[Formation of free radicals during photooxidation of bacterioviridin in its monomeric and aggregated state].

ESR study of photooxidation of bacterioviridin in polar and non-polar organic solvents containing monomeric and aggregated forms of the pigment was carried out. Light-indiced formation of free radicals was shown to proceed during photooxidation of bacterioviridin with oxygen. These free radicals were similar by the ESR-signal parameters (G-factor value and the line width) to the cation-radicals initiated during photooxidation of the pigment with p-benzoquinone and at the same time differing in kinetics and temperature relationship. A small yield of radical products in the presence of oxygen is observed in non-polar solvents where bacterioviridin forms the aggregated forms with the absorption maxima of 680 and 720 nm. The study of the kinetics of photoformation of radicals within the temperature range +20-- --110 degrees allowed to reveal different stages corresponding to the oxidation of the long wave and short wave forms of bacterioviridin, photooxidation of the long wave aggregated form being the first stage of photoprocess. It is concluded that aggregations contributs to the stabilization of the primary reversible products of bacterioviridin photooxidation having the nature of free radicals.