Surface Plasmon Resonance
Also known as: SPR, surface plasmon, SPR biosensing
Surface Plasmon Resonance (SPR) is a real-time, label-free technique for detecting and monitoring biomolecular interactions at a sensor surface by measuring changes in the refractive index caused by ligand binding. Developed by Kretschmann in 1971 and applied to biosensing by Liedberg, Nylander, and Lundström in 1983, SPR is now a gold standard for measuring binding kinetics (association and dissociation rates) and equilibrium binding constants in protein interactions, antibody-antigen recognition, and drug discovery.
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When to use it
Apply SPR to measure binding kinetics and affinity for any biomolecular interaction: protein-ligand, protein-protein, antibody-antigen, or cell-cell interactions. SPR requires immobilization of one binding partner (the analyte) on the sensor surface; this may affect kinetics compared to solution measurements. SPR is ideal for screening hundreds of ligands, optimizing binding, and validating structural models.
Strengths & limitations
- Label-free: no fluorescent, radioactive, or enzymatic labels needed; measures refractive index change directly
- Real-time kinetics: captures both association (ka) and dissociation (kd) rates in a single experiment
- High-throughput capable: multiple experiments in parallel using sensor arrays or multiplex formats
- No sample consumption: analyte solution passes over the chip and can be collected if needed
- Requires immobilization of one binding partner; attachment chemistry may impair binding or introduce steric effects
- Nonspecific adsorption to the sensor surface can confound results
- Low molecular weight ligands (< 500 Da) produce small refractive index changes, reducing sensitivity
- Baseline drift and sensor aging affect long-term reproducibility
Frequently asked
Why can SPR measure binding kinetics directly?
SPR detects binding and unbinding events in real time by monitoring refractive index changes at the sensor surface. The association rate (ka) is evident from the rising phase when ligand is injected; the dissociation rate (kd) is evident from the falling phase when ligand is removed. The true equilibrium constant Kd = kd/ka combines both.
What is the difference between kinetic and steady-state binding constant determination?
Kinetic Kd = kd/ka is extracted from the ratio of dissociation and association rates. Steady-state Kd is determined by fitting binding at equilibrium (plateau phase) versus ligand concentration. Both methods yield Kd, but kinetic analysis provides additional information about mechanism.
How does surface immobilization affect SPR results?
Immobilization can slow dissociation rates (kd) because the receptor is restricted in motion; solution kinetics often show faster dissociation. Association rates (ka) may also be affected by surface crowding and steric effects. Careful surface chemistry and low receptor density minimize these artifacts.
Sources
- Kretschmann, E. (1971). Determination of optical constants of metals by excitation of surface plasmons. Zeitschrift für Physik, 241(4), 313-324. link ↗
- Liedberg, B., Nylander, C., & Lundström, I. (1983). Surface plasmon resonance for gas detection and biosensing. Sensors and Actuators, 4, 299-304. DOI: 10.1016/0250-6874(83)85036-7 ↗
- Homola, J. (2008). Surface plasmon resonance sensors for detection of chemical and biological species. Chemical Reviews, 108(2), 462-493. DOI: 10.1021/cr068107d ↗
How to cite this page
ScholarGate. (2026, June 3). Surface Plasmon Resonance. ScholarGate. https://scholargate.app/en/spectroscopy/surface-plasmon-resonance
Which method?
Set this method beside its closest kin and read them side by side — the library lays the books on the table; the choice is yours.
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