Oligosaccharide sequence determination using B/E linked field scanning or tandem mass spectrometry of phosphatidylethanolamine derivatives

Abstract

Product ion mass spectral data of [M + H]+ ions of oligosaccharides, mainly tetra- and pentasaccharides, as their dipalmitoyl phosphatidylethanolamine derivatives were obtained using both liquid secondary ion mass spectrometry with B/E linked scanning and fast atom bombardment ionization with collision-induced dissociation/tandem mass spectrometry. Both methods give similar positive product ion spectra of equivalent high sensitivity (detection limits of approximately 50 pmol) that principally contain glycosidic cleavage ions retaining the reducing end of the molecule from which monosaccharide sequence can be deduced. A series of ions from fission of the phosphate ester bond together with glycosidic cleavage are present in the tandem mass spectra and B/E linked scan spectra when helium collision gas is used. Monosaccharide linkage position of isomeric molecules is reflected in the intensity of glycosidic fragmentation, without retention of the oxygen atom, with decreasing cleavage in the order 1-3 greater than 1-4 greater than 1-6 linkage. Fucose and N-acetylhexosamines show an increased degree of fragmentation over hexose sugars. The application of product ion spectra of derivatized oligosaccharides is demonstrated for characterizing mixed samples and also the acquisition of spectra directly from the silica surface of high-performance thin-layer chromatography plates.