Recombinant protein precipitating upon freezing
(by legatekBLAH from hotmail.com)
Sat Feb 28 03:47:43 EST 2009
marguerite.b.colas from gsk.com wrote:
> 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.
Is there a reason you're keeping them at -20C? Normal protein storage is
at -80C, unless you're working with an enzyme that loses activity upon
freezing, in which case -20C in 50% glycerol is acceptable. You can try
adding glycerol to 50% to keep the protein cold but not frozen.
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