Voltammetric evaluation for the binding of wheat germ agglutinin to glucosamine-modified magnetic microbead

Binding of wheat germ agglutinin (WGA) on glucosamine-modified magnetic microbeads was investigated with voltammetry. A magnetic bead was considered as a cell, and the beads with amino groups were modified with the sugar by using a cross-linking reagent. To evaluate the binding, glucose labeled with an electroactive daunomycin was prepared as a probe. After WGA and the beads were mixed in 0.1 M phosphate buffer (pH 7.0), the labeled glucose was added to the solution. The binding was monitored from the changes in the electrode response of labeled glucose because the labeled glucose was held to the binding site of WGA for the sugar. In contrast, other lectin not having the binding site to glucosamine or glucose was incubated with the glucosamine-modified beads. As a result, the change of peak current was not observed. Therefore, it is clear that the binding of WGA to glucosamine moiety on the bead surface selectively takes place. This method would be powerful for evaluation of interaction between protein and sugar chain existing at cell surface.