title: Conformational changes of poly(dG-dC) . poly(dG-dC) modified by the carcinogen N-acetoxy-N-acetyl-2-aminofluorene.
abstract: Poly (dG-dC) . poly(dG-dC) was modified by the reaction with N-acetoxy-N-acetyl-2-aminofluorene. The conformations of poly(dG-dC) . poly(dG-dC) and of poly d(G-C)AAF were studied by circular dichroism under various experimental conditions. In 95% ethanol, the two polynucleotides adopt the A-form. In 3.9 M LiCl, the transition B-form-C-form is observed with poly(dG-dC) . poly (dG-dC) but not with poly d(G-C)AAF. In 1 mM phosphate buffer, poly d(G-C)AAF behaves as a mixture of B- and Z-form, the relative percentages depending upon the amounts of modified bases. The percentage of Z-form is decreased by addition of EDTA and is increased by addition of Mg++. Spermine favors the Z-form in modified and unmodified polynucleotides. No defect in the double helix of poly d(G-C)AAF is detected by SI endonuclease.
mesh_terms: D015073:2-Acetylaminofluorene / Q000031:analogs & derivatives; D000099:Acetoxyacetylaminofluorene; D055598:Chemical Phenomena; D002621:Chemistry; D002942:Circular Dichroism; D008968:Molecular Conformation; D009994:Osmolar Concentration; D011089:Polydeoxyribonucleotides
chemical_list: D011089:Polydeoxyribonucleotides; C016681:poly(dG).poly(dC); D000099:Acetoxyacetylaminofluorene; D015073:2-Acetylaminofluorene