REVISED PROTOCOLS FOR USE OF DISPERSIBLE RADIOACTIVITY AT X 9A

通过辐解形成的羟基自由基可以作为一种化学物质 探针对它们与蛋白质和DNA-蛋白质复合体的反应性 受这些分子中溶剂可获得性的影响。在……里面 与反应时间只有几秒的其他方法不同 在肽主链的键被割裂的情况下，我们的研究 蛋白质已经揭示了氨基酸侧链是由 同步辐射裂解。为了将这项技术应用于 表征蛋白质折叠过程的瞬时中间产物和 蛋白质/配体的相互作用，有必要了解自然界 和氨基酸的辐射裂解修饰的反应性顺序。这 调查报告质谱学鉴定 辐射诱导的氨基酸修饰：Phe，Tyr，Pro，Met， Cys和Trp。好氧条件下O18标记水的附加使用 实验条件揭示了氨基酸侧链 修饰通过两条涉及两个羟基的途径发生 水中的自由基和空气中的分子氧。的顺序 用串联质谱法测定了这些氨基酸的反应性。 光谱分析。

ydroxyl radicals formed by radiolysis can function as a chemical probe since their reactivity with proteins and DNA-protein complexes is influenced by solvent accessibility within these molecules. In contrast to other methods with reaction time scales of a few seconds where bonds of the peptide backbone are cleaved our studies of proteins have revealed that amino acids side chains are modified by synchrotron radiolysis. In order to apply this technology to characterize transient intermediates of a protein folding process and protein/ligand interactions, it is necessary to understand the nature and reactivity order of radiolytic modifications to amino acids. This investigation reports the mass spectrometric identification of radiolysis-induced modification of amino acids: Phe, Tyr, Pro, Met, Cys and Trp. The additional use of O18-labeled water under aerobic experimental conditions reveals that amino acid side chain modifications occur through two pathways involving both hydroxyl radicals from water and molecular oxygen from air. The order of reactivity for these amino acids has been examined by tandem mass spectrometry.