(n.) A gaseous element, colorless, tasteless, and odorless, the lightest known substance, being fourteen and a half times lighter than air (hence its use in filling balloons), and over eleven thousand times lighter than water. It is very abundant, being an ingredient of water and of many other substances, especially those of animal or vegetable origin. It may by produced in many ways, but is chiefly obtained by the action of acids (as sulphuric) on metals, as zinc, iron, etc. It is very inflammable, and is an ingredient of coal gas and water gas. It is standard of chemical equivalents or combining weights, and also of valence, being the typical monad. Symbol H. Atomic weight 1.
Example Sentences:
(1) The hypothesis that proteins are critical targets in free radical mediated cytolysis was tested using U937 mononuclear phagocytes as targets and iron together with hydrogen peroxide to generate radicals.
(2) It has been conformed that catalase from bovine liver eliminates only the pro R hydrogen atom from ethanol.
(3) We investigated the possible contribution made by oropharyngeal microfloral fermentation of ingested carbohydrate to the generation of the early, transient exhaled breath hydrogen rise seen after carbohydrate ingestion.
(4) Hydrogen isotope effects on these mutants indicate that MotA catalyzes proton transfer.
(5) Excessive accumulation of hydrogen ions in the brain may play a pivotal role in initiating the necrosis seen in infarction and following hyperglycemic augmentation of ischemic brain damage.
(6) Studies were conducted in isolated, buffer-perfused rat lungs to determine if prostaglandin (PG) E1 attenuated pulmonary edema provoked by hydrogen peroxide (H2O2).
(7) All N and O atoms except N(3) and O(4') participate in a three-dimensional hydrogen-bonding system.
(8) Both adiphenine.HCl and proadifen.HCl form more stable complexes, suggesting that hydrogen bonding to the carbonyl oxygen by the hydroxyl-group on the rim of the CD ring could be an important contributor to the complexation.
(9) Control mutant S38N has stability essentially the same as that of wild-type lysozyme but hydrogen bonding similar to that of the stabilizing mutant S38D.
(10) High intensity ultrasound also enhances the heterogeneous catalysis of alkene hydrogenation by Ni powders.
(11) An atmosphere of hydrogen eliminates this inhibition in the hydrogenase-containing T. foetus but not in E. invadens which lacks the enzyme.
(12) Vanadate-dependent oxidation of either pyridine nucleotide was inhibited by the addition of either superoxide dismutase or catalase, indicating that both superoxide and hydrogen peroxide may be intermediates in the process.
(13) Our findings suggest that (a) the inclusion of a liquid meal provides a reproducible method of measuring orocaecal transit using the lactulose hydrogen breath test, (b) rapid small bowel transit in thyrotoxicosis may be one factor in the diarrhoea which is a feature of the disease and (c) if altered gut transit is the cause of sluggish bowel habit in hypothyroidism, delay in the colon, and not small bowel, is likely to be responsible.
(14) Stepwise hydrogenation of metal tetradehydrocorrin salts (10 double bonds) yields a series of macrocycles containing 9, 8, 7, 6 and 5 double bonds and conditions necessary to obtain corrins have been established.
(15) For dipeptides containing the amino terminal residues glycine, alanine and phenylalanine, abstraction of the hydrogen from the carbon adjacent to the peptide nitrogen was the major process leading to the spin-adducts.
(16) (7) The first-order radical transformation rates are independent of the (initial) concentration of N3 or peptide and unaffected by urea (as a modifier of hydrogen bond structures).
(17) Intermolecular contacts occur in both oligomers in the minor groove: in the B form through twisted guanine-guanine hydrogen bonding, and in the Z form through base-base stacking and the water network.
(18) Equilibrium-partitioning measurements indicate that the relative affinities of different probes for PC-rich vesicles, in competition with HODMA or DOTAP vesicles, increase with increasing hydrogen-bonding capacity of the probe headgroup in the order PC less than N,N-dimethyl PE less than N-methyl PE less than PE approximately phosphatidyl-2-amino-1-propanol.
(19) When tissue metabolism was irreversibly inhibited by exposure to formaldehyde, hydrogen ion concentration and pCO2 were significantly decreased in the mucosal side of the chamber compared with the viable gall bladder.
(20) Based on the refined atomic coordinates of the tRNAphe in the orthorhombic crystal, on the recent advances in the distance dependence of the ring-current magnetic field effects and on the adopted values for the isolated hydrogen-bonded NH resonances, a computed spectrum consisting of 23 protons was constructed.
Hydroquinone
Definition:
(n.) A white crystalline substance, C6H4(OH)2, obtained by the reduction of quinone. It is a diacid phenol, resembling, and metameric with, pyrocatechin and resorcin. Called also dihydroxy benzene.
Example Sentences:
(1) These series were prepared by oxidation of the new hydroquinone precursors.
(2) In the liver, the major site of benzene metabolism, benzene is converted by a cytochrome P-450-mediated pathway to phenol, the major metabolite, and the secondary metabolites, hydroquinone and catechol.
(3) Here we report that phenol hydroxylation to hydroquinone is also catalyzed by human myeloperoxidase in the presence of a superoxide anion radical generating system, hypoxanthine and xanthine oxidase.
(4) We tested nine (cadmium chloride, chloral hydrate, colchicine, diazepam, econazole nitrate, hydroquinone, pyrimethamine, thiabendazole, thimerosal) of the 10 known or suspected spindle poisons of the coordinated programme to study aneuploidy induction sponsored by the Commission of the European Communities using Saccharomyces cerevisiae D61.M (mitotic chromosomal malsegregation system).
(5) Comparison of these two activities for both the quinone and hydroquinone showed that the hydroquinone form had superior activities.
(6) 2-Chloro-1,4-dimethoxybenzene (IV) is oxidized by lignin peroxidase to generate 2,5-dimethoxy-1,4-benzoquinone (V), which is reduced to 2,5-dimethoxy-1,4-hydroquinone (VI).
(7) Bis(alkylthio)quinones 4a-d and 5a-d, and corresponding hydroquinones 9b-d exhibited high activities both in vitro and in vivo.
(8) Glutathione (GSH) conjugates of 2-bromohydroquinone are more difficult to oxidize than the parent hydroquinone.
(9) The activity of cytochrome P-450 reductase, which reduces quinones to hydroquinones in the estrogen redox cycle, was 6-fold higher in liver than in kidney of both control and estrogen-treated animals.
(10) The hydrolytic products of lignins, humic acids and industrial waste including hydroquinone, catechol, resorcinol, pyrogallol and 1,2,4-benzenetriol are widely distributed in water sources.
(11) Treatment with hydroquinone and 1,2,4,-benzenetriol produced DNA adducts not detected after treatment with either metabolite alone.
(12) The changes were also prevented by 0.02% hydroquinone.
(13) Compounds such as butylated hydroxytoluene, catechol, chlorobenzene, hydroquinone, potassium chloride, phenol, cis-stilbene, trans-stilbene, and toluene did not elicit positive responses in either strain.
(14) Catechol given alone was not inhibitory but when phenol was added to catechol, erythropoiesis was suppressed, as observed for the phenol and hydroquinone combination.
(15) Ethoxyquin, propyl gallate and butylated hydroquinone only partially inhibited rTNF-alpha-induced cytotoxicity, while the antioxidants butylated hydroxytoluene (BHT), alpha-tocopherol, ascorbic acid and thiodipropionic acid had minimal effects.
(16) Hydroquinone is estimated to be nonmutagenic by the Ames test but induces chromosome aberrations or karyotypic effects in eucaryotic cells.
(17) This observation prompted us to study in a well-defined in vitro system the possible allosteric interaction between the propeptide binding site and the vitamin K hydroquinone binding site on carboxylase.
(18) The present data indicate that hydroquinone and 1,2,4-benzenetriol in the presence of copper ions can lead to the formation of reactive hydroxyl radicals which can release TBAR from glutamate or DNA.
(19) In Tris-washed spinach chloroplasts (incapable of O2 evolution), the chlorophyll a fluorescence transient in the presence of various artificial electron donors (hydroquinone, diphenylcarbazide, MnCl2 and NH2OH) and in the absence of bicarbonate ions shows a rapid initial rise; the addition of 10 mM NaHCO3 restores the transient to one characteristic of normal chloroplast.
(20) The relative toxic potencies of the hydroquinone and quinone metabolites of AMAP were comparable to that of NAPQI, and do not readily explain the marked difference between the cytotoxic effects of AMAP and APAP.