Storage temperatures

Paul N Hengen pnh at fcsparc6.ncifcrf.gov
Thu Jun 29 11:53:36 EST 1995


 Jim Hartley <jhartley at access2.digex.net> writes:

|for differing suspensions (i.e. plasmids).
|                                ^^^^^^^^
....
: Do you mean that repeated freezing and thawing can do damage to
: my plasmid DNA preps?

> 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.

Thanks for the response Jim.  I did know about the old BRL study, and I was
trying to see if Ted meant all samples in the freezer, including plasmid DNA.
I did e-mail him about the study done by BRL that concluded there is no damage
done to DNA samples by repeated freeze/thaw cycles - granted the test for
damage was by looking at the DNA on EtBr stained agarose gels.

@article{Anonymous1983,
author = "Anonymous",
title = "Does freezing and thawing of {DNA} solutions
insert nicks in the double helix?",
journal = "B.R.L. Focus",
volume = "5",
number = "2",
pages = "10",
year = "1983"}
 
*******************************************************************************
* Paul N. Hengen, Ph.D.                           /--------------------------/*
* National Cancer Institute                       |Internet: pnh at ncifcrf.gov |*
* Laboratory of Mathematical Biology              |   Phone: (301) 846-5581  |*
* Frederick Cancer Research and Development Center|     FAX: (301) 846-5598  |*
* Frederick, Maryland 21702-1201 USA              /--------------------------/*
* - - - - - Methods FAQ list -> http://www-lmmb.ncifcrf.gov/~pnh/ - - - - - - *
* - - -  Anonymous FTP from ftp.ncifcrf.gov as file pub/methods/FAQlist - - - *
*******************************************************************************



More information about the Methods mailing list