Proton Mobility in b2 Ion Formation and Fragmentation Reactions of Histidine-Containing Peptides
Proton Mobility in b2 Ion Formation and Fragmentation Reactions of Histidine-Containing Peptides
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DOI：
10.1007/s13361-015-1298-4
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发表时间：
2016-03-01
影响因子：
3.2
通讯作者：
Bythell, Benjamin J.
中科院分区：
文献类型：
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作者：
Nelson, Carissa R.;Abutokaikah, Maha T.;Bythell, Benjamin J.
对质子化的含组氨酸肽及其 b(2) 离子的断裂反应进行了详细的能量分辨研究。利用密度泛函理论计算来预测碎片反应如何发生，以便我们可以了解为什么质谱显示出特定的能量依赖性。我们将我们的结果与当前文献和合成 b(2) 离子标准品进行比较。我们表明，His 残基的位置确实会影响随后的 b(2) 离子（二酮哌嗪、恶唑酮、内酰胺）的特性，并且能量分辨 CID 可以根据这些异构体产物的裂解能量来区分这些异构体产物。组氨酸侧链促进除第一个酰胺键的反式-顺式异构化之外的所有主要转化，这是二酮哌嗪 b(2) 离子形成的必要先决条件。尽管缺乏催化作用，但预计反式-顺式异构化是容易的。与此同时，随后的酰胺键断裂反应是限速的。
A detailed energy-resolved study of the fragmentation reactions of protonated histidine-containing peptides and their b(2) ions has been undertaken. Density functional theory calculations were utilized to predict how the fragmentation reactions occur so that we might discern why the mass spectra demonstrated particular energy dependencies. We compare our results to the current literature and to synthetic b(2) ion standards. We show that the position of the His residue does affect the identity of the subsequent b(2) ion (diketopiperazine versus oxazolone versus lactam) and that energy-resolved CID can distinguish these isomeric products based on their fragmentation energetics. The histidine side chain facilitates every major transformation except trans-cis isomerization of the first amide bond, a necessary prerequisite to diketopiperazine b(2) ion formation. Despite this lack of catalyzation, trans-cis isomerization is predicted to be facile. Concomitantly, the subsequent amide bond cleavage reaction is rate-limiting.