A theoretical study of methylation and CH/π interactions in DNA intercalation: methylated 1,10-phenanthroline in adenine–thymine base pairs

Abstract

The study of CH/π interactions in DNA model intercalated systems has been carried out with the popular intercalator 1,10-phenanthroline (phen) and several methyl derivatives, changing number and position, and the adenine–thymine tetramers (AT/TA) where thymine also contains a methyl group. Density Functional Theory (DFT) was used for the calculations, by means of improved functionals including dispersion effects. Our results given by the AIM analysis confirm the existence of these CH/π interactions and the energy decomposition analysis shows a perfect direct correlation between the number of CH/π interactions found and their ΔE_int. Moreover, despite the important role of dispersion energy in the systems with more methyl groups, it is not yet enough to compensate the Pauli repulsion term, ΔE_Pauli, and the orbital contribution, ΔE_orb, and the electrostatic contribution, ΔE_elstat, become crucial for the stabilization of the structures in the intercalation process.