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eff. of transformation of E. coli

Nancy Lemieux nhl at binkley.cs.mcgill.ca
Sun Jul 10 14:06:34 EST 1994

>Dear Netters,
>I've been trying to make E. coli competent for transformation
>using a modified chemical method of Hanahan (prococol I in Molecular
>Cloning. A Laboratory Manual, by Sambrook et al.). They say you should get
>efficiencies of transformation greater than 5x10E8 for DH1, DH5 and MM294.
>I've tried it with DH5alpha and HB101, and the best that I've gotten was
>2x10E6. DH5alpha may have been an old culture (I got it from another lab),
>but HB101 was taken from a tube of frozen high efficiency cells from Promega
>and grown overnight in SOB medium, then diluted 100x with SOB + 20mM MgSO4
>and grown up to <0.4 OD600. Would anyone have an idea what my problem is and
>how to fix it? I would appreciate any help.


I have a very hard time believing such high competencies.  I know 10^5 and
10^6 are possible, but the only time I've seen efficiencies higher than
10^7 is with electrocompetent bugs.  With that I've had up to 10^8 and even
once 1X10^9.

Nancy Lemieux
Dept. of Biochemistry
McGill University
Montreal, Canada
nhl at binkley.cs.mcgill.ca

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