title: Negative-ion electron capture dissociation: radical-driven fragmentation of charge-increased gaseous peptide anions.
abstract: The generation of gaseous polyanions with a Coulomb barrier has attracted attention as exemplified by previous studies of fullerene dianions. However, this phenomenon has not been reported for biological anions. By contrast, electron attachment to multiply charged peptide and protein cations has seen a surge of interest due to the high utility for tandem mass spectrometry (MS/MS). Electron capture dissociation (ECD) and electron transfer dissociation (ETD) involve radical-driven fragmentation of charge-reduced peptide/protein cations to yield N-C(α) backbone bond cleavage, resulting in predictable c'/z(•)-type product ions without loss of labile post-translational modifications (PTMs). However, acidic peptides, e.g., with biologically important PTMs such as phosphorylation and sulfonation, are difficult to multiply charge in positive ion mode and show improved ionization in negative-ion mode. We found that peptide anions ([M - nH](n-), n ≥ 1) can capture electrons within a rather narrow energy range (~3.5-6.5 eV), resulting in charge-increased radical intermediates that undergo dissociation analogous to that in ECD/ETD. Gas-phase zwitterionic structures appear to play an important role in this novel MS/MS technique, negative-ion electron capture dissociation (niECD).
authors.affiliation: Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109-1055, USA.
authors.forename: Hyun Ju
authors.initials: HJ
authors.lastname: Yoo
authors.forename: Ning
authors.initials: N
authors.lastname: Wang
authors.forename: Shuyi
authors.initials: S
authors.lastname: Zhuang
authors.forename: Hangtian
authors.initials: H
authors.lastname: Song
authors.forename: Kristina
authors.initials: K
authors.lastname: Håkansson
mesh_terms: D000838:Anions / Q000737:chemistry; D004583:Electrons; D005609:Free Radicals; D005740:Gases / Q000737:chemistry*; D010455:Peptides / Q000737:chemistry*
chemical_list: D000838:Anions; D005609:Free Radicals; D005740:Gases; D010455:Peptides