When working with larger nanopores, the system may need to be optimised further to allow for accurate and reproducible size and concentration measurements. Large nanopores have a large cross-sectional area and therefore a low electrical resistance. This needs to be managed in order to keep the measured current inside the operating range of the sensing electronics.
When railed, the current shows either a very straight line or a full-screen band that does not respond to an increase in nanopore stretch or voltage:
In the Classic Capture mode, the typical way to recover a railed system is to lower the voltage until a responsive “thin” current readout is seen – you can generally step the voltage up again when the system has recovered as long as you do not exceed the threshold current. If you're using the Assistant, click on "Reset Amplifier" to recover the baseline current.
Consider increasing electrical resistance by changing electrolyte strength and membrane stretch: