Structural Proton Diffusion along Lipid Bilayers

• Published in: Biophysical journal 2003-02, Vol.84 (2), p.1031-1037
• Main Authors: Serowy, Steffen, Saparov, Sapar M., Antonenko, Yuri N., Kozlovsky, Wladas, Hagen, Volker, Pohl, Peter
• Format: Article
• Language: English
• Subjects: Diffusion; Electrochemistry - methods; Experiments; Hydrogen-Ion Concentration; Light; Lipid Bilayers - chemistry; Lipid Bilayers - radiation effects; Lipids; Membranes; Membranes, Artificial; Molecular biology; Monte Carlo Method; Motion; Phosphatidylcholines - chemistry; Phosphatidylcholines - radiation effects; Proteins; Protons; Spectrometry, Fluorescence - methods; Surface Properties; Water - chemistry
• ISSN: 0006-3495; 1542-0086
• DOI: 10.1016/S0006-3495(03)74919-4

For H + transport between protein pumps, lateral diffusion along membrane surfaces represents the most efficient pathway. Along lipid bilayers, we measured a diffusion coefficient of 5.8 × 10 −5 cm 2 s −1. It is too large to be accounted for by vehicle diffusion, considering proton transport by acid carriers. Such a speed of migration is accomplished only by the Grotthuss mechanism involving the chemical exchange of hydrogen nuclei between hydrogen-bonded water molecules on the membrane surface, and the subsequent reorganization of the hydrogen-bonded network. Reconstitution of H +-binding sites on the membrane surface decreased the velocity of H + diffusion. In the absence of immobile buffers, structural (Grotthuss) diffusion occurred over a distance of 100 μm as shown by microelectrode aided measurements of the spatial proton distribution in the immediate membrane vicinity and spatially resolved fluorescence measurements of interfacial pH. The efficiency of the anomalously fast lateral diffusion decreased gradually with an increase in mobile buffer concentration suggesting that structural diffusion is physiologically important for distances of ∼10 nm.