Theoretical investigation of hydrogen atom transfer in the hydrated C–G base pair

Abstract

Hydrogen atom transfer and the related electronic rearrangement in the hydrated C–G base pair have been studied in order to understand the role of the hydrogen bonds between the bases and those with the water molecules in these processes. The modification of hydrogen transfer due to the first shell and bulk hydration has been analysed. The different structures, when the hydrogen atom moves in a H-bond or in another bond, have been studied. Two naïve schemes, where the water molecules are only indirectly or directly involved in the hydrogen atom transfer, have been considered. The results support the idea that the actual mechanisms are more complex than these schemes. Hydration modifies the potential energy curves of both tautomers and zwitterionic structures, but does not generate new stable structures (minimum PES) of these types. We find a new stable structure due to both a reorganization of the two down water molecules and other global changes of the system. This new system is generated from a zwitterionic structure. The charges, during hydrogen transfer, of the hydrogen donor and of the hydrogen acceptor part of the base pair and of the hydrogen atoms between the bases have been determined and their modifications, due to the first shell and bulk hydration, have been analysed. The qualitative and quantitative behavior has been studied.

Keywords:

• DNA
• base pair
• hydrated
• hydrogen transfer
• hydrogen bond