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. 1997 Mar 4;94(5):1692–1697. doi: 10.1073/pnas.94.5.1692

Figure 2.

Figure 2

Conversion of a nicked DNA trefoil to the positively supercoiled form yields doublets of topoisomers of different linking numbers upon agarose gel electrophoresis. Lanes 1 and 2, trefoil produced by cyclization of a 5.6-kb linear pCC56cos DNA in the presence of 7.5 mM (lane 1) or 75 mM (lane 2) magnesium glutamate. Lane 3, trefoil produced by the addition of AMPPNP to mixtures containing nicked pCC56cos DNA and a 10-fold molar excess of S. cerevisiae DNA topoisomerase II; the reaction medium contained 7.5 mM magnesium glutamate. nc, nicked circle; n3, nicked trefoil; lin, linear DNA.