Magnesium Chloride

Magnesium chloride (MgCl2) is a soluble compound and a necessary reagent in PCR-based experiments. Magnesium ions bind dNTPs; thus optimal MgCl2 concentration will depend on the amount of dNTPs. DNA polymerase also requires free magnesium as a cofactor. For a standard reaction with Taq polymerase, a working MgCl2 concentration of 1.5 to 2.0 mM is typically used. Excessive magnesium stabilizes DNA double-strand formation, but can also promote primer annealing to incorrect template sites, leading to the formation of incorrect products. Inadequate magnesium will result in reduced yield. Magnesium chloride can come supplied as a pure powder or in solution.