Methodology to label mixed carbohydrate components by APTS

Labelling of carbohydrates with fluorescent dyes is of importance in the analysis of complex oligo- or polysaccharides. The complexity of the hydrolization mixtures of the oligosaccharides can be studied with separation methods after labelling. However, the procedures might provide unexpected phenomena. The experimental circumstances for labelling carbohydrates with 8-aminopyrene-1,3,6-trisulfonic acid were studied and the labelling efficiency of mono and oligosaccharides present in endotoxins was followed by capillary electrophoresis using LIF detection. Significant differences were observed in the labelling of the different sugar molecules, and the lowest reactivity with the dye was observed in the cases of amino-sugars. The results provide a basis for studies in determining the structures of the core parts and the O-chains of bacterial endotoxins.