Determination of constituents of sulphated proteoglycans using a methanolysis procedure and gas chromatography/mass spectrometry of heptafluorobutyrate derivatives

A major impediment in the analysis of glycosaminoglycans is the difficulty to cleave quantitatively the glycosidic bonds because of the stabilisation of glycosidic bonds and of the relative instability of the liberated constituents. This manuscript describes a modified procedure of methanolysis in the presence of barium acetate, reducing the destruction of uronic acids and increasing the cleavage yield. The reaction products could be identified and analysed quantitatively by GC and GC/MS of the heptafluorobutyrate derivatives of O-methyl glycosides of monosaccharides (for keratan sulphate and chondroitin sulphate B), or as a mixture of O-methyl glycosides of monosaccharides and of disaccharides (for the other sulphated glycosaminoglycans). Quantitative molar ratio between the different monosaccharide constituents (including the linkage region constituents) could be obtained, even when proteoglycans also contain classical N-glycans or O-glycans.