Help with LiAc transformation

Erin Yoshida eyoshida at
Tue Dec 6 18:12:05 EST 1994

I am trying to transform S. cerevisiae, strains AH22cir+ and
YPH98, with an episomal yeast shuttle vector.  I have been
using the lithium acetate transformation protocol cited in
Methods in Enzymology (194):186-187, but my transformation
efficiencies have been very low.  I have not worked with yeast
very much in the past, and do not know what the critical parameters
are.  For instance, is it alright to begin the cultures with yeast
that have been maintained on YPD plates for several months at 4
degrees?  Or, is it better to freshly streak from a frozen stock
culture onto YPD plates and then begin your liquid culture from
the plates (as in bacterial competent cells)?  Is it recommended
to include sorbitol in your selective plate media?  How long should
one heat shock the cells at 42 degrees (I have seen anywhere from
5 to 15 minutes)?  Any other tips to increase the transformation
frequency would be greatly appreciated.

Erin Yoshida
Department of Biology
University of Ottawa, CANADA
eny at

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