A light-initiated, dark oxidation of bacteriochlorophyll from reaction center particles

When reaction center particles from Rhodopseudomonas spheroides strain R26 are illuminated and then extracted with methanol, about one-third of the extracted bacteriochlorophyll slowly becomes oxidized, The oxidation does not occur under anaerobic conditions or in the absence of the detergent lauryldimethylamine oxide. Alkaline conditions also prevent the reaction. A dark interval between illumination and extraction delays the onset of bacteriochlorophyll oxidation in a predictable way. These results are consistent with the hypothesis that illumination generates a reaction initiator which is fairly stable in methanol but decays with a half-life of about 4.5 min in reaction center particles after illumination ceases.