IPTG induction in phage display techniques - (Nov/11/2008 )

Hi guys,

I'm an invader here - a chemist doing biology I'm following standard procedures and everything is working relatively well, given my lack of experience. My question is, I add IPTG to my liquid culture after a certain amount of amplification to "induce" it, prior to adding my T7 Phage display library for amplification of the phage clones.

What on earth is "induction" of a culture, and how does the IPTG do it?

Thanks in advance

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Without meaning to fob you off, I'd suggest you try a quick Google for IPTG. But to show how friendly and helpful we biologists and biochemists can be (even to chemists ), here's a brief starter ...

IPTG is a non-hydrolysable analog of lactose. When lactose is found in the media (in organisms that metabolise it), a fairly complex chain of steps involving the production, inhibition or modified conformation of activator proteins and repressor proteins leads (normally) to the expression of of the lactose metabolism enzymes. The phage DNA in your library has the lactose promoter just before your gene of interest, so when the phage are added to the bacterial culture, IPTG causes that machinery to be switched on in the bacteria. When you add t he phage, they infect the cells, and synthesis of your recombinant protein is switched on, or induced, using the bacteria's lactose-metabolising machinery.

I hope that helps a bit.

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That's awesome, thanks *so* much.

I had tried google, honest - all I got was pages and pages of "IPTG was used..." "And then add IPTG..." "which was induced by IPTG...". So frustrating. This makes very much more sense!

Thanks again

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