Preparation of plasmid samples.

<p>Lane M: 1 kb ladder DNA marker. Lane 1: S, supercoiled plasmid sample. Lane 2: L, linear plasmid sample (SspI treated). Lane 3: N, nicked-circular plasmid sample (Nt.BspQI treated). Lane 4: C, closed-circular plasmid sample (topoisomerase I treated). Lane 5: S-LB, supercoiled plasmid treated with SspI reaction buffer. Lane 6: S-NB, supercoiled plasmid treated with Nt.BspQI reaction buffer. Lane 7: S-CB, supercoiled plasmid treated with topoisomerase I reaction buffer.