Magnesium effects on PCR

Stephen Marcus Lane smlane at
Fri Feb 9 10:03:05 EST 1996

Dubear Kroening (dubear at offroad) wrote:

" Does anyone know of any detailed studies on the effects of magnesium 
" on PCR?  I've searched the web, PCR books, and medline but cannot find 
" enough info.  For instance, what exactly Mg does, what concentrations 
" are better for certain size products and why they vary, whether there 
" is a range one can use if trying to amplify different size products, 
" etc...   Any info would be greatly appreciated.

This is speculation on my part... but [Mg++] is a critical factor
in the 3D structure of single-stranded oligonucleotides; it
basically determines how tight the oligo folds and hence what its
structure is.  So every different set of template and primers
will have a different optimum [Mg++], where the single-stranded
species are folded to the best extent to be substrates for
the polymerase.

Another bit of data: my PCR reaction has a small template: 152 bp.
The primers are 18 and 34 bp.  The optimum [Mg++] is 2.5 mM,
although I get measurable (bands on an agarose gel) activity
from 1 - 10 mM.
-- Steve Lane <steve at> ------------------------------- 
-------------- a net.god^0.5 of NAZZUSOASH  ------------------

More information about the Methods mailing list