Autoradiography: "Hole in the middle of Southern Bands"

pmiguel at pmiguel at
Fri Sep 10 11:34:09 EST 1993

This was recently posted to bionet.molbio.methds-reagnts:

+ Here's a weird problem: recently we have started seeing empty centers to
+intense bands in our PCR-Southerns (amplify, blot, probe with internal
+fragment, autorad).  Previous months of blotting never showed this.  Now
+past 2 weeks, several blots have it.  Sometimes only in certain lanes of a
+single blot, sometimes all.  Sometimes appears as a clear area in the lane
+(2 sides of band are hot), other times it's a "doughnut".  

  I'm convinced (as at least one other poster was) that this was actually an 
autoradiographic/photographic effect.  That is, the Xray film used is 
normally turned black from exposure to 32P betatron emissions (after the 
film is developed.)  But in cases where there is a very hot "band" it can 
actually disappear off the film -- or even be a clear band in grey or 
black background.  
  So I'm cross-posting this to sci.chem in the hopes of getting the details 
of the photochemical reactions going on here.  Presumably a certain amount 
of energy causes the silver salts in the film to convert to a non-soluble, 
black form, but above a certain amount of energy the non-soluble products  
convert again into some (new?) soluble form.

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