A QM/MM study on the fast photocycle of blue light using flavin photoreceptors in their light-adapted/active form.
A QM/MM study on the fast photocycle of blue light using flavin photoreceptors in their light-adapted/active form.
复制标题
使用光适应/活性形式的黄素光感受器进行蓝光快速光循环的 QM/MM 研究。
DOI：
10.1039/b925908b
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发表时间：
2010
期刊：
影响因子：
--
通讯作者：
M. Schütz
中科院分区：
文献类型：
--
作者：
K. Sadeghian;M. Bocola;M. Schütz
基于基于含时Hartree-Fock和耦合团簇响应理论的QM/MM计算，提出了一种在信号/光适应构象中利用黄素(BLUF)结构域光循环蓝光的机制。与暗适应形式类似，电荷转移状态驱动质子从高度保守的酪氨酸残基转移到黄素生色团。后一步是由邻近的谷氨酰胺残基介导的，在光适应构象中，谷氨酰胺残基以其亚基互变异构体的形式存在。然而，甚至在质子转移完成一半之前，电荷转移和基态之间就达到了圆锥形的相交接缝。两个通道是开放的，用于衰变回到最初的光适应构象，一个快速通道直接通过锥形交叉口的漏斗，绕过双自由基中间体的形成，以及一个较慢的通道通过双自由基中间体。这里提出的机制：(I)解释了非常快速的光循环；以及(Ii)证实了光不可逆性的概念，这两个概念都已经在BLUF结构域的光适应构象中被实验观察到。
Based on QM/MM calculations using a combination of time-dependent Hartree-Fock and coupled cluster response theory a mechanism is proposed for the photocycle of blue light using flavin (BLUF) domains in the signaling/light adapted conformation. In analogy to the dark-adapted form, a charge transfer state drives proton transfer from the highly conserved tyrosine residue to the flavin chromophore. The latter step is mediated by the adjacent glutamine residue, which, in the light adapted conformation, exists as its imidic tautomer. However, before the proton transfer is even halfway completed, a conical intersection seam between the charge transfer and ground state is reached. Two channels for the decay back to the initial light-adapted conformation are open, a rapid one leading directly through the funnel of the conical intersection, bypassing the formation of the biradical intermediate, and a slower one via the biradical intermediate. The mechanism as proposed here: (i) explains the very rapid photocycle; and (ii) confirms the concept of photoirreversibility, both of which have been experimentally observed for BLUF domains in their light-adapted conformations.
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