FLUOROMETRIC QUANTITATION OF AMINO-SUGARS IN THE PICOMOLE RANGE

A fluorometric method was developed for the convenient and quantitative assay of amino sugars over the concentration range of 10 nM-6 mM. Linear results were obtained for reaction mixtures containing 6 pmol-60 nmol hexosamine. The procedure involves the condensation of amino sugars with the fluorogenic reagent o-phthalaldehyde, at alkaline pH in the presence of 2-mercaptoethanol. Relative fluorescence intensities are then determined using excitation and emission wavelengths of 340 and 445 nm, respectively. The presence of 2-mercaptoethanol in reaction mixtures enhanced sensitivity of the assay and defined the excitation/emission spectra. Under the conditions described, amino acids also reacted with o-phthalaldehyde, yielding fluorescence intensities similar to those of amino sugars. The results suggest the applicability of fluorescence techniques in automated amino sugar analyses and the potential interference of other compounds containing primary amines.