FIG. 4.

Supercoiling of pUC19 plasmids bearing hybrid gyrase sites. Relaxed pUC19 constructs (10 nM) were incubated at 37°C for 30 min with increasing concentrations of DNA gyrase, with the enzyme concentration (in nanometers) shown above each lane. Samples were resolved on 1% agarose gels containing 40-μg/ml chloroquine. R, relaxed substrate; NC, nicked circular DNA; S, negatively supercoiled product.