Microscale Thermophoresis

The infrared laser creates a localized heat source, producing a microscopic temperature gradient within the solution. Molecules redistribute along that gradient, and their thermophoretic mobility reflects properties such as size, charge, hydration shell, and conformation. Because interactions can change these properties, the fluorescence trace provides a way to detect molecular behavior without requiring a surface.

Binding can change a molecule’s size, charge, hydration shell, or conformation, all of which influence thermophoretic mobility. MST therefore detects interaction-dependent changes in the fluorescence response rather than relying only on a direct visual signal of complex formation. This is especially useful when the biochemical interaction produces a measurable mobility change under solution conditions.

Compared with surface-based assays, MST examines partners in solution and does not depend on immobilizing one component. That distinction matters for proteins, nucleic acids, or ligands whose behavior could be difficult to assess after attachment to a surface. The near-native format also supports interaction measurements for systems that are challenging to immobilize or purify.

A typical measurement uses a fluorescently detected sample containing one interaction partner and a series of concentrations of the other. The infrared laser locally heats each sample, while fluorescence records the resulting redistribution. Comparing responses across the titration allows researchers to characterize the interaction and determine its binding affinity.

Small sample volumes are a practical feature of the technique, making MST suited to biochemical measurements when material is limited. The essential setup combines fluorescence detection with localized infrared heating, rather than a surface-bound assay format. Samples are measured in solution, which helps preserve conditions close to those experienced by the interacting molecules.

In biochemistry, MST can examine protein-protein, protein-DNA, and protein-ligand interactions. Its value extends beyond a single interaction class because the same readout links binding-dependent molecular changes to an affinity measurement. Researchers can consequently use it to characterize biochemical partners or investigate interactions that are difficult to immobilize or purify for surface-based approaches.