Primary structure of twenty three neutral and monosialylated oligosaccharides O-glycosidically linked to the human secretory immunoglobulin A hinge region determined by a combination of permethylation analysis and 400-MHz 1H-NMR spectroscopy.

Sialooligosaccharide and asialooligosaccharide alditols, derived from the human milk secretory immunoglobulin A hinge region, have been purified by HPLC using, successively, an amino-bonded silica column and an octadecyl-bonded silica column. Their primary structures were completely resolved by applying a combination of sugar analysis, methylation mass spectrometry and 400-MHz 1H-NMR spectroscopy. In the present report, twenty three oligosaccharide alditols are described and all possess a type two core consisting of the branched trisaccharide: Gal(beta 1-3)[GlcNAc(beta 1-6)]GalNAc-ol. The elongation of this core arises by chain lengthening only on the GlcNAc(beta 1-6) branch for the sialylated compounds, leading to a dodecasaccharide, and on both branches for the neutral compounds leading to a nonasaccharide. Sixteen of the described oligosaccharide structures are original. Moreover, some of the fucosylated structures were found to support Le(a), Le(b) and X blood group determinants.