Exploring The Effects Of Substituents On The Binding Energy In Hydrogen-bonded Complexes Containing Adenine And Thymine

The optimal structures and binding energies of seventeen substitutional thymine andadenine hydrogen-bonded complexes have been obtained theoretically and the effects ofsubstituents on the binding energies are explored. The calculation results show that theinteraction between trifluridine and adenine is stronger than that between thymine andadenine both in the gas and in the aqueous environment. This conclusion is in agreement withthe fact that the association of trifluridine and adenine has precedence over the association ofthymine and adenine. Compared with CF3, three stronger electron withdrawing groups SO3H,CN, NO2can increase the binding energy between thymine and adenine, suggesting that thethymine substituted by these three groups may also provide a potential anticancer application.Atoms in molecules theory and the natural bond orbital analysis indicate that N H…Nhydrogen bonding is the strongest, N H…O=C is the next, while C H…O=C is the weakest.Atoms in molecules theory and the natural bond orbital analysis also indicate that the orbitaloverlap interactions play a significant role in these hydrogen bonds. The binding energies indifferent solvent environments show that the interaction between monomers is weaker inpolar solvent.