Molecular modeling and thermodynamics of the interaction between DNA base pairs and radon originated ionizing alpha radiation

Abstract

Ionizing alpha radiation (He2+) is known to adversely affect human DNA, but the biochemical reasoning is not clear yet. Relatedly, the present computational study was conducted investigating the effects of ionizing alpha radiation onto the Watson-Crick type DNA base pairs (nucleotides) Adenine-Thymine (AT’) and Guanine-Cytosine (GC’). The long-range cation (He2+)−π interactions were modeled for this purpose. A hybrid DFT functional of M06-2X was used with 6-31G(d,p) and 6-311G(d) basis sets at unrestricted level. The results showed that alpha radiation severely changed the considered base pairs’ hydrogen bond lengths and their interaction enthalpies and Gibbs free energies, however, the more drastic changes were observed in GC’ rather than AT’. This observation was also supported by frontier molecular orbital analyses performed. GC’ was more favored to form He2+ complexes (oxidize) than AT’ and consequently these complexes had more exothermic interaction energies (formed more spontaneously) than that of AT’. It could be highlighted that the molecular modeling proposed in this study would contribute to the elucidation of the uncertainty in this field.