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首页> 外文期刊>Journal of the American Society for Mass Spectrometry >Long-lived electron capture dissociation product ions experience radical migration via hydrogen abstraction
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Long-lived electron capture dissociation product ions experience radical migration via hydrogen abstraction

机译：长寿命的电子俘获解离产物离子通过夺氢经历自由基迁移

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摘要

To explore the mechanism of electron capture dissociation (ECD) of linear peptides, a set of 16-mer peptides were synthesized with deuterium labeled on the a-carbon position of four glycines. The ECD spectra of these peptides showed that such peptides exhibit a preference for the radical to migrate to the a-carbon position on glycine via hydrogen (or deuterium) abstraction before the final cleavage and generation of the detected product ions. The data show c-type fragment ions, ions corresponding to the radical cation of the c-type fragments, c(.), and they also show c(.)-1 peaks in the deuterated peptides only. The presence of the c(.)-1 peaks is best explained by radical-mediated scrambling of the deuterium atoms in the long-lived, metastable, radical intermediate complex formed by initial electron capture, followed by dissociation of the complex. These data suggest the presence of at least two mechanisms, one slow, one fast. The abundance of H-. and -CO losses from the precursor ion changed upon deuterium labeling indicating the presence of a kinetic isotope effect, which suggests that the values reported here represent an underestimation of radical migration and H/D scrambling in the observed fragments.
机译：为了探索线性肽的电子捕获解离（ECD）的机理，合成了一组16-mer肽，在四个甘氨酸的a-碳位置标记了氘。这些肽的ECD谱图表明，在最终裂解并生成检测到的产物离子之前，此类肽表现出偏爱自由基通过氢（或氘）提取而迁移至甘氨酸上的a-碳位置。数据显示c型碎片离子，即与c型碎片的自由基阳离子相对应的离子c（。），并且它们还仅在氘代肽中显示c（。）-1峰。 c（。）-1峰的存在可以通过长介导的初始电子捕获形成的长寿命亚稳态自由基中间配合物的氘原子的自由基介导的加扰来最好地解释，该配合物解离。这些数据表明存在至少两种机制，一种缓慢，一种快速。 H-的丰度。氘标记后，前体离子的-CO损失发生变化，表明存在动态同位素效应，这表明此处报道的值低估了所观察到的碎片中的自由基迁移和H / D加扰。

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