PCR buffer with Tris-HCl and Ammonium sulfate (4:1)-does it exist?

[Duncan Clark]

Historians believe that in newspost 
<6b414df1.0402050504.3a95d575 at posting.google.com> on Thu, 5 Feb 2004, 
Elisabet W <elisabet.witso at chello.no> penned the following literary 
masterpiece:
>Can you by a PCR buffer which contains Ammonium sulfate together with
>Tris-HCL (pH 8.5), when the consentration is 4:1?



I would not advise using a PCR buffer with more than 20mM AmmSO4 in the 
1x mix so that would give a Tris of only 5mM.  IMHO, that is 
insufficient buffering capacity and I would not run below 10mM Tris.

I have seen and used a variety of buffers from 10mM Tris + 20mM AmmSO4 
up to 75mM Tris + 20mM AmmSO4. pH from 8.3 to 9.0

>
>Or do I have to make these reagents by myself?

Straight forward. Trizma preset from Sigma plus AmmSO4. Autoclave at no 
more than a 10x stock with or without Mg. If using high Tris plus 
AmmSO4, beware of pptation over time in the buffer. It will re-dissolve 
when heated but can be disconcerting when one's previously clear buffer 
turns cloudy.

Duncan
-- 
I love deadlines. I especially like the whooshing noise they make as
they go flying by.

Duncan Clark
GeneSys Ltd.