Which physical property does SPR detect?
Surface Plasmon Resonance detects minute shifts in refractive index at the sensor chip interface, which directly correlate with mass concentration variations close to the gold surface. When light excites surface plasmons, resonance occurs at a specific angle dependent on the dielectric environment. Adsorption or binding of biomolecules increases the refractive index within the evanescent field, shifting the resonance angle. This optical readout is independent of magnetic or pH changes and does not measure bulk optical density alone. Sensitivity to refractive index enables quantitative, real-time monitoring of unlabeled interaction kinetics and equilibrium binding parameters.
Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.