Novel peptide ion chemistry associated with gold (I) cationization is described. Cation switching ion/ion reactions, involving gold dichloride reagent anion, [AuCl2]-, are used to replace protons with a gold (I) cation on a polypeptide. Collision induced dissociation of aurated, lysine-containing peptides results in the elimination of gold hydride and ammonia, generating a [M - H - NH3]+ oxidized species. The oxidized product is likely a cyclic iminium ion. This fragmentation pathway is specific to lysine side-chains as polypeptides containing arginine or histidine in the absence of lysine were not observed to form the oxidized product. While oxidation can occur on N-terminal, internal, and C-terminal lysine residues, it is observed to a lesser extent at lysines found at internal and C-terminal positions. However, isolation and subsequent activation of the [M - H - NH3]+ species derived from the internal or C-terminal positions results in preferential cleavage N-terminal to the oxidized lysine residue. This chemistry has been demonstrated using a variety of model peptides and has also been applied to the analysis of melittin.

中文翻译：

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与金 (I) 阳离子化相关的新型肽离子化学：赖氨酸残基的优先裂解

描述了与金 (I) 阳离子化相关的新型肽离子化学。涉及二氯化金试剂阴离子 [AuCl2]- 的阳离子转换离子/离子反应用于用多肽上的金 (I) 阳离子替换质子。含金的赖氨酸肽的碰撞诱导解离导致金氢化物和氨的消除，产生 [M - H - NH3]+ 氧化物质。氧化产物可能是环状亚胺离子。这种断裂途径对赖氨酸侧链是特异性的，因为在没有赖氨酸的情况下没有观察到含有精氨酸或组氨酸的多肽形成氧化产物。虽然氧化可发生在 N 端、内部和 C 端赖氨酸残基上，但在内部和 C 端位置的赖氨酸上观察到的程度较小。然而，来自内部或 C 端位置的 [M - H - NH3]+ 物质的分离和随后的活化导致优先切割 N 端氧化赖氨酸残基。已使用多种模型肽证明了这种化学反应，也已应用于蜂毒肽的分析。