Chen Wei, Huang Feiran
Cellular and Molecular Biophysics, Department of Physics, University of South Florida, Tampa, FL, USA.
J Bioenerg Biomembr. 2008 Aug;40(4):337-45. doi: 10.1007/s10863-008-9152-z. Epub 2008 Aug 5.
The behavior of Na/K pump currents when exposed to an oscillating electric field is studied by computer simulation. The pump current from a single pump molecule was sketched based on previous experimental results. The oscillating electric field is designed as a symmetric, dichotomous waveform varying the membrane potential from -30 to -150 mV around the membrane resting potential of -90 mV. Based on experimental results from skeletal muscle fibers, the energy needed to overcome the electrochemical potentials for the Na and K-transports are calculated in response to the field's two half-cycles. We found that a specially designed oscillating electric field can eventually synchronize the pump molecules so that all the individual pumps run at the same pumping rate and phase as the field oscillation. They extrude Na ions during the positive half-cycle and pump in K ions during the negative half-cycle. The field can force the two ion-transports into the corresponding half-cycles, respectively, but cannot determine their detailed positions. In other words, the oscillating electric field can synchronize pumps in terms of their pumping loops but not at a specific step in the loop. These results are consistent with our experimental results in measurement of the pump currents.
通过计算机模拟研究了钠钾泵电流在振荡电场作用下的行为。基于先前的实验结果，绘制了单个泵分子的泵电流。振荡电场设计为对称的二分波形，在 -90 mV 的膜静息电位附近将膜电位从 -30 mV 变化到 -150 mV。根据骨骼肌纤维的实验结果，计算了响应电场两个半周期克服钠和钾运输的电化学势所需的能量。我们发现，专门设计的振荡电场最终可以使泵分子同步，从而使所有单个泵以与场振荡相同的泵送速率和相位运行。它们在正半周期挤出钠离子，在负半周期泵入钾离子。该场可以分别迫使两种离子运输进入相应的半周期，但不能确定它们的详细位置。换句话说，振荡电场可以使泵在其泵送循环方面同步，但不能在循环中的特定步骤同步。这些结果与我们测量泵电流的实验结果一致。
