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Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Fundamental kinetic studies on the reduction of nitrate, nitrite, and their mixtures were performed with a strain of Pseudomonas denitrificans (ATCC 13867). Methanol served as the carbon source and was supplied in excess (2:1 mole ratio relative to nitrate and/or nitrite). Nitrate and nitrite served as terminal electron acceptors as well as sources of nitrogen for biomass synthesis. The results were explained under the assumption that respiration is a growth-associated process. It was found that the sequence of complete reduction of nitrate to nitrogen gas is via nitrite and nitrous oxide.It was found that the specific growth rate of the biomass on either nitrate or nitrite follows Andrews inhibitory kinetics and nitrite is more inhibitory than nitrate. It was also found that the culture has severe maintenance requirements which can be described by Herbert's model, i.e., by self-oxidation of portions of the biomass. The specific maintenance rates at 30 degrees C and pH 7.1 were found to be equal to about 28% of the maximum specific growth rate on nitrate and 23% of the maximum specific growth rate on nitrite. Nitrate and nitrite were found to be involved in a cross-inhibitory noncompetitive kinetic interaction. The extent of this interaction is negligible when the presence of nitrite is low but is considerable when nitrite is present at levels above 15 mg/L.Studies on the effect of temperature have shown that the culture cannot grow at temperatures above 40 degrees C. The optimal temperature for nitrate or nitrite reduction was found to be about 38 degrees C. Using an Arrhenius expression to describe the effect of temperature on the specific growth rates, it was found that the activation energy for the use of nitrate by the culture is 8.6 kcal/mol and 7.21 kcal/mol for nitrite. Arrhenius-type expressions were also used in describing the effect of temperature on each of the parameters appearing in the specific growth rate expressions. Studies on the effect of pH at 30 degrees C have shown that the culture reduces nitrate optimally at a pH between 7.4 and 7.6, and nitrite at a pH between 7.2 and 7.3. (c) 1995 John Wiley & Sons, Inc.
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PMID:Fundamental denitrification kinetic studies with Pseudomonas denitrificans. 1862 64

The mixture of two surfactants (C12EO10-CTAB and C12EO10-SDS) forms lyotropic liquid-crystalline (LLC) mesophases with [Zn(H2O)6](NO3)2 in the presence of a minimum concentration of 1.75 H2O per C12EO10. The metal ion/C12EO10 mole ratio can be increased up to 8.0, which is a record high metal ion density in an LLC mesophase. The metal ion concentration can be increased in the medium by increasing the CTAB/C12EO10 or SDS/C12EO10 mole ratio at the expense of the stability of the LLC mesophase. The structure and some thermal properties of the new mesophase have been investigated using XRD, POM, FTIR, and Raman techniques.
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PMID:Lyotropic liquid-crystalline mesophases of [Zn(H2O)6](NO3)2-C12EO10-CTAB-H2O and [Zn(H2O)6](NO3)2-C12EO10-SDS-H2O systems. 1872 33

Ethylammonium nitrate (EAN) is composed of C(2)H(5)NH(3)(+) and NO(3)(-) ions, which behave as an acid and a base, respectively. The ionic liquid thus involves small amounts of C(2)H(5)NH(2) and HNO(3) molecules owing to proton transfer from C(2)H(5)NH(3)(+) to NO(3)(-). The equilibrium constant K(s) (= [C(2)H(5)NH(2)][HNO(3)]), which corresponds to the autoprotolysis constant of water, was obtained to be ca. 10(-10) mol(2) dm(-6) by potentiometry using an ion-selective field-effect transistor and hydrogen electrodes at 298 K. The value indicates that C(2)H(5)NH(2) and HNO(3) molecules of ca. 10(-5) mol dm(-3) are involved in neat EAN. On the other hand, in an EAN-water mixture, a water molecule behaves as a base. The apparent pK(s) value was determined in EAN-water mixtures of various solvent compositions. Interestingly, the pK(s) value is remained at 10.5 in mixtures over the range of an EAN mole fraction of 0.05-0.9. The value is close to the pK(a) of C(2)H(5)NH(2), or the acid-dissociation constant of C(2)H(5)NH(3)(+), in aqueous solution. This implies that the reaction C(2)H(5)NH(3)(+) + H(2)O --> C(2)H(5)NH(2) + H(3)O(+) is responsible for the pK(s) over a wide range of solvent composition. The pK(s) value in neat EAN is thus slightly smaller than that in the mixtures, implying that H(3)O(+) is a stronger acid than HNO(3) in an EAN solution, unlike water.
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PMID:Acidity and basicity of aqueous mixtures of a protic ionic liquid, ethylammonium nitrate. 1884 98

An injection calorimeter used for analytical and thermochemical purposes is described. Amounts of sodium fluoride between 6 and 8 mg are determined with an error of +/-0.04 mg. The calorimeter is also used in determining DeltaH for the precipitation of lead chloro-fluoride from water solutions with an ionic strength of 1M. DeltaH = 36.6 +/- 0.3 kJ mole . Quantitative analysis is made by flow microcalorimeter with amounts of sodium fluoride between 40 and 400mug and an error of +/-4 mug. An ion-exchange system for separation of fluoride from phosphate, sulphate, nitrate and chloride is also described.
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PMID:Enthalpimetric determination of fluoride. 1896 Jul 93

Simple microgasometric and gravimetric methods for the determination of the nitrate and nitrite groups are described. These are based on reduction with formic acid whereby one mole of nitrous oxide and four moles of carbon dioxide are simultaneously liberated per two moles of nitrate; two moles of nitrous oxide and six moles of carbon dioxide are liberated per seven moles of nitrite. Nitrous oxide is measured gasometrically and carbon dioxide gravimetrically. Results accurate to +/- 0.2% absolute are obtained for both nitrate and nitrite.
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PMID:Microdetermination of nitrates and nitrites-III Gasometric and gravimetric methods based on reduction with formic acid. 1896 Aug 75

A simple, selective and accurate method has been described for the rapid micro and submicro determination of organic nitrates and nitramines. It is based on reaction with mercury-sulphuric acid mixture for 5 min at room temperature followed by potentiometric titration of the mercurous ions released, a solid-state iodide-sensitive electrode being used. Three equivalents of potassium iodide as titrant are consumed per mole of nitrate or nitramine group. The results obtained, with sample sizes ranging from 1.0 to 50 mumole, are precise to +/- 0.2% and the average recovery is 99%. None of the other nitrogenous functional groups responds to this reaction.
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PMID:Ion-selective electrodes in organic functional group analysis: microdetermination of nitrates and nitramines with use of the iodide electrode. 1896 74

A sensitive spectrophotometric method based on the extraction of a uranium-benzoate-Malachite Green complex by chlorobenzene is described. The absorption maximum is at 635 nm and the molar absorptivity is 8.3 x 10(4) 1 mole(-1), cm(-1). A preliminary separation of uranium by extraction with methyl isobutyl ketone from acid-deficient aluminium nitrate solution is used to avoid interferences. An aliquot of the extract is then diluted with chlorobenzene and shaken with benzoate buffer containing Malachite Green (MG). The method has been applied for the determination of uranium in a synthetic leach solution. The complex extracted is probably [MG(2)(C(6)H(5)COO)(3)][MG(+)].
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PMID:Extractive spectrophotometric determination of uranium with Malachite Green. 1896 80

The thermometric titration of Th(IV) in the presence of neutral sodium salts, sulphuric acid or acetic acid with EDTA has been studied. The effect of each on the observed heat values for the titration is discussed. For sodium perchlorate media, DeltaH values of -9 and -21 kJ/mole have been estimated for the formation of the Th(IV)-EDTA chelate at mu --> 0 and mu = 0.5 (NaClO(4)), respectively. The -DeltaH values increase steadily with increase in concentration of sodium perchlorate up to at least 3M. For the titration of Th(IV) in the presence of a large excess of sodium nitrate the use of sodium iodide as a masking reagent has been examined: large amounts of Bi and Cu(II) are masked and a masking effect is observed for small amounts of Ni.
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PMID:Thermometric titration of thorium with EDTA in the presence of large excess of neutral sodium salts. 1896 12

The acidity constants of benzidine (Bz) in aqueous solutions determined potentiometrically at 25 degrees were K(a1) = (1.11 +/- 0.08) x 10(-5), K(a2) = (1.45 +/- 0.12) x 10(-4). The apparent mixed constants in 0.1M sodium nitrate are K(a1) = (5.37 +/- 0.28) x 10(-6) and K(a2) = (1.14 +/- 0.09) x 10(-4). The ultraviolet spectra were recorded as a function of pH and analysed with these constants to obtain the absorption spectra of H(2)Bz(2+), HBz(+) and Bz; the corresponding wavelengths of maximal absorption are 247, 273 and 278 nm, and molar absorptivities 1.63 x 10(4), 1.76 x 10(4) and 2.26 x 10(4) 1.mole(-1).cm(-1).
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PMID:Acidity constants of benzidine in aqueous solutions. 1896 55

A simple and precise preconcentration technique, based on collecting a precipitate on a membrane filter and dissolving the filter and precipitate in an organic solvent, has been applied to the spectrophotometric determination of trace sulphate in rain and snow. The sulphate is precipitated with 2-aminoperimidine and the resulting compound is dissolved in nitric acid, made alkaline with sodium hydroxide and then adsorbed on tetradecyldimethylbenzylammonium nitrate. The precipitate is then collected on a membrane filter and both precipitate and filter are dissolved in dimethylsulphoxide (DMSO). The absorbance of the DMSO solution is measured at 550 nm against a reagent blank. The molar absorptivity is 2.1 x 10(4) 1 . mole(-1) . cm(-1) and the coefficient of variation for six measurements is < 1.5%. The detection limit (S/N = 3) is 0.06 mug of sulphate in 5 ml of sample solution.
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PMID:Spectrophotometric determination of trace sulphate in rain and snow after preconcentration with 2-aminoperimidine on a membrane filter. 1896 91


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