I can't concentrate!

Ding Ming ming at ahabs.wisc.edu
Thu Mar 24 18:09:27 EST 1994


In article <mckegney.14.00093AA2 at unixg.ubc.ca>, mckegney at unixg.ubc.ca
(Brian Ellis - lab) wrote:

> Here is problem that i haven't encountered before.  After FPLC i attempt to 
> concentrate the fractions in centricon/centriprep tube (MW cutoff 10K), it 
> appears that my protein precipitates out of solution.  Has anyone else 
> encountered this problem.  The protein is 78 kD in size and is found in native 
> state as a tetramer.  

I am not sure 78kd is the size for one subunit or four of them. Is this
protein temperature sensitive? I meant if you used Centricon under room
temperature. Denaturation would be one possibility. I am also not sure what
kind of column were you using in fplc and if that was an ion-exchange
one(monoQ or S), it is possible that you were getting some very
concentrated fractions and further concentration will force the protein to
be precipitated out of the solution. Another possibility is that salts or
organic slvents, which is required for the solubility of the protein(like
most globulin proteins are only soluble in salt solutions), were
ultrafiltrated while the protein was concentrated. Hope this helps. Good
luck!
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Ding Ming
University of Wisconsin-Madison
Telephone: (608)265-3544     Fax: (608)262-7420
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