Following evolution of bacteriorhodopsin in its reactive excited state via stimulated emission pumping.
New information concerning the photochemical dynamics of bacteriorhodopsin (BR) is obtained by impulsively stimulating emission from the reactive fluorescent state. Depletion of the excited-state fluorescence leads to an equal reduction in production of later photoproducts. Accordingly, chromophores which are forced back to the ground state via emission do not continue on in the photocycle, conclusively demonstrating that the fluorescent state is a photocycle intermediate. The insensitivity of depletion dynamics to the "dump" pulse timing, throughout the fluorescent states lifetime, and the biological inactivity of the dumped population suggest that the fluorescent-state structure is constant, well-defined, and significantly different than that where crossing to the ground state takes place naturally. In conjunction with conclusions from comparing the photophysics of BR with those of synthetic analogues containing "locked" retinals, present results show that large-amplitude torsion around C13=C14 is required to go between the above structures.
Ruhman
Sanford
S
Department of Physical Chemistry and The Farkas Center for Light Induced Processes, The Hebrew University, Jerusalem 91904, Israel. sandy@fh.huji.ac.il
Hou
Bixue
B
Friedman
Noga
N
Ottolenghi
Michael
M
Sheves
Mordechai
M
D001436:Bacteriorhodopsins / Q000737:chemistry* / Q000502:physiology; D006217:Halobacterium / Q000737:chemistry* / Q000502:physiology; D010777:Photochemistry; D013050:Spectrometry, Fluorescence; D013055:Spectrophotometry, Infrared; D019265:Spectroscopy, Near-Infrared
D001436:Bacteriorhodopsins