Unraveling the Modulation of the Activity in Drugs Based on Methylated Phenanthroline When Intercalating between DNA...

Phenanthroline derivatives intercalate between base pairs of DNA and produce cytotoxic effects against tumoral cells. Nevertheless, modulation of their efficiency by substitution remains unclear in bibliography. In this work, the effects of methylation of phenanthroline, in number and position, when it intercalates between guanine-cytosine base pairs (GC/CG), were studied with PM6-DH2 and DFT-D methods including dispersion corrections. An analysis of the geometries, electronic structure, and energetics in the interaction was carried out for the studied systems. Our results were compared to experimental works to gain insight on the relation structure-interaction for the intercalated system with cytotoxicity. The trends are explained including not only intrinsic contributions to energy, ΔE_Pauli, ΔE_disp, ΔE_orb, and ΔE_elstat, but also the solvation energy, ΔE_Solv. A subtle balance between the number of stabilizing weak interactions (CH/π, CH/n, etc.) and steric hindrance seems to be related to the efficiency of such drugs.