Biacore systems generate data on interaction between proteins and other molecules, such as other proteins, nucleic acids or small molecules. This technique exploits the phenomena of surface plasmon resonance (SPR).
One of the molecules of the binding pair will be considered as the "ligand" and will be immobilised on the surface of the sensor chip. A solution with the other partner of the interaction (called the "analyte") will be injected over the immobilised ligand. Changes in the index of refraction at the surface where the binding interaction occurs are detected by the hardware and recorded as RU (resonance units) in the control software. As the analyte binds the ligand an increase in SPR signal will be observed, when the analyte dissociates the signal will decrease.
The injection of a series of concentrations of the analyte will generate curves that will be evaluated by fitting algorithms that compare the raw data to well-defined binding models. These fits allow determination of a variety of thermodynamic constants: the association and dissociation rates (ka and kd) and the equilibrium constant KD.