Liquid chromatography-electrospray mass spectrometry as a tool for the analysis of sulfated oligosaccharides from mucin glycoproteins.

An approach for analyzing sulfated oligosaccharide alditol mixtures by liquid chromatography-electrospray mass spectrometry (LC-ESI-MS) is described. Two columns, an amino-bonded column and a porous graphitized carbon column (PGC) were used. Oligosaccharides were eluted with linear gradients of acetonitrile and water, with 5 mM ammonium hydrogencarbonate or formate buffers at a basic pH. The methods were evaluated on a mixture of sulfated oligosaccharide alditols prepared from mucin glycoproteins from pig stomach. Results from LC-ESI-MS of the mixture were compared with the structural information obtained by high energy collision fragmentation using fast atom bombardment tandem mass spectrometry (FAB-MS-MS). The separation ability of the two columns was also tested using a more complex mixture of sulfated oligosaccharides from pig colon, where several isomers were detected. The potential use of in-source collision-induced dissociation (CID) to gain sequence information of sulfated oligosaccharides was also evaluated. The major fragment ions obtained by in-source CID of the trisaccharide Hex-3HexNAcol6-HexNAc6-SO3 were sufficient for assigning the oligosaccharide sequence and the position of the sulfate group within the monosaccharide moiety. The LC-ESI-MS approach should be a valuable tool for characterization of mucin glycosylation and alterations during pathological conditions.