Functional LnFe-Nx Models of Biological N2 Fixation

生物 N2 固定的功能性 LnFe-Nx 模型

• 批准号: 8113712
• 负责人: Jonas C Peters
• 金额: $ 22.94万
• 依托单位: CALIFORNIA INSTITUTE OF TECHNOLOGY
• 依托单位国家: 美国
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-02-01 至 2011-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8113712
• 关键词: Functional; LnFe; Nx; Models; Biological

DESCRIPTION (provided by applicant): Nitrogenase (N2ase) is a metalloenzyme that mediates biological nitrogen fixation and as such is essential to sustained life. Understanding the chemical mechanism by which N2ase-mediated nitrogen reduction occurs is therefore of general interest. The proposed program is to study biomimetic LnFe-Nx model complexes that will help to evaluate a mechanistic scheme that stresses a single Fe-Nx binding site in the FeMo cofactor (FeMoco) of N2ase. The experimental design focuses on functional rather than structural models of the FeMoco. Low molecular weight LnFe-Nx complexes will be developed to isolate a single iron site in either a tetrahedral or a trigonal bipyramidal geometry while at the same time preserving one binding site to accommodate dinitrogen and various other Nx functionalities. The Ln donor scaffolds will incorporate phosphorous and/or sulfur donor groups to render the LnFe species sufficiently electron-rich to bind relatively inert N2. By analogy to the mode of biocatalytic O2 reduction (FeII-O2 + 2 e-+ 2 H+ -> FeIV= O + H2O), a mechanistic sequence for N2 reduction that proceeds through a terminal nitride intermediate (Fel-N2 + 3 e-+ 3 H+ -> FeIV=(N + NH3) will be explored. To this end each of the critical intermediates envisaged for the complete cycle will be generated and studied. These intermediates will include Fel-N2, Fell-N=NH, Felll=N-NH2, FeIV = N, FeIII(NH, FeII-NH2, and Fel-NH3 species. Of further interest will be to understand how the local geometry and electronic structure of the LnFe-Nx species control their relative stabilities and reactivity patterns at their Fe-Nx linkages. The intent is to then use this knowledge to further design model systems that can facilitate catalytic N2ase activity. To accomplish these collective goals will require the physical and theoretical characterization of each type of Fe-Nx species, a mechanistic understanding of each of the stepwise transformations that pertain to the proposed cycle, and exploratory catalytic studies that will expose promising model systems that successfully mediate nitrogen fixation.

描述（由申请人提供）：固氮酶（N2酶）是一种介导生物固氮的金属酶，因此对持续生命至关重要。因此，了解N2酶介导的氮还原发生的化学机制具有普遍意义。拟议的计划是研究仿生LnFe-Nx模型复合物，这将有助于评估一个机械方案，强调一个单一的Fe-Nx结合位点的FeMo辅因子（FeMoco）的N2酶。实验设计侧重于FeMoco的功能模型，而不是结构模型。将开发低分子量LnFe-Nx复合物以在四面体或三角双锥几何结构中分离单个铁位点，同时保留一个结合位点以容纳二氮和各种其他Nx功能。Ln供体支架将结合磷和/或硫供体基团以使LnFe物质足够富电子以结合相对惰性的N2。通过类比生物催化O2还原的模式（FeII-O2 + 2 e-+ 2 H+ -> FeIV= O + H2O），将探索通过末端氮化物中间体（FeII-N2 + 3 e-+ 3 H+ -> FeIV=（N + NH3））进行的N2还原的机理序列。为此，将生成并研究整个循环中设想的每种关键中间体。这些中间体将包括Fe 11-N2、Fe 11-N =NH、Fe 11 = N-NH 2、Fe 14 = N、Fe 13（NH）、Fe 11-NH 2和Fe 11-NH3物质。进一步的兴趣将是了解如何的局部几何形状和电子结构的LnFe-Nx物种控制其相对稳定性和反应模式在其Fe-Nx连接。其目的是使用这些知识来进一步设计可以促进催化N2酶活性的模型系统。为了实现这些共同的目标，将需要每种类型的Fe-Nx物种的物理和理论表征，与所提出的循环有关的每个逐步转化的机械理解，以及探索性催化研究，这些研究将暴露成功介导固氮的有前途的模型系统。