DMSO in PCR rxns ??

Matthias Zeiner mzei at
Mon Mar 13 07:53:45 EST 1995

On Fri, 10 Mar 1995 18:15:57 -0500, jie li wrote:

>> This is, in my experience, especially true for GC-rich templates, ie >75% 
>> GC. DMSO seems to lower the Tm of DNA, but this also means that one might 
>> have to adjust the annealing temperature. Also, specificity of the PCR can 
>> be enhanced, for obvious reasons.

>Please explain further the obvious reasons.  They are still quite obscure
>to me.  Sorry!
>                                                         Jie li U of PENN

I'm sorry I didn't make that clear.
Adding a Tm-lowering compound (DMSO may be such a compound) to a PCR rxn 
can result in 2 effects: Denaturing of the template DNA is more efficient 
and conditions for subsequent primer annealing are more stringent. 
Stringent annealing conditions can enhance specificity. 
Both effects are beneficial for GC rich templates and primers which tend 
to be somewhat sticky. 
Since it's known that DMSO inhibits Taq pol., it's a good idea to ad an 
extra unit of Taq to the reaction. Also, the annealing step might be 
extendet to about 1 min.

Matthias Zeiner

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