DNA base pairs: the effect of the aromatic ring on the strength of the Watson–Crick hydrogen bonding

Abstract

The aromatic ring in DNA bases affects the Watson–Crick binding strength. Our quantum-chemical analyses, which compare the hydrogen bonding between the DNA bases and unsaturated analogs lacking the aromatic ring, reveal that this arises not from π-resonance assistance but from the electron-withdrawing (purines) or electron-donating (pyrimidines) effect of the heteroatom-containing ring on the frontier atoms. This electron redistribution modulates the electrostatics, steric Pauli repulsion, and σ-orbital interactions upon hydrogen bonding.