I need to measure fine changes in cell capacitance. Does anybody know how to set pClamp 10 and axopatch 200b to have the lock-in amplifier function? I know it is possible on Heka amplifiers through the Pulse function.
Will not work with lockin amplifier with pClamp 10. Problem is that pCalmp 10 will not run lockin function (If anyone knows how to I'd like to know as well). Axon (Molecular devices) suggest using the sealtest function in pClamp 10 and this works OK. When you say 'fine' what range are you thinking of sub fF? and at what sample rate?
Hi Vincenzo,
Euan is right, you don't have lock-in function with axopatch 200B. Indeed you can use the seal test function to track the cell capacitance but 1) it is not exactly for what it is made for..., and 2) you are limited to follow the cell capacitance at constant voltage.
In other words, if you really want to do extensive recordings of cell capacitance you will have better time using the HEKA amplifier.
Norbert
Thanks to both of you for your answer! I was afraid that I cannot use the Axopatch for this...
I don't want to be the dissenting voice, and I suspect I am somewhat ignorant on the subject relative to Norbet and Euan, but are we sure you can't use a 200B, so long as you have some other equipment? That is to say, if you have a sine wave generator with variable phase, and a digital phase detector, couldn't you achieve something? a la, the attached.
Obviously it wouldn't be as easy as using PULSE, but if you didn't have access to a HEKA. Just a thought.
Thanks William, I actually found an article from Fernandez from 1988 where he explains the technique. We actually found the way to generate the waveform right now and we're working on the phase detection, which is quite theoretical.
Thanks!
Hi Will no dissent there! You would need to tool up though! If you manage to figure out how to do this with clampex Id love to know. We have been measuring slow Cap changes with a 200B and using the sealtest. which is OK in the sub picoF range. You can use the sequencing keys to swap between V steps and sealtest. The sealtest cap output needs to be continuously recorded in the graph display. Its all a bit clunky!
You can used a indert protocol, you can follow the membrane noise and calculate for the power spectrum thetotal cells capacitance. I used thats in big cells in a two electrode system and is good inderect mesured of the changes in the membrane permability.
The hek intrument can made same similir observaton and you can used minianalisys noise analisis of the you membrane recording
I hope help you these "inderect" idea
It is possible to do this without lock-in. See this paper, but I am afraid that I cannot offer any guidance on the contents or implementation. I have EPC10s in my lab so never needed to go into its detail.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1301564/
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