Kinetic and Spectroscopic Effects of Protein‐chromophore Electrostatic Interactions in Bacteriorhodopsin

Available pH effects on the absorption spectrum and on the rates of dark adaptation (all‐trans → 13‐cis interconversion) of bacteriorhodopsin are analyzed in terms of a model based on protein‐chromophore electrostatic interactions. Plausible locations of three protein acid‐base groups controlling the spectrum and the activation energy of the thermal trans → 13‐cis process are suggested. The importance of the protein charges in controlling the cycles of bacteriorhodopsin is indicated.