Bacterial Reaction Centers With New Photochemical Properties

在所有的光合作用系统中，主要的能量传递事件是光诱导色素-蛋白质复合体中电荷分离态的产生。尽管不同生物体的具体途径不同，但总体模式是非常保守的，对这些过程的理解是当前设计模拟光合作用过程的人工系统的基础。球形红杆菌的反应中心作为光系统II的模型是有用的，以前的工作是将氧化还原活性的锰辅助因子结合到反应中心的位置上，位置类似于光系统II的锰簇。该项目的第一个具体目标是表征反应中心中结合的锰和其他新的金属辅助因子的性质。将利用各种光谱技术来确定金属辅因子的结构性质、电子结构和电子转移性质，为理解金属结合的特异性、控制金属活性的因素以及涉及金属辅因子的反应如何由蛋白质相互作用控制提供基础。第二个具体目标是设计具有多核锰簇的蛋白质。簇的组装将通过三个独立的途径进行：一种半合成方法，其中各种锰化合物将结合到蛋白质上，应用光系统II的锰簇的自组装原理，以及引入新的配体来结合双核和四核锰簇。新的锰辅助因子的加入应该有助于阐明金属簇与蛋白质结合的分子要求。关于含有新的金属辅因子的电子转移蛋白的研究，应该为设计能够光驱动的金属催化的蛋白质提供基础。研究目标的实现将对理解光合作用和开发太阳能设备产生影响。更广泛的影响该项目为本科生和研究生提供多学科培训，并通过合作提供国际接触。许多项目概念，特别是光合作用在能源利用中的作用和用于研究反应中心的光谱技术基础，将包括在为不同背景的学生开发的课程中，以及由首席研究员编写的本科教育教科书。

In all photosynthetic systems, the primary energy transduction event is the light-induced generation of a charge-separated state in a pigment-protein complex. Although the specific pathways vary among organisms, the general pattern is remarkably conserved, and an understanding of these processes serves as the basis for current designs of artificial systems that mimic the photosynthetic process. The usefulness of the reaction center from Rhodobacter sphaeroides as a model for photosystem II is illustrated by previous work in which a redox-active Mn cofactor was bound to the reaction center at a location analogous to that of the Mn cluster of photosystem II. The first specific aim of the project is to characterize the properties of the bound Mn and other new metal cofactors in the reaction center. A wide variety of spectroscopic techniques will be utilized to determine the structural properties, the electronic structure of the metal cofactor, and the electron transfer properties, providing the basis for understanding the specificity for metal binding, the factors that control the activity of the metal, and how reactions involving metal cofactors are controlled by protein interactions. The second specific aim is to design proteins with multinuclear Mn clusters. The assembly of clusters will be approached by three independent avenues: a semi-synthetic method in which a variety of Mn compounds will be bound to the protein, the application of the self-assembly principles of the Mn cluster of photosystem II, and the introduction of new ligands for the binding of binuclear and tetranuclear Mn clusters. The incorporation of new Mn cofactors should shed light into the molecular requirements for the binding of metal clusters to proteins. The insight gained regarding electron transfer proteins with new metal cofactors should provide the foundation for the design of proteins capable of light-driven metal-based catalysis. Achievement of the research goals should have an impact on understanding photosynthesis and the development of solar-energy devices. Broader impactsThe project provides multidisciplinary training for undergraduate and graduate students and international exposure through collaborations. Many project concepts, notably the role of photosynthesis in energy utilization and the fundamentals of spectroscopic techniques used to study reaction centers, will be included in the development of courses for students of different backgrounds, as well as a textbook for undergraduate education authored by the principal investigator.