Effects of Cation Charge-Site Identity and Position on Electron-Transfer Dissociation of Polypeptide Cations

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• 作者：Yu Xia ; Harsha P. Gunawardena ; David E. Erickson ; Scott A. McLuckey
• 刊名：Journal of the American Chemical Society
• 出版年：2007
• 出版时间：October 10, 2007
• 年：2007
• 卷：129
• 期：40
• 页码：12232 - 12243
• 全文大小：392K
• 年卷期：v.129,no.40(October 10, 2007)
• ISSN：1520-5126

文摘

The effect of cation charge site on gas-phase ion/ion reactions between multiply protonatedmodel peptides and singly charged anions has been examined. Insights are drawn from the quantitativeexamination of the product partitioning into competing channels, such as proton transfer (PT) versus electrontransfer (ET), electron transfer followed by dissociation (ETD) versus electron transfer without dissociation(ET, no D), and fragmentation of backbone bonds versus fragmentation of side chains. Peptide cationscontaining protonated lysine, arginine, and histidine showed similar degrees of electron transfer, whichwere much higher than the peptide having fixed-charge sites, that is, trimethyl ammonium groups. Amongthe four types of cation charge sites, protonated histidine showed the highest degree of ET, no D, while noapparent intact electron-transfer products were observed for peptides with protonated lysine or arginine.All cation types showed side chain losses with arginine yielding the greatest fraction and lysine the smallest.The above trends were observed for each electron-transfer reagent. However, proton transfer wasconsistently higher with 1,3-dinitrobeznene anions, as was the fraction of side-chain losses. The partitioningof products among the various electron-transfer channels provides evidence for several of the mechanismsthat have been proposed to account for electron-transfer dissociation and electron-capture dissociation.The simplest picture to account for all of the observations recognizes that several mechanisms can contributeto the observed products. Furthermore, the identity of the anionic reagent and the positions of the chargesites can affect the relative contributions of the competing mechanisms.