The proton pump at work: Part I. The basic concept of excess proton/defect proton translocation

Abstract

The Nagle-Morowitz proton pump, which is based on proton transport in water and ice, is shown to be inapplicable to weakly H-bonded proton transport systems. It is demonstrated that in weakly or non H-bonded systems protons can migrate either as excess protons H♭ using a high-lying proton conduction band or as defect protons H′ using intermediate energy levels. As H′ the protons act as positive charge carriers endowed with a very high mobility. As H′ they act as negative charge carriers. The H′ transport mechanism involves thermally activated proton tunneling. Owing to the very large mobility differences between H • and H′, > 10 6, very high potentials can be self-generated in any situation which creates a concentration gradient. Proton conductivity data on inorganic model compounds are presented. Applying these results to proton transport across biomembranes, transmembrane potentials U m , acidification Δ pH and transient phenomena can be explained as result of H • and H′ translocation.