transformation efficiency Chung?

Cornelius Krasel krasel at
Tue Feb 9 15:36:40 EST 1999

Burkhard Hassel <b.hassel at> wrote:
> is anybody using the transformation method of Chung et al (PNAS 86,
> pp2172-2175) ?


> The authors claim an transformation efficiency of 1E7 to 1E8 per ug of
> DNA (pUC19) but I can reach only 5E5 (with bluescript and DH5 alpha
> cells).

I get up to 2E7 with pBR322 and JM109. (For 2E7, I must be really lucky.
Usually I get around 5E6.) I use old DMSO, treat the cells with TSS pH 6.5
(I think the original paper calls for pH 6.1 instead) and let them stand
one or two hours on ice before I dump them in the liquid N2. Re-thawed
cells work fine (at least when storage time is only a week, I didn't
measure transformation efficiency of long-time stored cells).


/* Cornelius Krasel, U Wuerzburg, Dept. of Pharmacology, Versbacher Str. 9 */
/* D-97078 Wuerzburg, Germany   email: phak004 at  SP4 */
/* "Science is the game we play with God to find out what His rules are."  */

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