Sunghwan Kim - Hydration of the lowest triplet states of the DNA/RNA pyrimidines

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  Publication Details (including relevant citation   information):

  A.M. Rasmussen, M.C. Lind, S. Kim, and H.F. Schaefer;

  Journal of Chemical Theory and Computation,   20106, 930.



  The effects of hydration on the lowest triplet states of the   DNA/RNA pyrimidines have been studied by including one and two   water molecules explicitly. Three configurations for the singly   hydrated cytosine moiety were located, and six for the doubly   hydrated system. For thymine and uracil, four singly and eight   doubly hydrated structures were found. The singlet-triplet energy   gaps of all three pyrimidines (cytosine, thymine, and uracil)   fall in the low-energy range of ultraviolet radiation (UVA).   Energetic excited states can be a step leading to lesions in DNA,   such as a mismatched base pairs. Although the adiabatic and   vertical electronic excitation energies for all three pyrimidines   slightly increase upon inclusion of additional water molecules,   this effect upon the excitation energies is much smaller than   hydration effects upon the electron affinities and ionization   energies of the three nucleobases. Because both the ground state   and the triplet state are neutral, the hydration energy   difference between the two states is not significant (compared to   those between the neutral and charged species), making the   excitation energy less sensitive to hydration. Copyright © 2010   American Chemical Society.


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