why glycerol?

[xyzzyx]

In article <Pine.PMDF.3.91.951016170717.591408591A-100000 at utkvx.utk.edu>, 
abel at UTKVX.UTCC.UTK.EDU says...
>
>> Hi, everybody! I am a student and I often find in the literature that 
people
>> use glycerol to store proteins or enzymes. I was told that glycerol help to
>> stablize the protein, but through what mechanism?
>> thank you for your advise. Alan
>
>As far as I know, glycerol is a "cryoprotectant" that is used to retard 
>the freezing of protein solutions so you don't continually freeze and 
>thaw your favorite protein.  In a cell suspension, the glycerol 
>minimizes the total concentration of water that can freeze and form ice 
>crystals that can damage cells.  Anyone have any more to add that I don't 
>know about?
>
>Michael Gregory Abel *   **   **   **   **   **   **   **   **   **   **
>University of Tennessee *::* *::* *::* *::* *::* *::*Abel at utkvx.utk.edu:*
>Department of Microbiology::*::::*::::*::::*::::*::::*615-974-2933::*::::*
>Walters Life Sciences Bldg:* *::* *::* *::* *::* *::* *::* *::* *::* *::*
>Knoxville, TN 37996-0845 **   **   **   **   **   **   **   **   **   **
>           "We are constantly faced with great opportunities 
>              brilliantly disguised as insolvable problems."
>
I seem to recall reading, a while back, that the stabilizing effect of certain 
polyols is the result of a phenomenon whereby a shell of water is forced 
around the  molecule by the solute molecules.  That is, there is a zone 
directly adjacent to the surface of the molecule which is actually depleted in 
the added solute.  Sucrose is supposed to act predominantly in this manner.  
Glycerol is said to act in this manner, but additionally "coats" exposed 
hydrophobic residues and minimizes their ability to aggregate.  If I don't 
forget (which I might), I'll try to dig up a reference.  Email me if I forget.

George Trager