Voltage clamp system with a very low noise probe for electrophysiological measurements

A cell derives its electrical properties mostly from the electrical properties of its membrane. A membrane, in turn, acquires its properties from its lipids and proteins, such as ion channels and transporters. An electrical potential difference exists between the interior and exterior of cells. A charged object, such an ion, gain or loses energy as it moves between places of different electrical potential, just as an object with mass moves up or down between points of different gravitational potential. The potential difference across a cell relates the potential of the cellpsilas interior to that of the external solution. Potential differences between two points that are separated by an insulator are larger than the difference between these points separated by a conductor. Thus, the lipid membrane, which is a good insulator, has an electrical difference across it. This potential difference, called transmembrane potential, amounts to less than 0.1 V, typically 30 to 90 mV in most animal cells, but can be as much as 150 - 200 mV in plant cells. On the other hand, the salt-rich solutions of the cytoplasm and the blood are fairly good conductors, and there are usually very small differences at steady state between any two points within a cellpsilas cytoplasm or within the extracellular solution. Electrophysiological equipment enables researches to measure potential differences in biological systems. Electrophysiological equipment can also measure current, which is the flow of electrical charge passing a point per unit of time. Usually, currents measured by electrophysiological equipment range from picoamperes to microamperes. Electrophysiological measurements should satisfy two requirements: they should accurately measure the parameter of interest, and they should produce no perturbation of the parameter. In this work, we present designs of the probe (input stage) and amplifiers that together constitute a system of setting very low noise voltage clamp system.