ABSTRACT
Another problem arises when determining PCR products with mass spectrometry, namely that the commonly used DNA-polymerase enzyme Taq can transfer a nontemplated adenine nucleotide dA to the 3' end of the PCR products because of its terminal deoxynucleotidyl transferase activity [60]. This causes the PCR products to have a nonuniform molecular weight and complicates the interpretation of the MS data. A solution to this problem was found by incorporating an EcoRI recognition site in the PCR primers [45-47]. Upon digestion of the PCR products with EcoRI, products of uniform molecular weight were obtained. This is a complication in the analysis and an additional time loss. A better solution was found by Muddiman et al. [12]. They used the DNA polymerase from Pyrococcus furiosus (Pfu), which does not incorporate a nontemplated adenine nucleotide (Fig. 7). Using Pfu, no additional digestion was necessary.
