MicroScale Thermophoresis (MST) and Temperature Related Intensity Change (TRIC) are important biophysical techniques with numerous advantages including minimal assay development time, very low protein consumption and the ability to eliminate false positives early.
MST and TRIC use thermo-optical measurements to quantify the interactions between ligands and biomolecules. Whilst both are relatively new techniques, Domainex has extensive experience using them and has used them to support numerous client programmes.
Domainex has invested in both the Dianthus NT.23PicoDuo1 and Monolith NT.Automated2 high-end instruments from NanoTemper.3 The Dianthus is a 384-well plate-based system that can screen several thousand samples in 24 hours, lending its use to medium-throughput screening. The instrument is able to take TRIC measurements highly efficiently. Whereas the Monolith is a 96-capillary-based system that is very sparing on protein use. It can take both Microscale Thermophoresis (MST) and TRIC measurements. A set of samples can be analysed in under 30 minutes, allowing for the efficient screening of targeted libraries and fragment collections.
TRIC measures the strength of the interaction between a test compound and target protein by detecting variations in the fluorescence signal, as a result of an IR-laser induced temperature change. The range of the variation in the fluorescence signal correlates with the binding of the ligand to the fluorescent target. Whereas, MicroScale Thermophoresis describes the directed movement of molecules within a temperature gradient that changes with the concentration of the binding partner.
Both MST and TRIC are highly sensitive techniques that allow the study of biomolecular interactions under close-to-native conditions.
The advantages of these techniques, over other biophysical methods, include:
- Target remains in solution and therefore in its native folded state, without the risk of binding sites being occluded by immobilisation
- Very low protein consumption
- No molecular weight restrictions on the molecules that can be analysed
- Eliminates false positives early
- Minimal assay development time
- Wide range of buffers can be used
- Supports challenging biology (e.g. ternary or quaternary systems)
- Readily allows competitive binding studies to be performed, and orthosteric and allosteric binders to be discovered
- Binding affinity determinations performed easily, with a large dynamic range (pM–mM)
State-of-the-art NanoTemper biophysical instruments – utilising the techniques of MST and Temperature Related Intensity Change (TRIC) – are at the core of Domainex’s fragment screening platform FragmentBuilder. We also use these instruments for screening and characterising compounds arising from our LeadBuilder virtual screens and subsequently through lead optimisation campaigns.
In our hands MST/TRIC is a very rapid and cost-effective approach to undertaking medium throughput compound screening. We take great care to perform high-throughput buffer screens to deliver optimised assays in a fast and efficient manner.
Our G9a case study demonstrates how we successfully used MicroScale Thermophoresis to screen a sub-set of our fragment library against the lysine methyl transferase, G9a, with a hit rate of 5.3 %. By using a saturating concentration of SAM, we ensured that the co-factor binding pocket was not available for fragment binding, and so we specifically identified substrate-competitive hits.