title: Conformations of poly(dG-dC).poly(dG-dC) modified by the O-acetyl derivative of the carcinogen 4-hydroxyaminoquinoline 1-oxide.
abstract: Poly(dG-dC).poly(dG-dC) has been modified by reaction with 4-acetoxyaminoquinoline 1-oxide (Ac-4 HAQO), the ultimate carcinogen of 4-nitroquinoline 1-oxide. The circular dichroism (CD) spectra of the modified and unmodified polymers have been compared under various experimental conditions. The CD spectra were recorded in 1 mM phosphate, 50% (v/v) ethanol, 3.8 M LiCl and 95% (v/v) ethanol, conditions in which poly(dG-dC).poly(dG-dC) adopts the B-, Z-, C- and A-form respectively. In 1 mM phosphate buffer, poly(dG-dC).poly(dG-dC) modified by Ac-4 HAQO seems not to contain regions in the Z-form. Z-form induction could be progressively obtained by the addition of ethanol as follows: in the buffer with about 30% ethanol the modified polymer started to adopt the Z structure, while 40% of ethanol in the buffer was necessary for the unmodified polymer. In the 50% ethanol-1 mM phosphate buffer mixture (v/v), poly(dG-dC).poly(dG-dC) was entirely in the Z-form while poly(dG-dC).poly(dG-dC) modified by Ac-4 HAQO remained partially in the B-form. Enzymatic digestions with the nuclease S1 which is specific of the single-stranded DNA were carried out in order to support the modified poly(dG-dC).poly(dG-dC) CD study conclusions. The role played by the two major adducts on the conformational characteristics of modified polymer is discussed.
mesh_terms: D000634:Aminoquinolines; D002273:Carcinogens; D002851:Chromatography, High Pressure Liquid; D002942:Circular Dichroism; D004720:Endonucleases / Q000378:metabolism; D007700:Kinetics; D009690:Nucleic Acid Conformation; D011089:Polydeoxyribonucleotides; D015719:Single-Strand Specific DNA and RNA Endonucleases; D013816:Thermodynamics
chemical_list: D000634:Aminoquinolines; D002273:Carcinogens; D011089:Polydeoxyribonucleotides; C019530:poly(dC-dG); C032982:4-acetoxyaminoquinoline 1-oxide; D004720:Endonucleases; D015719:Single-Strand Specific DNA and RNA Endonucleases