Why use K+ and NH4+ in Taq buffer?

chovek69 via methods%40net.bio.net (by ivanoov from gmail.com)
Tue Apr 8 04:28:50 EST 2008


On Apr 3, 2:02 am, WS <novalidaddr... from nurfuerspam.de> wrote:
> Dear SiLin,
>
> total ionic strength doesn't differ so much. It's most likely due to
> patent and other legal issues and/or due to the composition of the Taq
> storage buffer that the PCR buffers differ in composition. Seems that
> in real life these differences do not affect Taq  much but of course
> require you to optimise a PCR for each polymerase/buffer composition.
> (another way nasty companies annoy scientists to stay with their
> products).
>
> Furthermore, (that's my personal explanation for the ammonium salts)
> some Taqs are hot start and reversibly blocked (by imino group
> formation with eg lysines) with formaldehyde (btw, thats how some
> people make their homebrew hot start Taq, too). This formaldehyde -
> once liberated by heat- can be caught by the excess of ammonium ions
> and thus won't afftect the Taq anymore.
>
> Best regards,
>
> Wo

Hi,

Check the bible
http://info.med.yale.edu/genetics/ward/tavi/p06.html
http://info.med.yale.edu/genetics/ward/tavi/p07.html
check also the references

From my own experience I can say that KCl-based buffers are far
superior than (NH4)2SO4-based ones in terms of PCR sensitivity, and
specificity (maybe because the latter ones require far more Mg2+ which
leads to unspecific amplifications)


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