Figure 1
Detection and location of MAGE-modified peptides. (A) Dot-blot analysis with a specific antibody towards methylglyoxal-derived glycation adducts. A dose and time-dependent glycation is clearly detected. (B) The panels show representative sections of the MALDI-TOF/TOF spectra of peptides from unmodified and glycated insulin. New m/z peaks, absent from the control, are clearly detected in the mass spectra of the glycated insulin (highlighted in red). These new m/z values correspond to the mass of an insulin peptide plus the mass increment characteristic of a hydroimidazolone modification (54 Da). These peptides were analyzed by MS/MS, confirming the glycation of the arginine residue 46. (C) MS/MS spectrum of a glycated insulin peptide with m/z 991.4788, showing the y and b fragment ions. The detected fragment ions arise from the amino acid sequence LVCALQGER GF, with a hydroimidazolone modification on the arginine residues. All the reported glycated peptides were confirmed by MS/MS data.