Plasmid DNA storage - (Jan/06/2005 )
planning to do pcr cloning of a promoter. will transfect the resulting reporter plasmid in cos cells. if i isolate the vector plasmid DNA from a megaprep. how long i can store it in the freezer. does long term storage cause any deterioration of the plasmid DNA.
Also please let me know the storage conditions.
I think you can store plasmid DNA at -20C forever. I have used 5-years old plasmid such stored.
At -80C, the plasmid should be stable in water for years. Be sure and aliquot to avoid multiple freeze-thaw cycles. Avoid self-defrosting freezers. I don't know if that matters, but I always hear it.
Over-time, plasmids begin to deteriorate, but probaly not enough to prevent their use. If using old plasmids and you have trouble, you can run some on a gel (0.8-1.0% agarose), cut the band of supercoiled DNA, and purify to get rid of excess nicked DNA.
In addition to storing the plasmid, store a couple 1 ml aliquots of the transformed bacteria to innoculate culutres down the road. Add 300ul 50% glycerol to 700ul of your maxiprep culture and freeze. Try to use microtubes that have a rubber sealing ring in the lid. These bacterial stocks should be safe for years as well.
- The Biology Ninja
dna should be stable at low temperatures for long times. i used plasmids stored for >7 years in a self-defrosting -20°C freezer. if they are no more ready to use "out of the box", i just transform them into fresh competent cells and there you go - new plasmid, all ok. and BTW i once forgot to freeze some minipreps for a longer period, 6 months that is, and left them in the cooler at 4°C. were just fine after half a year! could have beep just plain luck, though.
The problem with self defrosting freezers is that they cycle their temperature (heating up cooling down ) to avoid frosting up. This can have the effect of continually defrosting / refreezing your samples. They can also dry out samples in a similar way to freeze drying