gel problem resolved
jfstein at amnh.org
Sun Nov 1 18:47:33 EST 1998
Thanks to everyone for the helpful suggestions, especially those who
directed my attention to the possibility of charge build-up on the plates.
The problem is gone. Apparently I was leaving a NaOH residue on the plates
when washing and creating my own personal charge build-up.
Our gel preparation protocol includes rubbing a little NaOH on each plate,
to facilitate smooth pouring, then rinsing with lots of ultrapure water.
Since we all use NaOH in this manner regularly it didn't occur to me to
question it closely. Recently we replaced our expensive water purification
system with a less expensive one of greatly reduced capacity. Water
conservation efforts were leading me to rinse less. A little too much
NaOH, increasingly less H2O = gel breakdown and short sequences. Others in
the lab rinse slightly differently, and only very infrequently have seen
the kind of resolution loss I was getting.
When I changed to three ultrapure water rinses from a squeeze bottle, with
vigorous rubbing, instead of rinsing at the RO tap, the problem went away.
The difference is dramatic. My sequences are pretty again.
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