Defense Date


Graduation Date

Spring 5-8-2020


Immediate Access

Submission Type


Degree Name



Chemistry and Biochemistry


Bayer School of Natural and Environmental Sciences

Committee Chair

Michael Van Stipdonk

Committee Member

Michael Cascio

Committee Member

Jeffrey D. Evanseck

Committee Member

Theodore Corcovilos


peptide fragmentation, peptidomics, gas-phase, CID, IRMPD, tandem mass spectrometry, ion trap, de novo sequencing, peptide sequencing, metal-cationized


In this work, the fragmentation pattern derived from model peptides derivatized to create N-terminal imines (Schiff bases) were evaluated. Collision-induced dissociation of the protonated peptide-imines ([M+H]+) generally produced complete series of the sequence informative an and bn ions, now undoubtedly characteristic of the peptide ion species. A novel product ion was also observed, denoted the yǂ ion, determined by IRMPD spectroscopy and density functional theory to be generated from the elimination of the N-terminal amino acid residue despite the N-terminal modification. It was concluded the pathway involved a nucleophilic attack by an amide nitrogen and the possible formation of an imidazole-4-one intermediate, which collapses to generate a truncated, protonated peptide-imine with a conserved primary sequence. N-terminal imine-modification was also observed to eliminate sequence scrambling events, presumably by eliminating the macrocyclic b ion mechanism implicated in the sequence rearrangements. Additionally, the CID mass spectra of Ag-cationized imine-modified peptides were obtained. An apparent even-electron, [M-H]+ peptide ion was observed, determined to be generated by the loss of AgH. The hydrogen abstraction was explicitly identified to originate from the imine-carbon of the argentinated modified peptide. CID of the [M–H]+ ions generated sequence ions analogous to those produced from the [M+H]+ species of imine-modified peptides, however less extensively.



Additional Citations

VanStipdonk, M. J., Patterson, K., Gibson, J. K., Berden, G., and Oomens, J. (2015). IRMPD spectroscopy reveals a novel rearrangement reaction for modified peptides that involves elimination of the N-terminal amino acid. Int. J. Mass Spectrom., 379, 165-178.

Plaviak, A., Osburn, S., Patterson, K., and VanStipdonk, M. J. (2016). Even-electron [M-H]+ ions generated by loss of AgH from argentinated peptides with N-terminal imine groups. Rapid Commun. Mass Spectrom., 30, 69-80.