Study of Fragmentation Behavior of Amadori Rearrangement Products in Lysine-Containing Peptide Model by Tandem Mass Spectrometry

Protein and peptide glycation with reducing sugars through Maillard reaction is recognized as one of the most critical and fundamental reactions in food and in the human body. Amadori rearrangement products (ARPs) are formed at the initial stage of Maillard reaction and then may be converted into intermediate and advanced glycation products. We report here that using electrospray ionization-mass spectrometry (ESI-MS) to directly and rapidly characterize fragmentation behavior of ARPs in a lysine-containing peptide—reducing sugars unambiguously model and identify the modification sites in glycated tri- and tetra-peptides. Tandem mass spectrometry (MS²) results show that the sugar moiety was preferentially fragmented, whereby the neutral loss of small molecules, such as 18 Da (–H₂O), 36 Da (–2 × H₂O), 54 Da (–3 × H₂O), 84 Da (–H₂O–HCOH) and 162 Da from monosaccharide (glucose) moieties and 18 Da, 36 Da, 216 Da, 246 Da and 324 Da from disaccharide moieties. Among the fragmented ions, [M −;84 + H]⁺ of monosaccharides and [M − 246 + H]⁺ of disaccharides are relatively stable. Further multi-stage mass spectrometry (MS³) of [M − 84 + H]⁺ for tri- and longer peptides displays peptide sequence and glycation sites by providing modified y ions (y*), and/or modified b ions (b*) and even a modified a ion (a*). The study is useful to monitor and characterize PMTs of glycation in complex protein systems based on ESI-MS related techniques.