The Effect of Dimethyl Sulfoxide on Supercoiled DNA Relaxation Catalyzed by Type I Topoisomerases

Figure 1

The enhancement of relaxation efficiency of EcTopo I caused by DMSO. (a) Electrophoretic analysis of relaxation products catalyzed by EcTopo I in the presence or absence of 10% (v/v) DMSO. Lane 1: untreated pBR322 plasmid. Lanes 2 to 6: EcTopo I catalyzed relaxation products obtained by incubation of 0.2 μg (Lane 2), 0.4 μg (Lane 3), 0.6 μg (Lane 4), 0.8 μg (Lane 5), and 1.0 μg (Lane 6) pBR322 plasmid in the presence of 10% (v/v) DMSO. Lane 7: the mixture of 1.0 μg pBR322 with 10% (v/v) DMSO. Lanes 8 to 12: EcTopo I catalyzed relaxation products obtained by incubation of 0.2 μg (Lane 2), 0.4 μg (Lane 3), 0.6 μg (Lane 4), 0.8 μg (Lane 5), and 1.0 μg (Lane 6) pBR322 plasmid in the absence of 10% (v/v) DMSO. (b) Correlations between the amount of pBR322 substrate and ratio of relaxed plasmid in the presence (red) and absence (blue) of 10% (v/v) DMSO. (c) Electrophoretic analysis of relaxation products catalyzed by EcTopo I with different concentrations of DMSO. Lane 1: untreated pBR322 plasmid. Lanes 2 to 8: EcTopo I catalyzed relaxation products obtained by incubating 1.0 μg pBR322 plasmid with the concentrations of DMSO of 0% (Lane 2; no DMSO is added), 5% (Lane 3), 10% (Lane 4), 15% (Lane 5), 20% (Lane 6), 25% (Lane 7), and 30% (Lane 8). Lane 9: the mixture of 1.0 μg pBR322 with 20% (v/v). (d) Mutual relations between concentration of DMSO in solution (v/v) and ratio of relaxed pBR322 plasmid.

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