glycerol to avoid protein precipitation?...

[Toumy Guettouche]

On Tue, 20 Aug 1996, Arioch wrote:

> 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 bmg.bhs.uab.edu)
> Graduate Student ( and Lord of Chaos...)
> Dept. of Biochemistry and Molecular Genetics...
> Milieu of Entropy (a.k.a University of Alabama at Birmingham...)
> 
> 
Glycerol basically prevents proteins from unfolding  (there is a paper 
from W. Welch et all at UCSF, I think from 1994). This prevents 
aggregation and precipitation of your protein as well. Another good thing 
is to use Hepes-buffer(if possible), which shows little change in pH when 
frozen (a major factor of enzyme inactivation; ref.: Hill and Buckley, Anal 
in Biochem., 192(2), 358(1991)). Also adding some  salt your protein likes 
(NaCl, KCl etc) might be a good thing. Some people also add EDTA, DTT and 
non ionic detergents like Tween 20 or Triton-X to prevent aggregation. , 
Hope that helps

Toumy