Inhibition of leinamycin DNA damage by using daunomycin intercalator. The 5'-32P-labeled DNA duplex 5'-GTT CGT ATA TGGGAGGTC GCA TGT G-3' (underlined portion of the sequence is double-stranded) was incubated with daunomycin, leinamycin and 2-mercaptoethanol at 25 °C for 23.25 h followed by Maxam-Gilbert workup and separation of the resulting fragments on a 20% denaturing polyacrylamide gel. Labeled fragments were visualized by phosphorimager analysis. Reactions were conducted in TNE buffer, pH 7.0 (Tris-HCl, 50 mM; NaCl, 150 mM, and EDTA, 1 mM). Lane 1, DNA with leinamycin (50 μM) alone; lane 2, DNA with of 2-mercaptoethanol (0.5 mM); lane 3, DNA and daunomycin (50 μM); lanes 4–16, all contained DNA, leinamycin (50 μM), and 2-mercaptoethanol (0.5 mM). Lanes 4–16 contained 0, 0.1, 0.5, 1, 2, 4, 6, 8, 10, 20, 30, 40, and 50 μM daunomycin respectively.