Theoretical studies on the color-tuning mechanism in retinal proteins
Theoretical studies on the color-tuning mechanism in retinal proteins
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DOI：
10.1021/ct6002687
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发表时间：
2007-03-01
影响因子：
5.5
通讯作者：
Nakatsuji, Hiroshi
中科院分区：
文献类型：
--
作者：
Fujimoto, Kazuhiro;Hayashi, Shigehiko;Nakatsuji, Hiroshi
使用对称适应簇构型相互作用 (SAC-CI) 以及量子力学和分子力学相结合 (QM/MM) 方法研究了牛视紫红质 (Rh)、细菌视紫红质 (bR) 和感觉视紫红质 II (sRII) 三种视网膜蛋白的激发态。计算的吸收能与所有三种蛋白质的实验吸收能非常一致。光谱调谐机制从三个方面进行了分析：结合袋中发色团的分子结构、发色团与周围蛋白质环境的静电（ES）相互作用以及发色团与反离子基团之间的量子力学效应。该分析深入了解了 Rh 和 sRII 的吸收峰位置相对于 bR 的吸收峰位置发生大幅蓝移的机制。蛋白质ES效应在Rh和sRII中都是最重要的，而结构效应在Rh中是次要的。发色团和反离子之间的量子力学相互作用对于激发能量的定量再现非常重要。这些结果表明，本方法可用于研究视网膜蛋白质的吸收光谱和颜色调节机制。
The excited states of the three retinal proteins, bovine rhodopsin (Rh), bacteriorhodopsin (bR), and sensory rhodopsin II (sRII) were studied using the symmetry-adapted cluster-configuration interaction (SAC-CI) and combined quantum mechanical and molecular mechanical (QM/MM) methods. The computed absorption energies are in good agreement with the experimental ones for all three proteins. The spectral tuning mechanism was analyzed in terms of three contributions: molecular structures of the chromophore in the binding pockets, electrostatic (ES) interaction of the chromophore with the surrounding protein environment, and quantum-mechanical effect between the chromophore and the counterion group. This analysis provided an insight into the mechanism of the large blue-shifts in the absorption peak position of Rh and sRII from that of bR. Protein ES effect is primarily important both in Rh and in sRII, and the structure effect is secondary important in Rh. The quantum-mechanical interaction between the chromophore and the counterion is very important for quantitative reproduction of the excitation energy. These results indicate that the present approach is useful for studying the absorption spectra and the mechanism of the color tuning in the retinal proteins.