nash effect with phagemids

suter at VAX.mpiz-koeln.mpg.d400.de suter at VAX.mpiz-koeln.mpg.d400.de
Tue Jan 25 04:21:14 EST 1994


John Nash wrote:

+I was curious as to why I could only get 1 X 10e9 some days and 1 X
+10e10 on others with the same batch of cells.
+Then I wrote down my controls on a grid...  They went something like
+this (from memory).
+Host: DH5 alpha or DH5alpha F'  - it didn't matter which.
+
+pUC8	1 x 10e10
+pUC18	1 x 10e10
+pUC18 derivative (from a colleague) 1 x 10e10
+
+pUC118 1 x 10e9
+pT7/T3 alpha 19 (BRL's phagemid) 1 x 10e9
+Now look at that... a ss phage origin (fd or M13) drops the
+electroporation efficiency down a log.

with 'classic' transformation protocols I usually measure the
competence of the frozen cells by transfetcing with 10 ng pBR322.
I cannot recall the above described Nash effect taking place if 
transfecting with pBS or puc118. Do the latter two transform less
well with both methods, or only with electroporation, and why ?
Does this relate to the mystery bands of 2 kb, discussed some
time ago on the net (presumably ss DNA ?)? 
I hate using phagemids, because I always
had a vague impression that they are cumbersome vectors for
cloning (in comparison to f.i. pT7T3-18). Anybody out there
made the same experience, or has suggestions why this may be so ?

cheers,
clemens
===============================================================================
Clemens Suter-Crazzolara, PhD
Max-Planck-Institut fuer Zuechtungsforschung
Abteilung Genetische Grundlagen der Zuechtungsforschung
Carl-von-Linne Weg 10,        D-50829 Koeln, Germany
Tel.xx49.221.5062-221    Fax.-213      e-mail: suter at vax.mpiz-koeln.mpg.d400.de
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