An assay for carbohydrate-binding activity of lectins using polyamidoamine dendrimer conjugated with carbohydrates.  The carbohydrate-binding activity of lectins was examined using polyamidoamine dendrimer conjugated with carbohydrates (sugar-PD). When a C-type lectin, CEL-IV, was mixed with melibiose-PD, large complexes with a diameter of about 1 μm were formed. Changes in the amount of CEL-IV/melibiose-PD complex as an indication of lectin activity were measured sensitively by Rayleigh scattering. The carbohydrate specificity of the lectin was determined on the basis of inhibition of complex-formation by individual carbohydrates. It is suggested that various lectins can also be measured using sugar-PDs to which different carbohydrates are attached.