Institute of Physical and Theoretical Chemistry, Johann Wolfgang Goethe-University Frankfurt, Frankfurt am Main, Germany.
J Am Chem Soc. 2013 May 8;135(18):6968-76. doi: 10.1021/ja400554y. Epub 2013 Apr 29.
The primary reaction dynamics of channelrhodopsin-2 was investigated using femtosecond vis-pump/mid-IR probe spectroscopy. Due to the fast deactivation of the excited state in channelrhodopsin-2, it is possible to observe the direct impact of retinal isomerization on the protein surrounding. We show that the dominant negative band at 1665 cm(-1) tentatively assigned to an amide I vibration is developed with a time constant of 0.5 ps. Also a variety of side-chain vibrations are formed or intensified on this time scale. The comparison of the light-induced FT-IR spectra of channelrhodopsin-2 in H2O and D2O at 80 K enabled us to tentatively identify the contribution of Arg side chain(s). The subsequently observed decay of nearly the whole difference pattern has a particularly high impact on the C═C and C═N stretching vibrations of the retinal. This suggests that the underlying mechanism describes a cooling process in which the excess energy is redirected toward the retinal surrounding, e.g., the protein and functional water molecules. The pronounced protein contributions in comparison to other rhodopsins point to a very efficient energy redistribution in channelrhodopsin-2.
使用飞秒可见泵浦/中红外探测光谱研究了通道蛋白视紫红质-2 的主要反应动力学。由于通道蛋白视紫红质-2 中激发态的快速失活，有可能观察到视黄醛异构化对周围蛋白质的直接影响。我们表明，在 1665 cm(-1)处的主导负带暂定分配给酰胺 I 振动，其时间常数为 0.5 ps。同样，在这个时间尺度上形成或增强了各种侧链振动。在 80 K 下，比较了通道蛋白视紫红质-2 在 H2O 和 D2O 中的光致 FT-IR 光谱，使我们能够暂定识别 Arg 侧链的贡献。随后观察到的几乎整个差谱的衰减对视网膜的 C═C 和 C═N 伸缩振动有特别大的影响。这表明，基础机制描述了一个冷却过程，其中多余的能量重新定向到视网膜周围，例如蛋白质和功能水分子。与其他视蛋白相比，明显的蛋白质贡献表明通道蛋白视紫红质-2 中能量的再分配非常有效。
