Cornelius Krasel wrote:
>> Arioch (sai at topaz.microbio.uab.edu) wrote:
> > ...had heard seomwhere that adding glycerol to purified protein
> > and then freezing them keeps the breakdown at a minimum and prevents
> > protein precipitation (after freeze-thawing from the -20 degrees C).
>> It's a common way to freeze proteins - just think of all that restriction
> endonucleases :-)
>> To find out if it is of help for your protein of interest, you have to
> try. Try different glycerol concentrations (actually, above approx.
> 30% v/v glycerol the solution won't freeze anymore). Some proteins
> don't like -20 degrees C. In my experience, glycerol often improves
> activity. For example, protein kinase A doesn't like to be frozen in
> the absence of glycerol.
I think there are some additional positive effects of glycerol.
The intracellular protein concentration is around 100 to 300 mg/mL.
Usually, this is not a concentration achieved in the laboratory, a
possible reason why some proteins are not too stable under these
lab-conditions. Addition of glycerol probalby 'mimicks' the osmolarity
of the inner cell.
Glycerol is a good scavenger of radicals; during cooling or especially
freezing, the protein solutions saturate with air. Glycerol probalby
protects against oxygen-radicals.