Femtosecond spectroscopy of a 13-demethylrhodopsin visual pigment analogue: The role of nonbonded interactions in the isomerization process

Journal Article · Thu Oct 24 04:00:00 EDT 1996 · Journal of Physical Chemistry

DOI:https://doi.org/10.1021/jp961150s· OSTI ID:420729

Wang, Q; Shank, C V ^[1]; Kochendoerfer, G G; Mathies, R A ^[2]; Schoenlein, R W ^[1]; Verdegem, P J.E.; Lugtenburg, J ^[3]

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1. Lawrence Berkeley National Lab., CA (United States)
2. Univ. of California, Berkeley, CA (United States)
3. 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, Journal Name: Journal of Physical Chemistry Journal Issue: 43 Vol. 100; ISSN JPCHAX; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

40 CHEMISTRY
55 BIOLOGY AND MEDICINE
BASIC STUDIES
ABSORPTION SPECTRA
ATOMS
CHEMICAL REACTION KINETICS
DYE LASERS
ELECTROMAGNETIC PULSES
HYDROGEN
ISOMERIZATION
PHOTOCHEMICAL REACTIONS
PHOTOLYSIS
PIGMENTS
PROTEINS
RHODOPSIN
TIME DEPENDENCE
VISION