Proton Transfer and Cofactor Function in Photosynthetic Reaction Centers

所有的生命都是基于化学反应和过程的一小部分，而这些反应和过程几乎是无限可能的。所选择的反应由生物大分子催化，使反应速率提高了许多数量级。这些催化剂绝大多数是被称为酶的蛋白质，其中许多都有小分子作为辅助因子，与化学反应密切相关。在生物能转化中，氧化还原（氧化还原）自由能转化为跨膜质子和电梯度。氧化还原化学是由多种有机和金属辅因子完成的，这些辅因子被结合它们的蛋白质赋予了非凡的特性。产生这些特性的蛋白质-辅因子相互作用与酶活性位点底物上的相互作用相同。由于氧化还原和光生物辅助因子的特殊光谱特性，呼吸、光合作用和甲烷生成的膜蛋白以惊人的特异性为研究生物化学催化的本质和定义质量提供了理想的系统。这个项目的重点是光合反应中心（RC），它以几乎100%的量子效率催化光驱动的电子转移。主要目的是阐明光激活电子传递给受体并稳定防止浪费的反反应的机制。在很大程度上，这是由于RC内伴随的电荷再分布，包括内部质子转移和溶液的净吸收。已知的RC结构，其丰富的光谱，以及其反应的光活化性质允许这些辅因子性质的起源，以分子结构的动力学和能量学来表征。在所有项目中，将研究化学和诱变扰动对能量学和动力学的影响。动力学和平衡结果将通过光学吸收光谱测定，通过延迟荧光和电位测定法测定自由能级，通过FTIR、x射线衍射和脉冲EPR光谱测定结构含义。更广泛的影响：这项研究的更广泛的影响来自于所采用的非常多样化的方法，它为年轻科学家提供了一个特殊的培训环境，具有实质性的多学科成分。这项工作有助于对全球和人类影响过程的实际理解，包括替代能源、生物燃料和全球变暖。无论是在高中还是大学，它们都是教学、指导和激励学生的坚实基础。

All of life is based on a small subset of chemical reactions and processes, among the almost infinite number of possible ones. The selected reactions are catalyzed by biological macromolecules that speed up the reaction rates by very many orders of magnitude. The vast majority of these catalysts are proteins known as enzymes, and many of these have small molecules as cofactors that are intimately involved in the chemistry. In biological energy conversions, oxidation-reduction (redox) free energy is converted into transmembrane proton and electrical gradients. The redox chemistry is performed by diverse organic and metal cofactors that are invested with extraordinary properties by the proteins that bind them. The protein-cofactor interactions that yield these properties are the same as those that operate on a substrate in an enzyme active site. Because of the exceptional spectroscopic attributes of redox and photobiological cofactors, the membrane proteins of respiration, photosynthesis and methanogenesis provide ideal systems for studying the essential and defining quality of biochemistry - catalysis with astonishing specificity. This project focuses on the photosynthetic reaction center (RC), which catalyzes a light-driven electron transfer with almost 100% quantum efficiency. The primary aim is to elucidate the mechanisms whereby the photo-activated electron is delivered to the acceptor and stabilized against wasteful backreaction. In large part, this is due to accompanying charge redistributions within the RC, including internal proton transfers and net uptake from solution. The known structure of the RC, its rich spectroscopy, and the light-activatable nature of its reactions allow the origins of these cofactor properties to be characterized in terms of the dynamics and energetics of the molecular structure. In all projects, the impact of chemical and mutagenic perturbations on energetics and kinetics will be studied. Kinetic and equilibrium consequences will be determined by optical absorption spectroscopy, free energy levels by delayed fluorescence and by potentiometry, and structural implications by FTIR, X-ray diffraction and pulsed EPR spectroscopy.Broader impacts: The broader impacts of this research derive from the very diverse methodologies employed, which provide an exceptional training environment for young scientists, with a substantially multidisciplinary component. This work contributes to the practical understanding of processes with global and human impact, including alternative energy sources, biofuels and global warming. They form a strong basis for teaching, mentoring and motivating students in the classroom, at the high school as well as college level.