The effect of intermolecular interactions on the electric dipole polarizabilities of nucleic acid base complexes

In this Letter, we report on the interaction-induced electric dipole polarizabilities of 70 Watson–Crick B-DNA pairs (27 adenine–thymine and 43 guanine-cytosine complexes) and 38 structures of cytosine dimer in stacked alignment. In the case of hydrogen-bonded Watson–Crick base pairs the electrostatic as well as the induction and exchange-induction interactions, increase the average polarizability of the studied complexes, whereas the exchange-repulsion effects have the opposite effect and consistently diminish this property. On the other hand, in the case of the studied cytosine dimers in stacked alignment the dominant electrostatic contribution has generally much larger magnitude and the opposite sign, resulting in a significant reduction of the average polarizability of these complexes. As a part of this model study, we also assess the performance of recently developed LPol-ds reduced-size polarized basis set. Although being much smaller than the aug-cc-pVTZ set, the LPol-ds performs equally well as far as the excess polarizabilities of the studied hydrogen-bonded complexes are concerned.