Plasmid DNA spont. digesting - the long version :-)

plxsrt at plxsrt at
Fri Jun 4 08:05:13 EST 1999

If I am reading your essay correctly you get growth of the host cells
without plasmid under Amp selection.  This is not what you expect-
your cells are contaminated, get a fresh stock and start again.
Everything else you describe could arise from contamination.

If you stil get extra bands after the maxiprep and after you've ruled
out the strain it may be from RNA contamination (have you added RNase
to the cell resuspension buffer(1)?) or it may be due to poor timing
of prep stages  in which case you can get single stranded DNA coming

Simon T

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