ABSTRACT
The glycosylation of a protein involves co-and post-translational reactions that have significant impact on expression levels, structural integrity, spe cific activity, immunogenicity, and solubility [1-3]. Mammalian cells pro duce a wide range of oligosaccharide structures, and the type of structures depends on the species [4]. Common sources of heterogeneity include varia tion in the sites of attachment of oligosaccharides, differences in branching, and terminal modification with different sialic acid residues. The polypep tide chains appear to direct glycosylation at individual sites, unique to a single protein or class of proteins. Each of these sources of oligosaccharide heterogeneity can have significant effects on biological properties [5]. The structure of glycoprotein glycans can be influenced not only by cell culture methodology, but also by culture time [6,7].
