Chromophores opsin interaction

The study of visual pigment analogs serves to clarify the nature of chromophore-opsin interactions in visual pigments. Visual pigment analogs are modified retinals bound to opsins, which can be investigated by spectroscopic and biochemical methods. 

Changes in Chromophore-Opsin Interaction in Bleaching Process of Rhodopsin... 

While the factors resulting here in a given distortion are intramolecular, the conclusions we can draw may be applied to cases where an isolated molecule is distorted by its environment. We would like to examine this approach as starting point for treating the effect of the 11-cw retinal-opsin interaction on the photoisomerization quantum yield of 11-cw to aW-trans retinal. This quantum yield increases from 0.2 for the free chromophore [9] to 0.66 in rhodopsin [10]. This value is close to that of the biacetyl sensitized reaction of the free chromophore, 0.75 [11], and indicates that the triplet state is involved to a large extent in the photoisomerization of ll-cis retinal and that intersystem crossing is inefficient. 

Saari has made the bold statement that Three derivatives of 11-cis-retinaldehyde serve as the chromophores of all known visual pigments. They are complexed with a protein component (an opsin), and the resulting protein-retinoid interactions determine the spectral sensitivity of the visual pigment. 85 No reference is given for this statement nor is any explanation of how these complexes exhibit an absorption spectrum in the visual region. However, except for the substitution of all-trans for 11 -cis in the above quotation and a slight modification to the retinoid involved, this work agrees completely with the statement and provides an explanation for how it is applied. 

Callender, Biochemistry 13, 4243 (1974). Each pigment has unique physiochemical properties. The most significant is the absorption spectrum which is regulated by electrostatic interactions between the chromophore and the charged or dipolar groups on the opsin R. Hubbard, L. Sparling, Exp. Eye Res. 17, 581 (1973) B. Honig et al, J. Am, Chem. Soc. 101, 7084 (1979). 

Shichida, Y., Ono, X, Yoshizawa, T., Matsumoto, H., Asato, A.E., Zingoni, J.P., and Liu, R.S., Electrostatic interaction between retinyUdene chromophore and opsin in rhodopsin studied by fluorinated rhodopsin analogues. Biochemistry, 26, 4422, 1987. 

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