Bindingassays

Binding assays are experimental procedures that measure the interaction between two or more molecules, typically a binding partner such as a ligand and a target molecule like a receptor, antibody, enzyme, or nucleic acid. The primary aim is to characterize binding properties, including affinity, capacity, kinetics, and specificity, and to evaluate how other substances influence the interaction. These assays are foundational in biochemistry, pharmacology, and diagnostics.

Common formats include direct binding assays, in which a labeled ligand binds to immobilized or soluble targets, and saturation or equilibrium binding assays, which vary ligand concentrations to derive binding parameters. Competitive binding assays use an unlabeled competitor to displace the labeled ligand, enabling estimation of affinity. Immunoassays such as ELISA are a subset of binding assays that rely on antigen-antibody interactions to quantify molecules.

Detection methods span radiolabels, fluorescent or chemiluminescent labels, and label-free approaches. Historically, radioligand binding was widely used, but fluorescence-based and chemiluminescent readouts are now common. Label-free techniques, including surface plasmon resonance and related platforms, monitor binding in real time without labels and can provide kinetic constants.

Data interpretation centers on important metrics: the dissociation constant (Kd) reflects affinity, while Bmax denotes binding capacity. In competitive formats, IC50 and, with appropriate analysis, Ki quantify inhibitory potency. Applications span drug discovery and receptor characterization, immunodiagnostics, and assay development for research and clinical use.

Key considerations include nonspecific binding, assay equilibrium and temperature, ligand stability, and appropriate controls such as blank, non-specific binding, and saturating ligand conditions. Safety and regulatory requirements may apply for radiolabeled components.