Kinetics of Light‐Induced Intramolecular Charge Transfer and Proton Release in Bacteriorhodopsin

Recent advances in understanding the intramolecular charge transfer and proton release by the light‐driven proton pump bacteriorhodopsin (bR) are critically reviewed. The focus is on the time‐resolved electrical methods, i.e., photocurrent and photovoltage measurements, and on transient absorption experiments with pH‐sensitive dyes. Particular attention is paid to the following topics: charge translocation in the low‐pH forms of bR (acid‐blue and acid‐purple); electrogenicity of the 13‐ cis cycle; results with bR mutants; surface‐bound dyes to detect the proton release at specific sites on either side of the protein; the question of kinetic coupling between the deprotonation of the Schiff base and proton release; and rapid long‐range migration of protons along the surface of the purple membrane.