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. Author manuscript; available in PMC: 2013 Jul 15.
Published in final edited form as: Bioorg Med Chem. 2012 May 19;20(14):4489–4494. doi: 10.1016/j.bmc.2012.05.030

Figure 3.

Figure 3

Impact of CPT-epipodophyllotoxin conjugates on topoisomerase I cleavage activity. (A). Schematic diagram of the cleavage assay. (B). [γ32P]-ATP-labeled ON4/ON5 was incubated with topoisomerase I and indicated compounds (25 µM) at 37 °C for 15 min. Covalent-linked topoisomerase I was digested by proteinase K and the cleavage products (containing topoisomerase I amino acid residues on the 3′ end of the cleaved strand) were separated by 20% denaturing urea/polyacrylamide gel electrophoresis.