Computational Investigation of Deoxyribose and Phosphate Substitutions Effects on the Hydrogen Bond Strength of Adenine–Thymine Base Pair in the Gas Phase and Water Solution.

The effects of deoxyribose and phosphate substitutions on the hydrogen bond strength of adenine-thymine (AT) base pair in the gas phase and water solution were computationally investigated. According to the gas phase complexation energies, the parent molecule is the least stable complex among all of the structures. Our results clearly show that the attachment of deoxyribose substitution significantly increased the stability of dAT and ATd derivatives. While the phosphate addition has an opposite effect. In addition, the binding of the deoxyribose substitution from thymine side further increased the stability of ATd compared to adenine side in the dAT structures. Surprisingly, in the water solution, the binding of the phosphate group increased the additive effect of the deoxyribose substitution on the hydrogen bond strength. It is interesting to note that these substitutions in both phases further effect on the C–H···O hydrogen bond than the other units. Also the highest amount of its energy in the gas phase and water solution belongs to the dAT and ATdp, respectively and these structures have the highest values of total energy of hydrogen bonds. Finally, we introduced some good descriptors for estimation of the individual and the total hydrogen bond energies in these biomolecules. [ABSTRACT FROM AUTHOR]