35S contamination while cycle sequencing

Black, Michael BlackM at dfo-mpo.gc.ca
Wed Jul 30 15:29:56 EST 1997


Hello Everyone,
   I run between 3 or 4 sets of cycle-sequencing reactions per week in a
Cetus cycler (the model which pre-dated the 480 - just called DNA Thermo
Cycler I think), using 35S-ATP as label.  Given the warnings about
volatility of 35S which have been out for several years now, I set up
the
reactions in a hood but had thought that by the time the reactions were
sealed in their tubes with an oil overlay the risk of air-borne
contamination would be eliminated.  Recently our technician was doing a
wipe test while I had a reaction running, and he lifted the lid on the
cycler and wiped the underside - sure enough, the count was disturbingly
high (the previous week he had wiped the block itself and it was clean).
   My question is, does anyone have any further information about the
risk
of contamination from air-borne 35S while a cycler is running?  Should
we
stick the whole cycler in the hood (inconvenient since it can not stay
in
there all the time as we need the space)?  What about other machines?
We
also have a Stratagene RoboCycler, but as it takes 0.2mL tubes I don't
use
it for sequencing since I hate labeling those little tubes.  This
machine
will take 96-well plates (the cost of which have kept me from trying
those), which perhaps can be sealed better than the 0.5mL tubes?  Any
comments or suggestions will be much appreciated.

Dr. Michael B. Black
Fisheries and Oceans, Canada
Maurice Lamontagne Institute
blackm at dfo-mpo.gc.ca



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