Stark G, Ketterer B, Benz R, Läuger P
Biophys J. 1971 Dec;11(12):981-94. doi: 10.1016/S0006-3495(71)86272-0.
Electrical relaxation experiments have been performed with phosphatidylinositol bilayer membranes in the presence of the ion carrier valinomycin. After a sudden change of the voltage a relaxation of the membrane current with a time constant of about 20 musec is observed. Together with previous stationary conductance data, the relaxation amplitude and the relaxation time are used to evaluate the rate constants of valinomycin-mediated potassium transport across the lipid membrane. It is found that the rate constants of translocation of the free carrier S and the carrier-ion complex MS(+) are nearly equal (2.10(4) sec(-1)) and are of the same order as the dissociation rate constant of MS(+) in the membrane-solution interface (5.10(4) sec(-1)). The equilibrium constant of the heterogeneous association reaction M(+) (solution) + S (membrane) --> MS(+) (membrane) is found to be approximately 1 M(-1), about 10(6) times smaller than the association constant in ethanolic solution.
在离子载体缬氨霉素存在的情况下，对磷脂酰肌醇双层膜进行了电弛豫实验。在电压突然变化后，观察到膜电流以约20微秒的时间常数弛豫。结合先前的稳态电导数据，利用弛豫幅度和弛豫时间来评估缬氨霉素介导的钾离子跨脂质膜转运的速率常数。发现游离载体S和载体 - 离子复合物MS(+)的转运速率常数几乎相等（2×10⁴ 秒⁻¹），并且与MS(+)在膜 - 溶液界面的解离速率常数（5×10⁴ 秒⁻¹）处于同一数量级。非均相缔合反应M(+)（溶液）+ S（膜）→ MS(+)（膜）的平衡常数约为1 M⁻¹，比在乙醇溶液中的缔合常数小约10⁶ 倍。
