desalting/concentrating low MW proteins

Dima Klenchin klenchin at
Wed Feb 3 22:45:36 EST 1999

In article <79abc8$ulb$1 at>, ardibat at wrote:
>In article <798aqf$lqu$1 at>,
>  Eugene Hone <eugeneh at> wrote:
>> Hi,
>> Does anyone know of/have a method for concentrating and desalting a solution
>> containing a 4kDa protein?
>> Cheers
>One solution for your problem (the problem is that a 4kD protein is too small
>for dialyse) is to use a G25 resin.
>Just put the resin in a tube with a very small hole on the bottom, pour your
>protein solution and give a very short centrifuge tour to collect the
>concentrated protein.
>For desalting... I don't know...

Keep in mind that G-25 has nominal cut-off of 5K for globular proteins. 
Another thing is that old dry G-25 leaches something (dextranes? 
crosslinkers?) which inhibits various enzymatic reactions. For 
chromatography it's OK since the column gets washed anyway but
for for the purpose of concentrating, this can be a reservation. 

        - Dima

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