EPR STUDIES OF DINUCLEAR METAL CLUSTERS IN PROTEINS

含有双核金属团簇的蛋白质对生命的许多基本过程至关重要，包括DNA合成、氧化磷酸化、甲烷氧化、脂肪酸降解、过氧化物解毒、氧和电子传递。此外，催化自裂反应的核酶核酶被认为在活性位点含有双核金属簇。双核金属团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，特别适合探测这些金属团簇。EPR光谱长期以来一直是研究在许多蛋白质活性中心发现的过渡金属离子的宝贵工具。许多具有重要生物学意义的金属，如钒、铬、锰、铁、钴、镍、铜和钼，都有不成对的电子，产生新的电子自旋和由此产生的磁矩。EPR光谱能够测量这一时刻，因此为这些蛋白质的活性位点提供了微观探针。多年来，EPR光谱学一直局限于金属蛋白中具有奇数未配对电子的研究。然而，在过去的几年里，我们的工作已经大大拓宽了EPR光谱的应用范围，包括对具有偶数未配对电子的金属蛋白的定量分析。特别是，具有重要生物学意义的双核金属团簇的氧化态主要是具有偶数电子的状态。

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.