Is there any posibility to store chemical competent or electrocompetent E coli al -20 ºC? Any protocol?
Thanks
You can, but it's not recommended. The best competent cells are from a fresh culture and actually used on the day. That said, from experience, they will last at -20 a day (night) or two, but transformation efficiency will be much lower. Best to keep them at -80.
Check out these:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3939052/
http://openwetware.org/wiki/Electrocompetent_cells
Edit: and so say the experts:
https://www.neb.com/products/c2989-neb-5-alpha-electrocompetent-e-coli#pd-notes
It's not recommend !!!!!!!
When I study in the bachelor degree, my advisor purchased chemical competent E.coli (DH5 alpha) from company and stored at -20 C. After 2 days transformation efficacy was lower.
Hi Martin,
I never store my competent E. coli cells at -20C freezer. They should be stored at -80C all the time.
Agreed: minus 80 is preferred. However, it depends on what you are doing. If you are subcloning a vector, even if the efficiency is very low (less than 1% of original) you will probably still get some clones that will be OK. If its a library, I would always use the freshest possible cells. Of course you can always determine the loss of efficiency at minus 20oC experimentally - then you know for sure and for the future. I imagine that this will vary considerably according to the host cells.
Geoff, i do not need to make any library, just plasmid cloning, and my chassis is E. coli, i will try to store some at -20 ºC and then determine the loss of efficiency
Thanks!
It is not advisable to store the competent cells in -20 degree. I assume you are asking about the storage then it is definitely -80 for long-term. If you are asking about after the competent cell preparation, then I would recommend you keep at 4 degree in ice box. It will give you much efficient cells even 5 days after. Regularly change the ice and seal the tube properly.
I was wondering about -40ºC? The reason is that there are rather inexpensive wireless freezer monitors that work down to -40ºC, which could give me warning that my -80 has a problem before it reaches -20ºC or higher.
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