Carbohydrate Composition Analysis of Glycoproteins by HPLC Using Highly Fluorescent Anthranilic Acid (AA) Tag

Summary

Oligosaccharides in glycoproteins by their very nature infl uence many aspects of protein function, e.g., half-life and activity/potency. Recombinant IgGs constitute a major portion of therapeutic proteins. Though the glycans in IgGs account for about 2% of the total weight, they influence biologic activity apart from antigen binding. Characterization of the carbohydrates is not only a regulatory requirement but it may allow understanding of structure-function of proteins. Current advances in analytical techniques permit structural elucidation of small quantities of glycoproteins. At a fi rst glance monosaccharide analysis may provide insight into the types of glycosylation similar to information afforded by amino acid composition. It is the only stand-alone technique by which individual sugar residues can be identifi ed and quantitated (mol/mol). Fluorescent anthranilic acid (AA) has been extensively used as a high sensitivity detection tag for carbohydrates. HPLC methods with fl uorescence detection described in this chapter are suitable for the analysis of monosaccharides (including sialic acids) on a routine basis. AA is used for the determination of hexoses and hexosamines, and o-phenylenediamine for sialic acids. These methods were validated and found to be highly reproducible compared to HPAEC-PAD and CE methods.