Boggio-Pasqua Martial, Robb Michael A, Groenhof Gerrit
Laboratoire de Chimie et Physique Quantiques, IRSAMC, CNRS et Universite de Toulouse, Toulouse, France.
J Am Chem Soc. 2009 Sep 30;131(38):13580-1. doi: 10.1021/ja904932x.
We have performed excited-state dynamics simulations of a Photoactive Yellow Protein chromophore analogue in water. The results of the simulations demonstrate that in water the chromophore predominantly undergoes single-bond photoisomerization, rather than double-bond photoisomerization. Despite opposite charge distributions in the chromophore, excited-state decay takes place very efficiently from both single- and double-bond twisted minima in water. Radiationless decay is facilitated by ultrafast solvent reorganization, which stabilizes both minima by specific hydrogen bond interactions. Changing the solvent to the slightly more viscous D(2)O leads to an increase of the excited-state lifetime. Together with previous simulations, the present results provide a complete picture of the effect of the protein on the photoisomerization of the chromophore in PYP: the positive guanidinium group of Arg52 favors double-bond isomerization over single-bond isomerization by lowering the barrier for double-bond isomerization, while the hydrogen bonds with Tyr42 and Glu46 enhance deactivation from the double-bond twisted minimum.
我们对一种光活性黄色蛋白发色团类似物在水中进行了激发态动力学模拟。模拟结果表明，在水中发色团主要发生单键光异构化，而非双键光异构化。尽管发色团中电荷分布相反，但在水中，从单键和双键扭曲的最低能量状态出发，激发态衰变都能非常高效地发生。超快的溶剂重组促进了无辐射衰变，通过特定的氢键相互作用使两种最低能量状态都得以稳定。将溶剂换成黏度稍高的D₂O会导致激发态寿命增加。结合之前的模拟结果，目前的研究结果完整地呈现了蛋白质对PYP中发色团光异构化的影响：精氨酸52的正胍基通过降低双键异构化的势垒，相比于单键异构化更有利于双键异构化，而与酪氨酸42和谷氨酸46形成的氢键则增强了从双键扭曲最低能量状态的失活过程。
