help protein concentration

[Thomas Seib]

In article <5k4lcn$6b4 at mserv1.dl.ac.uk>, Mark Bryant
<jmb36 at mole.bio.cam.ac.uk> wrote:

> How can I concentrate a purified, recombinant His-tagged protein to near
> 10mg/ml without it precipitating out of solution? Any tips on buffers or
> salts to try?
>         Mark Bryant
>         Dept. of Clinical Biochemistry
>         University of Cambridge 


Dear Mark,
a good method to concentrate proteins mildly is to dialyze them
against a buffer containing 50 to 80% glycerol, if glycerol does
not disturb. You can also use a solution of PEG with an average 
Mol. weight of 20000, which should be as concentrated as possible.
The advantage here is that the PEG does not enter the sample
if you use a dialysis membrane with cut off <10000 Da.

Matthias

-- 
Thomas Seib
Kantstr. 12
66292 Riegelsberg