Molecular Mechanism for the Initial Process of Visual Excitation. II. Theoretical Analysis of Optical Activity in Rhodopsin and Bathorhodopsin
Molecular Mechanism for the Initial Process of Visual Excitation. II. Theoretical Analysis of Optical Activity in Rhodopsin and Bathorhodopsin
复制标题
视觉兴奋初始过程的分子机制。
DOI：
10.1143/jpsj.42.996
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发表时间：
1977
影响因子：
1.7
通讯作者：
S. Yomosa
中科院分区：
文献类型：
--
作者：
H. Kakitani;T. Kakitani;S. Yomosa
本文根据文献[1]中提出的挠率模型，从视网膜发色团的内禀旋光性出发，对视紫红质和深紫红质的圆二色性光谱进行了理论分析。用自洽HMO方法处理发色团的π电子体系。从α-和β-带的光学吸收和圆二色性光谱的分析，发色团的合理构象预测如下。在视紫红质中，当从平面顺式构象顺时针测量扭转角θ时，6s-顺式、11-顺式质子化的视网膜席夫碱12 s-反式形式和键6C-7 C、11 C-12 C和12 C-13 C分别在-、+和-方向上扭转。虽然我们不能确定θ的值，但它们的范围是θ 6-7 =-40 ^° θ-120 ^°，θ 11-12 =30^° θ 40^°和θ 12-13 =-130 ^° θ-150 ^°。在视紫红质中，11 C-12 C键通过在正方向上围绕它旋转约100 ° ~ 120 °而异构化为反式形式。
The circular dichroism spectra in rhodopsin and bathorhodopsin are theoretically analysed in terms of intrinsic optical activity of the retinal chromophore according to a torsion model proposed in paper I. The self-consistent HMO method is used to treat the π-electron system of the chromophore. From the analysis of the α- and β-bands of optical absorption and circular dichroism spectra, the plausible conformation of the chromophore is predicted as follows. In rho-dopsin, 6s- cis , 11- cis protonated retinal Schiff-base 12s- trans form and the bonds 6C-7C, 11C-12C and 12C-13C are twisted in -, + and - directions, respectively, when torsional angles θ's are measured clockwise from planar cis conformation. Although we cannot determine the values of θ's definitely, the ranges of them are θ 6-7 =-40^°∼-120^°, θ 11-12 =30^°∼40^° and θ 12-13 =-130^°∼-150^°. In bathorhodopsin, the bond 11C-12C is isomerized to a trans form by the rotation of about 100∼120 around it in the plus direction.