Equilibrium dialysis using chromophoric sugar derivatives.

Equilibrium dialysis has been used to examine the binding affinity of ligands to proteins. It is a simple and reliable method, which requires only inexpensive equipment. For analysis of lectin-sugar interactions, the lectin and sugar are placed in the individual chambers separated by the membrane to allow the sugar to diffuse into the lectin chamber. After equilibrium has been reached, the concentrations of the sugar in both chambers are determined to evaluate the sugar-binding affinity of lectin. In this chapter, an example of the equilibrium dialysis experiment using the chromophoric derivatives of galactose and N-acetylgalactosamine is demonstrated, which reveals the difference in the affinity as well as specificities of two different carbohydrate-binding sites present in the B-chains of the plant lectin ricin.