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the function of -70 for X-ray film

Stephen Lessnick stevel at ucla.edu
Tue Nov 7 23:19:51 EST 1995

msz at bio.embnet.se (Michael Szardenings) wrote:

>I expose my 35S sequencing gels anyway at RT, because Idon't like to wait
>for thawing the next morning :-)

A couple of points...

1)  Why would one expose 35S sequencing gels at -70 degrees in the first 
place since they don't possess enough energy to make the enhancing screen 
worthwhile.  On the other hand, soaking the gel in salicylate or PPO 
would provide the enhancement effect, and then I believe it would make a 
difference to expose the gel at -70.

2)  You don't really need to thaw the gel after a -70 degree exposure.  
Just take the frozen cassette into the darkroom, and pull the film off 
while frozen.  Provided the X-omat is properly warmed up, the autorad 
will come out just fine.  I know, because I usually had to develop my 
films immediately before our a.m. lab meetings...

Have fun


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