Surface Plasmon Resonance Assay Services

SPR is a real-time, label-free biophysical technique that monitors changes in the refractive index at a sensor chip interface as molecular binding events occur. It allows for the precise determination of association (ka) and dissociation (kd) rate constants, from which the equilibrium dissociation constant (Kd) is calculated. It is widely used for characterizing binding kinetics, affinity, and concentration-dependent interactions.

Our SPR services are suitable for a broad range of interaction types, including antibody–antigen, protein–protein, peptide–protein, and small molecule–protein complexes. We also support the analysis of more complex biomolecules such as virus-like particles (VLPs), transmembrane proteins, Fc receptors, and T cell receptor–MHC peptide complexes. These capabilities make our platform highly adaptable to both conventional and challenging binding systems.

Standard assay projects using purified protein or antibody samples are typically completed within two to three business days. For more complex analytes, such as membrane protein nanodiscs, peptides, or multimeric complexes, the workflow may extend to three to five business days. This timeline includes method development, sensor chip preparation, kinetic runs, and data processing. SPR services are performed on a first come first serve basis.

Clients are asked to provide the ligand and analyte identities, their intended roles in the assay (e.g., immobilized vs. injected), the concentration and buffer composition of each sample, and documentation on purity (ideally ≥90%). A minimum volume of 100 µL per interaction is recommended. Following review of your request, our team will guide you in optimizing sample conditions to ensure compatibility with SPR instrumentation and assay parameters. If a tested protein is available in our catalog, we can provide the protein for SPR testing for free.

We utilize both direct and indirect immobilization methods depending on the biochemical properties of the ligand. Direct immobilization involves covalent attachment to the sensor chip via amine coupling. Indirect (capture-based) methods rely on molecules such as streptavidin, Protein A/G, or anti-His antibodies to anchor tagged ligands. These strategies are chosen based on the desired assay orientation, ligand activity, and sample purity requirements.

Our Biacore SPR system is capable of measuring interactions within a broad dynamic range, with affinities from picomolar (pM) to low millimolar (mM), on-rates ranging from 10² to 10⁶ M⁻¹s⁻¹, and off-rates from 10⁻⁶ to 1 s⁻¹. This level of sensitivity enables the characterization of high-affinity therapeutics as well as weak or transient interactions, such as those seen in TCR-pMHC systems or Fc receptor binding.

Upon completion, clients receive detailed kinetic analysis reports, including fitted binding curves, raw sensorgrams, residual plots, and calculated kinetic parameters (ka, kd, Kd). We also provide the raw data files in standard formats (.csv, .txt), along with a Certificate of Analysis if required. Our team is available to provide interpretation support and guidance on result application in your downstream research.

Yes, we routinely handle assays involving weak or transient interactions. Depending on the project, we can adjust surface densities, flow rates, buffer compositions, and regeneration protocols. For interactions approaching mass transport limits or requiring high sensitivity, we implement low-temperature runs and optimized chip chemistries to improve resolution and binding signal fidelity.

While our SPR services are intended for research use, our workflow follows strict SOPs that align with GLP-like standards. We maintain complete documentation, including instrument calibration logs, usage records, dual data backups, and detailed electronic and paper-based experimental records. This makes our assay data appropriate for preclinical reports, early-stage regulatory filings, or investigational documentation.

Absolutely. SPR is routinely applied in lead candidate selection, affinity maturation, epitope binning, and isotype/format comparison. We support screening campaigns for mAbs, bispecifics, and Fc variants, including low-affinity FcγR interactions or pH-dependent binding assessments.