Biosensor-based interaction analyses are enjoying increasing popularity in both quality control and in research and development. Conventional biosensors, such as surface plasmon resonance systems, are based on alterations in the macroscopic properties of the measurement surface. However, switchable DNA layers, featuring switchSENSE® technology, facilitate the active movement of the tethered molecules. This kind of “active” biosensor not only offers information about measurement parameters such as binding affinity and kinetics, but also about biophysical parameters such as melting point, protein size, protein activity, etc. Erythropoietin (EPO) and anti-EPO antibodies are used here as examples to illustrate the potential of this technology both in buffer systems and in serum. more