Temperature-induced ultraviolet difference absorption spectrometry for determination of enthalpy changes: Binding of 4-methylumbelliferyl glycosides to four lectins

Abstract

Raising the temperature in a single mixture of a lectin and a chromophoric glycoside allows determination of the binding enthalpy. This is made possible by continuously monitoring the displacement of the complex from its equilibrium concentration with a sensitive difference absorption spectrophotometer. The method is illustrated with the following lectins: concanavalin A, soybean agglutinin, peanut agglutinin and Erythrina cristagalli agglutinin. The ligands are 4-methylumbelliferyl glycosides. The binding enthalpies found range from −60 kJ · mol −1 for the Galß1 → 3GalNAc-ßglycoside and peanut agglutinin to −30 kJ · mol −1 for a monosaccharide glycoside and the other lectins.