Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Oxygen Compounds”

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 217 records · Page 12Linked to original sources
PubMed2006

Production of bio-fuels by high temperature pyrolysis of sewage sludge using conventional and microwave heating.

The pyrolysis of sewage sludge was investigated using microwave and electrical ovens as the sources of heat, and graphite and char as microwave absorbers. The main objective of this work was to maximize the gas yield and to assess its quality as a fuel and as a source of hydrogen or syngas (H2 + CO). Both gases were produced in a higher proportion by microwave pyrolysis than by conventional pyrolysis, with a maximum value of 38% for H2 and 66% for H2 + CO. The oils obtained were also characterized using FTIR and GC-MS. The use of conventional electrical heating in the pyrolysis of sewage sludge produced an oil that could have a significant environmental and toxicological impact. Conversely, microwave pyrolysis still preserved some of the functional groups of the initial sludge such as aliphatic and oxygenated compounds, whereas no heavy PACs were detected.

Bioelectric Energy Sources↗
PubMed2004

Synthesis and structure-activity relationships of thioflavone derivatives as specific inhibitors of the ERK-MAP kinase signaling pathway.

Condensation of nitrobenzaldehydes 3 and alpha-[o-(p-methoxybenzylthio)benzoyl] sulfoxide 4 gave alpha-sulfinyl enones 5. Treatment of 5 with formic acid caused cyclization followed by debenzylation to afford 3-(methylsulfinyl)thioflavanones 6. Double-bond formation with elimination of methanesulfenic acid was performed by refluxing 6 in benzene, and, finally, the nitro group of 2-phenyl-4H-1-benzothiopyran-4-one (thioflavones) 7 was reduced with tin in tetrafluoroboric acid. Various 2'-aminothioflavones 8 thus prepared were evaluated for their inhibitory effects on the ERK-MAP kinase pathway. In a cell-based assay, 2-(2'-amino-3'-methoxyphenyl)-4H-1-benzothiopyran-4-one (8b) showed a more potent inhibitory effect than the corresponding oxygen compound (PD98059, 1) on the Raf-induced activation of the ERK-MAP kinase pathway as well as cell proliferation. Furthermore, compound 8b selectively and potently inhibited the proliferation of tumor cells in which the ERK-MAP kinase pathway is constitutively activated.

Animals↗
PubMed1999

Exocytosis of neutrophil granulocytes.

Neutrophil granulocytes play an important role in the defense mechanisms of mammalian organisms against bacterial invaders. The combat arsenal of neutrophils consists of engulfing and endocytosing the foreign particle, producing toxic oxygen compounds, and liberating substances stored in intracellular vesicles. At least four different types of granules are formed during maturation of neutrophil granulocytes in the bone marrow. Functional properties of release from the different granule populations differ in several respects from characteristics of neurotransmitter release, the best understood secretory process in mammals. The available data indicate that several key proteins of the exocytotic machinery identified in neural tissue either are absent from neutrophil granulocytes or their subcellular localization is different. Furthermore, in a human disease (Chédiak-Higashi syndrome), the defect of the secretory pathway affects mainly the cells of the haemopoietic lineage. Taken together, these data suggest that regulated exocytosis from neutrophil granulocytes (or perhaps also from other haemopoietic cells) may represent a specific case of the general mechanism of secretion.

Cell Degranulation↗
PubMed2000

Epoxide hydrolases: biochemistry and molecular biology.

Epoxides are organic three-membered oxygen compounds that arise from oxidative metabolism of endogenous, as well as xenobiotic compounds via chemical and enzymatic oxidation processes, including the cytochrome P450 monooxygenase system. The resultant epoxides are typically unstable in aqueous environments and chemically reactive. In the case of xenobiotics and certain endogenous substances, epoxide intermediates have been implicated as ultimate mutagenic and carcinogenic initiators Adams et al. (Chem. Biol. Interact. 95 (1995) 57-77) Guengrich (Properties and Metabolic roles 4 (1982) 5-30) Sayer et al. (J. Biol. Chem. 260 (1985) 1630-1640). Therefore, it is of vital importance for the biological organism to regulate levels of these reactive species. The epoxide hydrolases (E.C. 3.3.2. 3) belong to a sub-category of a broad group of hydrolytic enzymes that include esterases, proteases, dehalogenases, and lipases Beetham et al. (DNA Cell Biol. 14 (1995) 61-71). In particular, the epoxide hydrolases are a class of proteins that catalyze the hydration of chemically reactive epoxides to their corresponding dihydrodiol products. Simple epoxides are hydrated to their corresponding vicinal dihydrodiols, and arene oxides to trans-dihydrodiols. In general, this hydration leads to more stable and less reactive intermediates, however exceptions do exist. In mammalian species, there are at least five epoxide hydrolase forms, microsomal cholesterol 5,6-oxide hydrolase, hepoxilin A(3) hydrolase, leukotriene A(4) hydrolase, soluble, and microsomal epoxide hydrolase. Each of these enzymes is distinct chemically and immunologically. Table 1 illustrates some general properties for each of these classes of hydrolases. Fig. 1 provides an overview of selected model substrates for each class of epoxide hydrolase.

Animals↗
PubMed1998

Serum nitrates and creatinine in workers exposed to atmospheric nitrogen oxides and ammonia.

An epidemiological survey was carried out on 332 workers in a nitrogen fertilizer factory exposed to various levels of NO, NO2, NO3- and NH3. The population was divided into six groups as a function of the atmospheres in the different workshops and compared with a control group recruited outside the factory. We investigated the relations between the exposures of the different groups and serum levels of three nitrogen-containing derivatives involved in arginine metabolism: nitrates, creatinine and urea. The workers most exposed to the hydrogenated and oxygenated compounds of nitrogen were found to have the highest serum nitrates. Further analysis of the results showed that inhaled nitrogen oxides and ammonia were only partly responsible for the circulating nitrates. The excess nitrates were thought to have an endogenous origin due to inflammatory reactions induced by the pollutants, especially ammonia. In addition, we showed that the workers from the two groups exposed to both NO and NH3 had significantly elevated levels of serum creatinine (P < 0.001). The excess creatinine was thought to have derived from the interaction of the exogenous NO with arginine metabolites.

Adult↗
PubMed2003

Photo-oxidation products of petroleum hydrocarbons in the Eastern Red Sea coastal waters.

The level of dissolved oil residues as well as the oxygenated petroleum hydrocarbons in the seawater of the affected area of Jeddah coast, Red Sea was estimated. The dissolved/dispersed petroleum hydrocarbons concentration was found minimal. The minimum level may be attributed to the action of the weathering processes. Selected samples of the dichloromethane extracts of seawater were fractionated, using silica gel columns, into four fractions eluted with solvents of increasing polarity. The fluorescence intensity of these fractions was measured at three different pairs of excitation and emission wavelengths using ultraviolet fluorescence spectrofluorophotometry (UVF). The total fluorescence intensity of the fractions at 280 nm excitation, 327 nm emission wavelengths and 310 nm excitation, 360 nm emission wavelengths exceeds the fluorescence intensity of the whole extract by more than two orders of magnitude. The estimation of higher molecular mass oxygenated compounds in the fourth fractions, read at 380 nm excitation, 430 nm emission wavelengths, indicates rather low concentrations of <1 microg l(-1) hydroxypyrene equivalents. However, the polar fractions (eluted with acetone) account for more than 25% of the total fluorescence intensity of all fractions combined at each pair of wavelengths. The characterization of the products causing the fluorescence particularly the high molecular mass compounds still presents difficulties. Preliminary GC/MS results revealed some evidence for petroleum hydrocarbon oxidation products. Alkyl isobenzofuranones have been found in some seawater extracts. This is an ongoing project to characterize and identify additional compounds from these extracts.

Gas Chromatography-Mass Spectrometry↗
PubMed2002

The disulfide redox system of Schistosoma mansoni and the importance of a multifunctional enzyme, thioredoxin glutathione reductase.

Schistosoma mansoni, a causative agent of schistosomiasis, is a major cause of human morbidity in tropical countries. Adult schistosomes, which reside in the hepatic portal system, are exposed to reactive oxygen compounds through respiration and as a result of the host immune response. To minimize oxidative stress schistosomes must possess adequate mechanisms of detoxification. Major detoxification systems rely on reducing equivalents from the disulfide oxidoreductases glutathione and thioredoxin. Therefore, maintenance of adequate levels of these thiols in a reduced form is critical. Here we show that S. mansoni possess an unusual thiol redox system centered on thioredoxin glutathione reductase. This enzyme represents an unusual fusion of a pyridine nucleotide disulfide oxidoreductase with a redox active glutaredoxin extension. Furthermore, we predict that this is a selenocysteine protein. Immunoprecipitation, western blot and inhibitor studies show that this protein has thioredoxin reductase, glutathione reductase, and glutaredoxin activities. Most importantly, we show that thioredoxin glutathione reductase appears to be the major, if not the sole enzyme for these activities in adult worms, completely replacing thioredoxin reductase and glutathione reductase. This is the first example of an organism with a redox system based exclusively on thioredoxin glutathione reductase.

Amino Acid Sequence↗
PubMed2000

Differential developmental expression and cell type specificity of Dictyostelium catalases and their response to oxidative stress and UV-light.

Cells of Dictyostelium discoideum are highly resistant to DNA damaging agents such as UV-light, gamma-radiation and chemicals. The genes encoding nucleotide excision repair (NER) and base excision repair (BER) enzymes are rapidly upregulated in response to UV-irradiation and DNA-damaging chemicals, suggesting that this is at least partially responsible for the resistance of this organism to these agents. Although Dictyostelium is also unusually resistant to high concentrations of H(2)O(2), little is known about the response of this organism to oxidative stress. To determine if transcriptional upregulation is a common mechanism for responding to DNA-damaging agents, we have studied the Dictyostelium catalase and Cu/Zn superoxide dismutase antioxidant enzymes. We show that there are two catalase genes and that each is differentially regulated both temporally and spatially during multicellular development. The catA gene is expressed throughout growth and development and its corresponding enzyme is maintained at a steady level. In contrast, the catB gene encodes a larger protein and is only expressed during the final stages of morphogenesis. Cell type fractionation showed that the CatB enzyme is exclusively localized to the prespore cells and the CatA enzyme is found exclusively in the prestalk cells. Each enzyme has a different subcellular localization. The unique developmental timing and cell type distribution suggest that the role for catB in cell differentiation is to protect the dormant spores from oxidative damage. We found that exposure to H(2)O(2) does not result in the induction of the catalase, superoxide dismutase, NER or BER mRNAs. A mutant with greatly reduced levels of catA mRNA and enzyme has greatly increased sensitivity to H(2)O(2) but normal sensitivity to UV. These results indicate that the natural resistance to oxidative stress is not due to an ability to rapidly raise the level of antioxidant or DNA repair enzymes and that the response to UV-light is independent from the response to reactive oxygen compounds.

Amino Acid Sequence↗
PubMed1999

Oxidative stress and DNA damage in Fischer rats following acute exposure to trichloroethylene or perchloroethylene.

Oxidative DNA damage is emerging as an biomarker of effect in studies assessing the health risks of occupational chemicals. Trichloroethylene (TCE) and perchloroethylene (PERC) are used in the dry cleaning industry and their metabolism can produce reactive oxygen compounds. The present study examined the potential for TCE and PERC to induce oxidative DNA damage in rats that was detectable as increased urinary excretion of 8-hydroxydeoxyguanosine (8OHdG). Thiobarbaturic acid reactive substances (TBARS) and 8-epiprostaglandin F2alpha (8epiPGF) were also measured as biomarkers of increased oxidative stress. Male Fischer rats were administered a single i.p. injection of 0, 100, 500, or 1000 mg/kg of PERC or TCE. Control rats received only vehicle (1:4 v/v of Alkamuls/water). A positive control group received 100 mg/kg 2-nitropropane (2NP). Rats were sacrificed 24 h after dosing. In rats receiving 2NP or TCE but not PERC, TBARS and the 8OHdG/dG ratios were significantly elevated in liver. Lymphocyte 8OHdG/dG was not affected significantly by 2NP, TCE or PERC. In rats receiving 2NP, urinary excretion of 8OHdG and 8epiPGF2 were significantly increased. In rats receiving TCE or PERC, significant increases in 8epiPGF2 or 8OHdG were not evident. Results indicate that a single high dose of TCE, but not PERC, can induce an increase in oxidative DNA damage in rat liver. However, the usefulness of 8OHdG as a biomarker of TCE-induced oxidative DNA damage is questionable.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed2001

Biocatalytic synthesis of hydroxylated natural products using aldolases and related enzymes.

Synthetic building blocks bearing hydroxylated chiral centers are important targets for biocatalysis. Many C-C bond forming enzymes have recently been investigated for new applications and new strategies towards the synthesis of natural products and related oxygenated compounds. Several old catalysts have been studied to increase our functional knowledge of natural aldolase-type enzymes, and new mutated catalysts or catalytic antibodies have been tested for their synthetic utility.

Aldehyde-Lyases↗
PubMed2000

Ring opening of benzo[a]pyrene in the germ-free rat is a novel pathway for formation of potentially genotoxic metabolites.

The metabolism of benzo[a]pyrene (BP) is known to lead to a large number of oxygenated compounds, some of which can bind covalently to DNA. We have studied the integrated metabolism of BP in vivo in germ-free rats given (14)C-labeled BP. Urinary metabolites were separated into groups according to acidity using lipophilic ion exchangers. The groups were analyzed by mass spectrometry and were further fractionated by high-performance liquid chromatography. The fraction of urinary metabolites previously shown to contain N-acetylcysteine and glucuronic acid conjugates was found to contain derivatives of 7-oxo-benz[d]anthracene-3,4-dicarboxylic acid as major components. These compounds, which were identified by mass spectrometry and NMR, accounted for about 30% of the total metabolites in urine, demonstrating that, surprisingly, ring opening is a major pathway for metabolism of BP in the germ-free rat. The dicarboxylic acid may be excreted in urine as an ester glucuronide. By using the single cell gel electrophoresis or COMET assay, we were able to demonstrate that the anhydride of 7-oxo-benz[d]anthracene-3, 4-dicarboxylic acid was an efficient inducer of DNA damage. Taken together, these results indicate that the novel ring opening metabolic pathway may provide alternative mechanisms for the toxicity of BP.

Animals↗
PubMed2005

Measurements of secondary organic aerosol from oxidation of cycloalkenes, terpenes, and m-xylene using an Aerodyne aerosol mass spectrometer.

The Aerodyne aerosol mass spectrometer (AMS) was used to characterize physical and chemical properties of secondary organic aerosol (SOA) formed during ozonolysis of cycloalkenes and biogenic hydrocarbons and photo-oxidation of m-xylene. Comparison of mass and volume distributions from the AMS and differential mobility analyzers yielded estimates of "effective" density of the SOA in the range of 0.64-1.45 g/cm3, depending on the particular system. Increased contribution of the fragment at m/z 44, C02+ ion fragment of oxygenated organics, and higher "delta" values, based on ion series analysis of the mass spectra, in nucleation experiments of cycloalkenes suggest greater contribution of more oxygenated molecules to the SOA as compared to those formed under seeded experiments. Dominant negative "delta" values of SOA formed during ozonolysis of biogenics indicates the presence of terpene derivative structures or cyclic or unsaturated oxygenated compounds in the SOA. Evidence of acid-catalyzed heterogeneous chemistry, characterized by greater contribution of higher molecular weight fragments to the SOA and corresponding changes in "delta" patterns, is observed in the ozonolysis of alpha-pinene. Mass spectra of SOA formed during photooxidation of m-xylene exhibit features consistent with the presence of furandione compounds and nitro organics. This study demonstrates that mixtures of SOA compounds produced from similar precursors result in broadly similar AMS mass spectra. Thus, fragmentation patterns observed for biogenic versus anthropogenic SOA may be useful in determining the sources of ambient SOA.

Aerosols↗
PubMed2003

Volatile constituents from Cinnamomum zeylanicum fruit stalks and their antioxidant activities.

Cinnamomum zeylanicum Blume is an important spice and aromatic crop having wide applications in flavoring, perfumery, beverages, and medicines. The steam-distilled volatile oil from cinnamon fruit stalks was analyzed with GC and GC-MS. It showed the presence of hydrocarbons (44.7%) and oxygenated compounds (52.6%). Twenty-seven compounds constituting ca. 95.98% of the volatile oil were characterized. (E)-Cinnamyl acetate (36.59%) and (E)-caryophyllene (22.36%) are found to be major compounds. The volatile oil was screened for its potential as an antioxidant by using in vitro models, such as the beta-carotene-linoleate and phosphomolybdenum complex method. The volatile oil showed 55.94% and 66.9% antioxidant activity at 100 and 200 ppm concentration, respectively. Also, the volatile oil showed good antioxidant capacity, using the formation of the phosphomolybdenum complex. A comparison of the chemical composition of the volatile oil was made with that of buds, flowers, and fruits. This is the first report on the chemical composition of volatile oil of the fruit stalks of this species and its antioxidant activity.

Alcohols↗
PubMed2000

Chemical composition of the flower oil of Cinnamomum zeylanicum blume.

The steam-distilled oil of cinnamon (Cinnamomum zeylanicum) flowers was analyzed by GC and GC-MS. It consists of 23% hydrocarbons and 74% oxygenated compounds. A total of 26 compounds constituting approximately 97% of the oil were characterized. (E)-Cinnamyl acetate (41.98%), trans-alpha-bergamotene (7.97%), and caryophyllene oxide (7.2%) are found to be major compounds. This is the first report on the chemical composition of the flower oil of Cinnamomum zeylanicum.

Cinnamomum zeylanicum↗
PubMed2000

Variable strategy toward carbasugars and relatives. 1. Stereocontrolled synthesis of pseudo-beta-D-gulopyranose, pseudo-beta-D-xylofuranose, (pseudo-beta-D-gulopyranosyl)amine, and (pseudo-beta-D-xylofuranosyl)amine.

Four novel, chiral nonracemic carbasugars have been synthesized from 1,2-O-isopropylidene-D-glyceraldehyde. Furan- and pyrrole-based 2-silyloxy dienes--mimics of the alpha,gamma-dianions of gamma-hydroxy- and gamma-aminobutanoic acid, respectively--nicely served to complete the syntheses of two all-oxygen compounds, pseudo-beta-D-gulopyranose and pseudo-beta-D-xylofuranose, and two "anomeric" amino derivatives, (pseudo-beta-D-gulopyranosyl)amine (1,2,4-tri-epi-validamine) and (pseudo-beta-D-xylofuranosyl)amine. Two sequential, highly diastereoselective carbon-carbon bond-forming maneuvers, i.e., a vinylogous crossed aldol addition and an intramolecular aldolization, proved central to these constructions. The fact that readily available heterocyclic diene scaffolds can be employed in the assembly of a varied repertoire of carbasugars and analogues widens the prospects of dienoxy silane chemistry.

Carbohydrates↗
PubMed2003

A facile synthesis of enantiopure tricyclic furanyl and pyranyl derivatives via tungsten-mediated cycloalkenation and Diels-Alder reaction.

We report the synthesis of chiral furanyl and pyranyl dienes 1 and 2 based on cycloalkenation of chiral tungsten alkynol complexes. These two dienes bear a chiral 1,3-dioxolane group to control diastereoselective Diels-Alder reactions with electron-deficient olefins. The chiral 1,3-dioxolane substituents of the cycloadducts were degraded into hydrogen atoms to make these molecules possess common furan and pyran rings. Dienes 1 and 2 are good building blocks for enantiopure forms of tricyclic oxygen compounds.

Journal Article↗
PubMed2003

Gauging the significance of atomic oxygen [O(3P)] in sulfoxide photochemistry. A method for hydrocarbon oxidation.

A liquid-phase photolysis of 1,2-benzodiphenylene sulfoxide, 1, and dibenzothiophene sulfoxide, 2, was used to generate atomic oxygen [O(3P)] or an equivalent active oxygen species. The reaction for sulfoxide photodeoxygenation was similar to a microwave discharge method for generating O(3P) atoms in the condensed phase (Zadok, E.; Rubinraut, S.; Mazur, Y. J. Org. Chem. 1987, 52, 385-90). Sulfoxide photodeoxygenation is a potentially clean method for O(3P) production compared to the microwave discharge method. With Argon purging of the sulfoxide sample before photolysis, the method can preclude a secondary oxidation process involving molecular oxygen. Our study focused on the results of oxidation products in the reaction of styrene, 3, and on the dependence of substrates that provided an opportunity to vary the electronic and steric effects. The sulfoxide photochemistry is rationalized with the primary formation of O(3P) in which a charge-transfer interaction between O(3P) and substrate precedes oxidation. Functionalization of hydrocarbons takes place under mild photolysis conditions of 1 and 2, which leads to an interesting possibility for the synthetic use of atomic oxygen, O(3P). Alkanes give principally alcohols. Alkenes give principally epoxides and ketones. For comparison, hydroxyl radicals are more reactive and less selective toward hydrocarbons compared to O(3P) atoms. On the other hand, O(3P) atoms balance reactivity and selectivity and involve the oxidation of inert alkanes typically inaccessible to peracid, dioxirane, ozone, and singlet molecular oxygen chemistry. The findings from this study may be useful to those interested in generating high-value oxygenated compounds from readily available petroleum components.

Journal Article↗