How It Works: Surface Plasmon Resonance
Many functional proteomic technologies require time-consuming labeling steps and still produce little more than yes or no answers as to whether proteins interact. Surface plasmon resonance (SPR) allows for label-free detection in real time and provides rich information about the interaction kinetics. Under total internal reflection conditions, light shining at a specific angle at a thin film of gold between two media with different refractive indices (e.g., glass and buffer) creates an evanescent wave that interacts with free electron clouds in the metal and reduces the intensity of reflected light. The so-called resonance angle at which this phenomenon occurs depends on the refractive index at the surface and hence changes according to the mass of any molecules bound to the surface. By tracking the change of this angle, research tools can detect molecular binding and dissociation. Biacore makes the T100 instrument depicted here.
Editor's note: The original depiction of surface plasmon resonance on this page, posted March 1, contained errors pertaining to the nature of the technology. These errors have been corrected as of March 15.
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