Modification of ColE1 DNA with osmium tetroxide generates positively supercoiled molecules.
Covalent binding of osmium tetroxide to negatively supercoiled DNA in vitro initially induces its relaxation, accompanied by a formation of a single denaturation "bubble" per molecule. Binding of further osmium results in DNA overwinding and the appearance of positive supercoils as demonstrated by gel electrophoresis and electron microscopy.
D004269:DNA, Bacterial / Q000187:drug effects* / Q000378:metabolism; D004270:DNA, Circular / Q000187:drug effects / Q000378:metabolism; D004278:DNA, Superhelical / Q000187:drug effects* / Q000378:metabolism; D004587:Electrophoresis, Agar Gel; D008854:Microscopy, Electron; D009992:Osmium / Q000494:pharmacology*; D009993:Osmium Tetroxide / Q000378:metabolism / Q000494:pharmacology*; D010957:Plasmids
D004269:DNA, Bacterial; D004270:DNA, Circular; D004278:DNA, Superhelical; D009992:Osmium; D009993:Osmium Tetroxide