Photochemically catalyzed generation of site-specific 8-nitroguanine adducts in DNA by the reaction of long-lived neutral guanine radicals with nitrogen dioxide.
A novel photochemical approach is described for synthesizing site-specific 8-nitro-2'-deoxyguanosine (8-nitro-dG) adducts DNA. The method is based on the bimolecular reaction of a neutral, deprotonated guanine radical [G(-H)*] in DNA and nitrogen dioxide (*NO(2)) radicals. This approach is illustrated using the single-stranded oligodeoxyribonucleotide 5'-d(CCATCGCTACC) dissolved in an aqueous solution of nitrite and bicarbonate anions at pH 7.5. The photochemical synthesis was triggered by the selective photodissociation of persulfate anions to yield SO(4)(*-) radical anions by either 308 nm XeCl excimer laser pulses or by a continuous irradiation with 290-340 nm light from a 1000 W Xe lamp. The sulfate radicals formed generate the CO(3)(*-) and *NO(2) radicals by one-electron oxidation of the bicarbonate and nitrite anions. In turn, the CO(3)(*-) radicals site-selectively generate G(-H)* radicals in DNA that combine with *NO(2) to form 8-nitro-dG lesions in the oligonucleotide. The nitrated oligonucleotides were purified by reversed-phase HPLC techniques and are stable at 4 degrees C for at least 4 days, but depurinate at ambient temperatures of 23 degrees C at pH 7 with a half-life of approximately 20 h. The nature of the reaction and decomposition products were studied by a combination of ESI and MALDI-TOF mass spectrometric techniques.
Shafirovich
Vladimir
V
Chemistry Department and Radiation and Solid State Laboratory, 31 Washington Place, New York University, New York, New York 10003-5180, USA. vs5@nyu.edu
Mock
Steven
S
Kolbanovskiy
Alexander
A
Geacintov
Nicholas E
NE
D018736:DNA Adducts / Q000032:analysis / Q000138:chemical synthesis*; D004277:DNA, Single-Stranded / Q000737:chemistry; D005609:Free Radicals / Q000737:chemistry; D006147:Guanine / Q000031:analogs & derivatives* / Q000737:chemistry*; D016297:Mutagenesis, Site-Directed; D009585:Nitrogen Dioxide / Q000737:chemistry*; D010777:Photochemistry; D021241:Spectrometry, Mass, Electrospray Ionization; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
C095838:8-nitroguanine; D018736:DNA Adducts; D004277:DNA, Single-Stranded; D005609:Free Radicals; D006147:Guanine; D009585:Nitrogen Dioxide