Negative-ion fast atom bombardment and electrospray ionization tandem mass spectrometry for characterization of sulfated and sialyl Lewis-type glycosphingolipids.

Structural characterization of sulfated and sialyl Lewis (Le)-type glycosphingolipids performed by fast atom bombardment (FAB) and electrospray ionization (ESI) mass spectrometry is described. Both FAB and ESI collision-induced dissociation tandem mass spectrometry (CID-MS/MS) of acidic glycosphingolipids allowed identification of the sulfated or sialyl sugar, and provided information on the saccharide chain sequence. The negative-ion tandem FABMS of sulfated Le-type glycosphingolipids having the non-reducing end trisaccharide ion as the precursor can be used to differentiate the Le(a)- and Le(x)-type oligosaccharides. The ESI CID-MS/MS of multiple-charged ions provided even more detailed structural information, and some of the useful daughter ions appeared with higher m/z values than the precursor because of a lower charge-state. These methodologies can be applied to the structural analyses of glycoconjugates with much larger molecular masses and higher polarity, such as the poly-sulfated and sialyl analogues.