Two possible mechanisms of water-assisted proton transfer in the stack of adenine-thymine: Displacement polarization and oriented polarization

Proton transfer in DNA has attracted much attention because of its close relationship with charge transfer and DNA base damage. In the present study, the relationship between proton transfer and water polarization at a certain temperature in the radical cation stack of adenine-thymine is investigated by QM/MM molecular dynamics simulations. By analyzing the polarization of aqueous solution, it is found that at low temperature water molecules promote proton transfer by means of displacement polarization and oriented polarization, while at high temperature, water molecules promote proton transfer only by displacement polarization.