SEC
Can I do patch clamp experiments with a npi SEC amplifier?


Yes and no. You can do patch clamp experiments in the whole cell and perforated patch configuration, but due to the principle of switched operation, experiments with excised patches are not possible. Nevertheless, in whole cell configuration you record without any series resistance, which makes the SEC superior to conventional patch clamp amplifiers, especially if large currents in the nA range are recorded or large series resistance in perforated patch recordings occur.




SEC
Is the compensation of the capacity of the microelectrode in npi SEC systems important?


Yes, for accurate measurements in switched mode, it is ESSENTIAL that the capacity of the electrode is fully compensated. Wrong compensation of electrode capacity leads to errors in measurements done in switched mode of the amplifier.




SEC
How should I adjust the capacity compensation of the microelectrode in npi SEC systems?


The capacity of the microelectrode has to be compensated using two controls, the coarse control in the headstage and a the fine control at the front panel of the amplifier. In brief: first, tune the capacity with the control in the headstage by application of a holding current to the electrode in the bath and watching the signal at ELECTRODE POTENTIAL OUTPUT (rear panel). The signal should be as square as possible (at a low switching frequency). Second, apply square pulses of a few nA to a (model)cell. The POTENTIAL OUTPUT (front panel) should show the ohmic response of the cell membrane, without an artifact.

Download detailled instructions for tuning the capacity compensation in SEC systems.




TEC
I have a TEC-03X-CW and a valve manifold, and I use CellWorks for data acquisition and experiment control. How should I connect the hardware and configure CellWorks?


Please Download detailled instructions for connecting a TEC-03X-CW and configuring CellWorks accordingly.




TEC
I am using a TEC amplifier for oocytes and I am planning to record gating currents. What should I consider in general?


There are several points to consider. Generally, the clamp speed is determined by the maximum amount of current which the clamp system can force through a given electrode. Therefore, electrode resistance must be kept as low as possible. The clamp speed can be improved additionally by optimizing the position of the electrodes and using series resistance compensation. By placing the electrode in the center of the oocyte, the membrane capacity is charged homogeneously. The capacitive current transient is mono-exponential and the amplifier can be tuned without ringing around the slow tail of the transient. These procedures can lead to clamps as fast as 60 µs.
Please Download an article from Prof. Greeff in the ALA Action Potentials No.4 (2000) for some practical hints to achieve a fast clamp.




Extracellular measurement
How should I connect the electrode(s) to the headstage of my extracellular amplifier?


All headstages of npi amplifiers for extracellular measurements have differential inputs, i.e. the signal for the amplifier is always the difference between the positive (+) and negative(-) input of the headstage. Usually, the (+) input is linked to the BNC or SMC connector and the (-) input to a connector labeled REF. The potential measuring electrode should be connected to the (+) input and the reference electrode to the (-) input. If the (-) input is not used, it must be grounded.