School of Physics & Astronomy, University of Leeds, Leeds, LS2 9JT, UK.
Chemphyschem. 2010 Jul 12;11(10):2191-8. doi: 10.1002/cphc.200900917.
Tethered bilayer lipid membranes (tBLM) are formed on 1) pure tether lipid triethyleneoxythiol cholesterol (EO(3)C) or on 2) mixed self-assembled monolayers (SAMs) of EO(3)C and 6-mercaptohexanol (6MH). While EO(3)C is required to form a tBLM with high resistivity, 6MH dilutes the cholesterol content in the lower leaflet of the bilayer forming ionic reservoirs required for submembrane hydration. Here we show that these ionic reservoirs are required for ion transport through gramicidin or valinomycin, most likely due to the thermodynamic requirements of ions to be solvated once transported through the membrane. Unexpectedly, electrochemical impedance spectroscopy (EIS) shows an increase of capacitance upon addition of gramicidin, while addition of valinomycin decreases the membrane resistance in the presence of K(+) ions. We hypothesise that this is due to previously reported phase separation of EO(3)C and 6MH on the surface. This results in ionic reservoirs on the nanometre scale, which are not fully accounted for by the equivalent circuits used to describe the system.
束缚双层脂质膜（tBLM）形成于 1）纯束缚脂质三乙氧基硫醇胆固醇（EO(3)C）或 2）EO(3)C 和 6-巯基己醇（6MH）的混合自组装单层（SAM）上。虽然 EO(3)C 是形成高电阻 tBLM 所必需的，但 6MH 会稀释双层下叶胆固醇的含量，形成亚膜水合所需的离子储库。在这里，我们表明这些离子储库对于通过革兰氏菌素或缬氨霉素的离子传输是必需的，这很可能是由于离子在通过膜传输后被溶剂化的热力学要求。出乎意料的是，电化学阻抗谱（EIS）显示在加入革兰氏菌素时电容增加，而在存在 K(+)离子时，加入缬氨霉素会降低膜电阻。我们假设这是由于先前报道的 EO(3)C 和 6MH 在表面上的相分离。这导致了纳米尺度的离子储库，而这无法完全用用于描述该系统的等效电路来解释。
