High Efficiency Transformation (library)

erfi at eel.sunet.se erfi at eel.sunet.se
Fri Feb 25 11:26:28 EST 1994

About a year ago, I bought one batch of high competency XL1 Blue MRF'
and one batch of noncompetent JM109 from Stratagene.  I used each of these
stocks to make my own batches of competent XL1 Blue and JM109 (made at
the same time with the same reagents).  The XL1 Blue had a competency
within 5x of the cells that I had bought, whereas the JM109 had a
competency 3-4 orders of magnitude lower.  The take home message, I think,
is that one should be sure that the particular batch of cells you start
with has the potential to be highly competent, no matter what procedure
you use.
	Regarding electroporation, there's an NAR article (Jacobs et al.
NAR 18(6) p1653 (1990)) claiming that dialysis increases the efficiency
500 fold.  In my hands, desalting your samples before electroporation
definitely makes a big difference, although I used 300 ul of Promega
DNA cleanup resin and eluted with 15 ul of deionized H20 (sorry Jim ;)).

Eric First (erfi at eel.sunet.se)

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