Uh-oh, open freezer door...

Hiranya Roychowdhury hroychow at NMSU.EDU
Fri Jun 9 17:12:22 EST 1995


On 9 Jun 1995, John Ladasky wrote:

> Greetings, folks,
> 
> 	The other day I came in to the lab to disocver that our -20 C
> freezer was not closed completely.  (My conscience is clear, I know that
> it couldn't have been me.)  There was a small puddle of water on the
> floor in front of the freezer door, although the ice on the coils hadn't
> melted much.  I freaked and moved all the enzymes (which were in Strata-
> coolers) to another freezer.  After a few hours, the freezer had returned
> to -20 C and I brought the perishable reagents back.
> 
> 	Right after cleaning out the enzymes, I checked the air tempera-
> ture in the freezer and found it to be hovering around zero C.  Unfortu-
> nately, the Strata-coolers weren't much colder than zero, either.  So, I
> estimate that the enzymes were subjected to these conditions for a few
> hours.  My question is: what are our chances?  Can we use these enzymes
> or will we find that they have been largely inactivated?  I would be 
> grateful if people whould share their experience.
> 
> -- 
> Unique ID : Ladasky, John Joseph Jr.
> Title     : BA Biochemistry, U.C. Berkeley, 1989  (Ph.D. perhaps 1998???)
> Location  : Stanford University, Dept. of Structural Biology, Fairchild D-105
> Keywords  : immunology, music, running, Green
> 
> 
Enzymes vary in their sensitivities towards temperature changes. In 
general, there should not be significant loss of activity in them due to 
a few hours at zero degrees. The enzymes come already stabilized in 50% 
glycerol, which prevents drastic physical changes due to freezing. 
However, if the freezer is habitually being maintained at or near zero, 
despite its -20 claim, then one needs to worry. Otherwise, nucleases, 
ligases, kinases and even polymerases will survive well at 4 degrees
overnight. In one instance, I used a tube of XhoI that was accidentally 
left outside overnight on a rack in the cold room (our enzyme freezer 
used to be in the cold room). The enzyme cut my vector fine. 

			>>>>>>>>>>>>>>>>>>>>>>>>>>>
			  Hiranya S. Roychowdhury
   			  Plant Genetic Engineering Lab.
			  Box 3GL, NM State Univ.
			  Las Cruces, NM 88003
			  Phone: (505) 646-5785
			  hroychow at nmsu.edu
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