Tagging of sugars with a fluorescent compound, 2-aminopyridine

Potential aldehyde groups of several monosaccharides and oligosaccharides were coupled with 2-aminopyridine by reductive amination with sodium cyanoborohydride. The product was isolated by adsorption on a Dowex 50 (H+) column, followed by washing, elution with aqueous ammonia and evaporation. The specimen was analyzed by paper electrophoresis at pH 5.0. Each sugar derivative gave a single spot in addition to one corresponding to excess 2-amino-pyridine when the paper was scanned under a UV lamp. The migration rates of these fluorescent sugars were related to their molecular weights and were independent of their linkage points and anomeric configurations. The reducing end sugar units of oligosaccharide derivatives could be identified by gas-liquid chromatography after hydrolysis of the 2-aminopyridine derivatives of the oligosaccharides.