Towards understanding the ultra-fast dynamics of rhodopsin

Abstract

The photoisomerization of rhodopsin in 200 femtoseconds is among the fastest and most efficient photochemical reactions known. We have developed a microscopic model to study rhodopsin's dynamics which retains the collective quantum mechanics of the π electrons in the conjugated system. Our model is a generalization to three dimensions of Su, Schrieffer, and Heeger's model for polyacetylene (CH)x. Model parameters are inferred from comparison with experiments and ab initio calculations. The spatial structure and vibrational modes of the rhodopsin chromophore 11-cis retinal are calculated and shown to agree quite well with NMR and Raman spectroscopy measurements. Dynamics following photoexcitation are studied.