[Physicochemical mechanisms of the action of gramicidin S on a model membrane]. / Izuchenie fiziko-khimicheskikh mekhanizmov deistviia gramitsidina S na model'nom membrane.

Influence of gramicidin S on electric parameters of nitrocellulose ultrafilter as a biomembrane model was studied, the ultrafilters being impregnated with fatty acids or their ethers. It was shown that addition of the antibiotic to the solution over one side of the model membrane resulted in generation of electric potential. With increasing of the drug concentration by one order there was observed more than a 10-fold drop in the membrane resistance while the electric capacitance actually remained unchanged. It was suggested that gramicidin S was localized in thin water layers covering the surface of the ultrafilter pores and separating the polymer matrix and impregnating liquid filling the pores. Such incorporation led to changes in the state of water and water channel surfaces which defined the increase in the model membrane electric conductivity.

[Electroneutral transport of monovalent ions by fatty acids]. / Elektroneitral'nyi perenos odnovalentnykh kationov zhirnymi kislotami.

By means of ion-selective electrodes transport of H+ and K+ ions through model membranes was studied. The latter are fatty acid esters--impregnated nitroacetatecellulose ultrafilters. Fatty acids like nigericin were shown to be ion carriers and stimulate K+--H+-exchange. The velocity of H+ ions transfer was proportional to the content of fatty acid in the membrane, it depended on the content of Mg+2 ions and decreased abruptly as a result of cooling-induced phase transition of the fatty acid.

[Comparative study of the surface-active properties of gramicidin S and its derivatives by polarography]. / Sravnitel'noe izuchenie poverkhnostno-aktivnykh svoistv gramitsidina S i ego proizvodnykh poliarograficheskim metodom.

Gramicidin S and its derivatives by the free amino groups of the ornithine moieties were studied with respect to their effect on interface tension of mercury and the polarographic background for comparative estimation of the surface active properties of these compounds. The same way as the compounds preserving their main properties, the neutral and acid derivatives lowered the polarographic maximum. No correlation between the level of the antimicrobial and membrane activity and the surface active properties of the tested compounds was observed. It is likely that the direct cause of the induced biological effect is not connected with the surface active properties responsible for possible interaction of the tested substances with the cell (protoplast).

[Reduction of spin labels with ascorbic acid in solution and on biomembranes]. / Vosstanovlenie spinovykh zondov askorbinovoi kislotoi v rastvore i na biomembranakh.

Dependence of the rate of nitroxyl radical reduction with ascorbic acid upon pH, ionic force, temperature, type of radical and dielectric constant of the solvent is reported. The factors mentioned are essential for interpreting the results obtained for biomembranes. It is shown that under physiological pH the reduction is determined by ascorbic acid monoanion and unprotonated radical interaction. In acid environment the reaction involves more complicated mechanisms. In the presence of microsome membranes the negative radical R5-COO- reduction proceeds in two steps. The first one is in power more fast than in water solution. The membrane influence was insignificant in case of the uncharged R6- = O and [Formula: see text] and radical R6-NH2 which is able to form the cation R6-NH3+.

[Study of spin-labeled microsomal membrane proteins by their reaction with ascorbic acid]. / Izuchenie spin-mechennykh belkov membran mikrosom po reaktsii s askorbinovoi kislotoi.

Kinetics of the reduction of nitroxyl radicals bound to SH-groups of microsome membrane proteins by ascorbic acid was investigated. The reduction involves two steps. During the first quick step mainly the radicals with weak immobilization located on the membrane surface are reduced. At the second slow step more immobilized radicals located in hydrophobic membrane regions take part in the reaction. A kinetic analysis of the process showed that the slow step is not determined by the slow movement of protein or its fragments, for instance, from the membrane depth to its surface, and apparently is conditioned by lower ascorbic acid concentration in the membranes.

[Ion transport through thick liquid membranes by fatty acids]. / Perenos ionov zhirnymi kislotami cherez tolstye zhidkie membrany.

Ion transfer through bulk liquid membrane induced by free fatty acids has been studied. Dependence of the rate of ion transfer upon pH change, salt concentrations, concentration and length of fatty acids and the type of cation has been obtained. These effects have been found both in H+ concentration gradient and cations of monovalent metals. It was shown that magnesium chloride inhibited the ion transfer. The scheme of stimulation with fatty acids of H+ electroneutral exchange for the cations of alkali metals has been proposed. It is supposed that the mode of action of fatty acids is more similar to nigericin than to the uncouplers of oxidative phosphorylation.

[Lipids as possible proton carriers from the respiratory chain to ATP-synthetase and the mechanism of oxidative phosphorylation]. / Lipidy kak vozmozhnye perenoschiki protona ot dykhatel'noi tsepi k ATF-sintetaze i mekhanizm okislitel'nogo fosforilirovaniia.

A scheme of oxidative phosphorylation is suggested according to which at the first stage due to the functioning of the electron-transport chain (ETC) in the points of coupling during relaxation of protein non-equilibrium conformation thermodynamically unfavourable transfer of H+ from H2O into the membrane takes place. Athe 2nd stage H+memb is carried by lipids from ETC-protein to ATP-synthetase. At the 3rd stage ATPase with ATP already contained in the active center seizes 2H+. In the course of subsequent protein relaxation the ATP interaction with the active center is disturbed, and ATP with protons transfers to H2O. In terms of the scheme proposed it proves possible to explain the respiratory control and formation of transmembrane potential difference, as well as the action mechanism of uncouplers and inhibitors of oxidative phosphorylation.

[Modeling non-enzymatic influence of membranes on the kinetics of chemical reactions]. / Modelirovanie nefermentnogo vliianiia membran na kinetiku khimicheskikh reaktsii

The reduction of nitroxide radicals by rho-phenylene diamine was studied in H2O, various organic solvents in liposome suspensions and oleic acid emulsion. Some new parameters, particularly the presence of acids, appeared to effect the rate of the process. The results obtained are consistent with the hypothesis that the electron transport in coupled membranes leads to the production of undissociated acids thus supplying protons for the ATP synthesis.