1. Reactivity of benzene oxide (BO), a reactive metabolite of benzene, was studied in model reactions with biologically relevant S- and N-nucleophiles by LC-ESI-MS. 2. Reaction with N-acetylcysteine (NAC) in aqueous buffer solutions gave N-acetyl-S-(6-hydroxycyclohexa-2,4-dien-1-yl)cysteine (pre-phenylmercapturic acid, PPhMA), which was easily dehydrated in acidic solutions to phenylmercapturic acid (PhMA). The yield of PPhMA + PhMA increased exponentially with pH up to 11% in the pH range from 5.5 to 11.4. 3. Primary 6-hydroxycyclohexa-2,4-dien-1-yl (HC) adducts were detected also in reactions of purine nucleosides and nucleotides under physiological conditions. After a vigorous acidic hydrolysis, all HC adducts were converted to corresponding phenyl purines, which were identified as 7-phenylguanine (7-PhG), 3-phenyladenine (3-PhA) and N(6)-phenyladenine (6-PhA). The yield of 7-PhG amounted to 14 ± 5 and 16 ± 7 ppm for 2'-deoxyguanosine and 2'-deoxyguanosine-5'-monophosphate, respectively, that of 6-PhA was 500 ± 70 and 455 ± 75 ppm with 2'-deoxyadenosine and 2'-deoxyadenosine-5'-phosphate, respectively, with only traces of 3-PhA. 4. Reactions with the DNA followed by acidic hydrolysis yielded 26 ± 11 ppm (mean ± SD; n = 9) of 7-PhG as the sole adduct detected. 5. In contrast to the reactions with S-nucleophiles, the reactivity of BO with nucleophilic sites in the DNA is very low and can therefore hardly account for a significant DNA damage caused by benzene.
- MeSH
- acetylcystein analogy a deriváty chemie metabolismus MeSH
- adenosinmonofosfát metabolismus MeSH
- adukty DNA chemie metabolismus MeSH
- benzen metabolismus MeSH
- cyklohexany chemie metabolismus MeSH
- deoxyadenosiny metabolismus MeSH
- deoxyguaninnukleotidy metabolismus MeSH
- deoxyguanosin metabolismus MeSH
- DNA chemie metabolismus MeSH
- hmotnostní spektrometrie s elektrosprejovou ionizací MeSH
- roztoky MeSH
- skot MeSH
- teplota MeSH
- zvířata MeSH
- Check Tag
- skot MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Styrene 7,8-oxide, which reacts preferentially at the N-7 position of guanine, yielded two pairs of diastereomers 7-(1'-hydroxy-2'-phenylethyl)-dGMP (the alpha-isomer) and 7-(2-hydroxy-2-phenylethyl)-dGMP (the beta-isomer) on reaction with deoxyguanosine-3'-monophosphate (3'-dGMP). The alpha- and beta-isomers were formed in the ratio 32:68. T4 polynucleotide kinase preferentially mediated labelling of diastereomers corresponding to the beta-isomer. The beta-diastereomers showed a labelling efficiency of 52%, whereas the alpha-isomers showed a labelling efficiency of 4%. Molecular modelling experiments showed intrinsic differences between the two isomers. The torsion angles of C8-N7-2'-Ar and C8-N7-2'-1' for the alpha-isomers were 149.9 degrees and -26.4 degrees, whereas the torsion angles of C-8-N7-1'-2' and N7-1'-2'-Ar for the beta-isomers were 105.3 degrees and 179.4 degrees. The consequent interatomic distance between one of the hydrogens on the alpha-carbon and the 3'-phosphate group on the sugar residue was 5.3 A in the alpha-isomer whereas the closest distance between the hydrogens attached to the alpha-carbon and 3'-phosphate group in the beta-isomer was 6.2 A. This arrangement probably leads to steric overcrowding at the 3'-phosphate group in alpha-isomers and these are less efficiently phosphorylated than beta-isomers. In in vitro styrene oxide-modified salmon testis DNA alpha- and beta-isomers of 7-alkylguanines were formed in the ratio 37:63. The recovery of two diastereomeric beta-isomers in a 32P-postlabelling assay was 14%, but one of the diastereomers was obtained in 3-fold greater yield than the second isomer.
- MeSH
- chemické modely MeSH
- deoxyguaninnukleotidy metabolismus MeSH
- DNA metabolismus MeSH
- epoxidové sloučeniny metabolismus MeSH
- fosforylace MeSH
- karcinogeny metabolismus MeSH
- radioizotopy fosforu MeSH
- stereoizomerie MeSH
- vysokoúčinná kapalinová chromatografie MeSH
- zvířata MeSH
- Check Tag
- mužské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- práce podpořená grantem MeSH
The reaction of 3,4-epoxy-1-butene (BMO) with deoxyguanosine-3'-monophosphate (3'-dGMP) resulted in the formation of two pairs of diastereomeric 7-alkyl-3'-dGMP derivatives corresponding to two isomers C?-1 and C?-2. The T4 polynucleotide kinase-mediated phosphorylation with [gamma-32P]-ATP showed preferential labelling of diastereo- mers of the C?-1 isomer. The diastereomers 1 and 2 of the C?-1 isomer had labelling efficiencies of 42%. However, the labelling efficiencies of diastereomers 3 and 4 of the C?-2 isomer were 11 and 10%, respectively. The 32P-postlabelling of BMO-modified DNA yielded four isomers in the ratio of 4:4:1:1 with overall recoveries being 14%. The two isomers had a half-life of 270 min (C?-1 isomer) and 300 min (C?-2 isomer) which is in accordance with the stability predicted by other similar adduct experiments. The molecular modelling experiments showed more pronounced restricted rotation of butadiene residue in C?-2 isomers due to steric interaction between butadiene residue at N-7 and O(6) atom of guanine than in C?-1 isomer. The butadiene residue also leads to steric overcrowding at 3'-phosphate in C?-2 isomer which probably restricts the access to the active site of T4 polynucleotide kinase.
- MeSH
- adukty DNA analýza biosyntéza izolace a purifikace MeSH
- deoxyguaninnukleotidy izolace a purifikace metabolismus MeSH
- DNA metabolismus účinky léků MeSH
- epoxidové sloučeniny farmakologie metabolismus MeSH
- fosforylace MeSH
- izotopové značení MeSH
- losos MeSH
- molekulární modely MeSH
- mutageny farmakologie izolace a purifikace metabolismus MeSH
- poločas MeSH
- polynukleotid-5'-hydroxylkinasa metabolismus MeSH
- radioizotopy fosforu MeSH
- stereoizomerie MeSH
- vazebná místa MeSH
- zvířata MeSH
- Check Tag
- mužské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- práce podpořená grantem MeSH
