Carbohydrates are the most abundant class of biomolecules found in nature. They are complex structures that exist from simple monosaccharides (ex: D-glucose, D-mannose, D-galactose, N-acetyl-D-glucosamine), disaccharides (ex: sucrose, lactose) to much larger polysaccharides (ex: starch, cellulose, chitin). In living organisms, most carbohydrates exist in conjugated forms such as glycolipids, glycoproteins and proteoglycans. Cell surface carbohydrates are found at the outermost layer, so they serve as the initial contact to cell's enviroment by interacting with other biomolecules such as proteins. Protein folding also requires the participation of carbohydrates. Thus, in addition to serving the role as energy sources for all living cells, carbohydrates are involved in many biological processes including cell-cell communication and adhesion, cell growth, differentiation, transformation and metastasis. Microoranisms such as virus and bacteria also exploit specific carbohydrate structures displayed on cell surface of host to initiate infections.

Studying carbohydrate-protein interactions involved by lectins, enzymes, antibodies, toxins, hormones and others is the key to gain understanding of fundamental biochemical processes. The acquired knowledge can be used to guide future design and synthesis of carbohydrate-based analogs to inhibit key biological recognitions. Some of the inhibitors can be developed futher to become novel therapeutics to treat diseases and improve human health. During last century, cancer has quickly evolved to becoming the second most common cause of mortality, next to heart disease, and during recent years, many infectious diseases have emerged as a major public concern due to the development of multidrug resistence.

Bacteria express a thick, mucos-like layer of polysaccharides which are strain-specific. These polymers are vital to the microorganism because they form a highly hydrated shell that separates the cell from its environment and they modulate the intake of nutrients and ions and output of wastes. In addition, bacterial polysaccharides can act as virulence factors that enable the pathogen to adhere to host or to solid surfaces. and they also aid the microorganism to evade host immune response. Lipopolysaccharides and capsular polysaccharides are the two classes of polymers expressed by bacteria. Because they are unique to bacterial strains, they are ideal candidates to be incorporated in a vaccine to raise carbohydrate-specific antibodies. Unfortunately, carbohydrates are poor immunogens, as they are incapable of eliciting strong host immune response. Howver, chemically conjugating bacterial polysaccharides to an immunogenic protein can create a class of glycoconjugates which can stimulate host to generate long term immunity.