Resonance Raman analysis of the mechanism of energy storage and chromophore distortion in the primary visual photoproduct

The vibrational structure of the chromophore in the primary photoproduct of vision, bathorhodopsin, is investigated to determine the cause of the anomalously decoupled and intense C(sub 11)=C(sub 12) hydrogen-out-of-plane (HOOP) wagging modes and their relation to energy storage in the primary photoproduct. The results suggest that the distortions are caused by three constraints consisting of an electrostatic anchor between the protonated Schiff base and the Glu113 counterion, as well as steric interactions of the 9- and 13-methyl groups with surrounding residues.