Benz R, Nonner W
J Membr Biol. 1981 Apr 15;59(2):127-34. doi: 10.1007/BF01875710.
Asymmetrical displacement currents are measured in the absence and in the presence of the lipophilic anion dipicrylamine (DPA) in the extracellular solution of nerve fibers of the frog Rana esculenta. DPA (30 nM--3 microM) enhances the current by a component that has the properties expected for a translocation current of DPA ion across the lipid membrane. Analysis in terms of a single-barrier model yields the translocation rate constant (k), the total surface density of DPA absorbed to the membrane (Nt), and the equidistribution voltage (psi). The value of kappa of about 10(4) s-1 is similar to that for a solvent-free artificial bilayer formed by the Montal-Mueller method. The surface density Nt varies with the DPA concentration as it does in the artificial bilayer, but is about tenfold smaller at all concentrations. The DPA ions sense an intrinsic electric field that is offset by a transmembrane voltage between 0 and 30 mV (inside positive). The part of the axolemma probed by the DPA ion appears as a thin ( less than 2.5 nm), fluid bilayer of lipids. DPA ions seem, however, to be excluded from the major part of the axolemma as if this area is occupied by integral proteins or negative charges.
在食用蛙（Rana esculenta）神经纤维的细胞外溶液中，于不存在和亲脂性阴离子二苦味胺（DPA）的情况下测量不对称位移电流。DPA（30 nM - 3 μM）通过一个具有DPA离子跨脂质膜转运电流预期特性的成分增强电流。根据单屏障模型进行分析得出转运速率常数（k）、吸附到膜上的DPA的总表面密度（Nt）以及等分布电压（ψ）。约10⁴ s⁻¹的κ值与通过蒙塔尔 - 米勒方法形成的无溶剂人工双层膜的κ值相似。表面密度Nt随DPA浓度变化，与人工双层膜中的情况相同，但在所有浓度下都约小十倍。DPA离子感知到一个由0至30 mV（内侧为正）的跨膜电压抵消的固有电场。DPA离子探测的轴膜部分表现为脂质的薄（小于2.5 nm）流体双层膜。然而，DPA离子似乎被排除在轴膜的主要部分之外，就好像该区域被整合蛋白或负电荷占据一样。
