Fluorescence Polarization Immunoassay for Alternaria Mycotoxin Tenuazonic Acid Detection and Molecular Modeling Studies of Antibody Recognition

A simple and rapid method of fluorescence polarization immunoassay (FPIA) for detection of Alternaria mycotoxin tenuazonic acid (TeA) was described. In this study, the tracers TeAH-FITC and TeAH-DTAF were synthesized from hapten 5-(sec-butyl)-3-(1-hydrazonoethyl)-4-hydroxy-1H-pyrrol-2(5H)-one (TeAH) and different fluoresceins isothiocyanate isomer I (FITC) or 5-([4,6-dichlorotriazin-2-yl]amino)fluorescein hydrochloride (DTAF), respectively. The established FPIA showed an IC50 value of 3.0 μg/mL with a detection limit of 0.13 μg/mL for TeAH based on the tracer of TeAH-FITC, and with the same properties of 7.3 and 0.93 μg/mL based on TeAH-DTAF. The former gave better assay sensitivity than the latter, that the 2,4-dichloro-s-triazine group of TeAH-DTAF may affect the specific recognition of tracer and antibody. Models of the lowest energy conformation and the molecular electrostatic potential isosurface studies revealed that the –C=N–N– and –CHCH3(CH2CH3) groups were the characteristic chemical groups in anti-TeAH antibody-analyte recognition via molecular modeling, which could create a theoretical guide for hapten design of small molecules and provide the traditional theory with empirical proof.