Storage temperatures

jim hartley jhartley at
Thu Jun 29 05:24:41 EST 1995

A few years back a guy here took a plasmid and cycled it between 37 C and 
dry ice, my memory is 30 times, and took out samples during the process.  
By gel analysis the degree of supercoiling was entirely unchanged by all 
this freezing and thawing.  I know there is an ancient bias that freezing 
is bad for plasmids, but for DNA less than lambda size I have never seen 
any data demonstrating this.  I fear microbial growth and slow enzymatic 
degradation much more than freeze/thaw cycles, so all my DNA is tucked away in a frost free -20 freezer.

Jim Hartley
Life Technologies, Inc.
On Wed, 28 Jun 1995, Paul N Hengen wrote:

>  In article <nbai.12.00088C53 at| 
>  nbai at (Ted G. Martin) writes:
> | I have read discussions here on correct freezing temperatures and longevity 
> | for differing suspensions (i.e. plasmids). What I question is the control over 
> .                                 ^^^^^^^^
> | any of these temperatures.
> | 
> | Alot of problems occur not due to the actual temperature but allowing the item 
> .         ^^^^^^^^
> | to pass across critical crystalization phases such as 0, -20, -70, and -130 
> | C on a repeated basis. It may improve your efforts to ensure that temperature 
> | set points on your storage devices are set well on side or the other of these 
> | critical phases.
> | 
> | Ted Martin
> | National Bio-Medical Archives (NBAI)
> Do you mean that repeated freezing and thawing can do damage to
> my plasmid DNA preps?
> -Paul.

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