Cooperative interactions of hydrogen bonds in proton-transfer processes involving water molecules. Simulation of biochemical systems

Abstract

Quantum-chemical calculations of molecular complexes simulating the proton channel of influenza A virus and the proton-transfer system of the active site of carboanhydrase enzyme were performed. These complexes comprise a proton-donor and a proton-acceptor groups bridged by a chain of water molecules. Calculations of the methylimidazole (H+)-H2O-CH3COO− complex as a model of influenza M2 virus revealed free translation motion of the water molecule between the donor and acceptor, as well as concerted proton transfer in both H bonds. The barrier for proton transfer is independent of the position of the bridging water molecule and varies linearly with the difference in the electrostatic potentials between the donor and acceptor. With elongation of the H-bond bridge between the donor and acceptor groups, the H-bond lengths and proton shifts in the chain links vary periodically. This process can be defined as an H-bond deformation wave (proton wave). It was shown that motion of one proton along the H bond is associated with vibrational motion of protons in other links, which results in wave propagation along the chain. The calculation results allowed the rate of the proton wave and the time of proton transfer from the donor to acceptor to be estimated.