Search results for "Pyrene"
showing 10 items of 260 documents
Pyrene-functionalized nanoparticles: two independent sensors, the excimer and the monomer.
2012
The high surface-to-volume ratio of nanoparticles has been used to obtain a high local concentration of pyrene units on their periphery, making the formation of both pyrene emissive species possible using amazingly small pyrene concentrations. The sensing properties of model pyrene-functionalized nanoparticles was investigated by using different nitroaromatic compounds [m-nitroaniline and p-nitroaniline] and nitrobenzenes [nitrobenzene, p-nitrotoluene, 2,4-dinitrotoluene, and 2,6-dinitrotoluene]. The hybrid system acts as a dual-fluorescence sensor, in which the decrease of the pyrene emission, induced by the quencher, is hardly reflected in the pyrene excimer emission. The encapsulation ca…
Solubilisation of multi walled carbon nanotubes by alpha-pyrene functionalised PMMA and their liquid crystalline self-organisation.
2008
alpha-Pyrene functionalised poly(methyl methacrylate) (PMMA) chains were synthesised by RAFT polymerisation and found to be highly efficient to solubilise and disentangle multi walled carbon nanotubes that can now self-organise as liquid crystalline phases in PMMA and PEG 400 matrices.
Photoinduced toxicity of retene to Daphnia magna under enhanced UV-B radiation.
2001
Abstract The effects of UV radiation on the acute toxicity of retene (7-isopropyl-1-methylphenanthrene) to Daphnia magna Straus were studied. Dehydroabietic acid (DHAA) from which retene is formed in the vicinity of pulp and paper industry was also studied. Pyrene, anthracene, and phenanthrene were used as model PAH compounds. The time taken for immobilization (ET50) was monitored under biologically effective UV-B dose rates of 240, 365, 565, and 650 mW m−2 (UV-A and visible light also present). Median effective concentrations (EC50) were determined after a 15-min UV exposure (565 mW m−2) followed by 24 h in the dark. Retene ( 10–320 μg l −1 ) was not acutely toxic in the dark. The inductio…
The capacity of liver microsomes to form benzo[a]pyrene-diolepoxide-DNA adducts and induction of cytochrome P450 1A in feral fish exposed to pulp mil…
1996
An investigation was made of cytochrome P4501A (CYP1A) induction, determined by the activity of EROD (7-ethoxyresorufin O-deethylase), and formation of benzo[a]pyrene-diolepoxide-DNA (BPDE-DNA) adducts, measured by synchronous fluorescence spectrophotometry, in liver microsomes of perch (Perca fluviatilis), bream (Abramis brama), and roach (Rutilus rutilus). Fish were collected from the southern part of Lake Saimaa (Finland), an area polluted by effluents from the pulp and paper industry. In addition, two conjugation enzymes (UDP-glucuronosyltransferase and glutathione S-transferase) were determined. Overall, when compared to an upstream reference, EROD activity was higher in fish at waters…
Mono- and diglucuronide formation from benzo[a]pyrene and chrysene diphenols by AHH-1 cell-expressed UDP-glucuronosyltransferase UGT1A7
1999
Polycyclic aromatic hydrocarbon (PAH)-type compounds induce at least two rat UDP-glucuronosyltransferase isoforms, UGT1A6 and UGT1A7. Among the glucuronidation reactions of PAH metabolites studied, mono- and diglucuronide formation of benzo[a]pyrene and chrysene-3,6-diphenol showed the highest induction factors in rat liver microsomes. Availability of AHH-1 cells stably expressing UGT1A7 allowed us to study whether this PAH-inducible isoform could catalyze benzo[a]pyrene and chrysene-3,6-diphenol glucuronidation. It was found that UGT1A7 indeed catalyzed mono- and diglucuronide formation of both benzo[a]pyrene and chrysene 3,6-diphenols. V79 cell-expressed rat UGT1A6 also catalyzed these re…
Fluorinated Heterocyclic Compounds. A Photochemical Approach to a Synthesis of Fluorinated Quinazolin-4-ones
2004
An efficient and generalized photochemical methodology for the preparation of fluorinated quinazolin-4-ones is described. Depending on the starting substrate, quinazolin-4-ones bearing a perfluoroalkyl- or perfluoroaryl- substituent in position 2 or fluorine atoms on any positions of the benzo-fused moiety can easily be obtained. 5-Aryl-3-perfluoroalkylpentafluorophenyl- or 5-polyfluoroaryl-3-phenyl(methyl)-1,2,4-oxadiazoles, respectively, can be considered as ideal precursors that can be transformed into the target quinazolin-4-ones by irradiation in the presence of triethylamine (TEA) (at λ = 313 nm) or pyrene (at λ = 365 nm) in dry methanol or acetonitrile as solvent. Some mechanistic co…
Epoxidation of benzo[a]pyrene-7,8-dihydrodiol by human CYP1A1 in reconstituted membranes. Effects of charge and nonbilayer phase propensity of the me…
2002
Human cytochrome P4501A1 (CYP1A1) is one of the key enzymes in the bioactivation of environmental pollutants such as benzo[a]pyrene (B[a]P) and other polycyclic aromatic hydrocarbons. To evaluate the effect of membrane properties and distinct phospholipids on the activity of human CYP1A1 purified insect cell-expressed human CYP1A1 and of human NADPH-P450 reductase were reconstituted into phospholipid vesicle membranes. Conversion rates of up to 36 pmol x min(-1) x pmol(-1) CYP1A1 of the enantiomeric promutagens (-)- and (+)-trans-7,8-dihydroxy-7,8-dihydro-B[a]P (7,8-diol) to the genotoxic diolepoxides were achieved. The highest rates were obtained when negatively charged lipids such as phos…
Pyrene-benzoylthiophene Bichromophores as Selective Triplet Photosensitizers.
2006
Combination of the pyrene and benzoylthiophene units constitutes an interesting approach to design bichromophoric photosensitizers with increased intersystem crossing quantum yield and enhanced selectivity. The potential of this strategy has been illustrated in the present work by using a model photoisomerization reaction.
Flavonoids of honey and propolis : characterization and effects on hepatic drug-metabolizing enzymes and benzo(a)pyrene-DNA binding in rats
1996
The influence of dietary sunflower honey, propolis, and a flavonoid extract of propolis was examined on drug-metabolizing enzyme activities in rat liver and on microsome-mediated binding of benzo[a]pyrene to DNA. Characterization of flavonoids present in sunflower honey and propolis was achieved in order to assess the relative effects of different components of honey and propolis. Honey and propolis contained the same major flavonoids, pinocembrin, chrysin, galangin, and pinobanksin. The concentration of flavonoids was higher in propolis. Sunflower honey produced no significant changes on phase I and phase II enzyme activities and no modification of in vitro binding of benzo[a]pyrene to DNA…
Soil mutagens are airborne mutagens: variation of mutagenic activities induced in Salmonella typhimurium TA 98 and TA 100 by organic extracts of agri…
2000
As our hypothesis was that soil mutagens are airborne mutagens, possibly modified by soil microorganisms, we checked solvent extracts from agricultural and forest soils collected during late summer in the environment of Mainz, a region highly charged by anthropogenic air pollution, or near Bayreuth, a rural low charged region of Germany, or in a remote region of western Corsica without anthropogenic air pollution for the presence of mutagenicity in Salmonella typhimurium. Levels of mutagenic activities were quantified by calculation of revertants/g from the initial slope of dose-response curves applying tester strains S. typhimurium TA 98 and TA 100 in the absence and presence of an activat…