Figure 4.

Effect of borate concentration on the purity of single-nucleotide incorporation by TdT. Each of rNTP and modified rNTP was inserted to at the 3′-end of F-20dN initiator by TdT reaction in the Tris buffer (20 mM, pH 8.0) containing various concentration of borate ion (0–200 mM). The reaction products were separated on denaturing PAGE in a 12% gel (with 7 M urea) and quantified by analyzing the intensity of FAM dye, which was labeled on the 5′-end initiator. The purity was obtained by measuring the ratio of single- per multi-incorporated ODN product.