FIG. 6.

(a) Time dependency of nuclease activity. pJuFo plasmid was incubated with a previously tested urine with excellent spike recovery (positive urine) and an inhibitory urine sample for different times (given in minutes) at room temperature. EcoRI/HindIII-digested lambda DNA was used as a marker (M1). (b) pH dependency of nuclease activity. pJuFo plasmid was incubated for 10 min at room temperature with an inhibitory urine which was adjusted to different pH values. The marker is a 1-kb ladder (M2). As a positive control (+), water instead of urine was spiked with plasmid. §, relaxed circular plasmid; §§, linearized plasmid; and §§§, supercoiled form of plasmid.