Recombinant protein precipitating upon freezing

David-Paul Minde via (by davidminde from
Fri Feb 27 14:20:15 EST 2009

... protein people dont keep their "pets" at -20 ... (better
snapfreeze&store-80C or keep in lN2)

2009/2/27, Pow Joshi <pow.joshi from>:
> 2009/2/27 <marguerite.b.colas from>
>> Hello Peter!
>> I work at a pharmaceutical company and have been working on this study
>> that involves freezing hemoglobin proteins, Every time we thaw our samples
>> we notice that they go cloudy.
>> At first we thought that we had been mixing our cell membrane pellet with
>> the cell content supernatant. However, the time we took extra care to
>> distinguish the supernatant from the pellet, we still noticed that our
>> samples went cloudy after thawing them from the freezer. All our samples
>> are kept in a -20c freezer.
>> If you think you might know what might be happening to our samples, please
>> let us know!
> methinks, you could try adding extra salt to the supernatant; or check the
> pH .... these are Fe bound proteins are'nt they?, perhaps if you need to
> have near neutral pH? ... I wonder if the Fe is forming hydroxides and
> precipitation out ...., in which case, you could add a bit of acid and
> resolublize?  ....... Dima, may be you will be able to answer if I'm
> completely off the track?
> Pow
>> thank you very much for your attention!
>> -----------------------------------------------------------
>> This e-mail was sent by GlaxoSmithKline Services Unlimited
>> (registered in England and Wales No. 1047315), which is a
>> member of the GlaxoSmithKline group of companies. The
>> registered address of GlaxoSmithKline Services Unlimited
>> is 980 Great West Road, Brentford, Middlesex TW8 9GS.
>> -----------------------------------------------------------
>> _______________________________________________
>> Methods mailing list
>> Methods from
> _______________________________________________
> Methods mailing list
> Methods from

David Minde MSc (TUM)

Cellular Protein Chemistry Room 707
Department of Chemistry
 Faculty of Science
 Utrecht University
 Padualaan 8
 NL-3584 CH Utrecht
 The Netherlands

 office phone +31 30 253 4105
 mobile phone +31(0)631154267

private address:
Griftkade 4 bis
3572 TW Utrecht

Science is what happens while we are making other plans (~John Lennon)

More information about the Methods mailing list