Estrogen receptor binding assay method for endocrine disruptors using fluorescence polarization.

Area of Science:

• Biochemistry
• Environmental Science
• Assay Development

Background:

• Endocrine disruptors pose risks to environmental and human health.
• Accurate and rapid detection methods are crucial for monitoring these compounds.
• Estrogen receptor (ER) binding assays are key for identifying estrogenic activity.

Purpose of the Study:

• To develop a rapid, simple, and nonhazardous assay for endocrine disruptors.
• To utilize fluorescence polarization (FP) and ER binding for high-throughput screening.
• To characterize the binding kinetics and cooperative effects of ligands with ER.

Main Methods:

• Developed a fluorescence polarization (FP) assay using a fluorescein-labeled estradiol derivative and estrogen receptor (ER).
• Performed Scatchard and Hill plot analyses to determine binding constants and cooperativity.
• Conducted competitive binding assays with unlabeled 17beta-estradiol (E2) and other known estrogenic compounds.

Main Results:

• A 17alpha-fluorescein-labeled estradiol derivative demonstrated high affinity and suitable characteristics for ER binding.
• Scatchard analysis indicated positive cooperative binding, suggesting ER dimerization.
• The assay determined a dissociation constant (Kd) of 10.4 nM and a Hill coefficient of 1.63 for the labeled ligand.
• Competitive assays yielded an IC50 of 2.82 nM for 17beta-estradiol (E2), with a Ki of 0.65 nM.
• Varied Hill coefficients were observed for other tested compounds, indicating different binding mechanisms.

Conclusions:

• The developed ER-FP assay is a rapid, simple, and nonhazardous method for detecting endocrine disruptors.
• The assay effectively characterizes ligand-ER interactions, including cooperative binding.
• This method provides a valuable tool for screening environmental samples and chemicals for estrogenic activity.