A study of the schiff base mode in bovine rhodopsin and bathorhodopsin

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48 Citations (Scopus)

Abstract

We have obtained the resonance Raman spectra of bovine rhodopsin, bathorhodopsin, and isorhodopsin for a series of isotopically labeled retinal chromophores. The specific substitutions are at retinal's protonated Schiff base moiety and include - HC = NH+ - , - HC = ND+ - , - H13C = NH+ - , and - H13C = ND+ - . Apart from the doubly labeled retinal, we find that the protonated Schiff base frequency is the same, within experimental error, for both rhodopsin and bathorhodopsin for all the substitutions measured here and elsewhere. We develop a force field that accurately fits the observed ethylenic (C = C) and protonated Schiff base stretching frequencies of rhodopsin and labeled derivatives. Using MINDO/3 quantum mechanical procedures, we investigate the response of this force field, and the ethylenic and Schiff base stretching frequencies, to the placement of charges close to retinal's Schiff base moiety. Specifically, we find that the Schiff base frequency should be measurably affected by a 3.0-4.5-Å movement of a negatively charged counterion from the positively charged protonated Schiff base moiety. That there is no experimentally discernible difference in the Schiff base frequency between rhodopsin and bathorhodopsin suggests that models for the efficient conversion of light to chemical energy in the rhodopsin to bathorhodopsin photoconversion based solely on salt bridge separation of the protonated Schiff base and its counterion are probably incorrect. We discuss various alternative models and the role of electrostatics in the rhodopsin to bathorhodopsin primary process.

Original languageEnglish (US)
Pages (from-to)7418-7426
Number of pages9
JournalBiochemistry
Volume26
Issue number23
StatePublished - 1987
Externally publishedYes

Fingerprint

Rhodopsin
Schiff Bases
Stretching
Substitution reactions
bathorhodopsin
Chromophores
Static Electricity
Raman scattering
Electrostatics
Salts
Derivatives
Light

ASJC Scopus subject areas

  • Biochemistry

Cite this

A study of the schiff base mode in bovine rhodopsin and bathorhodopsin. / Deng, Hua; Callender, Robert.

In: Biochemistry, Vol. 26, No. 23, 1987, p. 7418-7426.

Research output: Contribution to journalArticle

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