Structural elucidation of zwitterionic sugar cores from glycosphingolipidsby nanoelectrospray ionization-ion-trap mass spectrometry

The use of electrospray ionization (ESI)-ion-trap mass spectrometry (ITMS) for analysis of zwitterionic, glycolipid-derived sugar cores of glycosphing olipids is described. The capability of the method to perform multiple step s of fragmentation (MSn) allows structural characterization of these compou nds. No derivatization of the released oligosaccharides is necessary when u sing nano-ESI with sample solution flow rates of about 30 nL/min. Investiga tions of positive as well as negative ions in fragmentation experiments up to MS4 permit determination of the sequence of sugar units, their linkage p ositions, and the exact location of the substituents phosphocholine and pho sphoethanolamine, In the case of phosphocholine, chemical cleavage of this substituent was necessary to obtain all the linkage information. Approximat ely 150-250 ng of sample was needed for each analysis. (C) 2000 Academic Pr ess.