Article ID Journal Published Year Pages File Type
9575333 Chemical Physics 2005 12 Pages PDF
Abstract
A new model of the primary events of the bacteriorhodopsin (BR) photocycle is derived from the analysis of vibrational spectroscopic data obtained from native BR (BR-570) and three artificial BR pigments containing structurally modified retinals with carbon rings bridging specific C-C and CC bonds (BR6.11, BR6.9, and BR5.12). Vibrational spectra from the ground-states and from picosecond intermediates appearing in the respective photo-reactions are measured by coherent anti-Stokes Raman spectroscopy (CARS). Special attention is given to an analysis of the time-dependent bandwidth changes in vibrational bands assigned to the CC stretching and hydrogen-out-of-plane (HOOP) modes. The bandwidth analysis reveals an intramolecular, vibrational dephasing mechanism in the lowest-energy electronic excited state, involving a coupling between out-of-plane motion along the retinal backbone and CC stretching modes. The mode-selective coupling plays a significant role as a precursor to the all-trans → 13-cis isomerization in BR and accounts for primary events in the BR photocycle not previously demonstrated.
Related Topics
Physical Sciences and Engineering Chemistry Physical and Theoretical Chemistry
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