Figure 5.

Initial velocities (v) for the DNase I (A) and exonuclease I (B) hydrolysis reactions in the presence of 0% (w/v) (open circles), 5% (w/v) (closed circles), 10% (w/v) (closed triangles), 15% (w/v) (closed squares) and 20% (w/v) PEG (closed diamonds). The DNase I reaction was carried out in a buffer containing 100 mM NaCl, 5 mM MgCl₂ and 50 mM HEPES (pH 7.2) at 25°C in the absence or presence of PEG 4000. The exonuclease I reaction was carried out in a buffer containing 100 mM NaCl, 6.7 mM MgCl₂, 10 mM 2-mercaptoethanol and 67 mM glycine-KOH (pH 9.5) at 37°C in the absence or presence of PEG 8000. The dsDNA and ssDNA concentrations in kinetic assays were 0.1–20 μM for DNase I and 0.1–10 μM for exonuclease I. The value of v was plotted versus the concentration of substrate DNA. Error bars (smaller than ±1%) were omitted for clarity.