. Author manuscript; available in PMC: 2008 Aug 26.

Published in final edited form as: J Med Chem. 2005 Dec 29;48(26):8209–8219. doi: 10.1021/jm050902g

Table 1.

Comparison of thermodynamic parameters for daunorubicin, WP631 and WP762 binding to herring sperm DNA^a.

	K_obs (M⁻¹)	ΔG_obs (kcal mol⁻¹)	SK	ΔG_pe (kcal mol⁻¹)	ΔG_t (kcal mol⁻¹)	ΔG_calc (kcal mol⁻¹)^c	ΔH (kcal mol⁻¹)	−TΔS (kcal mol⁻¹)
Daunorubicin^b	1.6 × 10⁷	− 9.7	0.9	− 2.0	− 7.7	−7.7	− 10.5	0.8
WP631^b	2.7 × 10¹¹	− 15.3	1.6	− 3.9	− 11.4	−11.9	− 30.2	14.9
WP762	7.3 × 10¹²	− 17.3	1.5	− 3.7	− 13.6	−12.6	− 33.8	16.6

K_obs (M⁻¹) is the binding constant for the interaction of the ligand with salmon testes DNA in 18 mM Na⁺ at 20°C. ΔG_ob_s is the binding free energy calculated from ΔG_obs = −RTlnK. SK is the slope of the plot of logK_ob_s versus log[Na ⁺] shown in Fig. 4. ΔG_pe and Δ G_t are the polyelectrolyte and non-electrostatic contributions to the binding free energy (ΔG_pe = SKRTln[Na⁺]) evaluated at 16 mM Na⁺. Enthalpy values were determined by DSC (Fig. 3).

Data adapted from.¹²

Calculated using the HINT software to obtain a HINT score, which was divided by −451 to obtain the ΔG_calc.¹⁸–²²