Freezing competent E coli

Richard Near rocket1 at
Mon Mar 7 17:04:57 EST 1994

I've been having difficulty in the storage of competent
bugs for transformation either with CaCl2 or by 
electroporation.  Questions are: Is it better to freeze
in dry-ice-ethanol or snap freeze with liquid N2 (or
can one gradually freeze things in a "Revco"?
                                Usually the storage 
buffer is Ca in 10% glycerol or water with 10% glycerol--
does the purity/PH of the storage buffer have a large
                                   Finally, what are the
best conditions for storage (-70 or N2) and the rate at
which the frozen competent busg should be thawed.

Thanks much (if I get A good response I'll summarize and post)

rocket1 at

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