TLC-LSIMS of neoglycolipids of glycosaminoglycan disaccharides and of oxymercuration cleavage products of heparin fragments that contain unsaturated uronic acid

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Heparin and chondroitin sulfate disaccharides have been investigated by high-performance (HP) TLC and liquid secondary-ion mass spectrometry (LSIMS) after conversion to neoglycolipid derivatives by reductive-amination with an aminolipid (dihexadecyl phosphatidylethanolamine, DHPE). Mobility on HPTLC was largely determined by the number of sulfate groups present, but was also influenced by the position of sulfate, monosaccharide composition and linkage. The mass spectra acquired directly from the TLC plate provided quasimolecular and fragment ions from which composition, including sulfate content, and sequence information was obtained at high sensitivity. Lipid DHPE conjugation and TLC-LSIMS were performed to analyse products of the oxymercuration reaction used to cleave unsaturated uronic acid (ΔUA) residues from glycosaminoglycan (GAG) fragments produced by enzymatic degradation with glycan lyases. Previously the identification of the product from ΔUA and the integrity of the remaining structures from oligosaccharides larger than disaccharide have not been made. Multiple and characteristic products of the cleaved ΔUA were detected and these can be used for identification of terminal ΔUA and its sulfate content. It was established with several disaccharides and a tetrasaccharide that glycosidic linkages and O- and N-sulfate groups are preserved in the remaining structures after removal ΔUA. These results indicate that the oxymercuration reaction will be applicable to generating series of GAG fragments containing unmodified sequences for biological activity studies.