Effects of model protein environments on the dynamics of proton wires

The multiconfigurational molecular dynamics with quantum transitions (MC-MDQT) method is utilized to study the impact of model protein environments on the dynamics of proton wires. The MC-MDQT method allows the real-time nonequilibrium quantum dynamical simulation of proton transport along water chains and provides a framework for analyzing the detailed dynamical mechanisms of these multiple proton transfer reactions. In this paper, the protein environment is modeled by applying structural restraints to the oxygen atoms of the chain, by applying external electric fields, and by including solvating water molecules hydrogen-bonded to the ends of the water chain. Our simulations illustrate that the protein environment could strongly impact the dynamics of proton wires through a combination of structural restraints, fluctuating electric fields, solvation, and hydrogen bonding. Our simulations also indicate that quantum effects such as hydrogen tunneling and nonadiabatic transitions play a significant role under certain nonequilibrium conditions.