Profiling of N-linked oligosaccharides using phenylhydrazine derivatization and mass spectrometry

N-linked oligosaccharide standards obtained from commercial sources were derivatized with phenylhydrazine (PHN) and analyzed by on-line reversed-phase high performance liquid chromatography (HPLC)/electrospray ionization mass spectrometry (ESI-MS). This procedure was then applied to mixtures of N-glycans enzymatically released from hen ovalburnin. Under ESI-MS conditions. phenylhydrazones of asialylated oligosaccharide standards and ovalbumin glycans produced mainly [M + 2H](2+) molecular ions at low cone voltage values, while minimal fragmentation was observed. Reversed-phase HPLC/ESI-MS total and selected ion chromatograms obtained for derivatized N-glycans from ovalburnin showed partial but useful separation. Overall alycan profiles obtained by ESI-MS were compared with results obtained by matrix-assisted laser desorption/ionization (MALDI)-MS. Qualitatively. profiles were similar from one technique to the other in terms of relative abundance of glycans versus composition. Post-source decay (PSD) analysis of the [M +Na](+) ions of PHN-glycans showed dominant B, C and internal B/Y, C/Y cleavages. These patterns were helpful in relating fragmentation to proposed structures. Cross-ring cleavage fragment ions (A-type) were also observed in most cases. The PHN derivatization method is fast and simple. It produces abundant parent ions in both MALDI-MS and ESI-MS, while avoiding the presence of salt contaminants during the labeling procedure. (C) 2003 Elsevier B.V. All rights reserved.