Effects of oxygenation on the intercalation of 1,10-phenanthroline-5,6/4,7-dione between DNA base pairs: a computational study.

The effects of oxygen in positions 4,7 and 5,6 of phenanthroline when this ligand intercalates between guanine-cytosine and adenine-thymine DNA base pairs (GC/CG and AT/TA) have been studied at the M06-2X/6-31+G(d,p) level of calculation. We focused on the changes in the structure, stabilization and energy contributions in the analysis of the interaction. The obtained trends in stabilization are explained by a model including repulsive Pauli (ΔEPauli) contributions, and attractive dispersion (ΔEdisp), orbital (ΔEorb) and electrostatic (ΔEelstat) contributions to energy. When no solvation is considered, the intrinsic ΔEelstat contribution results are crucial for the stabilization of the system. However, the inclusion of the solvation energy ΔEsolv can reverse the final stability trend of the systems becoming, thus, the driving force of the process. Therefore, the solvent will have a relevant influence in the potential cytotoxicity of the intercalation drugs.