Do C—H^...O hydrogen bonds contribute to the stability of nucleic acid base pairs?

The possible formation of inter-base C—H...O hydrogen bonds in A·T, A·U and certain non-Watson–Crick base pairs is examined. A geometrical analysis in conjunction with implications for the thermodynamic stability of the base pairs suggests that C—H...O hydrogen bonds could form in nucleic acid base pairs. They may alleviate destabilizing interactions that would arise if an unsatisfied hydrogen-bond acceptor were present and mediate secondary hydrogen-bonding effects in these base pairs.