Time-resolved resonance Raman spectroscopy of intermediates of bacteriorhodopsin: The bK 590 intermediate

Abstract

Microbean and flow technique were combined 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, and 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 and 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.