LIGHT-INDUCED, LONG-LIVED PERTURBATION OF THE PHOTOCYCLE OF BACTERIORHODOPSIN

The relative weight of the slowly decaying M intermediate of the photocycle of bacteriorhodospin increases upon increasing the energy density of the short (10 ns) actinic laser pulse. Moreover, when a pre-exciting flash is applied to the BR sample, the absolute amplitude of the M(s) is higher in the signal induced by a second flash, applied with a delay from 100-mu-s to 100 ms. These facts together prove that either the leftover BR ground-state population becomes different due to the pre-excitation, or there is a cooperative interaction between the BR molecules.