Cis-trans isomerization in the photochemistry of vision
Cis-trans isomerization in the photochemistry of vision
复制标题
视觉光化学中的顺反异构化
DOI：
10.1351/pac197749030341
复制
发表时间：
1977
影响因子：
1.8
通讯作者：
T. Ebrey
中科院分区：
文献类型：
--
作者：
T. Rosenfeld;B. Honig;M. Ottolenghi;J. Hurley;T. Ebrey
各种模型提出的主要光事件在视觉上进行了批判性的讨论。它的结论是一个单一的顺反异构化步骤的经典图片是唯一一个令人满意的占所有可用的实验数据。进行的实验表明，该过程在200°C的范围内与温度无关。测定了11-顺式（和全反式）视黄醛游离质子化席夫碱的光异构化产率随激发波长的变化。与视紫红质的高效和波长无关的光漂白相反，自由发色团的11-cis→al-trans异构化的产率很小，表现出对激发波长的显著依赖性。通过对实验数据的分析，得到了视紫红质基态和激发态的势能曲线。与模型化合物的行为不同，颜料中的光异构化通过共同的、无势垒的、热弛豫的激发态的数量分布沿着沿着分离11-顺式（视紫红质）和全反式（视紫红质）构型的11-12扭转坐标进行。在基态，与蛋白质的相互作用使全反式异构化产物不稳定，导致在初级步骤中储存了相当大一部分光子能量。
Various models proposed for the primary photoevent in vision are critically discussed. It is concluded that the classical picture of a single cis-trans isomerization step is the only one which satisfactorily accounts for all the available experimental data. Experiments are performed showing that this process is temperature independent over a range of 200°C. Photoisomerization yields for the free protonated Schiff base of 11-cis (and all-trans) retinal are measured as a function of the excitation wavelength. In contrast to the efficient and wavelength independent photobleaching of rhodopsin, the yields of the 11-cis→al-trans isomerization of the free chromophore are small, exhibiting a marked dependence on the excitation wavelength. Potential energy curves for both ground and excited states of rhodopsin are derived from the analysis of the accumulated experimental data. In variance with the behavior of model compounds, photoisomerization in the pigment proceeds via the quantitative population of a common, barrierless, thermally relaxed excited state along the 11-12 torsional coordinate separating the 11-cis (rhodopsin) and all-trans (bathorhodopsin) configurations. In the ground state, interactions with the protein destabilize the all-trans isomerization product, leading to storage of a significant fraction of the photon's energy in the primary step.