Potassium acetate

tfitzwater at gilead.com tfitzwater at gilead.com
Mon Jun 12 12:52:57 EST 2000

I realized as soon as I sent the first posting on potassium acetate that I
had left out one detail regarding the addition of Solution III:  The
potassium salt of dodecyl sulfate (formed when combining SDS and potassium
acetate) is very insoluble.  This is what forms the precipitate that pulls
everything else out of solution.  The earliest (1978-1982) plasmid prep
protocols used sodium acetate.  Potassium acetate did not come into use
until T. Maniatis, et al. published Molecular Cloning and included the
Ish-Horowicz and Burke 1981 modification of Birnboim and Doly 1979.

Warren Gallin commented that the glucose in solution I buffers the pH on
addition of solution II.  Tris has only a single pKa, at around 8, whereas
cyclic glucose will give a proton at around 12.  (Thanks, Warren)

Tim Fitzwater
Principal Research Associate
Gilead Sciences


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