Protein Interaction

Microcalorimetry allows the direct, thorough and accurate thermodynamic characterisation of interactions between molecules in solution and of biochemical reactions in general. Two types of calorimeters are available depending on the focus of the study that one wishes to perform:

• Isothermal titration calorimetry (VP-ITC , ITC200 and PEAQ-ITC): principally dedicated to the study of molecular interactions. ITC the only direct method to quantify Kd values in solution without the use any label. ITC is relatively artefacts-free as it is not affected by the optical properties of the samples and it is not limited by the ligand or protein sizes. A direct experiment in the ITC200 instrument detects affinities ranging from nanomolar to low millimolar, although an indirect experiment (competition with a ligand of known affinity) can be used in to extend from pico- to sub-millimolar.

• Differential scanning calorimetry (VP-DSC and auto PEAQ-DSC): principally dedicated to the study of the thermal stability of macromolecules and their complexes. By measuring the variation of heat capacity (ΔCp) as a function of temperature, DSC allows to determine directly the variations of enthalpy (ΔH) and entropy (ΔS) and the melting temperature (Tm) related to each structural transition. DSC systems are powerful tools for characterizing the stability of proteins and other biomolecules that require no assay development, labeling or immobilization. The automated PEAQ-DSC system, available on the platform, offers a high throughput and sensitive analysis of protein stability with low sample consumption.