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

Freeze-thawed rat liver mitochondria were extensively washed with potassium phosphate, pH 7.5, and the residue was extracted with 10 mM potassium phosphate, pH 7.5, 1% (w/v) sodium cholate, 0.5 M KCl. The four beta-oxidation enzyme activities of the washes and the last extract were assayed with substrates of various carbon chain lengths. Our data suggest that the last extract contains a novel acyl-CoA dehydrogenase and long-chain 3-hydroxyacyl-CoA dehydrogenase. A novel acyl-CoA dehydrogenase was purified. The molecular masses of the native enzyme and the subunit were estimated to be 150 and 71 kDa, respectively. One mole of enzyme contained 2 mole of FAD. These properties and immunochemical properties of the enzyme differed from those of three other acyl-CoA dehydrogenases: short-, medium-, and long-chain acyl-CoA dehydrogenases. Carbon chain length specificity of the enzyme differed from that of other acyl-CoA dehydrogenases. The enzyme was active toward CoA esters of long- and very-long-chain fatty acids, but not toward those of medium- and short-chain fatty acids. The specific enzyme activity was greater than 10 times that of long-chain acyl-CoA dehydrogenase when palmitoyl-CoA was used as substrate. We propose the name "very-long-chain acyl-CoA dehydrogenase" for this enzyme.
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PMID:Novel fatty acid beta-oxidation enzymes in rat liver mitochondria. I. Purification and properties of very-long-chain acyl-coenzyme A dehydrogenase. 173 Jun 32

Carbon exchange in the Krebs cycle may result in underestimation of substrate oxidation measured with 13C-labeled substrates, since carbon labeled in position 2 of acetyl-coenzyme A (CoA) could be incorporated into glucose (via gluconeogenesis) and glutamine. Five healthy volunteers were therefore infused with [1-13C] and [2-13C] acetate at a rate of 0.5 micromol x kg(-1) x min(-1) for 165 minutes on two different occasions in randomized order. Whole body acetate turnover did not differ between the two tracers: 7.9+/-0.3 and 7.5+/-0.6 micromol x kg(-1) x min(-1) (nonsignificant [NS]) for [1-13C] and [2-13C] acetate, respectively. Isotopic 13C enrichment was higher in expired CO2 (0.177+/-0.021 v 0.089+/-0.009 atom percent excess [APE], P < .01) and lower in glucose (0.074+/-0.017 v0.291+/-0.061 mole percent excess [MPE], P < .01) for [1-13C] acetate compared with [2-13C] acetate, respectively, at the end of the infusions. Glutamine isotopic enrichment was slightly but not significantly higher when infusing [1-13C] acetate versus [2-13C] acetate (0.348+/-0.038 v0.495+/-0.069 MPE, NS, respectively). At the end of the experiment, the recovery of 13CO2 from [1-13C] acetate was 44.8%+/-2.7%, and from [2-13C] acetate, 22.6%+/-1.3%. A significant correlation was observed between the differences in 13C enrichment of CO2 for the two tracers and glucose (deltaCO2=0.424 x deltaglucose + 0.001, R2=.9856, P=.0007) or glutamine (deltaCO2=0.621 x deltaglutamine + 0.004, R2=.9573, P=.0038) during the infusion. These results suggest that (1) although gluconeogenesis appears to be more responsible than glutamine for the differential recovery of [2-13C] versus [1-13C] acetate, other secondary pathways are probably also implicated; and (2) different recovery correction factors should be applied when measuring substrate oxidation with a stable isotope tracer depending on the expected position of 13C in acetyl-CoA.
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PMID:Role of glucose and glutamine synthesis in the differential recovery of 13CO2 from infused [2-13C] versus [1-13C] acetate. 959 45

Dissolved organic carbon (DOC) concentrations in five shallow (< 20 m) and three deeper wells (27 to 30 m) in the Eocene Yegua Formation (Brazos County in east-central Texas) ranged from 92 to 500 microns. Characterization of high, intermediate, and low molecular weight DOC fractions (HMW > 3000 amu, IMW 1000 to 3000 amu, and LMW 500 to 1000 amu) and combined neutral sugar analyses provide information on organic matter sources in the Yegua aquifers. Combined neutral sugars ranged in concentration from 0.6 to 2.7 mumol/L and comprised 0.8% to 6.7% of DOC in ground water. Glucose was the most abundant neutral sugar, followed by xylose and galactose, arabinose, mannose, rhamnose, and fucose. These combined neutral sugars were more diagenetically altered in shallow, oxic ground water as indicated by high mole % fucose + rhamnose and low neutral sugar yield. The precursors for neutral sugars are most probably angiosperm leaves, which show a similar distribution pattern of neutral sugars. Ground water DOC was depleted in 13C relative to soil-zone organic matter (OM) (-16@1000 to -19@1000). The delta 13C values of bulk DOC and HMW DOC ranged from -24@1000 to -32@1000, whereas LMW and IMW DOC ranged from -32@1000 to -34@1000 and -16@1000 to -28@1000, respectively. This variability in delta 13C values is probably related to microbial processes and selective preservation of OM. Carbon isotope analyses in bulk and different molecular weight DOC fractions imply a predominantly C3 OM source and a low contribution of soil-zone OM to DOC.
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PMID:Characterization and origin of dissolved organic carbon in Yegua ground water in Brazos County, Texas. 1155 55

Carbon-13 nuclear magnetic resonance (NMR) spectroscopy was employed to investigate alterations in hepatic carbohydrate metabolism in Meriones unguiculatus infected with Echinococcus multilocularis. Following portal vein injections of an equimolar mixture of [1,2-13C2]acetate and [3-13C]lactate, perchloric acid extracts of the livers were prepared and NMR spectra obtained. Isotopomer analysis using glutamate resonances in these spectra showed that the relative contributions of endogenous and exogenous substrates to the acetyl-CoA entering the tricarboxylic acid cycle differed significantly between infected and control groups. The mole fraction of acetyl-CoA that was derived from endogenous, unlabelled sources (F(U)) was 0.50 +/- 0.10 in controls compared to 0.34 +/- 0.04 in infected animals. However, the fraction of acetyl-CoA derived from [3-13C]lactate (FLL) was larger in livers of infected animals than those from controls with values of 0.27 +/- 0.04 and 0.18 +/- 0.04, respectively. Similarly, the fraction of acetyl-CoA derived from [1,2-13C2]acetate (FLA) was larger in livers of infected animals compared to those in controls; the fractions were 0.38 +/- 0.01 and 0.32 +/- 0.07, respectively. The ratio of FLA:FLL was significantly smaller in the infected group with a value of 1.42 +/- 0.18 compared to 1.74 +/- 0.09 for the controls. These results indicate that alveolar hydatid disease has a pronounced effect on the partitioning of substrates within the pathways of carbohydrate metabolism in the host liver.
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PMID:Effect of Echinococcus multilocularis on the origin of acetyl-coA entering the tricarboxylic acid cycle in host liver. 1201 93

A carbon mass balance methodology employing minimal measurements was applied to heterotrophic and photoheterotrophic marine bacteria grown under constant dilution and exposed to 12-h intervals of light or darkness. Carbon mass balance calculations using measurements taken every 3 h closed to within 93-103% using dissolved organic carbon, biomass carbon and CO2 production data only, indicating that background interference from dissolved inorganic carbon variations in the amended seawater medium was not significant. Neither strain was observed to sustain a net CO2 fixation using paramagnetic measurement of oxygen uptake rates (OUR), indicating a need for more sensitive on-line measurement techniques for OUR. Photoheterotrophic growth demonstrated lower carbon-mole biomass yields (0.41+/-0.026 vs. 0.64+/-0.013 mol mol(-1)) despite higher specific glucose uptake rates (0.025 vs. 0.02 mol mol(-1) h(-1)), suggesting that bioreactor-based study of marine bacteria can present growth modes that are different from those encountered in the marine environment.
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PMID:Carbon mass balance methodology to characterize the growth of pigmented marine bacteria under conditions of light cycling. 1566 59

An autonomous instrument based on off-axis integrated cavity output spectroscopy has been developed and successfully deployed for measurements of carbon monoxide in the troposphere and tropopause onboard a NASA DC-8 aircraft. The instrument (Carbon Monoxide Gas Analyzer) consists of a measurement cell comprised of two high-reflectivity mirrors, a continuous-wave quantum-cascade laser, gas sampling system, control and data-acquisition electronics, and data-analysis software. CO measurements were determined from high-resolution CO absorption line shapes obtained by tuning the laser wavelength over the R(7) transition of the fundamental vibration band near 2172.8 cm(-1). The instrument reports CO mixing ratio (mole fraction) at a 1-Hz rate based on measured absorption, gas temperature, and pressure using Beer's Law. During several flights in May-June 2004 and January 2005 that reached altitudes of 41,000 ft (12.5 km), the instrument recorded CO values with a precision of 0.2 ppbv (1-s averaging time) and an accuracy limited by the reference CO gas cylinder (uncertainty < 1.0%). Despite moderate turbulence and measurements of particulate-laden airflows, the instrument operated consistently and did not require any maintenance, mirror cleaning, or optical realignment during the flights.
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PMID:Cavity-enhanced quantum-cascade laser-based instrument for carbon monoxide measurements. 1627 May 60

Methanogenic enrichments catabolizing 13 mM phenylacetate or 4 mM phenol were established at 37 degrees C, using a 10% inoculum from a municipal anaerobic digester. By using agar roll tubes of the basal medium plus 0.1% yeast extract-25 mM fumarate, a hydrogenotrophic lawn of Wolinella succinogenes and phenol or phenylacetate, strains P-2 and PA-1, respectively, were isolated in coculture with W. succinogenes. With the lawn deleted, PA-1 was isolated in pure culture. Strain P-2 is apparently a new species of anaerobic, motile, gram-negative, spindle-shaped, small rod that as yet has been grown only in coculture with W. succinogenes. It used phenol, hydrocinnamate, benzoate, and phenylacetate as energy sources. Product recovery by the coculture, per mole of phenol and 4.4 mol of fumarate used, included 2.03, 0.12, 0.08, and 3.23 mol, respectively, of acetate, propionate, butyrate, and succinate. Carbon recovery was 75% and H recovery was 80%, although CO(2) and a few other possible products were not determined. That P-2 is an obligate proton-reducing acetogen and possible pathways for its degradation of phenol are discussed. Strain PA-1 is apparently a new species of anaerobic, motile, relatively small, gram-negative rod. It utilized compounds such as phenylacetate, hydrocinnamate, benzoate, phenol, resorcinol, gallate, 4-aminophenol, 2-aminobenzoate, pyruvate, Casamino Acids, and aspartate as energy sources in coculture with W. succinogenes. Per mole of phenylacetate and 1.44 mol of fumarate used, 1.04, 0.53, and 0.78 mol of acetate, propionate, and succinate, respectively, were recovered from the coculture. Only about 50% of the carbon and H were recovered. In coculture with Methanospirillum hungatei, 0.96 mol of acetate and 0.25 mol of methane were recovered per mol of pyruvate used; 0.90 mol of acetate and 0.33 mol of methane, per mol of fumarate used; 0.93 mol of acetate and 0.54 mol of methane, per mol of aspartate used; and 1.71 mol of acetate and 0.57 mol of methane, per mol of glucose used. Carbon and H recoveries, assuming CO(2) and ammonia were produced in stoichiometric amounts, were 97 and 98% for pyruvate, 72.5 and 82% for fumarate, 96.5 and 98% for aspartate, and 61.8 and 76% for glucose. No explanation such as contamination could be found for the fact that the coculture PA-1 plus Wolinella sp. did not use glucose; after growth with M. hungatei on pyruvate, however, the latter coculture used glucose. The PA-1 pure culture produced 0.86 mol of propionate per mol of succinate used during growth. PA-1 produced a small amount of H(2). Strain PA-1 is the most versatile anaerobic bacterium yet known that catabolizes monobenzenoids in the absence of electron acceptors such as sulfate or nitrate.
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PMID:PA-1, a Versatile Anaerobe Obtained in Pure Culture, Catabolizes Benzenoids and Other Compounds in Syntrophy with Hydrogenotrophs, and P-2 plus Wolinella sp. Degrades Benzenoids. 1634 52

The anaerobic photodissimilation of acetate by Chlamydomonas reinhardii F-60 adapted to a hydrogen metabolism was studied utilizing manometric and isotopic techniques. The rate of photoanaerobic (N(2)) acetate uptake was approximately 20 mumoles per milligram chlorophyll per hour or one-half that of the photoaerobic (air) rate. Under N(2), cells produced 1.7 moles H(2) and 0.8 mole CO(2) per mole of acetate consumed. Gas production and acetate uptake were inhibited by monofluoroacetic acid (MFA), 3-(3',4'-dichlorophenyl)-1,1-dimethylurea (DCMU) and by H(2). Acetate uptake was inhibited about 50% by 5% H(2) (95% N(2)). H(2) in the presence of MFA or DCMU stimulated acetate uptake and the result was interpreted to indicate a transition from oxidative to reductive metabolism. Carbon-14 from both [1-(14)C]- and [2-(14)C]acetate was incorporated under N(2) or H(2) into CO(2), lipids, and carbohydrates. The methyl carbon of acetate accumulated principally (75-80%) in the lipid and carbohydrate fractions, whereas the carboxyl carbon contributed isotope primarily to CO(2) (56%) in N(2). The presence of H(2) caused a decrease in carbon lost from the cell as CO(2) and a greater proportion of the acetate was incorporated into lipid. The results support the occurrence of anaerobic and light-dependent citric acid and glyoxylate cycles which affect the conversion of acetate to CO(2) and H(2) prior to its conversion to cellular material.
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PMID:Fermentative Metabolism of Chlamydomonas reinhardii: III. Photoassimilation of Acetate. 1666 85

Carbon-dioxide-expanded liquids, which are mixtures of organic liquids and compressed CO2, are novel media used in chemical processing. The authors present a molecular simulation study of the transport properties of liquid mixtures formed by acetonitrile and carbon dioxide, in which the CO2 mole fraction is adjusted by changing the pressure, at a constant temperature of 298 K. They report values of translational diffusion coefficients, rotational correlation times, and shear viscosities of the liquids as function of CO2 mole fraction. The simulation results are in good agreement with the available experimental data for the pure components and provide interesting insights into the largely unknown properties of the mixtures, which are being recognized as important novel materials in chemical operations. We find that the calculated quantities exhibit smooth variation with composition that may be represented by simple model equations. The translational and rotational diffusion rates increase with CO2 mole fraction for both the acetonitrile and carbon dioxide components. The shear viscosity decreases with increasing amount of CO2, varying smoothly between the values of pure acetonitrile and pure carbon dioxide. Our results show that adjusting the amount of CO2 in the mixture allows the variation of transport rates by a factor of 3-4 and liquid viscosity by a factor of 8. Thus, the physical properties of the mixture may be tailored to the desired range by changes in the operating conditions of temperature and pressure.
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PMID:Transport properties of CO2-expanded acetonitrile from molecular dynamics simulations. 1732 20

The effect of solvent participation on the ligand-to-metal charge transfer (LMCT, L-->Co(III)) reduction of the of Co(III)(en)(2)Br(RC(6)H(4)NH(2))(2+) where R=m-OCH(3), p-F, H, m-CH(3), p-CH(3,)p-OC(2)H(5) and p-OCH(3) were examined in aqueous 2-methyl-2-propanol (Bu(t)OH) solutions. The change in the reduction behavior of Co(III) centre was also examined through cyclic voltammetric studies. The observed reduction in quantum yield due to LMCT excitation can mainly be accounted using linear solvation energy relationship (LSER) comprising model correlation equations. These consist of empirical parameters such as Grunwald-Winstein's solvent ionizing power, Y, Dimroth-Richardt's solvent micro-polarity parameter, E(T)(N), Gutmann's donor number, DN(N), along with Kamlet-Taft's solvatochromic parameters (hydrogen bond acceptor acidity/basicity alpha/beta and solvent dipolarity/polarizability, pi*). The origin of solvent effect is found to be due to microscopic interaction between the solvent donor and the nitrogen-bound hydrogen of the ligand. Cyclic voltammograms show an irreversible reduction of Co(III) in DMF using Glassy Carbon Electrode, GCE, the redox peaks for the aniline complexes appear at -0.20 and 0.525V. Irradiation of the complexes with UV light (lambda=254nm) in binary mixtures produce Co(II)(aq) and the concentration of this species are highly dependent on x(alc) (x(alc)=mole fraction of alcohol). The observed quantum yield (logPhi(Co(II))) is found to be linearly related to mole fraction of organic co-solvent added in the mixture, therefore, logPhi(Co(II))=26.41 x 10(-2) when x(2)=0.0094 and 43.75 x 10(-2) when x(2)=0.076 for a typical complex Co(III)(en)(2)Br(p-OCH(3)C(6)H(4)NH(2))(2+) in aqueous 2-methyl-2-propanol at 300K. Cyclic voltammetry and LSER analyses illustrate the variation of reduction property of Co(III) by the aryl ligand and homogeneous solvation of the excited state of the complex Co(III)(en)(2)Br(RC(6)H(4)NH(2))(2+) in H(2)O/Bu(t)OH mixtures.
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PMID:Homogeneous solvation controlled photoreduction of cobalt(III) complexes in aqueous 2-methyl-2-propanol solutions linear solvation energy relationship and cyclic voltammetric analyses. 1769 8


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