Analysis of sialyl oligosaccharides by high-performance liquid chromatography-electrospray ionisation-mass spectrometry with differentiation of α2-3 and α2-6 sialyl linkages

A method for analysing sialyl oligosaccharides from bovine colostrum using high-performance liquid chromatography-electrospray ionisation-mass spectrometry (HPLC-ESI-MS) is described. Under positive ionisation mode, mass spectra of α2-3 and α2-6 linkages were different, and the former produced a prominent B2 (or B3 in disialyl lactose) mass fragment. This fragment was absent from mass spectra with α2-6 linkages. Two sialyl oligosaccharides, which have not been reported previously, were tentatively identified. One comprises a N-acetyl neuraminic acid (Neu5Ac), two hexoses (Hex), and one N-acetyl hexosamine (HexNAc) residue ((Neu5Ac)1(Hex)2(HexNAc)1), and the other comprises one Neu5Ac and one Hex residue ((Neu5Ac)1(Hex)1).