Fig. 2.

Agarose gel electrophoresis of YOYO-I-labeled pPIC9K〈TRL5〉 DNA samples containing an initial mixture of supercoiled (S) and relaxed circular (RC) species (A), a relaxed circular form produced by treatment with topoisomerase I (B), and a nicked circular form (C). The staining level was varied as follows (in base pairs per dye molecule): lane a, unlabeled DNA; lane b, 500:1; lane c, 50:1; lane d, 5:1; lane e, 1:2; lane f, 1:20; lane g, 1:200; lane h, 1:2,000. The samples were incubated in the dark for 2 h at 50°C to ensure homogeneous labeling. A 1% agarose gel was run using tris-acetate-EDTA buffer and poststained with ethidium bromide to make the bands uniformly visible.