Figure 3.

Two-dimensional gel electrophoresis of pA₅N₅i and pA₅N₁i topoisomers. Mixtures of topoisomers prepared by relaxation of native supercoiled plasmids with wheat-germ topoisomerase I in the presence of ethidium bromide were subjected to agarose gel electrophoresis. First-dimension electrophoresis in all cases was carried out in TBE buffer containing 50 mM NaCl for 11 h with buffer recirculation. (A) Second-dimension electrophoresis carried out in TBE buffer containing chloroquine phosphate (0.3 μg/ml). (B) Second-dimension electrophoresis carried out in TBE buffer containing chloroquine (4 μg/ml).