Novel tri-and tetrasialosylpoly-N-acetyllactosaminyl gangliosides of human placenta: structure determination of pentadeca- and eicosaglycosylceramides by methylation analysis, fast atom bombardment mass spectrometry, and 1H NMR spectroscopy.

A series of highly polar neolacto series (poly-N-acetyllactosaminyl) gangliosides were isolated from human placenta tissue and purified by HPLC and preparative HPTLC. Two of these ganglioside fractions (G-12 and G-13) were analyzed by 500-MHz 1H NMR spectroscopy, GC-EIMS, +FAB-MS, and sequential exoglycosidase treatments. Their structures have been identified as being of the repeating N-acetyllactosamine type, multiply branched through GlcNAc beta 1----6/3 linkages, with every nonreducing Gal terminal alpha 2----3-sialosylated, as shown below. These are among the highest molecular weight glycosphingolipids whose detailed oligosaccharide structures are presently known. (formula; see text).