Voltage Offsets in Patch-Clamp Experiments
Voltage Offsets in Patch-Clamp Experiments
复制标题
膜片钳实验中的电压偏移
DOI：
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发表时间：
1995
期刊：
影响因子：
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通讯作者：
E. Neher
中科院分区：
文献类型：
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作者：
E. Neher
在膜片钳实验中必须考虑不同来源的偏置电压。在典型的实验中，有些偏移量是恒定的，如放大器输入偏移量；有些是可变的，如液体结电势，取决于离子条件。有些出现在外部电路中(即，在膜片移液管、实验室或氯化银电极上)，有些出现在膜片钳放大器中。放大器偏置的典型幅度为±30 mV，电极偏置的最大幅度为100 mV(取决于Cl−浓度)，不同溶液界面的液体结电位最高为±15 mV。在吸管密封到电池之前，通过执行参考测量来补偿放大器和电极偏移是标准做法。这是通过调整可变偏移量(Vo)来实现的，该可变偏移量(Vo)在放大器中被加到命令电压(Vc)上，使得在Vc=0时有零电流流动。如果上述偏移量在实验期间没有改变，则该协议是正确的。然而，如果吸管溶液的组成与浴液的组成不同(通常是全电池测量的情况)，则在参考测量过程中，吸管尖端将出现液结电势。在测试测量过程中，当液结被研究中的膜取代时，将不再是这种情况。
Offset voltages of various origins have to be considered in patch-clamp experiments. Some of the offsets are constant during a typical experiment, such as amplifier input offsets; some are variable, such as liquid junction potentials, depending on ionic conditions. Some arise in the external circuit (i.e., in the patch pipette, in the experimental chamber, or at the silver chloride electrodes), and some arise in the patch-clamp amplifier. Typical magnitudes are ±30 mV for amplifier offsets, up to 100 mV (depending on Cl− concentrations) for electrode offsets, and up to ±15 mV for liquid junction potentials at interfaces between different solutions. It is standard practice to compensate amplifier and electrode offsets by performing a reference measurement before the pipette is sealed to a cell. This is done by adjusting a variable offset (V o), which, in the amplifier, is added to the command voltage (V c), such that there is zero current flow at V c = 0. This protocol is correct, provided that none of the offsets mentioned above changes during the experiment. If, however, the pipette solution is different in its composition from the bath solution (as is usually the case for whole-cell measurements), a liquid junction potential will be present at the pipette tip during the reference measurement. This will no longer be the case during the test measurement, when the liquid junction is replaced by the membrane under study.