title: Electron-capture-induced dissociation of microsolvated di- and tripeptide monocations: elucidation of fragmentation channels from measurements of negative ions.
abstract: The results from an experimental study of bare and microsolvated peptide monocations in high-energy collisions with cesium vapor are reported. Neutral radicals form after electron capture from cesium, which decay by H loss, NH(3) loss, or N-C(alpha) bond cleavage into characteristic z(*) and c fragments. The neutral fragments are converted into negatively charged species in a second collision with cesium and are identified by means of mass spectrometry. For protonated GA (G = glycine, A = alanine), the branching ratio between NH(3) loss and N-C(alpha) bond cleavage is found to strongly depend on the molecule attached (H(2)O, CH(3)CN, CH(3)OH, and 18-crown-6 ether (CE)). Addition of H(2)O and CH(3)OH increases this ratio whereas CH(3)CN and CE decrease it. For protonated AAA ([AAA+H](+)), a similar effect is observed with methanol, while the ratio between the z(1) and z(2) fragment peaks remains unchanged for the bare and microsolvated species. Density functional theory calculations reveal that in the case of [GA+H](+)(CE), the singly occupied molecular orbital is located mainly on the amide group in accordance with the experimental results.
authors.affiliation: Department of Physics and Astronomy, University of Aarhus, Ny Munkegade, 8000 Aarhus C, Denmark. zetter@phys.au.dk
authors.forename: Henning
authors.initials: H
authors.lastname: Zettergren
authors.forename: Lamri
authors.initials: L
authors.lastname: Adoui
authors.forename: Virgile
authors.initials: V
authors.lastname: Bernigaud
authors.forename: Henrik
authors.initials: H
authors.lastname: Cederquist
authors.forename: Nicole
authors.initials: N
authors.lastname: Haag
authors.forename: Anne I S
authors.initials: AI
authors.lastname: Holm
authors.forename: Bernd A
authors.initials: BA
authors.lastname: Huber
authors.forename: Preben
authors.initials: P
authors.lastname: Hvelplund
authors.forename: Henrik
authors.initials: H
authors.lastname: Johansson
authors.forename: Umesh
authors.initials: U
authors.lastname: Kadhane
authors.forename: Mikkel Koefoed
authors.initials: MK
authors.lastname: Larsen
authors.forename: Bo
authors.initials: B
authors.lastname: Liu
authors.forename: Bruno
authors.initials: B
authors.lastname: Manil
authors.forename: Steen
authors.initials: S
authors.lastname: Brøndsted Nielsen
authors.forename: Subhasis
authors.initials: S
authors.lastname: Panja
authors.forename: Jimmy
authors.initials: J
authors.lastname: Rangama
authors.forename: Peter
authors.initials: P
authors.lastname: Reinhed
authors.forename: Henning T
authors.initials: HT
authors.lastname: Schmidt
authors.forename: Kristian
authors.initials: K
authors.lastname: Støchkel
mesh_terms: D002412:Cations / Q000737:chemistry; D002586:Cesium / Q000737:chemistry; D043844:Crown Ethers / Q000737:chemistry; D004583:Electrons; D007477:Ions / Q000737:chemistry*; D013058:Mass Spectrometry; D010455:Peptides / Q000737:chemistry*
chemical_list: D002412:Cations; D043844:Crown Ethers; D007477:Ions; D010455:Peptides; D002586:Cesium; C015762:18-crown-6