Leaving group effects on the selectivity of the gas-phase fragmentation reactions of side chain fixed-charge-containing peptide ions
作者:Kade D. Roberts、Gavin E. Reid
DOI:10.1002/jms.1150
日期:2007.2
The effect of trialkylsulfonium versus quaternaryalkylammonium ions on the multistage gas-phase fragmentation reactions of side chain, fixed-charge, cysteine-containing peptides has been examined in a quadrupole linear ion trap. These tandem mass spectrometry experiments reveal that selective loss of dialkylsulfide from fixed-charge sulfonium ion derivatives is the dominant fragmentation pathway regardless of the degree of proton mobility, indicating that it is the most energetically favored fragmentation pathway. In contrast, the loss of trimethylamine from the side chain of fixed-charge ammonium-ion-containing cysteine derivatives appears to be less energetically favored, and as a result extensive charge-remote fragmentation is observed under low proton mobility conditions, while under conditions of high proton mobility, amide bond fragmentation reactions dominate. These findings are supported by molecular orbital calculations at the B3LYP/6-31 + G(d, p) level of theory, which showed that the neutral loss of dimethylsulfide is both thermodynamically and kinetically preferred over the loss of trimethylamine. Copyright © 2006 John Wiley & Sons, Ltd.
已在四极线性离子阱中研究了三烷基锍与季烷基铵离子对侧链、固定电荷、含半胱氨酸肽的多级气相裂解反应的影响。这些串联质谱实验表明,无论质子迁移率如何,固定电荷锍离子衍生物中二烷基硫醚的选择性损失是主要的碎裂途径,表明它是最受能量青睐的碎裂途径。相反,三甲胺从含固定电荷铵离子的半胱氨酸衍生物的侧链损失似乎不太受能量青睐,因此在低质子迁移率条件下观察到广泛的电荷远程碎裂,而在高质子迁移率,酰胺键断裂反应占主导地位。这些发现得到了 B3LYP/6-31 + G(d, p) 理论水平的分子轨道计算的支持,该计算表明二甲硫醚的中性损失在热力学和动力学上都优于三甲胺的损失。版权所有 © 2006 约翰·威利父子有限公司