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Structural features underlying the anesthetic-induced equilibrium between three spectral species of bacteriorhodopsin: bR570, bR480and bR380

Authors
Journal
Journal of Molecular Structure
0022-2860
Publisher
Elsevier
Publication Date
Volume
297
Identifiers
DOI: 10.1016/0022-2860(93)80154-n

Abstract

Abstract In the presence of halogenated anesthetics and under moderate pH conditions, bacteriorhodopsin exists in equilibrium between three different spectral forms absorbing at 570, 480 and 380 nm. We examined the pigment containing these three chromophores by means of resonance Raman and FT-IR spectroscopy. Our results show that in the 480 nm chromophore the protonation state of the retinal Schiff base is not different from that of the native 570 nm bacteriorhodopsin. The FT-IR spectra indicate that the sequential formation of bR 480 and bR 380 is accompanied by a reversible disorientation of the pigment α helices with respect to one another, and that the phenomenon remains fully reversible as long as the secondary structure of the helices is not modified.

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