Chemistry and Biochemistry
Bayer School of Natural and Environmental Sciences
Michael Van Stipdonk
Jeffrey D. Evanseck
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.
Patterson, K. L. (2020). N-terminal Imine Derivatization for Enhanced De Novo Peptide Sequencing: A Study of the Fragmentation Pattern Generated from CID of Peptide-Imines (Doctoral dissertation, Duquesne University). Retrieved from https://dsc.duq.edu/etd/1901
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.