Figure 5.

Electrophoretic resolution of purified topoisomers. Closed circular pUC19 DNA was relaxed with Escherichia coli topoisomerase I and resolved into constituent toposiomers by preparative electrophoresis, as described in ‘Materials and Methods’ section. Here individual topoisomers are shown resolved on a 1.4% agarose gel, stained with ethidium bromide and photographed with UV transillumination. The gel lanes are labeled S (source DNA prior to purification), and with linkage differences with respect to relaxed DNA (0 to −6). The positions of bands containing relaxed circular DNA (N) and closed circular DNA (CC) are indicated in the left margin.