HELP!How do you properly count radiolabelled DNA on filter paper disks?

Paul E. Ulanch PULANCH at
Fri Jun 16 17:45:02 EST 1995

In our lab re routinely measure incorporation of nucleotides into DNA or RNA. 
 You simply dot a small amount onto Whatman DE81 paper and wash twice in 5% 
Na2HPO4, once in water to remove excess phosphate, once in 100% EtOH to remove 
most of the water, and quickly in Ether.  Five minutes for each wash is fine 
and two minutes for the ether wash is more than enough.  Just remove the paper 
filters (we quarter each filter to get 4x as many uses) and air dry them in a 
hood.  It only takes a few minutes.  Scintillation count and you are all set. 
 The high phosphate solution removes all free nucleotides.  It is a heck of a 
lot easier than ppt with TCA.  The EtOH also removes some compounds that may 
interfer with the scintillation counting. 

Good Luck, hope this helps...

Paul "Goose" Ulanch

Dept. Biochem/Biophys
Texas A&M University
College Station, TX   77843-2128
(409) 847-9379

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