Soft X-ray Magnetic Circular Dichroism of Metalloproteins

X射线磁性圆二色性（XMCD）是一种新的实验方法， 具有巨大潜力技术， 金属簇和复杂蛋白质的表征。 博士 Cramer建议进行有史以来第一次XMCD测量， 仔细选择的顺磁性过渡金属络合物， 将实验结果与最近开发的 理论模拟程序。XMCD实验将在 在具有已知金属位点的小蛋白质上进行，结果 与其他方法如穆斯堡尔谱和电子顺磁共振的数据进行了比较。 建立了XMCD的实验和理论基础， 他将把这项技术应用于磁性和结构问题 关于金属酶固氮酶，氢化酶， 光系统II。 为了进行这些实验，他将使用圆偏振 从电子存储器中以同步辐射形式发射的软X射线 环，如国家同步加速器光源。 样本将 被放置在超导磁体的强磁场中。 光吸收将通过透射率直接测量。 方法，并间接使用样品光电流或 荧光检测技术。 固氮酶中金属的位点特异性表征， 氢化酶和光系统II将允许更好地理解和 合成模拟其重要的催化活性。 的 这项新技术的发展还将提供 生物无机社区与一个新的工具，磁性和网站- 具体的表征，和XMCD技术将是 通常适用于几乎所有顺磁性过渡金属 配合物

X-ray magnetic circular dichroism (XMCD) is a new experimental technique with tremendous potential for site-specific characterization of metals in clusters and complex proteins. Dr. Cramer proposes to conduct the first-ever XMCD measurements on carefully selected paramagnetic transition metal complexes, and to compare the experimental results with recently developed theoretical simulation programs. XMCD experiments will then be conducted on small proteins with known metal sites, and the results compared with data from other methods such as Mossbauer and EPR. With the experimental and theoretical basis of XMCD established, he will apply the technique to magnetic and structural questions about metal centers in the metalloenzymes nitrogenase, hydrogenase, and photosystem II. To conduct these experiments, he will employ circularly-polarized soft x-rays emitted as synchrotron radiation from electron storage rings such as the National Synchrotron Light Source. Samples will be placed in the strong magnetic field of a superconducting magnet. Photoabsorption will be measured directly by the transmission method on thin films, and indirectly using sample photocurrent or fluorescence detection techniques. Site-specific characterization of metals in nitrogenase, hydrogenase, and photosystem II will allow better understanding and synthetic modelling of their important catalytic activities. The development of this new technique will also provide the bioinorganic community with a new tool for magnetic and site- specific characterization, and the XMCD techniques will be generally applicable to nearly all paramagnetic transition metal complexes.