EPR STUDIES OF DINUCLEAR METAL CLUSTERS IN PROTEINS

含有双核金属簇的蛋白质对生命的许多基本过程都是必不可少的，包括DNA合成、氧化磷酸化、甲烷氧化、脂肪酸降解、过氧化氢解毒以及氧和电子传递。此外，催化自身切割反应的核酶被认为在活性部位含有一个双核金属簇。对双核金属簇的光谱研究有助于我们在原子水平上理解这些酶和蛋白质的功能。我们开发了新的光谱仪器和定量方法，特别适合于探测这些金属团簇。电子顺磁共振波谱长期以来一直是研究存在于许多蛋白质活性中心的过渡金属离子的有价值的工具。许多具有生物重要性的金属，如钒、铬、锰、铁、钴、镍、铜和钼，都有未配对的电子，从而产生新的电子自旋和产生的磁矩。EPR光谱能够测量这一时刻，因此为这些蛋白质的活性部位提供了一个微观探针。多年来，EPR光谱学一直局限于对金属蛋白质中含有奇数个未配对电子的金属的研究。然而，我们在过去几年的工作显著扩大了EPR光谱的应用范围，包括对具有偶数个未配对电子的金属蛋白的定量分析。特别是，具有主要生物学意义的双核金属团簇的氧化态是主要具有偶数个电子的状态。

Proteins which contain dinuclear metal clusters are essential for many basic processes of life, including DNA synthesis, oxidative phosphorylation, methane oxidation, fatty acid degradation, peroxide detoxification, and oxygen and electron transport. In addition, the nucleic enzyme ribozyme, which catalyses a self cleavage reaction, is believed to contain a dinuclear metal cluster at the active site. Spectroscopic studies of dinuclear metal cluster contribute to our understanding of the function of these enzymes and proteins at an atomic level. We have developed new spectroscopic instrumentation and quantitative methodologies specifically suited to probe these metal cluster. EPR spectroscopy has long been a valuable tool for the study of the transition-metal ions that are found in the active centers of many proteins. Many metals of biological importance such as vanadium, chromium, manganese, iron, cobalt,, nickel, copper, and molybdenum, have unpaired electrons that give rise to a new electronic spin and a resultant magnetic moment. EPR spectroscopy is capable of measuring this moment and therefore provides a microscopic probe for the active sites of these proteins. For many years, EPR spectroscopy has been limited to studies of metalloproteins have an odd number of unpaired electrons in at the metal. However, our work over the past years has significantly broadened the range of applications for EPR spectroscopy to include quantitative analysis of metalloproteins with an even number of unpaired electrons. In particular, the oxidation states of dinuclear metal clusters that are of main biological importance, are states that predominantly have an even number of electrons.