Chromophore Protein Interactions in Visual Pigments and Their Analogs

HONIG and A. D. GREENBERG Dept, of Physical Chemistry, The Hebrew University, Jerusalem, Israel 

Pullman (edj. Environmental Effects on Molecular Structure and Properties. 355-362. All Rights Reserved Copyright 1976 by D. Reidel Publishing Company, Dordrecht-Holland 

Calculated and experimental spectral maxima, calculated band width parameters, and experimental band widths for various model compounds 

While a plausible model of pigment color appears to be available, the photochemical properties of visual pigments are difficult to understand in terms of existing theories. Perhaps the most interesting single observation is that the quantum yield of 0.7 for 

There is an analogy between the photochemistry of the triplet in solution and that of the visual pigments [6]. While the triplet sensitized isomerization yield of the protonated Schiff base of ll-c/5 retinal is close to 1, the yields for the other isomers with planar chains are less than half this value. Theoretical calculations indicate that a destabilization of the triplet due to twisting in the ll-c/5 isomer might account for this observation. Similar effects are predicted to be less likely in the first singlet [6], 

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CHROMOPHORE PROTEIN INTERACTIONS IN VISUAL PIGMENTS AND THEIR ANALOGS... 

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