title: Unwinding of supercoiled Col E1-DNA after covalent binding of the ultimate carcinogen N-acetoxy-N-2-acetylaminofluorene and its 7-iodo derivative.
abstract: The unwinding of superhelical Col E1-DNA was studied by means of gel electrophoresis and electron microscopy after covalent binding of N-acetoxy-N-2-[14C]acetylaminofluorene (N-Aco-[14C]AAF) and its 7-iodo derivative (N-Aco-[14C]AAIF). Studies with both compounds indicated that complete unwinding of the supercoiled DNA required the binding of hydrocarbon residue to about 3% of the bases. Thus the unwinding angle per residue of N-2-acetylaminofluorene (AAF) and its 7-iodo derivative was of 22 degrees +/- 3 and 18 degrees +/- 3 respectively. Our results are in good agreement with those obtained by Drinkwater et al. [9]. Precedent studies from this laboratory have shown that N-Aco-AAF and its 7-iodo derivative induce different local conformation change in native DNA (insertion-denaturation model and outside binding model respectively). The unexpected ability of the 7-iodo derivative to unwind supercoiled DNA is discussed.
mesh_terms: D015073:2-Acetylaminofluorene / Q000031:analogs & derivatives*; D000099:Acetoxyacetylaminofluorene / Q000031:analogs & derivatives* / Q000494:pharmacology*; D055598:Chemical Phenomena; D002621:Chemistry; D004278:DNA, Superhelical / Q000032:analysis* / Q000494:pharmacology; D004587:Electrophoresis, Agar Gel; D008854:Microscopy, Electron
chemical_list: D004278:DNA, Superhelical; C022917:N-acetoxy-N-2-acetylamino-7-iodofluorene; D000099:Acetoxyacetylaminofluorene; D015073:2-Acetylaminofluorene