Max-Planck-Institut für Medizinische Forschung, Jahnstraße 29, 69120, Heidelberg, Germany.
Univ. Grenoble Alpes, CNRS, CEA, Institut de Biologie Structurale, 71 Avenue des Martyrs, 38000, Grenoble, France.
Nat Commun. 2019 Jul 18;10(1):3177. doi: 10.1038/s41467-019-10758-0.
Bacteriorhodopsin (bR) is a light-driven proton pump. The primary photochemical event upon light absorption is isomerization of the retinal chromophore. Here we used time-resolved crystallography at an X-ray free-electron laser to follow the structural changes in multiphoton-excited bR from 250 femtoseconds to 10 picoseconds. Quantum chemistry and ultrafast spectroscopy were used to identify a sequential two-photon absorption process, leading to excitation of a tryptophan residue flanking the retinal chromophore, as a first manifestation of multiphoton effects. We resolve distinct stages in the structural dynamics of the all-trans retinal in photoexcited bR to a highly twisted 13-cis conformation. Other active site sub-picosecond rearrangements include correlated vibrational motions of the electronically excited retinal chromophore, the surrounding amino acids and water molecules as well as their hydrogen bonding network. These results show that this extended photo-active network forms an electronically and vibrationally coupled system in bR, and most likely in all retinal proteins.
细菌视紫红质（bR）是一种光驱动的质子泵。光吸收后的主要光化学事件是视黄醛发色团的异构化。在这里，我们使用自由电子激光的时间分辨晶体学来跟踪多光子激发的 bR 从 250 飞秒到 10 皮秒的结构变化。量子化学和超快光谱学用于识别顺序的双光子吸收过程，导致围绕视黄醛发色团的色氨酸残基的激发，作为多光子效应的第一个表现。我们解析了全反式视黄醛在光激发 bR 中高度扭曲的 13-顺式构象的结构动力学的不同阶段。其他活性位点亚皮秒重排包括电子激发的视黄醛发色团、周围的氨基酸和水分子以及它们的氢键网络的相关振动运动。这些结果表明，这个扩展的光活性网络在 bR 中形成了一个电子和振动耦合系统，很可能在所有的视蛋白中也是如此。
