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Issue 30, 2008
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Solvation free energies of molecules. The most stable anionic tautomers of uracil

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Abstract

Anionic states of nucleic acid bases are suspected to play a role in the radiation damage processes of DNA. Our recent studies suggested that the excess electron attachment to the nucleic acid bases can stabilize some rare tautomers, i.e. imineenamine tautomers and other tautomers with a proton being transferred from nitrogen sites to carbon sites (with respect to the canonical tautomer). So far, these new anionic tautomers have been characterized by the gas-phase electronic structure calculations and photoelectron spectroscopy experiments. In the current contribution we explore the effect of water solvation on the stability of the new anionic tautomers of uracil. The accurate free energies of solvation are calculated in a two step approach. The major contribution was calculated using the classical free-energy perturbation adiabatic-charging approach, where it is assumed that the solvated molecule has the charge distribution given by the polarizable continuum model. In the second step the free energy of solvation is refined by taking into account the real, average solvent charge distribution. This is done using our accelerated QM/MM simulations, where the QM energy of the solute is calculated in the mean potential averaged over many MD steps. We found that in water solution three of the recently identified anionic tautomers are 6.5–3.6 kcal mol−1 more stable than the anion of the canonical tautomer.

Graphical abstract: Solvation free energies of molecules. The most stable anionic tautomers of uracil

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Publication details

The article was received on 12 Feb 2008, accepted on 18 Apr 2008 and first published on 11 Jun 2008


Article type: Paper
DOI: 10.1039/B802300J
Citation: Phys. Chem. Chem. Phys., 2008,10, 4442-4448
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    Solvation free energies of molecules. The most stable anionic tautomers of uracil

    M. Haranczyk, M. Gutowski and A. Warshel, Phys. Chem. Chem. Phys., 2008, 10, 4442
    DOI: 10.1039/B802300J

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