when should I add IPTG? - (Aug/17/2010 )

Hii Bioforumers...

I need your help to overcome my research problem.

For expression of the recombinant enzymes, the transformed E. coli BL21 cells were grown in 1 liter of LB medium at 37°C containing 100 g of ampicillin per ml usually induced in mid-exponential phase (OD600: 0.5-0.6) with 1 mM IPTG.
If we use alternative medium other than Luria Bertani, does it mean that we have to find out the exact time of mid-exponential phase? or is it ok if we add IPTG into the culture just when the OD600 is between 0.5-0.6?

please help me..

Since the spectrophotometer is blanked against the media used, it has little impact on the reading, so you can use the same OD to estimate growth phase. The thing that might change is the time the culture takes to reach the target OD -- it may be quicker or slower, depending on how rapidly the cells grow in the media used.

Ok. Thank you HomeBrew