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

Figure 5

The enhancement of reaction efficiency of T7 endonuclease I caused by DMSO. S: supercoiled plasmid; L: linear DNA; N: nicked plasmid. (a) Electrophoretic analysis of products catalyzed by T7 endonuclease I in the absence of DMSO. Lane 1: untreated pBR322 plasmid. Lanes 2 to 6: T7 endonuclease I catalyzed reaction products obtained by incubating negatively supercoiled pBR322 with T7 endonuclease I at 37°C for 5 min (Lane 2), 10 min (Lane 3), 15 min (Lane 4), 30 min (Lane 5), and 60 min (Lane 6). (b) Electrophoretic analysis of products catalyzed by T7 endonuclease I in the presence of DMSO. T7 endonuclease I catalyzed reaction products obtained by incubating 1.0 μg pBR322 plasmid with the concentrations of DMSO of 5% (Lane 2), 10% (Lane 3), 15% (Lane 4), and 20% (Lane 5) at 37°C for 10 min.

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