FROZEN acrylamide sol'n!

Tom Thatcher ttha at uhura.cc.rochester.edu
Wed Apr 17 12:37:42 EST 1996


In <4l2t3c$17l at ccshst05.uoguelph.ca> tjackson at uoguelph.ca (Timothy R Jackson) writes:

>we are making our own 8% denaturing acrylamide gel solution for 
>electrophoresis, sequencing, etc. and were told by a few people that it's 
>best to store the stuff in a 4 degree fridge.  well our damn acrylamide 
>solution freezes!!  some days it doesn't some batches don't - it's a real 
>pain!  however, since we started doing this, when the acrylamide isn't 
>frozen, we're getting the nicest gels we've ever run.  what's the scoop 
>here?  why does it freeze and what can we do to prevent it?  any help 
>here would be greatly appreciated.  if it's any help, we're making 7.83M 
>urea gels and mixing the solution in a vacuum (i.e. degassing).
>thanx in advance!

I don't think the solution is freezing; I think the urea is precipitating 
out of solution because it is not soluble in that high a concentration
at that cold a temp.

One speculation about why some batches don't precipitate and give very nice
gels is the following: crystals form around a nucleus, something to get
them started, like dust, or tiny undissolved crystals.  If the solution is
extremely clean, you can cool it below the crystalization point and not
get crystals (supercooled).  So maybe those solutions that don't "freeze"
are the cleanest, most well-mixed and degassed batches.  If you take a 
supercooled batch and shake it vigorously, the air bubbles you introduce 
can serve as nucleating sites for crystals and the whole solution can "freeze"
in seconds.

BTW, I do not refrigerate my sequencing mix, and I rarely get poor gels.
-- 
Tom Thatcher                          | You can give a PC to a Homo habilis,
University of Rochester Cancer Center | and he'll use it, but he'll use it
ttha at uhura.cc.rochester.edu           | to crack nuts.



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