Biacore is a label-free molecular interaction analyzer based on Surface Plasmon Resonance (SPR), which can real-time detect the binding kinetics and affinity of proteins, small molecules and other substances.

Pull-down assay (ligand pull-down) is an application of Biacore. The bait protein is immobilized on the chip to capture interacting molecules from mixed samples. The captured molecules are then eluted and identified by mass spectrometry, enabling discovery of unknown interacting proteins and small molecules.