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Structure of the intermediate species of the photoreaction cycle of rhodopsin
Author(s) -
Saran Anil,
Dhingra M. M.
Publication year - 2009
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.560220715
Subject(s) - rhodopsin , chemistry , protonation , chromophore , isomerization , deprotonation , retinaldehyde , schiff base , opsin , retinal , photochemistry , stereochemistry , polyene , biochemistry , organic chemistry , ion , catalysis
Rhodopsin is a membrane‐bound chromoprotein which has 11‐ cis retinal (aldehyde of vitamin A) as the chromophore linked to the protein opsin through a protonated Schiff base. On light absorption, rhodopsin undergoes a photoreaction cycle involving a number of intermediate species. PCILO computations have been carried out on the conformational preferences of protonated Schiff bases of 11‐ cis and 9‐ cis retinals with n ‐pentylamine as a model for lysine. The results indicate that deprotonation enhances the flexibility of the chromophore. On the basis of this result as well as that on all‐ trans retinal, two models are proposed for the structure of the intermediate species of the pohotoreaction cycle of rhodopsin. The experimental evidences, however, support model 2 in which deprotonation and cis‐trans isomerization accompany the primary photochemical event.