Cellular depression of freezing point. Help!!

Paul. S. Brookes. psb at mole.bio.cam.ac.uk
Wed Nov 8 04:46:54 EST 1995

On 7/11/95, richwill at innotts.co.uk wrote:-

>Can anyone point me in the direction of information about what chemicals
>some animals use to depress cellular freezing point?

   There's quite a lot of evidence that fatty acid composition of cell
membranes is altered to make them more or less fluid depending on the
cold/heat acclimation of the animal concerned.  This is all based around a
property of lipids termed the "phase transition temperature" (Tm), i.e. the
temperature at which lipids will go from a liquid crystal state to a gel
state.  For most lipids this is somewhere between zero and 20 degrees
Celcius, but it gets a bit more complicated for lipid mixtures.
   Changing the unsaturation index of the fatty acids is thought to be one
way of depressing cell freezing point by lowering the Tm of the membrane
lipids to below that of the ambient temperature, thereby keeping the lipids
in their gel state.  This is essential so that membrane based phenomena can
continue at depressed temperature.

As for what happens inside the cell, I think its something to do with
anti-freeze (polyethylene glycol).... anyone?


^^^^P. S. Brookes^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Department of Biochemistry,    Tel' 01223 333649
University of Cambridge,       Fax' 01223 333345
Tennis Court Rd,               E-mail psb at mole.bio.cam.ac.uk
Cambridge, CB2 1QW, UK.


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