ABSTRACT
The biological significance of cell surface carbohydrates in cell communication unfolds in a highly complex interplay with one another and other molecules, both membrane-anchored receptors and soluble proteins. Such secreted or membrane-bound proteins, which can recognize carbohydrates to form carbohydrate-protein complexes, are called lectins. They occur ubiquitously in all organisms and are involved in cell development, the immune system, signal transduction, and also states of disease and malignancy. Intracellular lectins often recognize core structures from glycoconjugate oligosaccharides, while cell surface and extra-cellular lectins frequently bind to terminal carbohydrate residues. The diversity of lectins, the molecular details of their interaction with glycans, the predominant multivalency effects occurring in carbohydrate-lectin interactions and the biological significance of carbohydrate-protein complex formation, including bacterial adhesion and orientational effects, are subject of this chapter.It might appear that the variety of possible lectin-carbohydrate interactions is large; however, it can be considered rather modest when compared to the amount of variations that is suggested theoretically. Still, the complexity of structures and the diversity of contexts in the carbohydrate regime present a significant challenge for glycobiological research. In an attempt to investigate the molecular details of carbohydrate-protein interactions, many different (multivalent) glycomimetics have been developed and intensively studied to deepen our understanding of glycobiology. Some of them are included here and discussed as tools of the glycosciences. This chapter is meant to let the reader acquire a taste of the fascinating field of glycobiology and its implications in human life.
