Insights into excited-state and isomerization dynamics of bacteriorhodopsin from ultrafast transient UV absorption

A visible-pump/UV-probe transient absorption is used to characterize the ultrafast dynamics of bacteriorhodopsin with 80-fs time resoln. We identify three spectral components in the 265- to 310-nm region, related to the all-trans retinal, tryptophan (Trp)-86 and the isomerized photoproduct, allowing us to map the dynamics from reactants to products, along with the response of Trp amino acids. The signal of the photoproduct appears with a time delay of ~250 fs and is characterized by a steep rise (~150 fs), followed by addnl. rise and decay components, with time scales characteristic of the J intermediate. The delayed onset and the steep rise point to an impulsive formation of a transition state on the way to isomerization. We argue that this impulsive formation results from a splitting of a wave packet of torsional modes on the potential surface at the branching between the all-trans and the cis forms. Parallel to these dynamics, the signal caused by Trp response rises in ~200 fs, because of the translocation of charge along the conjugate chain, and possible mechanisms are presented, which trigger isomerization. [on SciFinder (R)]

Published in:
Proceedings of the National Academy of Sciences of the United States of America, 103, 11, 4101-4106
CAN 144:345475
General Biochemistry
Laboratoire de Spectroscopie Ultrarapide, Institut des Sciences et Ingenierie Chimiques, Faculte des Sciences de Base,Ecole Polytechnique Federale de Lausanne,Lausanne-Dorigny,Switz.
written in English.
73-22-3 (L-Tryptophan); 116-31-4 (all-trans-Retinal) Role: BSU (Biological study, unclassified), PRP (Properties), BIOL (Biological study) (Trp86 response mirrors change in permanent dipole moment of retinal after excitation in bacteriorhodopsin)
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 Record created 2007-05-31, last modified 2018-03-17

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