Competent Cells - making the best

Daniel.Marc marc at
Mon Feb 22 09:11:34 EST 1999

The method I prefer ios the CCMB method "Calcium-manganese based". It is
described, along with other methods, in "Methods in Enzymology, vol 204,
pp63-113, 1991 (authors : D. Hanahan, J Jessee and F.R. Bloom)`.
It is easy and allows the prepa	ration of frozen competent celles.
In my hands, I get at least 10+7 col/microgram, usually after
the competent cells have been flash-frozen in liquid N2, then stored
at -80 degrees C (and I am not a "super preparator" of competent cells.
In brief : easy, rapid, consistently powerfull, and described with many
in the article cioted above.
Daniel Marc
INRA -Centre de Tours
37380 Nouzilly, France
marc at

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