Femtosecond spectroscopy of a 13-demethylrhodopsin visual pigment analogue: The role of nonbonded interactions in the isomerization process
- Lawrence Berkeley National Lab., CA (United States)
- Univ. of California, Berkeley, CA (United States)
- Leiden Univ. (Netherlands)
The photoisomerization reaction of the visual pigment analogue 11-cis-13-demethylrhodopsin is investigated using femtosecond pump-probe techniques. Following excitation with a 40-fs pump pulse at 500 nm, differential trasnsient absorption spectra are measured from 470 to 560 nm using a 10-fs probe pulse centered at 500 nm and from 560 to 650 nm using a 10-fs probe pulse centered at 620 nm. The persistence of the excited-state absorption, the recovery kinetics of the ground-state bleach, and the formation time of the photoproduct absorption all indicate that this photoisomerization reaction is complete on the 400-fs time scale. Comparison of the reaction dynamics of 11-cis-rhodopsin with 11-cis-13-demethylrhodopsin suggests that the removal of the nonbonded steric intersection between the C{sub 13}-methyl group and the C{sub 10}-hydrogen atom slows down the initial torsional dynamics and that this in turn results in a lower isomerization quantum yield and a slower overall reaction time. Our results support the hypothesis that the quantum yield and the speed of the isomerization reaction are coupled according to a dynamic potential-sulfate crossing mechanism. 27 refs., 5 figs.
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 420729
- Journal Information:
- Journal of Physical Chemistry, Vol. 100, Issue 43; Other Information: PBD: 24 Oct 1996
- Country of Publication:
- United States
- Language:
- English
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