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

More information about the Methods mailing list