fresh transformations for protein expression??

Cornelius Krasel krasel at
Fri Jan 5 04:06:32 EST 1996

Torsten Boerchers (borcher at wrote:
> The more we were surprised that we now on two occacions
> with similar proteins encountered problems (i.e. no
> expression) which were solved by freshly transforming
> the E.coli (BL31(DE3)) with the expression vector instead
> of starting from a plate. 

In my and my colleagues' hands, the expression level in different
clones of transfored BL21(DE3)pLysS can be quite different. Therefore
we transform them, screen for clones which express the protein in
high amounts and make a glycerol stock of this clone.

It has happened once to a colleague of mine that he had to make
a new glycerol stock because the old one didn't express sufficient
amounts of protein any more.

I have no idea why this might be the case. Maybe the levels of
pLysS are different in different clones?


/* Cornelius Krasel, U Wuerzburg, Dept. of Pharmacology, Versbacher Str. 9 */
/* D-97078 Wuerzburg, Germany   email: phak004 at  SP3 */
/* "Science is the game we play with God to find out what His rules are."  */

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