SELF-CONSISTENT REACTION FIELD COMPUTATION OF THE REACTIVE CHARACTERISTICS OF DNA BASES IN WATER

The effect of the solvent in the molecular properties of DNA bases has been explored by using a self-consistent reaction field (SCRF) method based on the AM1 (Austin Model 1) Hamiltonian and a modified version of the high level Miertus-Scrocco-Tomasi (MST) algorithm. MST/AM1 estimates of free energies of hydration compare qualitatively well with the available experimental data, as well as with the results obtained from molecular dynamic simulations. Furthermore, the changes in the dipole predicted by the MST/AM1 method are in good agreement with Monte Carlo/quantum mechanical data, as well as with AM1-SM2 (Soluation Model 2) estimates. AM1/MST calculations of Mulliken, and electrostatic charges, dipoles, molecular electrostatic potentials and molecular interaction potentials in both vacuum and solution allowed us to quantify the effect of the water on the reactive characteristics of the DNA bases. This effect is large and complex, and cannot be neglected in theoretical calculations where an accurate representation of the DNA bases is needed. The possibility of including the polarization effect of the water into force-field simulations of DNA structures is discussed. (C) 1993 John Wiley and Sons, Inc.