Feketeová Linda, O'Hair Richard A J
School of Chemistry, University of Melbourne, Victoria 3010, Australia.
Rapid Commun Mass Spectrom. 2009 Oct 30;23(20):3259-63. doi: 10.1002/rcm.4239.
The [M21+2H]2+ cluster of the zwitterion betaine, M = (CH3)3NCH2CO2, formed via electrospray ionisation (ESI), has been allowed to interact with electrons with energies ranging from >0 to 50 eV in a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer. The types of gas-phase electron-induced dissociation (EID) reactions observed are dependent on the energy of the electrons. In the low-energy region up to 10 eV, electrons are mainly captured, forming the charge-reduced species, {[M21+2H]+}, in an excited state, which stabilises via the ejection of an H atom and one or more neutral betaines. In the higher energy region, above 12 eV, a Coulomb explosion of the multiply charged clusters is observed in highly asymmetric fission with singly charged fragments carrying away more than 70% of the parent mass. Neutral betaine evaporation is also observed in this energy region. In addition, a series of singly charged fragments appears which arise from C-X bond cleavage reactions, including decarboxylation and CH3 group transfer. These latter reactions may arise from access of electronic excited states of the precursor ions.
两性离子甜菜碱（M = (CH3)3NCH2CO2）的[M21+2H]2+簇通过电喷雾电离（ESI）形成，已使其在傅里叶变换离子回旋共振（FT-ICR）质谱仪中与能量范围从>0到50 eV的电子相互作用。观察到的气相电子诱导解离（EID）反应类型取决于电子的能量。在高达10 eV的低能量区域，电子主要被捕获，形成处于激发态的电荷减少物种{[M21+2H]+}，其通过氢原子和一个或多个中性甜菜碱的逸出来稳定。在高于12 eV的较高能量区域，观察到多电荷簇在高度不对称裂变中发生库仑爆炸，单电荷碎片带走超过70%的母体质量。在该能量区域也观察到中性甜菜碱蒸发。此外，出现了一系列单电荷碎片，它们源于C-X键裂解反应，包括脱羧和甲基转移。后一种反应可能源于前体离子电子激发态的作用。
