Lifetime of M Intermediate in the D96N Mutant of Bacteriorhodpsin Determined by a Photoelectrochemical Method

The recombinant D96N mutant of bacteriorhodopsin (bR) was immobilized on SnO2 electrode that contacts an aqueous electrolyte. By laser pulse excitation, photocurrent behavior of D96N was analyzed to evaluate the lifetime of the M intermediate involved in proton transfer reactions. The half-life of the M intermediate in the photocycle was about 5 s, which is 10-fold longer than that of wild-type and shows the crucial role of D96 in the uptake of protons.