Effect of the N-terminal basic residue on facile Cα-C bond cleavages of aromatic-containing peptide radical cations

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review

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Author(s)

  • Minijie Xu
  • Tao Song
  • Quan Quan
  • Qiang Hao
  • Dei-Cai Fang
  • Ivan K. Chu

Detail(s)

Original languageEnglish
Pages (from-to)5888-5896
Journal / PublicationPhysical Chemistry Chemical Physics
Volume13
Issue number13
Publication statusPublished - 7 Apr 2011

Abstract

Fragmentation of radical cationic peptides [R(G)n-2X(G) 7-n]+ and [R(G)m-2XG]+ (X = Phe or Tyr; m = 2-5; n = 2-7) leads selectively to an + product ions through in situ Cα-C peptide backbone cleavage at the aromatic amino acid residues. In contrast, substituting the arginine residue with a less-basic lysine residue, forming [K(G)n-2X(G) 7-n]+ (X = Phe or Tyr; n = 2-7) analogs, generates abundant b-y product ions; no site-selective Cα-C peptide bond cleavage was observed. Studying the prototypical radical cationic tripeptides [RFG]+ and [KFG]+ using low-energy collision-induced dissociation and density functional theory, we have examined the influence of the basicity of the N-terminal amino acid residue on the competition between the isomerization and dissociation channels, particularly the selective C α-C bond cleavage via β-hydrogen atom migration. The dissociation barriers for the formation of a2 + ions from [RFG]+ and [KFG]+via their β-radical isomers are comparable (33.1 and 35.0 kcal mol-1, respectively); the dissociation barrier for the charge-induced formation of the [b2 - H]+ radical cation from [RFG]+via its α-radical isomer (39.8 kcal mol-1) was considerably higher than that from [KFG]+ (27.2 kcal mol-1). Thus, the basic arginine residue sequesters the mobile proton to promote the charge-remote selective Cα-C bond cleavage by energetically hindering the competing charge-induced pathways. © the Owner Societies. 2011.

Citation Format(s)

Effect of the N-terminal basic residue on facile Cα-C bond cleavages of aromatic-containing peptide radical cations. / Xu, Minijie; Song, Tao; Quan, Quan; Hao, Qiang; Fang, Dei-Cai; Siu, Chi-Kit; Chu, Ivan K.

In: Physical Chemistry Chemical Physics, Vol. 13, No. 13, 07.04.2011, p. 5888-5896.

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review