Proton conduction in linear hydrogen-bonded systems

It has been suggested that the hydrophilic side groups of proteins can form hydrogen-bonded conductors that transport protons across biomembranes. Based on previous studies of the proton dynamics in ice, a kinetic model for such proton conductors is developed. The steady-state proton current is evaluated as a function of the pH and voltage difference along the conductor. This electrochemical potential is found to determine the mechanism by which the protons are transported. Under acidic conditions the proton current is inversely proportional to the number of side groups composing the conductor and is determined by the rate of injecting a L-Bjerrum orientation fault into the hydrogen-bonded conductor. For small voltages (< 100 mV) an analytical expression for the proton flux is derived.