the storage of the recombinant plasmid

Kristine E Gouveia Kristine.Gouveia at
Thu Sep 16 09:34:34 EST 1999

Hi Zeng,
I have been told not to store expression vectors in BL21.  If the
protein is toxic the bacteria will naturally want to alter the protein
in some way in order to protect itself.  I usually store my expression
vectors in a strain such as JM109.  When I need to purify some more
protein I do a fresh transformation.  Have you tried to retransform
your plasmid?
Kristine Gouveia
Bristol-Myers Squibb
Wallingford, CT

Zeng Yitao wrote:

> I have constructed a recombinant expression plasmid and kept it in
> E.coli Bl21 at -70 degree. Now it seems  not to  be able to express
> again, that is, there are some changes for this recombinant plasmid
> although stored at -70 degree. Does anyone know how to recover its
> expression?
> xin Gao
> Shanghai Institute of Medical Genitics,
> Beijing Xi Lu 1400/24,
> Shanghai 200042,
> P.R.China
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