QM/MM Trajectory Surface Hopping Approach to Photoisomerization of Rhodopsin and Isorhodopsin: The Origin of Faster and More Efficient Isomerization for Rhodopsin
QM/MM Trajectory Surface Hopping Approach to Photoisomerization of Rhodopsin and Isorhodopsin: The Origin of Faster and More Efficient Isomerization for Rhodopsin
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DOI：
10.1021/jp212378u
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发表时间：
2012-07-19
影响因子：
3.3
通讯作者：
Ishida, Toshimasa
中科院分区：
文献类型：
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作者：
Chung, Wilfredo Credo;Nanbu, Shinkoh;Ishida, Toshimasa
采用基于朱-中村非绝热跃迁理论的QM/MM混合轨道跃迁分子动力学方法，研究了视紫红质和异视紫红质的光致顺反异构化动力学。视紫红质和异视紫质以11顺式和9顺式视网膜为发色团，这两种蛋白异构化为包被全反式视紫红质的视紫红质。该模拟再现了视紫红质中的异构化反应比异视紫质中的异构化反应更快、更有效。在激发态，视紫红质表现出简单的动力学，而等视紫红质的动力学是相当复杂的，并且是以来回的方式。后者的复杂动力学主要是由于在视蛋白中由苏氨酸118和酪氨酸268产生的活性二面角=C8-C9=C10-C11=(Phi(9))附近有一个狭窄的空间。视紫红质只能产生视紫红质，而异视紫红质会产生副产物。视紫红质的严格选择性将是视紫红质被生物学选择的另一个原因。与我们以前的无视蛋白研究相比，光学蛋白倾向于将活性二面体的扭曲限制在一个方向上，并且漏斗过渡到最小能量锥形交点(MECI)附近。扭转限制完全阻止了Phi(9)和Phi(11)(=C10-C11=C12-C13=)的同时扭曲，提高了量子产额。Phi(9)和Phi(11)的相反旋转(“拧湿毛巾”运动)在光激发下发生，这也是在没有光学蛋白的情况下发生的。与MECI位置预期的运动相比，扭动湿毛巾的运动得到了动态增强。目前的模拟表明，Weiss-Warshel模型的顺反光异构化不适用于视紫红质，因为跃迁后的支化比是关键的。
The photoinduced cis-trans isomerization dynamics of rhodopsin and isorhodopsin are studied using a newly developed hybrid QM/MM trajectory surface hopping MD scheme based on the Zhu-Nakamura theory for nonadiabatic transitions. Rhodopsin and isorhodopsin have 11-cis and 9-cis forms of retinal as chromophore and the two proteins are isomerized to bathorhodopsin enclosing the all-trans form. The simulation reproduced faster and more efficient isomerization in rhodopsin than in isorhodopsin. In the excited state, rhodopsin shows a straightforward dynamics, whereas isorhodopsin dynamics is rather complicated and in a back-and-forth manner. The latter complicated dynamics would be mainly due to a narrow space near the active dihedral angle = C8-C9 = C10-C11 =(phi(9)) created by Thr 118 and Tyr 268 in opsin. Rhodopsin gives bathorhodopsin only while isorhodopsin yields a byproduct. The rigorous selectivity in rhodopsin would be another reason why rhodopsin is selected biologically. Comparison with our previous opsin-free investigations reveals that opsin tends to confine the twist of the active dihedral to only one direction and funnels transitions into the vicinity of minimum energy conical intersections (MECI). The twist-confinement totally blocks simultaneous twisting of phi(9) and phi(11) (= C10-C11 = C12-C13 =) and enhances the quantum yields. The opposite rotation of phi(9) and phi(11) ("wring-a-wet-towel" motion) takes place upon photoexcitation, which also does without opsin. The wring-a-wet-towel motion is dynamically enhanced in comparison with the one expected from locations of the MECI. The present simulation reveals that the Weiss-Warshel model for cis-trans photoisomerization is not applicable for rhodopsin because the branching ratio after transition is crucial.