Department of Physiology and Biophysics, State University of New York, Buffalo, New York, USA.
Biophys J. 2011 Dec 7;101(11):2645-51. doi: 10.1016/j.bpj.2011.11.002.
The ability to form gigaseals is essential for patch-clamp electrophysiology; however, ion channels located in the seal can produce measureable currents. To explore the expected properties of channels in the seal (i.e., rim channels), we created a mathematical model. The seal was a two-dimensional cable filled with saline and bounded on one side by membrane (with resistance and capacitance) and on the other side by glass (nonconductive and noncapacitive). We included ion depletion/accumulation around the channels. The channels were ohmic with a conductance that increased with the concentration of permeant ions. The aqueous seal thickness was set nominally to 1 nm. Imaging with fluorescent dyes in the pipette showed that the hydrophilic dye Alexa 488 is impermeant, but lipophilic FM1-43 labels the seal. The model showed that to obtain high-resistance seals, the conductivity of the seal media has to be <10% that of the bath. Stimulus voltages decreased with distance down the seal. In agreement with results in the literature, channels in the seal can produce currents similar to those in the pipette-spanning dome. The transition times of currents are slower due to membrane capacitance. If channel densities are uniform, patch currents are dominated by channels in the dome.
形成千兆欧姆密封的能力对于膜片钳电生理学至关重要；然而，位于密封处的离子通道会产生可测量的电流。为了探索密封处（即边缘通道）的通道的预期特性，我们创建了一个数学模型。密封是一个二维的电缆，内部充满生理盐水，一侧由膜（具有电阻和电容）构成，另一侧由玻璃（不导电且无电容）构成。我们还包括了通道周围的离子耗竭/积累。通道呈欧姆特性，其电导随可渗透离子的浓度增加而增加。水相密封厚度设定为名义上的 1nm。用玻璃微电极内的荧光染料进行成像显示，亲水性染料 Alexa 488 是不可渗透的，但疏水性 FM1-43 标记了密封。该模型表明，为了获得高电阻密封，密封介质的电导率必须小于浴液的 10%。刺激电压随密封长度的增加而降低。与文献中的结果一致，密封处的通道可以产生类似于贯穿玻璃微电极尖端的穹顶内的电流。由于膜电容，电流的过渡时间较慢。如果通道密度均匀，那么膜片钳电流主要由穹顶内的通道产生。
