Carbohydrate-Mediated Information

The property of conformational restriction in polysaccharides make them candidates for being the initial self-ordering molecules of prebiotic evolution. This same property in the complex carbohydrate moiety of glycoproteins is the basis of carbohydrate-mediated information transfer through cell surface oligosaccharides interacting with each other or with lectin-like proteins in cell-cell recognition processes. 

In addition to their important roles as stored fuels (starch, glycogen, dextran) and as structural materials (cellulose, chitin, peptidoglycans), polysaccharides and oligosaccharides are information carriers they serve as destination labels for some proteins and as mediators of specific cell-cell interactions and interactions between cells and the extracellular matrix. Specific carbohydrate-containing molecules act in cell-cell recognition and... 

Selectins are plasma membrane lectins that bind carbohydrate chains in the extracellular matrix or on the surfaces of other cells, thereby mediating the flow of information between cell and matrix or between cells. 

A key property of carbohydrates in their role as mediators of cellular interactions is the tremendous structural diversity possible within this class of molecules. Carbohydrates are built from monosaccharides, small molecules, lypically containing from three to nine carbon atoms, that vary in size and in the stereochemical configuration at one or more carbon centers. These monosaccharides may be linked together to form a large variety of oligosaccharide structures. The sheer number of possible oligosaccharides makes this class of molecules information rich. This information, when attached to proteins, can augment the already immense diversity of proteins. 

The evidence is increasing that glycosylation of integrins plays important modulatory roles in the function of these molecules. In other studies it appears that the glycosylation of at least one extracellular matrix glycoprotein, namely laminin, is important in cellular adhesion mediated by integrins. So far most information on the role of carbohydrates in integrin-mediated adhesive interactions has been obtained for the fibronectin receptors... 

The manifold chiral information readily available in customary carbohydrates provides an attractive approach to a chiral modification of metal carbenes that may be applied to either metal-mediated stereoselective organic synthesis via sugar auxiliaries or to carbohydrate synthesis via organometallic methodologies [107, 108]. The sugar moiety can be incorporated into metal carbenes by well-established procedures such as nucleophilic addition to the metal-coordinated carbene carbon atom or conjugate addition to the vinylogous position in alkenyl or alkynyl car-... 

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