Department of Chemistry, Texas A&M University, College Station, TX 77843, USA.
J Am Soc Mass Spectrom. 2011 Jan;22(1):31-7. doi: 10.1007/s13361-010-0009-4. Epub 2011 Jan 20.
A study on the effect of cysteic acid position on the types of fragment ions formed by collision-induced dissociation (CID) of M - H ions is presented. Of particular note is the observation of d-type fragment ions for peptides that contain an N-terminal cysteic acid (fixed negative charge) and cleavable amino acid side chains possessing a β-γ carbon-carbon bond. For example, the CID mass spectrum of oxidized cys-kemptide (C(ox)LRRASLG) M - H + O(3) ions contains abundant series of d-type fragment ions, and similar results are observed for oxidized cysteine-containing ribonuclease A proteolytic peptides. The d(i) fragment ions are assumed to arise by a charge-remote and/or charge-assisted fragmentation mechanism, which both occur at high collision energies and involve consecutive reactions (i.e., the formation of a(i) ions followed by the elimination of the side chain to form d(i) ions).
本文研究了半胱氨酸位置对 M - H 离子碰撞诱导解离（CID）形成的碎片离子类型的影响。值得注意的是，对于含有 N 端半胱氨酸（固定负电荷）和可裂解氨基酸侧链的肽，观察到了 d 型碎片离子。例如，氧化半胱氨酸 - 肯普肽（C(ox)LRRASLG）M - H + O(3) 离子的 CID 质谱包含丰富的 d 型碎片离子系列，并且氧化含半胱氨酸的核糖核酸酶 A 肽也观察到类似的结果。假设 d(i) 碎片离子是通过远程电荷或电荷辅助断裂机制产生的，这两种机制都发生在高碰撞能量下，并涉及连续反应（即形成 a(i) 离子，然后消除侧链形成 d(i) 离子）。
