STRUCTURAL ELUCIDATION OF UNDERIVATIZED GANGLIOSIDES BY ELECTROSPRAY-IONIZATION TANDEM MASS-SPECTROMETRY (ESIMS MS)/

The structural characterization of intact polysialogangliosides by ele ctrospray-ionization mass spectrometry (ESIMS) and tandem mass spectro metry (MS/MS) is described. The negative-ion ESI mass spectra of gangl iosides such as a tetrasialoganglioside GQ1b, showed molecularly relat ed ions with high sensitivity and accuracy. Collision-induced dissocia tion (CID) MS/MS provided adequate information to characterize the num ber and positions of sialic acids. ESIMS and CIDMS/MS techniques were applied successfully also in the positive-ion mode for characterizatio n of intact gangliosides. Two isomeric disialogangliosides, GD1a and G D1b, are distinguishable from one another by CIDMS/MS in both negative - and positive-ion modes. The technique is readily applicable to struc tural analyses such as determining the positional isomers of glycoconj ugates.