Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, MI 48109-1055, USA.
J Am Soc Mass Spectrom. 2011 Dec;22(12):2209-21. doi: 10.1007/s13361-011-0233-6. Epub 2011 Sep 20.
Dissociation of singly charged species is more challenging compared with that of multiply charged precursor ions because singly charged ions are generally more stable. In collision activated dissociation (CAD), singly charged ions also gain less kinetic energy in a fixed electric field compared with multiply charged species. Furthermore, ion-electron and ion-ion reactions that frequently provide complementary and more extensive fragmentation compared with CAD typically require multiply charged precursor ions. Here, we investigate electron induced dissociation (EID) of singly deprotonated peptides and compare the EID fragmentation patterns with those observed in negative ion mode CAD. Fragmentation induced upon electron irradiation and collisional activation is not specific and results in the formation of a wide range of product ions, including b-, y-, a-, x-, c-, and z-type ions. Characteristic amino acid side chain losses are detected in both techniques. However, differences are also observed between EID and CAD spectra of the same species, including formation of odd-electron species not seen in CAD, in EID. Furthermore, EID frequently results in more extensive fragmentation compared with CAD. For modified peptides, EID resulted in retention of sulfonation and phosphorylation, allowing localization of the modification site. The observed differences are likely due to both vibrational and electronic excitation in EID, whereas only the former process occurs in CAD.
与多电荷前体离子相比，单电荷物种的离解更具挑战性，因为单电荷离子通常更稳定。在碰撞激活解离（CAD）中，与多电荷物种相比，单电荷离子在固定电场中获得的动能也更少。此外，与 CAD 相比，通常需要多电荷前体离子才能进行提供互补且更广泛片段的离子-电子和离子-离子反应。在这里，我们研究了单脱质子肽的电子诱导解离（EID），并将 EID 碎裂模式与在负离子模式 CAD 中观察到的碎裂模式进行了比较。电子辐照和碰撞激活引起的碎裂没有特异性，会导致形成广泛的产物离子，包括 b-、y-、a-、x-、c-和 z-型离子。在这两种技术中都检测到了特征性的氨基酸侧链缺失。然而，在相同物质的 EID 和 CAD 光谱之间也观察到了差异，包括在 CAD 中未观察到的奇数电子物质的形成，而在 EID 中则观察到了奇数电子物质的形成。此外，与 CAD 相比，EID 通常会导致更广泛的片段化。对于修饰肽，EID 保留了磺化和磷酸化，从而能够定位修饰部位。观察到的差异可能归因于 EID 中的振动和电子激发，而 CAD 中仅发生前一种过程。
