title: Synthesis and spectroscopic characterization of site-specific 2-amino-1-methyl-6-phenylimidazo.
abstract: The aim of the present study is to determine the chemical structure and conformation of DNA adducts formed by incubation of the bioactive form of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), N-acetoxy-PhIP, with a single-stranded 11mer oligodeoxyribonucleotide. Using conditions optimized to give the C8-dG-PhIP adduct as the major product, sufficient material was synthesized for NMR solution structure determination. The NMR data indicate that in duplex DNA this adduct exists in equilibrium between two different conformational states. In the main conformer, the covalently bound PhIP molecule intercalates in the helix, whilst in the minor conformation the PhIP ligand is probably solvent exposed. In addition to the C8-dG-PhIP adduct, at least eight polar adducts are found after reaction of N-acetoxy-PhIP with the oligonucleotide. Three of these were purified for further characterization and shown to exhibit lowest energy UV absorption bands in the range 342-347 nm, confirming the presence of PhIP or PhIP derivative. Accurate mass determination of two of the polar adducts by negative ion MALDI-TOF MS revealed ions consistent with a spirobisguanidino-PhIP derivative and a ring-opened adduct. The third adduct, which has the same mass as the C8-dG-PhIP oligonucleotide adduct, may contain PhIP bound to the N2 position of guanine.
authors.affiliation: Biology and Biotechnology Research Program, Lawrence Livermore National Laboratory, Livermore, CA 94551, USA.
authors.forename: K
authors.initials: K
authors.lastname: Brown
authors.forename: E A
authors.initials: EA
authors.lastname: Guenther
authors.forename: K H
authors.initials: KH
authors.lastname: Dingley
authors.forename: M
authors.initials: M
authors.lastname: Cosman
authors.forename: C A
authors.initials: CA
authors.lastname: Harvey
authors.forename: S J
authors.initials: SJ
authors.lastname: Shields
authors.forename: K W
authors.initials: KW
authors.lastname: Turteltaub
mesh_terms: D001483:Base Sequence; D002851:Chromatography, High Pressure Liquid; D018736:DNA Adducts / Q000138:chemical synthesis* / Q000737:chemistry*; D003849:Deoxyguanosine / Q000031:analogs & derivatives* / Q000138:chemical synthesis* / Q000737:chemistry*; D007093:Imidazoles / Q000138:chemical synthesis* / Q000737:chemistry*; D019906:Nuclear Magnetic Resonance, Biomolecular; D009690:Nucleic Acid Conformation; D009838:Oligodeoxyribonucleotides / Q000138:chemical synthesis / Q000737:chemistry; D011725:Pyridines / Q000138:chemical synthesis / Q000737:chemistry; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: C096092:2-(acetoxyamino)-1-methyl-6-phenylimidazo(4,5-b)pyridine; D018736:DNA Adducts; D007093:Imidazoles; D009838:Oligodeoxyribonucleotides; D011725:Pyridines; C078255:N-(deoxyguanosin-8-yl)-2-amino-1-methyl-6-phenylimidazo(4,5-b)pyridine; D003849:Deoxyguanosine