Structural studies of gangliosides by fast atom bombardment ionization, low-energy collision-activated dissociation, and tandem mass spectrometry.

Negative ion fast atom bombardment, low-energy collision-activated dissociation, and tandem mass spectrometry techniques were applied for the structural elucidation of gangliosides. The mass spectra were simplified by selecting a single molecular ion or fragment ion in the analysis of mixtures, and interference by background signals from the liquid matrix could be avoided. Introduction of collision-activated dissociation produced abundant fragment ions convenient for structural analysis. In the daughter scan mode, ions were produced by cleavage of the glycosidic bonds, and not by cleavage at the sugar ring. These ions all contain ceramide moieties, except the sialic acid fragment ion. In the parent scan mode, product ions resulting from cleavage at the sugar ring were detected beside the ions resulting from cleavage at the glycosidic bonds, and ions of oligosaccharide fragments were also detected. In parent scan mode spectra of gangliosides based on the sialic acid ion, all ions contained a sialic acid residue, and the observed ions were similar to those obtained in the high-energy collision-activated dissociation daughter scan mode. These results indicate the usefulness of low-energy collision-activated dissociation tandem mass spectrometry in the daughter and parent scan modes for the analysis of ganglioside structure, in combination with fast atom bombardment mass spectrometry and high-energy collision-activated dissociation mass spectrometry.