Analysis of gangliosides by capillary zone electrophoresis and capillary zone electrophoresis-electrospray mass spectrometry.

Gangliosides, sialic acid(s)-containing glycosphingolipids, were separated by capillary zone electrophoresis and detected with either UV or electrospray mass spectrometry. Several electrolyte system were evaluated for the separation of underivatized gangliosides. The best result was obtained by using 50 mM borate and 50 mM phosphate buffer containing 20 mM alpha-cyclodextrin at pH 9.9. The four major ganglioside forms (GM1, GD1a, GD1b, GT1b) were successfully separated, and, moreover, each ganglioside yielded two peaks, splitting by the difference in chain length of the ceramide moiety. The resolution obtained in CE-UV could not be reproduced in CE-MS because of the incompatibility of the borate/phosphate buffer to ESI-MS. With the use of more volatile buffers, such as ammonium acetate or 2-[N-cyclohexylamino]-ethanesulfonic acid, baseline resolution was obtained for gangliosides having different number of sugars, but the two disialoganglioside isomers, GD1a and GD1b, were coeluted.

High-energy collision-induced dissociation of ceramide ions from permethylated glycosphingolipids.

Ceramide fragments from permethylated glycosphingolipids (GSLs) were studied by highenergy collision-induced dissociation (CID). In comparison with ceramlde fragments of underivatized GSLs, many more product ions including charge-remote fragment ions were observed. These ions provided detailed structural information on the ceramides. The relative intensity and the mass interval between the L and M ions were used to assign the position of the double bond. The position of the hydroxyl group was assigned with the Ln and K ions. Because the ceramide fragments and not the pseudomolecular ions were selected as the precursor ions, the size of GSLs had little effect on the quality of the product ion spectra. The sensitivity of this approach was in the range of picomoles.