Relative orientation between the beta-ionone ring and the polyene chain for the chromophore of rhodopsin in native membranes

Results point out that the rhodopsin chromophore ring exhibits preference to 6-s-cis orientation in the dark-adapted protein, different from the twisted 6-s-trans conformation revealed by (sup)2H nuclear magnetic resonance measurements. The major portion of retinylidene in rhodopsin shows the former conformation.