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

Toluene degradation occurred concomitantly with sulfate reduction in anaerobic microcosms inoculated with contaminated subsurface soil from an aviation fuel storage facility near the Patuxent River (Md.). Similar results were obtained for enrichment cultures in which toluene was the sole carbon source. Several lines of evidence suggest that toluene degradation was directly coupled to sulfate reduction in Patuxent River microcosms and enrichment cultures: (i) the two processes were synchronous and highly correlated, (ii) the observed stoichiometric ratios of moles of sulfate consumed per mole of toluene consumed were consistent with the theoretical ratio for the oxidation of toluene to CO2 coupled with the reduction of sulfate to hydrogen sulfide, and (iii) toluene degradation ceased when sulfate was depleted, and conversely, sulfate reduction ceased when toluene was depleted. Mineralization of toluene was confirmed in experiments with [ring-U-14C]toluene. The addition of millimolar concentrations of amorphous Fe(OH)3 to Patuxent River microcosms and enrichment cultures either greatly facilitated the onset of toluene degradation or accelerated the rate once degradation had begun. In iron-amended microcosms and enrichment cultures, ferric iron reduction proceeded concurrently with toluene degradation and sulfate reduction. Stoichiometric data and other observations indicate that ferric iron reduction was not directly coupled to toluene oxidation but was a secondary, presumably abiotic, reaction between ferric iron and biogenic hydrogen sulfide.
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PMID:Microbial degradation of toluene under sulfate-reducing conditions and the influence of iron on the process. 157 81

The reaction of a copper(II) or nickel(II) imidazolate complex (M[CBP-PHEN-4-CHO-Im]) with zinc(II)tetraphenylporphyrin (TPP) in toluene results in the formation of an imidazolate bridged heterobinuclear axial adduct. Conversion of the four-coordinated Zn(TPP) to the five-coordinated species is followed in the visible region between 700 and 500 nm. Isosbestic behavior is exhibited at 523, 556, 588, and 638 nm by solutions of Zn(TPP) to which varying amounts of the metal imidazolate complex are added, indicating the existence of an equilibrium between Zn(TPP) and its axial adduct. The products exhibit maxima beta and alpha bands at 566 and 606 nm, respectively, which are red-shifted from 548 and 588 nm for Zn(TPP) and yield epsilon alpha/epsilon beta ratios of 0.57 and 0.55 for the Ni(II) and Cu(II) adducts, respectively. The binding of the metal imidazolate complexes is thought to closely resemble that of N-methylimidazole, N-CH3Im, rather than imidazolate, owing to the close spectral similarities with the adduct of the former and significant differences from the latter. Formation constants were determined using the 548-nm beta band of Zn(TPP) in the 293-308 K range by the method of Rose and Drago. At 25 degrees C, K = 152,000 M-1 and 110,000 M-1 for the copper and nickel adducts, respectively. Comparison of these values to that of 54,100 M-1 for N-CH3Im indicates that the metal-imidazolate complexes are considerably more reactive. Van't Hoff plots for the two series are very similar with enthalpies of -41.9 and -43.3 kJ/mole respectively. The structural core of these complexes is similar to the imidazolate bridged model of cytochrome c oxidase in that they contain a metal imidazolate axially adducted to a metalloporphyrin.
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PMID:Imidazolate bridged heterobinuclear complexes of zinc(II)tetraphenylporphyrin. Modeling cytochrome c oxidase. 301 87

1. The efflux of [(14)C]urea was measured in micro-injected axons at 18 degrees C. A permeability constant for urea of (0.55 +/- 0.18) x 10(-6) cm/sec was calculated from these experiments.2. The influxes of urea, thiourea, ethylene glycol, urethane and toluene were measured in perfused axons at 18 +/- 1 degrees C. The permeability constants obtained from these determinations increased in the order listed, from (0.76 +/- 0.19) x 10(-6) cm/sec for urea to 0.80 x 10(-4) cm/sec for toluene.3. The influxes of tritiated water and sodium ions at 18 degrees C were measured in perfused axons. An average permeability of (0.78 +/- 0.22) x 10(-4) cm/sec for titriated water and an average influx of 23 +/- 6 p-mole/cm(2) sec for sodium were obtained.4. Lowering the temperature of the external sea-water bathing the axon from 18 to 5 degrees C produced a decrease of 12% in the permeability of toluene, 30% for tritiated water and urethane, 55% for ethylene glycol and urea and 60% for thiourea. There was a 50% reduction in the influx of sodium for this same temperature change.5. The results obtained with the effect of temperature on permeabilities suggest that the axonal membrane has a non-homogeneous composition. A model based on the assumption of structured aqueous channels in the membrane is postulated.
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PMID:Temperature dependence of non-electrolyte and sodium permeability in giant axon of squid. 550 Sep 90

A radioenzymatic assay for the measurement of histamine is described, based on the incubation of histamine in the presence of histamine-N-methyl-transferase from rat kidney and [3H-methyl]-S-adenosyl-L-methionine (sp act 15 Ci/mmol) in phosphate buffer, 0.05 mole/l, pH 7.9, at 37 degrees C for 60 min. The N-[3H]-methyl]histamine generated was selectively extracted into toluene/isoamyl alcohol (3:2) and the quantity of the tritium in the sample was determined by liquid- scintillation counting. As little as 1 nmol/l of histamine can be detected. The assay is specific, with no cross-reactivity noted for several compounds closely related to histamine. The assay was used to measure the released histamine of a group of allergic subjects following the incubation of their blood with various allergens. A good correlation was found between histamine release from whole blood and the response of skin mast cells to intradermal antigen administration.
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PMID:Development of a sensitive radioassay of histamine for in vitro allergy testing. 620 58

The T-for-H substitution reaction was studied in the recoil tritium reactions with toluene in C6F6-moderated systems. The moderator-free control experiment showed an approximately uniform labeling in the aromatic ring, with a slightly enhanced reactivity in the ortho- and para-positions (o: 41%, m: 38%, p: 21%) and showed a preference for ring tritiation over methyl group tritiation (23 relative to the corresponding ring assumed as a standard (= 100)). The addition of hexafluorobenzene progressively changed the uniform distribution to a marked ortho- and para-orientation and decreased the relative tritium activity of the methyl group. If the C6F6/PhCH3 mole ratio is 204, the tritium distribution in the ring is o: 53%, m: 22%, p: 25% and the methyl group activity is reduced to 2. The data show the existence of the threshold energy of side chain tritiation and that the selective aromatic ring tritiation is given by increasing contribution of the reactions of tritium atoms having lower energy than the threshold energy.
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PMID:The reactions of recoil tritium atoms with toluene in the C6F6-moderated systems. 651 48

Recoil tritium reactions in the aromatic ring were investigated with toluene and benzonitrile in the moderator-free and the C6F6-moderated systems in terms of the intramolecular tritium distribution, the relative tritiation rate, and the isotope effect in toluene. The reactions free from hexafluorobenzene are in essential agreement with non-selective nature shown in hot atom reactions. The addition of the moderator to the systems changes more markedly the uniform labeling to o,p-orientation in toluene than in benzonitrile, and the 1.17 PhCH3/PhCN tritiation rate (in PhCH3-d8/PhCN, 0.942) to the 1.89 PhCH3/PhCN one (in PhCH3-d8/PhCN, 1.51) when the mole ratio of C6F6/substrate is about 100. These findings agree with the electrophilic nature of the tritium at lower energies. The H/D isotope effect in the moderated system is given as 1.89/1.51 or 1.25 and is substantially the same as that (1.24) in the moderator-free system.
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PMID:Reactions of recoil tritium atoms with toluene and benzonitrile. 652 54

The effect of modification of carboxylic groups of phenylalanyl-tRNA synthetase by p-toluene sulfonate N-cyclohexyl-N'-beta-(4-methylmorpholine) ethylcarbodiimide (CMEC) on the activity of the enzyme was investigated. It was shown that modification of two moles of carboxylic groups per mole of the enzymes leads to the diminution of negative charge of the enzyme and to inactivation in ATP-[32P]PPi-exchange and aminoacylation reactions. The inactivation is completely reversed by mild alkaline hydrolysis. ATP in concentration 2 X 10(-4) M partially protects the enzyme against inactivation, protective effect being stimulated by Mg2+ and 0.4-0.7 moles of carboxylic groups per mole of the enzyme are protected against inactivation is observed although the depth of modification is increased. Other substrates do not have protective effect. Modification of the enzyme by CMEC increases Kdiss value of [14C]-Phe-tRNA enzyme complex and Km value for tRNAPhe in aminoacylation by factor of three. Vmax for all substrates in both aminoacylation and leads to 40% increase of Hill's coefficient for ATP in ATP-[32P]PPi-exchange reaction but not in aminoacylation. The carboxylic groups modified by CMEC are assumed to take part in ATP recognition and in catalysis of the ATP conversion and in catalysis of transfer of activated amino acid residues on tRNA.
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PMID:[Role of the carboxylic groups in interaction of phenylalanyl-tRNA synthetase with substrates]. 703 45

A procedure has been developed for measuring the steady state rate of permeation of commercial solvents through living human skin. To get the most consistent results, it was necessary with some solvents to normalize the solvent permeation rate of a given skin sample with its [3H]water permeation rate. For other solvents this was not necessary, so the un-normalized data were used. High [3H]water permeation rate also was used as a criterion for "defective" skin samples that gave erroneous permeability rates, especially for solvents having slow permeability. The linearity of the steady state data was characterized by calculation of the "percent error of the slope." The following permeability rates (g/m2h) of single solvents were measured: dimethyl sulfoxide (DMSO), 176; N-methyl-2-pyrrolidone, 171; dimethyl acetamide, 107; methyl ethyl ketone, 53; methylene chloride, 24; [3H]water, 14.8; ethanol, 11.3; butyl acetate, 1.6; gamma-butyrolactone, 1.1; toluene, 0.8; propylene carbonate, 0.7; and sulfolane, 0.2. The effect of [3H]water saturation on the shape of the presteady state portion of the permeation curve was determined and found to be very dependent on the solvent. The permeability of mixtures of DMSO and octyl acetate were measured. No octyl acetate was detected and the permeability of DMSO was proportional to its mole fraction in the mixture. The effect of two hours of solvent exposure on the viability of skin (based on DNA synthesis) was measured and found to be very dependent on the solvent.
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PMID:Permeability of commercial solvents through living human skin. 761 4

This research evaluated the effect of the polarity of a second vapor on the adsorption of a polar and a nonpolar vapor using the Wheeler model. To examine the effect of polarity, it was also necessary to observe the effect of component boiling point. The 1% breakthrough time (1% tb), kinetic adsorption capacity (W(e)), and rate constant (kv) of the Wheeler model were determined for vapor challenges on carbon beds for both p-xylene and pyrrole (referred to as test vapors) individually, and in equimolar binary mixtures with the polar and nonpolar vapors toluene, p-fluorotoluene, o-dichlorobenzene, and p-dichlorobenzene (referred to as probe vapors). Probe vapor polarity (0 to 2.5 Debye) did not systematically alter the 1% tb, W(e), or kv of the test vapors. The 1% tb and W(e) for test vapors in binary mixtures can be estimated reasonably well, using the Wheeler model, from single-vapor data (1% tb +/- 30%, W(e) +/- 20%). The test vapor 1% tb depended mainly on total vapor concentration in both single and binary systems. W(e) was proportional to test vapor fractional molar concentration (mole fraction) in mixtures. The kv for p-xylene was significantly different (p < or = 0.001) when compared according to probe boiling point; however, these differences were apparently of limited importance in estimating 1% tb for the range of boiling points tested (111 to 180 degrees C). Although the polarity and boiling point of chemicals in the range tested are not practically important in predicting 1% tb with the Wheeler model, an effect due to probe boiling point is suggested, and tests with chemicals of more widely ranging boiling point are warranted. Since the 1% tb, and thus, respirator service life, depends mainly on total vapor concentration, these data underscore the importance of taking into account the presence of other vapors when estimating respirator service life for a vapor in a mixture.
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PMID:The effect of vapor polarity and boiling point on breakthrough for binary mixtures on respirator carbon. 876

A novel sulfate-reducing bacterium isolated from fuel-contaminated subsurface soil, strain PRTOL1, mineralizes toluene as the sole electron donor and carbon source under strictly anaerobic conditions. The mineralization of 80% of toluene carbon to CO2 was demonstrated in experiments with [ring-U-14C]toluene; 15% of toluene carbon was converted to biomass and nonvolatile metabolic by-products, primarily the former. The observed stoichiometric ratio of moles of sulfate consumed per mole of toluene consumed was consistent with the theoretical ratio for mineralization of toluene coupled with the reduction of sulfate to hydrogen sulfide. Strain PRTOL1 also transforms o- and p-xylene to metabolic products when grown with toluene. However, xylene transformation by PRTOL1 is slow relative to toluene degradation and cannot be sustained over time. Stable isotope-labeled substrates were used in conjunction with gas chromatography-mass spectrometry to investigate the by-products of toluene and xylene metabolism. The predominant by-products from toluene, o-xylene, and p-xylene were benzylsuccinic acid, (2-methylbenzyl)succinic acid, and 4-methylbenzoic acid (or p-toluic acid), respectively. Metabolic by-products accounted for nearly all of the o-xylene consumed. Enzyme assays indicated that acetyl coenzyme A oxidation proceeded via the carbon monoxide dehydrogenase pathway. Compared with the only other reported toluene-degrading, sulfate-reducing bacterium, strain PRTOL1 is distinct in that it has a novel 16S rRNA gene sequence and was derived from a freshwater rather than marine environment.
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PMID:Isolation and characterization of a novel toluene-degrading, sulfate-reducing bacterium. 891 80


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