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Isothermal Titration Calorimetry

The TA Instruments Nano-Series calorimeters represent the highest sensitivity and unmatched flexibility for the investigation of biological samples. The Nano ITC is focused on the measurement of ligand binding and reaction kinetics, with increased baseline stability and more tolerance to environment temperature fluctuations. New heat sensing architecture ensures the highest data quality for reproducible results using the new easy-to-use NanoAnalyze data analysis software.

Life Science professionals know that the thermodynamic driving forces of macro-molecular interactions are critical parameters for the design of effective biomedical and pharmaceutical treatments. Calorimetry has become the method of choice for characterizing the thermodynamic driving forces of critical molecular interactions and defining molecular stabilities. Calorimetric analyses are based on accurately measuring the rate of heat absorbed or evolved when the biomolecule of interest interacts specifically or nonspecifically with another macromolecule or ligand (binding studies). The TA Instruments Nano ITC Standard Volume or Nano ITC Low Volume instruments are powerful tools to accurately and efficiently perform these important measurements. The Nano ITC instruments are designed to improve laboratory productivity and efficiency by performing high-sensitivity analyses on nanomolar quantities of biomolecule. This is accomplished through a combination of a high sensitivity calorimeter, accurate and stable temperature control, and efficient titrant delivery.

Characterizing Binding Interactions by ITC

All binding events are accompanied by the evolution or absorption of heat (a change in enthalpy, ΔH). In a single ITC experiment a full thermodynamic characterization of the binding reactions can be obtained. With the appropriate experimental design, fundamental information about the molecular interactions driving the process, as well as the stoichiometry of binding (n) and the binding constant (Ka) is generated. The first figure shows a typical incremental titration (20, 5 μL injections) of an inhibitor, 2’-CMP, titrated into RNase A; n = 1, Ka = 1.69 x106 M-1, and ΔH = -58 kJ mol-1. The second figure shows the same experiment, plotting the individual integrated peak areas vs the ratio of the two binding molecules. As the binding sites become saturated, the amount of heat produced with individual injections decreases. The resulting titration curve reveals valuable information on the enthalpy (ΔH), entropy (ΔS) and overall Gibbs free energy (ΔG) of the reaction taking place in the calorimeter. ITC is a powerful analytical tool and considered the most sensitive assay technique for characterizing the fundamental driving forces of molecular binding reactions.

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