Nucleic Acids Research, 2002, Vol. 30, No. 20 4567-4573
© 2002 Oxford University Press
Thermodynamic characterization of the multivalent binding of chartreusin to DNA
Departament de Biologia Fundamental i Ciencies de la Salut, Universitat de les Illes Balears, Palma de Mallorca, Spain and 1 Departamento de Biología Molecular y Celular, Instituto de Biología Molecular de Barcelona, CSIC, Jordi Girona 1826, 08034 Barcelona, Spain
*To whom correspondence should be addressed. Tel: +34 93 400 61 76; Fax: +34 93 204 59 04; Email: jpmbmc{at}cid.csic.es
Characterization of the thermodynamics of DNA drug interactions is a very useful part in rational drug design. Isothermal titration calorimetry (ITC), differential scanning calorimetry (DSC) and UV melting experiments have been used to analyze the multivalent (intercalation plus minor groove) binding of the antitumor antibiotic chartreusin to DNA. Using DNA UV melting studies in the presence of the ligand and the binding enthalpy determined by ITC, we determined that the binding constant for the interaction was 3.6 x 105 M1 at 20°C, in a solution containing 18 mM Na+. The DNAdrug interaction was enthalpy driven, with a
Hb of 7.07 kcal/mol at 20°C. Binding enthalpies were determined by ITC in the 2035°C range and used to calculate a binding-induced change in heat capacity (
Cp) of 391 cal/mol K. We have obtained a detailed thermodynamic profile for the interaction of this multivalent drug, which makes possible a dissection of
Gobs into the component free energy terms. The hydrophobic transfer of the chartreusin chromophore from the solution to the DNA intercalating site is the main contributor to the free energy of binding.
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