The FRET (Fluorescence Resonance Energy Transfer) technology allows to detect distances of a few tens of angstroms between
2 fluorophores, and is therefore a technique of choice to study molecular interactions.
Here, it allows to measure the binding between a membrane receptor fused to a fluorophore and a ligand fused to another fluorophore. The binding is measured on living whole cells. The assay is performed under homogeneous conditions and does not require any washing.