Excited state dynamics in the early stages of the bR and Rh photocycle

视网膜蛋白质复杂功能的第一步是吸收光，随后蛋白质内发色团的异构化。该过程的快速性、高效性和选择性直接关系到结合袋分子排列的优化，不同的因素限制了对这些体系的理论描述。首先，反应发生在激发电子态，量子化学计算只有在高计算成本的情况下才能提供准确的解决方案。其次，视网膜蛋白质的动力学被认为发生在一个强耦合的势能面上。这使得必须使用先进的非绝热分子动力学方案，以获得反应时间尺度和量子产率的实际值。最后，蛋白质与生色团相互作用的复杂性要求在活性部位的结构模型中包含很大一部分结合口袋，这涉及到很高的计算工作量。在这个项目的前半部分，我们开发了解决这些具体问题的方法，并可在后半部分用于分析bR和Rh光循环的早期阶段。这些计算将提供结构信息和光循环中的中间体，并导致复杂的视网膜光反应的详细图像。

The very first step in the complex function of the retinal proteins is the absorption of light which is followed by an isomerization of the chromophore within the protein. The high speed, efficiency and selectivity of the process are directly related to the optimized molecular arrangement of the binding pocket.Different factors have so far limited the theoretical description of theses systems. First, the reaction occurs in an excited electronic state for which quantum chemical calculations provide accurate solutions only at high computational cost. Second, the dynamics in the retinal proteins are believed to happen an strongly coupled potential energy surfaces. This makes the use of advanced nonadiabatic molecular dynamics schemes mandatory in order to obtain realistic values for reaction time scales and quantum yields. Finally, the complexity of the protein interaction with the chromophore requires the inclusion of a large part of the binding pocket in structural models for the active site, which involves a high computational effort. In the first half of this project we developed methods which cope with these specific problems and can be used in the second half to analyze the early stages of the bR and Rh photocycies. These calculations will provide structural Information an intermediates in the photocycle and lead to a detailed picture of the complex retinal photoreaction.