: Add-on heater for ABI 373A sequencer

Rick Wilson rick at GENEMAN.WUSTL.EDU
Mon Jan 13 09:18:38 EST 1992

Hi -

   For those of you who are using ABI's DNA sequencer, we have been
fooling around with a gel heater plate built by Time Logic, Inc. of
Moorpark, CA.  The idea of this heater was initially conceived by
Bruce Roe, and it is designed to minimize the thermal gradient which
occurs between the back (normally heated to 40 degrees) and the front
(normally not heated) of the rather thick gel plates.  As I believe
Bruce has correctly surmised, DNA bands run faster adjacent to the
back plate, and are thereby somewhat tilted.  This effect increases
over the length of the run.  Since the sequencer detects the bands at
a fixed location, the tilt of the bands makes them appear wider.  This
effect probably plays some role in the ever decreasing resolution
which we usually observe out around 350+ bp.

   The heater plate can be mounted in place of the laser stop which
swings up to hold the gel plates in place.  A temperature controller
sits on top of the ABI machine, and a thin cable is threaded through
the side of the sequencer.

   We have used the heater plate for several runs on our ABI sequencer;
it appears to significantly improve the resolution of the 350-550 bp
region.  Since we routinely use only 10 hour runs, we don't usually
collect more than 550 bp per sample.  However, with this heater plate,
the accuracy of the last 200 bp (especially with regard to insertion/
deletion errors) is greatly improved.  We will be writing up a more
detailed summation for BioTechniques within the next couple of weeks.

   More details about the gel heater plate can be obtained from
Jim Lindelien at Time Logic (76610.237 at compuserve.com).  I believe
they are asking around $4900 for the device.  This may seem a bit much,
but to us, the results have been well worth the cost.

Rick Wilson
C. elegans Genome Sequencing Consortium
St. Louis/Cambridge

Disclaimer:  I don't work for Time Logic, Inc., I only care about bp.

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