Abstract
Although electron capture dissociation (ECD) offers many advantages for structural elucidation, a fundamental understanding of all possible processes following electron capture is necessary if ECD is to succeed in the characterization of unknowns. Many biologically active compounds have non-standard structures, e.g, N-alkylation, branching, cyclization, and ester linkages. Here we report ECD of cyclodepsipeptides (valinomycin and beauvericin), including N-methylated structures (beauvericin), branched peptides (AcA(3)K(G(3))A(3)-NH2 and A(3)K(G(3))A(3)-NH2), and oligomers of epsilon-amino acids (epsilon-peptides) (Ac(Ahx)(6)K and (Ahx)(6)K) to establish the behavior of such non-standard structures. ECD of cyclodepsipeptides yielded numerous backbone fragments but no charge-reduced species, consistent with a radical cascade mechanism. ECD of E-peptides resulted in a(.) and y fragments only, suggesting that the N-Calpha c/z(.) fragmentation channel is impeded in those structures. ECD of branched peptides resulted in complex fragmentation patterns, characterized by the presence of the immonium related m ion from the modified residue. (C) 2004 Elsevier B.V. All rights reserved.
Original language | English |
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Pages (from-to) | 23-35 |
Number of pages | 13 |
Journal | International Journal of Mass Spectrometry |
Volume | 234 |
Issue number | 1-3 |
DOIs | |
Publication status | Published - 1 May 2004 |
Keywords
- epsilon-peptides
- FT-ICR
- ECD
- cyclodepsipeptides
- branched peptides