EtOH precipitation

benedik at uh.edu benedik at uh.edu
Fri Mar 3 18:11:25 EST 1995


In article <3j84ej$8va at usenet.ucs.indiana.edu>
Rick Conrad <rconrad at bio.indiana.edu> writes:

> Path: news.uh.edu!swrinde!howland.reston.ans.net!vixen.cso.uiuc.edu!usenet.ucs.indiana.edu!news
> From: Rick Conrad <rconrad at bio.indiana.edu>
> Newsgroups: bionet.molbio.methds-reagnts
> Subject: EtOH precipitation
> Date: 3 Mar 1995 22:15:47 GMT
> Organization: Indiana University, Bloomington
> Lines: 5
> Message-ID: <3j84ej$8va at usenet.ucs.indiana.edu>
> NNTP-Posting-Host: splatter.chem.indiana.edu
> 
> Anyone out there have a history of the different salts used in ethanol
> precipitations?  I know ammonium acetate is supposed to leave small
> molecules in the supe, but why sodium acetate versus chloride (or vice
> versa)?  Any citations relating to this (I've read the basically non-
> informative Maniatis and Red Book blurbs) would be appreciated.


My recollection of past history (it used to be that we oldtimers used
NaCl then we switched to NaAc) was that solubility was the reason for
the changeover. NaAc was more soluble in ethanol at suitable
concentrations for DNA precip and therefore you had less problems of
salt in your DNA pellet.

I remember having big fat NaCl pellets in my ETOH ppts when I chilled
them in dry ice ethanol baths. 

Things have sure gotten simpler...

Michael Benedik               benedik at uh.edu
Biochemical Sciences
University of Houston
Houston, TX 77204-5934



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