Experimental Demonstration of Localized Excess Protons at a Water-Membrane Interface

The widespread Mitchellian proton motive force equation has recently been revised with the proton-electrostatics localization hypothesis, which, for the first time, successfully elucidates the 30-year longstanding energetic conundrum of ATP synthesis in alkalophilic bacteria. To demonstrate the fundamental behavior of localized protons in a pure water-membrane-water system in relation to the newly derived pmf equation, excess protons and excess hydroxyl anions were generated by utilizing an open-circuit water-electrolysis system and their distributions were tested using a proton-sensing aluminum membrane. The proton-sensing film placed at the membrane-water interface displayed dramatic localized proton activity while that placed into the bulk water phase showed no excess proton activity during the entire experiment. These observations clearly match with the prediction from the proton-electrostatics localization hypothesis that excess protons do not stay in water bulk phase; they localize at the water-membrane interface in a manner similar to the behavior of excess electrons in a conductor. This finding has significance not only in the science of bioenergetics but also in the fundamental understanding for the importance of water to life in serving as a proton conductor for energy transduction in living organisms