QM/MM calculations of retinal protein excited states: Investigating the mechanisms of color tuning

虽然蛋白质bR和Rh含有相同的发色团，即质子化的视网膜希夫碱，但与分离视网膜的光谱相比，不同蛋白质基质中的吸收最大值移位不同（copsin移位）。这是由于发色团与不同蛋白质口袋中的各种氨基酸的相互作用。此外，蛋白质中的光异构化在速度、反应配位和量子产率方面与溶液中的光异构化有很大的不同。在这个项目中，我们研究了蛋白质在电子激发态下与发色团的特定相互作用。这些研究现在是可行的，因为直到最近才有足够分辨率的各种中间体的晶体结构，并且已经发展了适当的理论方法。本研究的目的是研究蛋白质口袋中氨基酸残基的空间和静电相互作用对发色团光学性质的影响。此外，在光循环过程中，由于蛋白质重排和氨基酸序列突变引起的光谱变化将被研究。

Although the proteins bR and Rh contain the same chromophore, a protonated retinal Schiff base, the absorption maxima are shifted differently in the different protein matrices compared to the spectrum of the isolated retinal (¿copsin shift ). This is due to the interaction of the chromophore with various amino acids in the different protein pockets. Further, the photoisomerization in the protein differs significantly from that in solution, concerning its velocity, the reaction coordinate and quantum yield.In this project we investigate the specific interactions of the proteins with the chromophore in its electronically excited state. These investigations are now feasible, since only recently crystal structures of various intermediates with sufficient resolution became available, and appropriate theoretical methods have been developed. The goal of this proposal is to investigate the influence of steric and electrostatic interactions of amino acid residues from the protein pocket an the optical properties of the chromophore. Further, the spectral changes due to rearrangement of the protein during the photo cycle and the changes due to mutations of the amino acid sequence will be investigated.