[Reduction of spin labels with ascorbic acid in solution and on biomembranes].

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+.