Q. About Protein Expression !!!

Thomas Schwartz tomblack at MIT.EDU
Fri Mar 14 02:52:44 EST 1997

Miss ELLA CHAN wrote:
>   Dear all,
>   Could somebody kindly tell me at which OD600 will be the optimum
>   condition for the induction of protein expression by using IPTG
>   in bacterial strain ?

I've got the following suggestions:

look which is the maximal OD600 your cells grow to, i.e. after overnight
This depends highly on the strain you use and the repression level of
the protein you want to overproduce.
For cells which grow no further than OD600=2 I induce at OD600 = 0.5 -
0.8 for cells which grow up to OD600=4 I induce at OD600=1.
This always worked fine.
Look for your OD600 after the induction. If cell growth stops after
around 1h means, that your protein is probably expressed very well. To
get high amounts of cells in this case you can induce at even higher
cell densities. 

Good luck, Thomas.

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