ORIENTATIONAL CHANGES OF THE TRANSITION DIPOLE-MOMENT OF RETINAL CHROMOPHORE ON THE DISK MEMBRANE DUE TO THE CONVERSION OF RHODOPSIN TO BATHORHODOPSIN AND TO ISORHODOPSIN

The changes in the orientation of the transition dipole moment of the retinal chromophore of rhodopsin when converted to bathorhodopsin and to isorhodopsin in the disk plane were determined. A bullfrog retina was successively irradiated with plane polarized light at 437 nm at liquid nitrogen temperature. The absorbance at 640 nm was measured with plane polarized light along the direction perpendicular to the disk plane with rotation of a polarizer. The angle-absorbance curves thus obtained were simulated in time course by theoretical analysis. The results showed that the angle between the transition dipole moments of rhodopsin and bathorhodopsin or isorhodopsin was 20° or 17°, respectively, in the disk plane. © 1979.