Picosecond kinetic absorption and fluorescence studies of bovine rhodopsin with a fixed 11-ene

A synthetic retinal having a fixed 11-cis geometry has been used to prepare a nonbleachable analogue of bovine rhodopsin. Marked differences in the picosecond absorption and fluorescence behavior of this analogue at room temperature, compared with that of natural rhodopsin, were observed. This not only indicates that the 11-cis to trans isomerization of the retinal moiety is the crucial primary event in the photolysis of rhodopsin, but also it establishes that this isomerization must occur on the picosecond time scale or faster.