Keto-enol tautomer of uracil and thymine

Department of Chemistry, Tohoku University, Miyagi, Japan
The Journal of Physical Chemistry (Impact Factor: 2.78). 04/1988; 92(7):1760-1765. DOI: 10.1021/j100318a013
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The relative stability orders in the tautomers of uracil and its derivatives (5-fluorouracil, 5-chlorouracil, 5-aminouracil, 5-hydroxyuracil, 5-methyluracil, 6-methyluracil, 5-hydroxy-6-methyluracil and 5-amino-6-methyluracil) were established using composite (G3MP2B3) and DFT (TPSS) methods. The stability orders were determined both in the gas phase and water solutions, taking into account specific and non-specific hydration. The primary solvation shell of uracils was modeled as a complex of a tautomer with 5 water molecules. An analysis of the factors which determine the stability of the enol forms of uracils was performed. The most important factor was found to be changes in the intramolecular conjugation at tautomerization. As was shown by the NBO analysis, the stabilization energy due to the nN → π∗ (or σ∗) interaction in the diketo tautomer is lost in the enol forms, but is partially compensated by an increase in the conjugation length. The effect of the substituent in the fifth position of the pyrimidine ring on the energy of tautomers is less prominent. It was shown that the hydration energy considerably differs for tautomers, and leads to substantial redistribution in the stability series of uracil tautomers. Both specific and non-specific solvation are of vital importance for stabilization of tautomers.
    Computational and Theoretical Chemistry 11/2013; 1023:38–45. DOI:10.1016/j.comptc.2013.09.005 · 1.37 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Nucleobases in DNA and RNA are important building blocks of the genetic codes and are critical in transferring genetic information. In general, nucleobases have many tautomers; but in DNA and RNA molecules they are mainly presented in the most stable forms. Uncommon tautomers can cause mispairing of base pairs to form irregular structures of DNA and RNA that lead to spontaneous mutations during replication. Thus, systematic studies of nucleobase tautomers are very important in understanding the structures and the characteristics of DNA and RNA. This review summarizes the experimental and theoretical studies in the literature and our density functional calculations on all the nucleobase tautomers. The relative energies of nucleobase tautomers and the structures of their lowest-energy tautomers fromour calculations are in good agreement with the experimental values in the literature. In addition, we also summarize the information of electron affinities, ionization potentials, and proton affinities of nucleobases reported in the literature.
    ACTA PHYSICO-CHIMICA SINICA 10/2013; 29(10). DOI:10.3866/PKU.WHXB201308011 · 0.89 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Stability orderings of 150 stable complexes formed by metal ions (Na+, K+, Ca2+, Mg2+, and Zn2+) and 13 stable thymine tautomers in both solvent and gas phases are obtained, and the optimal binding site for a metal ion in a specific thymine tautomer is identified. Results indicate that the complex with the canonical thymine tautomer (T1) is more stable than those with the rare ones, and the monodentate complex M–T1o4(o2) are their ground‐state form in the solvent phase. The ground‐state thymine complexes bound by Ca2+, Mg2+, or Zn2+ become bidentate M–T3o4lo2,n3, which is derived from a rare thymine tautomer T3o4l, whereas those bound by Na+ and K+ are still monodentate complexes M–T1o4(o2), however, in the gas phase. The differences in stability are discussed in detail from the binding strength of metal ions, relative energy of the corresponding thymine tautomers, and solution effect. Copyright © 2011 John Wiley & Sons, Ltd.
    Journal of Physical Organic Chemistry 02/2012; 25(2). DOI:10.1002/poc.1881 · 1.23 Impact Factor