2D nightmare

Chi-kuang Wen ckwen at expert.cc.purdue.edu
Sun Jun 9 09:01:22 EST 1996


: >best wishes,

: >Chi-Kuang Wen

: Well, the original post did state that migration stopped due to too low 
: a current after 30 mins - this is a fast IEF run if already at 
: equilibrium. Secondly, the ampholines or immobilines in the system would 
: be unlikely to be focused (ie. at their pI) after such a short run 
: (assuming no prefocusing stage which is an unecessary step with this 
: system). Third, the run should be constant voltage since the current 
: will decrease during the run and if left constant at a high level could 
: result in too much heat. 
: ***************************
: david.logan at plants.ox.ac.uk

: David C. Logan
: Department of Plant Science
: University of Oxford
: South Parks Road
: Oxford
: OX1 3RB
CORRESTION:

I am sorry that I gave a wrong suggestion after it was posted, and I did not
know that the original post stated that the migration stoped after 30min.


You do need to run at constant voltage.

I have used two different powersupplies and have no problems in running the
IEF.  One is made by Hoeffer and the other is made by Biorad.  I amm sorry
that I do not remember the model number.(it was many years ago).  The most important thing is that
both powersupplies have very broad current ranges, and for IEF, the range needs
to be as low as 1mAMP when the molecules arrive thier pI points to support a
extremely high resistance.  For example, when the amperage is 1mAMP, and the
setting for voltage is 700volts, you may have a resistance as high as 700,000.

My guess , for your problem if it stopped migrating after 30min, is that your
powersupply has a narrow ampergae range, or the lower amperage limit is too
high, and when the resistance increases and results in "under-load" of the 
current, and it stops.  To check this, when your powersuppply stops, change
the voltage setting to 400volts, and turn the powersupply on again, if your
IEF keeps running for a while and then stops again, it may indicate that your
powersupply   can not support a low current output.

best wishes,


Chi-Kuang 



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