junction potential calculation
Mark Farrant
m.farrant at ucl.ac.uk
Tue Jan 30 12:02:49 EST 1996
Alexander Reiprich wrote:
>
> Does anybody know how to calculate junction potentials between complex intra-
> and extracellular solutions in whole cell recordings ( containing
> TRIS-phosphate for example]? Is there free software available?
> How can I calculate the series resistance error in wcr?
>
The calculation for liquid junction potentials is perfectly
straightforward as long as you have access to values of ionic mobility.
The equation required is the Generalized Henderson Liquid Junction
equation and the calculation is easy to implement either in Mathcad or
Excel, for example. Essential reading (and sources of mobilility data)
are Barry & Lynch (1991; J.Memb.Biol. 121, 101-117), Ng & Barry (1995;
J.Neurosci.Meth. 56, 37-41), Neher (1995; Chapter 6 in Single-Channel
Recording, eds Sakmann and Neher, Plenum Press) and references therein.
I can't remember if either of the Barry papers give data on
Tris-phosphate. Things start getting difficult if you try to include
every constituent (eg ATP or EGTA, for which I can find no data).
There is a commercial package sold by Peter Barry called JPCalc.
As to series resistance errors in wcr, this is an entirely different
question. I suggest you read selected chapters in the aforementioned
Single-Channel Recording, in Microelectrode Techniques (The Plymouth
Workshop Handbook, Ed D. Ogden 2nd edition 1994) or the quite useful Axon
Guide from Axon Instruments.
Mark Farrant
Dept. Pharmacology
UCL
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