Abstract
Rhodopsin, a photoreceptive protein in our eyes, is an excellent molecular switch to convertlight signal to the electrical response of the photoreceptor cells. Since the initial event of rhodopsin after absorption of a photon is a cis-trans isomerization of the retinylidene chromophore, elucidation of this isomerization mechanism has been a central issue in vision as wellas ultrafast spectroscopy. Recent progress of ultrafast spectroscopy enable us to elucidate theexcited state dynamics of rhodopsin; the Franck-Condon state has an extremely short lifetimeand converts to a fluorescent state, from which isomerization of the chromophore occurs.Chromophore isomerization is one of the fastest chemical reactions observed so far, andis achieved in the specific protein environment that have been constructed in the course ofanimal evolution.
