Abstract
AbstractThis study is aimed at explaining the preference for AT and CG pairings and the possible insertion of other tautomeric DNA base pairs such as GenolT, that respect energetic and steric requirements including at least two hydrogen bonds and 11 ± 0.5Å distance between the 9‐CH3 of purine and 5‐CH3 of pyrimidine. The calculated free energy of formation ΔΔG at the DFT B3LYP/6‐31G*‐PCM/BEM level pointed out the CG and AT pairs as the most favored, followed closely by GenolT, in good agreement with Michaelis–Menten first order kinetics (CG ≈ AT > GenolT). Unusual DNA base pairs complexes such as AG (BEM) and CT (PCM) resulted to be stable, but it is very difficult to assume that they are likely to be included in the double strand DNA. The calculated enthalpy and dipole moments of isolated DNA bases agree well with experiment. The free energy of hydration, ΔGhyd, was found to depend on the electrostatic term, while cavitation‐dispersion components are almost constant. The stability of DNA complexes in water resulted from PCM calculations is markedly influenced by the free energy of hydration. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010
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