contaminating plasmids (fwd)

John Brunstein brunstei at
Sun Jan 16 03:45:37 EST 1994

	Thanks Sharon, this seems to be the gereral consensus as to the
source of the mystery band.  I am really glad to see that it does happen
to other people, I was beginning to think I was the only freak on the
planet with this problem!

---------- Forwarded message ----------
Date: Sat, 15 Jan 1994 22:33:01 -0600
From: "Sharon E. Plon" <splon at>
To: brunstei at
Subject: contaminating plasmids

I don't know how to post to the bulletin board but maybe you can post this
response.  I wonder if it really is a contaminating plasmid versus what we
used to call irreversibly denatured DNA which can occur with alkaline
lysis.  You can be left with small amounts of DNA that have not renatured,
tend to run slightly faster than the normal supercoiled circle and are
resistant to digestion due to their single stranded nature.  They should
be lost by Cesium banding or by altering the method so that it is properly
renatured.  Hope this was helpful

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