Analysis of non-enzymatically glycated peptides: neutral-loss-triggered MS(3) versus multi-stage activation tandem mass spectrometry.

Non-enzymatic glycation of tissue proteins has important implications in the development of complications of diabetes mellitus. While electron transfer dissociation (ETD) has been shown to outperform collision-induced dissociation (CID) in sequencing glycated peptides by tandem mass spectrometry, ETD instrumentation is not yet widely available and often suffers from significantly lower sensitivity than CID. In this study, we evaluated different advanced CID techniques (i.e., neutral-loss-triggered MS(3) and multi-stage activation) during liquid chromatography/multi-stage mass spectrometric (LC/MS(n)) analyses of Amadori-modified peptides enriched from human serum glycated in vitro. During neutral-loss-triggered MS(3) experiments, MS(3) scans triggered by neutral losses of 3 H(2)O or 3 H(2)O + HCHO produced similar results in terms of glycated peptide identifications. However, neutral losses of 3 H(2)O resulted in significantly more glycated peptide identifications during multi-stage activation experiments. Overall, the multi-stage activation approach produced more glycated peptide identifications, while the neutral-loss-triggered MS(3) approach resulted in much higher specificity. Both techniques are viable alternatives to ETD for identifying glycated peptides.