Dissociation Chemistry of Hydrogen-Deficient Radical Peptide Anions

Benjamin Moore, Qingyu Sun, Julie C. Hsu, Albert H. Lee, Gene C. Yoo, Tony Ly, Ryan R. Julian*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

The fragmentation chemistry of anionic deprotonated hydrogen-deficient radical peptides is investigated. Homolytic photodissociation of carbon-iodine bonds with 266 nm light is used to generate the radical species, which are subsequently subjected to collisional activation to induce further dissociation. The charges do not play a central role in the fragmentation chemistry; hence deprotonated peptides that fragment via radical directed dissociation do so via mechanisms which have been reported previously for protonated peptides. However, charge polarity does influence the overall fragmentation of the peptide. For example, the absence of mobile protons favors radical directed dissociation for singly deprotonated peptides. Similarly, a favorable dissociation mechanism initiated at the N-terminus is more notable for anionic peptides where the N-terminus is not protonated (which inhibits the mechanism). In addition, collisional activation of the anionic peptides containing carbon-iodine bonds leads to homolytic cleavage and generation of the radical species, which is not observed for protonated peptides presumably due to competition from lower energy dissociation channels. Finally, for multiply deprotonated radical peptides, electron detachment becomes a competitive channel both during the initial photoactivation and following subsequent collisional activation of the radical. Possible mechanisms that might account for this novel collision-induced electron detachment are discussed.

Original languageEnglish
Pages (from-to)460-468
Number of pages9
JournalJournal of the American Society for Mass Spectrometry
Volume23
Issue number3
Early online date30 Dec 2011
DOIs
Publication statusPublished - 1 Mar 2012

Keywords

  • Photodissociation
  • Mechanism
  • Electron
  • Electrospray
  • COLLISION-INDUCED DISSOCIATION
  • ELECTRON PHOTODETACHMENT DISSOCIATION
  • GAS-PHASE
  • CAPTURE DISSOCIATION
  • PROTEIN POLYANIONS
  • MASS-SPECTROMETRY
  • TRYPTIC PEPTIDES
  • IN-VACUO
  • N-H
  • FRAGMENTATION

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