Peter M. Findeis, Senior Mass Spectrometry & Instrumentation Specialist
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. (C) 2015 Elsevier B.V. All rights’ reserved.
Swan, James; Findeis, Peter M.; Hilton, Sheena; Lebold, Kathryn M.; Temelso, Berhane; and Shields, George C. “Formation of Deprotonated 2-Imidazoline-4(5)-One Product Ions in the Collision-Induced Dissociation of Some Serine-Containing Dipeptides.” International Journal of Mass Spectrometry 381, (2015) : 25-32.