Assigning the resonance Raman spectral features of rhodopsin, isorhodopsin and bathorhodopsin in bovine photostationary state spectra.

Abstract—High resolution resonance Raman spectra of rhodopsin. isorhodopsin and photostationary state mixtures containing a high percentage of bathorhodopsin arc presented. New spectral features are detected which were not obsei-ved in lower resolution studies by other workers. All of the hands in the photostationary state spcctra arc assigned based on pure rhodopsin and isorhodopsin resonance Raman results and alterations in the photostationary state mixture. The spectral features in these spectra are invariant from 20 to 150K indicating that retinal and protein structural alteration, consistent with a model of excitation proposed by Lewis, occurs in steady-state spectra even at 20 K. In addition, the relative intensity of certain features in the photostationary state spectra are altered upon D₂O suspension. One explanation for these alterations is that the contributions of various intcrmediates to the photostationary state mixture are changed when membrane fragments are suspended in D₂O.