Derivatization of protonated peptides via gas phase ion–molecule reactions with acetone

• Published in: Journal of the American Society for Mass Spectrometry Vol. 11; no. 3; pp. 244 - 256
• Main Authors: O’Hair, Richard A.J, Reid, Gavin E
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 01.03.2000; Elsevier Science; Springer Nature B.V
• Subjects: Acetone; Adducts; Chemistry; Data Interpretation, Statistical; Exact sciences and technology; Gas Chromatography-Mass Spectrometry; Glycine; Ions; Isotopic labeling; Ketones - chemistry; Mass spectrometry; Organic chemistry; Peptides; Peptides - chemistry; Protein Conformation; Protons; Reactivity and mechanisms; Schiff Bases; Solvents; Vapor phases; Water loss; Ion molecule reaction; Collisional activation; Peptides; Reaction path; Tripeptide; Imine; Glycine; Ketone; Quadrupole spectrometer; Schiff base; α-Aminoacid; Ion trap; Protonated form; Mass spectrometry MS/MS; Dipeptides; Gaseous phase reaction; Acetone
• ISSN: 1044-0305; 1879-1123
• DOI: 10.1016/S1044-0305(99)00142-7

The protonated [M + H] + ions of glycine, simple glycine containing peptides, and other simple di- and tripeptides react with acetone in the gas phase to yield [M + H + (CH 3) 2CO] + adduct ions, some of which fragment via water loss to give [M + H + (CH 3) 2CO − H 2O] + Schiff’s base adducts. Formation of the [M + H + (CH 3) 2CO] + adduct ions is dependent on the difference in proton affinities between the peptide M and acetone, while formation of the [M + H + (CH 3) 2CO − H 2O] + Schiff’s base adducts is dependent on the ability of the peptide to act as an intramolecular proton “shuttle.” The structure and mechanisms for the formation of these Schiff’s base adducts have been examined via the use of collision-induced dissociation tandem mass spectrometry (CID MS/MS), isotopic labeling [using (CD 3) 2CO] and by comparison with the reactions of Schiff’s base adducts formed in solution. CID MS/MS of these adducts yield primarily N-terminally directed a- and b-type “sequence” ions. Potential structures of the b 1 ion, not usually observed in the product ion spectra of protonated peptide ions, were examined using ab initio calculations. A cyclic 5 membered pyrrolinone, formed by a neighboring group participation reaction from an enamine precursor, was predicted to be the primary product.