Figure 4.

A: Effect of temperature on DSN activity. Calf thymus high-molecular-weight DNA (50 μg/ml) was dissolved in 50 mM Tris-HCl, pH 7.15 containing 5 mM MgCl₂ and incubated with DSN (1 units/ml) for 2 min at different temperatures. B: Dependence of DSN activity on pH. Calf thymus high-molecular-weight DNA (50 μg/ml) was dissolved in 50 mM buffer containing 5 mM MgCl₂. The pH was adjusted to the desired pH using glycine-HCl, sodium acetate, MES-NaOH, Tris-HCl and sodium borate buffers. The sample was equilibrated at 25°C and activity was measured using the Kunitz method.