SUBSTATES IN BACTERIORHODOPSIN PHOTOCYCLE

On the basis of our previous data concerning photoelectric and optical absorption kinetic measurements performed on purple membranes of D85N , D212N, and D96N mutants (1,2) and of additional information concerni ng D96N mutant, the bacteriorhodopsin photocycle was analyzed using th e sequential model with reversible reactions. The rate constants of th e reactions were obtained from the absorption change signals by fittin g the time-dependent concentrations. From the rate constants, the elec trogenicities of the intermediates were calculated by fitting the elec tric response signals. From considerations made upon kinetic and charg e motion studies, the necessity of introducing substates of the interm ediates arose, allowing us to draw some conclusions about the possible sequence of reactions in bacteriorhodopsin photocycle.