SPR Principles


Surface plasmon resonance (SPR) is a technique for detecting changes in refractive index at the surface of a sensor that enables measurement of biomolecular interactions in real-time in a label free environment. The fully integrated SPR sensor offered in Pioneer systems is a highly sensitive, static, and stable optical design. Light emitted by an LED passes through a polarizer and reflects off of the gold sensing surface. A detector array then measures the reflected light and calculates the angle at which light has coupled through the gold surface as an attenuation or dip in the signal.

As mass accumulates at the sensor surface during a binding interaction, the refractive index increases and an increase in signal is observed. After the sample is replaced by buffer, mass will decrease at the surface during the dissociation phase and with a subsequent decrease in the resonance unit response. By repeating this cycle at different concentrations, calculations can be made for ka (on-rate) and kd (off-rate) of the interaction.


Dynamic injection SPR (diSPR) provides enhanced information content, including binding affinity characterization, without requiring the time-consuming individual concentration dilutions necessary with other SPR instrumentation. In OneStep® Injections, Taylor dispersion is exploited to generate an analyte concentration gradient that provides a high-resolution dose response in a single injection for enhanced biophysical characterization and increased throughput. Analyte gradients conform to Taylor dispersion theory for accurate modeling of the analyte concentration during the titration. A full analyte titration over 3-4 orders of magnitude in concentration is recorded within a few minutes. The technique also provides a method for determination of the analyte diffusion coefficient and can be used to assess whether the analyte is heterogeneous or aggregated — valuable information in biophysical analyses. View related articles.