FLASH PHOTOLYSIS OF FLAVINS‐II. QUENCHING OF THE PHOTOREACTIONS*,†

Abstract— Quenching of the degradative photobleaching of FMN in anaerobic aqueous solution, and of the flavin‐sensitized photo‐oxidation of EDTA, alcohols, glycols, and glycerol, has been examined using flash techniques. The quenching can be produced by addition of KI, by successive flashes, and by increasing the flavin concentration (self‐quenching). It is concluded that the lowest triplet is the photoreactive species in all systems, that the successive flash effect is due to triplet quenching by a reaction product, and that the concentration quenching may be due to either triplet‐triplet annihilation or to reaction between a ground‐state flavin and a flavin triplet.