Crouch R, Purvin V, Nakanishi K, Ebrey T
Proc Natl Acad Sci U S A. 1975 Apr;72(4):1538-42. doi: 10.1073/pnas.72.4.1538.
We have found that in addition to the 11-cis and 9-cis isomers of retinal which are known to couple with the visual pigment apoprotein opsin to form pigments, a third isomer 9,13-dicis retinal also will form a pigment. That this isomer is indeed bound to opsin has been shown unequivocally by removing the chromophore without isomerization and subsequent identification by high-speed liquid chromatography. Using similar techniques, we have shown that the product of bleaching by light of all three pigments in Trition X-100 is the all-trans isomer. This specificity in the product of bleaching, as with many other properties of visual pigments, is not shared by the free chromophore. Of particular interest is that when 9,13-dicis retinal is combined with opsin to form a pigment, a single photon can isomerize it about two double bonds, to the all-trans isomer.
我们发现,除了已知的与视觉色素脱辅基蛋白视蛋白结合形成色素的11-顺式和9-顺式视黄醛异构体之外,第三种异构体9,13-二顺式视黄醛也会形成一种色素。通过在不发生异构化的情况下除去发色团并随后用高效液相色谱法进行鉴定,已明确证明这种异构体确实与视蛋白结合。使用类似技术,我们已表明在Triton X-100中所有三种色素经光漂白后的产物是全反式异构体。与视觉色素的许多其他特性一样,漂白产物中的这种特异性并非游离发色团所具有。特别令人感兴趣的是,当9,13-二顺式视黄醛与视蛋白结合形成一种色素时,单个光子可以使其大约两个双键异构化为全反式异构体。