Biophysical Assays

Surface plasmon resonance (SPR) is a very popular technique in drug discovery in both pharmaceutical industry and academia. The technique is used to detect interactions between molecules, such as protein-protein, protein-small molecule, protein-nucleic acid, protein-carbohydrate, etc. The parameters that can be measured by SPR include dissociation constant (KD), association rate constant (kon) and dissociation rate constant (koff). SPR can measure interactions in real time with high sensitivity and without the need for labeling.

Thermal shift assay (TSA) is a widely used method in academia and industry for discovering potential compounds to the target protein for structural genomics and drug screening ^[1]. TSA can effectively screen for factors that affect protein stability. In addition, by monitoring the shift in the melting temperature (Tm) of proteins, TSA can also provide quantitative data on protein-ligand binding affinity.

Isothermal titration calorimetry (ITC) is a useful tool for understanding the full thermodynamic picture of binding reactions. In addition, it is considered the gold standard technique for measuring the interaction between two molecules. ITC determines the binding constant (affinity) by direct titration. ITC also determines the standard enthalpy change of the interaction, which leads to the most important thermodynamic parameters of the binding process, i.e., the Gibbs energy, enthalpy, and entropy.

Microscale thermophoresis (MST) is a biophysical assay method for quantifying interactions between molecules (e.g., proteins and small molecules). It measures the strength of the interaction between two molecules by detecting variations in fluorescence signal as a result of an IR laser-induced temperature change. MST is highly sensitive to almost any change in the nature of the molecules, allowing for precise quantification of molecular events independent of the size or nature of the specimen under study.