PHOTOCHEMISTRY OF RHODOPSIN AND ISORHODOPSIN INVESTIGATED ON A PICOSECOND TIME SCALE

Bovine rhodopsin and isorhodopsin were excited with a single 530 nm, 7 ps light pulse emitted by a mode-locked Nd3+ glass laser at room temperature. Within 3 ps of excitation, absorbance changes due to formation of bathorhodopsin were observed. The difference spectra generated during and 100 ps after pulse excitation are presented. Bathorhodopsin formation is completed within 3 ps for both primary pigments. A single common bathorhodopsin is apparently photochemically formed from both primary pigments. These findings provide additional support for the cis-trans isomerization model of the primary event in vision. Additional absorption transients that were observed near 670 and 460 nm are discussed.