| Abstract: | Abstract— In the presence of light, Tricine efficiently reduced flavin. Under aerobic conditions, oxygen uptake was observed. Inhibition studies with superoxide dismutase, with cytochrome c as electron acceptor, suggested that about 50% of the reduced oxygen was superoxide anion. Oxygen uptake by this system was markedly inhibited by 2.5 mM phenol or salicyl aldehyde. A rapid and convenient assay for superoxide dismutase was developed based on the light-induced reduction of cytochrome c by flavin mononucleotide (FMN) and Tricine. Reduction of cytochrome c in chloroplasts without addition of ferredoxin appears to be mediated by superoxide anions, as indicated by inhibition of this reaction by superoxide dismutase. Loss of photophosphorylation by sonication of chloroplasts could be partially prevented by the presence of Tricine and FMN during sonication. Phosphorylation under these conditions was dependent on white light, but no evidence for the participation of superoxide anion could be obtained with internal or external superoxide dismutase. |
