Nonlinear models of collective proton transport in hydrogen-bonded systems

Abstract

Proton transport plays a fundamental role in cellular bioenergetics because pH gradients across membranes are the driving mechanism of many biomolecular reactions. In particular, proton transport is coupled to synthesis and hydrolysis of ATP which is the essential energy storage mechanism in biology. In spite of its importance, the mechanism of proton transport is far from being properly understood and this problem extends beyond biology. Even in physical systems which appear much simpler than biological molecules, such as ice, the mechanism of proton transport is not elucidated completely. The main question is the high proton mobility which is observed experimentally. When the proton-hydroxide permeability of biological membranes has been measured, it has been found to be orders of magnitude greater than expected from sodium-potassium permeabilities [1], showing that protons play a special role. A similar observation had been made previously for ionic mobility in water solutions [2].