This kit contains reagents for routine detection of Top1 activity. DNA markers (included) allow unequivocal detection of the enzyme. The assay is specific for topoisomerase I; (eukaryotic type II topoisomerases require MgCl2 and ATP). The standard topo I assay kit is supplied with EDTA containing reaction buffer (minus Mg++) in order to prevent nucleolytic nicking of the supercoiled substrate (although we note that some eukaryotic type I activities are stimulated by Mg++). This assay will work even with crude extracts. A detailed manual of instruction (see link above) is included that describes how to run the gels to maximally resolve topoisomers for analysis of DNA unwinding.