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Ghost Plasmid !

Michael Moser moser at U.WASHINGTON.EDU
Tue Oct 17 17:29:55 EST 1995

Dear Rajesh,
	The E. coli strain BL21 DE3 that you describe is an expression
strain thgat contains an integrated form of T7 RNA polymerase.  I
seriously doubt that you will ever be able to recover good plasmid DNA
from this strain, much less clone with it.  I wouldn't be surprised if you
see a lot of strange bands that are resistant to digestion.  I suggest
DH5alpha or XL-1 blue for cloning.  These strains are engineered to 
reduce plasmid rearrangements and cut down on nasty glycoproteins that 
inhibit DNA modification enzymes.
Good luck! 

Mike Moser                                             Tel: 206-543-5354
UW Department of Biochemistry                          FAX: 206-685-1792
Box 357350                                        moser at u.washington.edu
Seattle, WA  98195-7350                     Make peace my beast is yeast

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