Femtosecond time-resolved absorption and time-resolved resonance Raman spectroscopy are used to examine the molecular mechanism of the light-driven proton pump in bacteriorhodopsin. Transient absorption spectroscopy with 6-fs pulses is used to directly observe the excited-state, double bond torsional isomerization of the retinal chromophore. Time-resolved resonance Raman spectroscopy is used to determine the structure of the retinal prosthetic group in each of the subsequent photolytic intermediates. Based on these results, a new "C-T Model" for the molecular mechanism of the proton pump has been developed. The key feature of this model is an isomerization-driven conformational change of the protein from the T-form to the C-form which acts as a "reprotonation switch" and stores energy to drive later events in the photocycle.

Date Published: 8 May 1989
PDF: 8 pages
Proc. SPIE 1057, Biomolecular Spectroscopy, (8 May 1989); doi: 10.1117/12.951656

Published in SPIE Proceedings Vol. 1057:
Biomolecular Spectroscopy
Robert R. Birge; Henry H. Mantsch, Editor(s)