide acid and hydrophobic interaction of the methyl groups of the chroman nucleus of alpha-tocopherol with cis-unsaturated double bonds of the accyls of phosphatide acid. The role of such complexes in the mechanisms of biomembrane stabilization for preventing the damaging action of phospholipases is discussed.

The study of 6 E. coli strains differing in their capacity for survival in the air has revealed that the physicochemical characteristics of lipids in microbial cells, such as antioxidizing activity, the concentration of peroxidation products, the content of lipids and their capacity for oxidation, are interrelated, which confirms the existence of the system regulating the peroxidation of lipids in prokaryotic cells, similar to the system regulating lipid peroxidation in eukaryotic cells. The capacity of cells for survival in the air has been shown to depend on the physicochemical state of lipids in cellular membranes.