Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “FLUORENES”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 451 records · Page 25Linked to original sources

Theoretical studies on the electronic and optical properties of two new alternating fluorene/carbazole copolymers.

Poly(fluorene)-type materials are widely used in polymer-based emitting devices. During operation there appears, however, an additional emission peak at around 2.3 eV, leading to both a color instability and reduced efficiency. The incorporation of the carbazole units has been proven to efficiently suppress the keto defect emission. In this contribution, we apply quantum-chemical techniques to investigate two series of alternating fluorene/carbazole oligomers and copolymers poly[2,7-(N-(2-methyl)-carbazole)-co-alt-2,7-m(9,9-dimethylfluorene)], namely, PFmCz (m = 1,2) and gain a detailed understanding of the influence of carbazole units on the electronic and optical properties of fluorene derivatives. The electronic properties of the neutral molecules, HOMO-LUMO gaps (Delta(H-L)), in addition to the positive and negative ions, are studied using B3LYP functional. The lowest excitation energies (E(g)s) and the maximal absorption wavelength lambda(abs) of PFmCz (m = 1,2) are studied, employing the time-dependent density functional theory (TD-DFT). The properties of the two copolymers, such as Delta(H-L), E(g), IPs, and EAs were obtained by extrapolating those of the oligomers to the inverse chain length equal to zero (1/n = 0). The outcomes showed that the carbazole unit is a good electron-donating moiety for electronic materials, and the incorporation of carbazole into the polyfluorene (PF) backbone resulted in a broadened energy gap and a blue shift of both the absorption and photoluminescence emission peaks. Most importantly, the HOMO energies of PF1Cz and PF2Cz are both a higher average (0.4 eV) than polyfluorene (PF), which directly results in the decreasing of IPs of about 0.2 eV more than PF, indicating that the carbazole units have significantly improved the hole injection properties of the copolymers. In addition, the energy gap tends to broaden and the absorption and emission peaks are gradually blue-shifted to shorter wavelengths with an increase in the carbazole content in the copolymers. This is due to the interruption of the longer conjugation length of the backbone in the (F1Cz)(n) series.

Journal Article↗

Synthesis and evaluation of benzylfluorenyl and 1-arylethyl quaternary ammonium salts for antimicrobial and antineoplastic activities.

A number of substituted benzyldimethyl-9-fluorenylammonium bromides (II) and 9-benzylfluorenyl-9-trimethylammonium bromides (IV) were synthesized and examined for antimicrobial and anticancer activites. Series IV showed greater antimicrobial activity than Series II while some corresponding acyclic fluorene analogs were bereft of antimicrobial activities. Significant antineoplastic activity was not found in Series II and IIV. Representative fluorenes subjected to a preliminary screen for various pharmacological activities revealed marked anti-inflammatory and analgesic properties coupled with some antihistaminic activities. The acyclic quaternary ammonium compounds demonstrated substantial pressor activites.

Animals↗

Ability of polycyclic aromatic hydrocarbons to induce 7-ethoxyresorufin-o-deethylase activity in a trout liver cell line.

Along with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), 24 unsubstituted polycyclic aromatic hydrocarbons (PAHs) were evaluated for their ability to induce 7-ethoxyresorufin-o-deethylase (EROD) activity in the rainbow trout liver cell line RTL-W1. When the duration and cell density of exposure were increased, the EC(50) for EROD induction was relatively constant for TCDD, but increased for PAHs. Regardless of exposure conditions, EROD activity was not induced by 9 PAHs: naphthalene, phenanthrene, anthracene, pyrene, perylene, acenaphthylene, acenaphthene, fluorene, and fluoranthene. Two PAHs, benzo[g,h,i]perylene and coronene, induced EROD activity inconsistently. The remaining 13 PAHs consistently induced EROD activity. The EC(50)s for induction exhibited approximately a 110-fold range. The order of potency, from most to least potent, was benzo[k]fluoranthene, dibenzo[a,i]pyrene, dibenzo [a,h]anthracene, benzo[a]pyrene, indeno[1,2,3-cd]pyrene, benzo [b]fluoranthene, pentacene, benzo[b]anthracene, benzo[b] fluorene, chrysene, benzo[a]anthracene, benzo[e]pyrene, and triphenylene. When the induction potency was expressed relative to TCDD, the toxic equivalency factors (TEFs) ranged from 0.001 to 0.000 01. When expressed relative to benzo[a]pyrene, the TEFs ranged from 3.44 to 0. 03.

Animals↗

Mycoremediation of PAH-contaminated soil.

Out of a number of white-rot fungal cultures, strains of Irpex lacteus and Pleurotus ostreatus were selected for degradation of 7 three- and four-ring unsubstituted aromatic hydrocarbons (PAH) in two contaminated industrial soils. Respective data for removal of PAH in the two industrial soils by I. lacteus were: fluorene (41 and 67%), phenanthrene (20 and 56%), anthracene (29 and 49%), fluoranthene (29 and 57%), pyrene (24 and 42%), chrysene (16 and 32%) and benzo[a]anthracene (13 and 20%). In the same two industrial soils P. ostreatus degraded the PAH with respective removal figures of fluorene (26 and 35%), phenanthrene (0 and 20%), anthracene (19 and 53%), fluoranthene (29 and 31%), pyrene (22 and 42%), chrysene (0 and 42%) and benzo[a]anthracene (0 and 13%). The degradation of PAH was determined against concentration of PAH in non-treated contaminated soils after 14 weeks of incubation. The fungal degradation of PAH in soil was studied simultaneously with ecotoxicity evaluation of fungal treated and non-treated contaminated soils. Compared to non-treated contaminated soil, fungus-treated soil samples indicated decrease in inhibition of bioluminescence in luminescent bacteria (Vibrio fischerii) and increase in germinated mustard (Brassica alba) seeds.

Biodegradation, Environmental↗

Cloning, expression, and characterization of a self-sufficient cytochrome P450 monooxygenase from Rhodococcus ruber DSM 44319.

A new member of class IV of cytochrome P450 monooxygenases was identified in Rhodococcus ruber strain DSM 44319. As the genome of R. ruber has not been sequenced, a P450-like gene fragment was amplified using degenerated primers. The flanking regions of the P450-like DNA fragment were identified by directional genome walking using polymerase chain reaction. The primary protein structure suggests a natural self-sufficient fusion protein consisting of ferredoxin, flavin-containing reductase, and P450 monooxygenase. The only flavin found within the enzyme was riboflavin 5'-monophosphate. The enzyme was successfully expressed in Escherichia coli, purified and characterized. In the presence of NADPH, the P450 monooxygenase showed hydroxylation activity towards polycyclic aromatic hydrocarbons naphthalene, indene, acenaphthene, toluene, fluorene, m-xylene, and ethyl benzene. The conversion of naphthalene, acenaphthene, and fluorene resulted in respective ring monohydroxylated metabolites. Alkyl aromatics like toluene, m-xylene, and ethyl benzene were hydroxylated exclusively at the side chains. The new enzyme's ability to oxidize such compounds makes it a potential candidate for biodegradation of pollutants and an attractive biocatalyst for synthesis.

Amino Acid Sequence↗

Fluorophore(s) appended fullerene dyads and triads for probing photoinduced energy transfer: syntheses, electronic structure, and fluorescence studies.

Fullerene, C(60) was functionalized to possess one or two fluorophore entities. The fluorophore-fullerene dyads thus synthesized contain either a naphthalene, pyrene, or fluorene entity while the triads contain either a pyrene or fluorene entity in addition to a naphthalene entity. The redox behavior of these dyads and triads were probed by cyclic voltammetric technique, while the geometry and electronic structures were deduced from ab initio B3LYP/3-21G(*) method. Steady-state emission studies revealed the occurrence of energy transfer from the singlet excited fluorophore to the fullerene entity in the case of the dyads while the occurrence of step-by-step sequential energy transfer is envisioned in the case of the triads. A better 'antenna-effect' owing to the extended range of excitation wavelength to induce energy transfer to the appended fullerene has been achieved in the case of the triads.

Computational Biology↗

Arylamidation and arylation by the carcinogen N-2-fluorenylacetamide: a sensitive and rapid radiochemical assay.

N-acetoxy-N-arylacetamides, which are generally considered as an ultimate carcinogenic form of the corresponding N-arylacetamides, react with the cellular macromolecules (nucleic acids, proteins, etc.) to give two types of adducts: (I) arylamidation and (II) arylation addition products. In this paper, we present a radiochemical determination of the amount of N-2-fluorenylacetamide bound to DNA via arylamidation or arylation, respectively. This assay is based upon the difference of stability under weak alkali hydrolysis conditions (0.1 N NaOH, 75 degrees C, 2 h) of the specifically 14C-labeled N-acetyl group of the N-2-fluorenylacetamide residue linked to the macromolecule either via arylamidation or arylation. Native DNA which has been reacted with N-acetoxy-N-2-[14C]acetylaminofluorene exhibits 16% of the fluorene adducts linked to the bases via arylation. On the other hand, denatured DNA reacts with the fluorene derivative to give almost only arylamidation addition products.

2-Acetylaminofluorene↗

HRP-catalyzed bioactivation of carcinogenic hydroxamic acids. The greater reactivity of glycolyl- versus acetyl-derived hydroxamic acids.

An analysis of the hydroxamic acid oxidation reaction by H2O2 and horseradish peroxidase (HRP) was made with three pairs of hydroxamic acids. Each pair consisted of the aceto- and glycolhydroxamic acid derivatives from one of three different arylhydroxylamines. The parent arylhydroxylamines were the known carcinogens, N-hydroxy-2-aminofluorene and N-hydroxy-4-aminobiphenyl and the noncarcinogen 4-chlorophenyl-hydroxylamine. All the hydroxamic acids appeared to be converted to products that were expected on the basis of the previously-proposed mechanism of this peroxidative reaction. Each acetohydroxamic acid gave the corresponding nitroso compound and O-acetyl ester of the starting material in approximately equal amounts. The glycolhydroxamic acids gave the corresponding nitroso compound and a relatively unstable product that was proposed, by analogy, to be the O-glycolyl ester of the starting material. A comparison of the initial rates of reaction of each hydroxamic acid pair showed that the glycolhydroxamic acid was much more susceptible to the peroxidation reaction than was the corresponding acetohydroxamic acid. The initial rate of the reaction was also highly dependent upon the nature of the aromatic ring in the order fluorene greater than biphenyl greater than 4-chlorophenyl. The relative degree of HRP-catalyzed covalent binding to DNA of the aceto- and glycolhydroxamic acids in the fluorene series was studied and found to parallel the relative rates of reaction of these substrates in the H2O2/HRP system. It was proposed that glycolhydroxamic acids are likely to be more genotoxic than are acetohydroxamic acids when subjected to peroxidative bioactivation conditions.

Biotransformation↗

Mutagenicity of nitro derivatives induced by exposure of aromatic compounds to nitrogen dioxide.

Mutagenic nitro derivatives were readily induced when 6 kinds of chemicals were exposed to 10 ppm of nitrogen dioxide (NO2). Single nitro derivatives were formed from pyrene, phenanthrene, fluorene or chrysene. Carbazole and fluoranthene each produced 2 derivatives substituted with nitro groups at different positions. The formation of nitro derivatives was enhanced by exposure of pyrene to NO2 containing nitric acid (HNO3, less than 100-fold enhancement) or sulphur dioxide (SO2, less than 15-fold enhancement). After 24 h of exposure the yields of the nitro derivative were 0.02% with 1 ppm of NO2 in air and 2.85% with NO2 (1 ppm) containing traces of HNO3. The nitro derivatives from all but phenanthrene and carbazole were chemically identified by means of gas chromatography (GC) and mass spectrometry (MS), and the mutagenicity of the 4 kinds of authentic nitro derivatives was tested by using Salmonella strains TA98 and TA1538 with or without the S9 fraction from rat liver treated with Aroclor 1254. The nitro derivative induced from pyrene was determined to be 1-nitropyrene; that of chrysene was 6-nitrochrysene; that of fluorene was 2-nitrofluorene; and those of fluoranthene were 3-nitrofluoranthene, and 8-nitrofluoranthene. Tested with strain TA98 in the absence of the S9 fraction, the first 4 of these derivatives yielded, respectively, 3050, 269, 433 and 13 400 revertants per nmole. Thus, each nitro derivative formed was potentially a direct-acting frameshift-type mutagen. Each compound exposed to NO2 showed a decreased mutagenic activity when tested in the presence of S9 mix. A possible explanation comes from experiments in which 1-nitropyrene was incubated with the S9 mix at 37 degree C for 10 min, and 1-aminopyrene was formed. The mutagenic activity of 1-aminopyrene was appreciable, but only about one-tenth of that of 1-nitropyrene in the Ames test.

Heterocyclic Compounds↗

Polycyclic aromatic compounds in Northwest Atlantic COD (Gadus morhua).

Twenty-seven polycyclic aromatic compounds (PAC) including polycyclic aromatic hydrocarbons (PAH) and polycyclic aromatic sulphur heterocycles were analysed in muscle, liver and ovaries of cod (Gadus morhua) from the Northwest Atlantic. These PAC include the 16 PAH priority pollutants (EPA recommendation), alkylated naphthalenes, phenanthrene-anthracenes as well as dibenzothiophenes (DBT). Aromatics were undetectable in muscle. One of the analysed PAC was detected in one ovary and six in another ovary sample. Liver samples contained between 1 and 9 PAC. Of the parental PAH, only acenapthene (18 ng/g, dry weight), fluorene (28 ng/g) and chrysene (22 ng/g) were detected once each in two liver samples, while fluorene (72 ng/g) was detected once in one of the ovaries. C-2 DBT was the major component in ovaries and liver (8-86 ng/g), while C-3 and C-4 alkylated phenanthrene-anthracene (12-78 ng/g) were the next major components detected in the liver samples. This is the first detailed study of PAH and PAC in finfish from the Northwest Atlantic.

Journal Article↗

Removal of aqueous-phase polynuclear aromatic hydrocarbons using aspen wood fibers.

Roadway runoff derived polynuclear aromatic hydrocarbons (PAHs) impact the quality of surface and ground water. Inexpensive aspen wood fibers have been investigated as a means to remove dissolved PAH under laboratory conditions. Our isotherm experiments demonstrated that the uptake of naphthalene, fluorene, anthracene, and pyrene required up to 12.5 days to reach equilibrium. Aspen wood-water sorption coefficients, Kww, were linearly correlated to octanol-water partition coefficients and the molecular weight of the studied PAH compounds. The correlation between Kww and molecular weight was the most significant. Column experiments were carried out to study the sorption and desorption of fluorene, anthracene, and pyrene under dynamic conditions. The results indicate linear sorption, but non-linear desorption behavior. The degree of desorption was inversely correlated to a compound's hydrophobicity. Flow interruption experiments showed that sorption and desorption was rate limited. A mass balance of the sorption and desorption tests indicated that sorptive uptake exceeded desorptive release over a given number of pore volumes. Further, absolute mass-removal efficiency increased with the molecular weight and hydrophobicity of the PAH compound. Batch and column studies demonstrated that aspen wood has the potential to become an effective remedial agent for PAH in stormwater runoff or other PAH contaminated waters.

Adsorption↗

Anaerobic PAH degradation in soil by a mixed bacterial consortium under denitrifying conditions.

Polycyclic aromatic hydrocarbons (PAHs) are one of the main classes of contaminants in the terrestrial environment. Concentrations of biphenyl, fluorene, phenanthrene and pyrene were added to soil samples in order to investigate the anaerobic degradation potential of PAHs under denitrifying conditions. A mixed population of microorganisms obtained from a paddy soil was incubated for 20 days in anaerobic conditions in the presence of soil alone or with nitrate, adding, as electron donors, PAHs and, in some samples, glucose or acetate. At regular time intervals oxidation-reduction potential, PAHs concentration, microbial ATP and nitrate concentration into the solution were measured. Degradation trends for each hydrocarbon are similar under all conditions, indicating that the molecular conformation prevails over other parameters in controlling the degradation. Poor degradation results were obtained when PAHs were the only organic matter available for the inoculum, thus confirming the recalcitrance to degradation of these compounds. Biodegradation was influenced by the addition of other carbon sources. As better degradation results were generally obtained when acetate or glucose were added, the hypothesis of a co-metabolic enhancement of PAH biodegradation seems likely. Thus, anaerobic biodegradation of PAHs studied, biphenyl, fluorene, phenanthrene and pyrene, seems to be possible both through fermentative and respiratory metabolism, provided that low molecular weight co-metabolites and suitable electron acceptors (nitrate) are present.

Adenosine Triphosphate↗

Study of metabolites from the degradation of polycyclic aromatic hydrocarbons (PAHs) by bacterial consortium enriched from mangrove sediments.

The PAH metabolites produced during degradation of fluorene, phenanthrene and pyrene by a bacterial consortium enriched from mangrove sediments were analyzed using the on-fiber silylation solid-phase microextraction (SPME) combining with gas chromatography-mass spectrometry (GC-MS) method. Seventeen metabolites at trace levels were identified in different PAH degradation cultures based on the full scan mass spectra. In fluorene degradation cultures, 1-, 2-, 3- and 9-hydroxyfluorene, fluorenone, and phthalic acid were detected. In phenanthrene and pyrene degradation cultures, various common metabolites such as phenanthrene and pyrene dihydrodiols, mono-hydroxy phenanthrene, dihydroxy pyrene, lactone and 4-hydroxyphenanthrene, methyl ester, and phthalic acid were found. The detection of various common and novel metabolites demonstrates that SPME combining with GC-MS is a quick and convenient method for identification as well as monitoring the real time changes of metabolite concentrations throughout the degradation processes. The knowledge of PAH metabolic pathways and kinetics within indigenous bacterial consortium enriched from mangrove sediments contributes to enhance the bioremediation efficiency of PAH in real environment.

Bacteria↗

A comparative analysis of the toxicity of eight common soil contaminants and their effects on drought tolerance in the collembolan Folsomia candida.

Previous exposure to contaminants can increase the susceptibility to drought stress in soil invertebrates. In the present study, the effects of eight common environmental contaminants on drought tolerance and reproduction were investigated using the collembolan Folsomia candida as a model organism. Four classes of chemicals were considered: polycyclic aromatic hydrocarbons (pyrene and fluorene), detergents (linear alkylbenzene sulfonate (LAS) and nonylphenol), insecticides (dimethoate and cypermethrin), and heavy metals (copper and cadmium). Previous exposure to nonylphenol, pyrene, and fluorene had significant effects on drought tolerance. LAS had a weak effect on drought tolerance, whereas the remaining chemicals had no such effects even at concentrations at which reproduction was considerably reduced. Reproduction and adult survival in F. candida were equally sensitive to dimethoate. However, for all other chemicals, reproduction was a considerably more sensitive parameter than adult survival. The results suggest that toxicants whose effects are associated with cell membrane function are the most potent with respect to effect on drought tolerance.

Adaptation, Physiological↗

Polycyclic aromatic hydrocarbon biodegradation in extracellular fluids and static batch cultures of selected sub-tropical white rot fungi.

Four sub-tropical white rot fungi, Trametes versicolor, Trametes pocas, Trametes cingulata and isolate DSPM95 were studied alongside the well studied white rot fungus, Phanerochaete chrysosporium, for their ability to remove polycyclic aromatic hydrocarbons (PAHs) from culture media. Both static shallow cultures and extracellular fluids were studied using media contaminated with a defined mixture of the PAHs; fluorene, phenanthrene, anthracene, pyrene and benzo(a)anthracene. With all isolates, the total loss of the parent compound in 31 days was high for fluorene, at +60%, phenanthrene at +40% and anthracene at +42%. Biotransformation of pyrene and benzo(a)anthracene by all the isolates was low, with the highest reduction of pyrene of 15.2% and benzo(a)anthracene of 15.8% being achieved with P. chrysosporium. Disappearance of the more condensed PAHs, pyrene and benzo(a)anthracene, increased in shallow static cultures with the addition of glucose and glucose oxidase as a source of additional H2O2. The addition of Mn2+ and ABTS (2,2-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid)) to culture supernatants was associated with higher levels of biotransformation. Comparison of the isolates T. versicolor, T. pocas, T. cingulata and isolate DSPM95 with P. chrysosporium showed that these strains were competitive in the reduction of the PAHs, reducing the PAHs by more or less the same magnitude. Also these sub-tropical isolates did not accumulate a lot of HPLC detectable metabolites as much as P. chrysosporium.

Basidiomycota↗

Photomutagenicity of 16 polycyclic aromatic hydrocarbons from the US EPA priority pollutant list.

The photomutagenicity of 16 polycyclic aromatic hydrocarbons (PAHs), all on the United States Environmental Protection Agency (US EPA) priority pollutant list, was studied. Concomitant exposing the Salmonella typhimurium bacteria strain TA102 to one of the PAHs and light (1.1 J/cm2 UVA+2.1 J/cm2 visible) without the activation enzyme S9, strong photomutagenic response is observed for anthracene, benz[a]anthracene, benzo[ghi]perylene, benzo[a]pyrene, indeno[1,2,3-cd]pyrene, and pyrene. Under the same conditions, acenaphthene, acenaphthylene, benzo[k]fluoranthene, chrysene, and fluorene are weakly photomutagenic. Benzo[b]fluoranthene, fluoranthene, naphthalene, phenanthrene, and dibenz[a,h]anthracene are not photomutagenic. These results indicate that PAHs can be activated by light and become mutagenic in Salmonella TA102 bacteria. At the same time, the mutagenicity for all the 16 PAHs was examined with the standard mutagenicity test with 10% S9 as the activation system. Benzo[b]fluoranthene, benzo[k]fluoranthene, chrysene, acenaphthylene, and fluorene are weakly mutagenic, while the rest of the PAHs are not. In general, the photomutagenicity of PAHs in TA102 does not correlate with their S9-activated mutagenicity in either TA102 or TA98/TA100 since they involve different activation mechanisms.

Animals↗

The influence of planarity, rigidity and internal heavy atom upon fluorescence parameters and the intersystem crossing rate constant in molecules with the biphenyl basis.

Fluorescence properties of 10 specially chosen aromatic compounds with the biphenyl basis, differing in the degree of planarity, rigidity and in the nature of the internal heavy atom, but family-related in pi-structure are experimentally studied at room temperature (293K). The quantum yield of fluorescence, gamma, and fluorescence decay time, pi(f), of deaerated and non-deaerated cyclohexane solutions are measured. The oscillator strength, f(e), of S0-->S1 transition, fluorescence rate constant, k(f), natural lifetime, tau0(T), and intersystem crossing rate constant, k(ST), are calculated for each compound. It was observed that the increase in planarity and rigidity causes the k(ST) value to decrease very significantly. Any disturbance of the pi-system by the torsional vibrations of the substituted part of the molecule causes the k(ST) value to increase. The introduction of a heavy atom instead of the methylene bridge of fluorene leads to the increase in the k(ST) value and to the decrease in the f(e) of the 1A-->1La transition. The absence of laser action of fluorene is explained.

Biphenyl Compounds↗

DNA sequence analysis of mutations induced by N-2-acetylamino-7-iodofluorene in plasmid pBR322 in Escherichia coli.

The spectrum of mutations induced by N-2-acetylamino-7-iodofluorene (AAIF) was analyzed in a forward mutation system based on mutagenesis directed to a small restriction fragment in the tetracycline resistance gene of plasmid pBR322. AAIF was found to induce frameshift mutations and base-pair substitutions at approximately equal frequencies. The frameshift mutations were mostly deletions of single base-pairs, but -2 frameshifts and +1 frameshifts were also detected. With one exception, the substitutions were transversions initiated at a G.C base-pair. Both frameshift mutations and transversions occurred preferentially at sites of repetitive guanine residues. Although AAIF and the related aromatic amines N-2-acetylaminofluorene (AAF) and N-2-aminofluorene (AF) all bind to the C-8 position of guanine, they have different effects on DNA conformation, and these differences are reflected in their mutation spectra. Previous studies have provided evidence that AAF adducts can trigger a B to Z conformational change in alternating GC sequences or displacement of the guanine by the fluorene ring in other sequences; the principal result is two classes of frameshift mutations. AF, whose DNA interaction involves outside binding rather than insertion and denaturation, primarily induces base-pair substitutions. AAIF adducts are chemically similar to AAF adducts, but the iodo group apparently hinders insertion of the fluorene ring into DNA. Consistent with this model, the mutation spectrum of AAIF combines properties of the mutation spectra of both AAF and AF.

2-Acetylaminofluorene↗