PEG removal

Dima Klenchin klenchin at facstaff.REMOVE_TO_REPLY.wisc.edu
Tue Jan 25 15:27:27 EST 2000


:Dear Fellow Scientists,
:I urgently need a method to remove PEG traces from proteins precipitated
:from human sera. I have already tried dialysis, however it is pretty
:much time consuming. If anyone has an idea I would appreciate...

Dialysis won't work well enough with PEG 6-8k or higher. Two ways to 
get rid of PEG: 

Reprecipitate the protein with ammonium sulphate (at 90% saturation 
practically all proteins will be ppted), then dialyse sals out or buffer 
exchange by microfiltration or gel-filtration. 

Dialyze protein into law salt neutral buffer and bind protein to 
strong anion exchanger (like Q sepharose). Again, over 90% of total
protein will bind under these conditions while PEG will not. 

Why is traces of PEG are undesirable anyway and if they are why use 
PEG to ppt proteins? 

        - Dima




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