CsCl/EtBr preps - Strange Band!

Vivian Miao vmiao at
Wed Nov 17 21:58:09 EST 1993

In article <9311171934.AA29765 at>, tupy at
("Tupy.Jon") wrote:
> > 
> 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 :-)

I'm not good at riddles, but has anyone in your lab guessed
polysaccharides?  That might fit the "symptom" of some culture product that
is medium dependent.

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