BL21(DE3) pLYSe/s competent cells

Francois Coulier coulier at
Mon Nov 4 15:45:28 EST 1996

On Mon, 4 Nov 1996, Dr. Duncan Clark wrote:

> Hi Folks,
> Has anyone had any hassle making electrocompetent cells of the above.
> Thawing from -70C lyses our supposed electrocompetent stocks. I know
> they carry T7 lysozyme but I wasn't aware they were that sensitive to
> one freeze thaw. I'm now going to make ordinary competent cells and use
> them immediately but would like any comments.
We have no problem with our BL21(DE3) pLYS S. we do make them _ordinary_ 
competent with cacl2, and store them at -80C, in 10 or 20% glycerol. If
you want  to know exactly how much glycerol we use, I can check. It is not
enough to prevent freezing, though.

Francois Coulier
INSERM Unite 119
27 bd Lei Roure
13009 Marseille

tel 33 (0) 4 91 75 84 11
fax 33 (0) 4 91 26 03 64)
email: coulier at

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