Based on the principle of surface plasmon resonance (SPR), Creative Proteomics provides accurate and rapid affinity assays. The throughput, flexibility and sensitivity of SPR affinity assays make it possible for researchers to study any binding, including: antigen-antibody affinity assays, protein-small molecule and peptide affinity assays, protein-small molecule drug affinity assays, etc. It is possible to study a wide range of molecules, from ions, fragments and small molecules to proteins and viruses.
Surface Plasmon Resonance (SPR)
Surface Plasmon Resonance (SPR) affinity assay is an optical-based label-free detection technique for real-time detection of molecular interactions between two or more molecules.SPR affinity assay has high throughput, flexibility and sensitivity for early drug discovery and preclinical drug screening. For example, it has powerful advantages in screening small molecules or peptides (enzymes or antibodies, etc.), enabling rapid and accurate screening of candidate drug molecules to save costs for subsequent studies.
Principle
SPR affinity detection detects molecular interactions by tracking signal changes on a sensor chip. the SPR signal is measured in reaction units (RU), which is approximately equivalent to a protein surface concentration of 1 pg/mm2. During the interaction of two molecules, the SPR signal generates a sensing map, which can be visualized in real time (Figure 1). The general binding reaction consists of three phases: binding, equilibrium and dissociation. Fitting these sensorgram data to a mathematical model allows scientists to calculate the association (Ka) and dissociation (Kd) rate constants and ultimately determine the binding affinity. Unlike Isothermal titration calorimetry (ITC), SPR allows for complete kinetic parameters to be obtained to assess all effects of binding and dissociation as well as antibody affinity.
In antibody affinity measurement, the antibody to be analyzed is first captured by a high-affinity anti-IgG antibody immobilized on the surface of the sensor chip. A series of concentrations of antigen are then sequentially injected onto the surface of the chip. Based on the sensorgram, mAbs with superior properties can be selected according to kinetic parameters. The identification of specific regions (epitopes) is more promising in drug discovery than the discovery of tight-binding antibodies because binding affinity maturation can be achieved by standard protein engineering. Therefore, based on a bivalent analyte model involving two binding reactions, we are able to provide assays to identify antibodies that bind to two different epitopes. First, a universal antibody (such as rabbit anti-mouse immunoglobulin) is covalently attached to the surface of the chip, and then the primary antibody is captured by the previously attached universal antibody. After the unsaturated sites are blocked, the injected antigen will bind to the primary antibody to form an Ab-Ag complex. Subsequent administration of a second monoclonal antibody for assessment of binding affinity, if the second antibody binds a different individual epitope, a characteristic sensorgram will be observed.
Figure 1 Principle of Surface Plasmon Resonance [3]
SPR analysis can be applied for:
Interaction specificity
Interaction affinity
Kinetic binding parameters
Hermodynamic parameters
Biologically active concentration of an analyte
We provide SPR analysis services to study biomolecular interactions.
Study a wide variety of biological molecules by SPR, including small molecules (<100 Da), proteins, nucleic acids, lipids, bacteria, viruses, and whole cells. Most published SPR studies involve protein-protein interactions, with antibody-antigen interactions representing a major direction. We provide high-sensitivity instruments and accurate experimental protocols to help customers conduct research on small molecules, lipids and nucleic acids.
Sample Requirement
| Customer Provided | Requirement |
| Antibodies, proteins, peptides, compounds, small molecules, etc. | * Buffer: PBS, HEPPS, etc. without organic reagents, without Tris * Antigen sample: Protein (peptide) >2mg, concentration >0.5mg/ml, purity >90% * Protein sample (with antibody): >200ug, concentration >0.5mg/ml, purity >90% * Peptide samples: >200ug, concentration >1mg/ml, purity >90% * Compound small molecule: >1mg, concentration >1mg/ml (dry powder is best) |
References
- The United States Pharmacopeia (USP 35-NF 30)
- Surface plasmon resonance for gas detection and biosensing. Liedberg Bo, Sensors and Actuators, 1983, 4.
- Sensitivity Enhancement of Transition Metal Dichalcogenides/Silicon Nanostructure-based Surface Plasmon Resonance Biosensor. Sci Rep 6, 28190 (2016).
