Bio-Rad sequencer

Michael Joiner joiner at
Wed Jun 1 17:05:22 EST 1994

In article <rmlemons-010694082850 at>, rmlemons at um
(Rosemary Lemons) wrote:

> We're setting up our new Bio-Rad Sequencing apparatus and are having
> problems
> getting the proper current through it (low Watts, less than 10 at 1600 V).
> We've
> checked the leads, power supply, and buffers and there seems to be no
> problems there.  Anyone else out there have this machine and have any
> ideas?

We run both the small and the large BioRad kits with 0.4mm spacers. The
small one likes to run at about 2300V, 22mA and 50Watts (double the current
and watts for the large one). Generally, we set our power supply to limit
on 50 or 55 watts, and this then brings the temperature to about 50-55
degrees C after 45min to 1 hour. If you are using thinner spacers, your
conditions may not be so different from ours. For example at 1600V, 0.3mm
spacers should give about 11mA and 0.2mm spacers would give about 8mA.
We use 1X TBE running buffer. If its not the spacers, I assume you made up
your gel and running buffer to the same final TBE concentration? Also, the
buffer level in the tank must be above the glass plate. Is it possible your
power supply can't handle the task? You could check this by graphing
current against voltage, this should be linear otherwise you may need to
buy a more meaty unit. Try borrowing another power supply to test this.
Mike Joiner
Radiation Oncology
University of Pennsylvania                   joiner at

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