Isothermal Titration Calorimeter

Access or consultation: Dr. Vladimir Ermolenkov, 591-8890 or vermolenkov@albany.edu

Isothermal titration calorimetry is a technique which is used for measuring the energetics of biochemical reactions or molecular interactions at constant temperature. Experiments are performed by titration of a reactant into a sample solution containing the other reactant(s) necessary for reaction. After each addition, the heat released or absorbed as a result of the reaction is monitored. Thermodynamic analysis of the observed heat effects permits quantitative characterization of the energetic processes associated with the binding reaction. ITC can be used for study of ligand binding phenomena, enzyme-substrate interactions, and interactions among components of multimolecular complexes. The technique allows determination of the binding affinity, stoichiometry, and entropy and enthalpy of the binding reaction in solution.

The Low Volume Nano isothermal titration calorimeter (ITC) from TA Instruments uses two matched reaction vessels. The reference cell contains the buffer and the sample cell contains the reactant dissolved in the same buffer. The injection syringe with a titrant is inserted into the buret which accurately delivers the titrant to the sample cell at specified volumes and intervals. The buret also functions as the stirring mechanism for the reactants in the sample cell when the titrant syringe is installed.

Zero temperature difference is maintained between the sample and reference cell. The power required to maintain this zero difference is used as the calorimeter signal and is monitored as a function of time. If a reaction, producing/absorbing heat occurs in the sample cell, the heat required to maintain the zero difference decreases/increases by the amount of heat supplied/absorbed by the reaction, resulting in a peak in the thermogram.

The sample volume range for the Low Volume NanoITC is 300-700 μl. The injection syringe capacity is 50 μl. The minimum injection volume increment is 0.06 μl. ITC measurements can be performed in the temperature range of 2-80 °C.

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