Monoclonal antibodies to sweet taste proteins. II: Development of two different immunoassays for thaumatin and monellin

Two different types of immunoassays for the detection and quantitation of thaumatin and monellin, plant proteins with intense sweet taste properties, have been developed. A tandem enzyme-linked immunosorbent assay (ELISA) was developed for the quantitation of thaumatin, in which one monoclonal antibody (mAb) raised against thaumatin (TM-1-D) was used as the solid-phase "capture" antibody, while the second mAb antibody (TM-1-C) was labeled with biotin. A standard curve for the assay was obtained and had a correlation coefficient of 0.987; the detection limit of the immunoassay was 5 ng/ml. Using a single anti-monellin mAb, a competitive enzyme immunoassay (EIA) was developed for monellin. The competitive binding of biotinylated monellin and known monellin standards with mAb 4.2E was examined; this assay had a minimum detection limit of 30 micrograms/ml.