Аннотация:Flash-induced changes of redox potential of the medium and of the concentration of the secondary quinone were observed in the same samples containing redox mediators and chromatophores of R. rubrum. Comparison of the kinetic curves shows that after the first flash the rate of relaxation of the redox potential of the medium to the initial level is determined by the interaction of the redox mediator and semiquinone form of the secondary quinone, whereas after all the successive flashes the rate of this process is determined by the interaction of redox mediator and electron acceptors which are working in the electron transport chain after the secondary acceptor. A kinetic model of the flash-induced changes of the redox potential of the medium is proposed. The observed flash-induced changes of the redox potential of the medium are described on the base of this model.