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Author Kandori, Hideki ♦ Yoshihara, Keitaro ♦ Tomioka, Hiroaki ♦ Sasabe, Hiroyuki
Sponsorship USDOE
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword CHEMISTRY ♦ PIGMENTS ♦ PHOTOCHEMISTRY ♦ ISOMERIZATION ♦ TIME RESOLUTION ♦ STIMULATED EMISSION ♦ ABSORPTION SPECTROSCOPY
Abstract Primary photochemical events of the light-driven chloride-pump halorhodopsin (hR) are studied at room temperature by subpicosecond transient absorption measurements. On excitation of hR with 600-nm, 0.6-ps pulse, excited-state absorption and stimulated emission appear immediately in the 420-530-nm and 650-770-nm wavelength regions, respectively, and both decay with a time constant of 2.3 ps. The calculated absorption spectrum of the excited state of hR (hR{sup *}) has a peak at 516 nm and a shoulder at about 460 nm. Accompanied by the decay of hR{sup *}, the primary ground-state product appears at around 645 nm. The quantum yield of the product ({le} 1.0 ps) than the decay of the excited state (2.3 ps), as well as the possible presence of the J-intermediate (hR{sub J}). Instead of the simple sequential kinetic model considering three states of hR{sup *}, hR{sub J}, and hR, which has been applied to the primary process of bacteriorhodopsin, a parallel channel model is suggested for the primary process of hR. After Franck-Condon excitation, the cis-trans isomerization to hR{sub J} and the relaxation to hR{sup *} take place simultaneously. The latter decays only to hR via radiative and nonradiative processes. The present results suggest that the excited state having a reaction channel to cis-trans isomerization is not located at the potential minimum of hR{sup *} and that the relaxation process in the excited state is a process in competition with isomerization. 26 refs., 8 figs.
ISSN 00223654
Educational Use Research
Learning Resource Type Article
Publisher Date 1992-07-09
Publisher Place United States
Journal Journal of Physical Chemistry
Volume Number 96
Issue Number 14


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