Camptothecin is a topo I poison that both inhibits enzyme activity and stabilizes formation of topo I cleavage complexes (Hsiang et al J. Biol. Chem. 260:14873-14878, 1985). TopoGEN provides this reagent as a control inhibitor/poison of topoisomerase I. For in vitro cleavage detection, we recommend that the drug be tested in the range 100 uM; however, cleavages are strongly influenced by the amount of topoisomerase in the reaction as well as the type of assay being employed (SDS-K+ vs. Radioactive End Labeled DNA vs. testing for plasmid nick- ing). Note that larger amounts of enzyme will be required to detect cleavage complex, compared to assays that measure catalytic activity. This is because cleavage assays are stoichiometric based assays that consume topo I.
Chemical Name: (S)-4-Ethyl-4,10-dihydroxy-1H-pyrano[3',4':6,7]indolizino-[1,2-b]quinoline-3,14(4H,12H)-dione
Molecular Formula: C20H16N2O4
Molecular Weight: 348.35
TG4110 contains lyophilized Camptothecin. Addition of 0.25 ml of solvent to dry drug (methanol or DMSO) will yield a working stock of 10 mM. In some cases, the drug is supplied already suspended in DMSO at 10 mM (0.25 ml) and is ready for use. The drug is pre-tested and shown to induce topo I cleavages using purified human Topoisomerase I from TopoGEN, Inc.
The dry product is shipped at ambient temperature; store the rehydrated stock at -20°C.