Qualitative determination of early Maillard-products by MALDI-TOF mass spectrometry peptide mapping
Matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS) was used to qualitatively study the formation of early Maillard products of lysozyme, produced upon incubation with seven different sugars (D-ribose, L-rhamnose, D-glucose, D-fructose, D-galactose, D-lactose, D-maltose) in solution, in the presence of oxygen. MALDI-TOF mass spectra of intact lysozyme revealed a heterogeneous distribution of glycation products, detected by significant mass increase and peak broadening. Therefore, to get more detailed information about the nature of the glycation products, we performed MALDI-TOF MS peptide mapping analysis. In each of the peptide mapping spectra we were able to detect the early glycation products (Amadori products/glucosylamines) with high selectivity. We were able to distinguish between the Amadori products of the different sugars, due to the characteristic mass increases of the glycated peptides. Furthermore, variations of the modification pattern were observed, very likely due to the different relativities of the seven reducing sugars. Other, more advanced glycation products of the initially formed Maillard products were also detected. Further studies regarding the nature of these late Maillard products are in progress. Here we report, for the first time, the use of MALDI-TOF MS peptide mapping as a quick and highly selective method for the detection of early stage Maillard products produced upon incubation of lysozyme with seven different reducing sugars.
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