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Proceedings of the National Academy of Sciences of the United States of America logoLink to Proceedings of the National Academy of Sciences of the United States of America
. 1994 Sep 13;91(19):8880–8884. doi: 10.1073/pnas.91.19.8880

Synergy in the spectral tuning of retinal pigments: complete accounting of the opsin shift in bacteriorhodopsin.

J Hu 1, R G Griffin 1, J Herzfeld 1
PMCID: PMC44710  PMID: 8090738

Abstract

UV-visible and solid-state NMR studies of a series of 6-s-trans protonated Schiff bases of retinal with aniline show that the bathochromic shift induced by weakening the imine counterion is significantly greater in the 6-s-trans conformation than in the 6-s-cis conformation. Based on the observed magnitude of this coupling between the electronic effects of 6-s isomerization and imine counterion strength in the model compounds, the large opsin shift and unusual chemical shifts in light-adapted bacteriorhodopsin can be fully explained. These phenomena therefore do not require a negative point charge or polarizability effects in the chromophore binding pocket. The results are consistent with an effective center-to-center distance between the Schiff base and its counterion of about 4 A in light-adapted bacteriorhodopsin.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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