Figure 1: Isothermal titration calorimeter. The primary ligand (Protein) is placed in the sample cell (primary ligand is symbolized by circles) at a concentration on the order of at least 10-fold lower than the secondary ligand (protein, nucleic acid, carbohydrate, small molecule…etc.) that is placed in the syringe on top (Secondary ligand is symbolized by small rectangles). Several such injections are made during an experiment where both the ligands are mixed, and the release or absorption of a small amount of heat is detected. The output of the data (inset at top right) is transformed based on the differences measured for the heats of interaction of the given ligands. The heat from the reference cell is measured to account for the heat of dilution. |