Fluorescence quantum yield of visual pigments: evidence for subpicosecond isomerization rates

摘要: Abstract The fluorescence quantum yields (phi f) for bovine and squid rhodopsins are determined. Both pigments yield similar results, with an average value phi f of 1.2 (+/- 0.5) X 10(-5). Since the estimated radiative lifetime rhodopsin is 5 nsec, rate constant process that competes must be on order 0.1 psec. Given large isomerization rhodopsin's retinal chromophore, this likely to correspond motion along retinal's C11-C12 torsional coordinate leads cis-trans isomerization. An empirical excited-state potential energy curve derived. It shown subpicosecond highly twisted nonfluorescing regions possible and, in fact, likely. Our results require existence a barrier-less suggest occurs less than 1