Glycosylation is a major posttranslational modification that produces heterogeneity in a protein and results in a group of structurally different species called glycoforms. Protein-associated oligosaccharides are large, structurally diverse molecules, and the biological roles ascribed to them are numerous. Some of these functions include the following: intercellular adhesion, adhesion of microorganisms, including viruses to target cells, and modulation of immunological activity of polypeptide chains.