title: The facile generation of covalently closed, circular DNAs with defined negative superhelical densities.
mesh_terms: D001665:Binding Sites; D004264:DNA Topoisomerases, Type I; D004278:DNA, Superhelical / Q000032:analysis*; D003720:Densitometry; D004996:Ethidium; D013050:Spectrometry, Fluorescence
chemical_list: D004278:DNA, Superhelical; D004264:DNA Topoisomerases, Type I; D004996:Ethidium