Journal
JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY
Volume 26, Issue 3, Pages 432-443Publisher
SPRINGER
DOI: 10.1007/s13361-014-1038-1
Keywords
Photodissociation; Proline-containing peptides; Fragmentation; Molecular dynamics; H/D exchange
Funding
- Deutsche Forschungsgemeinschaft [DFG FOR1282]
- Split-Dalmatia County
- European Research Council under the European Union [320659]
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UV photodissociation of proline-containing peptide ions leads to unusual product ions. In this paper, we report laser-induced dissociation of a series of proline-containing peptides at 213 nm. We observe specific fragmentation pathways corresponding to the formation of (y-2), (a + 2) and (b + 2) fragment ions. This was not observed at 266 nm or for peptides which do not contain proline residues. In order to obtain insights into the fragmentation dynamics at 213 nm, a small peptide (RPK for arginine-proline-lysine) was studied both theoretically and experimentally. Calculations of absorption spectra and non-adiabatic molecular dynamics (MD) were made. Second and third excited singlet states, S-2 and S-3, lie close to 213 nm. Non-adiabatic MD simulation starting from S-2 and S-3 shows that these transitions are followed by C-C and C-N bond activation close to the proline residue. After this first relaxation step, consecutive rearrangements and proton transfers are required to produce unusual (y-2), (a + 2) and (b + 2) fragment ions. These fragmentation mechanisms were confirmed by H/D exchange experiments.
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