Surface plasmon resonance (SPR) technology is used to monitor and characterize molecular interactions. This method allows the detection of binding interactions with high sensitivity in real time, without the need for labeling. Researchers and biomanufacturers often use SPR to investigate binding kinetics and affinity between molecules.

How SPR works

SPR occurs when polarized light strikes an electrically conducting surface at the interface between two media. This generates electron charge density waves called plasmons, reducing the intensity of reflected light at a specific angle known as the resonance angle, in proportion to the mass on a sensor surface.

During SPR experiments, one molecule, known as the ligand, gets immobilized to a sensor chip made of a glass and a thin layer of a metal, such as gold. Researchers then infuse a solution containing the analyte over the sensor surface. This analyte interacts with the ligand, increasing mass and revealing association kinetics. During the interaction, polarized light is directed toward the sensor surface and the angle of minimum intensity reflected light is detected. This angle changes as molecules bind and dissociate, and the interaction profile is thus recorded in real time in a sensorgram.

SPR instruments

SPR instruments house the light source, chip, detector, one or more flow cells for the analyte solution, and other components needed to conduct SPR and capture the resulting data. They vary in sample capacity, from 15 samples per run (Biacore™ X100 system) for lab-scale characterization to as many as 4 608 samples per run (Biacore™ 8K+ system) for screening or characterization studies. Biacore™ SPR instruments allow you to obtain real-time affinity, specificity, and kinetics data. Through SPR instrument software, automated Biacore™ systems facilitate efficient characterization and data analysis for research or pharmaceutical development and quality control.

Advantages of SPR technology

The SPR detection principle does not require any of the interactants to be labeled, and measurements can be performed on complex mixtures, such as cell culture supernatants or cell extracts, as well as purified interactants. The identity of the interactant monitored in a complex sample matrix is determined by the interaction specificity of the partner attached to the surface. The SPR detection principle is non-invasive and works equally well on clear and colored or opaque samples.

Applications of SPR instruments

Use SPR for:

  • Protein interaction research
  • Drug discovery
  • Antibody characterization
  • Process development

SPR instruments FAQs

The following are frequently asked questions about SPR instruments:

What are SPR instruments?
SPR instruments are designed for characterization and screening of molecular interactions through surface plasmon resonance.

How are SPR instruments used?
SPR instruments can be used to study interactions involving (in principle) any kind of molecule, from organic compounds to proteins, nucleic acids, glycoproteins, and even viruses and whole cells. Since the response is a measure of the change in mass concentration, the response per molar unit of interactant is proportional to the molecular weight (smaller molecules give lower molar responses).