CALORIMETRY

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

Isothermal titration calorimetry(VP-ITC and ITC200 models): principally dedicated to the study of molecular interactions. By measuring the reaction heat at constant temperature, ITC allows the direct determination of the stochiometry (n), the equilibrium constant (Ka), and the variations of enthalpy (ΔH) and entropy (ΔS) induced by an association reaction. The last two terms contain information about the type of interaction and reflect the real nature of the forces driving the binding. By performing titrations at several temperatures, it is possible to measure the variation of heat capacity (ΔCp) related to the formation of a molecular complex.

ITC is an equilibrium solution technique and is truly the only direct method to quantify Kd values without the use any label. ITC is relatively artefacts-free as is not affected by the optical properties of the samples and 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.

Applications

• Characterization of molecular interactions established by proteins, nucleic acids, antibodies, lipids, sugars, etc. and any small molecules (peptides, compounds, metals, etc.).
• Assessment of biological activity.
• Assessment of the effect of molecular structure changes on binding mechanisms, dimerization, etc.
• Enzyme kinetics.

Differential scanning calorimetry(VP-DSC model): 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.

Application

• Protein stability and folding
• Liquid biopharmaceutical formulations
• Process development
• Protein engineering
• Antibody domain studies
• Characterization of membranes, lipids, nucleic acids and micellar systems
• Assessment of the effects of structural change on a molecule’s stability
• Measurement of ultra-tight molecular interactions
• Assessment of biocomparability during manufacturing

Devices :     ITC 200 (MicroCal)

                    VP- ITC (MicroCal)

                   PEAQ-DSC

                    PEAQ-ITC

Bibliography