Nesmelov Yuri E, Thomas David D
Department of Physics and Optical Science, University of North Carolina, 9201 University City Boulevard, Charlotte, NC 28223, USA.
Biophys Rev. 2010 May;2(2):91-99. doi: 10.1007/s12551-010-0032-5.
Multifrequency electron paramagnetic resonance (EPR), combined with site-directed spin labeling, is a powerful spectroscopic tool to characterize protein dynamics. The lineshape of an EPR spectrum reflects combined rotational dynamics of the spin probe's local motion within a protein, reorientations of protein domains, and overall protein tumbling. All these motions can be restricted and anisotropic, and separation of these motions is important for thorough characterization of protein dynamics. Multifrequency EPR distinguishes between different motions of a spin-labeled protein, due to the frequency dependence of EPR resolution to fast and slow motion of a spin probe. This gives multifrequency EPR its unique capability to characterize protein dynamics in great detail. In this review, we analyze what makes multifrequency EPR sensitive to different rates of spin probe motion and discuss several examples of its usage to separate spin probe dynamics and overall protein dynamics, to characterize protein backbone dynamics, and to resolve protein conformational states.
多频电子顺磁共振（EPR）与定点自旋标记相结合，是一种用于表征蛋白质动力学的强大光谱工具。EPR谱线形状反映了自旋探针在蛋白质内局部运动的组合旋转动力学、蛋白质结构域的重新定向以及蛋白质的整体翻滚。所有这些运动都可能受到限制且具有各向异性，分离这些运动对于全面表征蛋白质动力学很重要。由于EPR分辨率对自旋探针快速和慢速运动的频率依赖性，多频EPR能够区分自旋标记蛋白质的不同运动。这赋予了多频EPR独特的能力，能够非常详细地表征蛋白质动力学。在本综述中，我们分析了使多频EPR对自旋探针不同运动速率敏感的因素，并讨论了其用于分离自旋探针动力学和整体蛋白质动力学、表征蛋白质主链动力学以及解析蛋白质构象状态的几个示例。
