MONOSACCHARIDE COMPOSITION ANALYSIS BY HPAEC

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Methods: Each sample was dissolved with 400 ¿L of nanopure H2O , and divided equally into two aliquots and transferred into pre-rinsed (with methanol) screw-cap tubes. One aliquot was designated for neutral and amino sugars analysis with the other aliquot allocated for sialic acids analysis. All aliquots were dried under a stream of nitrogen gas. The aliquots intended for neutral and amino sugars analysis were hydrolyzed with 400 ¿L of 2.0 N trifluoroacetic acid (TFA) at 100¿C for 4 h, whereas the aliquots for sialic acids analysis were hydrolyzed with 400 ¿L of 2.0 M acetic acid at 80¿C for 3 h. The hydrolysates were lyophilized, resuspended in H2O, sonicated for 7 min in ice and transferred to injection vials. A mix of standards for neutral and amino sugars, and for sialic acids with a known number of moles was hydrolyzed in the same manner and at the same time as the samples. Four concentrations of standard mixture were prepared to establish a calibration equation. The number of moles of each residue in the sample was quantified by linear interpolation from the calibration equation. The neutral and amino sugars, and sialic acids were analyzed by HPAEC using a Dionex ICS3000 system equipped with a gradient pump, an electrochemical detector, and an autosampler. The individual neutral and amino sugars and sialic acids were separated by a Dionex CarboPac PA20 (3 x 150 mm) analytical column with an amino trap. The gradient programs used the following mobile phase eluents: A - degassed nanopure water and B - 200 mM NaOH for neutral and amino sugars, and C - 100 mM NaOH and D - 1M sodium acetate in 100 mM NaOH for sialic acids. Injections were made every 45 minutes for neutral and amino sugars and every 40 min for sialic acids. All methods were based on protocols described by Hardy and Townsend (Hardy, M. R., and Townsend, R. R., "High-pH anion-exchange chromatography of glycoprotein-derived carbohydrates", 1994, Methods Enzymol. 230: 208-225).