Quick PCR ques.

Alex Dobrovic adobrovic at medicine.adelaide.edu.au
Wed Aug 13 19:27:08 EST 1997

From: dcarpio at mail1.sas.upenn.edu (David Carpio)

>I'm having a few problems with my PCR protocol, and I've heard that
>having *too many* dNTPs can inhibit the reaction.  I was wondering what the
>reason for that would be.
>Any thoughts?

dNTPs bind Magnesium stoiochiometrically. Taq polymerase needs free Mg++ as
a cofactor. Typically with 0.m8M dNTPs and 1.5 mM, there is 0.7mM free
Mg++. (actually a bit less as the DNA binds some too). If you were to
double the dNTPs, there would be no free Mg++.

Alexander Dobrovic, Ph. D.
Chief Scientist
Department of Haematology-Oncology
The Queen Elizabeth Hospital, Woodville, SA 5011, Australia

Affiliate Senior Lecturer
Department of Medicine, University of Adelaide

Tel 61-8-8222 6884 Fax 61-8-8222 6046

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