Home made gems don't "invert"

Jim Owens jow at helix.nih.gov
Thu Jan 13 11:07:21 EST 1994

In article <758402053snz at genesys.demon.co.uk> Duncan Clark,
Duncan at genesys.demon.co.uk writes:
>I tried some while ago to find wax pellets that would work and drew a
>on commercially sold pellets from BDH (Merck). A lot have DMSO or other 
>reagents which screw up the PCR totally. I did howver find that ordinary
>(as blocks) from Fluka worked very well. My problem was making pellets
of even
>size etc. The other problem is the meniscus. Unless you add some
detergent ie
>Tween or Brij to the wax you will get a meniscus such that the centre of
>PCR reaction is not covered! I haven't been back to this. Finally as
>watch out for the inevitable patent applications!

I had the same problem getting the wax pellets uniform.  For what it's
worth someone down the hall has made beads with parafin wax (from Fisher
Scientific I believe).  He said for best results make the molten wax 10%
mineral oil.  I haven't tried this yet. Duncan Clark's problem may be
beads that are too small, but it might be that the 10% mineral oil would
take care of the problem without increasing the volume.  

I was so frustrated in making uniform beads with a wax recommended in a
BioTechniques article that I have reverted to using mineral oil for hot
start PCR.  My problem was in maintaining the wax in the molten state
until the beads were pipetted.  Also I was worrying about RNase
contamination since I had used Ampliwax for RT-PCR with no problem.  I
would have continued to use Ampliwax except for budgetary reasons.  Now
I've relearned using mineral oil and have no great desire for wax beads
any more.

Good luck,

Jim Owens

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