Fig. 2.
MS (A) and MS/MS (B) spectra of the peptide containing glycated Lys-206 residue of human serotransferrin. Product ions detected at m/z 2341.1 and 2311.1 represent the pyrilium (M + 108) and furylium/immonium (M + 78) ions formed by post-activation fragmentation of the relatively less stable Amadori compound (M + 162). Here, the MS/MS spectrum has been zoomed in to include y-ions containing the glycated residue. The detection of pyrilium y-ions (y + C6H4O2) together with multiple losses of H2O are particular to glycated peptides. Theoretical values for selected y-ions are listed in the table on the left.