protein precipitates:HELP !

Clemens Suter-Crazzolara un691cs at
Thu Oct 6 02:29:50 EST 1994

I use over expression in E. coli to produce a HIS-tagged protein,
which is then denatured in urea and purified over a Ni-column.
The urea can be removed without problems, that is the protein does
not precipitate. This probably because I added a spot of Tween-20.
However, if I then concentrate the protein (I put the dialysis
tube on PEG15000) the protein precipitates like crazy.
I need this protein at very high concentrations, like 10 
mg/ml (quite a lot).C
What can I do ? most literature says that top circumvent
precipitation, the best is to keep the protein in dilute form.
can a precipitated protein regain its function if I would 
inject it in an animal, or add it to a cellculture ???

clemens, heidelberg, inst for anatomy

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