VIBRATIONAL STUDIES OF METAL CLUSTERS IN PROTEINS

锰是一种必需的微量元素在生物体中执行 分子氧的各种氧化还原转化。 一个新的计划将是 开发的目的是探索结构和反应性的基本问题， 生物体系锰活性中心的光谱研究 方法，特别是共振拉曼（RR）光谱法。 初期目标 将包括超氧化物歧化酶（SOD）的单核Mn（III）位点 和双核非血红素Mn-过氧化氢酶， 结构已经提出。 我们的方法是 高质量的蛋白质和明智选择的模型的RR谱 配合物，与援助的低温拉曼技术和可变 激发波长，并记录尽可能多的频率和同位素 尽可能的改变。 然后将执行正常模式计算， 基于结构表征的Mn仿生模型系统， 目的是发展物理上合理的力场， 精确地再现观察到的频率和同位素位移， 详细了解被监测的振动模式的性质。 RR和溶液FT-IR光谱将用于阐明 超氧化物单核金属中心的阴离子相互作用模式 通过探测Cu，Zn-，Fe-和 含Mn的SOD-叠氮化物加合物。 精氨酸残基（Arg 141)叠氮键的化学修饰和磷酸盐加成 振动频率将被用来提供洞察的作用， Arg 141参与SOD催化过程。 对自然的理解 被监测的振动模式将允许确定结构 这些重要酶的特征，并建立蛋白质结构 与其活性金属位点的化学性质相关的变化。

Manganese is an essential trace element in living organisms to perform various redox transformations of dioxygen. A new program will be developed to explore fundamental questions of structure and reactivity at manganese active sites of biological systems by using spectroscopic methods, particularly resonance Raman (RR) spectroscopy. Initial targets will include the mononuclear Mn(III) site of superoxide dismutases(SODs) and dinuclear non-heme Mn-catalases for which several plausible structures have been proposed. Our approach will be to obtain high-quality RR spectra of proteins and of judiciously chosen model complexes, with the aid of low-temperature Raman techniques and variable excitation wavelengths, and to record as many frequencies and isotope shifts as possible. Normal mode calculations will then be carried out, based on structurally characterized Mn biomimetic model systems, with the aim of developing physically plausible force fields capable of reproducing the observed frequencies and isotope shifts accurately and to understand in detail the nature of vibrational modes being monitored. The RR and solution FT-IR spectroscopies will be used to elucidate the anion interaction modes at the mononuclear metal sites of superoxide dismutases by probing ligand vibrations of the Cu,Zn-, Fe-, and Mn-containing SOD-azide adducts. The effects of arginine residue (Arg 141) chemical modification and phosphate addition on azide-bound vibrational frequencies will be used to provide insights into the role of Arg 141 in the SOD catalytic process. An understanding of the nature of the vibrational modes being monitored will allow to pin down structural features of these important enzymes, and to establish protein structural changes associated with the chemistry of their active metal sites.