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

Abstract

We have combined microbeam and flow techniques with computer subtraction methods to obtain the resonance Raman spectrum of the short lived batho-intermediate (bK ₅₉₀) of bacteriorhodopsin. Comparison of the spectra obtained in ¹H₂O and ²H₂O, as well as the fact that the bK ₅₉₀ intermediate shows large optical red shifts, suggests that the Schiff base linkage of this intermediate is protonated. The fingerprint region of the spectrum of bK ₅₉₀, sensitive to the isomeric configuration of the retinal chromophore, does not resemble the corresponding region of the parent bR ₅₇₀ form. The resonance Raman spectrum of bK ₅₉₀ 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.

• purple membrane
• kinetics
• batho-intermediate
• prelumi-bacteriorhodopsin
• Raman microbeam