FIGURE 3.

Isothermal titration calorimetry. Titration of heparan sulfate into TAT-PTD. (A) Heat flow. The peptide concentration in the reaction cell is 78 μM. Each peak corresponds to the injection of 2 μL (every 5 min) of heparan sulfate at a concentration of 500 μM. Buffer is 10 mM Tris and 100 mM NaCl at pH 7.4. Temperature is 28°C. (B) Heats of reaction h_i (integrated from the heat flow in A) as a function of the molar ratio of heparan sulfate/TAT-PTD. Unfilled diamonds represent experimental data. The solid line is the least-square fit to these data using the binding model described by Eq. 2 with the parameters listed in Table 1.