Extended Data Fig. 1: Validation of our supercoiling generation assay.
To confirm the handedness of supercoiling, we introduced Topoisomerase I from E. coli, which only relaxes negative supercoils, to our DNA molecules on the surface that were generated to have positive/negative supercoils via SxO intercalation reaction. For negative supercoils, all the DNA molecules relaxed within 5 minutes of incubation with Topo1, while in the case of positive supercoils, the amount of supercoiled molecules only decreased by 25. Since, independent of Topo1, DNA molecules can be also nicked by exposure of excitation laser (which would resolve the supercoiling), the actual fraction of positive supercoiled DNA in our assay should be well above 75%. These data confirm the handedness of the supercoiling generated via SxO intercalation.
