Biophysical Studies of Metalloenzymes

智慧价值生物固氮--将氮气还原为两个摩尔氨(NH3/NH4+)，可用作植物养分--由金属酶--固氮酶催化。固氮酶的农学、经济和社会意义可以通过认识到，今天大约三分之二的人类人口的生活依赖于植物生长，而植物生长依赖于固氮酶产生的生物固定氮。另外三分之一依赖于工业哈伯-博世工艺的固氮，但这一工艺是世界能源使用的重要组成部分，需要大约1%的人类能源消耗。能否更有效地利用生物过程造福人类仍然是一个紧迫的问题，因此，必须了解生物体在常温常压下激活和裂解氮气的方法。本项目通过使用电子-核双共振(Endor)和电子自旋回波包络调制(ESEEM)光谱来表征固氮酶固氮过程中形成的催化中间体来解决这些问题。Endor/ESEEM研究独特地提供了有关底物结合/还原活性中心的电子性质的信息，并提供了关于金属结合底物、中间体和产品的详细结构信息。没有其他技术能提供这方面的信息。更广泛的影响与该项目相关的外展计划可以被视为(大致)一个金字塔。处于顶端的是对学科本身和研究界的智力/科学贡献。支持这些智力努力的是对博士后学者和研究生培养的贡献，不仅是为了这个项目，也是为了整个国家和世界。基础一级涉及鼓励本科生甚至高中生，特别是妇女和代表性不足的少数群体参与科学事业。

Intellectual MeritBiological nitrogen fixation - the reduction of N2 to yield two moles of ammonia (NH3/ NH4+) that are available as plant nutrient - is catalyzed by the metalloenzyme, nitrogenase. The agronomic, economic, and social significance of nitrogenase can be appreciated by recognizing that the lives of about two-thirds of today's human population depend on plant growth, which relies on biologically fixed nitrogen generated by nitrogenase. The other third depends on nitrogen fixation by the industrial Haber-Bosch process, but this process is a significant component in the world's energy usage, demanding approximately 1 percent of human energy consumption. Whether the biological process can be more effectively exploited for human benefit remains an urgent question, and thus it is imperative that an understanding be achieved of the means by which organisms manage to activate and cleave N2 at ambient temperature and pressure. This project is addressing these questions through the use of electron-nuclear double resonance (ENDOR) and electron spin-echo envelope modulation (ESEEM) spectroscopies to characterize catalytic intermediates that form during the process of nitrogen fixation by nitrogenase. ENDOR/ESEEM studies uniquely provide information about the electronic properties of the substrate-binding/reduction active site, and supply detailed structural information regarding metal-bound substrates, intermediates, and products. No other technique offers this information. Broader ImpactThe outreach program associated with this project can be viewed (roughly) as a pyramid. At the apex are intellectual/scientific contributions to the discipline itself, and to the research community. Supporting these intellectual endeavors are contributions to the training of post doctoral scholars and graduate students, not only for this project but throughout the country and the world. The foundation level involves the encouragement of undergraduates and even high-school students, especially of women and underrepresented minorities, to participate in the scientific enterprise.