Application of a universal solvation model to nucleic acid bases: Comparison of semiempirical molecular orbital theory, ab initio Hartree-Fock theory, and density functional theory

The free energies of solvation of six nucleic acid bases (adenine, cytosine , hypoxanthine, guanine, thymine, and uracil) in water and chloroform are c alculated using CM2 class IV charges and SM5.42R atomic surface tensions. U sing any of three approximations to the electronic wave function (AM1, Hart ree-Fock, or DFT), we obtain good agreement with experiment for five cases where the experimental results are known for the partition coefficients bet ween the two solvents. Decomposition of the solvation effects into bulk ele ctrostatic contributions and first-solvation-shell effects shows that the p artitioning is dominated by the former, and this illustrates the importance of using accurate partial atomic charges for modeling these molecules in a queous solution. (C) 1999 Elsevier Science B.V. All rights reserved.