CsCl/EtBr preps - Strange Band!

Tupy.Jon tupy at
Tue Nov 16 22:22:58 EST 1993

Hi NetLand!

I have a question for all of you who still indulge in the toxic messiness of
CsCl/EtBr density gradient plasmid preps: from time to time people in this lab have
been discovering an annomolous *white* band that seems to migrate just below (if
they're lucky) the banded plasmid.  Sometimes, for the unfortunate, it occupies
the same spot on the gradient as the desired DNA.  

No one around here seems to be able to identify the intruding band, but it only
manifests itself when the prep cultures are grown up in TB (LB resolves this
problem).  I know that in such gradients, protien goes up and RNA, down, so
what's white and stays the middle? (sounds like a bad riddle :-)

Jon Tupy
tupy at

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