Already two water molecules change planar H-bonded structures of the adenine•••thymine base pair to the stacked ones:: a molecular dynamics simulations study

The dynamical structure of the adenine...thymine nucleic acid base pair exposed to a small number of water molecules (from 1 to 216) was determined using molecular dynamics simulations with Cornell et al. force field (W. D. Cornell, P. Cieplak, C. I. Bayly, I. R.Gould, K. M. Merz, D. M. Ferguson, D. C. Spellmeyer, T. Fox, J. E. Caldwell and P. Kollman, J. Am. Chem. Soc., 1995, 117, 5179). The gradual increase of hydration number results in a transition from planar base pair structures to nonplanar ones, and already for two water molecules the population of stacked structures is higher than that of planar structures.