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Evidence for light‐induced 13‐ cis , 14‐s‐ cis isomerization in bacteriorhodopsin obtained by FTIR difference spectroscopy using isotopically labelled retinals
Author(s) -
Gerwert Klaus,
Siebert Friedrich
Publication year - 1986
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1002/j.1460-2075.1986.tb04285.x
Subject(s) - bacteriorhodopsin , isomerization , fourier transform infrared spectroscopy , physics , spectroscopy , chemistry , optics , quantum mechanics , biochemistry , membrane , catalysis
We have obtained by Fourier transformed infra‐red (FTIR)‐spectroscopy BR‐K, BR‐L and BR‐M difference spectra of bacteriorhodopsin regenerated with isotopically labelled retinals. Thereby, we are able to assign reliably the C 14 –C 15 and C=N stretching vibrations of the various intermediates. The lower C 14 –C 15 stretching vibration frequency in L as compared with 13‐ cis protonated Schiff base model compounds indicates a 13‐ cis , 14‐s‐ cis configuration of the retinal in this species. The unusually low C=N stretching vibration in K at 1615 cm −1 indicates less stabilization of the positive charge at the Schiff base by the protein environment. Based on these results, a mechanism is suggested by which the stored light energy is transformed into proton transfers.