Coon Joshua J, Shabanowitz Jeffrey, Hunt Donald F, Syka John E P
Department of Chemistry, University of Virginia, McCormick Road, Charlottesville, VA 22908, USA.
J Am Soc Mass Spectrom. 2005 Jun;16(6):880-2. doi: 10.1016/j.jasms.2005.01.015. Epub 2005 Apr 14.
Ion/ion reactions of multiply deprotonated peptide anions with xenon radical cations result in electron abstraction to generate charge-reduced peptide anions containing a free-radical site. Peptide backbone cleavage then occurs by hydrogen radical abstraction from a backbone amide N to facilitate cleavage of the adjacent C-C bond, thereby producing a- and x-type product ions. Introduction of free-radical sites to multiply charged peptides allows access to new fragmentation pathways that are otherwise too costly (e.g., lowers activation energies). Further, ion/ion chemistry, namely electron transfer reactions, presents a rapid and efficient means of generating odd-electron multiply charged peptides; these reactions can be used for studying gas-phase chemistries and for peptide sequence analysis.
多去质子化肽阴离子与氙自由基阳离子的离子/离子反应会导致电子提取，生成含有自由基位点的电荷减少的肽阴离子。然后通过从主链酰胺N上提取氢自由基来促进相邻C-C键的断裂，从而产生a型和x型产物离子，进而发生肽主链裂解。将自由基位点引入多电荷肽中可开启新的碎片化途径，否则这些途径成本过高（例如，降低活化能）。此外，离子/离子化学，即电子转移反应，提供了一种快速有效的生成奇数电子多电荷肽的方法；这些反应可用于研究气相化学和肽序列分析。
