Practice question

In Surface Plasmon Resonance, signal intensity increases when soluble analyte specifically binds to ligand immobilized on the sensor surface, thereby increasing mass concentration and local refractive index within the evanescent field approximately 300 nm from gold film. This accumulation shifts resonance angle, recorded as increase in resonance units over time during association phase. Dissociation or buffer washing decreases signal. Evaporation, light absorption, or refractive index decrease would lower or destabilize signal rather than increase it. Specificity is validated using reference flow cells and concentration series for accurate kinetic characterization.