Figure 7.

HPLC analysis of products of early phase of poly(dG)–poly(dC) synthesis. Polymerase extension assay was performed as described in Materials and Methods, with 15 μM (dG)₁₀–(dC) ₁₀ and 2 μg/ml of Klenow exo⁻ at 37°C. The reaction was started by addition of the enzyme and was terminated by addition of 10 mM EDTA. Aliquots of 50 μl were withdrawn from the assay mixture before (continuous curve) and 5 min (dashed curve) after the reaction had been started. Oligonucleotides were separated from dGTP and dCTP with TSKgel G-3000 SWXL HPLC column (7.8 × 300 mm) and loaded in 0.1 M KOH onto TSKgel DNA-NPR column (4.6 × 75 mm) equilibrated with 0.1 M KOH. Elution was performed using a 30 min linear KCl gradient between 0 and 1 M in 0.1 M KOH at a flow rate of 0.6 ml/min. Elution of correspondent C- and G-strands are indicated in the figure.