gel filtration vs dialysis

D.K. dk at no.email.thankstospam.net
Tue Jan 8 22:09:30 EST 2002

Dominic-Luc Webb molmed <domweb at mbox.ki.se> wrote:
>I want to get rid of proteases, mainly from an E coli
>expression system in which I am expressing an 86 KD
>protein (mammalian). The bacterial homolog is 32 KD
>and I also want this removed. This seems like classical
>job for gel filtration, but I am thinking that maybe
>the Spectra/por 6 or 7 RC dialysis tubing with 50 KD MWCO
>might work better (like preserving the volume) or
>maybe it would give better/faster separation. My
>understanding from reading is that bacterial proteases
>are typically very small, and well below this 50 KD
>Could someone please tell me if this is not such a
>clever idea and why or why not?

Not, because cut-off refers to retention, not flow-through.
In your case, 32K protein will not be effectively (in reasonable 
time with reasonable efficiency) dialyzed out in 50K cut-off
bag. Just do chromatogrpahy. 


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