Why do A·T and G·C self-sort? Huckel aromaticity as a driving force for electronic complementarity in base pairing

摘要

Density functional theory computations and block-localized wavefunction analyses for 57 hydrogenbonded base pairs document excellent linear correlation between the gas-phase association energies and the degree of aromaticity gain of paired bases (r = 0.949), challenging prevailing views of factors that underlie the proposed electronic complementarity of A.T(U) and G.C base pairs. Base pairing interactions can polarize the p-electrons of interacting bases to increase (or decrease) cyclic 4n + 2p electron delocalization, resulting in aromaticity gain (or loss) in the paired bases, and become strengthened (or weakened). The potential implications of this reciprocal relationship for improving nucleic acid force-fields and for designing robust unnatural base pairs are discussed.