pH and salt effects on the slow intermediates of the bacteriorhodopsin photocycle

Purple membrane fragments of Halobacterium halobium were used to investigate pH and salt effects on the kinetics of M₄₁₂, O₆₆₀ and BR₅₆₈. The flash-induced absorbance changes were measured in the 5–9 pH range, at low ionic strength and at 4 M NaCl. The results are consistent with a model which implies a branching in the last part of the bacteriorhodopsin photocycle.