Polyvalent Interactions on Biological Interfaces

Multi- and polyvalent interactions between lectins and glycans are of fundamental importance for the interaction of biological surfaces. Lectins are proteins with defined glycan-recognition domains on the surface of viruses and bacteria as well as of plant and animal cells. Affine inhibitors of lectins are, therefore, suitable for clarifying the function of defined carbohydrate stmctures, when they are used as a competitive binding partner. They also provide an opportunity for pharmacological intervention. The phenomenon of 

FIGURE 6.22 The selectin-ligand interaction recruits leukocytes to the vascular endothelium, which allows them to adhere. Following the inflammatory mediators, leukocytes migrate from the blood vessels toward the focus of inflammation. Source Fasting et al. [89], figure 21. Reproduced with permission of John Wiley Sons. 

Selectins are C-type lectins that form calcium-dependent bonds with their physiological ligands. The leukocyte L-selectin and the E- and P-selectins presented on the endothelium recognize all the sialyl Lewis tetrasaccharide ligands (sLe Fig. 6.23) that are presented by membrane-bound proteins or lipids on both interacting cellular surfaces (Fig. 6.22). 

In studies on selectin inhibition with functionalized dendritic glycopolymers (Fig. 6.24), Papp et al. were able to demonstrate with a competitive SPR-based measurement system that galactose acts as a minimal selectin ligand, if available in sufficient concentration [104]. Compared to a tetravalent architecture 

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