Formation of Deprotonated 2-Imidazoline-4(5)-One Product Ions in the Collision-Induced Dissociation of Some Serine-Containing Dipeptides
Swan, J. S.; Findeis, P. M.; Hilton, S.; Lebold, K. M.; Temelso, B.; Shields, G. C. Formation of Deprotonated 2-Imidazoline-4(5)-One Product Ions in the Collision-Induced Dissociation of Some Serine-Containing Dipeptides. Int. J. Mass Spectrom. 2015, 381, 25-32.
A deprotonated 2-imidazoline-4(5)-one product ion was observed as a major fragment in the collision-induced dissociation (CID) of several dipeptides containing serine at the C-terminal and an amino acid with an alkyl substituent at the N-terminal. This fragment becomes predominant at high collision energies. The same type of product ion was seen in the CID of cyclo(GlyGly). Labeling GlySer with O-18 suggests that the fragmentation may proceed through a symmetrical intermediate such as a deprotonated diketopiperazine. Density functional theory calculations of GlySer provided a possible mechanism for the fragmentation.
International Journal of Mass Spectrometry