Quintanar Liliana, Rivillas-Acevedo Lina
Departamento de Química, Centro de Investigación y de Estudios Avanzados, Mexico City, Mexico.
Methods Mol Biol. 2013;1008:267-97. doi: 10.1007/978-1-62703-398-5_10.
Metal ions play a wide range of important functional roles in biology, and they often serve as cofactors in enzymes. Some of the metal ions that are essential for life are strongly associated with proteins, forming obligate metalloproteins, while others may bind to proteins with relatively low affinity. The spectroscopic tools presented in this chapter are suitable to study metal ion-protein interactions. Metal sites in proteins are usually low symmetry centers that differentially absorb left and right circularly polarized light. The combination of electronic absorption and circular dichroism (CD) in the UV-visible region allows the characterization of electronic transitions associated with the metal-protein complex, yielding information on the geometry and nature of the metal-ligand interactions. For paramagnetic metal centers in proteins, electron paramagnetic resonance (EPR) is a powerful tool that provides information on the chemical environment around the unpaired electron(s), as it relates to the electronic structure and geometry of the metal-protein complex. EPR can also probe interactions between the electron spin and nuclear spins in the vicinity, yielding valuable information on some metal-ligand interactions. This chapter describes each spectroscopic technique and it provides the necessary information to design and implement the study of metal ion-protein interactions by electronic absorption, CD, and EPR.
金属离子在生物学中发挥着广泛的重要功能作用，并且它们常常作为酶的辅助因子。一些对生命至关重要的金属离子与蛋白质紧密结合，形成专一性金属蛋白，而其他一些金属离子可能以相对较低的亲和力与蛋白质结合。本章介绍的光谱学工具适用于研究金属离子与蛋白质的相互作用。蛋白质中的金属位点通常是低对称中心，它们对左旋和右旋圆偏振光有不同的吸收。紫外 - 可见区域的电子吸收和圆二色性（CD）相结合，可以表征与金属 - 蛋白质复合物相关的电子跃迁，从而获得有关金属 - 配体相互作用的几何结构和性质的信息。对于蛋白质中的顺磁性金属中心，电子顺磁共振（EPR）是一种强大的工具，它可以提供有关未成对电子周围化学环境的信息，这与金属 - 蛋白质复合物的电子结构和几何结构有关。EPR还可以探测附近电子自旋与核自旋之间的相互作用，从而获得有关一些金属 - 配体相互作用的有价值信息。本章描述了每种光谱技术，并提供了通过电子吸收、CD和EPR设计和开展金属离子 - 蛋白质相互作用研究所需的信息。
