Abstract
Bacteriorhodopsin (BR) is an intrinsic membrane protein that transduces light-energy into a trans-membrane protonmotive force. To elucidate the mechanism of this important process, it is necessary to determine the structure of the retinal chromophore in BR and its intermediates and to characterize important chromophore-protein interactions. This paper will review recent physical chemical and bio-organic approaches that we have developed to study chromophore structure and environment in bacteriorhodopsin. A model for the molecular mechanism of proton-pumping based on inversion of the unprotonated Schiff base nitrogen is presented.