Differential movement of ions in artificial phospholipid vesicles

[摘要]

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.

[学科分类] 生物化学/生物物理

[关键词] Ion movement;Liposome;Aqueous channel;Pyranine;Vesicular pH;DISC(3)-5;3';3'-diisopropylthiodicarbocyanine;TCS;3;3';4';5-tetrachlorosalicylanilide