protein concentration and desalting

[Dr Engelbert Buxbaum]

Am 07.09.2007, 09:02 Uhr, schrieb Esmaeil Sadroddiny  
<sadresm2002 from yahoo.com>:

> I am trying to concentrate low amount of protein in solution. In  
> parallel protein sample should be salt free as much as possible. who can  
> > introduce me an efficient method?

Cheap, but time consuming: Fill your sample into a dialysis bag, dialyse  
o/n against the buffer of your choice. Then dialyse against solid  
polyethylenglycol to remove as much water as required. Check the sample  
frequently, as you can concentrate it to dryness that way!

More convenient but expensive: Ultrafiltration with centrifuge filters   
(small sample size, up to a few ml) or Centicon pressure concentrators  
(large sample size). Select a membrane that retains your protein of  
interest but lets all smaller contaminants (including water) pass.