Archiving of plasmid DNA

Chris Boyd cboyd at
Thu Feb 10 06:24:33 EST 2000

Neil Fraser <njf16154 at> wrote:
: What is the general opinion on the best way to archive plasmid DNA for
: long term storage?
: I was thinking of lyophilising a couple of micrograms and then storing
: it at -20C. Does anyone have any evidence that this would not be the
: best way to go or any other suggestions.

Plasmid DNA of average size (< 10 kb) lasts at least 15 years (if
sufficiently pure) in TE at 4C.  Freezing ought to minimise damage by
trace nucleases that may be present, but I'm not sure that lyophilising
is beneficial. 

According to age-old editions of Maniatis, the canonical way of safely
storing plasmid DNA is in the dark at room temperature in saturated CsCl
solution containing EtBr. 

If I was asked to put money on it, I would say the best storage method
is to make glycerols of cells containing the plasmid and store these at
-70C.  If the cells turn out to be dead on retrieval, you can do a
miniprep on the dead cells and retransform. 

Best wishes,
Chris Boyd                      | from, but \    Medical Genetics Section
Chris.Boyd at             | not for,  /    MMC, Edinburgh Uni.,                       EH4 2XU, SCOTLAND

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