"Ghost" bands in plasmid preps?
Bernard Murray, PhD
spam at 127.0.0.1
Wed Nov 24 20:09:51 EST 1999
In article <383C5889.ED006DEB at cc.umanitoba.ca>, Rob Kirkpatrick
<kirkpat at cc.umanitoba.ca> wrote:
> Simon Dawson wrote:
> > Hi all,
> > Does anyone ever see what I can only call "ghost' bands if they
> > over-expose an ethidium bromide stained agarose gel of plasmid DNA? They
> > usually appear to run somewhat faster than what I would think is the
> > supercoiled DNA band and you only seem to see them if you overexpose the
> > gel.
> > Any thoughts? Ignore them (they don't seem to cause any problems with
> > subsequent manipulations)? I'm curious to know if anyone else sees something
> > like it.
> I'm told these are random cleaved DNA fragments that result
> from excess exposure
> to NaOH in the lysis step and that they are resistant to endonuclease
> But, I'm am not an expert on this and am somewhat interested in the answers to
> this question as well.
Paul Hengen tells the story in his March 1994 TIBS column and
the text is available here;
The ghost band usually runs about the same MW as ssDNA of
"non-denatured" plasmid. I don't believe "random cleavage"
Bernard P. Murray, PhD
bpmurray at cgl . ucsf . edu
Department of Cellular & Molecular Pharmacology, UCSF
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