Table 3. Isothermal Titration Calorimetry of Human BRD2 and BRD3 with Selected 9H-Purine Compounds^a.

protein/ligand	[P] (μM)	[L] (μM)	KD (nM)	ΔHobs (kcal/mol)	N	TΔS (kcal/mol)	ΔG (kcal/mol)	LE
BRD2(1)/7d	518	20	4444 ± 162	–6.62 ± 0.09	0.99 ± 0.011	0.44	–7.06	0.37
BRD3(1)/7d	532	20	2037 ± 105	–7.17 ± 0.09	1.01 ± 0.009	0.33	–7.50	0.39
BRD2(1)/11	488	20	1421 ± 60	–5.65 ± 0.04	1.02 ± 0.006	2.06	–7.71	0.39
BRD3(1)/11	510	20	2037 ± 105	–7.17 ± 0.09	1.01 ± 0.009	0.33	–7.50	0.38

^aTitrations were carried out in 50 mM HEPES, pH 7.5 (at 25 °C), 150 mM NaCl, and 15 °C while stirring at 1000 rpm. In both cases the protein was titrated into the ligand solution (reverse titration). Titrations were performed in triplicate. Ligand efficiencies (LE) have also been calculated where ΔG values were available (LE = ΔG/N where N is the number of non-hydrogen atoms).