concentrating proteins

Alan Kaiser alkaiser at
Fri Sep 9 12:53:56 EST 1994

In <Pine.3.89.9409080812.A27488-0100000 at> jbooth at ACS.UCALGARY.CA (Joseph Booth) writes:

>	I've read that you can concentrate a dilute solution of proteins through 
>the addition of dry G25 Sephadex. I was wondering if anyone who has used 
>this method could comment on how effective it is or if there are any 
>disadvantages (like binding of the protein to the beads) that I should be 
>aware of. Also, any alternative suggestions for a gentle method of 
>concentrating proteins would be appreciated. Thanks.


I'm not sure, but this might be the same thing as using polyethylene
glycol (PEG) to concentrate proteins. I use this method on a regular
basis and it works fine. Put your dilute protein solution in a
dialysis tubing with an appropriate MWCO (less than the MW of the
protein) and cover the tubing with PEG. I use Sigma PEG (avg. MW
10,000) but there is also a product available from Calbiochem called
Aquacide but it is more expensive. These powers draw the water out of
the dilute solution and therefore concentrate the sample. I have
eliminated 10-15 ml of water in about 6 hours or so at room temp (I
work with very stable peptides). The dry G25 Sephadex may serve the
same function since it swells when you add water to it. If this is the
case, the PEG or Aquacide would be more efficient than Sephadex since
it can absorb more water (I think Aquacide is better than PEG at doing
this). You will have to be careful to not contaminate your sample with
the PEG.

Hope this helps
Alan Kaiser
Rutgers University
New Brunswick, NJ
alkaiser at
Alan Kaiser
Rutgers University, Graduate Program in Microbiology
alkaiser at

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