Calorimetric titrations of gp120 with a) UM-24, b) KR-41 and c) KR-42 at 25°C in PBS at pH 7.4. The concentration of gp120 was 2 μM; the UM-24 and KR-41 concentrations were 25 μM, and the KR-42 concentration was 50 μM. VP-ITC titration calorimetric system used from MicroCal/GE Healthcare (Northampton, MA, USA). The calorimetric cell (~1.4mL), containing gp120 from the YU2 strain dissolved in PBS (Roche Diagnostics GmbH, Mannheim, Germany), pH 7.4, was titrated with different peptides dissolved in the same buffer.