Matrix-assisted laser desorption/ionization mass spectrometry of neutral and acidic oligosaccharides with collision-induced dissociation

Using ribonuclease B and human α1-acid glycoprotein (AGP) as model glycoproteins, matrix-assisted laser desorption/ionization (MALDI) mass spectrometry with collision-induced dissociation (CID) is validated here as an effective tool for oligosaccharide sequencing. The spectra acquired for high-mannose and complex oligosaccharide structures show characteristic fragments resulting from cleavages of the glycosidic bonds and a few cross-ring cleavages. Esterification of the sialic acid residues is essential in stabilizing the acidic N-linked oligosaccharides. An important analytical feature observed in all acquired spectra is the occurrence of cleavages on the same antenna up to the branching point, as deduced from the absence of fragmentation due to the simultaneous cleavages on two or more antennas.