Determination of Chromophore Structure and Photochemistry in Bacteriorhodopsin with Resonance Raman, NMR, and Chemical Analogues
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.
The title polymers have been prepared by nucleophilic substitution of 2,3-dimethyl- and trimethylhydroquinone, and 3,3′-dimethyl- and 3,3′,5,5′-tetramethylbiphenol with difluorobenzophenone. These polymers have been brominated to various degrees of substitution. The dimethyl PEEK can only be monobrominated; trimethyl PEEK yields mono- and dibromomethyl functional groups in the ratio 2:1. These results can be explained by steric hindrance to dibromination of the vicinal methyl groups. Dimethyl- and tetramethylbiphenyl PEEK can be dibrominated completely.