Ammonium or Potassium Acetate?

Dr. Hiranya S. Roychowdhury hroychow at nmsu.edu
Sat Feb 4 13:36:44 EST 2006


The both Amm-Ac and K-Ac does do the job fine.  Ammonium is to be avoided if 
you are using the DNA for ligation, since Ammonium ions seem to interfere with 
the reaction.  

The reason KOAc produces a big "precipitate" from the alk lysis buffers is the 
fact that potassium salt of dodecylsulfate is insoluble in water.  When you 
add KOAc to ppt the NA, the Na-DS is converted to K-DS.  

Quoting Wolfgang Schechinger <novalidaddress at nurfuerspam.de>:

> Dear JW
> Just checked sial.com for ammonium dodecyl sulfate. It's sold as a 30%
> aqueous solution. So it seems to be quite soluble and seems to me being
> not so much suited for the precipitation of proteins and geomic DNA.
> I also compared the precipitate formation of 3M KoAc vs 3M NH4OAc, bot
> pH 5,2 with HOAc with 0.1M NaOH / 1% SDS (the alkaline lysis solution).
> 
> No ppt at all with the NH4OAc, KOAc made lotsa snow like a charm.
> 
> Is there maybe a particular role of the Ammonium ions?
> 
> Wolfgang
> 
> PS please reply to the group, emails to this address will be delivered
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> 
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-- 
Hiranya S. Roychowdhury, Ph.D.
Asst. Professor,
Dept. of Health and Public Services
Dona Ana Branch Community College
Rm# 191T, 
New Mexico State University
Las Cruces, NM 88003



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