Surface Plasmon Resonance

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Surface plasmon resonance (SPR) is well-known and well-regarded as a powerful and highly sensitive technique for the study of biomolecular interactions.

Surface Plasmon Resonance (SPR)

Within drug discovery, one common application of SPR is to measure the interaction of one molecule (in SPR termed ‘analyte’ – a small molecule, a protein, an antibody) with another molecule held on a sensor chip surface (in SPR termed ‘ligand’ – typically a protein or different antibody).

Under certain conditions, SPR can measure both the affinity (KD) of the interaction and the kinetics (on-rate (ka) and off-rate (kd). Consequently, these parameters are highly valuable at all stages of a drug discovery project.

Often a series of hits can be ranked and triaged by their binding affinities, their on-rates or their off-rates. However, the ideal metric to use will depend on the specific interaction or disease area being targeted and the particular phase of that project. 

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Investment in Biacore 8K for SPR

At Charnwood Discovery we use the Biacore 8K system for our SPR work. Recognized as a world-leader for biophysical characterization of molecular interactions it has many benefits including:

  • Low protein consumption – extracting the maximum amount of data from relatively small amounts of recombinant protein, allows us to work with difficult to purify targets
  • High throughput – hundreds to thousands of compounds can be screened in a day, enabling a rapid start to any project. With 8 channels to simultaneously work with, affinities are rapidly determined allowing key project decisions to be reached quickly
  • High sensitivity – the Biacore 8K has excellent sensitivity and can detect binding affinities from the picomolar to millimolar
  • High flexibility – many approaches to developing an SPR assay are available, helping you maximize the chances of successful assay development for your target. These range from different immobilization chemistries to competition-based or complex-based binding studies, 
assay development

Example SPR Assay Development Data

SPR-Figure-1

Figure 1. Example SPR assay development data

To the left, in Figure 1, we see some example assay development data. Here we assess the robustness of an immobilized protein surface through repeated binding cycles of one fixed concentration of positive control compound.

The response plot (top) and sensorgrams (bottom) show a decreasing binding response and changing dissociation kinetics throughout the course of the experiment. These are highly valuable insights before starting a large screening exercise.

By assessing the extent to which the binding response reduces with increasing cycle number we can gauge how robust our surface is and how amenable to long compound-binding studies it is.

Below in Figure 2 we see some representative binding data from a multi-cycle kinetics experiment.  which we measure the interaction between the protein BRD4 and tool compound MS436.

The data quality is very high and so we have high confidence in both the 1:1 binding model fit (left) and the steady-state affinity fit (right). There is close agreement in the affinity measured using both fitting models (1:1 Binding Kinetics: ka 6.1e5 M-1 s-1, kd 1.3e-1 s-1, KD 210 nM. Steady State Affinity: 190 nM).

SPR-Figure-2

Figure 2. Representative SPR sensorgrams and binding data.  

Our expert team can discuss your needs with you and how SPR is best placed to progress your drug discovery project.

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