Hall J E
Biophys J. 1981 Mar;33(3):373-81. doi: 10.1016/S0006-3495(81)84901-6.
Alamethicin appears to allow voltage-dependent lipid exchange ("flip-flop") between leaflets of a planar bilayer. In membranes with one leaflet of phosphatidyl serine and one of phosphatidyl ethanolamine, the shape of the nonactin current-voltage curve accurately reports the difference in surface potential between the two sides of the membrane. The surface potential is itself a good measure of membrane asymmetry. Alamethicin added to the bathing solutions of an asymmetric membrane does not per se reduce the membrane asymmetry, but turning on the alamethicin conductance by application of a voltage pulse does. Immediately after application of a voltage pulse, large enough to turn on the alamethicin conductance, the asymmetry of the nonactin-K+ current voltage curve decreases, in some cases, nearly to zero. During the pulse, the alamethicin conductance activates if a decrease in surface potential favors turn-on of the alamethicin conductance or inactivates if a decrease in surface potential favors turn-off of the alamethicin conductance. After the pulse, the nonactin-K+ asymmetry returns to its original value if the alamethicin conductance is not turned on. The time-course of this return allows an estimate of the diffusion constant of lipid in the planar bilayer. The value obtained is 5.1 x 10(-8) cm2/s.
短杆菌肽似乎能使平面双层膜的两个小叶之间发生电压依赖性脂质交换（“翻转”）。在由一层磷脂酰丝氨酸小叶和一层磷脂酰乙醇胺小叶组成的膜中，缬氨霉素电流-电压曲线的形状准确反映了膜两侧表面电位的差异。表面电位本身就是膜不对称性的一个很好的衡量指标。添加到不对称膜浴液中的短杆菌肽本身并不会降低膜的不对称性，但通过施加电压脉冲开启短杆菌肽电导则会。在施加一个足以开启短杆菌肽电导的电压脉冲后，缬氨霉素-钾离子电流电压曲线的不对称性立即降低，在某些情况下，几乎降至零。在脉冲期间，如果表面电位降低有利于短杆菌肽电导的开启，则短杆菌肽电导激活；如果表面电位降低有利于短杆菌肽电导的关闭，则短杆菌肽电导失活。脉冲后，如果短杆菌肽电导未开启，缬氨霉素-钾离子不对称性会恢复到其原始值。这种恢复的时间进程可以估算平面双层膜中脂质的扩散常数。得到的值为5.1×10⁻⁸平方厘米/秒。
