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University of Connecticut Health Center - Know Better Care The Gregory P. Mullen NMR Structural Biology Facility & Biophysical Core Facility

Isothermal Titration Calorimetry (ITC)

CD

Microcal VP-ITC

This is a walk-up instrument or samples can be dropped off to be run for an additional fee. Training on the instrument is also available. Scheduling of this instrument is done through the FACES (http://faces.ccrc.uga.edu/) scheduling system. See the Calendars and Scheduling page for more information. Visit the Research Store for current pricing.

ITC measures the heat released or absorbed when two or more molecules interact to determine the thermodynamic parameters of the interaction. The technique is quantitative and works with non-labelled samples. Specifically ITC measure the binding affinity (Ka), Enthalpy (ΔH), and binding stoichiometry for the interaction. Based on the equation

ΔG = -RTlnKa = ΔH - TΔS

the Entropy (ΔS) and Gibbs free energy (ΔG) can also be determined. In conjunction with SPR, which measures on and off rates, a complete thermodynamic and kinetic profile can be determined for biological interactions in solution. ITC is becoming a very popular secondary screening in drug discovery due to the full thermodynamic profile that is measured.

Typical protein concentrations for ITC are 10 to 50 uM with a 1.8 ml sample volume which is placed in the cell. The ligand (protein, small molecule, nucleic acid) concentration is typically 50 to 500 uM with a volume of around 500 ul for the syringe. In general the ligand concentration is 10X higher than the protein. It is critical that the protein and ligand buffers be identical as heats of dilution will occur if they are different. Extensive dialysis of both the ligand and protein is recommended. TCEP is highly recommended over B-mercaptoethanol or DTT.