Discovery and mechanistic studies of facile N-terminal C α-C bond cleavages in the dissociation of tyrosine-containing peptide radical cations

Research output: Journal Publications and ReviewsRGC 21 - Publication in refereed journalpeer-review

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Author(s)

  • Xiaoyan Mu
  • Tao Song
  • Minjie Xu
  • Cheuk-Kuen Lai
  • Julia Laskin
  • Ivan K. Chu

Detail(s)

Original languageEnglish
Pages (from-to)4273-4281
Journal / PublicationJournal of Physical Chemistry B
Volume118
Issue number16
Publication statusPublished - 24 Apr 2014

Abstract

Fascinating N-terminal Cα-C bond cleavages in a series of nonbasic tyrosine-containing peptide radical cations have been observed under low-energy collision-induced dissociation (CID), leading to the generation of rarely observed x-type radical fragments, with significant abundances. CID experiments of the radical cations of the alanyltyrosylglycine tripeptide and its analogues suggested that the N-terminal Cα-C bond cleavage, yielding its [x2 + H]•+ radical cation, does not involve an N-terminal α-carbon-centered radical. Theoretical examination of a prototypical radical cation of the alanyltyrosine dipeptide, using density functional theory calculations, suggested that direct N-terminal C α-C bond cleavage could produce an ion-molecule complex formed between the incipient a1+ and x1 fragments. Subsequent proton transfer from the iminium nitrogen atom in a1+ to the acyl carbon atom in x 1 results in the observable [x1 + H] •+. The barriers against this novel Cα-C bond cleavage and the competitive N-Cα bond cleavage, forming the complementary [c1 + 2H]+/[z1 - H] •+ ion pair, are similar (ca. 16 kcal mol-1). Rice-Ramsperger-Kassel-Marcus modeling revealed that [x1 + H] •+ and [c1 + 2H]+ species are formed with comparable rates, in agreement with energy-resolved CID experiments for [AY]•+. © 2014 American Chemical Society.

Citation Format(s)

Discovery and mechanistic studies of facile N-terminal C α-C bond cleavages in the dissociation of tyrosine-containing peptide radical cations. / Mu, Xiaoyan; Song, Tao; Xu, Minjie et al.
In: Journal of Physical Chemistry B, Vol. 118, No. 16, 24.04.2014, p. 4273-4281.

Research output: Journal Publications and ReviewsRGC 21 - Publication in refereed journalpeer-review