increase in electrode resistance

r norman rsn_ at _comcast.net
Sun Mar 28 10:15:59 EST 2004


On Sun, 28 Mar 2004 15:00:25 +0100, usenet at out-of-phase.de (Christian
Wilms) wrote:

>r norman <rsn_ at _comcast.net> wrote:
>
>> om an increased probability of picking up floating
>> particles).   It is even more important to obtain a seal rapidly when
>> the pipette solution contains peptides or proteins, as they tend to
>> cover the pipette tip..."
>> 
>> The same glass using in sharp microelectrode will have the same
>> ability to pick up proteins, something in ample supply inside a cell.
>
>Hi Richard!
>
>I understood that statement from "Single Channel Recording" differently.
> I don't think that proteins and peptides will clog the pipette
>(consider the size of a patch pipette and the size of proteins). I think
>the problem here is more that a thin layer of proteins will lower the
>capability of the patch pipette to form a gigaseal, as it hinders the
>direct interaction of glass and membrane.
>
>Cheers, Chris

Of course you are right with patch clamp electrodes that have
relatively large tips.  The problem, though, is that proteins do tend
to stick to glass.  A coating of very small particles or individual
molecules will interfere with the seal, not clog the tip.  However, an
intracellular microelectrode may have a tip opening in the tens of
nanometer size range and sticking it into a cell can easily break of
"chunks" of material.of a size that can occlude the  tip.





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