Ion chemistry of protonated glutamic acid derivatives
Ion chemistry of protonated glutamic acid derivatives
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DOI：
10.1016/s1387-3806(01)00405-5
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发表时间：
2001-10-01
影响因子：
1.8
通讯作者：
Harrison, AG
中科院分区：
文献类型：
--
作者：
Harrison, AG
通式H-Glu（X）-Y的质子化谷氨酸衍生物（特别是H-Gln-OH、H-Glu-NH 2、H-Glu-OMe和H-Glu（OMe）-OH）的断裂反应已作为内能的函数进行了研究，并通过串联质谱（MS/MS/MS）实验。结果表明，HX从γ-羧基的损失不仅导致质子化的焦谷氨酸衍生物，而且导致环状阳离子化的酸酐或酰亚胺离子。HY从γ-羧基位置的损失伴随着CO的损失，这与已知的α-氨基酰基离子的不稳定性一致。二次裂解产物C_4H_6NO ~+（m/z 84）是由[MH-HX]（+）离子失去HY + CO和[MH-HY- CO]（+）离子失去RX而产生的。氘标记实验表明，虽然HX和HY+CO的初级损失仅涉及不稳定的氢，但在[MH-HX]（+）和[MH-HY- CO]（+）初级离子的进一步碎裂中，不稳定的氢和C-键合的氢都损失。得出的结论是，有几个途径的m/z 84的产物离子和几种结构的碎片离子。(C)2001年爱思唯尔科学有限公司
The fragmentation reactions of protonated glutamic acid derivatives of general formula H-Glu(X)-Y, specifically H-Gln-OH, H-Glu-NH2, H-Glu-OMe, and H-Glu(OMe)-OH, have been studied as a function of internal energy and by tandem mass spectrometry (MS/MS/MS) experiments. The results show that loss of HX from the gamma -carboxyl group leads not only to a protonated pyroglutamic acid derivative but also to a cyclic cationated anhydride or imide ion. Loss of HY from the gamma -carboxyl position is accompanied by loss of CO in agreement with the known instability of alpha -aminoacylium ions. The secondary fragmentation product C4H6NO+ (m/z 84) is shown to arise by loss of HY + CO from the [MH - HX](+) ions and by loss of RX from the [MH - HY - CO](+) ions. Deuterium labeling experiments show that, although the primary loss of HX and HY+CO involve only labile hydrogens, both labile hydrogens and C-bonded hydrogens are lost in the further fragmentation of the [MH - HX](+) and [MH - HY - CO](+) primary ions. It is concluded that there are several pathways to the m/z 84 product ion and several structures for this fragment ion. (C) 2001 Elsevier Science B.V.