Regensburg 2007 – wissenschaftliches Programm
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BP: Fachverband Biologische Physik
BP 26: Poster Session II
BP 26.28: Poster
Donnerstag, 29. März 2007, 17:00–19:30, Poster B
Chemically modified chromophore in rhodopsin — •Minoru Sugihara1, Oliver Weingart2, Peter Entel1, and Volker Buss2 — 1Theoretical Physics, University of Duisburg-Essen — 2Theoretical Chemistry, University of Duisburg-Essen
The 11-cis retinal protonated Schiff base is the chromophore of rhodopsin, which is a transmembrane protein in the rod cells of vertebrate eyes. On photo-excitation it isomerizes from a 11-cis to all-trans form. This reaction is the initial step in vision and induces a sequence of biochemical reactions, which eventually lead to the stimulation of the visual nerve.
The crystal structure of rhodopsin has recently been extended to 2.2 A resolution [1]. Based on this structure we have modeled the retinal chromophore and three chemically modified structures: 13-demethyl-, 10-methyl-13-demethyl- and 10 methyl-retinal with a quantum mechanical/molecular mechanical method [1,2]. Using these structures we were able to study systematically the influence of methyl substitution at 10- and 13-position on geometries and excited state dynamics. We found that the protein environment induces geometrical distortions around the isomerizing region and the initial pre-twist has significant influence on the reaction of the chromophore [3].
[1] T. Okada, M. Sugihara, A.-N. Bondar, et al. J. Mol. Biol. 341(2004) 571. [2] M. Sugihara, J. Hufen, V. Buss, Biochemistry 45 (2006) 801. [3] O. Weingart, I. Schapiro, V. Buss, submitted to J. Phys. Chem. A.