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The Biacore T200 system allows surface plasmon resonance spectroscopy for label-free measurement of biomolecular interactions in real-time, such as protein-protein, protein-DNA, protein-polysaccharide, enzyme-substrate or inhibitor, antibody-antigen, receptor-drug or protein-virus interaction. Extremely high sensitivity allows to detect binding of small (organic) compounds to various biomolecules. Affinities can be measured in the range of approx. 10 fM up to 1 mM. Besides association and dissociation rate constants, temperature-dependent measurements (4-45°C) can be performed in order to investigate thermodynamics of binding. The Biacore T200 is equipped with an autosampler and has a capacity of up to 384 samples, both allowing unattended operation.
Irene Schaffner PhD, Jakob Wallner BSc
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Methods & Expertise for Research Infrastructure
Surface Plasmon Resonance occurs when plane-polarized light hits a metal film at the interface of media with different refractive indices. When polarized light is directed towards a prism on a sensor chip with a thin metal film on top (e.g. gold), the light will be reflected by the metal film acting as a mirror. At a certain angle of incidence, the light will excite surface plasmons, causing a dip in the intensity of the reflected light. Photons of plane-polarized light can interact with the free electrons of the metal layer, inducing a wave-like oscillation of the free electrons, thereby reducing the reflected light intensity. The angle at which the maximum loss of the reflected light intensity occurs is called resonance angle or SPR angle. While the refractive index at the prism is not changing, the refractive index in the immediate vicinity of the metal surface will change when accumulated mass such as proteins adsorb on it. The change in refractive index at the surface of the metal film will cause a shift of the SPR angle.
The Biacore T200 system combines surface plasmon resonance with sensor chip technology to monitor the interaction between molecules in real time. To study the interaction between two binding partners, one interaction partner (= ligand) is attached to the surface of a sensor chip and the other one (= analyte) is passed over the surface in a continuous flow of sample solution. Binding of molecules to the sensor surface generates a signal response that is proportional to the mass of bound molecules and can be detected down to changes of a few picograms or less per square millimetre on the sensor surface, corresponding to concentrations in the picomolar to nanomolar range in the sample solution. The detection principle does not require any of the interactants to be labelled, thus, biomolecules can be analysed in their native state. The determined parameters comprise dissociation constant KD (measure for affinity), the binding rate constants kon and koff but also thermodynamic parameters of binding (enthalpy and entropy).