Majority of proteins for therapeutic use, such as growth hormones, cytokines, and antibodies are glycoproteins (proteins with carbohydrate chains). The pattern of carbohydrate structures on glycoproteins is important in influencing the biological properties of the proteins, such as protein stability, pharmacokinetics, antigenicity, cell adhesion, protein targeting, and many other intercellular recognition processes. Current biological techniques only provide heterogeneous mixtures of glycoproteins with non-human glycoforms, causing inconsistent efficiency and immunogenicity. We are developing a variety of chemical (e.g. novel glycosylation reactions, and glycoconjugation reactions) and biological (e.g. bioengineering expression hosts) methods to create homogenous glycoproteins for both basic research and biomedical applications.