M.J. van Stipdonk
- IRMPD spectroscopy reveals a novel rearrangement reaction for modified peptides that involves elimination of the N-terminal amino acid
- International Journal of Mass Spectrometry
- Pages (from-to)
- Document type
- Faculty of Science (FNWI)
- Van 't Hoff Institute for Molecular Sciences (HIMS)
In this study, peptides were derivatized by reaction with salicylaldehyde to create N-terminal imines (Schiff bases). Collision-induced dissociation of the imine-modified peptides produces a complete series of b and a ions (which reveal sequence). However, an unusual pathway is also observed, one that leads to elimination of the residue mass of the N-terminal amino acid despite the chemical modification to create the imine. This pathway was investigated further using infrared multiple-photon dissociation (IRMPD) spectroscopy and density functional theory with alanine-glycine-glycine (AGG) as the test peptide. The IRMPD spectrum for the product generated by loss of 71 from modified AGG (Sal-AGG) matches one predicted for protonated Sal-GG, as well as the IRMPD spectrum of glycine-glycine derivatized independently to produce a Schiff base. We conclude that the residue mass of the N-terminal amino acid is likely eliminated through a pathway that involves nucleophilic attack by an amide N atom and possible formation of an imidazole-4-one intermediate.
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