Supercoiled DNA

[Darren Boehning]

Has anyone noted plasmid DNA no longer being supercoiled?  It seems that 3
of my plasmids (all about 15kb) are no longer being supercoiled by the
bugs (DH5alpha).  I have tried LB and TB, and both CsCl preps and Wizard
preps are giving the same result.  I also re-transformed the bugs with
older supercoiled preps, and subsequently they are no longer supercoiled. 
Any help would be appreciated.

Please respond to boehnin1 at jeflin.tju.edu

Darren Boehning
Dept. Pathology and Cell Biology
Thomas Jefferson University