An experimental and theoretical study on fragmentation of protonated N-(2-pyridinylmethyl)indole in electrospray ionization mass spectrometry
An experimental and theoretical study on fragmentation of protonated N-(2-pyridinylmethyl)indole in electrospray ionization mass spectrometry
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DOI：
10.1002/rcm.6371
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发表时间：
2012-11-15
影响因子：
2
通讯作者：
Pan, Yuanjiang
中科院分区：
文献类型：
--
作者：
You, Zhushuang;Guo, Cheng;Pan, Yuanjiang
质子化分子的离解反应是电喷雾电离串联质谱仪(ESI-MSN)结构分析的基础。然而，阐明ESI-MSN中大量的碎裂反应的一般规则仍然相当缺乏。因此，对气相中的裂解反应进行机理研究一直是非常重要的。方法采用ESI离子陷阱串联质谱仪和ESI傅里叶变换离子回旋共振串联质谱仪研究了质子化N-(2-吡啶甲基)吲哚的正离子裂解反应。结果在ESI-MS/MS中，电离质子首先结合到热力学最有利的位置--吡啶氮，然后转移到解离质子化位置并引发裂解。在目标化合物的裂解过程中，一些有趣的反应，如重排反应、质子转移反应和电子转移反应，通过离子/中性络合物发生。理论计算和同位素标记实验都支持所提出的机理。结论本研究有助于更好地了解解离质子化中心，丰富离子/中性络合物在ESI-MS中的作用。它也为有机化合物的结构分析，特别是药物化学中的药物分析提供了有用的信息。版权所有(C)2012 John Wiley&Sons，Ltd.
RATIONALE The dissociation reactions of protonated molecules are the base of structural analysis in electrospray ionization tandem mass spectrometry (ESI-MSn). However, general rules for elucidating the numerous fragmentation reactions in ESI-MSn are still rather lacking. Therefore, it is very important at all times to carry out mechanistic investigations for fragmentation reactions in the gas phase. METHODS The fragmentation reactions of protonated N-(2-pyridinylmethyl)indoles were studied by both of ESI ion trap tandem mass spectrometry and ESI Fourier transform ion cyclotron resonance tandem mass spectrometry in positive-ion mode. RESULTS In ESI-MS/MS, the ionizing proton is first bound to the most thermodynamically favored site, the pyridine nitrogen; then it transfers to the dissociative protonation sites and triggers the fragmentation. In the fragmentation of the target compounds, some interesting reactions, such as rearrangement, proton transfer and electron transfer reactions, take place via ion/neutral complexes. The proposed mechanisms are supported by both theoretical calculations and isotopic labeling experiments. CONCLUSIONS This study is a case for better understanding the dissociative protonation sites and enriching the knowledge about the role of ion/neutral complexes in ESI-MS. It also provides useful information for the structural analysis of organic compounds, especially drug analysis in pharmaceutical chemistry. Copyright (C) 2012 John Wiley & Sons, Ltd.