A hydroxide ion carrier in planar phospholipid bilayer membranes: (C6F5)2Hg (dipentafluorophenylmercury).
Although a number of molecules are known to function as current-carrying proton carriers across lipid bilayer membranes, no such hydroxide ion carriers have been found to date. We report that (C6F5)2Hg, which can function as a chloride ion carrier, can also carry a hydroxide ion. In 100 mM Na2SO4 solutions, membranes treated with (C6F5)2Hg are almost ideally selective for H+/OH- between pH 6.0 and 9.5. Membrane conductance varies linearly with [OH-] over this pH range and with the square of the (C6F5)2Hg concentration. The presumed current-carrying species is the dimer [(C6F5)2Hg]2OH-, which, along with the neutral molecule (C6F5)2Hg, shuttles back and forth within the bilayer. In 0.2 M NaCl at pH 9.5, the OH- and Cl- conductances are approximately equal. Thus, the carrier displays an approximately 10(4)-fold preference for OH- over Cl-.
Blaustein
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Department of Physiology & Biophysics, Albert Einstein College of Medicine, Bronx, NY 10461.
Finkelstein
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D004553:Electric Conductivity; D006878:Hydroxides; D007476:Ionophores; D008051:Lipid Bilayers; D008564:Membrane Potentials; D009941:Organomercury Compounds; D010713:Phosphatidylcholines
D006878:Hydroxides; D007476:Ionophores; D008051:Lipid Bilayers; D009941:Organomercury Compounds; D010713:Phosphatidylcholines; C021016:1,2-diphytanoylphosphatidylcholine