Frozen restriction enzymes

[Rafael Maldonado]

On 15 Oct 1996, Michael Sachsamanoglou wrote:

> What happens when a restriction endonuclease solution is frozen to -80C?

It gets solid.

> Is it normal for the 50% glycerol storage solution to solidify at this 
> temperature? 

Sure it is.

> I've heard sometime ago that if a restriction enzyme 
> freezes it is dead. Is this true? 

No. When it is shipped in dry ice, it is normally frozen, is it not? But 
if you find it frozen at -20, normally beacuse some ice from the bucket got 
in to the tube, it may be dead.

I have heard that many frozen/defrozen cycles are bad, but I never tested 
it. Lower temperatures will be better for conservation, but I think we keep 
it at -20 because the convienence of the liquid phase.



Rafa