Electron-capture-induced dissociation of microsolvated di- and tripeptide monocations: elucidation of fragmentation channels from measurements of negative ions.
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.
Zettergren
Henning
H
Department of Physics and Astronomy, University of Aarhus, Ny Munkegade, 8000 Aarhus C, Denmark. zetter@phys.au.dk
Adoui
Lamri
L
Bernigaud
Virgile
V
Cederquist
Henrik
H
Haag
Nicole
N
Holm
Anne I S
AI
Huber
Bernd A
BA
Hvelplund
Preben
P
Johansson
Henrik
H
Kadhane
Umesh
U
Larsen
Mikkel Koefoed
MK
Liu
Bo
B
Manil
Bruno
B
Brøndsted Nielsen
Steen
S
Panja
Subhasis
S
Rangama
Jimmy
J
Reinhed
Peter
P
Schmidt
Henning T
HT
Støchkel
Kristian
K
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*
D002412:Cations; D043844:Crown Ethers; D007477:Ions; D010455:Peptides; D002586:Cesium; C015762:18-crown-6