在极低渗透离子浓度下短杆菌肽介导的电流。
Gramicidin-mediated currents at very low permeant ion concentrations.
作者信息
Hainsworth A H, Hladky S B
出版信息
Biophys J. 1987 Jul;52(1):109-13. doi: 10.1016/S0006-3495(87)83194-6.
Abstract
Current-voltage relations have been measured for the fluxes of caesium ions through pores formed by gramicidin in lipid bilayer membranes. The ionic currents have been separated from capacitative currents using a bridge circuit with an integrator as null-detector. The conductances during brief voltage pulses were small enough to avoid the effects of diffusion polarization and the ionic strength was raised using choline chloride or magnesium sulfate to reduce the effects of double-layer polarization. Under these conditions the current-voltage relations have the same shape at 0.1 and 1 mM, but different shapes for higher concentrations. These data demonstrate that the fluxes do not obey independence for concentrations above 10 mM, but they cannot be used in isolation to support a particular value of the binding constant. The shape observed at low concentrations suggests that entry of ions into the pore remains weakly potential dependent even at 300 mV.
摘要
已测量了铯离子通过脂双层膜中短杆菌肽形成的孔的通量的电流-电压关系。使用带有积分器作为零检测器的桥路将离子电流与电容电流分离。在短暂电压脉冲期间的电导足够小，以避免扩散极化的影响，并且使用氯化胆碱或硫酸镁提高离子强度以减少双层极化的影响。在这些条件下，电流-电压关系在0.1和1 mM时具有相同的形状，但在更高浓度时形状不同。这些数据表明，对于浓度高于10 mM的情况，通量不遵循独立性，但不能单独使用这些数据来支持结合常数的特定值。在低浓度下观察到的形状表明，即使在300 mV时，离子进入孔的过程仍然与电位弱相关。
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