PULSED EPR STUDIES OF NICKEL MODEL COMPLEXES

本申请中提出的研究的长期目标是 表征镍的两个重要类别的连接结构 的镍酶，并进一步发展脉冲EPR技术， 电子自旋回波包络调制和电子自旋回波 检测ENDOR光谱用于表征顺磁性 生物系统的中心。 具体实验旨在实现 第一个目标涉及Ni（III）和Ni（I）的模型配合物的研究， 使用cw-EPR，cw-ENDOR，ESEEM和ESE的生物相关结构， ENDOR光谱。 Ni（III）肽模型配合物将被研究 使用ESEEM、cw-和ESE-ENDOR方法获得磁耦合 14 N、2 H和1H的参数和耦合张量取向， 配体，以确定这些磁性参数是如何与 结构 这些数据将提供必要的背景， 解释已发布和正在进行的ESE和ENDOR的结果 Ni-Fe氢化酶中镍中心的研究。 镍（I） 辅因子F430的衍生物，被认为在甲烷中发挥关键作用 产甲烷细菌的生产，也将研究使用脉冲-和 cw-EPR技术 这里，配体超精细耦合常数和张量 定向将产生关于轴向结合的详细信息 辅因子的性质和辅因子减少的后果， 与corphin大环扭曲和“起皱”的变化有关。 这些 特性被认为是定义独特化学的关键要素 及其在甲基还原酶中的催化功能。 过程中 在本研究中，将开发ESE-ENDOR方法， 与cw-ENDOR的能力直接比较。 此外，本发明还提供了一种方法， 将改进现有的数据分析方法。 因为金属酶 用作许多重要氧化还原反应的催化剂 在某些阶段涉及顺磁离子的生物系统中 在这些过程中，本研究的结果将提供相关的 信息和增强的光谱工具的调查，许多 与健康有关的问题。

The long-range objectives of the research proposed in this application are to characterize the ligation structures of nickel in two important classes of nickel enzymes and to further develop the pulsed-EPR techniques of electron spin-echo envelope modulation (ESEEM) and electron spin-echo detected ENDOR spectroscopy for the characterization of paramagnetic centers in biological systems. The specific experiments aimed at achieving the first goal involve the study of Ni(III) and Ni(I) model complexes of biologically relevant structure using cw-EPR, cw-ENDOR, ESEEM, and ESE- ENDOR spectroscopies. Ni(III) peptide model complexes will be studied using ESEEM, cw- and ESE-ENDOR methods to obtain magnetic coupling parameters and coupling tensor orientations for 14N, 2H, and 1H containing ligands to determine how these magnetic parameters are related to structure. These data will provide the necessary background for interpreting the results of published and ongoing ESE and ENDOR investigations of the nickel center in Ni-Fe hydrogenases. Ni(I) derivatives of cofactor F430, thought to play a key role in methane production by methanogenic bacteria, will also be studied using pulsed- and cw-EPR techniques. Here, ligand hyperfine coupling constants and tensor orientations will yield detailed information concerning the axial bonding properties of the cofactor and the consequences of cofactor reduction as related to changes in corphin macrocycle distortion and "puckering". These properties are thought to be key elements in defining the unique chemistry of F430 and its catalytic function in methyl reductases. During the course of this research, ESE-ENDOR methodology will be developed and its capabilities compared directly with those of cw-ENDOR. In addition, current methods of data analysis will be improved. Because metalloenzymes serve as catalysts for a number of essential oxidation-reduction reactions in biological systems with paramagnetic ions being involved at some stage in these processes, the results of this research will provide pertinent information and enhanced spectroscopic tools for the investigation of many health-related problems.