Recombination reduction of photooxidized cytochrome c in reaction centers of Rhodopseudomonas viridis at low temperature

The temperature dependence of dark reduction of photooxidized cytochrome c was studied in isolated preparations of Rhodopseudomonas viridis reaction c enters. Within the range from room temperature to similar to 260 K this pro cess was found to be mediated by thermal diffusion of exogenous donor molec ules, whereas at lower temperatures photooxidized cytochrome is reduced as a result of indirect recombination with photoreduced primary quinone accept or. Kinetic simulation allowed certain thermodynamic characteristics of thi s reaction to be calculated. To the first approximation, these characterist ics correlate with the estimates obtained from the results of direct redox titration.