Figure 4.

Addressed cleavage by scPvuII-_C12-TFO in the presence of a 1400-fold excess of unaddressed PvuII sites over addressed PvuII. 0.16 nM scPvuII-_C12-TFO, 0.18 nM plasmid DNA with a single addressed PvuII site and 3 PvuII sites and 17 nM λ-DNA with 15 PvuII sites were preincubated in the absence of Mg²⁺; cleavage was initiated by addition of MgCl₂ (final concentrations: 2.5 mM MgCl₂ and 100 mM NaCl). The reaction products obtained after the times indicated were analyzed by agarose gel electrophoresis. The gel on the left shows the result of the control experiment (cleavage without preincubation): a typical PvuII cleavage pattern of bacteriophage λ-DNA is seen. The gel on the right shows the result of the cleavage pattern after preincubation: only the cleavage of plasmid DNA is observed, however not cleavage of bacteriophage λ-DNA.