Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: CAS:7782-44-7 (oxygen)
 369,292 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

This paper describes the preparation of an organic charge transfer complex (CTC) based printable enzyme electrode. CTC crystals were prepared by mixing TCNQ powder with TTF solution (in acetonitrile). Glucose oxidase (GOD) was adsorbed at the CTC crystal surface in a monolayer. A printable paste was prepared by mixing GOD-absorbed crystals with a binder and a solvent. This paste was applied to an electrode cavity and vacuum dried. A thin layer of gelatin was cast on the paste filled dried electrode, and cross-linked with glutaraldehyde in the dry condition. The sensors were fixed in a flow injection system, and continuously polarized at 0.15 V and 37 degrees C, and the samples were automatically injected every 30 min. The developed sensors produced a huge response current with an extended linear range of detection (0-100 mM) and the response was unaffected by the presence of normal oxygen in the buffer solution. The sensor showed excellent stability. The performance of the sensors was significantly influenced by the binder used.
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PMID:Organic charge transfer complex based printable biosensor. 889 26

A HPLC method with coulometric detection has been established to carry out the separation of the three nitrofuran derivatives, nitrofurantoin, furazolidone and furaltadone. A Nova-Pak C18 column (150 x 3.9 mm) and a Coulochem II detector from ESA have been used. After obtaining the hydrodynamic curves of the three compounds in the porous graphite electrode a potential of -600 mV was selected as the working potential. The influence of other variables such as mobile phase composition and flow-rate were studied. The mobile phase considered as an optimum was acetonitrile-0.1 M aqueous solution of sodium perchlorate (28:72), with 0.5% glacial acetic acid. The oxygen of the mobile phase was removed with a vacuum system on-line and a nitrogen stream was used to remove the oxygen of the samples. The calibration graphs and the detection limits were established. The method proposed was used, with good results, for the determination of the three compounds in milk.
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PMID:Determination of nitrofurantoin, furazolidone and furaltadone in milk by high-performance liquid chromatography with electrochemical detection. 909 99

The reaction of cholesterol with superoxide anion was investigated in aprotic (dry) and in protic (aqueous) conditions. Superoxide anion was produced by electro-chemical reduction of molecular oxygen in a solution of 0.1 M tetrabutylammonium bromide in acetonitrile. The cholesterol and cholesterol oxidation products, 7-ketocholesterol, 7 alpha-hydroxycholesterol, 7 beta-hydroxycholesterol and 25-hydroxycholesterol were measured by high performance liquid chromatography using a mu-Porasil normal phase column and a UV detector. Cholesterol triol, 5 alpha and 5 beta cholesterol epoxides were measured by capillary gas chromatography. None of these cholesterol oxidation products was detected from the reaction of cholesterol with superoxide anion in aprotic conditions. This indicates that cholesterol was not oxidized by direct attack of superoxide anion. When 4% water (v/v) was added to the aprotic reaction mixture, to induce the dismutation of superoxide anions and the production of hydroxy free radicals, it was found that cholesterol was not oxidized by the active oxygen species thus produced. The effects of hydrogen peroxide, on the reaction of cholesterol with superoxide anion in the protic condition was also investigated. When hydrogen peroxide was added to superoxide anion in aqueous solution, only 7-ketocholesterol, 7 alpha-hydroxycholesterol, 7 beta-hydroxycholesterol were formed from cholesterol.
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PMID:The effect of superoxide anion in the production of seven major cholesterol oxidation products in aptoric and protic conditions. 913 79

The potential for electron transfer quenching of rose bengal triplet (3RB2-) to compete with energy transfer quenching by oxygen was evaluated. Rate constants for oxidative and reductive quenching were measured in buffered aqueous solution, acetonitrile and in small unilamellar liposomes using laser flash photolysis. Biologically relevant quenchers were used that varied widely in structure, reduction potential and charge. Radical ion yields (phi i) were measured by monitoring the absorption of the rose bengal semireduced (RB.3-) and semioxidized (RB.-) radicals. The results in solution were analyzed as a function of the free energy for electron transfer (delta G) calculated using the Weller equation including electrostatic terms. Exothermic oxidative quenching was about 10-fold faster than exothermic reductive quenching in aqueous solution. The quenching rate constants decreased as delta G approached zero in both aqueous and acetonitrile solution. Exceptions to these generalizations were observed that could be rationalized by specific steric or electrostatic effects or by a change in mechanism. The results suggest that electron transfer reactions with some potential quenchers in cells could compete with formation of singlet oxygen [O2(1 delta g)]. Values of phi i were generally greater for reductive quenching and, for oxidative quenching, greater in acetonitrile than in buffer. Electron transfer quenching of 3RB2- in liposomes, below the phase transition temperature was slower than in solution for both lipid-soluble and water-soluble quenchers indicating that these reactions may not compete with formation of O2(1 delta g) during cell photosensitization.
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PMID:Electron transfer quenching of the rose bengal triplet state. 923 Jul

Induction of phase 2 detoxication enzymes [e.g., glutathione transferases, epoxide hydrolase, NAD(P)H: quinone reductase, and glucuronosyltransferases] is a powerful strategy for achieving protection against carcinogenesis, mutagenesis, and other forms of toxicity of electrophiles and reactive forms of oxygen. Since consumption of large quantities of fruit and vegetables is associated with a striking reduction in the risk of developing a variety of malignancies, it is of interest that a number of edible plants contain substantial quantities of compounds that regulate mammalian enzymes of xenobiotic metabolism. Thus, edible plants belonging to the family Cruciferae and genus Brassica (e.g., broccoli and cauliflower) contain substantial quantities of isothiocyanates (mostly in the form of their glucosinolate precursors) some of which (e.g., sulforaphane or 4-methylsulfinylbutyl isothiocyanate) are very potent inducers of phase 2 enzymes. Unexpectedly, 3-day-old sprouts of cultivars of certain crucifers including broccoli and cauliflower contain 10-100 times higher levels of glucoraphanin (the glucosinolate of sulforaphane) than do the corresponding mature plants. Glucosinolates and isothiocyanates can be efficiently extracted from plants, without hydrolysis of glucosinolates by myrosinase, by homogenization in a mixture of equal volumes of dimethyl sulfoxide, dimethylformamide, and acetonitrile at -50 degrees C. Extracts of 3-day-old broccoli sprouts (containing either glucoraphanin or sulforaphane as the principal enzyme inducer) were highly effective in reducing the incidence, multiplicity, and rate of development of mammary tumors in dimethylbenz(a)anthracene-treated rats. Notably, sprouts of many broccoli cultivars contain negligible quantities of indole glucosinolates, which predominate in the mature vegetable and may give rise to degradation products (e.g., indole-3-carbinol) that can enhance tumorigenesis. Hence, small quantities of crucifer sprouts may protect against the risk of cancer as effectively as much larger quantities of mature vegetables of the same variety.
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PMID:Broccoli sprouts: an exceptionally rich source of inducers of enzymes that protect against chemical carcinogens. 929 17

Surface enhanced Raman (SER) spectra of 2- and 3-formylthiophenes (2FT and 3FT) in silver colloids are compared with their normal Raman spectra in bulk and in acetonitrile solution. Experimental results indicate adsorption of 2FT on metal surface through the sulfur and the oxygen atoms with the ring plane vertical to the metal surface, whereas the ring plane of the 3FT molecule is inclined to the surface. Moreover, the SER spectrum of 2FT molecule predicts the existence of syn-form of this molecule in the adsorbed state because of large enhancement of the carbonyl stretching mode. Concentration dependence of relative enhancement infers the monolayer formation on metal surface at a specific concentration, implying strong evidence of chemisorption of the adsorbates. The excitation profile of C identical withC symmetric stretching mode of 2FT suggests classical plasmon resonance as the main contributor to surface enhancement. Copyright 1997 Academic Press. Copyright 1997Academic Press
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PMID:Surface-Enhanced Raman Spectroscopic Study of Isomeric Formylthiophenes in Silver Colloid 934 29

Bovine insulin was reacted at pH 4.0 with submolar amounts of hypochlorite. At least one molecule of insulin was modified per two molecules of hypochlorite added, as estimated by HPLC of native and modified insulin. About 5% of the hypochlorite-modified insulin reacted with dinitrophenylhydrazine (DNPH), a reagent which specifically labels carbonyl groups. The major DNPH-labeled product was isolated from the native insulin on reverse-phase HPLC, using trifluoroacetic acid/water/acetonitrile gradients. The UV spectrum of the major peak on the HPLC diode-array detector was representative of DNPH adducts, with lambda max = 365 nm. Several methods, including total amino acid analysis, tryptic digestion, and collision-induced dissociation-electrospray MS, indicate that the major carbonyl in the DNPH-labeled product was on the amino-terminal phenylalanine of the insulin B-chain. Amino acid analysis indicated that tyrosine was also degraded by hypochlorite, but we could not detect a carbonyl group formed at tyrosine. These findings suggest that the terminal amino groups of proteins are highly vulnerable to carbonyl formation during hypochlorite attack. The use of relatively low amounts of active oxygen species (such as hypochlorite), followed by chromatographic isolation of the protein labeled with a carbonyl-specific reagent, can be a useful approach to the study of reactive sites on proteins.
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PMID:Formation of carbonyls during attack on insulin by submolar amounts of hypochlorite. 957 Aug 50

As the continuation of the work on the antioxidant properties of furan derivatives, we have studied hydroxyl radical (OH.) scavenging activity of dimethylfuran (DMF) and diphenylfuran (DPF), which are well-known as an effective scavenger of singlet oxygen, by an ESR spin trapping technique. The incubation mixture of 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as a spin trapping agent with FE2+ and H202 in 50% acetonitrile aqueous solution gave 1:2:2:1 line signals characteristic of DMPO-OH spin adduct. The additions of furan derivatives to the incubation mixture decreased the intensity of the DMPO-OH spin adduct signal in a dose-dependent manner. The activities of furan derivatives were in the order of DMF > DPF > furan. The decrease in the intensity of the signals was not due to the inhibition of OH. generating system itself and the destruction of the spin adduct by furan derivatives. By comparison with the common OH. scavengers, DMF and DPF were found to scavenge OH. more effectively than dimethylsulfoxide and mannitol. These results indicate that DMF and DPF can act as a OH. scavenger as well as a singlet oxygen scavenger.
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PMID:[Scavenging activity of furan derivatives against hydroxyl radical generated by Fenton system]. 962 58

Reversed-phase HPLC conditions for the separation of 4-(2-pyridyl)-1-piperazinethiocarboxylic acid 2-[1-(pyridyl)-ethylidene]hydrazide dihydrochloride (NSC 348977, I), a synthetic thiosemicarbazone with antitumor activity, from mouse plasma have been investigated. Following denaturization and precipitation of the spiked plasma with acetonitrile, an aliquot of the supernatant was diluted with aqueous buffer and subjected to analysis on a Nova-Pak C18 column (150 x 3.9 mm I.D.) by isocratic elution with 50 mM aqueous potassium phosphate buffer (pH 6.8, containing 1 mM EDTA)-acetonitrile (60:40, v/v). The column effluent was monitored for UV absorption at 310 nm. Problems identified in the sample preparation and separation of I include sensitivity to oxygen, light, non-neutral pH and the presence of metal ions. These factors were seen to adversely influence sample recovery, and attempts were made to find conditions which minimize their effects.
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PMID:Reversed-phase high-performance liquid chromatography of 4-(2-pyridyl)-1-piperazinethiocarboxylic acid 2-[1-(pyridyl)ethylidene]hydrazide dihydrochloride (NSC 348977), a synthetic thiosemicarbazone with antitumor activity. 965 65

The photochemical and photophysical properties of nabumetone (4-[6-methoxy-2-naphthyl]-2-butanone) were examined employing conventional and time-resolved spectroscopic techniques. The naphthalene-like nabumetone triplet is formed with 29% efficiency in acetonitrile. Singlet oxygen formation was also detected in this solvent with a phi delta value of 0.19. A naphthalene-like radical cation absorption, formed via biphotonic processes, was also detected. The reactivity of both the triplet and radical cation of nabumetone toward different substrates was examined. The photochemical properties of nabumetone are compared with those of naproxen, a structurally related acidic nonsteroidal anti-inflammatory drug. For these two anti-inflammatory agents, a type II photosensitization process is most likely responsible for their phototoxicity.
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PMID:Characterization of the transient intermediates generated from the photoexcitation of nabumetone: a comparison with naproxen. 982 93


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