Search results for "Pyrenes"
showing 10 items of 65 documents
Prevention of benzo(a)pyrene-induced mutagenicity by homogeneous epoxide hydratase
1976
Benzo(a)pyrene and benz(a)anthrancene which, in contrast to the K-region epoxides benzo(a)pyrene 4,5-oxide and benz(a)anthracene 5,6-oxide, are not mutagenic to Salmonella typhimurium TA 1537 in the absence of mammalian enzyme preparations, were activated by liver microsomes from C3H mice, which had not received any pretreatment, to mutagens reverting this tester strain to histidine prototrophy. Addition of epoxide hydratase inhibitors greatly increased this mutagenicity and addition of pure epoxide hydratase reduced it by more than 95% down to the range of spontaneous mutations as observed in absence of any added mutagen. This demonstrates that the metabolic pathway responsible for the mut…
The influence of automobile exhausts on mutagenicity of soils: contamination with, fractionation, separation, and preliminary identification of mutag…
2000
To test the assumption that automobile exhausts contribute to soil mutagenicity, two soils with low levels of mutagenic activities were exposed to traffic exhausts at a heavily charged junction of German motorways (Autobahnen) for 3, 7, 10, 13, 17, 21, and 26 weeks. Indeed, in the presence of a metabolic activation system from rat liver (S9), an average increase of 8 and 9 (4 and 12) revertants per gram per week was found in Salmonella typhimurium TA 98 (TA 100). In the absence of S9, meaningful measurements were impossible on account of a concurrent dose dependent increase of toxicity. No correlation between the increase of mutagenicity and the contents of polycyclic aromatic hydrocarbons …
Sulfotransferase-mediated activation of mutagens studied using heterologous expression systems
1998
Abstract Sulfation is a common final step in the biotransformation of xenobiotics and is traditionally associated with inactivation. However, the sulfate group is electron-withdrawing and may be cleaved off heterolytically in some molecules leading to electrophilic cations which may form adducts with DNA and other important cellular structures. Since endogenous sulfotransferases do not appear to be expressed in indicator cells of standard mutagenicity tests, rat and human sulfotransferases have been stably expressed in his−Salmonella typhimurium strain TA1538 and Chinese hamster V79 cells. Using these recombinant indicator cells, sulfotransferase-dependent genotoxic activities were detected…
Inhibition of the mutagenicity of 2-nitrofluorene, 3-nitrofluoranthene and 1-nitropyrene by vitamins, porphyrins and related compounds, and vegetable…
1997
When 21 vitamins including related compounds haemin, chlorophyllin, chlorophyll, biliverdin and bilirubin, as well as juices from five fruits and 25 vegetables and solvent extracts from the residues of fruits and vegetables were tested for their antimutagenic potencies with respect to mutagenicity induced by 2-nitrofluorene (2-NF), 3-nitrofluoranthene (3-NFA) and 1-nitropyrene(1-NP) in Salmonella typhimurium TA98 the following results were obtained. The tetracyclic nitroarenes 3-NFA and 1-NP were in general more effectively antagonized by potent antimutagenic compounds than the tricyclic 2-NF. beta-Carotene, retinol, retinal, retinoic acid, retinol palmitate, riboflavin 5'-phosphate, alpha-…
Inhibition of the mutagenicity of 2-nitrofluorene, 3-nitrofluoranthene and 1-nitropyrene by flavonoids, coumarins, quinones and other phenolic compou…
1997
When 56 flavonoids, 32 coumarins, five naphthoquinones, 12 anthraquinones and five structurally-related compounds were tested for their antimutagenic potencies with respect to mutagenicities induced by 2-nitrofluorene (2-NF), 3-nitrofluoranthene (3-NFA) and 1-nitropyrene (1-NP) in Salmonella typhimurium TA98 distinct structure-activity relationships were detected. First, the tetracyclic nitroarenes 3-NFA and 1-NP were in general more effectively antagonized by potent antimutagenic flavonoids and coumarins than the tricyclic 2-NF, while there were only minor differences with quinones. Secondly, antimutagenicity of natural compounds of plant origin correlated with the aglyconic nature 10 of a…
Dual role of epoxide hydratase in both activation and inactivation of benzo(a)pyrene.
1977
The effect of epoxide hydratase upon the mutagenicity of benzo(a)pyrene was investigated using two Salmonella typhimurium strains (TA 1537 and TA 98). These two bacterial strains were found to differ characteristically in their susceptibility to different mutagens biologically produced from benzo(a)pyrene providing a diagnostic tool to investigate which types of mutagenic metabolites were produced in various metabolic situations. The results showed that the pattern of mutagenic metabolites produced by microsomes from methylcholanthrene-treated mice was very different from that produced by microsomes from phenobarbital-treated or untreated mice. However in all cases at least two mutagenic me…
Metabolic activation of dibenzo[a,l]pyrene by human cytochrome P450 1A1 and P450 1B1 expressed in V79 Chinese hamster cells.
1999
Metabolic activation of the strongly carcinogenic polycyclic aromatic hydrocarbon (PAH) dibenzo[a,l]pyrene (DB[a,l]P) and its trans-8,9-dihydrodiol (trans-8,9-diol) catalyzed by human cytochromes P450 (P450) 1A1 and 1B1 was investigated. DNA binding of DB[a,l]P in mammalian cell lines has previously been shown to be preferentially mediated by fjord region DB[a,l]P-11,12-dihydrodiol 13,14-epoxides (DB[a,l]PDE). In order to elucidate different capabilities of both P450 enzymes for metabolic activation of DB[a, l]P V79 Chinese hamster cells, stably expressing human P450s 1A1 or 1B1 have been exposed to the parent PAH or its racemic trans-8, 9-diol. For this purpose, synthesis and spectroscopic…
Structure elucidation of the adducts formed by fjord region Dibenzo[a,l]pyrene-11,12-dihydrodiol 13,14-epoxides with deoxyguanosine.
1999
Model adducts to be used in the identification of biologically formed adducts were synthesized by reaction of fjord-region dibenzo[a,l]pyrene 11,12-dihydrodiol 13,14-epoxides (DB[a,l]PDE) and deoxyadenosine (dA). The (+/-)-anti-DB[a,l]PDE was reacted with dA in dimethylformamide at 100 degrees C for 30 min to give four DB[a, l]PDE-14-N(6)dA adducts: (-)-anti-trans (26%), (+)-anti-trans (26%), (-)-anti-cis (17%), and (+)-anti-cis (17%). The (+/-)-syn-DB[a,l]PDE was reacted with dA under the same conditions to yield four DB[a, l]PDE-14-N(6)dA adducts and one N7Ade adduct: (+)-syn-cis (19%), (+)-syn-trans (13%), (-)-syn-cis (19%), (-)-syn-trans (13%), and (+/-)-syn-DB[a,l]PDE-14-N7Ade (22%). T…
Sulfotransferase-mediated mutagenicity of 1-hydroxymethylpyrene and 4H-cyclopenta[def]chrysen-4-ol and its enhancement by chloride anions.
1993
1-Hydroxymethylpyrene (HMP), a primary benzylic alcohol, and 4H-cyclopenta[def]chrysen-4-ol (OH-CPC), a secondary benzylic alcohol, were investigated for mutagenicity in Salmonella typhimurium (reversion of the his- strain TA98) in the presence of various xenobiotic-metabolizing systems. In the direct test, HMP was inactive and OH-CPC was very weakly active. In the presence of NADPH-fortified postmitochondrial fraction from rat liver (S9/NADPH), no activation of OH-CPC was observed, whereas strong mutagenic effects were elicited by HMP. In the presence of cytosol and 3'-phosphoadenosine-5'-phosphosulfate (PAPS), both alcohols were activated to potent mutagens. For equal mutagenic effects, a…
Synthesis of Nonplanar Graphene Nanoribbon with Fjord Edges
2021
As a new family of semiconductors, graphene nanoribbons (GNRs), nanometer-wide strips of graphene, have appeared as promising candidates for next-generation nanoelectronics. Out-of-plane deformation of π-frames in GNRs brings further opportunities for optical and electronic property tuning. Here we demonstrate a novel fjord-edged GNR (FGNR) with a nonplanar geometry obtained by regioselective cyclodehydrogenation. Triphenanthro-fused teropyrene 1 and pentaphenanthro-fused quateropyrene 2 were synthesized as model compounds, and single-crystal X-ray analysis revealed their helically twisted conformations arising from the [5]helicene substructures. The structures and photophysical properties …