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. 1986 Apr;5(4):805–811. doi: 10.1002/j.1460-2075.1986.tb04285.x

Evidence for light-induced 13-cis, 14-s-cis isomerization in bacteriorhodopsin obtained by FTIR difference spectroscopy using isotopically labelled retinals

Klaus Gerwert 1,1, Friedrich Siebert 1
PMCID: PMC1166862  PMID: 16453681

Abstract

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 C14–C15 and C=N stretching vibrations of the various intermediates. The lower C14–C15 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.

Keywords: FTIR, bacteriorhodopsin, vibrational analysis, proton pump mechanism, retinal isotopic derivatives

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Selected References

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