Opsin structure probed by raman spectroscopy of photoreceptor membranes.

The first nonresonance Raman spectra of photoreceptor membranes are presented. Information about the membrane protein, opsin, and the membrane phospholipids can be deduced. Opsin appears to contain alpha-helical structure but little beta structure. The tyrosine residues are predominantly hydrogen bonded, and disulfide bonds, if they are present, are not in the normal gauche-gauche configuration.