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From: whycare@athena.mit.edu (nemo)
Newsgroups: sci.bio
Subject: DNA Purification
Message-ID: <1990Jun26.232707.20681@athena.mit.edu>
Date: 26 Jun 90 23:27:07 GMT
Sender: news@athena.mit.edu (News system)
Reply-To: whycare@athena.mit.edu (nemo)
Organization: Massachusetts Institute of Technology
Lines: 27

In an article written by a member of Bethesda Research Laboratories, I
read the following generalized description for partially purifying DNA
for restriction endonuclease digestion:

"Before reaction, remove these (tightly associated molecules such as
protein and ethidium bromide) by chloroform/phenol extraction and/or
ethanol precipitation
from high salt (2.5 M ammonium acetate)."

I'm not very familiar with the methods of DNA and protein purification
and would
like a good explanation for the above procedure. The chloroform and
phenol, I think, break up the proteins into their amino acid
constituents, which then are
trapped in the upper phase of the resulting mixture. But I'm not sure why the
amino acids end up in the upper phase. I don't understand how the DNA
and protein
would phase out in solution and what the function of the high salt
concentration
is. A detailed explanation of the above procedure possibly including the
concepts
of phase buoyancy, density, and other chemical processes and references
to journal articles, lab manuals, and other reading material would be
highly appreciated.

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