Strange Southern Problem

brian bettencourt bbettenc at
Thu Dec 4 09:31:16 EST 1997

	Been doing fly genomic Southerns w/ great success over the past
year: nytran mb's, neutral transfer, turboblotter (S&S) system, DIG-probe,
colorimetric detection (I look at hsp70s, very good conservation, super
strong signal).  Anyway, recently things have gone awry and no one can
figure it out.  Basically these are the symptoms: ridiculously high
*generalized* background (not in lanes), but ***only on the top ~1/2 of
the blot***.  It looks like a shadow of the gel, complete w/ wells, down
to a line roughly corresponding to where ~1.5Kb frags are.  Below that the
shadow is gone and the blot looks fine.  Very strange.  Don't think it's
blocking, Ab, developing, or anything post-hyb b/c the bkgrnd is only on
part of the blot.  This has been repeated now for three blots.  It's not
due to overlapping in the hyb tube.  The only things I've changed recently
are 1) new restriction scheme, smaller frags, thus slightly stronger gel. 
2) OVERNIGHT GEL - could this be leading to an EtBr front or something? 
Any ideas?  No one has heard of this.  Thank you very much.

 Brian Bettencourt  *  b-bettencourt at  *  (773) 702-8096 / 5228
 Organismal Bio & Anatomy  *

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