Contaminating plasmid

Anderson at Anderson at
Tue Jan 18 21:50:26 EST 1994

Dear Folks,

    Here's my contribution.  I noticed that the manual for the Qiagen
columns describes something VERY similar to your mystery band.  They call
it "denatured supercoiled" plasmid and say that it results from letting the
denaturation step (ie. addition of NaOH after the lysozyme step) go too
long.  They claim it will run below the supercoiled band, will not reanneal
or cut with any enzyme, and one should simply shorten the base denaturation
time to get avoid getting it.  They don't provide any literature
references, but if their solution works it's not a bad explanation.  I'm
not sure how to fit that with the differences between bacterial strains,

                               Eric M.

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