Time-resolved resonance Raman spectroscopy of intermediates of bacteriorhodopsin: The bK590 intermediate

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We have combined microbeam and flow techniques with computer subtraction methods to obtain the resonance Raman spectrum of the short lived batho-intermediate (bK590) of bacteriorhodopsin. Comparison of the spectra obtained in 1H2O and 2H2O, as well as the fact that the bK590 intermediate shows large optical red shifts, suggests that the Schiff base linkage of this intermediate is protonated. The fingerprint region of the spectrum of bK590, sensitive to the isomeric configuration of the retinal chromophore, does not resemble the corresponding region of the parent bR570 form. The resonance Raman spectrum of bK590 as well as the spectra of all of the other main intermediates in the photoreaction cycle of bacteriorhodopsin are discussed and compared with resonance Raman spectra of published model compounds.

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