Quantum-mechanical kinetic study of the primary reaction of the photochemical cycle of Halobacterium halobium

Abstract

A two-frequency oscillator model for the primary photochemical reaction bacteriorhodopsin → batho-bacteriorhodopsin (K610) is proposed. According to this model two conformational changes in the reaction are considered to take place: the first one is a distortion of the retinal in the bacteriorhodopsin active site and the second one is a conformational transition of the bacterioopsin, affecting the native structure hydrogen bonds. On the basis of this model the temperature dependences of the rate constants for normal and deuterated reactants are calculated in good agreement with the available experimental data. The relations of the reaction considered to the primary photochemical reaction of vision are discussed.