Phenol pH?

Alan Smith alansmith at
Tue Oct 31 17:12:26 EST 2000


I have a question about the pH of Phenol and its effect on DNA.  According
to Maniatis phenol must equibilated to pH 7.8 or above to prevent the
movement of DNA into the organic phase (I have  done this my whole life). I
also have preformed many RNA extraction in which case acidic phenol is used
to remove DNA.  However, digging through the refrigerator in my lab I
realized to my horror that every one in the lab was using water saturated
phenol about pH 6.6 from Fisher, but nobody is having problems with loss of
DNA to the organic phase in either plasmid or genomic DNA preps.  The techs
didnt even know why little bottles of Tris came with the phenol and just
left them sit in the fridge (found about 6 of them)  Does the addition of
chloroform somehow prevent DNA from moving into the organic phase?  As far
as I know straight phenol is not used in any of the labs DNA preps, just
P/C/I.  Could someone please describe to me how the chloroform can protect
the DNA from being removed by the acidic phenol.

Thank You

Alan Smith


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