论文信息 - Ultrafast Protein Dynamics of Bacteriorhodopsin Probed by Photon Echo and Transient Absorption Spectroscopy

Ultrafast Protein Dynamics of Bacteriorhodopsin Probed by Photon Echo and Transient Absorption Spectroscopy

Bacteriorhodopsin (bR) is an efficient light-driven proton pump which shows a trans-cis isomerization reaction of its retinal chromophore after light absorption. BR exhibits a large reorganization energy λ of 2520 cm-1 on optical excitation. In this paper, we have studied the nature, origin, and dynamical aspects of this extensive reorganization. We report the results of a femtosecond three-pulse echo peak shift (3PEPS), transient grating (TG) and transient absorption (TA) study, complemented with those of steady-state absorption and fluorescence spectroscopy in wild-type bR and the D85S mutant in its blue and purple, halide-pumping forms. We have simulated the results in the context of the multimode Brownian oscillator (MBO) formalism. A simple model that incorporates retinal's known intramolecular vibrations, which represent 1094 cm-1 or reorganization energy, and a single Gaussian protein relaxation with a decay of 50 fs representing 1430 cm-1 of reorganization energy, yielded satisfactory results for ...

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