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[ccp4bb]: semet-labelled protein question

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     We are attempting to produce semet-labelled protein using the M9/
     glucose approach (as done by Van Duyne/Clardy) and BL21 cells.  
     However, we find that our cells are not able to grow past an OD600 of 
     0.1 on this minimal media.  Such a low density of cells translates 
     into a very low yield of protein for us and we are looking to increase 
     the density of cells before inducing.  Initially, I thought that 
     glucose was the limiting factor and increased the glucose in the 
     minimal media from 0.5% to 5%.  However, again, the cells would not 
     grow past an OD600 of 0.1. It seems that something else is limiting 
     cell growth.  Might anyone have any suggestions on how to modify this 
     minimal media to get improved cell growth without comprimising the 
     ability to get semet incorporation?   Any ideas are appreciated.
     I should also mention that the protein is an NTPase and therefore
     its expression has a certain metabolic cost.
     Thanks in advance.