Rhodopsin photochemistry is vibrationally coherent

Conference · Sun Dec 31 04:00:00 EST 1995

OSTI ID:215114

Mathies, R A; Wang, Q; Peteanu, L A ^[1]

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1. Lawrence Berkeley Lab., CA (United States); and others

Visual excitation is initiated by the absorption of a photon by the 11-cis retinal chromophore bound within the pigment called rhodopsin. We have used a variety of vibrational spectroscopies to obtain information about the vibrational nuclear dynamics that lead to this efficient photochemical isomerization. The cis-trans isomerization in rhodopsin is complete in only 200 fs. The extreme speed of this process, which is consistent with the {approximately}50 fs lifetime indicated by the spontaneous emission yield, suggests that the photochemistry involves non-stationary states or vibrational coherence. Recent studies have in fact observed vibrationally coherent oscillations of the ground state photoproduct called bathorhodopsin following impulsive excitation of the rhodopsin reactant. This conclusively demonstrates that the isomerization process in rhodopsin is vibrationally coherent. These observations further suggest that the isomerization quantum yield is directly dependent on the excited-state torsional velocity and can be thought of as a Landau-Zener tunneling process. This work establishes a vibrationally coherent paradigm for the photochemistry of vision that may be relevant for many other photochemical and photobiological processes including photosynthesis and proton pumping in bacteriorhodopsin.

• OSTI ID: 215114
• Report Number(s): CONF-950801--
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
40 CHEMISTRY
55 BIOLOGY AND MEDICINE
BASIC STUDIES
EXCITATION
ISOMERIZATION
PHOTOCHEMISTRY
PHOTOSYNTHESIS
RHODOPSIN
VISION