Protein Dynamics in Electron Transfer

本项目结合分子动力学模拟和实验测量，建立了紫色非硫细菌Rhodobacter sphaeroides光合作用电子传递反应中心的动力学模型。 目前对该系统的模拟表明，缓慢的集体蛋白质模式参与介导这些反应是关键，因此，在反应期间可用的重组能量的量在很大程度上取决于反应的时间尺度，特别是当从皮秒移动到纳秒时。在这里，一个理论小组和一个实验小组联手探索蛋白质动力学如何参与平衡两个竞争的电子转移反应，这两个反应对光合作用中的太阳能转化至关重要。 首先是一个生产性的电子转移反应，发生在200 ps的时间尺度上从细菌脱镁叶绿素中间体的醌。 第二种是竞争性的非生产性复合反应，其中电子在10-20 ns的时间尺度上返回到原始电子供体。 模拟和测量将作为这两个反应的驱动力和温度的函数进行，并直接进行比较，目的是了解自然界如何优化蛋白质结构和动力学，以促进生产性光合作用功能。 一系列的表面电荷突变体和不同的pH值将进行调查，测试的概念，即在蛋白质/水界面的电荷分布控制的初始和最终状态的电位表面的形状，如模拟所建议的。 此外，内部突变，认为改变潜在的表面之间的位移，也将进行调查。最终目标是提供定量预测生化反应动力学和相关功能的蛋白质结构在这个复杂的生物系统的能力。 发展一个定量的，基于结构的光合反应中心的结构，动力学和功能之间的关系的模型将是广泛的价值。 在这方面，反应中心代表了一个“分子实验室”，具有高分辨率的结构数据和用于相当详细地监测电子转移的固有光学探针。该项目将支持梅萨高中生物技术学院的学生在遗传操纵和光合细菌光谱探测的基础上发展一种完整的参与性学习经验。 这将涉及教师培训在亚利桑那州立大学实验室在一个夏天，然后PI直接与教师和学生在学院工作，在随后的几年中执行的活动。 在过去的5年里，PI非常积极地参与了本科生的指导工作，在实验室里有25名本科生。

This project integrates molecular dynamic simulation and experimental measurement to develop a dynamic model for photosynthetic electron transfer in reaction centers of the purple nonsulfur bacterium, Rhodobacter sphaeroides. Current simulations on this system have suggested that the involvement of slow, collective protein modes in mediating these reactions is key, and as a result, the amount of reorganization energy available during a reaction is profoundly dependant on the time scale of the reaction, particularly as one moves from picoseconds to nanoseconds. Here, a theoretical group and an experimental group have joined forces to explore how proteins dynamics is involved to balance two competing electron transfer reactions that are critical to solar energy conversion in photosynthesis. The first is a productive electron transfer reaction that takes place on the 200 ps timescale from a bacteriopheophytin intermediate to a quinone. The second is the competing unproductive recombination reaction in which the electron returns back to the original electron donor on the 10-20 ns time scale. Simulations and measurements will be performed as a function of the driving force and temperature for these two reactions and compared directly, the goal being to understand how Nature has optimized protein structure and dynamics to promote productive photosynthetic function. A series of surface charge mutants and different pH's will be investigated, testing the concept that that the charge distribution at the protein/water interface controls the shape of the initial and final state potential surfaces, as suggested by simulation. In addition, internal mutations, thought to alter the displacement between potential surfaces, will also be investigated. The ultimate objective is to provide the capability to quantitatively predict biochemical reaction dynamics and associated function from protein structure in this complex biological system. The development of a quantitative, structure-based model of the relationship between structure, dynamics and function in the photosynthetic reaction center would be broadly valuable. The reaction center in this respect represents something of a "lab on a molecule" with high resolution structural data and the inherent optical probes for monitoring electron transfer in considerable detail. The project will support the development of a complete, participatory learning experience for the students in the Mesa High School Biotechnology Academy, based on genetic manipulation and spectroscopic probing of photosynthetic bacteria. This will involve both teacher training in the ASU laboratories during one summer and then PIs working directly with the teachers and students in the academy to perform the activity during the subsequent years. The PIs are very heavily involved in undergraduate mentoring having had 25 undergraduates in the lab during the last 5 years.