THE PHOTOREACTION OF THE DEIONIZED FORM OF THE PURPLE MEMBRANE INVESTIGATED BY FTIR DIFFERENCE SPECTROSCOPY

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Abstract
Abstract— Deionization of the purple membrane of Halobacterium halobium shifts the visible absorption maximum from 570 to 605 nm and inhibits proton transport. FTIR‐difference‐spectra of this blue membrane at 280 K reveal that the retinal chromophore adopts a 13‐cis and all‐trans geometry in a light dependent ratio. In contrast to purple membrane the 13‐cu isomer forms much faster in the dark. The all‐trans component produces an L‐intermediate which can be stabilized at 170 K. Spectral characteristics are similar to normal L. including comparable changes of internal aspartic acids of the opsin. However, stronger changes in the amide‐I absorption are observed. IR bands of the chromo‐protein states are assigned to retinal normal modes by the use of bacteriorhodopsin regenerated with'C‐labeled retinals.