Electroporation optimal DNA conc.?

Michael Benedik bchs1b at Elroy.UH.EDU
Mon Sep 26 11:05:25 EST 1994

In article <1994Sep23.120049.1 at uwovax.uwo.ca>, 37_410 at uwovax.uwo.ca (OVan-Ham) writes:
>I've been having trouble getting decent transformation efficiencies with 
>electroporation.  Using pBR322 in DH5(alpha) all I'm getting is 
>2.8x10 to the 7 transformants per ug DNA.  This was done with 25ng DNA per
>40uL cells.  I thought that I should be getting a transformation efficiency
>near 10 to the 9 or 10.
>	It's been suggested to me that I could improve my transformation
>by using a lower concentration of DNA.  Has anybody else noticed an 
>improvement in efficiency with low DNA concentration?  Is there an optimal
>concentration that someone's found?  If so, please post to the group and/or
>e-mail me at OVan-Ham at UWO.CA.

It really depends upon whether you want a change in real numbers of 
transformants or in your apparent frequency. If you use 1ng of
DNA in your transformation then do the multiplication to get
transformants per microgram you will get a higher number,
but the max is usually in 10to8 range. However I don;t actually think
you will get more actual transformants in a cloning expt, just
a change in your apparent frequency. This is all a numbers game
the vendors play when selling comp cells.

Michael Benedik						benedik at uh.edu
Department of Biochemical Sciences
University of Houston

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