Low-energy collision induced dissociation of protonated peptides. Importance of an oxazolone formation for a peptide bond cleavage

Full-text article (75 kB)
(subscribers only)

Eur. J. Mass Spectrom. 4, 359 - 364 (1998)

Low-energy collision induced dissociation of protonated peptides. Importance of an oxazolone formation for a peptide bond cleavage

Tomáa Vaisar and Jan Urban
Molecumetics Ltd, 2023 120^th Ave NE, Bellevue WA, USA. E-mail: .

ABSTRACT:

One of the fragmentation mechanisms of protonated peptides assumes formation of an oxazolone both protonated as a b ion or neutral as a counterpart of a y ion. This assumption is based on structures of these species derived from their respective fragmentation. Here, the question of an oxazolone formation is approached from the point of view of the reactant ion, a protonated peptide. A series of model peptides with the general structure AcylAlaProNH₂ was synthesized, where the Acyl represents acyl groups with a range of nucleophilicities. The nucleophilicity of these acyl groups was approximated by proton affinity (PA) of the corresponding acyl N-methyl amides, calculated by ab initio methods. A linear correlation of y₁ ion formation with PA of the acyl group is found that provides evidence for the oxazolone formation during fragmentation of protonated peptides. Three other dipeptides were synthesized to probe the mechanistic aspects of peptide ion fragmentations.

Keywords: Low energy collision-induced dissociation, peptides, fragmentation mechanism, proton affinity, ab initio calculations.

You can now buy this paper on-line in PDF format; it costs only £11.75. Just click on the BUY on-line button. You can pay on-line through a secure server and get access immediately.