Carbohydrate weak interactions

The recognition is the binding of a carbohydrate by a specific receptor, which is usually part of a protein (enzyme, immunoglobuUn, lectin). The process is due to the sum of weak interactions (van der Waals-London, hydrogen bonds) that may results in high association constants. 

The chief function of lectins in animals is to facilitate cell-cell contact. A lectin usually contains two or more binding sites for carbohydrate units some lectins form oligomeric structures with multiple binding sites. The binding sites of lectins on the surface of one cell interact with arrays of carbohydrates displayed on the surface of another cell. Lectins and carbohydrates are linked by a number of relatively weak interactions that ensure specificity yet permit unlinking as needed. The interactions between one cell surface with carbohydrates and another with lectins resemble the action of Velcro each interaction is relatively weak but the composite is strong. 

To explore the concept of using terminal carbohydrate moieties as crucial elements, Hindsgaul et al. [36] developed a new class of compounds — glycohybrids. These compounds represent a unique combination of glycoside moieties combined with amino acids and do not occur in natural systems. Cognizant with the typical weak carbohydrate-protein bindings, the idea was to assist carbohydrate-based weak interactions by additional amino acids that may provide the extra contact points for specific bindings. 

The results indicate that most of the carbohydrate residues, such as Gal and GalNAc, weakly interact with Gd " " and Mn. The cyclitols (inositols), on the other hand, form with these metal ions unique complexes that are based on the geometry (stereochemistry) of the multiple hydroxyl groups. Due to stereochemical requirements, a unique, metal-ion binding-site (for Gd ) on gluconamides is also observed, although this interaction is weak. 

Astrom, E. and Ohlson, S. (2006) Detection of weakly interacting anti-carbohydrate scFv phages using surface plasmon resonance. J. Mol. Recognit. 19, 282-286... 

DNA-binding proteins, lectins, lipids, carbohydrates, and estimation of binding constants and weak interactions. 

Two other types of biological ligands that can be used in WAC are enzymes and lectins.As an example, the enzyme a-chymotrypsin has weak interactions with many of its inhibitors, which has allowed the separation of these inhibitors under isocratic conditions on an immobilized a-chymotrypsin column. Lectins are non-immune system proteins that bind carbohydrates with low-to-moderate association constants, allowing these agents to be used... 

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