Fourier transform infrared difference spectroscopy of bacteriorhodopsin and its photoproducts.

K. Bagley, G. Dollinger, L. Eisenstein, A. K. Singh, L. Zimányi

Research output: Contribution to journalArticle

149 Citations (Scopus)

Abstract

Fourier transform infrared difference spectroscopy has been used to obtain the vibrational modes in the chromophore and apoprotein that change in intensity or position between light-adapted bacteriorhodopsin and the K and M intermediates in its photocycle and between dark-adapted and light-adapted bacteriorhodopsin. Our infrared measurements provide independent verification of resonance Raman results that in light-adapted bacteriorhodopsin the protein-chromophore linkage is a protonated Schiff base and in the M state the Schiff base is unprotonated. Although we cannot unambiguously identify the Schiff base stretching frequency in the K state, the most likely interpretation of deuterium shifts of the chromophore hydrogen out-of-plane vibrations is that the Schiff base in K is protonated. The intensity of the hydrogen out-of-plane vibrations in the K state compared with the intensities of those in light-adapted and dark-adapted bacteriorhodopsin shows that the conformation of the chromophore in K is considerably distorted. In addition, we find evidence that the conformation of the protein changes during the photocycle.

Original languageEnglish
Pages (from-to)4972-4976
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Volume79
Issue number16
DOIs
Publication statusPublished - Aug 1982

    Fingerprint

ASJC Scopus subject areas

  • General

Cite this