Co(II) Radical Pair Dynamics in B12 Enzyme Catalysis

描述（由申请人提供）：拟议研究的长期目标是阐明在金属-自由基对生成和偶联自由基介导反应的背景下控制酶催化的基本分子原理。这一目标将通过对鼠伤寒沙门氏菌中辅酶B12（腺苷钴胺素）依赖性酶乙醇胺解氨酶的生化和物理综合研究来实现。我们开发了脉冲电子顺磁共振（EPR）光谱的新方法、新软件和新硬件。结合生物化学技术，我们开发了低温系统和时间分辨EPR方法，使开创性的实验工作能够在一步分辨率下直接解决乙醇胺解氨酶中共价键断裂/键形成反应。总的目标是定义指导反应的自由能格局，确定起源并描述蛋白质和耦合溶剂波动在这一格局上推动系统的作用，并解决构成自由能格局的埃级分子结构。该项目提出了一种酶催化的“构型催化”模型，并试图建立自由基重排作为一种范式，用于定义酶反应中化学步骤的景观和蛋白质-溶剂运动贡献。溶剂结构和动力学对酶反应的贡献也通过一套EPR光谱和弛豫技术来解决。研究结果将影响生物医学和人类健康的分子方法，包括抗微生物治疗，催化剂、抑制剂和生物纳米室的合理设计，以及自由基反应的控制。

DESCRIPTION (provided by applicant): The long-term goal of the proposed research is to elucidate fundamental molecular principles that govern catalysis in enzymes, in the context of metal-radical pair generation and coupled radical-mediated reactions. This goal will be enacted through a comprehensive program of biochemical and physical studies of the coenzyme B12 (adenosylcobalamin) - dependent enzyme, ethanolamine ammonia-lyase, from Salmonella typhimurium. We have developed new methods, software and hardware for pulsed-electron paramagnetic resonance (EPR) spectroscopy. In conjunction with biochemical techniques, we have developed low-temperature systems and time- resolved EPR approaches that enable pioneering experimental efforts that address, directly, covalent bond- breaking/bond-making reactions in ethanolamine ammonia-lyase at single-step resolution. The general aims are to define the free energy landscape that guides the reactions, identify the origins and characterize the roles of the protein and coupled solvent fluctuations that propel the system over this landscape, and resolve the Angstrom-scale molecular structures that frame the free energy landscape. The projects develop a proposed "configurational catalysis" model for enzyme catalysis, and seek to establish the radical rearrangement as a paradigm for defining landscape and protein-solvent motional contributions to chemical steps in enzyme reactions. Contributions of solvent structure and dynamics to the enzyme reactions are also addressed by a suite of EPR spectroscopic and relaxation techniques. The outcomes of the research will impact molecular approaches in biomedicine and human health, including anti- microbial therapies, rational design of catalysts, inhibitors, and bio-nanocompartments, and control of free radical reactions.