Kuhn Lars T
DFG Research Center Molecular Physiology of the Brain (CMPB), European Neuroscience Institute Göttingen (ENI-G) and EXC 171 Microscopy at the Nanometer Range, Göttingen, Germany,
Top Curr Chem. 2013;338:229-300. doi: 10.1007/128_2013_427.
Photo-chemically induced dynamic nuclear polarization (CIDNP) is a nuclear magnetic resonance (NMR) phenomenon which, among other things, is exploited to extract information on biomolecular structure via probing solvent-accessibilities of tryptophan (Trp), tyrosine (Tyr), and histidine (His) amino acid side chains both in polypeptides and proteins in solution. The effect, normally triggered by a (laser) light-induced photochemical reaction in situ, yields both positive and/or negative signal enhancements in the resulting NMR spectra which reflect the solvent exposure of these residues both in equilibrium and during structural transformations in "real time". As such, the method can offer - qualitatively and, to a certain extent, quantitatively - residue-specific structural and kinetic information on both the native and, in particular, the non-native states of proteins which, often, is not readily available from more routine NMR techniques. In this review, basic experimental procedures of the photo-CIDNP technique as applied to amino acids and proteins are discussed, recent improvements to the method highlighted, and future perspectives presented. First, the basic principles of the phenomenon based on the theory of the radical pair mechanism (RPM) are outlined. Second, a description of standard photo-CIDNP applications is given and it is shown how the effect can be exploited to extract residue-specific structural information on the conformational space sampled by unfolded or partially folded proteins on their "path" to the natively folded form. Last, recent methodological advances in the field are highlighted, modern applications of photo-CIDNP in the context of biological NMR evaluated, and an outlook into future perspectives of the method is given.
光化学诱导动态核极化（CIDNP）是一种核磁共振（NMR）现象，除其他用途外，该现象还可用于通过探测溶液中多肽和蛋白质中色氨酸（Trp）、酪氨酸（Tyr）和组氨酸（His）氨基酸侧链的溶剂可及性来获取生物分子结构信息。这种效应通常由原位（激光）光诱导光化学反应触发，会在所得的NMR光谱中产生正向和/或负向信号增强，这反映了这些残基在平衡状态以及“实时”结构转变过程中的溶剂暴露情况。因此，该方法能够定性地并在一定程度上定量地提供关于蛋白质天然状态，特别是非天然状态的残基特异性结构和动力学信息，而这些信息通常无法从更常规的NMR技术中轻易获得。在本综述中，讨论了应用于氨基酸和蛋白质的光CIDNP技术的基本实验程序，强调了该方法的最新改进，并介绍了未来展望。首先，概述了基于自由基对机制（RPM）理论的该现象的基本原理。其次，给出了标准光CIDNP应用的描述，并展示了如何利用这种效应来提取关于未折叠或部分折叠蛋白质在其“折叠”成天然折叠形式的“路径”上所采样的构象空间的残基特异性结构信息。最后，强调了该领域最近的方法学进展，评估了光CIDNP在生物NMR背景下的现代应用，并对该方法的未来前景进行了展望。
