Studying the Affinity of Different Ligands to Estrogen Receptor-á with Thermo Scientific Appliskan^®

This application note describes the performance of the Thermo Scientific Appliskan in the homogeneous Estrogen Receptor-á Competitor Assay based on fluorescence polarization. 17 â-estradiol and tamoxifen were used as test compounds to study their affinity to estrogen receptor-á.

Fluorescence polarization (FP) is used to study molecular interactions. The molecular size affects the rotation speed of the fluorescent molecule. The larger the molecule is, the slower it rotates. And the slower the molecule rotates during its fluorescent lifetime, the more the emission light stays polarized. Therefore, the larger the molecular size of the fluorescent complex is, the higher the polarization value (mP) will be. The binding or dissociation reactions lead to changes in the sizes of the molecular complexes so that molecular interactions can be studied by detecting changes in the polarization value.

Estrogens are a group of steroid compounds functioning as the primary female sex hormone. Estrogens act on target tissues by binding to estrogen receptors and that way activate or inactivate signaling pathways in cells. Cell proliferation is one of estrogens’ natural roles, but estrogens can also stimulate the development of breast cancer by causing uncontrollable cell growth.

The estrogen receptor assay can be used to study the affinity of different ligands to estrogen receptors (ER). Also, the effect of any chemical on the binding of the ligand to ER can be studied. ERá is well-known as a drug target for the treatment of breast cancer. Molecules which block the action of estrogens by binding to the receptor or directly to estrogen can be used to prevent the negative effects of estrogen. In this assay 17 â-estradiol and tamoxifen were used as test compounds. 17 â-estradiol is the main endogenous human estrogen and tamoxifen is a drug molecule used in breast cancer treatment.