glycerol to avoid protein precipitation?...

Bill Prichett William_P_Prichett at
Fri Aug 23 18:36:48 EST 1996

Arioch wrote:
    I read a long time ago in a protein purification and protein methods book that adding glycerol to a stock 
and freeze at -20 prevents a couple of things that help to maintain protein stability.  First, I prevents ice 
crystal formation.  Thus you do not have micro sheering stresses placed upon the protein.  You also do not have 
to warm the sample to take an aliquot. thus know freeze thaw cycles( which are probably an accumulation of both 
effects that I will mention).  We routinely add 1 volume of glycerol to all antibodies that we use (final conc. 
= 50% glycerol).  I have had antibody stocks that I go back into years later with out hesitating about it's 
quality.  Second, the book also mentioned that even in well buffered samples, as ice cystalizes, the 
microenvironment that the protein is in can change drastically.  pH shifts occur on a micro scale, salt 
concentrions as well as other additives, change (concentrate).  The book stated, I believe, that you could get 
a +/- 1-2 pH unit swing in a sample.  That could be as much as 4 units.  Some proteins can not handle so much. 
 I hope this helps.  As far as a reference I believe it was either "Protein Methods" by Bollag and Edelstein 
Pub-Wiley-Liss  ISBN 0-471-56871-6  or "Guide to Protein Purification" Ed Deutscher, Academic Press ISBN 
0-12-213585-7 (This is also the same as methods in enzymology v182).  Good Luck,


> hey all,
>         ...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).
> has anybody tried this??  i wouold really appreciate any help on
> this...thanks...
> Arioch (siyer at
> Graduate Student ( and Lord of Chaos...)
> Dept. of Biochemistry and Molecular Genetics...
> Milieu of Entropy (a.k.a University of Alabama at Birmingham...)


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