Interactions of adenine–thymine base pair with potassium cation and water clusters

Abstract

The structures of Ade-Thy-K+(H2O)n (n = 0–6) clusters were determined, and the interaction mechanism of K+-base pair (A-T) in water clusters was elucidated. The non-hydrated Ade-Thy-K+ shows a planar structure, while the complex transforms into a stacked form when the water molecules are involved. It is noted that K+ no longer connects to adenine but is tricoordinated with thymine and the adjacent water from n = 3, and then forms a tetracoordinate ion from n = 4. The RDG, AIM, and EDA combined with interaction energy analyses show that the interaction between K+ and base pair weakens gradually when the first four water molecules are involved successively, and then strengthens for n = 5, 6. The interaction between K+ and the A-T base pair is dominated by an electrostatic power, followed by dispersion, whereas the interactions between adenine and thymine are always dominated by dispersion from n = 1 to 6.