A highly sensitive method for determination of molecular weights of neutral oligosaccharides by fluorescence labeling

The electrophoretic mobilities of pyridylamino derivatives of oligosaccharides in paper electrophoresis at pH 5 ((1979) J. Biochem. 85, 989--994) were independent of linkage positions, anomeric configurations, and acetamido groups up to a molecular weight of 1,700 and dependent on only their molecular weights. To increase the accuracy and sensitivity of the method, the pyridylamino derivative of a sample (10--50 pmol) was mixed with small amounts of pyridylamino derivatives of internal standard oligosaccharides of different molecular weights. The mixture was electrophoresed on a paper. Sections of paper corresponding to the standard oligosaccharides were extracted with water and then each extract was analyzed by high performance liquid chromatography with a fluorescence spectrophotometer. The molecular weight of the pyridylamino derivative of the sample was calculated by comparing its mobility with those of the pyridylamino derivatives of the internal standard oligosaccharides which were detected together with the sample on the chromatogram.