Berlin 2005 – wissenschaftliches Programm
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AKB: Biologische Physik
AKB 200: Poster Session II
AKB 200.56: Poster
Dienstag, 8. März 2005, 17:00–19:00, Poster TU C
Modelling the Structure and Optical Properties of the Rhodopsin Chromophore — •Minoru Sugihara1, Marko Schreiber2, Peter Entel1, and Volker Buss2 — 1Theoretical Physics, University of Duisburg-Essen — 2Theoretical Chemistry, University of Duisburg-Essen
Modelling the Rhodopsin Chromophore with QM/MM: Four available X-ray structures of rhodopsin show a considerable variety of the chromophore geometry despite the similarity of the chromophore binding pocket. Based on the recent two crystal structures obtained by Okada [1,2], we have re-investigated the chromophore geometry applying QM/MM methodology. Our results show that the different chromophore geometries converge to practically one identical structure, which shows strong bond alternation and is twisted, in addition to the ionone ring, in the region undergoing photoisomerization [2].
Calculation of the Optical Properties with Ab-Initio Method: (CASPT2) Using the calculated chromophore geometry inside the binding pocket the absorption maximum of the chromophore was calculated. Two factors were considered: the internal distorsion and the presence of the counterion. We find that the first excited state is weakly red-shifted (ca. 20nm) due to the deformation of the chromophore and is strongly blue-shifted (ca. 100nm) in the presence of the counterion [3].
[1] T. Okada, et al. Proc. Natl. Acad. Sci. USA, 99 (2002) 5982. [2] T. Okada, et al. J. Mol. Biol. 342 (2004) 517. [3] M. Schreiber, et al. J. Chem. Phys. 23 (2003) 12045