Advancing Accurate Quantification of Protein-Ligand Interactions: Differential Scanning Calorimetry as a Precision...

Area of Science:

• Biochemistry
• Structural Biology
• Drug Discovery

Background:

• Quantifying protein-ligand binding energetics is crucial for drug screening but often hindered by issues like ligand aggregation and hydrophobicity.
• BCL-2 is a key oncogenic target, making it an important model for evaluating new screening methodologies.

Purpose of the Study:

• To evaluate differential scanning calorimetry (DSC) as a quantitative, label-free method for screening protein-ligand interactions.
• To assess DSC's performance with poorly soluble compounds and compare it with other established techniques.

Main Methods:

• Differential scanning calorimetry (DSC) was used to profile nine BCL-2 inhibitors across different solvent systems (neat DMSO, 10% DMSO, S3).
• The S3 solvent system (10% DMSO, 90% sulfobutylether-β-cyclodextrin) was employed to address solubility challenges.
• Results were compared with time-resolved fluorescence energy transfer (TR-FRET), in vitro assays, and MM/GBSA calculations.

Main Results:

• DSC successfully generated thermal transition temperatures and thermodynamic parameters (ΔH, ΔG) for ranking binding strengths.
• The S3 solvent system improved thermal signal quality, effectively managing solubility issues.
• DSC results demonstrated high accuracy in detecting binding energetics, correlating well with TR-FRET, in vitro assays, and computational methods.

Conclusions:

• Differential scanning calorimetry (DSC) is a robust and material-efficient tool for thermodynamic screening of BCL-2 ligands and other poorly soluble compounds.
• DSC serves as a practical complement to isothermal titration calorimetry, particularly when solubility or kinetic limitations are a concern in drug discovery.