XAS AS A NOVEL PROBE OF ELECTRONIC STRUCTURE AND REACTIVITY FOR PROTEIN-BASED SU

该子项目是利用NIH/NCRR资助的中心赠款提供的资源的许多研究子项目之一。子项目和研究者（PI）可能从另一个NIH来源获得了主要资金，因此可以在其他CRISP条目中表示。所列机构为中心机构，不一定为研究者机构。正在使用硫K边X射线吸收光谱作为这些具有生物重要性的肽自由基电子结构的新型探针，在各种不同的蛋白质环境中研究硫中心自由基的基本反应性。半胱氨酰自由基（[Cys SCys]1-）已被观察或假定为多种生物功能的中间体，包括酶催化、远程电子转移、肽翻译后修饰、细胞氧化还原缓冲，甚至细胞氧化还原信号传导。电子顺磁共振一直是用来表征这些自由基物种的主要工具，但直接观察受到信号的自旋轨道展宽的影响，这降低了该方法的有效性。由硫原子上的自由基性质引起的S 1 s-> 3 p前边缘跃迁被用于直接探测这些自由基物种的电子结构，并研究诸如氢键和电子离域等因素对这些自由基在各种蛋白质环境中的反应性的影响。这项工作的一个重要目标是发展S K边XAS作为一个强大的和一般的探针硫自由基物种调查范围广泛的生物系统。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The basic reactivity of sulfur-centered radicals is being studied in a variety of different protein environments using Sulfur K-edge X-ray Absorption Spectroscopy as a novel probe of the electronic structure of these biologically-important peptidic radicals. Cysteinyl radicals ([Cys¿¿]) and disulfide anion radicals ([CysS¿¿SCys]1-) have been observed or postulated as intermediates in several biological functions including enzymatic catalysis, long-range electron transfer, peptide post-translational modification, cellular redox buffering, and even cellular redox signaling. Electron paramagnetic resonance has been the primary tool used to characterize these radical species but direct observation is compromised by spin-orbit broadening of the signals, which has diminished the effectiveness of the approach. The S 1s->3p pre-edge transition that results from radical character on a sulfur atom is being used to directly probe the electronic structure of these radical species and to investigate the effect of factors such as hydrogen bonding and electron delocalization on the reactivity of these radicals in various protein environments. An important goal of this effort is to develop S K-edge XAS as a powerful and general probe of sulfur radical species to investigate a wide range of biological systems.