Phage DNA prep.-Expected Yield?

[Robert Roxby]

Just out of curiosity, what kind of yield do people end up with in large-scale 
lambda DNA isolations?  Theoretically there is a mg of DNA in 1L of culture 
having a titer of 2x10E10.  (Never mind that it seems difficult to get more 
than 1x10E10).  I can concentrate the phage almost quantitatively with PEG, but
after 2 CsCl gradients, step and equilibrium, followed by formamide 
extraction,  I only end up with about 20% of the theoretical amount of DNA. 
Not that this is bad as things go (try purifying an enzyme sometime), but the
books, such as CPMB, seem to imply that you will get more than that.  Also, if
you only end up the 400 ng/liter of culture, I don't see how the commercial
outfits can sell you 10 ug for $60, although I am sure 
it isn't CsCl purified.  Experiences or enlightenment appreciated.


Robert Roxby                           rr at bmmb01.umesci.maine.edu
Biochemistry, Microbiology             rroxby at maine.maine.edu
   & Molecular Biology                 72053,1712
University of Maine