Klaus.Matthaei at anu.edu.au Klaus.Matthaei at anu.edu.au
Mon Jul 12 19:45:31 EST 1993

G'Day Netters

Some months ago there was a question about S35 PCR and the possibility that
the label may be going through the tubes and contaminating the block.  We
have recently obtained a 96 well cycle sequencer (apologies to Cetus) that
uses thin-wall tubes or thin-wall 96 well plates.  The system does not use
oil but sealed tubes.  Although P32 PCR goes without a hitch (i.e. clean
block), when S35 is used the block inside the wells (but nowhere else)
becomes contaminated (200-500cps) if either of these tubes is used.  Our
only conclusion could be that the S35 was going through the tube walls.  
Amersham now inform us that S35 is volatile at high temperature (and of
course it should be , its sulphur).  We are still trying to establish
whether the S35 is from breakdown of S35dATP or from any free label that
may be in the preps that are sold.  We are still in conference with
Amersham.  Presumably P32 is also volatile but we don't have the same
problem so my money is on free S35 in the preps.  
My point to the net is, has anyone else seen this problem?  Does this also
happen with standard thick-walled PCR tubes.  And CAUTION please check your

I will keep in touch as things progress.

Cheers, Klaus
Klaus Matthaei
Gene Targeting
The John Curtin School of Medical Research
The Australian National University
E-mail: Klaus.Matthaei at anu.edu.au

"I know that you think that you think that you understand what I am saying."
"But what I am saying is sometimes not actually what I mean."

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