Radioligand Binding Assays

Radioligand binding assays are used to characterize the binding of a drug to its target receptor. They can provide information on both the affinity and mode of interaction of the drug with its receptor. For example, radioligand binding assays can provide information on whether the test drug is binding to the endogenous ligand binding site or is instead acting on another allosterically coupled binding site, such as a blocker of the receptor-coupled ion channel.

Three types of receptor binding experiments may be performed:


Saturation Binding experiments, where binding of an increasing series of radioligand concentrations is measured at equilibrium and analysed to determine its binding constant (affinity constant; K, or dissociation constant; Kd) and the concentration of specific binding sites for the radioligand (Bmax).

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Competition Binding experiments, where the binding of one or more fixed concentrations of a radioligand is measured at equilibrium in the presence of an increasing series of concentrations of a non-labelled compound and analysed to determine the half maximal inhibitory concentration (IC50) and the equilibrium inhibitor constant (Ki).

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Kinetic Binding experiments, where the binding of one or more concentrations of radioligand is measured at an increasing series of time points, and analysed to estimate association (kon) and dissociation (koff) rate constants

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Equilibrium dialysis (EqD) is useful for binding studies with soluble targets and small molecules. In other binding assays, when a target is immobilized or part of membrane fragment the free ligand can be easily washed away, but this is not possible with soluble targets. However, if placed in a chamber with a dialysis membrane then bound versus free ligand can be distinguished when binding has reached equilibrium.

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in vitro Assays and screening list

Specializing in both standard and custom in vitro assays, we are focused on providing the right assays for target identification & validation, assay development, screening, hit-to-lead validation to help identify candidate compounds for preclinical and clinical development.

Below is a complete list of available assays.

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