Storage of Midipreps - (Feb/07/2005 )
At what temperature do you store a pasmid midi prep? I always stored it at - 20 °C. Someone told me it´s better to store it at - 4 °C in the fridge!
i store my minipreps always at -20°! Once, when i need often a miniprep, i stored an aliquot in the fridge. After this use i forgot it in the fridge and after two month, i check my prep on agarose gel : it was a nice smear with one band in the middle !!!
You should really store your plasmids in the fridge (4 degrees Celcius) because constant freeze-thawing can nick the DNA. However if you want long term storage, the -20 degrees is probably OK.
a similar topic has been discussed here:
basically, both 4 or -20°C is ok, though there are some people who believe that self defrosting freezers can do very bad things to DNA