Differential movement of ions in artificial phospholipid vesicles.
Pyranine was incorporated into sonicated unilamellar vesicles of soybean phosphatidylcholine to monitor changes in the internal pH of the vesicles. Dilution of soybean phosphatidylcholine vesicles loaded with 0.3 M KCl, KNO3 or K2SO4 into salt-free buffer resulted in rapid exchange of K+ and protons. A pseudoequilibrium distribution of ions was achieved, since addition of valinomycin, uncoupler or nigericin now caused a rapid alkalinization of the vesicle interior. Dilution into buffer containing NaCl gave a further exchange of Na+ and protons following the initial K+/proton exchange. Na+ permeation was slower than that of K+. A stable membrane potential was not generated by the ion movements. It is proposed that aqueous channels are formed through the phospholipid bilayers and that K+ and Na+ permeate through these channels as the hydrated ions.
Department of Biochemistry, University of British Columbia, Vancouver, Canada.
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Sedgwick
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Bragg
D001190:Arylsulfonates; D002412:Cations; D004396:Coloring Agents; D006863:Hydrogen-Ion Concentration; D007473:Ion Channels / Q000378:metabolism; D008081:Liposomes / Q000378:metabolism*; D008564:Membrane Potentials; D009550:Nigericin / Q000494:pharmacology; D009566:Nitrates / Q000378:metabolism; D010316:Particle Size; D010713:Phosphatidylcholines / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism*; D011189:Potassium Chloride / Q000378:metabolism; D017680:Potassium Compounds; D011522:Protons; D012458:Salicylanilides / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism*; D013025:Glycine max / Q000032:analysis; D013431:Sulfates / Q000378:metabolism; D014634:Valinomycin / Q000494:pharmacology
D001190:Arylsulfonates; D002412:Cations; D004396:Coloring Agents; D007473:Ion Channels; D008081:Liposomes; D009566:Nitrates; D010713:Phosphatidylcholines; D017680:Potassium Compounds; D011522:Protons; D012458:Salicylanilides; D013431:Sulfates; C031512:potassium sulfate; D014634:Valinomycin; D011189:Potassium Chloride; D012964:Sodium; C003390:3,3',4',5-tetrachlorosalicylanilide; C005047:pyranine; D009550:Nigericin; C023844:potassium nitrate; D011188:Potassium