Abstract: The optimal condition for AFB₁ conjugating to nanogold particles was obtained by studying the preparation and the reaction. Optimum pH for conjugation was determined to be 7.4, reaction time was 5 min, and the least stable content of McAb to colloidal gold in five diameters(10.7—67.4 nm) was 0.07, 0.051, 0.033, 0.019, 0.012 mg/L gold solution, respectively. Combination of McAb with nanogold particles was also characterized with TEM, IR spectra and immunoreactivity. The results show that the titer of McAb increased obviously. Colloidal gold has a powerful ability to quench the McAb fluorescence via a nonradiative energy transfer mechanism. The fluorescence quenching data were analyzed according to Stern-Volmer equation. The binding constant of reaction was obtained. The data of enthalpy and entropy proved that the main interactions were London-van der Waals force and hydrogen bond between colloidal and McAb. From the synchronous spectrum colloidal gold has not obvious effect on the conformation of McAb. It was proposed that the small change of conformation of McAb was the reason of increase of titer, affinity and stability.

Key words: Aflatoxin B₁, AFB₁ antibody, Nanogold colloid, McAb Probe, Interaction mechanism