Structural characterization of chemically derivatized oligosaccharides by nanoflow electrospray ionization mass spectrometry

Oligosaccharides released from several glycoproteins were derivatized with either 4-aminobenzoic acid 2-(diethylamino)ethyl ester (ABDEAE) (Yoshino, I C; et al. Anal. Chem. 1995, 67, 4028-4031) or 2-aminopyridine. The resultin g derivatives were analyzed on a nanoflow electrospray ionization (ESI) qua drupole-inlet time-of-flight mass spectrometer using the low-energy collisi on-induced dissociation technique. In the MS/MS spectra, the oxonium (b or internal series) and y series ions, which are derived from the multiply cha rged precursor ions, were predominant and were used for the structural read out, Some oxonium ions that were observed in the low-mass region, but that were not found in the PSD analyses (Mo, W.; et al. Anal. Chem. 1998, 70, 45 20-4526), rendered a more detailed structural insight. The oxonium ions at m/z 512.2, which are derived from the fucosylated oligosaccharides of immun oglobulin Y and thyroglobulin, were observed, suggesting that fucosylation had occurred proximal to the outer nonreducing terminus. In addition, the d ata herein show that structural elucidation can be routinely achieved at a low sample concentration. For the case of ABDEAE derivatives, this can be a chieved at the 50 fmol/mu L level and with the actual sample consumption at the attomole level using nanoflow ESI MS/MS.