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Glycerol in Freezing media -Reply

David A. Mullin damullin at MAILHOST.TCS.TULANE.EDU
Wed Sep 25 17:17:47 EST 1996


>In article <s248f09c.077 at mc.edu>, Snazelle at MC.EDU (Ted Snazelle) writes:
>
>> Supposedly the glycerol prevented ice crystal
>>formation which would have disrupted the structure of the
>>immunoglobulins.  
>
        This is the story that I heard from a eukaryotic cell culture
person some years ago regarding the mechanism by which glycerol or DMSO
protects cells during the freezing process.  It sounds as reasonable as any
of the other stories that I have heard:

        As the temperature drops, ice crystals form in media outside of the
cells and the activity of the water outside of the cells decreases.  This
results in diffusion of water out of the cell, and as a result the
concentration of ions inside the cell increases.  The increased salt
concentration inside the cell results in some protein denaturation and
reduced viability. Part of the mechanism by which Glycerol and DMSO work is
by depressing  the freezing point of growth media outside of the cell. 
DMSO and Glycerol thus reduce water loss by the cells as they freeze.  I
think that the cells are supposed to freeze before the glycerol-containing
media outside of the cell freezes.  For good viability, bacterial cells
should definately be stored frozen.  I have cells that were frozen in DMSO
broth at -70oC  more than 10 years ago which are still viable when streaked
out.


        Sincerely,


        David Mullin




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