Lectins association constants

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 carbohydrate-binding sites of WGA are probably situated at the surface of the protein molecule. The pH dependences of association constants for lectin-chitotriose binding indicate that an ionizable group, pK = 3.9, is probably involved in complex-formation.494,504 This observation is especially noteworthy, inasmuch as protein carboxyl... 

Equilibrium-dialysis experiments revealed two 2-acetamido-2-deoxy-D-galactose binding-sites per molecule of soybean agglutinin.544 This value was confirmed by gel filtration of the lectin on a column equilibrated with a radioactive ligand. The noninteracting, identical sites exhibited an association constant of Ka = 3.0 X 104 liter.mole-1 for this 2-acetamido-2-deoxyhexose. 

The BS I that had been 125I-labeled by a diazonium coupling technique626 was employed in a study of lectin-receptor density on the B erythrocyte.191 Scatchard analysis of the binding data demonstrated a variation in receptor density among type B individuals from 7.2 X 104 to 13.4 X 104 sites per erythrocyte.191 Likewise, apparent association-constants for lectin-cell interaction varied from 1.1 X 107 to 2.9 X 107 M ... 

Association Constants of Antigen-Antibody, Hapten-Antibody and Ligand-Lectin Interactions... 

Firstly, immobilized lections may be used. Lectins are proteins that display high binding selectivity for defined carbohydrate structures and sugar residues [23, 24]. The interaction with the glycosylated enzyme is non-covalent, and binding strength depends on the specific association constants. This approach is cost intensive because it affords the production of a further immobilized protein. 

For each lectin, we will first give its description according to the recommended nomenclature. On the following line will be given its molecular weight and that of the subunits (a, j8...) as well as the association mode of the latter, the number (n) of recognition sites, and the possible metals present. We will end with the association constant with a good substrate. 

The association constants of a number of lectin-carbohydrate complexes have been determined by affinity electrophoresis and are pH-dependent. ... 

Theoretical aspects of affinity electrophoresis have been discussed and the applicability of the technique for determination of dissociation constants of protein-ligand complexes demonstrated. The pH dependence of lectin interactions with sugars has been determined by affinity electrophoresis. Association constants of dextrans and isomaltose oligosaccharides for myeloma anti-dextran have been determined using the technique. 

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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