Sustainable Thorium Nuclear Fuel Cycles: A Comparison of Intermediate and Fast Neutron Spectrum Systems

DOE PAGES

Brown, Nicholas R.; Powers, Jeffrey J.; Feng, B.; ...

2015-05-21

This paper presents analyses of possible reactor representations of a nuclear fuel cycle with continuous recycling of thorium and produced uranium (mostly U-233) with thorium-only feed. The analysis was performed in the context of a U.S. Department of Energy effort to develop a compendium of informative nuclear fuel cycle performance data. The objective of this paper is to determine whether intermediate spectrum systems, having a majority of fission events occurring with incident neutron energies between 1 eV and 10 5 eV, perform as well as fast spectrum systems in this fuel cycle. The intermediate spectrum options analyzed include tight latticemore » heavy or light water-cooled reactors, continuously refueled molten salt reactors, and a sodium-cooled reactor with hydride fuel. All options were modeled in reactor physics codes to calculate their lattice physics, spectrum characteristics, and fuel compositions over time. Based on these results, detailed metrics were calculated to compare the fuel cycle performance. These metrics include waste management and resource utilization, and are binned to accommodate uncertainties. The performance of the intermediate systems for this selfsustaining thorium fuel cycle was similar to a representative fast spectrum system. However, the number of fission neutrons emitted per neutron absorbed limits performance in intermediate spectrum systems.« less

Unsuspected task for an old team: succinate, fumarate and other Krebs cycle acids in metabolic remodeling.

PubMed

Bénit, Paule; Letouzé, Eric; Rak, Malgorzata; Aubry, Laetitia; Burnichon, Nelly; Favier, Judith; Gimenez-Roqueplo, Anne-Paule; Rustin, Pierre

2014-08-01

Seventy years from the formalization of the Krebs cycle as the central metabolic turntable sustaining the cell respiratory process, key functions of several of its intermediates, especially succinate and fumarate, have been recently uncovered. The presumably immutable organization of the cycle has been challenged by a number of observations, and the variable subcellular location of a number of its constitutive protein components is now well recognized, although yet unexplained. Nonetheless, the most striking observations have been made in the recent period while investigating human diseases, especially a set of specific cancers, revealing the crucial role of Krebs cycle intermediates as factors affecting genes methylation and thus cell remodeling. We review here the recent advances and persisting incognita about the role of Krebs cycle acids in diverse aspects of cellular life and human pathology. Copyright © 2014 Elsevier B.V. All rights reserved.

Krebs cycle intermediates regulate DNA and histone methylation: epigenetic impact on the aging process.

PubMed

Salminen, Antero; Kauppinen, Anu; Hiltunen, Mikko; Kaarniranta, Kai

2014-07-01

Many aging theories have proposed that mitochondria and energy metabolism have a major role in the aging process. There are recent studies indicating that Krebs cycle intermediates can shape the epigenetic landscape of chromatin by regulating DNA and histone methylation. A growing evidence indicates that epigenetics plays an important role in the regulation of healthspan but also is involved in the aging process. 2-Oxoglutarate (α-ketoglutarate) is a key metabolite in the Krebs cycle but it is also an obligatory substrate for 2-oxoglutarate-dependent dioxygenases (2-OGDO). The 2-OGDO enzyme family includes the major enzymes of DNA and histone demethylation, i.e. Ten-Eleven Translocation (TETs) and Jumonji C domain containing (JmjC) demethylases. In addition, 2-OGDO members can regulate collagen synthesis and hypoxic responses in a non-epigenetical manner. Interestingly, succinate and fumarate, also Krebs cycle intermediates, are potent inhibitors of 2-OGDO enzymes, i.e. the balance of Krebs cycle reactions can affect the level of DNA and histone methylation and thus control gene expression. We will review the epigenetic mechanisms through which Krebs cycle intermediates control the DNA and histone methylation. We propose that age-related disturbances in the Krebs cycle function induce stochastic epigenetic changes in chromatin structures which in turn promote the aging process. Copyright © 2014 Elsevier B.V. All rights reserved.

Crassulacean acid metabolism-cycling in Euphorbia milii.

PubMed

Herrera, Ana

2013-01-01

Crassulacean acid metabolism (CAM) occurs in many Euphorbiaceae, particularly Euphorbia, a genus with C3 and C4 species as well. With the aim of contributing to our knowledge of the evolution of CAM in this genus, this study examined the possible occurrence of CAM in Euphorbia milii, a species with leaf succulence and drought tolerance suggestive of this carbon fixation pathway. Leaf anatomy consisted of a palisade parenchyma, a spongy parenchyma and a bundle sheath with chloroplasts, which indicates the possible functioning of C2 photosynthesis. No evidence of nocturnal CO2 fixation was found in plants of E. milii either watered or under drought; watered plants had a low nocturnal respiration rate (R). After 12 days without watering, the photosynthetic rate (P N) decreased 85 % and nocturnal R was nearly zero. Nocturnal H(+) accumulation (ΔH(+)) in watered plants was 18 ± 2 (corresponding to malate) and 18 ± 4 (citrate) μmol H(+) (g fresh mass)(-1). Respiratory CO2 recycling through acid synthesis contributed to a night-time water saving of 2 and 86 % in watered plants and plants under drought, respectively. Carbon isotopic composition (δ(13)C) was -25.2 ± 0.7 ‰ in leaves and -24.7 ± 0.1 ‰ in stems. Evidence was found for the operation of weak CAM in E. milii, with statistically significant ΔH(+), no nocturnal CO2 uptake and values of δ(13)C intermediate between C3 and constitutive CAM plants; ΔH(+) was apparently attributable to both malate and citrate. The results suggest that daily malate accumulation results from recycling of part of the nocturnal respiratory CO2, which helps explain the occurrence of an intermediate value of leaf δ(13)C. Euphorbia milii can be considered as a CAM-cycling species. The significance of the operation of CAM-cycling in E. milii lies in water conservation, rather than carbon acquisition. The possible occurrence of C2 photosynthesis merits research.

Teaching about citric acid cycle using plant mitochondrial preparations: Some assays for use in laboratory courses*.

PubMed

Vicente, Joaquim A F; Gomes-Santos, Carina S S; Sousa, Ana Paula M; Madeira, Vítor M C

2005-03-01

Potato tubers and turnip roots were used to prepare purified mitochondria for laboratory practical work in the teaching of the citric acid cycle (TCA cycle). Plant mitochondria are particularly advantageous over the animal fractions to demonstrate the TCA cycle enzymatic steps, by using simple techniques to measure O(2) consumption and transmembrane potential (ΔΨ). The several TCA cycle intermediates induce specific enzyme activities, which can be identified by respiratory parameters. Such a strategy is also used to evidence properties of the TCA cycle enzymes: ADP stimulation of isocitrate dehydrogenase and α-ketoglutarate dehydrogenase; activation by citrate of downstream oxidation steps, e.g. succinate dehydrogenase; and regulation of the activity of isocitrate dehydrogenase by citrate action on the citrate/isocitrate carrier. Furthermore, it has been demonstrated that, in the absence of exogenous Mg(2+) , isocitrate-dependent respiration favors the alternative oxidase pathway, as judged by changes of the ADP/O elicited by the inhibitor n-propyl galate. These are some examples of assays related with TCA cycle intermediates we can use in laboratory courses. Copyright © 2005 International Union of Biochemistry and Molecular Biology, Inc.

Thermal analysis of heat and power plant with high temperature reactor and intermediate steam cycle

NASA Astrophysics Data System (ADS)

Fic, Adam; Składzień, Jan; Gabriel, Michał

2015-03-01

Thermal analysis of a heat and power plant with a high temperature gas cooled nuclear reactor is presented. The main aim of the considered system is to supply a technological process with the heat at suitably high temperature level. The considered unit is also used to produce electricity. The high temperature helium cooled nuclear reactor is the primary heat source in the system, which consists of: the reactor cooling cycle, the steam cycle and the gas heat pump cycle. Helium used as a carrier in the first cycle (classic Brayton cycle), which includes the reactor, delivers heat in a steam generator to produce superheated steam with required parameters of the intermediate cycle. The intermediate cycle is provided to transport energy from the reactor installation to the process installation requiring a high temperature heat. The distance between reactor and the process installation is assumed short and negligable, or alternatively equal to 1 km in the analysis. The system is also equipped with a high temperature argon heat pump to obtain the temperature level of a heat carrier required by a high temperature process. Thus, the steam of the intermediate cycle supplies a lower heat exchanger of the heat pump, a process heat exchanger at the medium temperature level and a classical steam turbine system (Rankine cycle). The main purpose of the research was to evaluate the effectiveness of the system considered and to assess whether such a three cycle cogeneration system is reasonable. Multivariant calculations have been carried out employing the developed mathematical model. The results have been presented in a form of the energy efficiency and exergy efficiency of the system as a function of the temperature drop in the high temperature process heat exchanger and the reactor pressure.

Evolution of the enzymes of the citric acid cycle and the glyoxylate cycle of higher plants. A case study of endosymbiotic gene transfer.

PubMed

Schnarrenberger, Claus; Martin, William

2002-02-01

The citric acid or tricarboxylic acid cycle is a central element of higher-plant carbon metabolism which provides, among other things, electrons for oxidative phosphorylation in the inner mitochondrial membrane, intermediates for amino-acid biosynthesis, and oxaloacetate for gluconeogenesis from succinate derived from fatty acids via the glyoxylate cycle in glyoxysomes. The tricarboxylic acid cycle is a typical mitochondrial pathway and is widespread among alpha-proteobacteria, the group of eubacteria as defined under rRNA systematics from which mitochondria arose. Most of the enzymes of the tricarboxylic acid cycle are encoded in the nucleus in higher eukaryotes, and several have been previously shown to branch with their homologues from alpha-proteobacteria, indicating that the eukaryotic nuclear genes were acquired from the mitochondrial genome during the course of evolution. Here, we investigate the individual evolutionary histories of all of the enzymes of the tricarboxylic acid cycle and the glyoxylate cycle using protein maximum likelihood phylogenies, focusing on the evolutionary origin of the nuclear-encoded proteins in higher plants. The results indicate that about half of the proteins involved in this eukaryotic pathway are most similar to their alpha-proteobacterial homologues, whereas the remainder are most similar to eubacterial, but not specifically alpha-proteobacterial, homologues. A consideration of (a) the process of lateral gene transfer among free-living prokaryotes and (b) the mechanistics of endosymbiotic (symbiont-to-host) gene transfer reveals that it is unrealistic to expect all nuclear genes that were acquired from the alpha-proteobacterial ancestor of mitochondria to branch specifically with their homologues encoded in the genomes of contemporary alpha-proteobacteria. Rather, even if molecular phylogenetics were to work perfectly (which it does not), then some nuclear-encoded proteins that were acquired from the alpha

Lipotoxicity in steatohepatitis occurs despite an increase in tricarboxylic acid cycle activity

PubMed Central

Patterson, Rainey E.; Kalavalapalli, Srilaxmi; Williams, Caroline M.; Nautiyal, Manisha; Mathew, Justin T.; Martinez, Janie; Reinhard, Mary K.; McDougall, Danielle J.; Rocca, James R.; Yost, Richard A.; Cusi, Kenneth; Garrett, Timothy J.

2016-01-01

The hepatic tricarboxylic acid (TCA) cycle is central to integrating macronutrient metabolism and is closely coupled to cellular respiration, free radical generation, and inflammation. Oxidative flux through the TCA cycle is induced during hepatic insulin resistance, in mice and humans with simple steatosis, reflecting early compensatory remodeling of mitochondrial energetics. We hypothesized that progressive severity of hepatic insulin resistance and the onset of nonalcoholic steatohepatitis (NASH) would impair oxidative flux through the hepatic TCA cycle. Mice (C57/BL6) were fed a high-trans-fat high-fructose diet (TFD) for 8 wk to induce simple steatosis and NASH by 24 wk. In vivo fasting hepatic mitochondrial fluxes were determined by 13C-nuclear magnetic resonance (NMR)-based isotopomer analysis. Hepatic metabolic intermediates were quantified using mass spectrometry-based targeted metabolomics. Hepatic triglyceride accumulation and insulin resistance preceded alterations in mitochondrial metabolism, since TCA cycle fluxes remained normal during simple steatosis. However, mice with NASH had a twofold induction (P < 0.05) of mitochondrial fluxes (μmol/min) through the TCA cycle (2.6 ± 0.5 vs. 5.4 ± 0.6), anaplerosis (9.1 ± 1.2 vs. 16.9 ± 2.2), and pyruvate cycling (4.9 ± 1.0 vs. 11.1 ± 1.9) compared with their age-matched controls. Induction of the TCA cycle activity during NASH was concurrent with blunted ketogenesis and accumulation of hepatic diacylglycerols (DAGs), ceramides (Cer), and long-chain acylcarnitines, suggesting inefficient oxidation and disposal of excess free fatty acids (FFA). Sustained induction of mitochondrial TCA cycle failed to prevent accretion of “lipotoxic” metabolites in the liver and could hasten inflammation and the metabolic transition to NASH. PMID:26814015

The Path of Carbon in Photosynthesis VIII. The Role of Malic Acid

DOE R&D Accomplishments Database

Bassham, James A.; Benson, Andrew A.; Calvin, Melvin

1950-01-25

Malonate has been found to inhibit the formation of malic acid during short periods of photosynthesis with radioactive carbon dioxide. This result, together with studies which show the photosynthetic cycle to be operating normally at the same time, indicates that malic acid is not an intermediate in photosynthesis but is probably closely related to some intermediate of the cycle. Absence of labeled succinic and fumaric acids in these experiments, in addition to the failure of malonate to inhibit photosynthesis, precludes the participation of these acids as intermediates in photosynthesis.

Anaerobic carbon metabolism by the tricarboxylic acid cycle

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vanlerberghe, G.C.; Horsey, A.K.; Weger, H.G.

Nitrogen-limited cells of Selenastrum minutum (Naeg.) Collins are able to assimilate NH{sub 4}{sup +} in the dark under anaerobic conditions. Addition of NH{sub 4}{sup +} to anaerobic cells results in a threefold increase in tricarboxylic acid cycle (TCAC) CO{sub 2} efflux and an eightfold increase in the rate of anaplerotic carbon fixation via phosphoenspyruvate carboxylase. Both of these observations are consistent with increased TCAC carbon flow to supply intermediates for amino acid biosynthesis. Addition of H{sup 14}CO{sub 3}{sup {minus}} to anaerobic cells assimilating NH{sub 4}{sup +} results in the incorporation of radiolabel into the {alpha}-carboxyl carbon of glutamic acid. Incorporationmore » of radiolabel into glutamic acid is not simply a short-term phenomenon following NH{sub 4}{sup +} addition as the specific activity of glutamic acid increases over time. This indicates that this alga is able to maintain partial oxidative TCAC carbon flow while under anoxia to supply {alpha}ketoglutarate for glutamate production. During dark aerobic NH{sub 4}{sup +} assimilation, no radiolabel appears in fumarate or succinate and only a small amount occurs in malate. During anaerobic NH{sub 4}{sup +} assimilation, these metabolites contain a large proportion of the total radiolabel and radiolabel accumulates in succinate over time. Also, the ratio of dark carbon fixation to NH{sub 4}{sup +} assimilation is much higher under anaerobic than aerobic conditions. These observations suggest the operation of a partial reductive TCAC from oxaloacetic acid to malate, fumarate, and succinate. Such a pathway might contribute to redox balance in an anaerobic cell maintaining partial oxidative TCAC activity.« less

The Impact of a Participant-Based Accounting Cycle Course on Student Performance in Intermediate Financial Accounting I

ERIC Educational Resources Information Center

Siagian, Ferdinand T.; Khan, Mohammad

2016-01-01

The authors investigated whether students in an Intermediate Financial Accounting I course who took a 1-credit, participant-based accounting cycle course performed better than students who did not take the accounting cycle course. Results indicate a higher likelihood of earning a better grade for students who took the accounting cycle course even…

Evaluation of the efficacy of four weak acids as antifungal preservatives in low-acid intermediate moisture model food systems.

PubMed

Huang, Yang; Wilson, Mark; Chapman, Belinda; Hocking, Ailsa D

2010-02-01

The potential efficacy of four weak acids as preservatives in low-acid intermediate moisture foods was assessed using a glycerol based agar medium. The minimum inhibitory concentrations (MIC, % wt./wt.) of each acid was determined at two pH values (pH 5.0, pH 6.0) and two a(w) values (0.85, 0.90) for five food spoilage fungi, Eurotium herbariorum, Eurotium rubrum, Aspergillus niger, Aspergillus flavus and Penicillium roqueforti. Sorbic acid, a preservative commonly used to control fungal growth in low-acid intermediate moisture foods, was included as a reference. The MIC values of the four acids were lower at pH 5.0 than pH 6.0 at equivalent a(w) values, and lower at 0.85 a(w) than 0.90 a(w) at equivalent pH values. By comparison with the MIC values of sorbic acid, those of caprylic acid and dehydroacetic acid were generally lower, whereas those for caproic acid were generally higher. No general observation could be made in the case of capric acid. The antifungal activities of all five weak acids appeared related not only to the undissociated form, but also the dissociated form, of each acid.

Anaerobic Carbon Metabolism by the Tricarboxylic Acid Cycle 1

PubMed Central

Vanlerberghe, Greg C.; Horsey, Anne K.; Weger, Harold G.; Turpin, David H.

1989-01-01

Nitrogen-limited cells of Selenastrum minutum (Naeg.) Collins are able to assimilate NH4+ in the dark under anaerobic conditions. Addition of NH4+ to anaerobic cells results in a threefold increase in tricarboxylic acid cycle (TCAC) CO2 efflux and an eightfold increase in the rate of anaplerotic carbon fixation via phosphoenolpyruvate carboxylase. Both of these observations are consistent with increased TCAC carbon flow to supply intermediates for amino acid biosynthesis. Addition of H14CO3− to anaerobic cells assimilating NH4+ results in the incorporation of radiolabel into the α-carboxyl carbon of glutamic acid. Incorporation of radiolabel into glutamic acid is not simply a short-term phenomenon following NH4+ addition as the specific activity of glutamic acid increases over time. This indicates that this alga is able to maintain partial oxidative TCAC carbon flow while under anoxia to supply α-ketoglutarate for glutamate production. During dark aerobic NH4+ assimilation, no radiolabel appears in fumarate or succinate and only a small amount occurs in malate. During anaerobic NH4+ assimilation, these metabolites contain a large proportion of the total radiolabel and radiolabel accumulates in succinate over time. Also, the ratio of dark carbon fixation to NH4+ assimilation is much higher under anaerobic than aerobic conditions. These observations suggest the operation of a partial reductive TCAC from oxaloacetic acid to malate, fumarate, and succinate. Such a pathway might contribute to redox balance in an anaerobic cell maintaining partial oxidative TCAC activity. PMID:16667215

Impact of unusual fatty acid synthesis on futile cycling through beta-oxidation and on gene expression in transgenic plants.

PubMed

Moire, Laurence; Rezzonico, Enea; Goepfert, Simon; Poirier, Yves

2004-01-01

Arabidopsis expressing the castor bean (Ricinus communis) oleate 12-hydroxylase or the Crepis palaestina linoleate 12-epoxygenase in developing seeds typically accumulate low levels of ricinoleic acid and vernolic acid, respectively. We have examined the presence of a futile cycle of fatty acid degradation in developing seeds using the synthesis of polyhydroxyalkanoate (PHA) from the intermediates of the peroxisomal beta-oxidation cycle. Both the quantity and monomer composition of the PHA synthesized in transgenic plants expressing the 12-epoxygenase and 12-hydroxylase in developing seeds revealed the presence of a futile cycle of degradation of the corresponding unusual fatty acids, indicating a limitation in their stable integration into lipids. The expression profile of nearly 200 genes involved in fatty acid biosynthesis and degradation has been analyzed through microarray. No significant changes in gene expression have been detected as a consequence of the activity of the 12-epoxygenase or the 12-hydroxylase in developing siliques. Similar results have also been obtained for transgenic plants expressing the Cuphea lanceolata caproyl-acyl carrier protein thioesterase and accumulating high amounts of caproic acid. Only in developing siliques of the tag1 mutant, deficient in the accumulation of triacylglycerols and shown to have a substantial futile cycling of fatty acids toward beta-oxidation, have some changes in gene expression been detected, notably the induction of the isocitrate lyase gene. These results indicate that analysis of peroxisomal PHA is a better indicator of the flux of fatty acid through beta-oxidation than the expression profile of genes involved in lipid metabolism.

Quantitative importance of the pentose phosphate pathway determined by incorporation of 13C from [2-13C]- and [3-13C]glucose into TCA cycle intermediates and neurotransmitter amino acids in functionally intact neurons.

PubMed

Brekke, Eva M F; Walls, Anne B; Schousboe, Arne; Waagepetersen, Helle S; Sonnewald, Ursula

2012-09-01

The brain is highly susceptible to oxidative injury, and the pentose phosphate pathway (PPP) has been shown to be affected by pathological conditions, such as Alzheimer's disease and traumatic brain injury. While this pathway has been investigated in the intact brain and in astrocytes, little is known about the PPP in neurons. The activity of the PPP was quantified in cultured cerebral cortical and cerebellar neurons after incubation in the presence of [2-(13)C]glucose or [3-(13)C]glucose. The activity of the PPP was several fold lower than glycolysis in both types of neurons. While metabolism of (13)C-labeled glucose via the PPP does not appear to contribute to the production of releasable lactate, it contributes to labeling of tricarboxylic acid (TCA) cycle intermediates and related amino acids. Based on glutamate isotopomers, it was calculated that PPP activity accounts for ~6% of glucose metabolism in cortical neurons and ~4% in cerebellar neurons. This is the first demonstration that pyruvate generated from glucose via the PPP contributes to the synthesis of acetyl CoA for oxidation in the TCA cycle. Moreover, the fact that (13)C labeling from glucose is incorporated into glutamate proves that both the oxidative and the nonoxidative stages of the PPP are active in neurons.

Capillary electrophoretic study of dibasic acids of different structures: Relation to separation of oxidative intermediates in remediation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yu, Z.; Cocke, D.L.

Dicarboxylic acids are important in environmental chemistry because they are intermediates in oxidative processes involved in natural remediation and waste management processes such as oxidative detoxification and advanced oxidation. Capillary electrophoresis (CE), a promising technique for separating and analyzing these intermediates, has been used to examine a series of dibasic acids of different structures and conformations. This series includes malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, maleic acid, fumaric acid, phthalic acid, and trans, trans-muconic acid. The CE parameters as well as structural variations (molecular structure and molecular isomers, buffer composition, pH, applied voltage, injection mode, current,more » temperature, and detection wavelength) that affect the separations and analytical results have been examined in this study. Those factors that affect the separation have been delineated. Among these parameters, the pH has been found to be the most important, which affects the double-layer of the capillary wall, the electro-osmotic flow and analyte mobility. The optimum pH for separating these dibasic acids, as well as the other parameters are discussed in detail and related to the development of methods for analyzing oxidation intermediates in oxidative waste management procedures.« less

Inactivation of thiol-dependent enzymes by hypothiocyanous acid: role of sulfenyl thiocyanate and sulfenic acid intermediates

PubMed Central

Barrett, Tessa J.; Pattison, David I.; Leonard, Stephen E.; Carroll, Kate S.; Davies, Michael J.; Hawkins, Clare L.

2012-01-01

Myeloperoxidase (MPO) forms reactive oxidants including hypochlorous and hypothiocyanous acids (HOCl and HOSCN) under inflammatory conditions. HOCl causes extensive tissue damage and plays a role in the progression of many inflammatory-based diseases. Although HOSCN is a major MPO oxidant, particularly in smokers, who have elevated plasma thiocyanate, the role of this oxidant in disease is poorly characterized. HOSCN induces cellular damage by targeting thiols. However, the specific targets and mechanisms involved in this process are not well defined. We show that exposure of macrophages to HOSCN results in the inactivation of intracellular enzymes, including creatine kinase (CK) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH). In each case, the active-site thiol residue is particularly sensitive to oxidation, with evidence for reversible inactivation and the formation of sulfenyl thiocyanate and sulfenic acid intermediates, on treatment with HOSCN (less than fivefold molar excess). Experiments with DAz-2, a cell-permeable chemical trap for sulfenic acids, demonstrate that these intermediates are formed on many cellular proteins, including GAPDH and CK, in macrophages exposed to HOSCN. This is the first direct evidence for the formation of protein sulfenic acids in HOSCN-treated cells and highlights the potential of this oxidant to perturb redox signaling processes. PMID:22248862

Genotypic variability and genotype by environment interactions in oil and fatty acids in high, intermediate, and low oleic acid peanut genotypes.

PubMed

Singkham, Nattawut; Jogloy, Sanun; Kesmala, Thawan; Swatsitang, Prasan; Jaisil, Prasit; Puppala, Naveen

2010-05-26

Variability of genotype and genotype x environment (G x E) interactions for fatty acids are important to develop high-oleic types in peanut varietal improvement programs. The objective of this study was to determine the variation in fatty acid composition among peanut genotypes and G x E interactions of fatty acids in three groups of genotypes with high, intermediate, and low-oleic acid. Twenty-one genotypes were tested in three environments consisting of two rainy seasons and one dry season. The results indicated that G x E interactions were significant for biomass, pod yield, and harvest index and also for oleic, linoleic acids, and O/L ratio. G x E interactions were less important than genotypic main effect. For oleic acid, significant interactions were found in the intermediate and low-oleic groups only. Therefore, selection for high-oleic trait in peanut breeding programs should be effective.

Metabolism: Part II. The Tricarboxylic Acid (TCA), Citric Acid, or Krebs Cycle.

ERIC Educational Resources Information Center

Bodner, George M.

1986-01-01

Differentiates the tricarboxylic acid (TCA) cycle (or Krebs cycle) from glycolysis, and describes the bridge between the two as being the conversion of pyruvate into acetyl coenzyme A. Discusses the eight steps in the TCA cycle, the results of isotopic labeling experiments, and the net effects of the TCA cycle. (TW)

Impact of Unusual Fatty Acid Synthesis on Futile Cycling through β-Oxidation and on Gene Expression in Transgenic Plants1[w

PubMed Central

Moire, Laurence; Rezzonico, Enea; Goepfert, Simon; Poirier, Yves

2004-01-01

Arabidopsis expressing the castor bean (Ricinus communis) oleate 12-hydroxylase or the Crepis palaestina linoleate 12-epoxygenase in developing seeds typically accumulate low levels of ricinoleic acid and vernolic acid, respectively. We have examined the presence of a futile cycle of fatty acid degradation in developing seeds using the synthesis of polyhydroxyalkanoate (PHA) from the intermediates of the peroxisomal β-oxidation cycle. Both the quantity and monomer composition of the PHA synthesized in transgenic plants expressing the 12-epoxygenase and 12-hydroxylase in developing seeds revealed the presence of a futile cycle of degradation of the corresponding unusual fatty acids, indicating a limitation in their stable integration into lipids. The expression profile of nearly 200 genes involved in fatty acid biosynthesis and degradation has been analyzed through microarray. No significant changes in gene expression have been detected as a consequence of the activity of the 12-epoxygenase or the 12-hydroxylase in developing siliques. Similar results have also been obtained for transgenic plants expressing the Cuphea lanceolata caproyl-acyl carrier protein thioesterase and accumulating high amounts of caproic acid. Only in developing siliques of the tag1 mutant, deficient in the accumulation of triacylglycerols and shown to have a substantial futile cycling of fatty acids toward β-oxidation, have some changes in gene expression been detected, notably the induction of the isocitrate lyase gene. These results indicate that analysis of peroxisomal PHA is a better indicator of the flux of fatty acid through β-oxidation than the expression profile of genes involved in lipid metabolism. PMID:14671017

pKa cycling of the general acid/base in glycoside hydrolase families 33 and 34.

PubMed

Yu, Haibo; Griffiths, Thomas M

2014-03-28

Glycoside hydrolase families 33 and 34 catalyse the hydrolysis of terminal sialic acid residues from sialyl oligosaccharides and glycoconjugates with a net retention of the stereochemistry at the anomeric centre. It is generally believed that the conserved aspartic acid in the active site functions as a general acid to protonate the hydroxyl group of the departing aglycone during glycosylation, and then as a general base to facilitate the nucleophilic attack of the water molecule on the intermediate state during the deglycosylation reaction. The dual role of the general acid/base places specific demands upon its protonation state, and thus pKa values. However, it is not fully understood how this catalytic residue can achieve such pKa cycling during catalysis. We present both MM and combined QM/MM simulations to characterise the pKa values of the proposed catalytic general acid/base in the glycoside hydrolase families 33 and 34. Collectively, our study suggests that the binding of anionic substrates and the local solvation properties along with the neutralisation of the nearby glutamic acid upon glycosylation modulate the electrostatic environment around the general acid/base to achieve its proper protonation states.

Metabolomics and transcriptomics profiles reveal the dysregulation of the tricarboxylic acid cycle and related mechanisms in prostate cancer.

PubMed

Shao, Yaping; Ye, Guozhu; Ren, Shancheng; Piao, Hai-Long; Zhao, Xinjie; Lu, Xin; Wang, Fubo; Ma, Wang; Li, Jia; Yin, Peiyuan; Xia, Tian; Xu, Chuanliang; Yu, Jane J; Sun, Yinghao; Xu, Guowang

2018-07-15

Genetic alterations drive metabolic reprograming to meet increased biosynthetic precursor and energy demands for cancer cell proliferation and survival in unfavorable environments. A systematic study of gene-metabolite regulatory networks and metabolic dysregulation should reveal the molecular mechanisms underlying prostate cancer (PCa) pathogenesis. Herein, we performed gas chromatography-mass spectrometry (GC-MS)-based metabolomics and RNA-seq analyses in prostate tumors and matched adjacent normal tissues (ANTs) to elucidate the molecular alterations and potential underlying regulatory mechanisms in PCa. Significant accumulation of metabolic intermediates and enrichment of genes in the tricarboxylic acid (TCA) cycle were observed in tumor tissues, indicating TCA cycle hyperactivation in PCa tissues. In addition, the levels of fumarate and malate were highly correlated with the Gleason score, tumor stage and expression of genes encoding related enzymes and were significantly related to the expression of genes involved in branched chain amino acid degradation. Using an integrated omics approach, we further revealed the potential anaplerotic routes from pyruvate, glutamine catabolism and branched chain amino acid (BCAA) degradation contributing to replenishing metabolites for TCA cycle. Integrated omics techniques enable the performance of network-based analyses to gain a comprehensive and in-depth understanding of PCa pathophysiology and may facilitate the development of new and effective therapeutic strategies. © 2018 UICC.

Quantitative importance of the pentose phosphate pathway determined by incorporation of 13C from [2-13C]- and [3-13C]glucose into TCA cycle intermediates and neurotransmitter amino acids in functionally intact neurons

PubMed Central

Brekke, Eva M F; Walls, Anne B; Schousboe, Arne; Waagepetersen, Helle S; Sonnewald, Ursula

2012-01-01

The brain is highly susceptible to oxidative injury, and the pentose phosphate pathway (PPP) has been shown to be affected by pathological conditions, such as Alzheimer's disease and traumatic brain injury. While this pathway has been investigated in the intact brain and in astrocytes, little is known about the PPP in neurons. The activity of the PPP was quantified in cultured cerebral cortical and cerebellar neurons after incubation in the presence of [2-13C]glucose or [3-13C]glucose. The activity of the PPP was several fold lower than glycolysis in both types of neurons. While metabolism of 13C-labeled glucose via the PPP does not appear to contribute to the production of releasable lactate, it contributes to labeling of tricarboxylic acid (TCA) cycle intermediates and related amino acids. Based on glutamate isotopomers, it was calculated that PPP activity accounts for ∼6% of glucose metabolism in cortical neurons and ∼4% in cerebellar neurons. This is the first demonstration that pyruvate generated from glucose via the PPP contributes to the synthesis of acetyl CoA for oxidation in the TCA cycle. Moreover, the fact that 13C labeling from glucose is incorporated into glutamate proves that both the oxidative and the nonoxidative stages of the PPP are active in neurons. PMID:22714050

Hydrogen-bonded intermediates and transition states during spontaneous and acid-catalyzed hydrolysis of the carcinogen (+)-anti-BPDE.

PubMed

Palenik, Mark C; Rodriguez, Jorge H

2014-07-07

Understanding mechanisms of (+)-anti-BPDE detoxification is crucial for combating its mutagenic and potent carcinogenic action. However, energetic-structural correlations of reaction intermediates and transition states during detoxification via hydrolysis are poorly understood. To gain mechanistic insight we have computationally characterized intermediate and transition species associated with spontaneous and general-acid catalyzed hydrolysis of (+)-anti-BPDE. We studied the role of cacodylic acid as a proton donor in the rate limiting step. The computed activation energy (ΔG‡) is in agreement with the experimental value for hydrolysis in a sodium cacodylate buffer. Both types of, spontaneous and acid catalyzed, BPDE hydrolysis can proceed through low-entropy hydrogen bonded intermediates prior to formation of transition states whose energies determine reaction activation barriers and rates.

FabQ, a Dual-Function Dehydratase/Isomerase, Circumvents the Last Step of the Classical Fatty Acid Synthesis Cycle

PubMed Central

Bi, Hongkai; Wang, Haihong; Cronan, John E.

2015-01-01

SUMMARY In the classical anaerobic pathway of unsaturated fatty acid biosynthesis, that of Escherichia coli, the double bond is introduced into the growing acyl chain by the FabA dehydratase/isomerase. Another dehydratase, FabZ, functions in the chain elongation cycle. In contrast, Aerococcus viridans has only a single FabA/FabZ homolog we designate FabQ. FabQ can not only replace the function of E. coli FabZ in vivo, but it also catalyzes the isomerization required for unsaturated fatty acid biosynthesis. Most strikingly, FabQ in combination with E. coli FabB imparts the surprising ability to bypass reduction of the trans-2-acyl-ACP intermediates of classical fatty acid synthesis. FabQ allows elongation by progressive isomerization reactions to form the polyunsaturated fatty acid, 3-hydroxy-cis-5, 7-hexadecadienoic acid, both in vitro and in vivo. FabQ therefore provides a potential pathway for bacterial synthesis of polyunsaturated fatty acids. PMID:23972938

Production of Putative Diterpene Carboxylic Acid Intermediates of Triptolide in Yeast

DOE Office of Scientific and Technical Information (OSTI.GOV)

Forman, Victor; Callari, Roberta; Folly, Christophe

The development of medical applications exploiting the broad bioactivities of the diterpene therapeutic triptolide from Tripterygium wilfordii is limited by low extraction yields from the native plant. Furthermore, the extraordinarily high structural complexity prevents an economically attractive enantioselective total synthesis. An alternative production route of triptolide through engineered Saccharomyces cerevisiae (yeast) could provide a sustainable source of triptolide. A potential intermediate in the unknown biosynthetic route to triptolide is the diterpene dehydroabietic acid. Here, we report a biosynthetic route to dehydroabietic acid by transient expression of enzymes from T. wilfordii and Sitka spruce (Picea sitchensis) in Nicotiana benthamiana. The combinationmore » of diterpene synthases TwTPS9, TwTPS27, and cytochromes P450 PsCYP720B4 yielded dehydroabietic acid and a novel analog, tentatively identified as ‘miltiradienic acid’. This biosynthetic pathway was reassembled in a yeast strain engineered for increased yields of the pathway intermediates, the diterpene olefins miltiradiene and dehydroabietadiene. Introduction in that strain of PsCYP720B4 in combination with two alternative NADPH-dependent cytochrome P450 reductases resulted in scalable in vivo production of dehydroabietic acid and its analog from glucose. Approaching future elucidation of the remaining biosynthetic steps to triptolide, our findings may provide an independent platform for testing of additional recombinant candidate genes, and ultimately pave the way to biotechnological production of the high value diterpenoid therapeutic.« less

Production of Putative Diterpene Carboxylic Acid Intermediates of Triptolide in Yeast

DOE PAGES

Forman, Victor; Callari, Roberta; Folly, Christophe; ...

2017-06-13

The development of medical applications exploiting the broad bioactivities of the diterpene therapeutic triptolide from Tripterygium wilfordii is limited by low extraction yields from the native plant. Furthermore, the extraordinarily high structural complexity prevents an economically attractive enantioselective total synthesis. An alternative production route of triptolide through engineered Saccharomyces cerevisiae (yeast) could provide a sustainable source of triptolide. A potential intermediate in the unknown biosynthetic route to triptolide is the diterpene dehydroabietic acid. Here, we report a biosynthetic route to dehydroabietic acid by transient expression of enzymes from T. wilfordii and Sitka spruce (Picea sitchensis) in Nicotiana benthamiana. The combinationmore » of diterpene synthases TwTPS9, TwTPS27, and cytochromes P450 PsCYP720B4 yielded dehydroabietic acid and a novel analog, tentatively identified as ‘miltiradienic acid’. This biosynthetic pathway was reassembled in a yeast strain engineered for increased yields of the pathway intermediates, the diterpene olefins miltiradiene and dehydroabietadiene. Introduction in that strain of PsCYP720B4 in combination with two alternative NADPH-dependent cytochrome P450 reductases resulted in scalable in vivo production of dehydroabietic acid and its analog from glucose. Approaching future elucidation of the remaining biosynthetic steps to triptolide, our findings may provide an independent platform for testing of additional recombinant candidate genes, and ultimately pave the way to biotechnological production of the high value diterpenoid therapeutic.« less

Involvement of organic acids and amino acids in ameliorating Ni(II) toxicity induced cell cycle dysregulation in Caulobacter crescentus: a metabolomics analysis.

PubMed

Jain, Abhishek; Chen, Wei Ning

2018-05-01

Nickel (Ni(II)) toxicity is addressed by many different bacteria, but bacterial responses to nickel stress are still unclear. Therefore, we studied the effect of Ni(II) toxicity on cell proliferation of α-proteobacterium Caulobacter crescentus. Next, we showed the mechanism that allows C. crescentus to survive in Ni(II) stress condition. Our results revealed that the growth of C. crescentus is severely affected when the bacterium was exposed to different Ni(II) concentrations, 0.003 mM slightly affected the growth, 0.008 mM reduced the growth by 50%, and growth was completely inhibited at 0.015 mM. It was further shown that Ni(II) toxicity induced mislocalization of major regulatory proteins such as MipZ, FtsZ, ParB, and MreB, resulting in dysregulation of the cell cycle. GC-MS metabolomics analysis of Ni(II) stressed C. crescentus showed an increased level of nine important metabolites including TCA cycle intermediates and amino acids. This indicates that changes in central carbon metabolism and nitrogen metabolism are linked with the disruption of cell division process. Addition of malic acid, citric acid, alanine, proline, and glutamine to 0.015 mM Ni(II)-treated C. crescentus restored its growth. Thus, the present work shows a protective effect of these organic acids and amino acids on Ni(II) toxicity. Metabolic stimulation through the PutA/GlnA pathway, accelerated degradation of CtrA, and Ni-chelation by organic acids or amino acids are some of the possible mechanisms suggested to be involved in enhancing C. crescentus's tolerance. Our results shed light on the mechanism of increased Ni(II) tolerance in C. crescentus which may be useful in bioremediation strategies and synthetic biology applications such as the development of whole cell biosensor.

Computational exploration of the chemical structure space of possible reverse tricarboxylic acid cycle constituents.

PubMed

Meringer, Markus; Cleaves, H James

2017-12-13

The reverse tricarboxylic acid (rTCA) cycle has been explored from various standpoints as an idealized primordial metabolic cycle. Its simplicity and apparent ubiquity in diverse organisms across the tree of life have been used to argue for its antiquity and its optimality. In 2000 it was proposed that chemoinformatics approaches support some of these views. Specifically, defined queries of the Beilstein database showed that the molecules of the rTCA are heavily represented in such compound databases. We explore here the chemical structure "space," e.g. the set of organic compounds which possesses some minimal set of defining characteristics, of the rTCA cycle's intermediates using an exhaustive structure generation method. The rTCA's chemical space as defined by the original criteria and explored by our method is some six to seven times larger than originally considered. Acknowledging that each assumption in what is a defining criterion making the rTCA cycle special limits possible generative outcomes, there are many unrealized compounds which fulfill these criteria. That these compounds are unrealized could be due to evolutionary frozen accidents or optimization, though this optimization may also be for systems-level reasons, e.g., the way the pathway and its elements interface with other aspects of metabolism.

Trapping proton transfer intermediates in the disordered hydrogen-bonded network of cryogenic hydrofluoric acid solutions.

PubMed

Ayotte, Patrick; Plessis, Sylvain; Marchand, Patrick

2008-08-28

A molecular-level description of the structural and dynamical aspects that are responsible for the weak acid behaviour of dilute hydrofluoric acid solutions and their unusual increased acidity at near equimolar concentrations continues to elude us. We address this problem by reporting reflection-absorption infrared spectra (RAIRS) of cryogenic HF-H(2)O binary mixtures at various compositions prepared as nanoscopic films using molecular beam techniques. Optical constants for these cryogenic solutions [n(omega) and k(omega)] are obtained by iteratively solving Fresnel equations for stratified media. Modeling of the experimental RAIRS spectra allow for a quantitative interpretation of the complex interplay between multiple reflections, optical interference and absorption effects. The evolution of the strong absorption features in the intermediate 1000-3000 cm(-1) range with increasing HF concentration reveals the presence of various ionic dissociation intermediates that are trapped in the disordered H-bonded network of cryogenic hydrofluoric acid solutions. Our findings are discussed in light of the conventional interpretation of why hydrofluoric acid is a weak acid revealing molecular-level details of the mechanism for HF ionization that may be relevant to analogous elementary processes involved in the ionization of weak acids in aqueous solutions.

Sulfate radicals enable a non-enzymatic Krebs cycle precursor

PubMed Central

Keller, Markus A.; Kampjut, Domen; Harrison, Stuart A.; Ralser, Markus

2017-01-01

The evolutionary origins of the tricarboxylic acid cycle (TCA), or Krebs cycle, are so far unclear. Despite a few years ago, the existence of a simple non-enzymatic Krebs-cycle catalyst has been dismissed ‘as an appeal to magic’, citrate and other intermediates have meanwhile been discovered on a carbonaceous meteorite and do interconvert non-enzymatically. To identify the non-enzymatic Krebs cycle catalyst, we used combinatorial, quantitative high-throughput metabolomics to systematically screen iron and sulfate reaction milieus that orient on Archean sediment constituents. TCA cycle intermediates are found stable in water and in the presence of most iron and sulfate species, including simple iron-sulfate minerals. However, we report that TCA intermediates undergo 24 interconversion reactions in the presence of sulfate radicals that form from peroxydisulfate. The non-enzymatic reactions critically cover a topology as present in the Krebs cycle, the glyoxylate shunt and the succinic semialdehyde pathways. Assembled in a chemical network, the reactions achieve more than ninety percent carbon recovery. Our results show that a non-enzymatic precursor for the Krebs cycle is biologically sensible, efficient, and forms spontaneously in the presence of sulfate radicals. PMID:28584880

Blood metabolomics analysis identifies abnormalities in the citric acid cycle, urea cycle, and amino acid metabolism in bipolar disorder.

PubMed

Yoshimi, Noriko; Futamura, Takashi; Kakumoto, Keiji; Salehi, Alireza M; Sellgren, Carl M; Holmén-Larsson, Jessica; Jakobsson, Joel; Pålsson, Erik; Landén, Mikael; Hashimoto, Kenji

2016-06-01

Bipolar disorder (BD) is a severe and debilitating psychiatric disorder. However, the precise biological basis remains unknown, hampering the search for novel biomarkers. We performed a metabolomics analysis to discover novel peripheral biomarkers for BD. We quantified serum levels of 116 metabolites in mood-stabilized male BD patients (n = 54) and age-matched male healthy controls (n = 39). After multivariate logistic regression, serum levels of pyruvate, N-acetylglutamic acid, α-ketoglutarate, and arginine were significantly higher in BD patients than in healthy controls. Conversely, serum levels of β-alanine, and serine were significantly lower in BD patients than in healthy controls. Chronic (4-weeks) administration of lithium or valproic acid to adult male rats did not alter serum levels of pyruvate, N-acetylglutamic acid, β-alanine, serine, or arginine, but lithium administration significantly increased serum levels of α-ketoglutarate. The metabolomics analysis demonstrated altered serum levels of pyruvate, N-acetylglutamic acid, β-alanine, serine, and arginine in BD patients. The present findings suggest that abnormalities in the citric acid cycle, urea cycle, and amino acid metabolism play a role in the pathogenesis of BD.

Cell cycle nucleic acids, polypeptides and uses thereof

DOEpatents

Gordon-Kamm, William J [Urbandale, IA; Lowe, Keith S [Johnston, IA; Larkins, Brian A [Tucson, AZ; Dilkes, Brian R [Tucson, AZ; Sun, Yuejin [Westfield, IN

2007-08-14

The invention provides isolated nucleic acids and their encoded proteins that are involved in cell cycle regulation. The invention further provides recombinant expression cassettes, host cells, transgenic plants, and antibody compositions. The present invention provides methods and compositions relating to altering cell cycle protein content, cell cycle progression, cell number and/or composition of plants.

Formation of biologically relevant carboxylic acids during the gamma irradiation of acetic acid

NASA Technical Reports Server (NTRS)

Negron-Mendoza, A.; Ponnamperuma, C.

1976-01-01

Irradiation of aqueous solutions of acetic acid with gamma rays produced several carboxylic acids in small yield. Their identification was based on the technique of gas chromatography combined with mass spectrometry. Some of these acids are Krebs Cycle intermediates. Their simultaneous formation in experiments simulating the primitive conditions on the earth suggests that metabolic pathways may have had their origin in prebiotic chemical processes.

A novel intermediate in the reaction of seleno CYP119 with m-chloroperbenzoic acid.

PubMed

Sivaramakrishnan, Santhosh; Ouellet, Hugues; Du, Jing; McLean, Kirsty J; Medzihradszky, Katalin F; Dawson, John H; Munro, Andrew W; Ortiz de Montellano, Paul R

2011-04-12

Cytochrome P450-mediated monooxygenation generally proceeds via a reactive ferryl intermediate coupled to a ligand radical [Fe(IV)═O]+• termed Compound I (Cpd I). The proximal cysteine thiolate ligand is a critical determinant of the spectral and catalytic properties of P450 enzymes. To explore the effect of an increased level of donation of electrons by the proximal ligand in the P450 catalytic cycle, we recently reported successful incorporation of SeCys into the active site of CYP119, a thermophilic cytochrome P450. Here we report relevant physical properties of SeCYP119 and a detailed analysis of the reaction of SeCYP119 with m-chloroperbenzoic acid. Our results indicate that the selenolate anion reduces rather than stabilizes Cpd I and also protects the heme from oxidative destruction, leading to the generation of a new stable species with an absorbance maximum at 406 nm. This stable intermediate can be returned to the normal ferric state by reducing agents and thiols, in agreement with oxidative modification of the selenolate ligand itself. Thus, in the seleno protein, the oxidative damage shifts from the heme to the proximal ligand, presumably because (a) an increased level of donation of electrons more efficiently quenches reactive species such as Cpd I and (b) the protection of the thiolate ligand provided by the protein active site structure is insufficient to shield the more oxidizable selenolate ligand.

Serum uric acid in relation to endogenous reproductive hormones during the menstrual cycle: findings from the BioCycle study

PubMed Central

Mumford, Sunni L.; Dasharathy, Sonya S.; Pollack, Anna Z.; Perkins, Neil J.; Mattison, Donald R.; Cole, Stephen R.; Wactawski-Wende, Jean; Schisterman, Enrique F.

2013-01-01

STUDY QUESTION Do uric acid levels across the menstrual cycle show associations with endogenous estradiol (E2) and reproductive hormone concentrations in regularly menstruating women? SUMMARY ANSWER Mean uric acid concentrations were highest during the follicular phase, and were inversely associated with E2 and progesterone, and positively associated with FSH. WHAT IS KNOWN ALREADY E2 may decrease serum levels of uric acid in post-menopausal women; however, the interplay between endogenous reproductive hormones and uric acid levels among regularly menstruating women has not been elucidated. STUDY DESIGN, SIZE, DURATION The BioCycle study was a prospective cohort study conducted at the University at Buffalo research centre from 2005 to 2007, which followed healthy women for one (n = 9) or 2 (n = 250) menstrual cycle(s). PARTICIPANTS/MATERIALS, SETTING, METHODS Participants were healthy women aged 18–44 years. Hormones and uric acid were measured in serum eight times each cycle for up to two cycles. Marginal structural models with inverse probability of exposure weights were used to evaluate the associations between endogenous hormones and uric acid concentrations. MAIN RESULTS AND THE ROLE OF CHANCE Uric acid levels were observed to vary across the menstrual cycle, with the lowest levels observed during the luteal phase. Every log-unit increase in E2 was associated with a decrease in uric acid of 1.1% (β = −0.011; 95% confidence interval (CI): −0.019, −0.004; persistent-effects model), and for every log-unit increase in progesterone, uric acid decreased by ∼0.8% (β = −0.008; 95% CI: −0.012, −0.004; persistent-effects model). FSH was positively associated with uric acid concentrations, such that each log-unit increase was associated with a 1.6% increase in uric acid (β = 0.016; 95% CI: 0.005, 0.026; persistent-effects model). Progesterone and FSH were also associated with uric acid levels in acute-effects models. Of 509 cycles, 42 were anovulatory

Linked cycles of oxidative decarboxylation of glyoxylate as protometabolic analogs of the citric acid cycle.

PubMed

Springsteen, Greg; Yerabolu, Jayasudhan Reddy; Nelson, Julia; Rhea, Chandler Joel; Krishnamurthy, Ramanarayanan

2018-01-08

The development of metabolic approaches towards understanding the origins of life, which have focused mainly on the citric acid (TCA) cycle, have languished-primarily due to a lack of experimentally demonstrable and sustainable cycle(s) of reactions. We show here the existence of a protometabolic analog of the TCA involving two linked cycles, which convert glyoxylate into CO 2 and produce aspartic acid in the presence of ammonia. The reactions proceed from either pyruvate, oxaloacetate or malonate in the presence of glyoxylate as the carbon source and hydrogen peroxide as the oxidant under neutral aqueous conditions and at mild temperatures. The reaction pathway demonstrates turnover under controlled conditions. These results indicate that simpler versions of metabolic cycles could have emerged under potential prebiotic conditions, laying the foundation for the appearance of more sophisticated metabolic pathways once control by (polymeric) catalysts became available.

Metabolic Interaction between Urea Cycle and Citric Acid Cycle Shunt: A Guided Approach

ERIC Educational Resources Information Center

Pesi, Rossana; Balestri, Francesco; Ipata, Piero L.

2018-01-01

This article is a guided pedagogical approach, devoted to postgraduate students specializing in biochemistry, aimed at presenting all single reactions and overall equations leading to the metabolic interaction between ureagenesis and citric acid cycle to be incorporated into a two-three lecture series about the interaction of urea cycle with other…

Thiamine pyrophosphate requirement for o-succinylbenzoic acid synthesis in Escherichia coli and evidence for an intermediate.

PubMed Central

Meganathan, R; Bentley, R

1983-01-01

Cell-free extracts of various strains of Escherichia coli synthesize the menaquinone biosynthetic intermediate o-succinylbenzoic acid (OSB) when supplied with chorismic acid, 2-ketoglutaric acid, and thiamine pyrophosphate (TPP). To assay for OSB synthesis, 2-[U-14C]ketoglutaric acid was used as substrate, and the synthesized OSB was examined by radiogas chromatography (as the dimethyl ester). [U-14C]Shikimic acid also gave rise to radioactive OSB if the cofactors necessary for enzymatic conversion to chorismic acid were added. Use of 2-[1-14C]ketoglutaric acid does not give rise to labeled OSB. In the absence of TPP during the incubations, OSB synthesis was much reduced; these observations are consistent with the proposed role for the succinic semialdehyde-TPP anion as the reagent adding to chorismic acid. Extracts of cells from menC and menD mutants did not form OSB separately, but did so in combination. There was evidence for formation of a product, X, by extracts of a menC mutant incubated with chorismic acid, TPP, and 2-ketoglutaric acid; X was converted to OSB by extracts of a menD mutant. It appears that the intermediate, X, is formed by one gene product and converted to OSB by the second gene product. PMID:6337125

Using coral Ba/Ca records to investigate seasonal to decadal scale biogeochemical cycling in the surface and intermediate ocean.

NASA Astrophysics Data System (ADS)

LaVigne, M.; Cobb, K. M.; DeLong, K. L.; Freiberger, M. M.; Grottoli, A. G.; Hill, T. M.; Miller, H. R.; Nurhati, I. S.; Richey, J. N.; Serrato Marks, G.; Sherrell, R. M.

2016-12-01

Dissolved barium (BaSW), a bio-intermediate element, is linked to several biogeochemical processes such as the cycling and export of nutrients, organic carbon (Corg), and barite in surface and intermediate oceans. Dynamic BaSW cycling has been demonstrated in the water column on short timescales (days-weeks) while sedimentary records have documented geologic-scale changes in barite preservation driven by export production. Our understanding of how seasonal-decadal scale climate variability impacts these biogeochemical processes currently lacks robust records. Ba/Ca calibrations in surface and deep sea corals suggest barium is incorporated via cationic substitution in both aragonite and calcite. Here we demonstrate the utility of Ba/Ca for reconstructing biogeochemical variability using examples of surface and deep sea coral records. Century-long deep sea coral records from the California Current System (bamboo corals: 900-1500m) record interannual variations in Ba/Ca, likely reflecting changes in barite formation via bacterial Corg respiration or barite saturation state. A surface Porites coral Ba/Ca record from Christmas Island (central equatorial Pacific: 1978-1995) shows maxima during low productivity El Niño warm periods, suggesting that variations in BaSW are driven by biological removal via direct cellular uptake or indirectly via barite precipitation with the decomposition of large phytoplankton blooms at this location. Similarly, a sixteen-year long Siderastera siderea surface coral record from Dry Tortugas, FL (Gulf of Mexico: 1991-2007) shows seasonal Ba/Ca cycles that align with annual chlorophyll and δ13C. Taken together, these records demonstrate the linkages among Corg, nutrient cycling and BaSW in the surface and intermediate ocean on seasonal to decadal timescales. Multi-proxy paleoceanographic reconstructions including Ba/Ca have the potential to elucidate the mechanisms linking past climate, productivity, nutrients, and BaSW cycling in the past.

Time-resolved vibrational spectroscopy detects protein-based intermediates in the photosynthetic oxygen-evolving cycle.

PubMed

Barry, Bridgette A; Cooper, Ian B; De Riso, Antonio; Brewer, Scott H; Vu, Dung M; Dyer, R Brian

2006-05-09

Photosynthetic oxygen production by photosystem II (PSII) is responsible for the maintenance of aerobic life on earth. The production of oxygen occurs at the PSII oxygen-evolving complex (OEC), which contains a tetranuclear manganese (Mn) cluster. Photo-induced electron transfer events in the reaction center lead to the accumulation of oxidizing equivalents on the OEC. Four sequential photooxidation reactions are required for oxygen production. The oxidizing complex cycles among five oxidation states, called the S(n) states, where n refers to the number of oxidizing equivalents stored. Oxygen release occurs during the S(3)-to-S(0) transition from an unstable intermediate, known as the S(4) state. In this report, we present data providing evidence for the production of an intermediate during each S state transition. These protein-derived intermediates are produced on the microsecond to millisecond time scale and are detected by time-resolved vibrational spectroscopy on the microsecond time scale. Our results suggest that a protein-derived conformational change or proton transfer reaction precedes Mn redox reactions during the S(2)-to-S(3) and S(3)-to-S(0) transitions.

Insights Into Intermediate Ocean Barium Cycling From Deep-Sea Bamboo Coral Records on the California Margin

NASA Astrophysics Data System (ADS)

LaVigne, M.; Serrato Marks, G.; Freiberger, M. M.; Miller, H. R.; Hill, T. M.; McNichol, A. P.; Lardie Gaylord, M.

2016-02-01

Dissolved barium (BaSW) has been linked to several biogeochemical processes such as the cycling and export of nutrients, organic carbon (Corg), and barite in surface and intermediate oceans. The dynamic nature of barium cycling in the water column has been demonstrated on short timescales (days-weeks) while sedimentary records have documented geologic-scale changes in barite preservation driven by export production. Our understanding of how inter-annual-decadal scale climate variability impacts these biogeochemical processes currently lacks robust instrumental and paleoceanographic records. Recent work has calibrated and demonstrated the reproducibility of a new BaSW proxy in California Current System (CCS) bamboo corals (Ba/Ca) using a coral depth transect spanning the CCS oxygen minimum zone (792-2055m water depth). New `reconnaissance' radiocarbon data identifying the bomb 14C spike in coral proteinaceous nodes and sclerochronological analyses of calcitic internodes are used to assign chronologies to the CCS coral records. Century-long coral records from 900-1500m record 4-7 year long increases in Ba/Ca ( 10-70 nmol/kg BaSW) at depths where rapid barite cycling occurs on day-weekly timescales. The BaSW peaks punctuate the coral records at different time periods and depths and do not coincide with inter-annual/decadal climate transitions (e.g. ENSO/PDO). Stable surface productivity and coral δ15N records indicate that Corg export from CCS surface waters has been relatively constant over the past century. Thus, the inter-annual scale BaSW peaks recorded by the 900-1500m corals more likely reflect periods of decreased barite formation (and/or increased dissolution) via reduced bacterial Corg respiration or barite saturation state. Paleoceanographic BaSW records and continued research on barium cycling in the modern ocean have the potential to elucidate the mechanisms linking intermediate water carbon and barium cycling, climate, and ocean oxygenation in the past.

Biodegradation of dichlorodiphenyltrichloroethane: intermediates in dichlorodiphenylacetic acid metabolism by aerobacter aerogenes

USGS Publications Warehouse

Wedemeyer, Gary

1967-01-01

The final product of dichlorodiphenyltrichloroethane (DDT) degradation by vertebrates is commonly considered to be dichlorodiphenylacetic acid, DDA. Recently, certain organisms have been found to degrade further DDA to dichlorobenzophenone (DBP), but the possibility that such degradation was due to microbial action could not be excluded. Significantly, dichlorobenzhydrol (DBH), dichlorophenylmethane (DPM), and dichlorodiphenylethylene (DDE) have been tentatively identified in rats fed DDA. Since DDA as well as DDT is degraded by the ubiquitous microorganism Aerobacter aerogenes, it seemed reasonable that the intestinal microflora might be involved in DBP formation, DPM and DBH being intermediates in its pathway from DDA. Since DDA is a (3,y-unsaturated acid, ketone formation via an alkene and an alcohol would be expected.

Forest Canopy Water Cycling Responses to an Intermediate Disturbance Revealed Through Stable Water Vapor Isotopes

NASA Astrophysics Data System (ADS)

Fiorella, R.; Poulsen, C. J.; Matheny, A. M.; Rey Sanchez, C.; Fotis, A. T.; Morin, T. H.; Vogel, C. S.; Gough, C. M.; Aron, P.; Bohrer, G.

2016-12-01

Forest structure, age, and species composition modulate fluxes of carbon and water between the land surface and the atmosphere. The response of forests to intermediate disturbances such as ecological succession, species-specific insect invasion, or selective logging that disrupt the canopy but do not promote complete stand replacement, shape how these fluxes evolve through time. We investigate the impact of an intermediate disturbance to water cycling processes by comparing vertical profiles of stable water isotopes in two closely located forest canopies in the northern lower peninsula of Michigan using cavity ring-down spectroscopy. In one of the canopies, an intermediate disturbance was prescribed in 2008 by inducing mortality in all canopy-dominant early successional species. Isotopic compositions of atmospheric water vapor are measured at six heights during two time periods (summer and early fall) at two flux towers and compared with local meteorology and calculated atmospheric back-trajectories. Disturbance has little impact on low-frequency changes in isotopic composition (e.g., >1 day); at these timescales, isotopic composition is strongly related to large-scale moisture transport. In contrast, disturbance has substantial impacts on the vertical distribution of water isotopes throughout the canopy when transpiration rates are high during the summer, but impact is muted during early fall. Sub-diurnal differences in canopy water vapor cycling are likely related to differences in species composition and response to disturbance and changes in canopy structure. Predictions of transpiration fluxes by land-surface models that do not account species-specific relationships and canopy structure are unlikely to capture these relationships, but addition of stable isotopes to land surface models may provide a useful parameter to improve these predictions.

An involvement of yeast peroxisomal channels in transmembrane transfer of glyoxylate cycle intermediates.

PubMed

Antonenkov, Vasily D; Mindthoff, Sabrina; Grunau, Silke; Erdmann, Ralf; Hiltunen, J Kalervo

2009-12-01

The separate localization of glyoxylate cycle enzymes in the peroxisomes and the cytosol of the yeast Saccharomyces cerevisiae indicates that the peroxisomal membrane must permit the flow of metabolites between the two compartments. The transfer of these metabolites may require peroxisomal membrane channel(s). We used an electrophysiological approach (reconstitution assay in lipid bilayers) to assess the ability of peroxisomal membrane channels to conduct different solutes including metabolites of the glyoxylate cycle. At least two distinct channel-forming activities were detected in peroxisomal preparations. One of these activities was highly inducible by dithiothreitol and showed large-amplitude current increments when 1M KCl was used as a bath solution. Single-channel analysis revealed that the inducible channel is anion-selective (P(Cl(-)) / P(K(+)) = 2.6; P(citrate)/P(K(+)) = 1.6) and displays flickering at holding potentials over + or - 30mV directed upward or downward relative to the main open state of the channel. The channel inducible by DTT facilitates the transfer of solutes with a molecular mass up to 400Da, sufficient to allow the transmembrane trafficking of glyoxylate cycle intermediates between the peroxisomal lumen and the cytoplasm.

Closed cycle ion exchange method for regenerating acids, bases and salts

DOEpatents

Dreyfuss, Robert M.

1976-01-01

A method for conducting a chemical reaction in acidic, basic, or neutral solution as required and then regenerating the acid, base, or salt by means of ion exchange in a closed cycle reaction sequence which comprises contacting the spent acid, base, or salt with an ion exchanger, preferably a synthetic organic ion-exchange resin, so selected that the counter ions thereof are ions also produced as a by-product in the closed reaction cycle, and then regenerating the spent ion exchanger by contact with the by-product counter ions. The method is particularly applicable to closed cycle processes for the thermochemical production of hydrogen.

Features of the Phosphatidylinositol Cycle and its Role in Signal Transduction.

PubMed

Epand, Richard M

2017-08-01

The phosphatidylinositol cycle (PI-cycle) has a central role in cell signaling. It is the major pathway for the synthesis of phosphatidylinositol and its phosphorylated forms. In addition, some lipid intermediates of the PI-cycle, including diacylglycerol and phosphatidic acid, are also important lipid signaling agents. The PI-cycle has some features that are important for the understanding of its role in the cell. As a cycle, the intermediates will be regenerated. The PI-cycle requires a large amount of metabolic energy. There are different steps of the cycle that occur in two different membranes, the plasma membrane and the endoplasmic reticulum. In order to complete the PI-cycle lipid must be transferred between the two membranes. The role of the Nir proteins in the process has recently been elucidated. The lipid intermediates of the PI-cycle are normally highly enriched with 1-stearoyl-2-arachidonoyl molecular species in mammals. This enrichment will be retained as long as the intermediates are segregated from other lipids of the cell. However, there is a significant fraction (>15 %) of lipids in the PI-cycle of normal cells that have other acyl chains. Phosphatidylinositol largely devoid of arachidonoyl chains are found in cancer cells. Phosphatidylinositol species with less unsaturation will not be as readily converted to phosphatidylinositol-3,4,5-trisphosphate, the lipid required for the activation of Akt with resulting effects on cell proliferation. Thus, the cyclical nature of the PI-cycle, its dependence on acyl chain composition and its requirement for lipid transfer between two membranes, explain many of the biological properties of this cycle.

Intermediates of Krebs cycle correct the depression of the whole body oxygen consumption and lethal cooling in barbiturate poisoning in rat.

PubMed

Ivnitsky, Jury Ju; Schäfer, Timur V; Malakhovsky, Vladimir N; Rejniuk, Vladimir L

2004-10-01

Rats poisoned with one LD50 of thiopental or amytal are shown to increase oxygen consumption when intraperitoneally given sucinate, malate, citrate, alpha-ketoglutarate, dimethylsuccinate or glutamate (the Krebs cycle intermediates or their precursors) but not when given glucose, pyruvate, acetate, benzoate or nicotinate (energy substrates of other metabolic stages etc). Survival was increased with succinate or malate from control groups, which ranged from 30-83% to 87-100%. These effects were unrelated to respiratory depression or hypoxia as judged by little or no effect of succinate on ventilation indices and by the lack of effect of oxygen administration. Body cooling of comatose rats at ambient temperature approximately 19 degrees C became slower with succinate, the rate of cooling correlated well with oxygen consumption decrease. Succinate had no potency to modify oxygen consumption and body temperature in intact rats. A condition for antidote effect of the Krebs intermediate was sufficiently high dosage (5 mmol/kg), further dose increase made no odds. Repeated dosing of succinate had more marked protective effect, than a single one, to oxygen consumption and tended to promote the attenuation of lethal effect of barbiturates. These data suggest that suppression of whole body oxygen consumption with barbiturate overdose could be an important contributor to both body cooling and mortality. Intermediates of Krebs cycle, not only succinate, may have a pronounced therapeutic effect under the proper treatment regimen. Availability of Krebs cycle intermediates may be a limiting factor for the whole body oxygen consumption in barbiturate coma, its role in brain needs further elucidation.

Degradation pathway of the naphthalene azo dye intermediate 1-diazo-2- naphthol-4-sulfonic acid using Fenton's reagent.

PubMed

Zhu, Nanwen; Gu, Lin; Yuan, Haiping; Lou, Ziyang; Wang, Liang; Zhang, Xin

2012-08-01

Degradation of naphthalene dye intermediate 1-diazo-2- naphthol-4-sulfonic acid (1,2,4-Acid) by Fenton process has been studied in depth for the purpose of learning more about the reactions involved in the oxidation of 1,2,4-Acid. During 1,2,4-Acid oxidation, the solution color initially takes on a dark red, then to dark black associated with the formation of quinodial-type structures, and then goes to dark brown and gradually disappears, indicating a fast degradation of azo group. The observed color changes of the solution are a result of main reaction intermediates, which can be an indicator of the level of oxidization reached. Nevertheless, complete TOC removal is not accomplished, in accordance with the presence of resistant carboxylic acids at the end of the reaction. The intermediates generated along the reaction time have been identified and quantified. UPLC-(ESI)-TOF-HRMS analysis allows the detection of 19 aromatic compounds of different size and complexity. Some of them share the same accurate mass but appear at different retention time, evidencing their different molecular structures. Heteroatom oxidation products like SO(4)(2-) have also been quantified and explanations of their release are proposed. Short-chain carboxylic acids are detected at long reaction time, as a previous step to complete the process of dye mineralization. Finally, considering all the findings of the present study and previous related works, the evolution from the original 1,2,4-Acid to the final products is proposed in a general reaction scheme. Copyright © 2012 Elsevier Ltd. All rights reserved.

TRIIODOTHYRONINE INCREASES MYOCARDIAL FUNCTION AND PYRUVATE ENTRY INTO THE CITRIC ACID CYCLE AFTER REPERFUSION IN A MODEL OF INFANT CARDIOPULMONARY BYPASS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Olson, Aaron; Bouchard, Bertrand; Ning, Xue-Han

We utilized a translational model of infant CPB to test the hypothesis that T3 modulates pyruvate entry into the citric acid cycle (CAC) thereby providing the energy support for improved cardiac function after ischemia-reperfusion. Methods and Results: Neonatal piglets received intracoronary [2-13Carbon(13C)]-pyruvate for 40 minutes (8 mM) during control aerobic conditions (Cont) or immediately after reperfusion (IR) from global hypothermic ischemia. A third group (IR-Tr) received T3 (1.2 ug/kg) during reperfusion. We assessed absolute CAC intermediate levels (aCAC) and flux parameters into the CAC through oxidative pyruvate decarboxylation (PDC ) and anaplerotic carboxylation (PC; ) using 13C-labeled pyruvate and isotopomermore » analysis by gas and liquid chromatography-mass spectrometry and 13C NMR. Neither IR nor IR-Tr modified aCAC. However, compared to IR, T3 (group IR-Tr) increased cardiac power and oxygen consumption after CPB while elevating both PDC and PC (~ four-fold). T3 inhibited IR induced reductions in CAC intermediate molar percent enrichment (MPE) and oxaloacetate(citrate)/malate MPE ratio; an index of aspartate entry into the CAC. Conclusions: T3 markedly enhances PC and PDC thereby providing substrate for elevated cardiac function and work after reperfusion. The increases in pyruvate flux occur with preservation of the CAC intermediate pool. Additionally, T3 inhibition of reductions in CAC intermediate MPEs indicates that T3 reduces the reliance on amino acids (AA) for anaplerosis after reperfusion. Thus, AA should be more available for other functions such as protein synthesis.« less

Analysis of hyaluronic acid concentration in rat vocal folds during estral and gravidic puerperal cycles.

PubMed

Pedroso, José Eduardo de Sá; Brasil, Osíris Camponês do; Martins, João Roberto Maciel; Nader, Helena Bociane; Simões, Manuel de Jesus

2009-01-01

Hormone plays an important role in the larynx. Among other substances, vocal folds contain hyaluronic acid, which tissue concentration may vary according to hormone action. the objective of this study is to analyze hyaluronic acid concentration in the vocal folds during estral and gravidic-puerperal cycles. Experimental study. 40 adult rats were divided into two groups. In the first group we used 20 rats to establish the concentration of hyaluronic acid during the estral cycle and in the second group, 20 animals were submitted to the same procedure but during the gravidic-puerperal cycle. Variations in hyaluronic acid concentration was not observed during the estral cycle. In the gravidic puerperal cycle group, an increase in hyaluronic acid concentration was observed in the puerperal subgroup. Comparing the two groups of estral and gravidic-puerperal cycles, no difference was observed. In comparing all subgroups of estral and gravidic-puerperal cycles, an increase in hyaluronic acid concentration was noticed only in the puerperal phase.

Sulfuric acid-sulfur heat storage cycle

DOEpatents

Norman, John H.

1983-12-20

A method of storing heat is provided utilizing a chemical cycle which interconverts sulfuric acid and sulfur. The method can be used to levelize the energy obtained from intermittent heat sources, such as solar collectors. Dilute sulfuric acid is concentrated by evaporation of water, and the concentrated sulfuric acid is boiled and decomposed using intense heat from the heat source, forming sulfur dioxide and oxygen. The sulfur dioxide is reacted with water in a disproportionation reaction yielding dilute sulfuric acid, which is recycled, and elemental sulfur. The sulfur has substantial potential chemical energy and represents the storage of a significant portion of the energy obtained from the heat source. The sulfur is burned whenever required to release the stored energy. A particularly advantageous use of the heat storage method is in conjunction with a solar-powered facility which uses the Bunsen reaction in a water-splitting process. The energy storage method is used to levelize the availability of solar energy while some of the sulfur dioxide produced in the heat storage reactions is converted to sulfuric acid in the Bunsen reaction.

Properties of Intermediates in the Catalytic Cycle of Oxalate Oxidoreductase and Its Suicide Inactivation by Pyruvate

PubMed Central

2017-01-01

Oxalate:ferredoxin oxidoreductase (OOR) is an unusual member of the thiamine pyrophosphate (TPP)-dependent 2-oxoacid:ferredoxin oxidoreductase (OFOR) family in that it catalyzes the coenzyme A (CoA)-independent conversion of oxalate into 2 equivalents of carbon dioxide. This reaction is surprising because binding of CoA to the acyl-TPP intermediate of other OFORs results in formation of a CoA ester, and in the case of pyruvate:ferredoxin oxidoreductase (PFOR), CoA binding generates the central metabolic intermediate acetyl-CoA and promotes a 105-fold acceleration of the rate of electron transfer. Here we describe kinetic, spectroscopic, and computational results to show that CoA has no effect on catalysis by OOR and describe the chemical rationale for why this cofactor is unnecessary in this enzymatic transformation. Our results demonstrate that, like PFOR, OOR binds pyruvate and catalyzes decarboxylation to form the same hydroxyethylidine–TPP (HE–TPP) intermediate and one-electron transfer to generate the HE–TPP radical. However, in OOR, this intermediate remains stranded at the active site as a covalent inhibitor. These and other results indicate that, like other OFOR family members, OOR generates an oxalate-derived adduct with TPP (oxalyl-TPP) that undergoes decarboxylation and one-electron transfer to form a radical intermediate remaining bound to TPP (dihydroxymethylidene–TPP). However, unlike in PFOR, where CoA binding drives formation of the product, in OOR, proton transfer and a conformational change in the “switch loop” alter the redox potential of the radical intermediate sufficiently to promote the transfer of an electron into the iron–sulfur cluster network, leading directly to a second decarboxylation and completing the catalytic cycle. PMID:28514140

Inhibition of Pyruvate Dehydrogenase Kinase 2 Protects Against Hepatic Steatosis Through Modulation of Tricarboxylic Acid Cycle Anaplerosis and Ketogenesis.

PubMed

Go, Younghoon; Jeong, Ji Yun; Jeoung, Nam Ho; Jeon, Jae-Han; Park, Bo-Yoon; Kang, Hyeon-Ji; Ha, Chae-Myeong; Choi, Young-Keun; Lee, Sun Joo; Ham, Hye Jin; Kim, Byung-Gyu; Park, Keun-Gyu; Park, So Young; Lee, Chul-Ho; Choi, Cheol Soo; Park, Tae-Sik; Lee, W N Paul; Harris, Robert A; Lee, In-Kyu

2016-10-01

Hepatic steatosis is associated with increased insulin resistance and tricarboxylic acid (TCA) cycle flux, but decreased ketogenesis and pyruvate dehydrogenase complex (PDC) flux. This study examined whether hepatic PDC activation by inhibition of pyruvate dehydrogenase kinase 2 (PDK2) ameliorates these metabolic abnormalities. Wild-type mice fed a high-fat diet exhibited hepatic steatosis, insulin resistance, and increased levels of pyruvate, TCA cycle intermediates, and malonyl-CoA but reduced ketogenesis and PDC activity due to PDK2 induction. Hepatic PDC activation by PDK2 inhibition attenuated hepatic steatosis, improved hepatic insulin sensitivity, reduced hepatic glucose production, increased capacity for β-oxidation and ketogenesis, and decreased the capacity for lipogenesis. These results were attributed to altered enzymatic capacities and a reduction in TCA anaplerosis that limited the availability of oxaloacetate for the TCA cycle, which promoted ketogenesis. The current study reports that increasing hepatic PDC activity by inhibition of PDK2 ameliorates hepatic steatosis and insulin sensitivity by regulating TCA cycle anaplerosis and ketogenesis. The findings suggest PDK2 is a potential therapeutic target for nonalcoholic fatty liver disease. © 2016 by the American Diabetes Association.

Geobiochemistry of metabolism: Standard state thermodynamic properties of the citric acid cycle

NASA Astrophysics Data System (ADS)

Canovas, Peter A.; Shock, Everett L.

2016-12-01

Integrating microbial metabolism into geochemical modeling allows assessments of energy and mass transfer between the geosphere and the microbial biosphere. Energy and power supplies and demands can be assessed from analytical geochemical data given thermodynamic data for compounds involved in catabolism and anabolism. Results are reported here from a critique of the available standard state thermodynamic data for organic acids and acid anions involved in the citric acid cycle (also known as the tricarboxylic acid cycle or the Krebs cycle). The development of methods for estimating standard state data unavailable from experiments is described, together with methods to predict corresponding values at elevated temperatures and pressures using the revised Helgeson-Kirkham-Flowers (HKF) equation of state for aqueous species. Internal consistency is maintained with standard state thermodynamic data for organic and inorganic aqueous species commonly used in geochemical modeling efforts. Standard state data and revised-HKF parameters are used to predict equilibrium dissociation constants for the organic acids in the citric acid cycle, and to assess standard Gibbs energies of reactions for each step in the cycle at elevated temperatures and pressures. The results presented here can be used with analytical data from natural and experimental systems to assess the energy and power demands of microorganisms throughout the habitable ranges of pressure and temperature, and to assess the consequences of abiotic organic compound alteration processes at conditions of subsurface aquifers, sedimentary basins, hydrothermal systems, meteorite parent bodies, and ocean worlds throughout the solar system.

Sulfuric acid on Europa and the radiolytic sulfur cycle.

PubMed

Carlson, R W; Johnson, R E; Anderson, M S

1999-10-01

A comparison of laboratory spectra with Galileo data indicates that hydrated sulfuric acid is present and is a major component of Europa's surface. In addition, this moon's visually dark surface material, which spatially correlates with the sulfuric acid concentration, is identified as radiolytically altered sulfur polymers. Radiolysis of the surface by magnetospheric plasma bombardment continuously cycles sulfur between three forms: sulfuric acid, sulfur dioxide, and sulfur polymers, with sulfuric acid being about 50 times as abundant as the other forms. Enhanced sulfuric acid concentrations are found in Europa's geologically young terrains, suggesting that low-temperature, liquid sulfuric acid may influence geological processes.

Intracellular synthesis of glutamic acid in Bacillus methylotrophicus SK19.001, a glutamate-independent poly(γ-glutamic acid)-producing strain.

PubMed

Peng, Yingyun; Zhang, Tao; Mu, Wanmeng; Miao, Ming; Jiang, Bo

2016-01-15

Bacillus methylotrophicus SK19.001 is a glutamate-independent strain that produces poly(γ-glutamic acid) (γ-PGA), a polymer of D- and L-glutamic acids that possesses applications in food, the environment, agriculture, etc. This study was undertaken to explore the synthetic pathway of intracellular L- and D-glutamic acid in SK19.001 by investigating the effects of tricarboxylic acid cycle intermediates and different amino acids as metabolic precursors on the production of γ-PGA and analyzing the activities of the enzymes involved in the synthesis of L- and D-glutamate. Tricarboxylic acid cycle intermediates and amino acids could participate in the synthesis of γ-PGA via independent pathways in SK19.001. L-Aspartate aminotransferase, L-glutaminase and L-glutamate synthase were the enzymatic sources of L-glutamate. Glutamate racemase was responsible for the formation of D-glutamate for the synthesis of γ-PGA, and the synthetase had stereoselectivity for glutamate substrate. The enzymatic sources of L-glutamate were investigated for the first time in the glutamate-independent γ-PGA-producing strain, and multiple enzymatic sources of L-glutamate were verified in SK19.001, which will benefit efforts to improve production of γ-PGA with metabolic engineering strategies. © 2015 Society of Chemical Industry.

Heme-bound nitroxyl, hydroxylamine, and ammonia ligands as intermediates in the reaction cycle of cytochrome c nitrite reductase: a theoretical study.

PubMed

Bykov, Dmytro; Plog, Matthias; Neese, Frank

2014-01-01

In this article, we consider, in detail, the second half-cycle of the six-electron nitrite reduction mechanism catalyzed by cytochrome c nitrite reductase. In total, three electrons and four protons must be provided to reach the final product, ammonia, starting from the HNO intermediate. According to our results, the first event in this half-cycle is the reduction of the HNO intermediate, which is accomplished by two PCET reactions. Two isomeric radical intermediates, HNOH(•) and H2NO(•), are formed. Both intermediates are readily transformed into hydroxylamine, most likely through intramolecular proton transfer from either Arg114 or His277. An extra proton must enter the active site of the enzyme to initiate heterolytic cleavage of the N-O bond. As a result of N-O bond cleavage, the H2N(+) intermediate is formed. The latter readily picks up an electron, forming H2N(+•), which in turn reacts with Tyr218. Interestingly, evidence for Tyr218 activity was provided by the mutational studies of Lukat (Biochemistry 47:2080, 2008), but this has never been observed in the initial stages of the overall reduction process. According to our results, an intramolecular reaction with Tyr218 in the final step of the nitrite reduction process leads directly to the final product, ammonia. Dissociation of the final product proceeds concomitantly with a change in spin state, which was also observed in the resonance Raman investigations of Martins et al. (J Phys Chem B 114:5563, 2010).

The synthesis of glutamic acid in the absence of enzymes: Implications for biogenesis

NASA Technical Reports Server (NTRS)

Morowitz, Harold; Peterson, Eta; Chang, Sherwood

1995-01-01

This paper reports on the non-enzymatic aqueous phase synthesis of amino acids from keto acids, ammonia and reducing agents. The facile synthesis of key metabolic intermediates, particularly in the glycolytic pathway, the citric acid cycle, and the first step of amino acid synthesis, lead to new ways of looking at the problem of biogenesis.

Role of intermediate phase for stable cycling of Na7V4(P2O7)4PO4 in sodium ion battery

PubMed Central

Lim, Soo Yeon; Kim, Heejin; Chung, Jaehoon; Lee, Ji Hoon; Kim, Byung Gon; Choi, Jeon-Jin; Chung, Kyung Yoon; Cho, Woosuk; Kim, Seung-Joo; Goddard, William A.; Jung, Yousung; Choi, Jang Wook

2014-01-01

Sodium ion batteries offer promising opportunities in emerging utility grid applications because of the low cost of raw materials, yet low energy density and limited cycle life remain critical drawbacks in their electrochemical operations. Herein, we report a vanadium-based ortho-diphosphate, Na7V4(P2O7)4PO4, or VODP, that significantly reduces all these drawbacks. Indeed, VODP exhibits single-valued voltage plateaus at 3.88 V vs. Na/Na+ while retaining substantial capacity (>78%) over 1,000 cycles. Electronic structure calculations reveal that the remarkable single plateau and cycle life originate from an intermediate phase (a very shallow voltage step) that is similar both in the energy level and lattice parameters to those of fully intercalated and deintercalated states. We propose a theoretical scheme in which the reaction barrier that arises from lattice mismatches can be evaluated by using a simple energetic consideration, suggesting that the presence of intermediate phases is beneficial for cell kinetics by buffering the differences in lattice parameters between initial and final phases. We expect these insights into the role of intermediate phases found for VODP hold in general and thus provide a helpful guideline in the further understanding and design of battery materials. PMID:24379365

Role of intermediate phase for stable cycling of Na7V4(P2O7)4PO4 in sodium ion battery.

PubMed

Lim, Soo Yeon; Kim, Heejin; Chung, Jaehoon; Lee, Ji Hoon; Kim, Byung Gon; Choi, Jeon-Jin; Chung, Kyung Yoon; Cho, Woosuk; Kim, Seung-Joo; Goddard, William A; Jung, Yousung; Choi, Jang Wook

2014-01-14

Sodium ion batteries offer promising opportunities in emerging utility grid applications because of the low cost of raw materials, yet low energy density and limited cycle life remain critical drawbacks in their electrochemical operations. Herein, we report a vanadium-based ortho-diphosphate, Na7V4(P2O7)4PO4, or VODP, that significantly reduces all these drawbacks. Indeed, VODP exhibits single-valued voltage plateaus at 3.88 V vs. Na/Na(+) while retaining substantial capacity (>78%) over 1,000 cycles. Electronic structure calculations reveal that the remarkable single plateau and cycle life originate from an intermediate phase (a very shallow voltage step) that is similar both in the energy level and lattice parameters to those of fully intercalated and deintercalated states. We propose a theoretical scheme in which the reaction barrier that arises from lattice mismatches can be evaluated by using a simple energetic consideration, suggesting that the presence of intermediate phases is beneficial for cell kinetics by buffering the differences in lattice parameters between initial and final phases. We expect these insights into the role of intermediate phases found for VODP hold in general and thus provide a helpful guideline in the further understanding and design of battery materials.

Structures of aspartic acid-96 in the L and N intermediates of bacteriorhodopsin: analysis by Fourier transform infrared spectroscopy

NASA Technical Reports Server (NTRS)

Maeda, A.; Sasaki, J.; Shichida, Y.; Yoshizawa, T.; Chang, M.; Ni, B.; Needleman, R.; Lanyi, J. K.

1992-01-01

The light-induced difference Fourier transform infrared spectrum between the L or N intermediate minus light-adapted bacteriorhodopsin (BR) was measured in order to examine the protonated states and the changes in the interactions of carboxylic acids of Asp-96 and Asp-115 in these intermediates. Vibrational bands due to the protonated and unprotonated carboxylic acid were identified by isotope shift and band depletion upon substitution of Asp-96 or -115 by asparagine. While the signal due to the deprotonation of Asp-96 was clearly observed in the N intermediate, this residue remained protonated in L. Asp-115 was partially deprotonated in L. The C = O stretching vibration of protonated Asp-96 of L showed almost no shift upon 2H2O substitution, in contrast to the corresponding band of Asp-96 or Asp-115 of BR, which shifted by 9-12 cm-1 under the same conditions. In the model system of acetic acid in organic solvents, such an absence of the shift of the C = O stretching vibration of the protonated carboxylic acid upon 2H2O substitution was seen only when the O-H of acetic acid is hydrogen-bonded. The non-hydrogen-bonded monomer showed the 2H2O-dependent shift. Thus, the O-H bond of Asp-96 enters into hydrogen bonding upon conversion of BR to L. Its increased hydrogen bonding in L is consistent with the observed downshift of the O-H stretching vibration of the carboxylic acid of Asp-96.

Induction of intermediate mesoderm by retinoic acid receptor signaling from differentiating mouse embryonic stem cells.

PubMed

Oeda, Shiho; Hayashi, Yohei; Chan, Techuan; Takasato, Minoru; Aihara, Yuko; Okabayashi, Koji; Ohnuma, Kiyoshi; Asashima, Makoto

2013-01-01

Renal lineages including kidney are derived from intermediate mesoderm, which are differentiated from a subset of caudal undifferentiated mesoderm. The inductive mechanisms of mammalian intermediate mesoderm and renal lineages are still poorly understood. Mouse embryonic stem cells (mESCs) can be a good in vitro model to reconstitute the developmental pathway of renal lineages and to analyze the mechanisms of the sequential differentiation. We examined the effects of Activin A and retinoic acid (RA) on the induction of intermediate mesoderm from mESCs under defined, serum-free, adherent, monolayer culture conditions. We measured the expression level of intermediate mesodermal marker genes and examined the developmental potential of the differentiated cells into kidney using an ex vivo transplantation assay. Adding Activin A followed by RA to mESC cultures induced the expression of marker genes and proteins for intermediate mesoderm, odd-skipped related 1 (Osr1) and Wilm’s Tumor 1 (Wt1). These differentiated cells integrated into laminin-positive tubular cells and Pax2-positive renal cells in cultured embryonic kidney explants. We demonstrated that intermediate mesodermal marker expression was also induced by RA receptor (RAR) agonist, but not by retinoid X receptor (RXR) agonists. Furthermore, the expression of these markers was decreased by RAR antagonists. We directed the differentiation of mESCs into intermediate mesoderm using Activin A and RA and revealed the role of RAR signaling in this differentiation. These methods and findings will improve our understanding of renal lineage development and could contribute to the regenerative medicine of kidney.

Intermediates in the reaction of substrate-free cytochrome P450cam with peroxy acetic acid.

PubMed

Schünemann, V; Jung, C; Trautwein, A X; Mandon, D; Weiss, R

2000-08-18

Freeze-quenched intermediates of substrate-free cytochrome 57Fe-P450(cam) in reaction with peroxy acetic acid as oxidizing agent have been characterized by EPR and Mossbauer spectroscopy. After 8 ms of reaction time the reaction mixture consists of approximately 90% of ferric low-spin iron with g-factors and hyperfine parameters of the starting material; the remaining approximately 10% are identified as a free radical (S' = 1/2) by its EPR and as an iron(IV) (S= 1) species by its Mossbauer signature. After 5 min of reaction time the intermediates have disappeared and the Mossbauer and EPR-spectra exhibit 100% of the starting material. We note that the spin-Hamiltonian analysis of the spectra of the 8 ms reactant clearly reveals that the two paramagnetic species, e.g. the ferryl (iron(IV)) species and the radical, are not exchanged coupled. This led to the conclusion that under the conditions used, peroxy acetic acid oxidized a tyrosine residue (probably Tyr-96) into a tyrosine radical (Tyr*-96), and the iron(III) center of substrate-free P450(cam) to iron(IV).

Metabolomic analysis reveals altered skeletal muscle amino acid and fatty acid handling in obese humans.

PubMed

Baker, Peter R; Boyle, Kristen E; Koves, Timothy R; Ilkayeva, Olga R; Muoio, Deborah M; Houmard, Joseph A; Friedman, Jacob E

2015-05-01

Investigate the effects of obesity and high-fat diet (HFD) exposure on fatty acid oxidation and TCA cycle intermediates and amino acids in skeletal muscle to better characterize energy metabolism. Plasma and skeletal muscle metabolomic profiles were measured from lean and obese males before and after a 5-day HFD in the 4 h postprandial condition. At both time points, plasma short-chain acylcarnitine species (SCAC) were higher in the obese subjects, while the amino acids glycine, histidine, methionine, and citrulline were lower in skeletal muscle of obese subjects. Skeletal muscle medium-chain acylcarnitines (MCAC) C6, C8, C10:2, C10:1, C10, and C12:1 increased in obese subjects, but decreased in lean subjects, from pre- to post-HFD. Plasma content of C10:1 was also decreased in the lean but increased in the obese subjects from pre- to post-HFD. CD36 increased from pre- to post-HFD in obese but not lean subjects. Lower skeletal muscle amino acid content and accumulation of plasma SCAC in obese subjects could reflect increased anaplerosis for TCA cycle intermediates, while accumulation of MCAC suggests limitations in β-oxidation. These measures may be important markers of or contributors to dysregulated metabolism observed in skeletal muscle of obese humans. © 2015 The Obesity Society.

Air Conditioning. Performance Objectives. Intermediate Course.

ERIC Educational Resources Information Center

Long, William

Several intermediate performance objectives and corresponding criterion measures are listed for each of seven terminal objectives for an intermediate air conditioning course. The titles of the seven terminal objectives are Refrigeration Cycle, Job Requirement Skills, Air Conditioning, Trouble Shooting, Performance Test, Shop Management, and S.I.E.…

SURFACE DEGRADATION OF COMPOSITE RESINS BY ACIDIC MEDICINES AND pH-CYCLING

PubMed Central

Valinoti, Ana Carolina; Neves, Beatriz Gonçalves; da Silva, Eduardo Moreira; Maia, Lucianne Cople

2008-01-01

This study evaluated the effects of acidic medicines (Dimetapp® and Claritin®), under pH-cycling conditions, on the surface degradation of four composite resins (microhybrid: TPH, Concept, Opallis and Nanofilled: Supreme). Thirty disc-shaped specimens (Ø = 5.0 mm / thickness = 2.0 mm) of each composite were randomly assigned to 3 groups (n = 10): a control and two experimental groups, according to the acidic medicines evaluated. The specimens were finished and polished with aluminum oxide discs, and the surface roughness was measured by using a profilometer. After the specimens were submitted to a pH-cycling regimen and immersion in acidic medicines for 12 days, the surface roughness was measured again. Two specimens for each material and group were analyzed by scanning electron microscopy (SEM) before and after pH-cycling. Data were analyzed by the Student's-t test, ANOVA, Duncan's multiple range test and paired t-test (α=0.05). Significant increase in roughness was found only for TPH in the control group and TPH and Supreme immersed in Claritin® (p<0.05). SEM analyses showed that the 4 composite resins underwent erosion and surface degradation after being subjected to the experimental conditions. In conclusion, although the roughness was slightly affected, the pH-cycling and acidic medicines caused surface degradation of the composite resins evaluated. Titratable acidity seemed to play a more crucial role on surface degradation of composite resins than pH. PMID:19089257

Dextranomer/hyaluronic acid endoscopic injection is effective in the treatment of intermediate and high grade vesicoureteral reflux in patients with complete duplex systems.

PubMed

Hunziker, Manuela; Mohanan, Nochiparambil; Puri, Prem

2013-05-01

Endoscopic subureteral injection of dextranomer/hyaluronic acid has become an established alternative to long-term antibiotic prophylaxis or surgical treatment for vesicoureteral reflux. We evaluated the effectiveness of endoscopic injection of dextranomer/hyaluronic acid in intermediate and high grade vesicoureteral reflux in patients with complete duplex collecting systems. A total of 123 children underwent endoscopic correction of intermediate or high grade vesicoureteral reflux using injection of dextranomer/hyaluronic acid into complete duplex systems between 2001 and 2010. Vesicoureteral reflux was diagnosed by voiding cystourethrogram, and dimercapto-succinic acid scan was performed to evaluate the presence of renal scarring. Followup ultrasound and voiding cystourethrogram were performed 3 months after the outpatient procedure and renal ultrasound thereafter every 2 years. Mean followup was 6.7 years. Complete duplex systems were unilateral in 110 patients and bilateral in 13. Reflux severity in the 136 refluxing units was grade II in 1 (0.7%), III in 52 (38.2%), IV in 61 (44.9%) and V in 22 (16.2%). Dimercapto-succinic acid scan revealed renal functional abnormalities in 63 children (51.2%). Vesicoureteral reflux resolved after the first endoscopic injection of dextranomer/hyaluronic acid in 93 ureters (68.4%), after a second injection in 35 (25.7%) and after a third injection in 8 (5.9%). Febrile urinary tract infection developed in 5 patients (4.1%) during followup. No patient required ureteral reimplantation or experienced significant complications. Our results confirm the safety and efficacy of endoscopic injection of dextranomer/hyaluronic acid in eradicating intermediate and high grade vesicoureteral reflux in patients with complete duplex systems. We recommend this minimally invasive, 15-minute outpatient procedure as a viable option for treating intermediate and high grade vesicoureteral reflux in patients with complete duplex collecting systems

Chopper-controlled discharge life cycling studies on lead-acid batteries

NASA Technical Reports Server (NTRS)

Kraml, J. J.; Ames, E. P.

1982-01-01

State-of-the-art 6 volt lead-acid golf car batteries were tested. A daily charge/discharge cycling to failure points under various chopper controlled pulsed dc and continuous current load conditions was undertaken. The cycle life and failure modes were investigated for depth of discharge, average current chopper frequency, and chopper duty cycle. It is shown that battery life is primarily and inversely related to depth of discharge and discharge current. Failure mode is characterized by a gradual capacity loss with consistent evidence of cell element aging.

Metabolic Mitigation of Staphylococcus aureus Vancomycin Intermediate-Level Susceptibility.

PubMed

Gardner, Stewart G; Marshall, Darrell D; Daum, Robert S; Powers, Robert; Somerville, Greg A

2018-01-01

Staphylococcus aureus is a major human pathogen whose infections are increasingly difficult to treat due to increased antibiotic resistance, including resistance to vancomycin. Vancomycin-intermediate S. aureus (VISA) strains develop resistance to vancomycin through adaptive changes that are incompletely understood. Central to this adaptation are metabolic changes that permit growth in the presence of vancomycin. To define the metabolic changes associated with adaptive resistance to vancomycin in S. aureus , the metabolomes of a vancomycin-sensitive and VISA strain pair isolated from the same patient shortly after vancomycin therapy began and following vancomycin treatment failure were analyzed. The metabolic adaptations included increases in acetogenesis, carbon flow through the pentose phosphate pathway, wall teichoic acid and peptidoglycan precursor biosynthesis, purine biosynthesis, and decreased tricarboxylic acid (TCA) cycle activity. The significance of these metabolic pathways for vancomycin-intermediate susceptibility was determined by assessing the synergistic potential of human-use-approved inhibitors of these pathways in combination with vancomycin against VISA strains. Importantly, inhibitors of amino sugar and purine biosynthesis acted synergistically with vancomycin to kill a diverse set of VISA strains, suggesting that combinatorial therapy could augment the efficacy of vancomycin even in patients infected with VISA strains. Copyright © 2017 American Society for Microbiology.

Conjugated linolenic acid (CLnA), conjugated linoleic acid (CLA) and other biohydrogenation intermediates in plasma and milk fat of cows fed raw or extruded linseed.

PubMed

Akraim, F; Nicot, M C; Juaneda, P; Enjalbert, F

2007-07-01

Thirty lactating dairy cows were used in a 3 × 3 Latin-square design to investigate the effects of a raw or extruded blend of linseed and wheat bran (70:30) on plasma and milk fatty-acids (FA). Linseed diets, containing 16.6% linseed blend on a dry-matter basis, decreased milk yield and protein percentage. They decreased the proportions of FA with less than 18 carbons in plasma and milk and resulted in cis-9, cis-12, cis-15 18:3 proportions that were more than three and four times higher in plasma and milk, respectively, whereas cis-9, cis-12 18:2 proportions were decreased by 10-15%. The cis-9, trans-11, cis-15 18:3 isomer of conjugated linolenic acid was not detected in the milk of control cows, but was over 0.15% of total FA in the milk fat of linseed-supplemented cows. Similarly, linseed increased plasma and milk proportions of all biohydrogenation (BH) intermediates in plasma and milk, including the main isomer of conjugated linoleic acid cis-9, trans-11 18:2, except trans-4 18:1 and cis-11, trans-15 18:2 in plasma lipids. In milk fat, compared with raw linseed, extruded linseed further reduced 6:0-16:0 even-chain FA, did not significantly affect the proportions of 18:0, cis-9 18:1 and cis-9, cis-12 18:2, tended to increase cis-9, cis-12, cis-15 18:3, and resulted in an additional increase in the proportions of most BH intermediates. It was concluded that linseed addition can improve the proportion of conjugated linoleic and linolenic acids, and that extrusion further increases the proportions of intermediates of ruminal BH in milk fat.

Anaerobic Carbon Metabolism by the Tricarboxylic Acid Cycle : Evidence for Partial Oxidative and Reductive Pathways during Dark Ammonium Assimilation.

PubMed

Vanlerberghe, G C; Horsey, A K; Weger, H G; Turpin, D H

1989-12-01

Nitrogen-limited cells of Selenastrum minutum (Naeg.) Collins are able to assimilate NH(4) (+) in the dark under anaerobic conditions. Addition of NH(4) (+) to anaerobic cells results in a threefold increase in tricarboxylic acid cycle (TCAC) CO(2) efflux and an eightfold increase in the rate of anaplerotic carbon fixation via phosphoenolpyruvate carboxylase. Both of these observations are consistent with increased TCAC carbon flow to supply intermediates for amino acid biosynthesis. Addition of H(14)CO(3) (-) to anaerobic cells assimilating NH(4) (+) results in the incorporation of radiolabel into the alpha-carboxyl carbon of glutamic acid. Incorporation of radiolabel into glutamic acid is not simply a short-term phenomenon following NH(4) (+) addition as the specific activity of glutamic acid increases over time. This indicates that this alga is able to maintain partial oxidative TCAC carbon flow while under anoxia to supply alpha-ketoglutarate for glutamate production. During dark aerobic NH(4) (+) assimilation, no radiolabel appears in fumarate or succinate and only a small amount occurs in malate. During anaerobic NH(4) (+) assimilation, these metabolites contain a large proportion of the total radiolabel and radiolabel accumulates in succinate over time. Also, the ratio of dark carbon fixation to NH(4) (+) assimilation is much higher under anaerobic than aerobic conditions. These observations suggest the operation of a partial reductive TCAC from oxaloacetic acid to malate, fumarate, and succinate. Such a pathway might contribute to redox balance in an anaerobic cell maintaining partial oxidative TCAC activity.

Long chain fatty acids and related pro-inflammatory, specialized pro-resolving lipid mediators and their intermediates in preterm human milk during the first month of lactation.

PubMed

Robinson, D T; Palac, H L; Baillif, V; Van Goethem, E; Dubourdeau, M; Van Horn, L; Martin, C R

2017-06-01

This study aimed to measure longitudinal quantities of the long chain fatty acids, their biologically active terminal metabolites and related intermediates (also called oxylipins) in preterm human milk expressed during the first month of lactation. In a prospective cohort, breast milk was collected throughout the first month of lactation in 30 women who delivered preterm infants. Eighteen bioactive lipids and their intermediates were quantified via solid phase extraction and LC-MS/MS. Analysis by GC-FID quantified the fatty acid precursors. Arachidonic acid (ARA) and docosahexaenoic acid (DHA) milk concentrations significantly declined throughout the first month. Oxylipin concentrations did not change during lactation. Positive associations existed between ARA and thromboxane B2, eicosapentaenoic acid and 18-hydroxyeicosapentaenoic acid, and between DHA and PDX and 14- and 17-hydroxydocosahexaenoic acids. DHA concentrations were 1.5 times higher and 14-HDHA was 1.7 times higher in milk from women taking DHA supplements. This investigation showed conditionally essential fatty acids, ARA and DHA, decreased in preterm milk, suggesting a need to supplement their intake for the breast milk-fed preterm infant. Positive associations between parent fatty acids, bioactive lipids and intermediates, as well as sensitivity of milk to maternal fatty acid intake, support consideration of a comprehensive approach to providing fatty acids for preterm infants through both maternal and infant supplementation. Copyright © 2017 Elsevier Ltd. All rights reserved.

Pentadecanoic and Heptadecanoic Acids: Multifaceted Odd-Chain Fatty Acids12

PubMed Central

Pfeuffer, Maria; Jaudszus, Anke

2016-01-01

The odd-chain fatty acids (OCFAs) pentadecanoic acid (15:0) and heptadecanoic acid (17:0), which account for only a small proportion of total saturated fatty acids in milk fat and ruminant meat, are accepted biomarkers of dairy fat intake. However, they can also be synthesized endogenously, for example, from gut-derived propionic acid (3:0). A number of studies have shown an inverse association between OCFA concentrations in human plasma phospholipids or RBCs and risk of type 2 diabetes and cardiovascular disease. We propose a possible involvement in metabolic regulation from the assumption that there is a link between 15:0 and 17:0 and the metabolism of other short-chain, medium-chain, and longer-chain OCFAs. The OCFAs 15:0 and 17:0 can be elongated to very-long-chain FAs (VLCFAs) such as tricosanoic acid (23:0) and pentacosanoic acid (25:0) in glycosphingolipids, particularly found in brain tissue, or can be derived from these VLCFAs. Their chains can be shortened, yielding propionyl-coenzyme A (CoA). Propionyl-CoA, by succinyl-CoA, can replenish the citric acid cycle (CAC) with anaplerotic intermediates and, thus, improve mitochondrial energy metabolism. Mitochondrial function is compromised in a number of disorders and may be impaired with increasing age. Optimizing anaplerotic intermediate availability for the CAC may help to cope with demands in times of increased metabolic stress and with aging. OCFAs may serve as substrates for synthesis of both odd-numbered VLCFAs and propionyl-CoA or store away excess propionic acid. PMID:27422507

Systematic engineering of TCA cycle for optimal production of a four-carbon platform chemical 4-hydroxybutyric acid in Escherichia coli.

PubMed

Choi, Sol; Kim, Hyun Uk; Kim, Tae Yong; Lee, Sang Yup

2016-11-01

To address climate change and environmental problems, it is becoming increasingly important to establish biorefineries for the production of chemicals from renewable non-food biomass. Here we report the development of Escherichia coli strains capable of overproducing a four-carbon platform chemical 4-hybroxybutyric acid (4-HB). Because 4-HB production is significantly affected by aeration level, genome-scale metabolic model-based engineering strategies were designed under aerobic and microaerobic conditions with emphasis on oxidative/reductive TCA branches and glyoxylate shunt. Several different metabolic engineering strategies were employed to develop strains suitable for fermentation both under aerobic and microaerobic conditions. It was found that microaerobic condition was more efficient than aerobic condition in achieving higher titer and productivity of 4-HB. The final engineered strain produced 103.4g/L of 4-HB by microaerobic fed-batch fermentation using glycerol. The aeration-dependent optimization strategy of TCA cycle will be useful for developing microbial strains producing other reduced derivative chemicals of TCA cycle intermediates. Copyright © 2016 International Metabolic Engineering Society. Published by Elsevier Inc. All rights reserved.

Metabolite profiling of human colon carcinoma--deregulation of TCA cycle and amino acid turnover.

PubMed

Denkert, Carsten; Budczies, Jan; Weichert, Wilko; Wohlgemuth, Gert; Scholz, Martin; Kind, Tobias; Niesporek, Silvia; Noske, Aurelia; Buckendahl, Anna; Dietel, Manfred; Fiehn, Oliver

2008-09-18

Apart from genetic alterations, development and progression of colorectal cancer has been linked to influences from nutritional intake, hyperalimentation, and cellular metabolic changes that may be the basis for new diagnostic and therapeutic approaches. However, in contrast to genomics and proteomics, comprehensive metabolomic investigations of alterations in malignant tumors have rarely been conducted. In this study we investigated a set of paired samples of normal colon tissue and colorectal cancer tissue with gas-chromatography time-of-flight mass-spectrometry, which resulted in robust detection of a total of 206 metabolites. Metabolic phenotypes of colon cancer and normal tissues were different at a Bonferroni corrected significance level of p=0.00170 and p=0.00005 for the first two components of an unsupervised PCA analysis. Subsequent supervised analysis found 82 metabolites to be significantly different at p<0.01. Metabolites were connected to abnormalities in metabolic pathways by a new approach that calculates the distance of each pair of metabolites in the KEGG database interaction lattice. Intermediates of the TCA cycle and lipids were found down-regulated in cancer, whereas urea cycle metabolites, purines, pyrimidines and amino acids were generally found at higher levels compared to normal colon mucosa. This study demonstrates that metabolic profiling facilitates biochemical phenotyping of normal and neoplastic colon tissue at high significance levels and points to GC-TOF-based metabolomics as a new method for molecular pathology investigations.

Criegee intermediates and their impacts on the troposphere

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khan, M. A. H.; Percival, C. J.; Caravan, R. L.

We report Criegee intermediates (CIs), carbonyl oxides formed in ozonolysis of alkenes, play key roles in the troposphere. The decomposition of CIs can be a significant source of OH to the tropospheric oxidation cycle especially during nighttime and winter months. A variety of model-measurement studies have estimated surface-level stabilized Criegee intermediate (sCI) concentrations on the order of 1 × 10 4 cm -3 to 1 × 10 5 cm -3, which makes a non-negligible contribution to the oxidising capacity in the terrestrial boundary layer. The reactions of sCI with the water monomer and the water dimer have been found tomore » be the most important bimolecular reactions to the tropospheric sCI loss rate, at least for the smallest carbonyl oxides; the products from these reactions (e.g. hydroxymethyl hydroperoxide, HMHP) are also of importance to the atmospheric oxidation cycle. The sCI can oxidise SO 2 to form SO 3, which can go on to form a significant amount of H 2SO 4 which is a key atmospheric nucleation species and therefore vital to the formation of clouds. Lastly, the sCI can also react with carboxylic acids, carbonyl compounds, alcohols, peroxy radicals and hydroperoxides, and the products of these reactions are likely to be highly oxygenated species, with low vapour pressures, that can lead to nucleation and SOA formation over terrestrial regions.« less

Criegee intermediates and their impacts on the troposphere

DOE PAGES

Khan, M. A. H.; Percival, C. J.; Caravan, R. L.; ...

2018-02-15

We report Criegee intermediates (CIs), carbonyl oxides formed in ozonolysis of alkenes, play key roles in the troposphere. The decomposition of CIs can be a significant source of OH to the tropospheric oxidation cycle especially during nighttime and winter months. A variety of model-measurement studies have estimated surface-level stabilized Criegee intermediate (sCI) concentrations on the order of 1 × 10 4 cm -3 to 1 × 10 5 cm -3, which makes a non-negligible contribution to the oxidising capacity in the terrestrial boundary layer. The reactions of sCI with the water monomer and the water dimer have been found tomore » be the most important bimolecular reactions to the tropospheric sCI loss rate, at least for the smallest carbonyl oxides; the products from these reactions (e.g. hydroxymethyl hydroperoxide, HMHP) are also of importance to the atmospheric oxidation cycle. The sCI can oxidise SO 2 to form SO 3, which can go on to form a significant amount of H 2SO 4 which is a key atmospheric nucleation species and therefore vital to the formation of clouds. Lastly, the sCI can also react with carboxylic acids, carbonyl compounds, alcohols, peroxy radicals and hydroperoxides, and the products of these reactions are likely to be highly oxygenated species, with low vapour pressures, that can lead to nucleation and SOA formation over terrestrial regions.« less

Triiodothyronine increases myocardial function and pyruvate entry into the citric acid cycle after reperfusion in a model of infant cardiopulmonary bypass

PubMed Central

Olson, Aaron K.; Bouchard, Bertrand; Ning, Xue-Han; Isern, Nancy; Rosiers, Christine Des

2012-01-01

Triiodothyronine (T3) supplementation improves clinical outcomes in infants after cardiac surgery using cardiopulmonary bypass by unknown mechanisms. We utilized a translational model of infant cardiopulmonary bypass to test the hypothesis that T3 modulates pyruvate entry into the citric acid cycle (CAC), thereby providing the energy support for improved cardiac function after ischemia-reperfusion (I/R). Neonatal piglets received intracoronary [2-13Carbon(13C)]pyruvate for 40 min (8 mM) during control aerobic conditions (control) or immediately after reperfusion (I/R) from global hypothermic ischemia. A third group (I/R-Tr) received T3 (1.2 μg/kg) during reperfusion. We assessed absolute CAC intermediate levels and flux parameters into the CAC through oxidative pyruvate decarboxylation (PDC) and anaplerotic carboxylation (PC) using [2-13C]pyruvate and isotopomer analysis by gas and liquid chromatography-mass spectrometry and 13C-nuclear magnetic resonance spectroscopy. When compared with I/R, T3 (group I/R-Tr) increased cardiac power and oxygen consumption after I/R while elevating flux of both PDC and PC (∼4-fold). Although neither I/R nor I/R-Tr modified absolute CAC levels, T3 inhibited I/R-induced reductions in their molar percent enrichment. Furthermore, 13C-labeling of CAC intermediates suggests that T3 may decrease entry of unlabeled carbons at the level of oxaloacetate through anaplerosis or exchange reaction with asparate. T3 markedly enhances PC and PDC fluxes, thereby providing potential substrate for elevated cardiac function after reperfusion. This T3-induced increase in pyruvate fluxes occurs with preservation of the CAC intermediate pool. Our labeling data raise the possibility that T3 reduces reliance on amino acids for anaplerosis after reperfusion. PMID:22180654

Time-resolved resonance Raman spectroscopy of intermediates of bacteriorhodopsin: The bK(590) intermediate.

PubMed

Terner, J; Hsieh, C L; Burns, A R; El-Sayed, M A

1979-07-01

We have combined microbeam and flow techniques with computer subtraction methods to obtain the resonance Raman spectrum of the short lived batho-intermediate (bK(590)) of bacteriorhodopsin. Comparison of the spectra obtained in (1)H(2)O and (2)H(2)O, as well as the fact that the bK(590) intermediate shows large optical red shifts, suggests that the Schiff base linkage of this intermediate is protonated. The fingerprint region of the spectrum of bK(590), sensitive to the isomeric configuration of the retinal chromophore, does not resemble the corresponding region of the parent bR(570) form. The resonance Raman spectrum of bK(590) as well as the spectra of all of the other main intermediates in the photoreaction cycle of bacteriorhodopsin are discussed and compared with resonance Raman spectra of published model compounds.

Chemically Activated Formation of Organic Acids in Reactions of the Criegee Intermediate with Aldehydes and Ketones

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jalan, Amrit; Allen, Joshua W.; Green, William H.

Reactions of the Criegee intermediate (CI, .CH2OO.) are important in atmospheric ozonolysis models. In this work, we compute the rates for reactions between .CH2OO. and HCHO, CH3CHO and CH3COCH3 leading to the formation of secondary ozonides (SOZ) and organic acids. Relative to infinitely separated reactants, the SOZ in all three cases is found to be 48–51 kcal mol-1 lower in energy, formed via 1,3- cycloaddition of .CH2OO. across the CQO bond. The lowest energy pathway found for SOZ decomposition is intramolecular disproportionation of the singlet biradical intermediate formed from cleavage of the O–O bond to form hydroxyalkyl esters. These hydroxyalkylmore » esters undergo concerted decomposition providing a low energy pathway from SOZ to acids. Geometries and frequencies of all stationary points were obtained using the B3LYP/MG3S DFT model chemistry, and energies were refined using RCCSD(T)-F12a/cc-pVTZ-F12 single-point calculations. RRKM calculations were used to obtain microcanonical rate coefficients (k(E)) and the reservoir state method was used to obtain temperature and pressure dependent rate coefficients (k(T, P)) and product branching ratios. At atmospheric pressure, the yield of collisionally stabilized SOZ was found to increase in the order HCHO o CH3CHO o CH3COCH3 (the highest yield being 10-4 times lower than the initial .CH2OO. concentration). At low pressures, chemically activated formation of organic acids (formic acid in the case of HCHO and CH3COCH3, formic and acetic acid in the case of CH3CHO) was found to be the major product channel in agreement with recent direct measurements. Collisional energy transfer parameters and the barrier heights for SOZ reactions were found to be the most sensitive parameters determining SOZ and organic acid yield.« less

Alternative carbohydrate reserves used in the daily cycle of crassulacean acid metabolism

Treesearch

C.C. Black; J.-Q. Chen; R.L. Doong; M.N. Angelov; Shi-Jean S. Sung

1996-01-01

Each day a massive interlocked biochemical cycle occurs in the green tissues of crassulacean acid metabolism plants.The function of this interlocked cycle, in its simplest context, is to furnish most of the CO2 for CAM plant photosynthesis.In this unified presentation our aims are (1) to divide CAM plants into two metabolic groups, (2) to...

Salicylic acid antagonizes abscisic acid inhibition of shoot growth and cell cycle progression in rice

NASA Astrophysics Data System (ADS)

Meguro, Ayano; Sato, Yutaka

2014-04-01

We analysed effects of abscisic acid (ABA, a negative regulatory hormone), alone and in combination with positive or neutral hormones, including salicylic acid (SA), on rice growth and expression of cell cycle-related genes. ABA significantly inhibited shoot growth and induced expression of OsKRP4, OsKRP5, and OsKRP6. A yeast two-hybrid assay showed that OsKRP4, OsKRP5, and OsKRP6 interacted with OsCDKA;1 and/or OsCDKA;2. When SA was simultaneously supplied with ABA, the antagonistic effect of SA completely blocked ABA inhibition. SA also blocked ABA inhibition of DNA replication and thymidine incorporation in the shoot apical meristem. These results suggest that ABA arrests cell cycle progression by inducing expression of OsKRP4, OsKRP5, and OsKRP6, which inhibit the G1/S transition, and that SA antagonizes ABA by blocking expression of OsKRP genes.

Regional and global impacts of Criegee intermediates on atmospheric sulphuric acid concentrations and first steps of aerosol formation.

PubMed

Percival, Carl J; Welz, Oliver; Eskola, Arkke J; Savee, John D; Osborn, David L; Topping, David O; Lowe, Douglas; Utembe, Steven R; Bacak, Asan; McFiggans, Gordon; Cooke, Michael C; Xiao, Ping; Archibald, Alexander T; Jenkin, Michael E; Derwent, Richard G; Riipinen, Ilona; Mok, Daniel W K; Lee, Edmond P F; Dyke, John M; Taatjes, Craig A; Shallcross, Dudley E

2013-01-01

Carbonyl oxides ("Criegee intermediates"), formed in the ozonolysis of alkenes, are key species in tropospheric oxidation of organic molecules and their decomposition provides a non-photolytic source of OH in the atmosphere (Johnson and Marston, Chem. Soc. Rev., 2008, 37, 699, Harrison et al, Sci, Total Environ., 2006, 360, 5, Gäb et al., Nature, 1985, 316, 535, ref. 1-3). Recently it was shown that small Criegee intermediates, C.I.'s, react far more rapidly with SO2 than typically represented in tropospheric models, (Welz, Science, 2012, 335, 204, ref. 4) which suggested that carbonyl oxides could have a substantial influence on the atmospheric oxidation of SO2. Oxidation of 502 is the main atmospheric source of sulphuric acid (H2SO4), which is a critical contributor to aerosol formation, although questions remain about the fundamental nucleation mechanism (Sipilä et al., Science, 2010, 327, 1243, Metzger et al., Proc. Natl. Acad. Sci. U. S. A., 2010 107, 6646, Kirkby et al., Nature, 2011, 476, 429, ref. 5-7). Non-absorbing atmospheric aerosols, by scattering incoming solar radiation and acting as cloud condensation nuclei, have a cooling effect on climate (Intergovernmental Panel on Climate Change (IPCC), Climate Change 2007: The Physical Science Basis, Cambridge University Press, 2007, ref. 8). Here we explore the effect of the Criegees on atmospheric chemistry, and demonstrate that ozonolysis of alkenes via the reaction of Criegee intermediates potentially has a large impact on atmospheric sulphuric acid concentrations and consequently the first steps in aerosol production. Reactions of Criegee intermediates with SO2 will compete with and in places dominate over the reaction of OH with SO2 (the only other known gas-phase source of H2SO4) in many areas of the Earth's surface. In the case that the products of Criegee intermediate reactions predominantly result in H2SO4 formation, modelled particle nucleation rates can be substantially increased by the improved

Role of Intermediate Filaments in Vesicular Traffic.

PubMed

Margiotta, Azzurra; Bucci, Cecilia

2016-04-25

Intermediate filaments are an important component of the cellular cytoskeleton. The first established role attributed to intermediate filaments was the mechanical support to cells. However, it is now clear that intermediate filaments have many different roles affecting a variety of other biological functions, such as the organization of microtubules and microfilaments, the regulation of nuclear structure and activity, the control of cell cycle and the regulation of signal transduction pathways. Furthermore, a number of intermediate filament proteins have been involved in the acquisition of tumorigenic properties. Over the last years, a strong involvement of intermediate filament proteins in the regulation of several aspects of intracellular trafficking has strongly emerged. Here, we review the functions of intermediate filaments proteins focusing mainly on the recent knowledge gained from the discovery that intermediate filaments associate with key proteins of the vesicular membrane transport machinery. In particular, we analyze the current understanding of the contribution of intermediate filaments to the endocytic pathway.

An allene oxide and 12-oxophytodienoic acid are key intermediates in jasmonic acid biosynthesis by Fusarium oxysporum.

PubMed

Oliw, Ernst H; Hamberg, Mats

2017-08-01

Fungi can produce jasmonic acid (JA) and its isoleucine conjugate in large quantities, but little is known about the biosynthesis. Plants form JA from 18:3 n -3 by 13 S -lipoxygenase (LOX), allene oxide synthase, and allene oxide cyclase. Shaking cultures of Fusarium oxysporum f. sp. tulipae released over 200 mg of jasmonates per liter. Nitrogen powder of the mycelia expressed 10 R -dioxygenase-epoxy alcohol synthase activities, which was confirmed by comparison with the recombinant enzyme. The 13 S -LOX of F. oxysporum could not be detected in the cell-free preparations. Incubation of mycelia in phosphate buffer with [17,17,18,18,18- 2 H 5 ]18:3 n -3 led to biosynthesis of a [ 2 H 5 ]12-oxo-13-hydroxy-9 Z ,15 Z -octadecadienoic acid (α-ketol), [ 2 H 5 ]12-oxo-10,15 Z -phytodienoic acid (12-OPDA), and [ 2 H 5 ]13-keto- and [ 2 H 5 ]13 S -hydroxyoctadecatrienoic acids. The α-ketol consisted of 90% of the 13 R stereoisomer, suggesting its formation by nonenzymatic hydrolysis of an allene oxide with 13 S configuration. Labeled and unlabeled 12-OPDA were observed following incubation with 0.1 mM [ 2 H 5 ]18:3 n -3 in a ratio from 0.4:1 up to 47:1 by mycelia of liquid cultures of different ages, whereas 10 times higher concentration of [ 2 H 5 ]13 S -hydroperoxyoctadecatrienoic acid was required to detect biosynthesis of [ 2 H 5 ]12-OPDA. The allene oxide is likely formed by a cytochrome P450 or catalase-related hydroperoxidase. We conclude that F. oxysporum , like plants, forms jasmonates with an allene oxide and 12-OPDA as intermediates. Copyright © 2017 by the American Society for Biochemistry and Molecular Biology, Inc.

Halogenated methanesulfonic acids: A new class of organic micropollutants in the water cycle.

PubMed

Zahn, Daniel; Frömel, Tobias; Knepper, Thomas P

2016-09-15

Mobile and persistent organic micropollutants may impact raw and drinking waters and are thus of concern for human health. To identify such possible substances of concern nineteen water samples from five European countries (France, Switzerland, The Netherlands, Spain and Germany) and different compartments of the water cycle (urban effluent, surface water, ground water and drinking water) were enriched with mixed-mode solid phase extraction. Hydrophilic interaction liquid chromatography - high resolution mass spectrometry non-target screening of these samples led to the detection and structural elucidation of seven novel organic micropollutants. One structure could already be confirmed by a reference standard (trifluoromethanesulfonic acid) and six were tentatively identified based on experimental evidence (chloromethanesulfonic acid, dichloromethanesulfonic acid, trichloromethanesulfonic acid, bromomethanesulfonic acid, dibromomethanesulfonic acid and bromochloromethanesulfonic acid). Approximated concentrations for these substances show that trifluoromethanesulfonic acid, a chemical registered under the European Union regulation REACH with a production volume of more than 100 t/a, is able to spread along the water cycle and may be present in concentrations up to the μg/L range. Chlorinated and brominated methanesulfonic acids were predominantly detected together which indicates a common source and first experimental evidence points towards water disinfection as a potential origin. Halogenated methanesulfonic acids were detected in drinking waters and thus may be new substances of concern. Copyright © 2016 Elsevier Ltd. All rights reserved.

Prebiotic Amino Acid Thioester Synthesis: Thiol-Dependent Amino Acid Synthesis from Formose substrates (Formaldehyde and Glycolaldehyde) and Ammonia

NASA Technical Reports Server (NTRS)

Weber, Arthur L.

1998-01-01

Formaldehyde and glycolaldehyde (substrates of the formose autocatalytic cycle) were shown to react with ammonia yielding alanine and homoserine under mild aqueous conditions in the presence of thiol catalysts. Since similar reactions carried out without ammonia yielded alpha-hydroxy acid thioesters, the thiol-dependent synthesis of alanine and homoserine is presumed to occur via amino acid thioesters-intermediates capable of forming peptides. A pH 5.2 solution of 20 mM formaldehyde, 20 mM glycolaldehyde, 20 mM ammonium chloride, 23 mM 3-mercaptopropionic acid, and 23 mM acetic acid that reacted for 35 days at 40 C yielded (based on initial formaldehyde) 1.8% alanine and 0.08% homoserine. In the absence of thiol catalyst, the synthesis of alanine and homoserine was negligible. Alanine synthesis required both formaldehyde and glycolaldehyde, but homoserine synthesis required only glycolaldehyde. At 25 days the efficiency of alanine synthesis calculated from the ratio of alanine synthesized to formaldehyde reacted was 2.1%, and the yield (based on initial formaldehyde) of triose and tetrose intermediates involved in alanine and homoserine synthesis was 0.3 and 2.1%, respectively. Alanine synthesis was also seen in similar reactions containing only 10 mM each of aldehyde substrates, ammonia, and thiol. The prebiotic significance of these reactions that use the formose reaction to generate sugar intermediates that are converted to reactive amino acid thioesters is discussed.

Improved amino acid, bioenergetic metabolite and neurotransmitter profiles following human amnion epithelial cell transplant in intermediate maple syrup urine disease mice.

PubMed

Skvorak, Kristen J; Dorko, Kenneth; Marongiu, Fabio; Tahan, Veysel; Hansel, Marc C; Gramignoli, Roberto; Arning, Erland; Bottiglieri, Teodoro; Gibson, K Michael; Strom, Stephen C

2013-06-01

Orthotopic liver transplant (OLT) significantly improves patient outcomes in maple syrup urine disease (MSUD; OMIM: 248600), yet organ shortages point to the need for alternative therapies. Hepatocyte transplantation has shown both clinical and preclinical efficacy as an intervention for metabolic liver diseases, yet the availability of suitable livers for hepatocyte isolation is also limited. Conversely, human amnion epithelial cells (hAEC) may have utility as a hepatocyte substitute, and they share many of the characteristics of pluripotent embryonic stem cells while lacking their safety and ethical concerns. We reported that like hepatocytes, transplantation of hAEC significantly improved survival and lifespan, normalized body weight, and significantly improved branched-chain amino acid (BCAA) levels in sera and brain in a transgenic murine model of intermediate maple syrup urine disease (imsud). In the current report, we detail the neural and peripheral metabolic improvements associated with hAEC transplant in imsud mice, including amino acids associated with bioenergetics, the urea cycle, as well as the neurotransmitter systems for serotonin, dopamine, and gamma-aminobutyric acid (GABA). This stem cell therapy results in significant global correction of the metabolic profile that characterizes the disease, both in the periphery and the central nervous system, the target organ for toxicity in iMSUD. The significant correction of the disease phenotype, coupled with the theoretical benefits of hAEC, particularly their lack of immunogenicity and tumorigenicity, suggests that human amnion epithelial cells deserve serious consideration for clinical application to treat metabolic liver diseases. Copyright © 2013. Published by Elsevier Inc.

Spectroscopic characterization of the iron-oxo intermediate in cytochrome P450.

PubMed

Jung, Christiane; Schünemann, Volker; Lendzian, Friedhelm; Trautwein, Alfred X; Contzen, Jörg; Galander, Marcus; Böttger, Lars H; Richter, Matthias; Barra, Anne-Laure

2005-10-01

From analogy to chloroperoxidase from Caldariomyces fumago, it is believed that the electronic structure of the intermediate iron-oxo species in the catalytic cycle of cytochrome P450 corresponds to an iron(IV) porphyrin-pi-cation radical (compound I). However, our recent studies on P450cam revealed that after 8 ms a tyrosine radical and iron(IV) were formed in the reaction of ferric P450 with external oxidants in the shunt pathway. The present study on the heme domain of P450BM3 (P450BMP) shows a similar result. In addition to a tyrosine radical, a contribution from a tryptophan radical was found in the electron paramagnetic resonance (EPR) spectra of P450BMP. Here we present comparative multi-frequency EPR (9.6, 94 and 285 GHz) and Mössbauer spectroscopic studies on freeze-quenched intermediates produced using peroxy acetic acid as oxidant for both P450 cytochromes. After 8 ms in both systems, amino acid radicals occurred instead of the proposed iron(IV) porphyrin-pi-cation radical, which may be transiently formed on a much faster time scale. These findings are discussed with respect to other heme thiolate proteins. Our studies demonstrate that intramolecular electron transfer from aromatic amino acids is a common feature in these enzymes. The electron transfer quenches the presumably transiently formed porphyrin-pi-cation radical, which makes it extremely difficult to trap compound I.

Production of Caproic Acid from Mixed Organic Waste: An Environmental Life Cycle Perspective

PubMed Central

2017-01-01

Caproic acid is an emerging platform chemical with diverse applications. Recently, a novel biorefinery process, that is, chain elongation, was developed to convert mixed organic waste and ethanol into renewable caproic acids. In the coming years, this process may become commercialized, and continuing to improve on the basis of numerous ongoing technological and microbiological studies. This study aims to analyze the environmental performance of caproic acid production from mixed organic waste via chain elongation at this current, early stage of technological development. To this end, a life cycle assessment (LCA) was performed to evaluate the environmental impact of producing 1 kg caproic acid from organic waste via chain elongation, in both a lab-scale and a pilot-scale system. Two mixed organic waste were used as substrates: the organic fraction of municipal solid waste (OFMSW) and supermarket food waste (SFW). Ethanol use was found to be the dominant cause of environmental impact over the life cycle. Extraction solvent recovery was found to be a crucial uncertainty that may have a substantial influence on the life-cycle impacts. We recommend that future research and industrial producers focus on the reduction of ethanol use in chain elongation and improve the recovery efficiency of the extraction solvent. PMID:28513150

Clinical benefit using sperm hyaluronic acid binding technique in ICSI cycles: a systematic review and meta-analysis.

PubMed

Beck-Fruchter, Ronit; Shalev, Eliezer; Weiss, Amir

2016-03-01

The human oocyte is surrounded by hyaluronic acid, which acts as a natural selector of spermatozoa. Human sperm that express hyaluronic acid receptors and bind to hyaluronic acid have normal shape, minimal DNA fragmentation and low frequency of chromosomal aneuploidies. Use of hyaluronic acid binding assays in intracytoplasmic sperm injection (ICSI) cycles to improve clinical outcomes has been studied, although none of these studies had sufficient statistical power. In this systematic review and meta-analysis, electronic databases were searched up to June 2015 to identify studies of ICSI cycles in which spermatozoa able to bind hyaluronic acid was selected. The main outcomes were fertilization rate and clinical pregnancy rate. Secondary outcomes included cleavage rate, embryo quality, implantation rate, spontaneous abortion and live birth rate. Seven studies and 1437 cycles were included. Use of hyaluronic acid binding sperm selection technique yielded no improvement in fertilization and pregnancy rates. A meta-analysis of all available studies showed an improvement in embryo quality and implantation rate; an analysis of prospective studies only showed an improvement in embryo quality. Evidence does not support routine use of hyaluronic acid binding assays in all ICSI cycles. Identification of patients that might benefit from this technique needs further study. Copyright © 2015 Reproductive Healthcare Ltd. Published by Elsevier Ltd. All rights reserved.

Synthesis of Enantiomerically Pure 6-Substituted-Piperazine-2-Acetic Acid Esters as Intermediates for Library Production.

PubMed

Chamakuri, Srinivas; Jain, Prashi; Guduru, Shiva Krishna Reddy; Arney, Joseph Winston; MacKenzie, Kevin; Santini, Conrad; Young, Damian W

2018-05-11

Amino acids from the chiral pool have been used to produce a 24-member branch of 2,6-disubstituted piperazine scaffolds suitable for use in compound library production. Each scaffold was obtained as a single absolute stereoisomer in multi-gram quantities. Stereochemistry was confirmed by 2D NMR protocols and enantiomeric purity was determined by chiral HPLC. The scaffolds are intended for use as intermediates in parallel synthesis of small-molecule libraries.

Changes in sodium and uric acid concentrations in plasma during the menstrual cycle.

PubMed

Mira, M; Stewart, P M; Gebski, V; Llewellyn-Jones, D; Abraham, S F

1984-03-01

Hormonal changes during the menstrual cycle are well documented, but many other biochemical variables have not been studied. We find that in the luteal phase of the menstrual cycle the concentrations of sodium and uric acid are significantly lower. The changes may be of significance for the determination of the normal reference interval.

Imbricatolic acid from Juniperus communis L. prevents cell cycle progression in CaLu-6 cells.

PubMed

De Marino, Simona; Cattaneo, Fabio; Festa, Carmen; Zollo, Franco; Iaccio, Annalisa; Ammendola, Rosario; Incollingo, Filomena; Iorizzi, Maria

2011-11-01

Imbricatolic acid was isolated from the methanolic extract of the fresh ripe berries of Juniperus communis (Cupressaceae) together with sixteen known compounds and a new dihydrobenzofuran lignan glycoside named juniperoside A. Their structures were determined by spectroscopic methods and by comparison with the spectral data reported in literature. Imbricatolic acid was evaluated for its ability to prevent cell cycle progression in p53-null CaLu-6 cells. This compound induces the upregulation of cyclin-dependent kinase inhibitors and their accumulation in the G1 phase of the cell cycle, as well as the degradation of cyclins A, D1, and E1. Furthermore, no significant imbricatolic acid-induced apoptosis was observed. Therefore, this plant-derived compound may play a role in the control of cell cycle. © Georg Thieme Verlag KG Stuttgart · New York.

Krebs Cycle Intermediates Protective against Oxidative Stress by Modulating the Level of Reactive Oxygen Species in Neuronal HT22 Cells.

PubMed

Sawa, Kenta; Uematsu, Takumi; Korenaga, Yusuke; Hirasawa, Ryuya; Kikuchi, Masatoshi; Murata, Kyohei; Zhang, Jian; Gai, Xiaoqing; Sakamoto, Kazuichi; Koyama, Tomoyuki; Satoh, Takumi

2017-03-16

Krebs cycle intermediates (KCIs) are reported to function as energy substrates in mitochondria and to exert antioxidants effects on the brain. The present study was designed to identify which KCIs are effective neuroprotective compounds against oxidative stress in neuronal cells. Here we found that pyruvate, oxaloacetate, and α-ketoglutarate, but not lactate, citrate, iso-citrate, succinate, fumarate, or malate, protected HT22 cells against hydrogen peroxide-mediated toxicity. These three intermediates reduced the production of hydrogen peroxide-activated reactive oxygen species, measured in terms of 2',7'-dichlorofluorescein diacetate fluorescence. In contrast, none of the KCIs-used at 1 mM-protected against cell death induced by high concentrations of glutamate-another type of oxidative stress-induced neuronal cell death. Because these protective KCIs did not have any toxic effects (at least up to 10 mM), they have potential use for therapeutic intervention against chronic neurodegenerative diseases.

The effect of propionic acid and valeric acid on the cell cycle in root meristems of Pisum sativum

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tramontano, W.A.; Yang, Shauyu; Delillo, A.R.

1990-01-01

Propionic acid and valeric acid at 1mM reduced the mitotic index of root meristem cells of Pisum sativum to < 1% after 12 hr in aerated White's medium. This effect varied with different acid concentrations. After a 12 hr exposure to either acid, seedlings transferred to fresh medium without either acid, resumed their normal mitotic index after 12 hr, with a burst of mitosis 8 hr post-transfer. Exposure of root meristem cells to either acid also inhibited ({sup 3}H)-TdR incorporation. Neither acid significantly altered the distribution of meristematic cells in G1 and G2 after 12 hr. The incorporation of ({supmore » 3}H) - uridine was also unaltered by the addition of either acid. This information suggests that propionic acid and valeric acid, limit progression through the cell cycle by inhibiting DNA synthesis and arresting cells in G1 and G2. These results were consistent with previous data which utilized butyric acid.« less

Evolution of trophic transmission in parasites: Why add intermediate hosts?

USGS Publications Warehouse

Choisy, Marc; Brown, Sam P.; Lafferty, Kevin D.; Thomas, Frédéric

2003-01-01

Although multihost complex life cycles (CLCs) are common in several distantly related groups of parasites, their evolution remains poorly understood. In this article, we argue that under particular circumstances, adding a second host to a single-host life cycle is likely to enhance transmission (i.e., reaching the target host). For instance, in several situations, the propagules of a parasite exploiting a predator species will achieve a higher host-finding success by encysting in a prey of the target predator than by other dispersal modes. In such a case, selection should favor the transition from a singleto a two-host life cycle that includes the prey species as an intermediate host. We use an optimality model to explore this idea, and we discuss it in relation to dispersal strategies known among free-living species, especially animal dispersal. The model found that selection favored a complex life cycle only if intermediate hosts were more abundant than definitive hosts. The selective value of a complex life cycle increased with predation rates by definitive hosts on intermediate hosts. In exploring trade-offs between transmission strategies, we found that more costly trade-offs made it more difficult to evolve a CLC while less costly trade-offs between traits could favor a mixed strategy.

Serum Amino Acid Profiling in Citrin-Deficient Children Exhibiting Normal Liver Function During the Apparently Healthy Period.

PubMed

Miyazaki, Teruo; Nagasaka, Hironori; Komatsu, Haruki; Inui, Ayano; Morioka, Ichiro; Tsukahara, Hirokazu; Kaji, Shunsaku; Hirayama, Satoshi; Miida, Takashi; Kondou, Hiroki; Ihara, Kenji; Yagi, Mariko; Kizaki, Zenro; Bessho, Kazuhiko; Kodama, Takahiro; Iijima, Kazumoto; Yorifuji, Tohru; Matsuzaki, Yasushi; Honda, Akira

2018-04-14

Citrin (mitochondrial aspartate-glutamate transporter) deficiency causes the failures in both carbohydrate-energy metabolism and the urea cycle, and the alterations in the serum levels of several amino acids in the stages of newborn (NICCD) and adult (CTLN2). However, the clinical manifestations are resolved between the NICCD and CTLN2, but the reasons are still unclear. This study evaluated the serum amino acid profile in citrin-deficient children during the healthy stage. Using HPLC-MS/MS analysis, serum amino acids were evaluated among 20 citrin-deficient children aged 5-13 years exhibiting normal liver function and 35 age-matched healthy controls. The alterations in serum amino acids characterized in the NICCD and CTLN2 stages were not observed in the citrin-deficient children. Amino acids involved in the urea cycle, including arginine, ornithine, citrulline, and aspartate, were comparable in the citrin-deficient children to the respective control levels, but serum urea was twofold higher, suggestive of a functional urea cycle. The blood sugar level was normal, but glucogenic amino acids and glutamine were significantly decreased in the citrin-deficient children compared to those in the controls. In addition, significant increases of ketogenic amino acids, branched-chain amino acids (BCAAs), a valine intermediate 3-hydroxyisobutyrate, and β-alanine were also found in the citrin-deficient children. The profile of serum amino acids in the citrin-deficient children during the healthy stage showed different characteristics from the NICCD and CTLN2 stages, suggesting that the failures in both urea cycle function and energy metabolism might be compensated by amino acid metabolism. In the citrin-deficient children during the healthy stage, the characteristics of serum amino acids, including decrease of glucogenic amino acids, and increase of ketogenic amino acids, BCAAs, valine intermediate, and β-alanine, were found by comparison to the age-matched healthy control

Synthesis of the 1-Monoester of 2-Ketoalkanedioic Acids, e.g., Octyl α-Ketoglutarate

PubMed Central

Jung, Michael E.; Deng, Gang

2012-01-01

Oxidative cleavage of cycloalkene-1-carboxylates, made from the corresponding carboxylic acids, and subsequent oxidation of the resulting ketoaldehyde afforded the important 1-monoesters of 2-ketoalkanedioic acids. Thus ozonolysis of octyl cyclobutene-1-carboxylate followed by sodium chlorite oxidation afforded the 1-monooctyl 2-ketoglutarate. This is a cell-permeable prodrug form of α-ketoglutarate, an important intermediate in the tricarboxylic acid (TCA, Krebs) cycle and a promising therapeutic agent in its own right. PMID:23163977

Nickel deficiency disrupts metabolism of ureides, amino acids, and organic acids of young pecan foliage.

PubMed

Bai, Cheng; Reilly, Charles C; Wood, Bruce W

2006-02-01

The existence of nickel (Ni) deficiency is becoming increasingly apparent in crops, especially for ureide-transporting woody perennials, but its physiological role is poorly understood. We evaluated the concentrations of ureides, amino acids, and organic acids in photosynthetic foliar tissue from Ni-sufficient (Ni-S) versus Ni-deficient (Ni-D) pecan (Carya illinoinensis [Wangenh.] K. Koch). Foliage of Ni-D pecan seedlings exhibited metabolic disruption of nitrogen metabolism via ureide catabolism, amino acid metabolism, and ornithine cycle intermediates. Disruption of ureide catabolism in Ni-D foliage resulted in accumulation of xanthine, allantoic acid, ureidoglycolate, and citrulline, but total ureides, urea concentration, and urease activity were reduced. Disruption of amino acid metabolism in Ni-D foliage resulted in accumulation of glycine, valine, isoleucine, tyrosine, tryptophan, arginine, and total free amino acids, and lower concentrations of histidine and glutamic acid. Ni deficiency also disrupted the citric acid cycle, the second stage of respiration, where Ni-D foliage contained very low levels of citrate compared to Ni-S foliage. Disruption of carbon metabolism was also via accumulation of lactic and oxalic acids. The results indicate that mouse-ear, a key morphological symptom, is likely linked to the toxic accumulation of oxalic and lactic acids in the rapidly growing tips and margins of leaflets. Our results support the role of Ni as an essential plant nutrient element. The magnitude of metabolic disruption exhibited in Ni-D pecan is evidence of the existence of unidentified physiological roles for Ni in pecan.

Dual function catalysts. Dehydrogenation and asymmetric intramolecular Diels-Alder cycloaddition of N-hydroxy formate esters and hydroxamic acids: evidence for a ruthenium-acylnitroso intermediate.

PubMed

Chow, Chun P; Shea, Kenneth J

2005-03-23

The chiral ruthenium salen complex, 13b, functions as an efficient catalyst for the sequential oxidation and asymmetric Diels-Alder cycloaddition of hydroxamic acids and N-hydroxy formate esters. This result provides evidence for the formation of a ruthenium-nitroso formate (acyl nitroso) intermediate. The Diels-Alder precursors are prepared from simple building blocks, and the cycloadducts, bridged oxazinolactams, can serve as useful intermediates in organic synthesis.

Evidence for an Ionic Intermediate in the Transformation of Fatty Acid Hydroperoxide by a Catalase-related Allene Oxide Synthase from the Cyanobacterium Acaryochloris marina*

PubMed Central

Gao, Benlian; Boeglin, William E.; Zheng, Yuxiang; Schneider, Claus; Brash, Alan R.

2009-01-01

Allene oxides are reactive epoxides biosynthesized from fatty acid hydroperoxides by specialized cytochrome P450s or by catalase-related hemoproteins. Here we cloned, expressed, and characterized a gene encoding a lipoxygenase-catalase/peroxidase fusion protein from Acaryochloris marina. We identified novel allene oxide synthase (AOS) activity and a by-product that provides evidence of the reaction mechanism. The fatty acids 18.4ω3 and 18.3ω3 are oxygenated to the 12R-hydroperoxide by the lipoxygenase domain and converted to the corresponding 12R,13-epoxy allene oxide by the catalase-related domain. Linoleic acid is oxygenated to its 9R-hydroperoxide and then, surprisingly, converted ∼70% to an epoxyalcohol identified spectroscopically and by chemical synthesis as 9R,10S-epoxy-13S-hydroxyoctadeca-11E-enoic acid and only ∼30% to the 9R,10-epoxy allene oxide. Experiments using oxygen-18-labeled 9R-hydroperoxide substrate and enzyme incubations conducted in H218O indicated that ∼72% of the oxygen in the epoxyalcohol 13S-hydroxyl arises from water, a finding that points to an ionic intermediate (epoxy allylic carbocation) during catalysis. AOS and epoxyalcohol synthase activities are mechanistically related, with a reacting intermediate undergoing a net hydrogen abstraction or hydroxylation, respectively. The existence of epoxy allylic carbocations in fatty acid transformations is widely implicated although for AOS reactions, without direct experimental support. Our findings place together in strong association the reactions of allene oxide synthesis and an ionic reaction intermediate in the AOS-catalyzed transformation. PMID:19531485

Bridge-bonded formate: active intermediate or spectator species in formic acid oxidation on a Pt film electrode?

PubMed

Chen, Y-X; Heinen, M; Jusys, Z; Behm, R J

2006-12-05

We present and discuss the results of an in situ IR study on the mechanism and kinetics of formic acid oxidation on a Pt film/Si electrode, performed in an attenuated total reflection (ATR) flow cell configuration under controlled mass transport conditions, which specifically aimed at elucidating the role of the adsorbed bridge-bonded formates in this reaction. Potentiodynamic measurements show a complex interplay between formation and desorption/oxidation of COad and formate species and the total Faradaic current. The notably faster increase of the Faradaic current compared to the coverage of bridge-bonded formate in transient measurements at constant potential, but with different formic acid concentrations, reveals that adsorbed formate decomposition is not rate-limiting in the dominant reaction pathway. If being reactive intermediate at all, the contribution of formate adsorption/decomposition to the reaction current decreases with increasing formic acid concentration, accounting for at most 15% for 0.2 M DCOOH at 0.7 VRHE. The rapid build-up/removal of the formate adlayer and its similarity with acetate or (bi-)sulfate adsorption/desorption indicate that the formate adlayer coverage is dominated by a fast dynamic adsorption-desorption equilibrium with the electrolyte, and that formate desorption is much faster than its decomposition. The results corroborate the proposal of a triple pathway reaction mechanism including an indirect pathway, a formate pathway, and a dominant direct pathway, as presented previously (Chen, Y. X.; et al. Angew. Chem. Int. Ed. 2006, 45, 981), in which adsorbed formates act as a site-blocking spectator in the dominant pathway rather than as an active intermediate.

Biological upgrading of volatile fatty acids, key intermediates for the valorization of biowaste through dark anaerobic fermentation.

PubMed

Singhania, Reeta Rani; Patel, Anil Kumar; Christophe, Gwendoline; Fontanille, Pierre; Larroche, Christian

2013-10-01

VFAs can be obtained from lignocellulosic agro-industrial wastes, sludge, and various biodegradable organic wastes as key intermediates through dark fermentation processes and synthesized through chemical route also. They are building blocks of several organic compounds viz. alcohol, aldehyde, ketones, esters and olefins. These can serve as alternate carbon source for microbial biolipid, biohydrogen, microbial fuel cells productions, methanisation, and for denitrification. Organic wastes are the substrate for VFA platform that is of zero or even negative cost, giving VFA as intermediate product but their separation from the fermentation broth is still a challenge; however, several separation technologies have been developed, membrane separation being the most suitable one. These aspects will be reviewed and results obtained during anaerobic treatment of slaughterhouse wastes with further utilisation of volatile fatty acids for yeast cultivation have been discussed. Copyright © 2012 Elsevier Ltd. All rights reserved.

Effect of alternative pathway therapy on branched chain amino acid metabolism in urea cycle disorder patients.

PubMed

Scaglia, Fernando; Carter, Susan; O'Brien, William E; Lee, Brendan

2004-04-01

Urea cycle disorders (UCDs) are a group of inborn errors of hepatic metabolism caused by the loss of enzymatic activities that mediate the transfer of nitrogen from ammonia to urea. These disorders often result in life-threatening hyperammonemia and hyperglutaminemia. A combination of sodium phenylbutyrate and sodium phenylacetate/benzoate is used in the clinical management of children with urea cycle defects as a glutamine trap, diverting nitrogen from urea synthesis to alternatives routes of excretion. We have observed that patients treated with these compounds have selective branched chain amino acid (BCAA) deficiency despite adequate dietary protein intake. However, the direct effect of alternative therapy on the steady state levels of plasma branched chain amino acids has not been well characterized. We have measured steady state plasma branched chain and other essential non-branched chain amino acids in control subjects, untreated ornithine transcarbamylase deficiency females and treated null activity urea cycle disorder patients in the fed steady state during the course of stable isotope studies. Steady-state leucine levels were noted to be significantly lower in treated urea cycle disorder patients when compared to either untreated ornithine transcarbamylase deficiency females or control subjects (P<0.0001). This effect was reproduced in control subjects who had depressed leucine levels when treated with sodium phenylacetate/benzoate (P<0.0001). Our studies suggest that this therapeutic modality has a substantial impact on the metabolism of branched chain amino acids in urea cycle disorder patients. These findings suggest that better titration of protein restriction could be achieved with branched chain amino acid supplementation in patients with UCDs who are on alternative route therapy.

Biodegradation of ichlorodiphenyltrichloroe-thane: Intermediates in dichlorodiphenylacetic acid metabolism by Aerobacter aerogenes

USGS Publications Warehouse

1967-01-01

The final product of dichlorodiphenyltrichloroethane (DDT) degradation by vertebrates is commonly considered to be dichlorodiphenylacetic acid, DDA (J. E. Peterson and W. H. Robison, Toxicol. Appl. Pharmacol. 6:321, 1964). Recently, certain organisms (A. S. Perry, S. Miller, and A. J. Buckner. J. Agr. Food Chem. 11:457, 1963; J. D. Pinto, M. N. Comien, and M. S. Dunn. J. Biol. Chem. 240:2148, 1965) have been found to degrade further DDA to dichlorobenzophenone (DBP), but the possibility that such degradation was due to microbial action could not be excluded. Significantly, dichlorobenzhydrol (DBH), dichlorophenylmethane (DPM), and dichlorodiphenylethylene (DDE) have been tentatively identified in rats fed DDA (Pinto et al., J. Biol. Chem. 240:2148, 1965). Since DDA as well as DDT is degraded by the ubiquitous microorganism Aerobacter aerogenes (G. Wedemeyer, Appl. Microbiol. 15:569, 1967; J. L. Mendel, and M. S. Walton, Science 151:1527, 1966), it seemed reasonable that the intestinal microflora might be involved in DBP formation, DPM and DBH being intermediates in its pathway from DDA. Since DDA is a (3,y-unsaturated acid, ketone formation via an alkene and an alcohol would be expected (S. G. Waley, Mechanisms of Organic and Enzymatic Reactions, Oxford University Press, London, England 1962).

Results of chopper-controlled discharge life cycling studies on lead acid batteries

NASA Technical Reports Server (NTRS)

Ewashinka, J. G.; Sidik, S. M.

1982-01-01

A group of 108 state of the art nominally 6 volt lead acid batteries were tested in a program of one charge/discharge cycle per day for over two years or to ultimate battery failure. The primary objective was to determine battery cycle life as a function of depth of discharge (25 to 75 percent), chopper frequency (100 to 1000 Hz), duty cycle (25 to 87.5 percent), and average discharge current (20 to 260 A). The secondary objective was to determine the types of battery failure modes, if any, were due to the above parameters. The four parameters above were incorporated in a statistically designed test program.

Examination of key intermediates in the catalytic cycle of aspartate-beta-semialdehyde dehydrogenase from a gram-positive infectious bacteria.

PubMed

Faehnle, Christopher R; Le Coq, Johanne; Liu, Xuying; Viola, Ronald E

2006-10-13

Aspartate-beta-semialdehyde dehydrogenase (ASADH) catalyzes a critical branch point transformation in amino acid bio-synthesis. The products of the aspartate pathway are essential in microorganisms, and this entire pathway is absent in mammals, making this enzyme an attractive target for antibiotic development. The first structure of an ASADH from a Gram-positive bacterium, Streptococcus pneumoniae, has now been determined. The overall structure of the apoenzyme has a similar fold to those of the Gram-negative and archaeal ASADHs but contains some interesting structural variations that can be exploited for inhibitor design. Binding of the coenzyme NADP, as well as a truncated nucleotide analogue, into an alternative conformation from that observed in Gram-negative ASADHs causes an enzyme domain closure that precedes catalysis. The covalent acyl-enzyme intermediate was trapped by soaking the substrate into crystals of the coenzyme complex, and the structure of this elusive intermediate provides detailed insights into the catalytic mechanism.

Stoichiometry of Reducing Equivalents and Splitting of Water in the Citric Acid Cycle.

ERIC Educational Resources Information Center

Madeira, Vitor M. C.

1988-01-01

Presents a solution to the problem of finding the source of extra reducing equivalents, and accomplishing the stoichiometry of glucose oxidation reactions. Discusses the citric acid cycle and glycolysis. (CW)

DIBROMOACETIC ACID-INDUCED ELEVATIONS OF ESTRADIOL IN THE CYCLING AND OVARIECTOMOZED/ESTRADIOL-IMPLANTED FEMALE RAT

EPA Science Inventory

Goldman, JM and Murr, AS. Dibromoacetic Acid-induced Elevations of Estradiol in Both Cycling and Ovariectomized / Estradiol-implanted Female Rats

ABSTRACT
Haloacetic acids are one of the principal classes of disinfection by-products generated by the chlorination of mun...

Prognostic Markers in Core-Binding Factor AML and Improved Survival with Multiple Consolidation Cycles of Intermediate/High-dose Cytarabine.

PubMed

Prabahran, Ashvind; Tacey, Mark; Fleming, Shaun; Wei, Andrew; Tate, Courtney; Marlton, Paula; Wight, Joel; Grigg, Andrew; Tuckfield, Annabel; Szer, Jeff; Ritchie, David; Chee, Lynette

2018-05-02

Core-binding factor acute myeloid leukaemia (CBF AML) defined by t(8;21)(q22;q22) or inv(16)(p13q22)/t(16;16)(p13;q22) has a favourable prognosis, however 30-40% of patients still relapse after chemotherapy. We sought to evaluate risk factors for relapse in a de novo CBF AML cohort. A retrospective review of patients from 4 Australian tertiary centres from 2001-2012, comprising 40 t(8;21) and 30 inv(16) AMLs. Multivariate analysis identified age (p=0.032) and WCC>40 (p=0.025) as significant predictors for inferior OS and relapse respectively. Relapse risk was higher in the inv(16) group vs the t(8;21) group (57% vs 18%, HR 4.31, 95% CI: 1.78-10.42, p=0.001). Induction therapy had no bearing on OS or relapse free survival (RFS) however, consolidation treatment with >3 cycles of intermediate/high dose cytarabine improved OS (p=0.035) and relapse-free survival (RFS) (p=0.063). 5 patients demonstrated post-treatment stable q PCR positivity without relapse. (1)>3 consolidation cycles of intermediate/ high-dose cytarabine improves patient outcomes. (2)Age and inv(16) CBF AML subtype are predictors of inferior OS and RFS respectively. (3)Stable low-level MRD by qPCR does not predict relapse. (4)Similar OS in the inv(16) cohort compared to the t(8;21) cohort, despite a higher relapse rate, confirms salvageability of relapsed disease. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Extending food deprivation reverses the short-term lipolytic response to fasting: role of the triacylglycerol/fatty acid cycle.

PubMed

Weber, Jean-Michel; Reidy, Shannon P

2012-05-01

The effects of short-term food deprivation on lipid metabolism are well documented, but little is known about prolonged fasting. This study monitored the kinetics of glycerol (rate of appearance, R(a) glycerol) and non-esterified fatty acids (R(a) NEFA) in fasting rabbits. Our goals were to determine whether lipolysis is stimulated beyond values seen for short-term fasting, and to characterize the roles of primary (intracellular) and secondary (with transit through the circulation) triacylglycerol/fatty acid cycling (TAG/FA cycling) in regulating fatty acid allocation to oxidation or re-esterification. R(a) glycerol (9.62±0.72 to 15.29±0.96 μmol kg(-1) min(-1)) and R(a) NEFA (18.05±2.55 to 31.25±1.93 μmol kg(-1) min(-1)) were stimulated during the first 2 days of fasting, but returned to baseline after 4 days. An initial increase in TAG/FA cycling was followed by a reduction below baseline after 6 days without food, with primary and secondary cycling contributing to these responses. We conclude that the classic activation of lipolysis caused by short-term fasting is abolished when food deprivation is prolonged. High rates of re-esterification may become impossible to sustain, and TAG/FA cycling could decrease to reduce its cost to 3% of total energy expenditure. Throughout prolonged fasting, fatty acid metabolism gradually shifts towards increased oxidation and reduced re-esterification. Survival is achieved by pressing fuel selection towards the fatty acid dominance of energy metabolism and by slowing substrate cycles to assist metabolic suppression. However, TAG/FA cycling remains active even after prolonged fasting, suggesting that re-esterification is a crucial mechanism that cannot be stopped without harmful consequences.

Intermediate progenitors are increased by lengthening of the cell cycle through calcium signaling and p53 expression in human neural progenitors

PubMed Central

García-García, Elisa; Pino-Barrio, María José; López-Medina, Laura; Martínez-Serrano, Alberto

2012-01-01

During development, neurons can be generated directly from a multipotent progenitor or indirectly through an intermediate progenitor (IP). This last mode of division amplifies the progeny of neurons. The mechanisms governing the generation and behavior of IPs are not well understood. In this work, we demonstrate that the lengthening of the cell cycle enhances the generation of neurons in a human neural progenitor cell system in vitro and also the generation and expansion of IPs. These IPs are insulinoma-associated 1 (Insm1)+/BTG family member 2 (Btg2)−, which suggests an increase in a self-amplifying IP population. Later the cultures express neurogenin 2 (Ngn2) and become neurogenic. The signaling responsible for this cell cycle modulation is investigated. It is found that the release of calcium from the endoplasmic reticulum to the cytosol in response to B cell lymphoma-extra large overexpression or ATP addition lengths the cell cycle and increases the number of IPs and, in turn, the final neuron outcome. Moreover, data suggest that the p53–p21 pathway is responsible for the changes in cell cycle. In agreement with this, increased p53 levels are necessary for a calcium-induced increase in neurons. Our findings contribute to understand how calcium signaling can modulate cell cycle length during neurogenesis. PMID:22323293

Differential regulation of glutamic acid decarboxylase gene expression after extinction of a recent memory vs. intermediate memory.

PubMed

Sangha, Susan; Ilenseer, Jasmin; Sosulina, Ludmila; Lesting, Jörg; Pape, Hans-Christian

2012-04-17

Extinction reduces fear to stimuli that were once associated with an aversive event by no longer coupling the stimulus with the aversive event. Extinction learning is supported by a network comprising the amygdala, hippocampus, and prefrontal cortex. Previous studies implicate a critical role of GABA in extinction learning, specifically the GAD65 isoform of the GABA synthesizing enzyme glutamic acid decarboxylase (GAD). However, a detailed analysis of changes in gene expression of GAD in the subregions comprising the extinction network has not been undertaken. Here, we report changes in gene expression of the GAD65 and GAD67 isoforms of GAD, as measured by relative quantitative real-time RT-PCR, in subregions of the amygdala, hippocampus, and prefrontal cortex 24-26 h after extinction of a recent (1-d) or intermediate (14-d) fear memory. Our results show that extinction of a recent memory induces a down-regulation of Gad65 gene expression in the hippocampus (CA1, dentate gyrus) and an up-regulation of Gad67 gene expression in the infralimbic cortex. Extinguishing an intermediate memory increased Gad65 gene expression in the central amygdala. These results indicate a differential regulation of Gad gene expression after extinction of a recent memory vs. intermediate memory.

Sirt3 promotes the urea cycle and fatty acid oxidation during dietary restriction

PubMed Central

Hallows, William C.; Yu, Wei; Smith, Brian C.; Devries, Mark K.; Ellinger, James J.; Someya, Shinichi; Shortreed, Michael R.; Prolla, Tomas; Markley, John L.; Smith, Lloyd M.; Zhao, Shimin; Guan, Kun-Liang; Denu, John M.

2011-01-01

Summary Emerging evidence suggests that protein acetylation is a broad-ranging regulatory mechanism. Here we utilize acetyl-peptide arrays and metabolomic analyses to identify substrates of mitochondrial deacetylase Sirt3. We identified ornithine transcarbamoylase (OTC) from the urea cycle, and enzymes involved in β-oxidation. Metabolomic analyses of fasted mice lacking Sirt3 (sirt3−/−) revealed alterations in β-oxidation and the urea cycle. Biochemical analysis demonstrated that Sirt3 directly deacetylates OTC and stimulates its activity. Mice under caloric restriction (CR) increased Sirt3 protein levels, leading to deacetylation and stimulation of OTC activity. In contrast, sirt3−/− mice failed to deacetylate OTC in response to CR. Inability to stimulate OTC under CR led to a failure to reduce orotic acid levels, a known outcome of OTC deficiency. Thus, Sirt3 directly regulates OTC activity and promotes the urea cycle during CR, and the results suggest that under low energy input, Sirt3 modulates mitochondria by promoting amino-acid catabolism and β-oxidation. PMID:21255725

Nickel Deficiency Disrupts Metabolism of Ureides, Amino Acids, and Organic Acids of Young Pecan Foliage[OA

PubMed Central

Bai, Cheng; Reilly, Charles C.; Wood, Bruce W.

2006-01-01

The existence of nickel (Ni) deficiency is becoming increasingly apparent in crops, especially for ureide-transporting woody perennials, but its physiological role is poorly understood. We evaluated the concentrations of ureides, amino acids, and organic acids in photosynthetic foliar tissue from Ni-sufficient (Ni-S) versus Ni-deficient (Ni-D) pecan (Carya illinoinensis [Wangenh.] K. Koch). Foliage of Ni-D pecan seedlings exhibited metabolic disruption of nitrogen metabolism via ureide catabolism, amino acid metabolism, and ornithine cycle intermediates. Disruption of ureide catabolism in Ni-D foliage resulted in accumulation of xanthine, allantoic acid, ureidoglycolate, and citrulline, but total ureides, urea concentration, and urease activity were reduced. Disruption of amino acid metabolism in Ni-D foliage resulted in accumulation of glycine, valine, isoleucine, tyrosine, tryptophan, arginine, and total free amino acids, and lower concentrations of histidine and glutamic acid. Ni deficiency also disrupted the citric acid cycle, the second stage of respiration, where Ni-D foliage contained very low levels of citrate compared to Ni-S foliage. Disruption of carbon metabolism was also via accumulation of lactic and oxalic acids. The results indicate that mouse-ear, a key morphological symptom, is likely linked to the toxic accumulation of oxalic and lactic acids in the rapidly growing tips and margins of leaflets. Our results support the role of Ni as an essential plant nutrient element. The magnitude of metabolic disruption exhibited in Ni-D pecan is evidence of the existence of unidentified physiological roles for Ni in pecan. PMID:16415214

Protein vivisection reveals elusive intermediates in folding

PubMed Central

Zheng, Zhongzhou; Sosnick, Tobin R.

2010-01-01

Although most folding intermediates escape detection, their characterization is crucial to the elucidation of folding mechanisms. Here we outline a powerful strategy to populate partially unfolded intermediates: A buried aliphatic residue is substituted with a charged residue (e.g., Leu→Glu−) to destabilize and unfold a specific region of the protein. We apply this strategy to Ubiquitin, reversibly trapping a folding intermediate in which the β5 strand is unfolded. The intermediate refolds to a native-like structure upon charge neutralization under mildly acidic conditions. Characterization of the trapped intermediate using NMR and hydrogen exchange methods identifies a second folding intermediate and reveals the order and free energies of the two major folding events on the native side of the rate-limiting step. This general strategy may be combined with other methods and have broad applications in the study of protein folding and other reactions that require trapping of high energy states. PMID:20144618

Long-chain fatty acid combustion rate is associated with unique metabolite profiles in skeletal muscle mitochondria.

PubMed

Seifert, Erin L; Fiehn, Oliver; Bezaire, Véronic; Bickel, David R; Wohlgemuth, Gert; Adams, Sean H; Harper, Mary-Ellen

2010-03-24

Incomplete or limited long-chain fatty acid (LCFA) combustion in skeletal muscle has been associated with insulin resistance. Signals that are responsive to shifts in LCFA beta-oxidation rate or degree of intramitochondrial catabolism are hypothesized to regulate second messenger systems downstream of the insulin receptor. Recent evidence supports a causal link between mitochondrial LCFA combustion in skeletal muscle and insulin resistance. We have used unbiased metabolite profiling of mouse muscle mitochondria with the aim of identifying candidate metabolites within or effluxed from mitochondria and that are shifted with LCFA combustion rate. Large-scale unbiased metabolomics analysis was performed using GC/TOF-MS on buffer and mitochondrial matrix fractions obtained prior to and after 20 min of palmitate catabolism (n = 7 mice/condition). Three palmitate concentrations (2, 9 and 19 microM; corresponding to low, intermediate and high oxidation rates) and 9 microM palmitate plus tricarboxylic acid (TCA) cycle and electron transport chain inhibitors were each tested and compared to zero palmitate control incubations. Paired comparisons of the 0 and 20 min samples were made by Student's t-test. False discovery rate were estimated and Type I error rates assigned. Major metabolite groups were organic acids, amines and amino acids, free fatty acids and sugar phosphates. Palmitate oxidation was associated with unique profiles of metabolites, a subset of which correlated to palmitate oxidation rate. In particular, palmitate oxidation rate was associated with distinct changes in the levels of TCA cycle intermediates within and effluxed from mitochondria. This proof-of-principle study establishes that large-scale metabolomics methods can be applied to organelle-level models to discover metabolite patterns reflective of LCFA combustion, which may lead to identification of molecules linking muscle fat metabolism and insulin signaling. Our results suggest that future studies

Long-Chain Fatty Acid Combustion Rate Is Associated with Unique Metabolite Profiles in Skeletal Muscle Mitochondria

PubMed Central

Seifert, Erin L.; Fiehn, Oliver; Bezaire, Véronic; Bickel, David R.; Wohlgemuth, Gert; Adams, Sean H.; Harper, Mary-Ellen

2010-01-01

Background/Aim Incomplete or limited long-chain fatty acid (LCFA) combustion in skeletal muscle has been associated with insulin resistance. Signals that are responsive to shifts in LCFA β-oxidation rate or degree of intramitochondrial catabolism are hypothesized to regulate second messenger systems downstream of the insulin receptor. Recent evidence supports a causal link between mitochondrial LCFA combustion in skeletal muscle and insulin resistance. We have used unbiased metabolite profiling of mouse muscle mitochondria with the aim of identifying candidate metabolites within or effluxed from mitochondria and that are shifted with LCFA combustion rate. Methodology/Principal Findings Large-scale unbiased metabolomics analysis was performed using GC/TOF-MS on buffer and mitochondrial matrix fractions obtained prior to and after 20 min of palmitate catabolism (n = 7 mice/condition). Three palmitate concentrations (2, 9 and 19 µM; corresponding to low, intermediate and high oxidation rates) and 9 µM palmitate plus tricarboxylic acid (TCA) cycle and electron transport chain inhibitors were each tested and compared to zero palmitate control incubations. Paired comparisons of the 0 and 20 min samples were made by Student's t-test. False discovery rate were estimated and Type I error rates assigned. Major metabolite groups were organic acids, amines and amino acids, free fatty acids and sugar phosphates. Palmitate oxidation was associated with unique profiles of metabolites, a subset of which correlated to palmitate oxidation rate. In particular, palmitate oxidation rate was associated with distinct changes in the levels of TCA cycle intermediates within and effluxed from mitochondria. Conclusions/Significance This proof-of-principle study establishes that large-scale metabolomics methods can be applied to organelle-level models to discover metabolite patterns reflective of LCFA combustion, which may lead to identification of molecules linking muscle fat

Aerobic Oxidation of Xylose to Xylaric acid in Water over Pt Catalysts.

PubMed

Saha, Basudeb; Sadula, Sunitha

2018-05-02

Energy-efficient catalytic conversion of biomass intermediates to functional chemicals can enable bio-products viable. Herein, we report an efficient and low temperature aerobic oxidation of xylose to xylaric acid, a promising bio-based chemical for the production of glutaric acid, over commercial catalysts in water. Among several heterogeneous catalysts investigated, Pt/C exhibits the best activity. Systematic variation of reaction parameters in the pH range of 2.5 to 10 suggests that the reaction is fast at higher temperatures but high C-C scission of intermediate C5-oxidized products to low carbon carboxylic acids undermines xylaric acid selectivity. The C-C cleavage is also high in basic solution. The oxidation at neutral pH and 60 C achieves the highest xylaric acid yield (64%). O2 pressure and Pt-amount have significant influence on the reactivity. Decarboxylation of short chain carboxylic acids results in formation of CO2, causing some carbon loss; however such decarboxylation is slow in the presence of xylose. The catalyst retained comparable activity, in terms of product selectivity, after five cycles with no sign of Pt leaching. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Cinnamic acid derivatives induce cell cycle arrest in carcinoma cell lines.

PubMed

Sova, Matej; Žižak, Željko; Stanković, Jelena A Antic; Prijatelj, Matevž; Turk, Samo; Juranić, Zorica D; Mlinarič-Raščan, Irena; Gobec, Stanislav

2013-08-01

Cinnamic acid derivatives can be found in plant material, and they possess a remarkable variety of biological effects. In the present study, we have investigated the cytotoxic effects of representative cinnamic acid esters and amides. The cytotoxicity was determined by MTT test on human cervix adenocarcinoma (HeLa), myelogenous leukemia (K562), malignant melanoma (Fem-x), and estrogen-receptor-positive breast cancer (MCF-7) cells, versus peripheral blood mononuclear cells (PBMCs) without or with the addition of the plant lectin phytohemaglutinin (PHA). The compounds tested showed significant cytotoxicity (IC50s between 42 and 166 µM) and furthermore selectivity of these cytotoxic effects on the malignant cell lines versus the PBMCs was also seen, especially when electron-withdrawing groups, such as a cyano group (compound 5), were present on the aromatic rings of the alcohol or amine parts of the cinnamic acid derivatives. The additional study on cell cycle phase distribution indicated that novel cinnamic acid derivatives inhibit cell growth by induction of cell death. Thus, cinnamic acids derivatives represent important lead compounds for further development of antineoplastic agents.

Contribution of the tricarboxylic acid (TCA) cycle and the glyoxylate shunt in Saccharomyces cerevisiae to succinic acid production during dough fermentation.

PubMed

Rezaei, Mohammad N; Aslankoohi, Elham; Verstrepen, Kevin J; Courtin, Christophe M

2015-07-02

Succinic acid produced by yeast during bread dough fermentation can significantly affect the rheological properties of the dough. By introducing mutations in the model S288C yeast strain, we show that the oxidative pathway of the TCA cycle and the glyoxylate shunt contribute significantly to succinic acid production during dough fermentation. More specifically, deletion of ACO1 and double deletion of ACO1 and ICL1 resulted in a 36 and 77% decrease in succinic acid levels in fermented dough, respectively. Similarly, double deletion of IDH1 and IDP1 decreased succinic acid production by 85%, while also affecting the fermentation rate. By contrast, double deletion of SDH1 and SDH2 resulted in a two-fold higher succinic acid accumulation compared to the wild-type. Deletion of fumarate reductase activity (FRD1 and OSM1) in the reductive pathway of the TCA cycle did not affect the fermentation rate and succinic acid production. The changes in the levels of succinic acid produced by mutants Δidh1Δidp1 (low level) and Δsdh1Δsdh2 (high level) in fermented dough only resulted in small pH differences, reflecting the buffering capacity of dough at a pH of around 5.1. Moreover, Rheofermentometer analysis using these mutants revealed no difference in maximum dough height and gas retention capacity with the dough prepared with S288C. The impact of the changed succinic acid profile on the organoleptic or antimicrobial properties of bread remains to be demonstrated. Copyright © 2015 Elsevier B.V. All rights reserved.

C-Myc Induced Compensated Cardiac Hypertrophy Increases Free Fatty Acid Utilization for the Citric Acid Cycle

DOE Office of Scientific and Technical Information (OSTI.GOV)

Olson, Aaron; Ledee, Dolena; Iwamoto, Kate

The protooncogene C-Myc (Myc) regulates cardiac hypertrophy. Myc promotes compensated cardiac function, suggesting that the operative mechanisms differ from those leading to heart failure. Myc regulation of substrate metabolism is a reasonable target, as Myc alters metabolism in other tissues. We hypothesize that Myc-induced shifts in substrate utilization signal and promote compensated hypertrophy. We used cardiac specific Myc-inducible C57/BL6 male mice between 4-6 months old that develop hypertrophy with tamoxifen (tam). Isolated working hearts and 13Carbon (13C )-NMR were used to measure function and fractional contributions (Fc) to the citric acid cycle by using perfusate containing 13C-labeled free fatty acids,more » acetoacetate, lactate, unlabeled glucose and insulin. Studies were performed at pre-hypertrophy (3-days tam, 3dMyc), established hypertrophy (7-days tam, 7dMyc) or vehicle control (cont). Non-transgenic siblings (NTG) received 7-days tam or vehicle to assess drug effect. Hypertrophy was confirmed by echocardiograms and heart weights. Western blots were performed on key metabolic enzymes. Hypertrophy occurred in 7dMyc only. Cardiac function did not differ between groups. Tam alone did not affect substrate contribution in NTG. Substrate utilization was not significantly altered in 3dMyc versus cont. The free fatty acid FC was significantly greater in 7dMyc vs cont with decreased unlabeled Fc, which is predominately exogenous glucose. Free fatty acid flux to the citric acid cycle increased while lactate flux was diminished in 7dMyc compared to cont. Total protein levels of a panel of key metabolic enzymes were unchanged; however total protein O-GlcNAcylation was increased in 7dMyc. Substrate utilization changes did not precede hypertrophy; therefore they are not the primary signal for cardiac growth in this model. Free fatty acid utilization and oxidation increase at established hypertrophy. Understanding the mechanisms whereby this change

13-cis Retinoic acid induces apoptosis and cell cycle arrest in human SEB-1 sebocytes.

PubMed

Nelson, Amanda M; Gilliland, Kathryn L; Cong, Zhaoyuan; Thiboutot, Diane M

2006-10-01

Isotretinoin (13-cis retinoic acid (13-cis RA)) is the most potent inhibitor of sebum production, a key component in the pathophysiology of acne, yet its mechanism of action remains largely unknown. The effects of 13-cis RA, 9-cis retinoic acid (9-cis RA), and all-trans retinoic acid (ATRA) on cell proliferation, apoptosis, and cell cycle proteins were examined in SEB-1 sebocytes and keratinocytes. 13-cis RA causes significant dose-dependent and time-dependent decreases in viable SEB-1 sebocytes. A portion of this decrease can be attributed to cell cycle arrest as evidenced by decreased DNA synthesis, increased p21 protein expression, and decreased cyclin D1. Although not previously demonstrated in sebocytes, we report that 13-cis RA induces apoptosis in SEB-1 sebocytes as shown by increased Annexin V-FITC staining, increased TUNEL staining, and increased cleaved caspase 3 protein. Furthermore, the ability of 13-cis RA to induce apoptosis cannot be recapitulated by 9-cis RA or ATRA, and it is not inhibited by the presence of a retinoid acid receptor (RAR) pan-antagonist AGN 193109. Taken together these data indicate that 13-cis RA causes cell cycle arrest and induces apoptosis in SEB-1 sebocytes by a RAR-independent mechanism, which contributes to its sebosuppressive effect and the resolution of acne.

Observing a late folding intermediate of Ubiquitin at atomic resolution by NMR

PubMed Central

Surana, Parag

2016-01-01

Abstract The study of intermediates in the protein folding pathway provides a wealth of information about the energy landscape. The intermediates also frequently initiate pathogenic fibril formations. While observing the intermediates is difficult due to their transient nature, extreme conditions can partially unfold the proteins and provide a glimpse of the intermediate states. Here, we observe the high resolution structure of a hydrophobic core mutant of Ubiquitin at an extreme acidic pH by nuclear magnetic resonance (NMR) spectroscopy. In the structure, the native secondary and tertiary structure is conserved for a major part of the protein. However, a long loop between the beta strands β3 and β5 is partially unfolded. The altered structure is supported by fluorescence data and the difference in free energies between the native state and the intermediate is reflected in the denaturant induced melting curves. The unfolded region includes amino acids that are critical for interaction with cofactors as well as for assembly of poly‐Ubiquitin chains. The structure at acidic pH resembles a late folding intermediate of Ubiquitin and indicates that upon stabilization of the protein's core, the long loop converges on the core in the final step of the folding process. PMID:27111887

Genetic alterations in Krebs cycle and its impact on cancer pathogenesis.

PubMed

Sajnani, Karishma; Islam, Farhadul; Smith, Robert Anthony; Gopalan, Vinod; Lam, Alfred King-Yin

2017-04-01

Cancer cells exhibit alterations in many cellular processes, including oxygen sensing and energy metabolism. Glycolysis in non-oxygen condition is the main energy production process in cancer rather than mitochondrial respiration as in benign cells. Genetic and epigenetic alterations of Krebs cycle enzymes favour the shift of cancer cells from oxidative phosphorylation to anaerobic glycolysis. Mutations in genes encoding aconitase, isocitrate dehydrogenase, succinate dehydrogenase, fumarate hydratase, and citrate synthase are noted in many cancers. Abnormalities of Krebs cycle enzymes cause ectopic production of Krebs cycle intermediates (oncometabolites) such as 2-hydroxyglutarate, and citrate. These oncometabolites stabilize hypoxia inducible factor 1 (HIF1), nuclear factor like 2 (Nrf2), inhibit p53 and prolyl hydroxylase 3 (PDH3) activities as well as regulate DNA/histone methylation, which in turn activate cell growth signalling. They also stimulate increased glutaminolysis, glycolysis and production of reactive oxygen species (ROS). Additionally, genetic alterations in Krebs cycle enzymes are involved with increased fatty acid β-oxidations and epithelial mesenchymal transition (EMT) induction. These altered phenomena in cancer could in turn promote carcinogenesis by stimulating cell proliferation and survival. Overall, epigenetic and genetic changes of Krebs cycle enzymes lead to the production of oncometabolite intermediates, which are important driving forces of cancer pathogenesis and progression. Understanding and applying the knowledge of these mechanisms opens new therapeutic options for patients with cancer. Copyright © 2017 Elsevier B.V. and Société Française de Biochimie et Biologie Moléculaire (SFBBM). All rights reserved.

Comparative study of toxicological and cell cycle effects of okadaic acid and dinophysistoxin-2 in primary rat hepatocytes.

PubMed

Rubiolo, J A; López-Alonso, H; Vega, F V; Vieytes, M R; Botana, L M

2012-03-10

To determine the relative toxicity and effects on the cell cycle of okadaic acid and dinophysistoxin-2 in primary hepatocyte cultures. Cytotoxicity was determined by the MTT method, caspase-3 activity and lactate dehydrogenase release to the medium. The cell cycle analysis was performed by imaging flow cytometry and the effect of the toxins on cell proliferation was studied by quantitative PCR and confocal microscopy. We show that dinophysistoxin-2 is less toxic than okadaic acid for primary hepatocytes with a similar difference in potency as that observed in vivo in mice after intraperitoneal injection. Both toxins induced apoptosis with caspase-3 increase. They also inhibited the hepatocytes cell cycle in G1 affecting diploid cells and diploid bi-nucleated cells. In proliferating hepatocytes exposed to the toxins, a decrease of p53 gene expression as well as a lower protein level was detected. Studies of the tubulin cytoskeleton in toxin treated cells, showed nuclear localization of this molecule and a granulated tubulin pattern in the cytoplasm. The results presented in this work show that the difference in toxicity between dinophysistoxin-2 and okadaic acid in cultured primary hepatocytes is the same as that observed in vivo after intraperitoneal injection. Okadaic acid and dinophysistoxin-2 arrest the cell cycle of hepatocytes at G1 even in diploid bi-nucleated cells. p53 and tubulin could be involved in the cell cycle inhibitory effect. Copyright © 2012 Elsevier Inc. All rights reserved.

Highly durable organic electrode for sodium-ion batteries via a stabilized α-C radical intermediate

NASA Astrophysics Data System (ADS)

Wu, Shaofei; Wang, Wenxi; Li, Minchan; Cao, Lujie; Lyu, Fucong; Yang, Mingyang; Wang, Zhenyu; Shi, Yang; Nan, Bo; Yu, Sicen; Sun, Zhifang; Liu, Yao; Lu, Zhouguang

2016-11-01

It is a challenge to prepare organic electrodes for sodium-ion batteries with long cycle life and high capacity. The highly reactive radical intermediates generated during the sodiation/desodiation process could be a critical issue because of undesired side reactions. Here we present durable electrodes with a stabilized α-C radical intermediate. Through the resonance effect as well as steric effects, the excessive reactivity of the unpaired electron is successfully suppressed, thus developing an electrode with stable cycling for over 2,000 cycles with 96.8% capacity retention. In addition, the α-radical demonstrates reversible transformation between three states: C=C α-C.radical and α-C- anion. Such transformation provides additional Na+ storage equal to more than 0.83 Na+ insertion per α-C radical for the electrodes. The strategy of intermediate radical stabilization could be enlightening in the design of organic electrodes with enhanced cycling life and energy storage capability.

p57KIP2 regulates radial glia and intermediate precursor cell cycle dynamics and lower layer neurogenesis in developing cerebral cortex

PubMed Central

Mairet-Coello, Georges; Tury, Anna; Van Buskirk, Elise; Robinson, Kelsey; Genestine, Matthieu; DiCicco-Bloom, Emanuel

2012-01-01

During cerebral cortex development, precise control of precursor cell cycle length and cell cycle exit is required for balanced precursor pool expansion and layer-specific neurogenesis. Here, we defined the roles of cyclin-dependent kinase inhibitor (CKI) p57KIP2, an important regulator of G1 phase, using deletion mutant mice. Mutant mice displayed macroencephaly associated with cortical hyperplasia during late embryogenesis and postnatal development. Embryonically, proliferation of radial glial cells (RGC) and intermediate precursors (IPC) was increased, expanding both populations, with greater effect on IPCs. Furthermore, cell cycle re-entry was increased during early corticogenesis, whereas cell cycle exit was augmented at middle stage. Consequently, neurogenesis was reduced early, whereas it was enhanced during later development. In agreement, the timetable of early neurogenesis, indicated by birthdating analysis, was delayed. Cell cycle dynamics analyses in mutants indicated that p57KIP2 regulates cell cycle length in both RGCs and IPCs. By contrast, related CKI p27KIP1 controlled IPC proliferation exclusively. Furthermore, p57KIP2 deficiency markedly increased RGC and IPC divisions at E14.5, whereas p27KIP1 increased IPC proliferation at E16.5. Consequently, loss of p57KIP2 increased primarily layer 5-6 neuron production, whereas loss of p27KIP1 increased neurons specifically in layers 2-5. In conclusion, our observations suggest that p57KIP2 and p27KIP1 control neuronal output for distinct cortical layers by regulating different stages of precursor proliferation, and support a model in which IPCs contribute to both lower and upper layer neuron generation. PMID:22223678

Arachidonic acid induces macrophage cell cycle arrest through the JNK signaling pathway.

PubMed

Shen, Ziying; Ma, Yunqing; Ji, Zhonghao; Hao, Yang; Yan, Xuan; Zhong, Yuan; Tang, Xiaochun; Ren, Wenzhi

2018-02-09

Arachidonic acid (AA) has potent pro-apoptotic effects on cancer cells at a low concentration and on macrophages at a very high concentration. However, the effects of AA on the macrophage cell cycle and related signaling pathways have not been fully investigated. Herein we aim to observe the effect of AA on macrophages cell cycle. AA exposure reduced the viability and number of macrophages in a dose- and time-dependent manner. The reduction in RAW264.7 cell viability was not caused by apoptosis, as indicated by caspase-3 and activated caspase-3 detection. Further research illustrated that AA exposure induced RAW264.7 cell cycle arrested at S phase, and some cell cycle-regulated proteins were altered accordingly. Moreover, JNK signaling was stimulated by AA, and the stimulation was partially reversed by a JNK signaling inhibitor in accordance with cell cycle-related factors. In addition, nuclear and total Foxo1/3a and phosphorylated Foxo1/3a were elevated by AA in a dose- and time-dependent manner, and this elevation was suppressed by the JNK signaling inhibitor. Our study demonstrated that AA inhibits macrophage viability by inducing S phase cell cycle arrest. The JNK signaling pathway and the downstream FoxO transcription factors are involved in AA-induced RAW264.7 cell cycle arrest.

Metabolomics approach to assessing plasma 13- and 9-hydroxy-octadecadienoic acid and linoleic acid metabolite responses to 75-km cycling.

PubMed

Nieman, David C; Shanely, R Andrew; Luo, Beibei; Meaney, Mary Pat; Dew, Dustin A; Pappan, Kirk L

2014-07-01

Bioactive oxidized linoleic acid metabolites (OXLAMs) include 13- and 9-hydroxy-octadecadienoic acid (13-HODE + 9-HODE) and have been linked to oxidative stress, inflammation, and numerous pathological and physiological states. The purpose of this study was to measure changes in plasma 13-HODE + 9-HODE following a 75-km cycling bout and identify potential linkages to linoleate metabolism and established biomarkers of oxidative stress (F2-isoprostanes) and inflammation (cytokines) using a metabolomics approach. Trained male cyclists (N = 19, age 38.0 ± 1.6 yr, wattsmax 304 ± 10.5) engaged in a 75-km cycling time trial on their own bicycles using electromagnetically braked cycling ergometers (2.71 ± 0.07 h). Blood samples were collected preexercise, immediately post-, 1.5 h post-, and 21 h postexercise, and analyzed for plasma cytokines (IL-6, IL-8, IL-10, tumor necrosis factor-α, monocyte chemoattractant protein-1, granulocyte colony-stimulating factor), F2-isoprostanes, and shifts in metabolites using global metabolomics procedures with gas chromatography mass spectrometry (GC-MS) and liquid chromatography mass spectrometry (LC-MS). 13-HODE + 9-HODE increased 3.1-fold and 1.7-fold immediately post- and 1.5 h postexercise (both P < 0.001) and returned to preexercise levels by 21-h postexercise. Post-75-km cycling plasma levels of 13-HODE + 9-HODE were not significantly correlated with increases in plasma cytokines but were positively correlated with postexercise F2-isoprostanes (r = 0.75, P < 0.001), linoleate (r = 0.54, P = 0.016), arachidate (r = 0.77, P < 0.001), 12,13-dihydroxy-9Z-octadecenoate (12,13-DiHOME) (r = 0.60, P = 0.006), dihomo-linolenate (r = 0.57, P = 0.011), and adrenate (r = 0.56, P = 0.013). These findings indicate that prolonged and intensive exercise caused a transient, 3.1-fold increase in the stable linoleic acid oxidation product 13-HODE + 9-HODE and was related to increases in F2-isoprostanes, linoleate, and fatty acids in the linoleate

Alternative reactions at the interface of glycolysis and citric acid cycle in Saccharomyces cerevisiae

PubMed Central

van Rossum, Harmen M.; Kozak, Barbara U.; Niemeijer, Matthijs S.; Duine, Hendrik J.; Luttik, Marijke A. H.; Boer, Viktor M.; Kötter, Peter; Daran, Jean-Marc G.; van Maris, Antonius J. A.

2016-01-01

Pyruvate and acetyl-coenzyme A, located at the interface between glycolysis and TCA cycle, are important intermediates in yeast metabolism and key precursors for industrially relevant products. Rational engineering of their supply requires knowledge of compensatory reactions that replace predominant pathways when these are inactivated. This study investigates effects of individual and combined mutations that inactivate the mitochondrial pyruvate-dehydrogenase (PDH) complex, extramitochondrial citrate synthase (Cit2) and mitochondrial CoA-transferase (Ach1) in Saccharomyces cerevisiae. Additionally, strains with a constitutively expressed carnitine shuttle were constructed and analyzed. A predominant role of the PDH complex in linking glycolysis and TCA cycle in glucose-grown batch cultures could be functionally replaced by the combined activity of the cytosolic PDH bypass and Cit2. Strongly impaired growth and a high incidence of respiratory deficiency in pda1Δ ach1Δ strains showed that synthesis of intramitochondrial acetyl-CoA as a metabolic precursor requires activity of either the PDH complex or Ach1. Constitutive overexpression of AGP2, HNM1, YAT2, YAT1, CRC1 and CAT2 enabled the carnitine shuttle to efficiently link glycolysis and TCA cycle in l-carnitine-supplemented, glucose-grown batch cultures. Strains in which all known reactions at the glycolysis-TCA cycle interface were inactivated still grew slowly on glucose, indicating additional flexibility at this key metabolic junction. PMID:26895788

Duty cycle dependent chemical structure and wettability of RF pulsed plasma copolymers of acrylic acid and octafluorocyclobutane

NASA Astrophysics Data System (ADS)

Muzammil, I.; Li, Y. P.; Li, X. Y.; Lei, M. K.

2018-04-01

Octafluorocyclobutane and acrylic acid (C4F8-co-AA) plasma copolymer coatings are deposited using a pulsed wave (PW) radio frequency (RF) plasma on low density polyethylene (LDPE). The influence of duty cycle in pulsed process with the monomer feed rate on the surface chemistry and wettability of C4F8-co-AA plasma polymer coatings is studied. The concentration of the carboxylic acid (hydrophilic) groups increase, and that of fluorocarbon (hydrophobic) groups decrease by lowering the duty cycle. The combined effect of surface chemistry and surface morphology of the RF pulsed plasma copolymer coatings causes tunable surface wettability and surface adhesion. The gradual emergence of hydrophilic contents leads to surface heterogeneity by lowering duty cycle causing an increased surface adhesion in hydrophobic coatings. The C4F8-co-AA plasma polymer coatings on the nanotextured surfaces are tuned from repulsive superhydrophobicity to adhesive superhydrophobicity, and further to superhydrophilicity by adjusting the duty cycles with the monomer feed rates.

Activities of Tricarboxylic Acid Cycle Enzymes, Glyoxylate Cycle Enzymes, and Fructose Diphosphatase in Bakers' Yeast During Adaptation to Acetate Oxidation

PubMed Central

Gosling, J. P.; Duggan, P. F.

1971-01-01

Bakers' yeast oxidizes acetate at a high rate only after an adaptation period during which the capacity of the glyoxylate cycle is found to increase. There was apparently no necessity for the activity of acetyl-coenzyme A synthetase, the capacity of the tricarboxylic acid cycle, or the concentrations of the cytochromes to increase for this adaptation to occur. Elevation of fructose 1,6 diphosphatase occurred only when acetate oxidation was nearly maximal. Cycloheximide almost completely inhibited adaptation as well as increases in the activities of isocitrate lyase and aconitate hydratase, the only enzymes assayed. p-Fluorophenylalanine was partially effective and chloramphenicol did not inhibit at all. The presence of ammonium, which considerably delayed adaptation of the yeast to acetate oxidation, inhibited the increases in the activities of the glyoxylate cycle enzymes to different degrees, demonstrating noncoordinate control of these enzymes. Under the various conditions, the only enzyme activity increase consistently related to the rising oxygen uptake rate was that of isocitrate lyase which apparently limited the activity of the cycle. PMID:5557595

Ecotypic variability in the metabolic response of seeds to diurnal hydration-dehydration cycles and its relationship to seed vigor.

PubMed

Bai, Bing; Sikron, Noga; Gendler, Tanya; Kazachkova, Yana; Barak, Simon; Grafi, Gideon; Khozin-Goldberg, Inna; Fait, Aaron

2012-01-01

Seeds in the seed bank experience diurnal cycles of imbibition followed by complete dehydration. These conditions pose a challenge to the regulation of germination. The effect of recurring hydration-dehydration (Hy-Dh) cycles were tested on seeds from four Arabidopsis thaliana accessions [Col-0, Cvi, C24 and Ler]. Diurnal Hy-Dh cycles had a detrimental effect on the germination rate and on the final percentage of germination in Col-0, Cvi and C24 ecotypes, but not in the Ler ecotype, which showed improved vigor following the treatments. Membrane permeability measured by ion conductivity was generally increased following each Hy-Dh cycle and was correlated with changes in the redox status represented by the GSSG/GSH (oxidized/reduced glutathione) ratio. Among the ecotypes, Col-0 seeds displayed the highest membrane permeability, whilst Ler was characterized by the greatest increase in electrical conductivity following Hy-Dh cycles. Following Dh 2 and Dh 3, the respiratory activity of Ler seeds significantly increased, in contrast to the other ecotypes, indicative of a dramatic shift in metabolism. These differences were associated with accession-specific content and patterns of change of (i) cell wall-related laminaribiose and mannose; (ii) fatty acid composition, specifically of the unsaturated oleic acid and α-linoleic acid; and (iii) asparagine, ornithine and the related polyamine putrescine. Furthermore, in the Ler ecotype the content of the tricarboxylic acid (TCA) cycle intermediates fumarate, succinate and malate increased in response to dehydration, in contrast to a decrease in the other three ecotypes. These findings provide a link between seed respiration, energy metabolism, fatty acid β-oxidation, nitrogen mobilization and membrane permeability and the improved germination of Ler seeds following Hy-Dh cycles.

Activation and Repression of Epstein-Barr Virus and Kaposi's Sarcoma-Associated Herpesvirus Lytic Cycles by Short- and Medium-Chain Fatty Acids

PubMed Central

Gorres, Kelly L.; Daigle, Derek; Mohanram, Sudharshan

2014-01-01

ABSTRACT The lytic cycles of Epstein-Barr virus (EBV) and Kaposi's sarcoma-associated herpesvirus (KSHV) are induced in cell culture by sodium butyrate (NaB), a short-chain fatty acid (SCFA) histone deacetylase (HDAC) inhibitor. Valproic acid (VPA), another SCFA and an HDAC inhibitor, induces the lytic cycle of KSHV but blocks EBV lytic reactivation. To explore the hypothesis that structural differences between NaB and VPA account for their functional effects on the two related viruses, we investigated the capacity of 16 structurally related short- and medium-chain fatty acids to promote or prevent lytic cycle reactivation. SCFAs differentially affected EBV and KSHV reactivation. KSHV was reactivated by all SCFAs that are HDAC inhibitors, including phenylbutyrate. However, several fatty acid HDAC inhibitors, such as isobutyrate and phenylbutyrate, did not reactivate EBV. Reactivation of KSHV lytic transcripts could not be blocked completely by any fatty acid tested. In contrast, several medium-chain fatty acids inhibited lytic activation of EBV. Fatty acids that blocked EBV reactivation were more lipophilic than those that activated EBV. VPA blocked activation of the BZLF1 promoter by NaB but did not block the transcriptional function of ZEBRA. VPA also blocked activation of the DNA damage response that accompanies EBV lytic cycle activation. Properties of SCFAs in addition to their effects on chromatin are likely to explain activation or repression of EBV. We concluded that fatty acids stimulate the two related human gammaherpesviruses to enter the lytic cycle through different pathways. IMPORTANCE Lytic reactivation of EBV and KSHV is needed for persistence of these viruses and plays a role in carcinogenesis. Our direct comparison highlights the mechanistic differences in lytic reactivation between related human oncogenic gammaherpesviruses. Our findings have therapeutic implications, as fatty acids are found in the diet and produced by the human microbiota

Aromatic aldehyde-catalyzed gas-phase decarboxylation of amino acid anion via imine intermediate: An experimental and theoretical study

NASA Astrophysics Data System (ADS)

Xiang, Zhang

2013-10-01

It is generally appreciated that carbonyl compound can promote the decarboxylation of the amino acid. In this paper, we have performed the experimental and theoretical investigation into the gas-phase decarboxylation of the amino acid anion catalyzed by the aromatic aldehyde via the imine intermediate on the basis of the tandem mass spectrometry (MS/MS) technique and density functional theory (DFT) calculation. The results show that the aromatic aldehyde can achieve a remarkable catalytic effect. Moreover, the catalytic mechanism varies according to the type of amino acid: (i) The decarboxylation of α-amino acid anion is determined by the direct dissociation of the Csbnd C bond adjacent to the carboxylate, for the resulting carbanion can be well stabilized by the conjugation between α-carbon, Cdbnd N bond and benzene ring. (ii) The decarboxylation of non-α-amino acid anion proceeds via a SN2-like transition state, in which the dissociation of the Csbnd C bond adjacent to the carboxylate and attacking of the resulting carbanion to the Cdbnd N bond or benzene ring take place at the same time. Specifically, for β-alanine, the resulting carbanion preferentially attacks the benzene ring leading to the benzene anion, because attacking the Cdbnd N bond in the decarboxylation can produce the unstable three or four-membered ring anion. For the other non-α-amino acid anion, the Cdbnd N bond preferentially participates in the decarboxylation, which leads to the pediocratic nitrogen anion.

Respiration accumulates Calvin cycle intermediates for the rapid start of photosynthesis in Synechocystis sp. PCC 6803.

PubMed

Shimakawa, Ginga; Hasunuma, Tomohisa; Kondo, Akihiko; Matsuda, Mami; Makino, Amane; Miyake, Chikahiro

2014-01-01

We tested the hypothesis that inducing photosynthesis in cyanobacteria requires respiration. A mutant deficient in glycogen phosphorylase (∆GlgP) was prepared in Synechocystis sp. PCC 6803 to suppress respiration. The accumulated glycogen in ΔGlgP was 250-450% of that accumulated in wild type (WT). The rate of dark respiration in ΔGlgP was 25% of that in WT. In the dark, P700(+) reduction was suppressed in ΔGlgP, and the rate corresponded to that in (2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone)-treated WT, supporting a lower respiration rate in ∆GlgP. Photosynthetic O2-evolution rate reached a steady-state value much slower in ∆GlgP than in WT. This retardation was solved by addition of d-glucose. Furthermore, we found that the contents of Calvin cycle intermediates in ∆GlgP were lower than those in WT under dark conditions. These observations indicated that respiration provided the carbon source for regeneration of ribulose 1,5-bisphosphate in order to drive the rapid start of photosynthesis.

The Tricarboxylic Acid Cycle, an Ancient Metabolic Network with a Novel Twist

PubMed Central

Mailloux, Ryan J.; Bériault, Robin; Lemire, Joseph; Singh, Ranji; Chénier, Daniel R.; Hamel, Robert D.; Appanna, Vasu D.

2007-01-01

The tricarboxylic acid (TCA) cycle is an essential metabolic network in all oxidative organisms and provides precursors for anabolic processes and reducing factors (NADH and FADH2) that drive the generation of energy. Here, we show that this metabolic network is also an integral part of the oxidative defence machinery in living organisms and α-ketoglutarate (KG) is a key participant in the detoxification of reactive oxygen species (ROS). Its utilization as an anti-oxidant can effectively diminish ROS and curtail the formation of NADH, a situation that further impedes the release of ROS via oxidative phosphorylation. Thus, the increased production of KG mediated by NADP-dependent isocitrate dehydrogenase (NADP-ICDH) and its decreased utilization via the TCA cycle confer a unique strategy to modulate the cellular redox environment. Activities of α-ketoglutarate dehydrogenase (KGDH), NAD-dependent isocitrate dehydrogenase (NAD-ICDH), and succinate dehydrogenase (SDH) were sharply diminished in the cellular systems exposed to conditions conducive to oxidative stress. These findings uncover an intricate link between TCA cycle and ROS homeostasis and may help explain the ineffective TCA cycle that characterizes various pathological conditions and ageing. PMID:17668068

Why do larval helminths avoid the gut of intermediate hosts?

PubMed

Parker, G A; Ball, M A; Chubb, J C

2009-10-07

In complex life cycles, larval helminths typically migrate from the gut to exploit the tissues of their intermediate hosts. Yet the definitive host's gut is overwhelmingly the most favoured site for adult helminths to release eggs. Vertebrate nematodes with one-host cycles commonly migrate to a site in the host away from the gut before returning to the gut for reproduction; those with complex cycles occupy sites exclusively in the intermediate host's tissues or body spaces, and may or may not show tissue migration before (typically) returning to the gut in the definitive host. We develop models to explain the patterns of exploitation of different host sites, and in particular why larval helminths avoid the intermediate host's gut, and adult helminths favour it. Our models include the survival costs of migration between sites, and maximise fitness (=expected lifetime number of eggs produced by a given helminth propagule) in seeking the optimal strategy (host gut versus host tissue exploitation) under different growth, mortality, transmission and reproductive rates in the gut and tissues (i.e. sites away from the gut). We consider the relative merits of the gut and tissues, and conclude that (i) growth rates are likely to be higher in the tissues, (ii) mortality rates possibly higher in the gut (despite the immunological inertness of the gut lumen), and (iii) that there are very high benefits to egg release in the gut. The models show that these growth and mortality relativities would account for the common life history pattern of avoidance of the intermediate host's gut because the tissues offer a higher growth rate/mortality rate ratio (discounted by the costs of migration), and make a number of testable predictions. Though nematode larvae in paratenic hosts usually migrate to the tissues, unlike larvae in intermediates, they sometimes remain in the gut, which is predicted since in paratenics mortality rate and migration costs alone determine the site to be

Biodegradation of Lignin Monomers Vanillic, p-Coumaric, and Syringic Acid by the Bacterial Strain, Sphingobacterium sp. HY-H.

PubMed

Wang, Jinxing; Liang, Jidong; Gao, Sha

2018-05-10

Many bacterial strains have been demonstrated to biodegrade lignin for contaminant removal or resource regeneration. The goal of this study was to investigate the biodegradation amount and associated pathways of three lignin monomers, vanillic, p-coumaric, and syringic acid by strain Sphingobacterium sp. HY-H. Vanillic, p-coumaric, and syringic acid degradation with strain HY-H was estimated as 88.71, 76.67, and 72.78%, respectively, after 96 h. Correspondingly, the same three monomers were associated with a COD removal efficiency of 87.30, 55.17, and 67.23%, and a TOC removal efficiency of 82.14, 61.03, and 43.86%. The results of GC-MS, HPLC, FTIR, and enzyme activities show that guaiacol and o-dihydroxybenzene are key intermediate metabolites of the vanillic acid and syringic acid degradation. p-Hydroxybenzoic acid is an important intermediate metabolite for p-coumaric and syringic acid degradation. LiP and MnP play an important role in the degradation of lignin monomers and their intermediate metabolites. One possible pathway is that strain HY-H degrades lignin monomers into guaiacol (through decarboxylic and demethoxy reaction) or p-hydroxybenzoic acid (through side-chain oxidation); then guaiacol demethylates to o-dihydroxybenzene. The p-hydroxybenzoic acid and o-dihydroxybenzene are futher through ring cleavage reaction to form small molecule acids (butyric, valproic, oxalic acid, and propionic acid) and alcohols (ethanol and ethanediol), then these acids and alcohols are finally decomposed into CO 2 and H 2 O through the tricarboxylic acid cycle. If properly optimized and controlled, the strain HY-H may play a role in breaking down lignin-related compounds for biofuel and chemical production.

Acetaminophen Toxicity and 5-Oxoproline (Pyroglutamic Acid): A Tale of Two Cycles, One an ATP-Depleting Futile Cycle and the Other a Useful Cycle

PubMed Central

2014-01-01

Summary The acquired form of 5-oxoproline (pyroglutamic acid) metabolic acidosis was first described in 1989 and its relationship to chronic acetaminophen ingestion was proposed the next year. Since then, this cause of chronic anion gap metabolic acidosis has been increasingly recognized. Many cases go unrecognized because an assay for 5-oxoproline is not widely available. Most cases occur in malnourished, chronically ill women with a history of chronic acetaminophen ingestion. Acetaminophen levels are very rarely in the toxic range; rather, they are usually therapeutic or low. The disorder generally resolves with cessation of acetaminophen and administration of intravenous fluids. Methionine or N-acetyl cysteine may accelerate resolution and methionine is protective in a rodent model. The disorder has been attributed to glutathione depletion and activation of a key enzyme in the γ-glutamyl cycle. However, the specific metabolic derangements that cause the 5-oxoproline accumulation remain unclear. An ATP-depleting futile 5-oxoproline cycle can explain the accumulation of 5-oxoproline after chronic acetaminophen ingestion. This cycle is activated by the depletion of both glutathione and cysteine. This explanation contributes to our understanding of acetaminophen-induced 5-oxoproline metabolic acidosis and the beneficial role of N-acetyl cysteine therapy. The ATP-depleting futile 5-oxoproline cycle may also play a role in the energy depletions that occur in other acetaminophen-related toxic syndromes. PMID:24235282

Acetaminophen toxicity and 5-oxoproline (pyroglutamic acid): a tale of two cycles, one an ATP-depleting futile cycle and the other a useful cycle.

PubMed

Emmett, Michael

2014-01-01

The acquired form of 5-oxoproline (pyroglutamic acid) metabolic acidosis was first described in 1989 and its relationship to chronic acetaminophen ingestion was proposed the next year. Since then, this cause of chronic anion gap metabolic acidosis has been increasingly recognized. Many cases go unrecognized because an assay for 5-oxoproline is not widely available. Most cases occur in malnourished, chronically ill women with a history of chronic acetaminophen ingestion. Acetaminophen levels are very rarely in the toxic range; rather, they are usually therapeutic or low. The disorder generally resolves with cessation of acetaminophen and administration of intravenous fluids. Methionine or N-acetyl cysteine may accelerate resolution and methionine is protective in a rodent model. The disorder has been attributed to glutathione depletion and activation of a key enzyme in the γ-glutamyl cycle. However, the specific metabolic derangements that cause the 5-oxoproline accumulation remain unclear. An ATP-depleting futile 5-oxoproline cycle can explain the accumulation of 5-oxoproline after chronic acetaminophen ingestion. This cycle is activated by the depletion of both glutathione and cysteine. This explanation contributes to our understanding of acetaminophen-induced 5-oxoproline metabolic acidosis and the beneficial role of N-acetyl cysteine therapy. The ATP-depleting futile 5-oxoproline cycle may also play a role in the energy depletions that occur in other acetaminophen-related toxic syndromes.

Catalytic amino acid production from biomass-derived intermediates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deng, Weiping; Wang, Yunzhu; Zhang, Sui

Amino acids are the building blocks for protein biosynthesis and find use in myriad industrial applications including in food for humans, in animal feed, and as precursors for bio-based plastics, among others. However, the development of efficient chemical methods to convert abundant and renewable feedstocks into amino acids has been largely unsuccessful to date. To that end, here we report a heterogeneous catalyst that directly transforms lignocellulosic biomass-derived a-hydroxyl acids into a-amino acids, including alanine, leucine, valine, aspartic acid, and phenylalanine in high yields. The reaction follows a dehydrogenation-reductive amination pathway, with dehydrogenation as the rate-determining step. Ruthenium nanoparticles supportedmore » on carbon nanotubes (Ru/CNT) exhibit exceptional efficiency compared with catalysts based on other metals, due to the unique, reversible enhancement effect of NH 3 on Ru in dehydrogenation. Based on the catalytic system, a two-step chemical process was designed to convert glucose into alanine in 43% yield, comparable with the well-established microbial cultivation process, and therefore, the present strategy enables a route for the production of amino acids from renewable feedstocks. Moreover, a conceptual process design employing membrane distillation to facilitate product purification is proposed and validated. Overall, this study offers a rapid and potentially more efficient chemical method to produce amino acids from woody biomass components.« less

Catalytic amino acid production from biomass-derived intermediates

PubMed Central

Deng, Weiping; Zhang, Sui; Gupta, Krishna M.; Hülsey, Max J.; Asakura, Hiroyuki; Liu, Lingmei; Han, Yu; Karp, Eric M.; Jiang, Jianwen; Tanaka, Tsunehiro; Wang, Ye

2018-01-01

Amino acids are the building blocks for protein biosynthesis and find use in myriad industrial applications including in food for humans, in animal feed, and as precursors for bio-based plastics, among others. However, the development of efficient chemical methods to convert abundant and renewable feedstocks into amino acids has been largely unsuccessful to date. To that end, here we report a heterogeneous catalyst that directly transforms lignocellulosic biomass-derived α-hydroxyl acids into α-amino acids, including alanine, leucine, valine, aspartic acid, and phenylalanine in high yields. The reaction follows a dehydrogenation-reductive amination pathway, with dehydrogenation as the rate-determining step. Ruthenium nanoparticles supported on carbon nanotubes (Ru/CNT) exhibit exceptional efficiency compared with catalysts based on other metals, due to the unique, reversible enhancement effect of NH3 on Ru in dehydrogenation. Based on the catalytic system, a two-step chemical process was designed to convert glucose into alanine in 43% yield, comparable with the well-established microbial cultivation process, and therefore, the present strategy enables a route for the production of amino acids from renewable feedstocks. Moreover, a conceptual process design employing membrane distillation to facilitate product purification is proposed and validated. Overall, this study offers a rapid and potentially more efficient chemical method to produce amino acids from woody biomass components. PMID:29712826

Catalytic amino acid production from biomass-derived intermediates.

PubMed

Deng, Weiping; Wang, Yunzhu; Zhang, Sui; Gupta, Krishna M; Hülsey, Max J; Asakura, Hiroyuki; Liu, Lingmei; Han, Yu; Karp, Eric M; Beckham, Gregg T; Dyson, Paul J; Jiang, Jianwen; Tanaka, Tsunehiro; Wang, Ye; Yan, Ning

2018-05-15

Amino acids are the building blocks for protein biosynthesis and find use in myriad industrial applications including in food for humans, in animal feed, and as precursors for bio-based plastics, among others. However, the development of efficient chemical methods to convert abundant and renewable feedstocks into amino acids has been largely unsuccessful to date. To that end, here we report a heterogeneous catalyst that directly transforms lignocellulosic biomass-derived α-hydroxyl acids into α-amino acids, including alanine, leucine, valine, aspartic acid, and phenylalanine in high yields. The reaction follows a dehydrogenation-reductive amination pathway, with dehydrogenation as the rate-determining step. Ruthenium nanoparticles supported on carbon nanotubes (Ru/CNT) exhibit exceptional efficiency compared with catalysts based on other metals, due to the unique, reversible enhancement effect of NH 3 on Ru in dehydrogenation. Based on the catalytic system, a two-step chemical process was designed to convert glucose into alanine in 43% yield, comparable with the well-established microbial cultivation process, and therefore, the present strategy enables a route for the production of amino acids from renewable feedstocks. Moreover, a conceptual process design employing membrane distillation to facilitate product purification is proposed and validated. Overall, this study offers a rapid and potentially more efficient chemical method to produce amino acids from woody biomass components. Copyright © 2018 the Author(s). Published by PNAS.

Catalytic amino acid production from biomass-derived intermediates

DOE PAGES

Deng, Weiping; Wang, Yunzhu; Zhang, Sui; ...

2018-04-30

Amino acids are the building blocks for protein biosynthesis and find use in myriad industrial applications including in food for humans, in animal feed, and as precursors for bio-based plastics, among others. However, the development of efficient chemical methods to convert abundant and renewable feedstocks into amino acids has been largely unsuccessful to date. To that end, here we report a heterogeneous catalyst that directly transforms lignocellulosic biomass-derived a-hydroxyl acids into a-amino acids, including alanine, leucine, valine, aspartic acid, and phenylalanine in high yields. The reaction follows a dehydrogenation-reductive amination pathway, with dehydrogenation as the rate-determining step. Ruthenium nanoparticles supportedmore » on carbon nanotubes (Ru/CNT) exhibit exceptional efficiency compared with catalysts based on other metals, due to the unique, reversible enhancement effect of NH 3 on Ru in dehydrogenation. Based on the catalytic system, a two-step chemical process was designed to convert glucose into alanine in 43% yield, comparable with the well-established microbial cultivation process, and therefore, the present strategy enables a route for the production of amino acids from renewable feedstocks. Moreover, a conceptual process design employing membrane distillation to facilitate product purification is proposed and validated. Overall, this study offers a rapid and potentially more efficient chemical method to produce amino acids from woody biomass components.« less

Comparison of the production, quality, and in vitro maturation capacity of oocytes from untreated cycling and intermediate phase equine serum gonadotropin-treated fat-tailed dunnarts (Sminthopsis crassicaudata).

PubMed

Czarny, N A; Garnham, J I; Harris, M S; Rodger, J C

2009-07-01

This study describes ovarian changes during the natural and stimulated reproductive cycle of breeding (< or =12 month) and retired (>12 month) fat-tailed dunnarts, Sminthopsis crassicaudata. Increased urinary cornified epithelial cells and the influx of leukocytes defined day 0, at which time the naturally cycling females had already ovulated; at day 16 females had no antral follicles, but by day 20 antral follicles had begun to develop. There was no difference between naturally cycling breeding and retired females. Females were stimulated with 1 IU equine serum gonadotropin (eSG) during the intermediate phase on day 16 and killed 3, 4, or 5 days later. Stimulation resulted in a significant increase in the number of growing antral follicles but retired females demonstrated a reduced response. Upon collection from breeding females 4 days following eSG stimulation, 100% of oocytes were at the first polar body (PB1) stage, those collected from retired females were immature upon collection but within 48 h 98.2+/-1.9% were cultured to the PB1 stage. The rate of ovulation was high in breeding females 5 days following stimulation but retired females were less reliable, and in both groups all oocytes were degraded. This is the first study to describe a reliable technique, involving ovarian stimulation during the intermediate phase and segregation of age groups, allowing the collection of a large number of healthy PB1 stage oocytes from S. crassicaudata. This is important for the development of further assisted reproductive techniques for this species and threatened dasyurids.

Advanced intermediate temperature sodium-nickel chloride batteries with ultra-high energy density

DOE PAGES

Li, Guosheng; Lu, Xiaochuan; Kim, Jin Yong; ...

2016-02-11

Here we demonstrate for the first time that planar Na-NiCl 2 batteries can be operated at an intermediate temperature of 190°C with ultra-high energy density. A specific energy density of 350 Wh/kg, which is 3 times higher than that of conventional tubular Na-NiCl 2 batteries operated at 280°C, was obtained for planar Na-NiCl 2 batteries operated at 190°C over a long-term cell test (1000 cycles). The high energy density and superior cycle stability are attributed to the slower particle growth of the cathode materials (NaCl and Ni) at 190°C. The results reported in this work demonstrate that planar Na-NiCl 2more » batteries operated at an intermediate temperature could greatly benefit this traditional energy storage technology by improving battery energy density, cycle life and reducing material costs.« less

Domino-Fluorination-Protodefluorination Enables Decarboxylative Cross-Coupling of α-Oxocarboxylic Acids with Styrene via Photoredox Catalysis.

PubMed

Zhang, Muliang; Xi, Junwei; Ruzi, Rehanguli; Li, Nan; Wu, Zhongkai; Li, Weipeng; Zhu, Chengjian

2017-09-15

Domino-fluorination-protodefluorination decarboxylative cross-coupling of α-keto acids with styrene has been developed via photoredox catalysis. The critical part of this strategy is the formation of the carbon-fluorine (C-F) bond by the capture of a carbon-centered radical intermediate, which will overcome side reactions during the styrene radical functionalization process. Experimental studies have provided evidence indicating a domino-fluorination-protodefluorination pathway with α-keto acid initiating the photoredox cycle. The present catalytic protocol also affords a novel approach for the construction of α,β-unsaturated ketones under mild conditions.

Keto-acids in Carbonaceous Meteorites

NASA Technical Reports Server (NTRS)

Cooper, G.; Chang, P. M.; Dugas, A.; Byrd, A.; Chang, P. M.; Washington, N.

2005-01-01

The Murchison and Murray meteorites are the best-characterized carbonaceous meteorites with respect to organic chemistry and are generally used as references for organic compounds in extraterrestrial material. Among the classes of organic compounds found in these meteorites are amino acids, carboxylic acids, hydroxy acids, purines, and pyrimidines. Such compounds, important in contemporary biochemistry, are thought to have been delivered to the early Earth in asteroids and comets and may have played a role in early life and/or the origin of life. Absent among (today's) critically important biological compounds reported in carbonaceous meteorites are keto acids, i.e., pyruvic acid, acetoacetic acid, and higher homologs. These compounds are key intermediates in such critical processes as glycolysis and the citric acid cycle. In this study several individual meteoritic keto acids were identified by gas chromatography-mass spectrometry (GC-MS) (see figure below). All compounds were identified as their trimethylsilyl (TMS), isopropyl ester (ISP), and tert-butyldimethylsilyl (tBDMS) derivatives. In general, the compounds follow the abiotic synthesis pattern of other known meteorite classes of organic compounds [1,2]: a general decrease in abundance with increasing carbon number within a class of compounds and many, if not all, possible isomers present at a given carbon number. The majority of the shown compounds was positively identified by comparison of their mass spectra to commercially available standards or synthesized standards.

Intermediate temperature proton conductors for PEM fuel cells based on phosphonic acid as protogenic group: a progress report.

PubMed

Steininger, H; Schuster, M; Kreuer, K D; Kaltbeitzel, A; Bingöl, B; Meyer, W H; Schauff, S; Brunklaus, G; Maier, J; Spiess, H W

2007-04-21

The melting behaviour and transport properties of straight chain alkanes mono- and difunctionalized with phosphonic acid groups have been investigated as a function of their length. The increase of melting temperature and decrease of proton conductivity with increasing chain length is suggested to be the consequence of an increasing ordering of the alkane segments which constrains the free aggregation of the phosphonic acid groups. However, the proton mobility is reduced to a greater extent than the proton diffusion coefficient indicating an increasing cooperativity of proton transport with increasing length of the alkane segment. The results clearly indicate that the "spacer concept", which had been proven successful in the optimization of the proton conductivity of heterocycle based systems, fails in the case of phosphonic acid functionalized polymers. Instead, a very high concentration of phosphonic acid functional groups forming "bulky" hydrogen bonded aggregates is suggested to be essential for obtaining very high proton conductivity. Aggregation is also suggested to reduce condensation reactions generally observed in phosphonic acid containing systems. On the basis of this understanding, the proton conductivities of poly(vinyl phosphonic acid) and poly(meta-phenylene phosphonic acid) are discussed. Though both polymers exhibit a substantial concentration of phosphonic acid groups, aggregation seems to be constrained to such an extent that intrinsic proton conductivity is limited to values below sigma = 10(-3) S cm(-1) at T = 150 degrees C. The results suggest that different immobilization concepts have to be developed in order to minimize the conductivity reduction compared to the very high intrinsic proton conductivity of neat phosphonic acid under quasi dry conditions. In the presence of high water activities, however, (as usually present in PEM fuel cells) the very high ion exchange capacities (IEC) possible for phosphonic acid functionalized ionomers (IEC

Prerequisite Change and Its Effect on Intermediate Accounting Performance

ERIC Educational Resources Information Center

Huang, Jiunn; O'Shaughnessy, John; Wagner, Robin

2005-01-01

As of Fall 1996, San Francisco State University changed its introductory financial accounting course to focus on a "user's" perspective, de-emphasizing the accounting cycle. Anticipating that these changes could impair subsequent performance, the Department of Accounting instituted a new prerequisite for intermediate accounting: Students would…

The life-extending gene Indy encodes an exchanger for Krebs-cycle intermediates.

PubMed

Knauf, Felix; Mohebbi, Nilufar; Teichert, Carsten; Herold, Diana; Rogina, Blanka; Helfand, Stephen; Gollasch, Maik; Luft, Friedrich C; Aronson, Peter S

2006-07-01

A longevity gene called Indy (for 'I'm not dead yet'), with similarity to mammalian genes encoding sodium-dicarboxylate cotransporters, was identified in Drosophila melanogaster. Functional studies in Xenopus oocytes showed that INDY mediates the flux of dicarboxylates and citrate across the plasma membrane, but the specific transport mechanism mediated by INDY was not identified. To test whether INDY functions as an anion exchanger, we examined whether substrate efflux is stimulated by transportable substrates added to the external medium. Efflux of [14C]citrate from INDY-expressing oocytes was greatly accelerated by the addition of succinate to the external medium, indicating citrate-succinate exchange. The succinate-stimulated [14C]citrate efflux was sensitive to inhibition by DIDS (4,4'-di-isothiocyano-2,2'-disulphonic stilbene), as demonstrated previously for INDY-mediated succinate uptake. INDY-mediated efflux of [14C]citrate was also stimulated by external citrate and oxaloacetate, indicating citrate-citrate and citrate-oxaloacetate exchange. Similarly, efflux of [14C]succinate from INDY-expressing oocytes was stimulated by external citrate, alpha-oxoglutarate and fumarate, indicating succinate-citrate, succinate-alpha-oxoglutarate and succinate-fumarate exchange respectively. Conversely, when INDY-expressing Xenopus oocytes were loaded with succinate and citrate, [14C]succinate uptake was markedly stimulated, confirming succinate-succinate and succinate-citrate exchange. Exchange of internal anion for external citrate was markedly pH(o)-dependent, consistent with the concept that citrate is co-transported with a proton. Anion exchange was sodium-independent. We conclude that INDY functions as an exchanger of dicarboxylate and tricarboxylate Krebs-cycle intermediates. The effect of decreasing INDY activity, as in the long-lived Indy mutants, may be to alter energy metabolism in a manner that favours lifespan extension.

Stereoselective synthesis of conformationally constrained omega-amino acid analogues from pyroglutamic acid.

PubMed

Bentz, Emilie L; Goswami, Rajesh; Moloney, Mark G; Westaway, Susan M

2005-08-07

Bicyclic lactams derived from pyroglutamic acid provide a useful scaffold for synthesis of conformationally restricted analogues of lysine, ornithine and glutamine, as well as an Ala-Ala dipeptide analogue. Amino alcohol and carboxylic acid derivatives are accessible from a common intermediate. In this strategy, the bicyclic lactam system not only controls, but also facilitates the determination of the stereochemistry of the synthetic intermediates.

An economically and environmentally acceptable synthesis of chiral drug intermediate L-pipecolic acid from biomass-derived lysine via artificially engineered microbes.

PubMed

Cheng, Jie; Huang, Yuding; Mi, Le; Chen, Wujiu; Wang, Dan; Wang, Qinhong

2018-05-10

Deficiency in petroleum resources and increasing environmental concerns have pushed a bio-based economy to be built, employing a highly reproducible, metal contaminant free, sustainable and green biomanufacturing method. Here, a chiral drug intermediate L-pipecolic acid has been synthesized from biomass-derived lysine. This artificial bioconversion system involves the coexpression of four functional genes, which encode L-lysine α-oxidase from Scomber japonicus, glucose dehydrogenase from Bacillus subtilis, Δ 1 -piperideine-2-carboxylase reductase from Pseudomonas putida, and lysine permease from Escherichia coli. Besides, a lysine degradation enzyme has been knocked out to strengthen the process in this microbe. The overexpression of LysP improved the L-pipecolic acid titer about 1.6-folds compared to the control. This engineered microbial factory showed the highest L-pipecolic acid production of 46.7 g/L reported to date and a higher productivity of 2.41 g/L h and a yield of 0.89 g/g. This biotechnological L-pipecolic acid production is a simple, economic, and green technology to replace the presently used chemical synthesis.

Cardiovascular Risk and Serum Hyaluronic Acid: A Preliminary Study in a Healthy Population of Low/Intermediate Risk.

PubMed

Papanastasopoulou, Chrysanthi; Papastamataki, Maria; Karampatsis, Petros; Anagnostopoulou, Eleni; Papassotiriou, Ioannis; Sitaras, Nikolaos

2017-01-01

Hyaluronic acid (HA) has been found to be an important trigger of atherosclerosis. In this study, we investigate the possible association of serum HA with cardiovascular disease risk in a population of low/intermediate risk for cardiovascular events. We enrolled 200 subjects with low/intermediate risk for developing cardiovascular disease. High specific C-reactive protein (hsCRP) was used as an indicator of preclinical atherosclerosis. The Framingham score was used to calculate the cardiovascular risk. Participants with dyslipidemia had significantly higher levels of serum HA than those without dyslipidemia (t-test, P = 0.05), higher levels of hsCRP (Kruskal-Wallis test, P = 0.04), and higher cardiovascular risk according to the Framingham score (Kruskal-Wallis test, P = 0.05). Serum HA concentration correlated significantly with the Framingham score for risk for coronary heart disease over the next 10 years (Spearman r = 0.152, P = 0.02). Diabetic volunteers had significantly higher HA than those without diabetes (t-test, P = 0.02). Participants with metabolic syndrome had higher serum HA levels and higher hsCRP (Kruskal-Wallis test, P = 0.01) compared to volunteers without metabolic syndrome (t-test, P = 0.03). Serum HA should be explored as an early marker of atheromatosis and cardiovascular risk. © 2016 Wiley Periodicals, Inc.

Correlation between root respiration and the levels of biomass and glycyrrhizic acid in Glycyrrhiza uralensis

PubMed Central

Liu, Wenlan; Sun, Zhirong; Qu, Jixu; Yang, Chunning; Zhang, Xiaomin; Wei, Xinxin

2017-01-01

The aim of the present study was to investigate the correlation between root respiration and the levels of biomass and glycyrrhizic acid in Glycyrrhiza uralensis. Root respiration was determined using a biological oxygen analyzer. Respiration-related enzymes including glucose-6-phosphate dehydrogenase plus 6-phosphogluconate dehydrogenase, phosphohexose isomerase and succinate dehydrogenase, and respiratory pathways were evaluated. Biomass was determined by a drying-weighing method. In addition, the percentage of glycyrrhizic acid was detected using high-performance liquid chromatography. The association between root respiration and the levels of biomass and glycyrrhizic acid was investigated. The glycolysis pathway (EMP), tricarboxylic acid cycle (TCA) and pentose phosphate (PPP) pathway acted concurrently in the roots of G. uralensis. Grey correlation analysis showed that TCA had the strongest correlation (correlation coefficient, 0.8003) with biomass. Starch and acetyl coenzyme A had the closest association with above-ground biomass, while soluble sugar correlated less strongly with above-ground biomass. Grey correlation analysis between biochemical pathways and the intermediates showed that pyruvic acid had the strongest correlation with EMP, while acetyl coenzyme A correlated most strongly with TCA. Among the intermediates and pathways, pyruvic acid and EMP exhibited the greatest correlation with glycyrrhizic acid, while acetyl coenzyme A and TCA correlated with glycyrrhizic acid less closely. The results of this study may aid the cultivation of G. uralensis. However, these results require verification in further studies. PMID:28962162

Correlation between root respiration and the levels of biomass and glycyrrhizic acid in Glycyrrhiza uralensis.

PubMed

Liu, Wenlan; Sun, Zhirong; Qu, Jixu; Yang, Chunning; Zhang, Xiaomin; Wei, Xinxin

2017-09-01

The aim of the present study was to investigate the correlation between root respiration and the levels of biomass and glycyrrhizic acid in Glycyrrhiza uralensis . Root respiration was determined using a biological oxygen analyzer. Respiration-related enzymes including glucose-6-phosphate dehydrogenase plus 6-phosphogluconate dehydrogenase, phosphohexose isomerase and succinate dehydrogenase, and respiratory pathways were evaluated. Biomass was determined by a drying-weighing method. In addition, the percentage of glycyrrhizic acid was detected using high-performance liquid chromatography. The association between root respiration and the levels of biomass and glycyrrhizic acid was investigated. The glycolysis pathway (EMP), tricarboxylic acid cycle (TCA) and pentose phosphate (PPP) pathway acted concurrently in the roots of G. uralensis . Grey correlation analysis showed that TCA had the strongest correlation (correlation coefficient, 0.8003) with biomass. Starch and acetyl coenzyme A had the closest association with above-ground biomass, while soluble sugar correlated less strongly with above-ground biomass. Grey correlation analysis between biochemical pathways and the intermediates showed that pyruvic acid had the strongest correlation with EMP, while acetyl coenzyme A correlated most strongly with TCA. Among the intermediates and pathways, pyruvic acid and EMP exhibited the greatest correlation with glycyrrhizic acid, while acetyl coenzyme A and TCA correlated with glycyrrhizic acid less closely. The results of this study may aid the cultivation of G. uralensis . However, these results require verification in further studies.

Residual Tensile Property of Plain Woven Jute Fiber/Poly(Lactic Acid) Green Composites during Thermal Cycling

PubMed Central

Katogi, Hideaki; Takemura, Kenichi; Akiyama, Motoki

2016-01-01

This study investigated the residual tensile properties of plain woven jute fiber reinforced poly(lactic acid) (PLA) during thermal cycling. Temperature ranges of thermal cycling tests were 35–45 °C and 35–55 °C. The maximum number of cycles was 103 cycles. The quasi-static tensile tests of jute fiber, PLA, and composite were conducted after thermal cycling tests. Thermal mechanical analyses of jute fiber and PLA were conducted after thermal cycling tests. Results led to the following conclusions. For temperatures of 35–45 °C, tensile strength of composite at 103 cycles decreased 10% compared to that of composite at 0 cycles. For temperatures of 35–55 °C, tensile strength and Young’s modulus of composite at 103 cycles decreased 15% and 10%, respectively, compared to that of composite at 0 cycles. Tensile properties and the coefficient of linear expansion of PLA and jute fiber remained almost unchanged after thermal cycling tests. From observation of a fracture surface, the length of fiber pull out in the fracture surface of composite at 103 cycles was longer than that of composite at 0 cycles. Therefore, tensile properties of the composite during thermal cycling were decreased, probably because of the decrease of interfacial adhesion between the fiber and resin. PMID:28773694

Effect of tricarboxylic acid cycle regulator on carbon retention and organic component transformation during food waste composting.

PubMed

Lu, Qian; Zhao, Yue; Gao, Xintong; Wu, Junqiu; Zhou, Haixuan; Tang, Pengfei; Wei, Qingbin; Wei, Zimin

2018-05-01

Composting is an environment friendly method to recycling organic waste. However, with the increasing concern about greenhouse gases generated in global atmosphere, it is significant to reduce the emission of carbon dioxide (CO 2 ). This study analyzes tricarboxylic acid (TCA) cycle regulators on the effect of reducing CO 2 emission, and the relationship among organic component (OC) degradation and transformation and microorganism during composting. The results showed that adding adenosine tri-phosphate (ATP) and nicotinamide adenine dinucleotide (NADH) could enhance the transformation of OC and increase the diversity of microorganism community. Malonic acid (MA) as a competitive inhibitor could decrease the emission of CO 2 by inhibiting the TCA cycle. A structural equation model was established to explore effects of different OC and microorganism on humic acid (HA) concentration during composting. Furthermore, added MA provided an environmental benefit in reducing the greenhouse gas emission for manufacture sustainable products. Copyright © 2018 Elsevier Ltd. All rights reserved.

The γ-Glutamyl Cycle in the Choroid Plexus: Its Possible Function in Amino Acid Transport

PubMed Central

Tate, Suresh S.; Ross, Leonard L.; Meister, Alton

1973-01-01

Various anatomic regions of rabbit brain have been examined for activities of the enzymes of the γ-glutamyl cycle. While these enzyme activities were widely distributed in the brain, they are present in much higher concentrations in the choroid plexus than in other parts of the brain. The activities observed are of about the same order of magnitude as found in the kidney. These observations and other considerations suggest that the γ-glutamyl cycle may play a significant role in the transport of amino acids between blood and cerebrospinal fluid. PMID:4145786

Not all boronic acids with a five-membered cycle induce tremor, neuronal damage and decreased dopamine.

PubMed

Pérez-Rodríguez, Maribel; García-Mendoza, Esperanza; Farfán-García, Eunice D; Das, Bhaskar C; Ciprés-Flores, Fabiola J; Trujillo-Ferrara, José G; Tamay-Cach, Feliciano; Soriano-Ursúa, Marvin A

2017-09-01

Several striatal toxins can be used to induce motor disruption. One example is MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine), whose toxicity is accepted as a murine model of parkinsonism. Recently, 3-Thienylboronic acid (3TB) was found to produce motor disruption and biased neuronal damage to basal ganglia in mice. The aim of this study was to examine the toxic effects of four boronic acids with a close structural relationship to 3TB (all having a five-membered cycle), as well as boric acid and 3TB. These boron-containing compounds were compared to MPTP regarding brain access, morphological disruption of the CNS, and behavioral manifestations of such disruption. Data was collected through acute toxicity evaluations, motor behavior tests, necropsies, determination of neuronal survival by immunohistochemistry, Raman spectroscopic analysis of brain tissue, and HPLC measurement of dopamine in substantia nigra and striatum tissue. Each compound showed a distinct profile for motor disruption. For example, motor activity was not disrupted by boric acid, but was decreased by two boronic acids (caused by a sedative effect). 3TB, 2-Thienyl and 2-furanyl boronic acid gave rise to shaking behavior. The various manifestations generated by these compounds can be linked, in part, to different levels of dopamine (measured by HPLC) and degrees of neuronal damage in the basal ganglia and cerebellum. Clearly, motor disruption is not induced by all boronic acids with a five-membered cycle as substituent. Possible explanations are given for the diverse chemico-morphological changes and degrees of disruption of the motor system, considering the role of boron and the structure-toxicity relationship. Copyright © 2017 Elsevier B.V. All rights reserved.

Capturing a flavivirus pre-fusion intermediate.

PubMed

Kaufmann, Bärbel; Chipman, Paul R; Holdaway, Heather A; Johnson, Syd; Fremont, Daved H; Kuhn, Richard J; Diamond, Michael S; Rossmann, Michael G

2009-11-01

During cell entry of flaviviruses, low endosomal pH triggers the rearrangement of the viral surface glycoproteins to a fusion-active state that allows the release of the infectious RNA into the cytoplasm. In this work, West Nile virus was complexed with Fab fragments of the neutralizing mAb E16 and was subsequently exposed to low pH, trapping the virions in a pre-fusion intermediate state. The structure of the complex was studied by cryo-electron microscopy and provides the first structural glimpse of a flavivirus fusion intermediate near physiological conditions. A radial expansion of the outer protein layer of the virion was observed compared to the structure at pH 8. The resulting approximately 60 A-wide shell of low density between lipid bilayer and outer protein layer is likely traversed by the stem region of the E glycoprotein. By using antibody fragments, we have captured a structural intermediate of a virus that likely occurs during cell entry. The trapping of structural transition states by antibody fragments will be applicable for other processes in the flavivirus life cycle and delineating other cellular events that involve conformational rearrangements.

Quantitation of intracellular purine intermediates in different Corynebacteria using electrospray LC-MS/MS.

PubMed

Peifer, Susanne; Schneider, Konstantin; Nürenberg, Gudrun; Volmer, Dietrich A; Heinzle, Elmar

2012-11-01

Intermediates of the purine biosynthesis pathway play key roles in cellular metabolism including nucleic acid synthesis and signal mediation. In addition, they are also of major interest to the biotechnological industry as several intermediates either possess flavor-enhancing characteristics or are applied in medical therapy. In this study, we have developed an analytical method for quantitation of 12 intermediates from the purine biosynthesis pathway including important nucleotides and their corresponding nucleosides and nucleobases. The approach comprised a single-step acidic extraction/quenching procedure, followed by quantitative electrospray LC-MS/MS analysis. The assay was validated in terms of accuracy, precision, reproducibility, and applicability for complex biological matrices. The method was subsequently applied for determination of free intracellular pool sizes of purine biosynthetic pathway intermediates in the two Gram-positive bacteria Corynebacterium glutamicum and Corynebacterium ammoniagenes. Importantly, no ion pair reagents were applied in this approach as usually required for liquid chromatography analysis of large classes of diverse metabolites.

Catalysis of the Oligomerization of O-Phospho-Serine, Aspartic Acid, or Glutamic Acid by Cationic Micelles

NASA Technical Reports Server (NTRS)

Bohler, Christof; Hill, Aubrey R., Jr.; Orgel, Leslie E.

1996-01-01

Treatment of relatively concentrated aqueous solutions of 0-phospho-serine (50 mM), aspartic acid (100 mM) or glutamic acid (100 mM) with carbonyldiimidazole leads to the formation of an activated intermediate that oligomerizes efficiently. When the concentration of amino acid is reduced tenfold, few long oligomers can be detected. Positively-charged cetyltrimethyl ammonium bromide micelles concentrate the negatively-charged activated intermediates of the amino acids at their surfaces and catalyze efficient oligomerization even from dilute solutions.

Catalysis of the Oligomerization of O-Phospho-Serine, Aspartic Acid, or Glutamic Acid by Cationic Micelles

NASA Technical Reports Server (NTRS)

Boehler, Christof; Hill, Aubrey R., Jr.; Orgel, Leslie E.

1996-01-01

Treatment of relatively concentrated aqueous solutions of O-phospho-serine (50 mM), aspartic acid (100 mM) or glutamic acid (100 mM) with carbonyldiimidazole leads to the formation of an activated intermediate that oligomerizes efficiently. When the concentration of amino acid is reduced tenfold, few long oligomers can be detected. Positively-charged cetyltrimethyl ammonium bromide micelles concentrate the negatively-charged activated intermediates of the amino acids at their surfaces and catalyze efficient oligomerization even from dilute solutions.

Acid Rain: A Teaching Focus for the Intermediate Grades.

ERIC Educational Resources Information Center

Adams, Renee B.; Adams, Neil D.

1992-01-01

The study of acid rain provides ample opportunities for active, interdisciplinary learning. This article describes 12 hands-on activities designed to expand students' understanding of acid rain. Background information on acid rain is included. (LB)

Independent of Their Localization in Protein the Hydrophobic Amino Acid Residues Have No Effect on the Molten Globule State of Apomyoglobin and the Disulfide Bond on the Surface of Apomyoglobin Stabilizes This Intermediate State

PubMed Central

Melnik, Tatiana N.; Majorina, Maria A.; Larina, Daria S.; Kashparov, Ivan A.; Samatova, Ekaterina N.; Glukhov, Anatoly S.; Melnik, Bogdan S.

2014-01-01

At present it is unclear which interactions in proteins reveal the presence of intermediate states, their stability and formation rate. In this study, we have investigated the effect of substitutions of hydrophobic amino acid residues in the hydrophobic core of protein and on its surface on a molten globule type intermediate state of apomyoglobin. It has been found that independent of their localization in protein, substitutions of hydrophobic amino acid residues do not affect the stability of the molten globule state of apomyoglobin. It has been shown also that introduction of a disulfide bond on the protein surface can stabilize the molten globule state. However in the case of apomyoglobin, stabilization of the intermediate state leads to relative destabilization of the native state of apomyoglobin. The result obtained allows us not only to conclude which mutations can have an effect on the intermediate state of the molten globule type, but also explains why the introduction of a disulfide bond (which seems to “strengthen” the protein) can result in destabilization of the protein native state of apomyoglobin. PMID:24892675

Independent of their localization in protein the hydrophobic amino acid residues have no effect on the molten globule state of apomyoglobin and the disulfide bond on the surface of apomyoglobin stabilizes this intermediate state.

PubMed

Melnik, Tatiana N; Majorina, Maria A; Larina, Daria S; Kashparov, Ivan A; Samatova, Ekaterina N; Glukhov, Anatoly S; Melnik, Bogdan S

2014-01-01

At present it is unclear which interactions in proteins reveal the presence of intermediate states, their stability and formation rate. In this study, we have investigated the effect of substitutions of hydrophobic amino acid residues in the hydrophobic core of protein and on its surface on a molten globule type intermediate state of apomyoglobin. It has been found that independent of their localization in protein, substitutions of hydrophobic amino acid residues do not affect the stability of the molten globule state of apomyoglobin. It has been shown also that introduction of a disulfide bond on the protein surface can stabilize the molten globule state. However in the case of apomyoglobin, stabilization of the intermediate state leads to relative destabilization of the native state of apomyoglobin. The result obtained allows us not only to conclude which mutations can have an effect on the intermediate state of the molten globule type, but also explains why the introduction of a disulfide bond (which seems to "strengthen" the protein) can result in destabilization of the protein native state of apomyoglobin.

Organic Acids: The Pools of Fixed Carbon Involved in Redox Regulation and Energy Balance in Higher Plants

PubMed Central

Igamberdiev, Abir U.; Eprintsev, Alexander T.

2016-01-01

Organic acids are synthesized in plants as a result of the incomplete oxidation of photosynthetic products and represent the stored pools of fixed carbon accumulated due to different transient times of conversion of carbon compounds in metabolic pathways. When redox level in the cell increases, e.g., in conditions of active photosynthesis, the tricarboxylic acid (TCA) cycle in mitochondria is transformed to a partial cycle supplying citrate for the synthesis of 2-oxoglutarate and glutamate (citrate valve), while malate is accumulated and participates in the redox balance in different cell compartments (via malate valve). This results in malate and citrate frequently being the most accumulated acids in plants. However, the intensity of reactions linked to the conversion of these compounds can cause preferential accumulation of other organic acids, e.g., fumarate or isocitrate, in higher concentrations than malate and citrate. The secondary reactions, associated with the central metabolic pathways, in particularly with the TCA cycle, result in accumulation of other organic acids that are derived from the intermediates of the cycle. They form the additional pools of fixed carbon and stabilize the TCA cycle. Trans-aconitate is formed from citrate or cis-aconitate, accumulation of hydroxycitrate can be linked to metabolism of 2-oxoglutarate, while 4-hydroxy-2-oxoglutarate can be formed from pyruvate and glyoxylate. Glyoxylate, a product of either glycolate oxidase or isocitrate lyase, can be converted to oxalate. Malonate is accumulated at high concentrations in legume plants. Organic acids play a role in plants in providing redox equilibrium, supporting ionic gradients on membranes, and acidification of the extracellular medium. PMID:27471516

Effect on combined cycle efficiency of stack gas temperature constraints to avoid acid corrosion

NASA Technical Reports Server (NTRS)

Nainiger, J. J.

1980-01-01

To avoid condensation of sulfuric acid in the gas turbine exhaust when burning fuel oils contaning sulfur, the exhaust stack temperature and cold-end heat exchanger surfaces must be kept above the condensation temperature. Raising the exhaust stack temperature, however, results in lower combined cycle efficiency compared to that achievable by a combined cycle burning a sulfur-free fuel. The maximum difference in efficiency between the use of sulfur-free and fuels containing 0.8 percent sulfur is found to be less than one percentage point. The effect of using a ceramic thermal barrier coating (TBC) and a fuel containing sulfur is also evaluated. The combined-cycle efficiency gain using a TBC with a fuel containing sulfur compared to a sulfur-free fuel without TBC is 0.6 to 1.0 percentage points with air-cooled gas turbines and 1.6 to 1.8 percentage points with water-cooled gas turbines.

Sodium Phenylbutyrate Decreases Plasma Branched-Chain Amino Acids in Patients with Urea Cycle Disorders

PubMed Central

Burrage, Lindsay C.; Jain, Mahim; Gandolfo, Laura; Lee, Brendan H.; Nagamani, Sandesh CS.

2014-01-01

Sodium phenylbutyrate (NaPBA) is a commonly used medication for the treatment of patients with urea cycle disorders (UCDs). Previous reports involving small numbers of patients with UCDs have shown that NaPBA treatment can result in lower plasma levels of the branched-chain amino acids (BCAA) but this has not been studied systematically. From a large cohort of patients (n=553) with UCDs enrolled in Longitudinal Study of Urea Cycle Disorders, a collaborative multicenter study of the Urea Cycle Disorders Consortium, we evaluated whether treatment with NaPBA leads to a decrease in plasma BCAA levels. Our analysis shows that NaPBA use independently affects the plasma BCAA levels even after accounting for multiple confounding covariates. Moreover, NaPBA use increases the risk for BCAA deficiency. This effect of NaPBA seems specific to plasma BCAA levels, as levels of other essential amino acids are not altered by its use. Our study, in an unselected population of UCD subjects, is the largest to analyze the effects of NaPBA on BCAA metabolism and potentially has significant clinical implications. Our results indicate that plasma BCAA levels should to be monitored in patients treated with NaPBA since patients taking the medication are at increased risk for BCAA deficiency. On a broader scale, they could open avenues to explore NaPBA as a therapy in maple syrup urine disease and other common complex disorders with dysregulation of BCAA metabolism. PMID:25042691

Evolution of the biosynthesis of the branched-chain amino acids

NASA Technical Reports Server (NTRS)

Keefe, Anthony D.; Lazcano, Antonio; Miller, Stanley L.

1995-01-01

The origins of the biosynthetic pathways for the branched-chain amino acids cannot be understood in terms of the backwards development of the present acetolactate pathway because it contains unstable intermediates. We propose that the first biosynthesis of the branched-chain amino acids was by the reductive carboxylation of short branched chain fatty acids giving keto acids which were then transaminated. Similar reaction sequences mediated by nonspecific enzymes would produce serine and threomine from the abundant prebiotic compounds glycolic and lactic acids. The aromatic amino acids may also have first been synthesized in this way, e.g. tryptophan from indole acetic acid. The next step would have been the biosynthesis of leucine from alpha-ketoisovalerc acid. The acetolactate pathway developed subsequently. The first version of the Krebs cycle, which was used for amino acid biosynthesis, would have been assembled by making use fo the reductive carboxylation and leucine biosynthesis enzymes, and completed with the development of a single new enzyme, succinate dehydrogenase. This evolutionary scheme suggests that there may be limitations to inferring the origins of metabolism by a simple back extrapolation of current pathways.

Mechanistic Insights into the Catalytic Oxidation of Carboxylic Acids on Au/TiO 2: Partial Oxidation of Propionic and Butyric Acid to Gold Ketenylidene through Unsaturated Acids

DOE Office of Scientific and Technical Information (OSTI.GOV)

McEntee, Monica; Tang, Wenjie; Neurock, Matthew

Here, the partial oxidation of model C 2–C 4 (acetic, propionic, and butyric) carboxylic acids on Au/TiO 2 catalysts consisting of Au particles ~3 nm in size was investigated using transmission infrared spectroscopy and density functional theory. All three acids readily undergo oxidative dehydrogenation on Au/TiO 2. Propionic and butyric acid dehydrogenate at the C2–C3 positions, whereas acetic acid dehydrogenates at the C1–C2 position. The resulting acrylate and crotonate intermediates are subsequently oxidized to form β-keto acids that decarboxylate. All three acids form a gold ketenylidene intermediate, Au 2C=C=O, along the way to their full oxidation to form CO 2.more » Infrared measurements of Au 2C=C=O formation as a function of time provides a surface spectroscopic probe of the kinetics for the activation and oxidative dehydrogenation of the alkyl groups in the carboxylate intermediates that form.« less

Mechanistic Insights into the Catalytic Oxidation of Carboxylic Acids on Au/TiO 2: Partial Oxidation of Propionic and Butyric Acid to Gold Ketenylidene through Unsaturated Acids

DOE PAGES

McEntee, Monica; Tang, Wenjie; Neurock, Matthew; ...

2014-12-12

Here, the partial oxidation of model C 2–C 4 (acetic, propionic, and butyric) carboxylic acids on Au/TiO 2 catalysts consisting of Au particles ~3 nm in size was investigated using transmission infrared spectroscopy and density functional theory. All three acids readily undergo oxidative dehydrogenation on Au/TiO 2. Propionic and butyric acid dehydrogenate at the C2–C3 positions, whereas acetic acid dehydrogenates at the C1–C2 position. The resulting acrylate and crotonate intermediates are subsequently oxidized to form β-keto acids that decarboxylate. All three acids form a gold ketenylidene intermediate, Au 2C=C=O, along the way to their full oxidation to form CO 2.more » Infrared measurements of Au 2C=C=O formation as a function of time provides a surface spectroscopic probe of the kinetics for the activation and oxidative dehydrogenation of the alkyl groups in the carboxylate intermediates that form.« less

Protein-protein interactions and metabolite channelling in the plant tricarboxylic acid cycle

PubMed Central

Zhang, Youjun; Beard, Katherine F. M.; Swart, Corné; Bergmann, Susan; Krahnert, Ina; Nikoloski, Zoran; Graf, Alexander; Ratcliffe, R. George; Sweetlove, Lee J.; Fernie, Alisdair R.; Obata, Toshihiro

2017-01-01

Protein complexes of sequential metabolic enzymes, often termed metabolons, may permit direct channelling of metabolites between the enzymes, providing increased control over metabolic pathway fluxes. Experimental evidence supporting their existence in vivo remains fragmentary. In the present study, we test binary interactions of the proteins constituting the plant tricarboxylic acid (TCA) cycle. We integrate (semi-)quantitative results from affinity purification-mass spectrometry, split-luciferase and yeast-two-hybrid assays to generate a single reliability score for assessing protein–protein interactions. By this approach, we identify 158 interactions including those between catalytic subunits of sequential enzymes and between subunits of enzymes mediating non-adjacent reactions. We reveal channelling of citrate and fumarate in isolated potato mitochondria by isotope dilution experiments. These results provide evidence for a functional TCA cycle metabolon in plants, which we discuss in the context of contemporary understanding of this pathway in other kingdoms. PMID:28508886

Microstructural Features Controlling the Variability in Low-Cycle Fatigue Properties of Alloy Inconel 718DA at Intermediate Temperature

NASA Astrophysics Data System (ADS)

Texier, Damien; Gómez, Ana Casanova; Pierret, Stéphane; Franchet, Jean-Michel; Pollock, Tresa M.; Villechaise, Patrick; Cormier, Jonathan

2016-03-01

The low-cycle fatigue behavior of two direct-aged versions of the nickel-based superalloy Inconel 718 (IN718DA) was examined in the low-strain amplitude regime at intermediate temperature. High variability in fatigue life was observed, and abnormally short lifetimes were systematically observed to be due to crack initiation at (sub)-surface non-metallic inclusions. However, crack initiation within (sub)-surface non-metallic inclusions did not necessarily lead to short fatigue life. The macro- to micro-mechanical mechanisms of deformation and damage have been examined by means of detailed microstructural characterization, tensile and fatigue mechanical tests, and in situ tensile testing. The initial stages of crack micro-propagation from cracked non-metallic particles into the surrounding metallic matrix occupies a large fraction of the fatigue life and requires extensive local plastic straining in the matrix adjacent to the cracked inclusions. Differences in microstructure that influence local plastic straining, i.e., the δ-phase content and the grain size, coupled with the presence of non-metallic inclusions at the high end of the size distribution contribute strongly to the fatigue life variability.

Metabolic pathways regulated by γ-aminobutyric acid (GABA) contributing to heat tolerance in creeping bentgrass (Agrostis stolonifera)

PubMed Central

Li, Zhou; Yu, Jingjin; Peng, Yan; Huang, Bingru

2016-01-01

γ-Aminobutyric acid is a non-protein amino acid involved in various metabolic processes. The objectives of this study were to examine whether increased GABA could improve heat tolerance in cool-season creeping bentgrass through physiological analysis, and to determine major metabolic pathways regulated by GABA through metabolic profiling. Plants were pretreated with 0.5 mM GABA or water before exposed to non-stressed condition (21/19 °C) or heat stress (35/30 °C) in controlled growth chambers for 35 d. The growth and physiological analysis demonstrated that exogenous GABA application significantly improved heat tolerance of creeping bentgrass. Metabolic profiling found that exogenous application of GABA led to increases in accumulations of amino acids (glutamic acid, aspartic acid, alanine, threonine, serine, and valine), organic acids (aconitic acid, malic acid, succinic acid, oxalic acid, and threonic acid), sugars (sucrose, fructose, glucose, galactose, and maltose), and sugar alcohols (mannitol and myo-inositol). These findings suggest that GABA-induced heat tolerance in creeping bentgrass could involve the enhancement of photosynthesis and ascorbate-glutathione cycle, the maintenance of osmotic adjustment, and the increase in GABA shunt. The increased GABA shunt could be the supply of intermediates to feed the tricarboxylic acid cycle of respiration metabolism during a long-term heat stress, thereby maintaining metabolic homeostasis. PMID:27455877

NHC-catalysed benzoin condensation - is it all down to the Breslow intermediate?

PubMed

Rehbein, Julia; Ruser, Stephanie-M; Phan, Jenny

2015-10-01

The Breslow catalytic cycle describing the benzoin condensation promoted by N-heterocyclic carbenes (NHC) as proposed in the late 1950s has since then been tried by generations of physical organic chemists. Emphasis has been laid on proofing the existence of an enaminol like structure (Breslow intermediate) that explains the observed umpolung of an otherwise electrophilic aldehyde. The present study is not focusing on spectroscopic elucidation of a thiazolydene based Breslow intermediate but rather tries to clarify if this key-intermediate is indeed directly linked with the product side of the overall reaction. The here presented EPR-spectroscopic and computational data provide a fundamentally different view on how the benzoin condensation may proceed: a radical pair could be identified as a second key-intermediate that is derived from the Breslow-intermediate via an SET process. These results highlight the close relationship to the Cannizarro reaction and oxidative transformations of aldehydes under NHC catalysis.

Omega-3 polyunsaturated fatty acid docosahexaenoic acid and its role in exhaustive-exercise-induced changes in female rat ovulatory cycle.

PubMed

Mostafa, Abeer F; Samir, Shereen M; Nagib, R M

2018-04-01

Exhaustive exercises can cause delayed menarche or menstrual cycle irregularities in females. Omega-3 polyunsaturated fatty acids (ω-3 PUFAs) are incorporated into a wide range of benefits in many physiological systems. Our work aimed to assess the role of ω-3 PUFA docosahexaenoic acid (DHA) on the deleterious effects of exhaustive exercise on the female reproductive system in rats. Virgin female rats were randomly divided into 4 groups (12 rats in each): control group, omega-3 group treated with DHA, exhaustive exercise group, and exhaustive exercised rats treated with DHA. Omega-3 was given orally to the rats once daily for 4 estrous cycles. Exhaustive exercises revealed lower levels in progesterone and gonadotropins together with histopathological decrease in number of growing follicles and corpora lutea. Moreover, the exercised rats showed low levels of ovarian antioxidants with high level of caspase-3 and plasma cortisol level that lead to disruption of hypothalamic-pituitary-gonadal axis. ω-3 PUFA DHA has beneficial effects on the number of newly growing follicles in both sedentary and exercised rats with decreasing the level of caspase-3 and increasing the antioxidant activity in ovaries. Exhaustive exercises can cause ovulatory problems in female rats that can be improved by ω-3 supplementation.

Engineering a Polyketide Synthase for In Vitro Production of Adipic Acid

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hagen, Andrew; Poust, Sean; Rond, Tristan de

2015-10-26

Polyketides have enormous structural diversity, yet polyketide synthases (PKSs) have thus far been engineered to produce only drug candidates or derivatives thereof. Thousands of other molecules, including commodity and specialty chemicals, could be synthesized using PKSs if composing hybrid PKSs from well-characterized parts derived from natural PKSs was more efficient. Here, using modern mass spectrometry techniques as an essential part of the design–build–test cycle, we engineered a chimeric PKS to enable production one of the most widely used commodity chemicals, adipic acid. To accomplish this, we introduced heterologous reductive domains from various PKS clusters into the borrelidin PKS’ first extensionmore » module, which we previously showed produces a 3-hydroxy-adipoyl intermediate when coincubated with the loading module and a succinyl-CoA starter unit. Acyl-ACP intermediate analysis revealed an unexpected bottleneck at the dehydration step, which was overcome by introduction of a carboxyacyl-processing dehydratase domain. Appending a thioesterase to the hybrid PKS enabled the production of free adipic acid. Using acyl-intermediate based techniques to “debug” PKSs as described here, it should one day be possible to engineer chimeric PKSs to produce a variety of existing commodity and specialty chemicals, as well as thousands of chemicals that are difficult to produce from petroleum feedstocks using traditional synthetic chemistry.« less

Correlations between FAS elongation cycle genes expression and fatty acid production for improvement of long-chain fatty acids in Escherichia coli.

PubMed

Lee, Sunhee; Jung, Yeontae; Lee, Seunghan; Lee, Jinwon

2013-03-01

Microorganisms have been used for biodiesel (fatty acid methyl ester) production due to their significant environmental and economic benefits. The aim of the present research was to develop new strains of Escherichia coli K-12 MG1655 and to increase the content of long-chain fatty acids by overexpressing essential enzymes that are involved in the fatty acid synthase elongation cycle. In addition, the relationship of β-ketoacyl-acyl carrier protein (ACP) synthase (fabH), β-ketoacyl-ACP reductase (fabG), β-hydroxyacyl-ACP dehydrase (fabZ), and β-enoyl-ACP reductase (fabI) with respect to fatty acid production was investigated. The four enzymes play a unique role in fatty acid biosynthesis and elongation processes. We report the generation of recombinant E. coli strains that produced long-chain fatty acids to amounts twofold over wild type. To verify the results, NAD(+)/NADH ratios and glucose analyses were performed. We also confirmed that FabZ plays an important role in producing unsaturated fatty acids (UFAs) as E. coli SGJS25 (overexpressing the fabZ gene) produced the highest percentage of UFAs (35 % of total long-chain fatty acids), over wild type and other recombinants. Indeed, cis-9-hexadecenoic acid, a major UFA in E. coli SGJS25, was produced at levels 20-fold higher than in wild type after 20 h in culture. The biochemically engineered E. coli presented in this study is expected to be more economical for producing long-chain fatty acids in quality biodiesel production processes.

Industrial production of L-ascorbic Acid (vitamin C) and D-isoascorbic acid.

PubMed

Pappenberger, Günter; Hohmann, Hans-Peter

2014-01-01

L-ascorbic acid (vitamin C) was first isolated in 1928 and subsequently identified as the long-sought antiscorbutic factor. Industrially produced L-ascorbic acid is widely used in the feed, food, and pharmaceutical sector as nutritional supplement and preservative, making use of its antioxidative properties. Until recently, the Reichstein-Grüssner process, designed in 1933, was the main industrial route. Here, D-sorbitol is converted to L-ascorbic acid via 2-keto-L-gulonic acid (2KGA) as key intermediate, using a bio-oxidation with Gluconobacter oxydans and several chemical steps. Today, industrial production processes use additional bio-oxidation steps with Ketogulonicigenium vulgare as biocatalyst to convert D-sorbitol to the intermediate 2KGA without chemical steps. The enzymes involved are characterized by a broad substrate range, but remarkable regiospecificity. This puzzling specificity pattern can be understood from the preferences of these enyzmes for certain of the many isomeric structures which the carbohydrate substrates adopt in aqueous solution. Recently, novel enzymes were identified that generate L-ascorbic acid directly via oxidation of L-sorbosone, an intermediate of the bio-oxidation of D-sorbitol to 2KGA. This opens the possibility for a direct route from D-sorbitol to L-ascorbic acid, obviating the need for chemical rearrangement of 2KGA. Similar concepts for industrial processes apply for the production of D-isoascorbic acid, the C5 epimer of L-ascorbic acid. D-isoascorbic acid has the same conformation at C5 as D-glucose and can be derived more directly than L-ascorbic acid from this common carbohydrate feed stock.

Simulation of climate, ice sheets and CO2 evolution during the last four glacial cycles with an Earth system model of intermediate complexity

NASA Astrophysics Data System (ADS)

Ganopolski, Andrey; Brovkin, Victor

2017-11-01

In spite of significant progress in paleoclimate reconstructions and modelling of different aspects of the past glacial cycles, the mechanisms which transform regional and seasonal variations in solar insolation into long-term and global-scale glacial-interglacial cycles are still not fully understood - in particular, in relation to CO2 variability. Here using the Earth system model of intermediate complexity CLIMBER-2 we performed simulations of the co-evolution of climate, ice sheets, and carbon cycle over the last 400 000 years using the orbital forcing as the only external forcing. The model simulates temporal dynamics of CO2, global ice volume, and other climate system characteristics in good agreement with paleoclimate reconstructions. These results provide strong support for the idea that long and strongly asymmetric glacial cycles of the late Quaternary represent a direct but strongly nonlinear response of the Northern Hemisphere ice sheets to orbital forcing. This response is strongly amplified and globalised by the carbon cycle feedbacks. Using simulations performed with the model in different configurations, we also analyse the role of individual processes and sensitivity to the choice of model parameters. While many features of simulated glacial cycles are rather robust, some details of CO2 evolution, especially during glacial terminations, are sensitive to the choice of model parameters. Specifically, we found two major regimes of CO2 changes during terminations: in the first one, when the recovery of the Atlantic meridional overturning circulation (AMOC) occurs only at the end of the termination, a pronounced overshoot in CO2 concentration occurs at the beginning of the interglacial and CO2 remains almost constant during the interglacial or even declines towards the end, resembling Eemian CO2 dynamics. However, if the recovery of the AMOC occurs in the middle of the glacial termination, CO2 concentration continues to rise during the interglacial

Genetic investigation of tricarboxylic acid metabolism during the Plasmodium falciparum life cycle.

PubMed

Ke, Hangjun; Lewis, Ian A; Morrisey, Joanne M; McLean, Kyle J; Ganesan, Suresh M; Painter, Heather J; Mather, Michael W; Jacobs-Lorena, Marcelo; Llinás, Manuel; Vaidya, Akhil B

2015-04-07

New antimalarial drugs are urgently needed to control drug-resistant forms of the malaria parasite Plasmodium falciparum. Mitochondrial electron transport is the target of both existing and new antimalarials. Herein, we describe 11 genetic knockout (KO) lines that delete six of the eight mitochondrial tricarboxylic acid (TCA) cycle enzymes. Although all TCA KOs grew normally in asexual blood stages, these metabolic deficiencies halted life-cycle progression in later stages. Specifically, aconitase KO parasites arrested as late gametocytes, whereas α-ketoglutarate-dehydrogenase-deficient parasites failed to develop oocysts in the mosquitoes. Mass spectrometry analysis of (13)C-isotope-labeled TCA mutant parasites showed that P. falciparum has significant flexibility in TCA metabolism. This flexibility manifested itself through changes in pathway fluxes and through altered exchange of substrates between cytosolic and mitochondrial pools. Our findings suggest that mitochondrial metabolic plasticity is essential for parasite development. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

The Viability of a Nonenzymatic Reductive Citric Acid Cycle Kinetics and Thermochemistry

NASA Astrophysics Data System (ADS)

Ross, David S.

2007-02-01

The likelihood of a functioning nonenzymatic reductive citric acid cycle, recently proposed as the precursor to biosynthesis on early Earth, is examined on the basis of the kinetics and thermochemistry of the acetate → pyruvate → oxaloacetate → malate sequence. Using data derived from studies of the Pd-catalyzed phosphinate reduction of carbonyl functions it is shown that the rate of conversion of pyruvate to malate with that system would have been much too slow to have played a role in the early chemistry of life, while naturally occurring reduction systems such as the fayalite magnetite quartz and pyrrhotite pyrite magnetite mineral assemblages would have provided even slower conversions. It is also shown that the production of pyruvate from acetate is too highly endoergic to be driven by a naturally occurring energy source such as pyrophosphate. It is thus highly doubtful that the cycle can operate at suitable rates without enzymes, and most unlikely that it could have participated in the chemistry leading to life.

Effects of carbon dioxide on cell growth and propionic acid production from glycerol and glucose by Propionibacterium acidipropionici.

PubMed

Zhang, An; Sun, Jianxin; Wang, Zhongqiang; Yang, Shang-Tian; Zhou, Haiying

2015-01-01

The effects of CO2 on propionic acid production and cell growth in glycerol or glucose fermentation were investigated in this study. In glycerol fermentation, the volumetric productivity of propionic acid with CO2 supplementation reached 2.94g/L/day, compared to 1.56g/L/day without CO2. The cell growth using glycerol was also significantly enhanced with CO2. In addition, the yield and productivity of succinate, the main intermediate in Wood-Werkman cycle, increased 81% and 280%, respectively; consistent with the increased activities of pyruvate carboxylase and propionyl CoA transferase, two key enzymes in the Wood-Werkman cycle. However, in glucose fermentation CO2 had minimal effect on propionic acid production and cell growth. The carbon flux distributions using glycerol or glucose were also analyzed using a stoichiometric metabolic model. The calculated maintenance coefficient (mATP) increased 100%, which may explain the increase in the productivity of propionic acid in glycerol fermentation with CO2 supplement. Copyright © 2014 Elsevier Ltd. All rights reserved.

Sodium phenylbutyrate decreases plasma branched-chain amino acids in patients with urea cycle disorders.

PubMed

Burrage, Lindsay C; Jain, Mahim; Gandolfo, Laura; Lee, Brendan H; Nagamani, Sandesh C S

2014-01-01

Sodium phenylbutyrate (NaPBA) is a commonly used medication for the treatment of patients with urea cycle disorders (UCDs). Previous reports involving small numbers of patients with UCDs have shown that NaPBA treatment can result in lower plasma levels of the branched-chain amino acids (BCAA) but this has not been studied systematically. From a large cohort of patients (n=553) with UCDs enrolled in the Longitudinal Study of Urea Cycle Disorders, a collaborative multicenter study of the Urea Cycle Disorders Consortium, we evaluated whether treatment with NaPBA leads to a decrease in plasma BCAA levels. Our analysis shows that NaPBA use independently affects the plasma BCAA levels even after accounting for multiple confounding covariates. Moreover, NaPBA use increases the risk for BCAA deficiency. This effect of NaPBA seems specific to plasma BCAA levels, as levels of other essential amino acids are not altered by its use. Our study, in an unselected population of UCD subjects, is the largest to analyze the effects of NaPBA on BCAA metabolism and potentially has significant clinical implications. Our results indicate that plasma BCAA levels should to be monitored in patients treated with NaPBA since patients taking the medication are at increased risk for BCAA deficiency. On a broader scale, these findings could open avenues to explore NaPBA as a therapy in maple syrup urine disease and other common complex disorders with dysregulation of BCAA metabolism. Copyright © 2014 Elsevier Inc. All rights reserved.

Selective cerebral perfusion prevents abnormalities in glutamate cycling and neuronal apoptosis in a model of infant deep hypothermic circulatory arrest and reperfusion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kajimoto, Masaki; Ledee, Dolena R.; Olson, Aaron K.

Rationale: Deep hypothermic circulatory arrest (DHCA) is often required for the repair of complex congenital cardiac defects in infants. However, DHCA induces neuroapoptosis associated with later development of neurocognitive abnormalities. Selective cerebral perfusion (SCP) theoretically provides superior neural protection possibly through modifications in cerebral substrate oxidation and closely integrated glutamate cycling. Objectives: We tested the hypothesis that SCP modulates glucose entry into the citric acid cycle, and ameliorates abnormalities in glutamate flux which occur in association neuroapoptosis during DHCA. Methods and Results: Eighteen male Yorkshire piglets (age 34-44 days) were assigned randomly to 2 groups of 7 (DHCA or DHCAmore » with SCP for 60 minutes at 18 °C) and 4 control pigs without cardiopulmonary bypass support. After the completion of rewarming from DHCA, 13-Carbon-labeled (13C) glucose as a metabolic tracer was infused. We used gas chromatography-mass spectrometry (GCMS) and nuclear magnetic resonance for metabolic analysis in the frontal cortex. Following 2.5 hours of cerebral reperfusion, we observed similar cerebral ATP levels, absolute levels of lactate and citric acid cycle intermediates, and 13C-enrichment. However, DHCA induced significant abnormalities in glutamate cycling resulting in reduced glutamate/glutamine and elevated γ-aminobutyric acid (GABA)/glutamate along with neuroapoptosis (TUNEL), which were all prevented by SCP. Conclusions: DHCA alone induces abnormalities in cycling of the major neurotransmitters in association with neuroapoptosis, but does not alter cerebral glucose utilization during reperfusion. The data suggest that SCP prevents these modifications in glutamate/glutamine/GABA cycling and protects the cerebral cortex from neuroapoptosis.« less

Stability and anti-glycation properties of intermediate moisture apple products fortified with green tea.

PubMed

Lavelli, Vera; Corey, Mark; Kerr, William; Vantaggi, Claudia

2011-07-15

Intermediate moisture products made from blanched apple flesh and green tea extract (about 6mg of monomeric flavan 3-ols added per g of dry apple) or blanched apple flesh (control) were produced, and their quality attributes were investigated over storage for two months at water activity (a(w)) levels of 0.55 and 0.75, at 30°C. Products were evaluated for colour (L(∗), a(∗), and b(∗) Hunter's parameters), phytochemical contents (flavan 3-ols, chlorogenic acid, dihydrochalcones, ascorbic acid and total polyphenols), ferric reducing antioxidant potential, 2,2-diphenyl-1-(2,4,6-trinitrophenyl)hydrazyl radical-scavenging activity and ability to inhibit formation of fructose-induced advanced glycation end-products. During storage of the fortified and unfortified intermediate moisture apples, water availability was sufficient to support various chemical reactions involving phytochemicals, which degraded at different rates: ascorbic acid>flavan 3-ols>dihydrochalcones and chlorogenic acid. Colour variations occurred at slightly slower rates after green tea addition. In the intermediate moisture apple, antioxidant and anti-glycoxidative properties decreased at similar rates (half-life was about 80d at a(w) of 0.75, 30°C). In the green tea-fortified intermediate moisture apple, the antioxidant activity decreased at a slow rate (half-life was 165d at a(w) of 0.75, 30°C) and the anti-glycoxidative properties did not change, indicating that flavan 3-ol degradation involved the formation of derivatives that retained the properties of their parent compounds. Since these properties are linked to oxidative- and advanced glycation end-product-related diseases, these results suggest that green tea fortification of intermediate moisture apple products could be a valuable means of product innovation, to address consumers' nutritional needs. Copyright © 2011 Elsevier Ltd. All rights reserved.

Production and characterization of murine models of classic and intermediate maple syrup urine disease

PubMed Central

Homanics, Gregg E; Skvorak, Kristen; Ferguson, Carolyn; Watkins, Simon; Paul, Harbhajan S

2006-01-01

Background Maple Syrup Urine Disease (MSUD) is an inborn error of metabolism caused by a deficiency of branched-chain keto acid dehydrogenase. MSUD has several clinical phenotypes depending on the degree of enzyme deficiency. Current treatments are not satisfactory and require new approaches to combat this disease. A major hurdle in developing new treatments has been the lack of a suitable animal model. Methods To create a murine model of classic MSUD, we used gene targeting and embryonic stem cell technologies to create a mouse line that lacked a functional E2 subunit gene of branched-chain keto acid dehydrogenase. To create a murine model of intermediate MSUD, we used transgenic technology to express a human E2 cDNA on the knockout background. Mice of both models were characterized at the molecular, biochemical, and whole animal levels. Results By disrupting the E2 subunit gene of branched-chain keto acid dehydrogenase, we created a gene knockout mouse model of classic MSUD. The homozygous knockout mice lacked branched-chain keto acid dehydrogenase activity, E2 immunoreactivity, and had a 3-fold increase in circulating branched-chain amino acids. These metabolic derangements resulted in neonatal lethality. Transgenic expression of a human E2 cDNA in the liver of the E2 knockout animals produced a model of intermediate MSUD. Branched-chain keto acid dehydrogenase activity was 5–6% of normal and was sufficient to allow survival, but was insufficient to normalize circulating branched-chain amino acids levels, which were intermediate between wildtype and the classic MSUD mouse model. Conclusion These mice represent important animal models that closely approximate the phenotype of humans with the classic and intermediate forms of MSUD. These animals provide useful models to further characterize the pathogenesis of MSUD, as well as models to test novel therapeutic strategies, such as gene and cellular therapies, to treat this devastating metabolic disease. PMID

Self-organizing biochemical cycles

NASA Technical Reports Server (NTRS)

Orgel, L. E.; Bada, J. L. (Principal Investigator)

2000-01-01

I examine the plausibility of theories that postulate the development of complex chemical organization without requiring the replication of genetic polymers such as RNA. One conclusion is that theories that involve the organization of complex, small-molecule metabolic cycles such as the reductive citric acid cycle on mineral surfaces make unreasonable assumptions about the catalytic properties of minerals and the ability of minerals to organize sequences of disparate reactions. Another conclusion is that data in the Beilstein Handbook of Organic Chemistry that have been claimed to support the hypothesis that the reductive citric acid cycle originated as a self-organized cycle can more plausibly be interpreted in a different way.

Intermediate states in the binding process of folic acid to folate receptor α: insights by molecular dynamics and metadynamics.

PubMed

Della-Longa, Stefano; Arcovito, Alessandro

2015-01-01

Folate receptor α (FRα) is a cell surface, glycophosphatidylinositol-anchored protein which has focussed attention as a therapeutic target and as a marker for the diagnosis of cancer. It has a high affinity for the dietary supplemented folic acid (FOL), carrying out endocytic transport across the cell membrane and delivering the folate at the acidic pH of the endosome. Starting from the recently reported X-ray structure at pH 7, 100 ns classical molecular dynamics simulations have been carried out on the FRα-FOL complex; moreover, the ligand dissociation process has been studied by metadynamics, a recently reported method for the analysis of free-energy surfaces (FES), providing clues on the intermediate states and their energy terms. Multiple dissociation runs were considered to enhance the configurational sampling; a final clustering of conformations within the averaged FES provides the representative structures of several intermediate states, within an overall barrier for ligand escape of about 75 kJ/mol. Escaping of FOL to solvent occurs while only minor changes affect the FRα conformation of the binding pocket. During dissociation, the FOL molecule translates and rotates around a turning point located in proximity of the receptor surface. FOL at this transition state assumes an "L" shaped conformation, with the pteridin ring oriented to optimize stacking within W102 and W140 residues, and the negatively charged glutamate tail, outside the receptor, interacting with the positively charged R103 and R106 residues, that contrary to the bound state, are solvent exposed. We show that metadynamics method can provide useful insights at the atomistic level on the effects of point-mutations affecting functionality, thus being a very promising tool for any study related to folate-targeted drug delivery or cancer therapies involving folate uptake.

Intermediate states in the binding process of folic acid to folate receptor α: insights by molecular dynamics and metadynamics

NASA Astrophysics Data System (ADS)

Della-Longa, Stefano; Arcovito, Alessandro

2015-01-01

Folate receptor α (FRα) is a cell surface, glycophosphatidylinositol-anchored protein which has focussed attention as a therapeutic target and as a marker for the diagnosis of cancer. It has a high affinity for the dietary supplemented folic acid (FOL), carrying out endocytic transport across the cell membrane and delivering the folate at the acidic pH of the endosome. Starting from the recently reported X-ray structure at pH 7, 100 ns classical molecular dynamics simulations have been carried out on the FRα-FOL complex; moreover, the ligand dissociation process has been studied by metadynamics, a recently reported method for the analysis of free-energy surfaces (FES), providing clues on the intermediate states and their energy terms. Multiple dissociation runs were considered to enhance the configurational sampling; a final clustering of conformations within the averaged FES provides the representative structures of several intermediate states, within an overall barrier for ligand escape of about 75 kJ/mol. Escaping of FOL to solvent occurs while only minor changes affect the FRα conformation of the binding pocket. During dissociation, the FOL molecule translates and rotates around a turning point located in proximity of the receptor surface. FOL at this transition state assumes an "L" shaped conformation, with the pteridin ring oriented to optimize stacking within W102 and W140 residues, and the negatively charged glutamate tail, outside the receptor, interacting with the positively charged R103 and R106 residues, that contrary to the bound state, are solvent exposed. We show that metadynamics method can provide useful insights at the atomistic level on the effects of point-mutations affecting functionality, thus being a very promising tool for any study related to folate-targeted drug delivery or cancer therapies involving folate uptake.

Greatly Suppressed Shuttle Effect for Improved Lithium Sulfur Battery Performance through Short Chain Intermediates.

PubMed

Xu, Na; Qian, Tao; Liu, Xuejun; Liu, Jie; Chen, Yu; Yan, Chenglin

2017-01-11

The high solubility of long-chain lithium polysulfides and their infamous shuttle effect in lithium sulfur battery lead to rapid capacity fading along with low Coulombic efficiency. To address above issues, we propose a new strategy to suppress the shuttle effect for greatly enhanced lithium sulfur battery performance mainly through the formation of short-chain intermediates during discharging, which allows significant improvements including high capacity retention of 1022 mAh/g with 87% retention for 450 cycles. Without LiNO 3 -containing electrolytes, the excellent Coulombic efficiency of ∼99.5% for more than 500 cycles is obtained, suggesting the greatly suppressed shuttle effect. In situ UV/vis analysis of electrolyte during cycling reveals that the short-chain Li 2 S 2 and Li 2 S 3 polysulfides are detected as main intermediates, which are theoretically verified by density functional theory (DFT) calculations. Our strategy may open up a new avenue for practical application of lithium sulfur battery.

Crystal Structures of Intermediates in the Nitroalkane Oxidase Reaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heroux, A.; Bozinovski, D; Valley, M

2009-01-01

The flavoenzyme nitroalkane oxidase is a member of the acyl-CoA dehydrogenase superfamily. Nitroalkane oxidase catalyzes the oxidation of neutral nitroalkanes to nitrite and the corresponding aldehydes or ketones. Crystal structures to 2.2 {angstrom} resolution or better of enzyme complexes with bound substrates and of a trapped substrate-flavin adduct are described. The D402N enzyme has no detectable activity with neutral nitroalkanes. The structure of the D402N enzyme crystallized in the presence of 1-nitrohexane or 1-nitrooctane shows the presence of the substrate in the binding site. The aliphatic chain of the substrate extends into a tunnel leading to the enzyme surface. Themore » oxygens of the substrate nitro group interact both with amino acid residues and with the 2'-hydroxyl of the FAD. When nitroalkane oxidase oxidizes nitroalkanes in the presence of cyanide, an electrophilic flavin imine intermediate can be trapped (Valley, M. P., Tichy, S. E., and Fitzpatrick, P. F. (2005) J. Am. Chem. Soc. 127, 2062-2066). The structure of the enzyme trapped with cyanide during oxidation of 1-nitrohexane shows the presence of the modified flavin. A continuous hydrogen bond network connects the nitrogen of the CN-hexyl-FAD through the FAD 2'-hydroxyl to a chain of water molecules extending to the protein surface. Together, our complementary approaches provide strong evidence that the flavin cofactor is in the appropriate oxidation state and correlates well with the putative intermediate state observed within each of the crystal structures. Consequently, these results provide important structural descriptions of several steps along the nitroalkane oxidase reaction cycle.« less

Functionalised carboxylic acids in atmospheric particles: An annual cycle revealing seasonal trends and possible sources

NASA Astrophysics Data System (ADS)

Teich, Monique; van Pinxteren, Dominik; Herrmann, Hartmut

2013-04-01

Carboxylic acids represent a major fraction of the water soluble organic carbon (WSOC) in atmospheric particles. Among the particle phase carboxylic acids, straight-chain monocarboxylic acids (MCA) and dicarboxylic acids (DCA) with 2-10 carbon atoms have extensively been studied in the past. However, only a few studies exist dealing with functionalised carboxylic acids, i.e. having additional hydroxyl-, oxo- or nitro-groups. Regarding atmospheric chemistry, these functionalised carboxylic acids are of particular interest as they are supposed to be formed during atmospheric oxidation processes, e.g. through radical reactions. Therefore they can provide insights into the tropospheric multiphase chemistry. During this work 28 carboxylic acids (4 functionalised aliphatic MCAs, 5 aromatic MCAs, 3 nitroaromatic MCAs, 6 aliphatic DCAs, 6 functionalised aliphatic DCAs, 4 aromatic DCAs) were quantitatively determined in 256 filter samples taken at the rural research station Melpitz (Saxony, Germany) with a PM10 Digitel DHA-80 filter sampler. All samples were taken in 2010 covering a whole annual cycle. The resulting dataset was examined for a possible seasonal dependency of the acid concentrations. Furthermore the influence of the air mass origin on the acid concentrations was studied based on a simple two-sector classification (western or eastern sector) using a back trajectory analysis. Regarding the annual average, adipic acid was found to be the most abundant compound with a mean concentration of 7.8 ng m-3 followed by 4-oxopimelic acid with 6.1 ng m-3. The sum of all acid concentrations showed two maxima during the seasonal cycle; one in summer and one in winter, whereas the highest overall acid concentrations were found in summer. In general the target acids could be divided into two different groups, where one group has its maximum concentration in summer and the other group during winter. The first group contains all investigated aliphatic mono- and dicarboxylic

Protonation of a peroxodiiron(III) complex and conversion to a diiron(III/IV) intermediate: implications for proton-assisted O-O bond cleavage in nonheme diiron enzymes.

PubMed

Cranswick, Matthew A; Meier, Katlyn K; Shan, Xiaopeng; Stubna, Audria; Kaizer, Jószef; Mehn, Mark P; Münck, Eckard; Que, Lawrence

2012-10-01

Oxygenation of a diiron(II) complex, [Fe(II)(2)(μ-OH)(2)(BnBQA)(2)(NCMe)(2)](2+) [2, where BnBQA is N-benzyl-N,N-bis(2-quinolinylmethyl)amine], results in the formation of a metastable peroxodiferric intermediate, 3. The treatment of 3 with strong acid affords its conjugate acid, 4, in which the (μ-oxo)(μ-1,2-peroxo)diiron(III) core of 3 is protonated at the oxo bridge. The core structures of 3 and 4 are characterized in detail by UV-vis, Mössbauer, resonance Raman, and X-ray absorption spectroscopies. Complex 4 is shorter-lived than 3 and decays to generate in ~20% yield of a diiron(III/IV) species 5, which can be identified by electron paramagnetic resonance and Mössbauer spectroscopies. This reaction sequence demonstrates for the first time that protonation of the oxo bridge of a (μ-oxo)(μ-1,2-peroxo)diiron(III) complex leads to cleavage of the peroxo O-O bond and formation of a high-valent diiron complex, thereby mimicking the steps involved in the formation of intermediate X in the activation cycle of ribonucleotide reductase.

DIBROMOACETIC ACID-INDUCED ELEVATIONS IN CIRCULATING ESTRADIOL: EFFECTS IN BOTH CYCLING AND OVARIECTOMIZED/STEROID-PRIMED FEMALE RATS

EPA Science Inventory

RTD-03-031
Goldman, JM and Murr, AS. Dibromoacetic Acid-induced Elevations in Circulating Estradiol: Effects in Both Cycling and Ovariectomized/Steroid-primed Female Rats. Reproductive Toxicology (in press).

Abstract

Oral exposures to high concentrations of th...

Enzymes in Glycolysis and the Citric Acid Cycle in the Yeast and Mycelial Forms of Paracoccidioides brasiliensis

PubMed Central

Kanetsuna, Fuminori; Carbonell, Luis M.

1966-01-01

Kanetsuna, Fuminori (Instituto Venezolano de Investigaciones Cientificas, Caracas, Venezuela), and Luis M. Carbonell. Enzymes in glycolysis and the citric acid cycle in the yeast and mycelial forms of Paracoccidioides brasiliensis. J. Bacteriol. 92:1315–1320. 1966.—Enzymatic activities in glycolysis, the hexose monophosphate shunt, and the citric acid cycle in cell-free extracts of the yeast and mycelial forms of Paracoccidioides brasiliensis were examined comparatively. Both forms have the enzymes of these pathways. Activities of glucose-6-phosphate dehydrogenase and malic dehydrogenase of the mycelial form were higher than those of the yeast form. Another 15 enzymatic activities of the mycelial form were lower than those of the yeast form. The activity of glyceraldehyde-3-phosphate dehydrogenase showed the most marked difference between the two forms, its activity in the mycelial form being about 20% of that in the yeast form. PMID:5924267

A reverse KREBS cycle in photosynthesis: consensus at last

NASA Technical Reports Server (NTRS)

Buchanan, B. B.; Arnon, D. I.

1990-01-01

The Krebs cycle (citric acid or tricarboxylic acid cycle), the final common pathway in aerobic metabolism for the oxidation of carbohydrates, fatty acids and amino acids, is known to be irreversible. It liberates CO2 and generates NADH whose aerobic oxidation yields ATP but it does not operate in reverse as a biosynthetic pathway for CO2 assimilation. In 1966, our laboratory described a cyclic pathway for CO2 assimilation (Evans, Buchanan and Arnon 1966) that was unusual in two respects: (i) it provided the first instance of an obligate photoautotroph that assimilated CO2 by a pathway different from Calvin's reductive pentose phosphate cycle (Calvin 1962) and (ii) in its overall effect the new cycle was a reversal of the Krebs cycle. Named the 'reductive carboxylic acid cycle' (sometimes also called the reductive tricarboxylic acid cycle) the new cycle appeared to be the sole CO2 assimilation pathway in Chlorobium thiosulfatophilum (Evans et al. 1966) (now known as Chlorobium limicola forma thiosulfatophilum). Chlorobium is a photosynthetic green sulfur bacterium that grows anaerobically in an inorganic medium with sulfide and thiosulfate as electron donors and CO2 as an obligatory carbon source. In the ensuing years, the new cycle was viewed with skepticism. Not only was it in conflict with the prevailing doctrine that the 'one important property ... shared by all (our emphasis) autotrophic species is the assimilation of CO2 via the Calvin cycle' (McFadden 1973) but also some of its experimental underpinnings were challenged. It is only now that in the words of one of its early skeptics (Tabita 1988) 'a long and tortuous controversy' has ended with general acceptance of the reductive carboxylic acid cycle as a photosynthetic CO2 assimilation pathway distinct from the pentose cycle. (Henceforth, to minimize repetitiveness, the reductive pentose phosphate cycle will often be referred to as the pentose cycle and the reductive carboxylic acid cycle as the carboxylic

A reverse KREBS cycle in photosynthesis: consensus at last.

PubMed

Buchanan, B B; Arnon, D I

1990-01-01

The Krebs cycle (citric acid or tricarboxylic acid cycle), the final common pathway in aerobic metabolism for the oxidation of carbohydrates, fatty acids and amino acids, is known to be irreversible. It liberates CO2 and generates NADH whose aerobic oxidation yields ATP but it does not operate in reverse as a biosynthetic pathway for CO2 assimilation. In 1966, our laboratory described a cyclic pathway for CO2 assimilation (Evans, Buchanan and Arnon 1966) that was unusual in two respects: (i) it provided the first instance of an obligate photoautotroph that assimilated CO2 by a pathway different from Calvin's reductive pentose phosphate cycle (Calvin 1962) and (ii) in its overall effect the new cycle was a reversal of the Krebs cycle. Named the 'reductive carboxylic acid cycle' (sometimes also called the reductive tricarboxylic acid cycle) the new cycle appeared to be the sole CO2 assimilation pathway in Chlorobium thiosulfatophilum (Evans et al. 1966) (now known as Chlorobium limicola forma thiosulfatophilum). Chlorobium is a photosynthetic green sulfur bacterium that grows anaerobically in an inorganic medium with sulfide and thiosulfate as electron donors and CO2 as an obligatory carbon source. In the ensuing years, the new cycle was viewed with skepticism. Not only was it in conflict with the prevailing doctrine that the 'one important property ... shared by all (our emphasis) autotrophic species is the assimilation of CO2 via the Calvin cycle' (McFadden 1973) but also some of its experimental underpinnings were challenged. It is only now that in the words of one of its early skeptics (Tabita 1988) 'a long and tortuous controversy' has ended with general acceptance of the reductive carboxylic acid cycle as a photosynthetic CO2 assimilation pathway distinct from the pentose cycle. (Henceforth, to minimize repetitiveness, the reductive pentose phosphate cycle will often be referred to as the pentose cycle and the reductive carboxylic acid cycle as the carboxylic

Solvent effects in acid-catalyzed dehydration of the Diels-Alder cycloadduct between 2,5-dimethylfuran and maleic anhydride

NASA Astrophysics Data System (ADS)

Salavati-fard, Taha; Caratzoulas, Stavros; Doren, Douglas J.

2017-03-01

Dehydration of the cycloadduct produced from the Diels-Alder reaction between 2,5-dimethylfuran and maleic anhydride to 3,6-dimethylphthalic anhydride exemplifies an important step in producing platform chemicals from biomass. The mechanisms of dehydration and catalytic effects of Lewis and Brønsted acids are investigated with density functional theory. The uncatalyzed reaction has a very high activation barrier (68.7 kcal/mol) in the gas phase and it is not significantly affected by solvation. With a Lewis acid catalyst, modeled as an alkali ion, the activation barriers are reduced, but intermediates are also stabilized. The net effect in vacuum is that the energetic span, or apparent activation energy of the catalytic cycle, is 77.9 kcal/mol, even higher than the barrier in the uncatalyzed case. In solution, however, the energetic span is reduced by as much as 20 kcal/mol, due to differences in the solvation energy of the transition states and intermediates. In the case of a Brønsted acid catalyst, modeled as a proton, the gas phase transition state energies are reduced even more than in the Lewis acid case, and there is no strong stabilization of the intermediates. The energetic span in vacuum is only 13.8 kcal/mol and is reduced even further in solution. Brønsted acid catalysis appears to be the preferred mechanism for dehydration of this cycloadduct. Since the Diels-Alder reaction that produced the molecule has previously been shown to be catalyzed by Brønsted acids, this suggests that a single catalyst could be used to accelerate both steps.

The Variations of Glycolysis and TCA Cycle Intermediate Levels Grown in Iron and Copper Mediums of Trichoderma harzianum.

PubMed

Tavsan, Zehra; Ayar Kayali, Hulya

2015-05-01

The efficiency of optimal metabolic function by microorganism depends on various parameters, especially essential metal supplementation. In the present study, the effects of iron and copper metals on metabolism were investigated by determination of glycolysis and tricarboxylic acid (TCA) cycle metabolites' levels with respect to the metal concentrations and incubation period in Trichoderma harzianum. The pyruvate and citrate levels of T. harzianum increased up to 15 mg/L of copper via redirection of carbon flux though glycolysis by suppression of pentose phosphate pathway (PPP). However, the α-ketoglutarate levels decreased at concentration higher than 5 mg/L of copper to overcome damage of oxidative stress. The fumarate levels correlated with the α-ketoglutarate levels because of substrate limitation. Besides, in T. harzianum cells grown in various concentrations of iron-containing medium, the intracellular pyruvate, citrate, and α-ketoglutarate levels showed positive correlation with iron concentration due to modifying of expression of glycolysis and TCA cycle enzymes via a mechanism involving cofactor or allosteric regulation. However, as a result of consuming of prior substrates required for fumarate production, its levels rose up to 10 mg/L.

A Role for the Krebs Cycle Intermediate Citrate in Metabolic Reprogramming in Innate Immunity and Inflammation

PubMed Central

Williams, Niamh C.; O’Neill, Luke A. J.

2018-01-01

Metabolism in immune cells is no longer thought of as merely a process for adenosine triphosphate (ATP) production, biosynthesis, and catabolism. The reprogramming of metabolic pathways upon activation is also for the production of metabolites that can act as immune signaling molecules. Activated dendritic cells (DCs) and macrophages have an altered Krebs cycle, one consequence of which is the accumulation of both citrate and succinate. Citrate is exported from the mitochondria via the mitochondrial citrate- carrier. Cytosolic metabolism of citrate to acetyl-coenzyme A (acetyl-CoA) is important for both fatty-acid synthesis and protein acetylation, both of which have been linked to macrophage and DC activation. Citrate-derived itaconate has a direct antibacterial effect and also has been shown to act as an anti-inflammatory agent, inhibiting succinate dehydrogenase. These findings identify citrate as an important metabolite for macrophage and DC effector function. PMID:29459863

A Role for the Krebs Cycle Intermediate Citrate in Metabolic Reprogramming in Innate Immunity and Inflammation.

PubMed

Williams, Niamh C; O'Neill, Luke A J

2018-01-01

Metabolism in immune cells is no longer thought of as merely a process for adenosine triphosphate (ATP) production, biosynthesis, and catabolism. The reprogramming of metabolic pathways upon activation is also for the production of metabolites that can act as immune signaling molecules. Activated dendritic cells (DCs) and macrophages have an altered Krebs cycle, one consequence of which is the accumulation of both citrate and succinate. Citrate is exported from the mitochondria via the mitochondrial citrate- carrier. Cytosolic metabolism of citrate to acetyl-coenzyme A (acetyl-CoA) is important for both fatty-acid synthesis and protein acetylation, both of which have been linked to macrophage and DC activation. Citrate-derived itaconate has a direct antibacterial effect and also has been shown to act as an anti-inflammatory agent, inhibiting succinate dehydrogenase. These findings identify citrate as an important metabolite for macrophage and DC effector function.

Correlation between citric acid and nitrate metabolisms during CAM cycle in the atmospheric bromeliad Tillandsia pohliana.

PubMed

Freschi, Luciano; Rodrigues, Maria Aurineide; Tiné, Marco Aurélio Silva; Mercier, Helenice

2010-12-15

Crassulacean acid metabolism (CAM) confers crucial adaptations for plants living under frequent environmental stresses. A wide metabolic plasticity can be found among CAM species regarding the type of storage carbohydrate, organic acid accumulated at night and decarboxylating system. Consequently, many aspects of the CAM pathway control are still elusive while the impact of this photosynthetic adaptation on nitrogen metabolism has remained largely unexplored. In this study, we investigated a possible link between the CAM cycle and the nitrogen assimilation in the atmospheric bromeliad Tillandsia pohliana by simultaneously characterizing the diel changes in key enzyme activities and metabolite levels of both organic acid and nitrate metabolisms. The results revealed that T. pohliana performed a typical CAM cycle in which phosphoenolpyruvate carboxylase and phosphoenolpyruvate carboxykinase phosphorylation seemed to play a crucial role to avoid futile cycles of carboxylation and decarboxylation. Unlike all other bromeliads previously investigated, almost equimolar concentrations of malate and citrate were accumulated at night. Moreover, a marked nocturnal depletion in the starch reservoirs and an atypical pattern of nitrate reduction restricted to the nighttime were also observed. Since reduction and assimilation of nitrate requires a massive supply of reducing power and energy and considering that T. pohliana lives overexposed to the sunlight, we hypothesize that citrate decarboxylation might be an accessory mechanism to increase internal CO₂ concentration during the day while its biosynthesis could provide NADH and ATP for nocturnal assimilation of nitrate. Therefore, besides delivering photoprotection during the day, citrate might represent a key component connecting both CAM pathway and nitrogen metabolism in T. pohliana; a scenario that certainly deserves further study not only in this species but also in other CAM plants that nocturnally accumulate citrate

Diel cycling of zinc in a stream impacted by acid rock drainage: Initial results from a new in situ Zn analyzer

USGS Publications Warehouse

Chapin, T.P.; Nimick, D.A.; Gammons, C.H.; Wanty, R.B.

2007-01-01

Recent work has demonstrated that many trace metals undergo dramatic diel (24-h) cycles in near neutral pH streams with metal concentrations reproducibly changing up to 500% during the diel period (Nimick et al., 2003). To examine diel zinc cycles in streams affected by acid rock drainage, we have developed a novel instrument, the Zn-DigiScan, to continuously monitor in situ zinc concentrations in near real-time. Initial results from a 3-day deployment at Fisher Creek, Montana have demonstrated the ability of the Zn-DigiScan to record diel Zn cycling at levels below 100 ??g/l. Longer deployments of this instrument could be used to examine the effects of episodic events such as rainstorms and snowmelt pulses on zinc loading in streams affected by acid rock drainage. ?? Springer Science+Business Media B.V. 2006.

Tandem dissolution of UO 3 in amide-based acidic ionic liquid and in situ electrodeposition of UO 2 with regeneration of the ionic liquid: a closed cycle

DOE PAGES

Wanigasekara, Eranda; Freiderich, John W.; Sun, Xiao-Guang; ...

2016-05-19

A closed cycle is demonstrated for the tandem dissolution and electroreduction of UO 3 to UO 2 with regeneration of the acidic ionic liquid. The dissolution is achieved by use of the acidic ionic liquid N,N-dimethylacetimidium bis(trifluoromethanesulfonimide) in 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonimide) serving as the diluent. Bulk electrolysis performed at 1.0 V vs. Ag reference yields a dark brown-black uranium deposit (UO 2) on the cathode. Anodic oxidation of water in the presence of dimethylacetamide regenerates the acidic ionic liquid. We have demonstrated the individual steps in the cycle together with a sequential dissolution, electroreduction, and regeneration cycle.

Tandem dissolution of UO 3 in amide-based acidic ionic liquid and in situ electrodeposition of UO 2 with regeneration of the ionic liquid: a closed cycle

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wanigasekara, Eranda; Freiderich, John W.; Sun, Xiao-Guang

A closed cycle is demonstrated for the tandem dissolution and electroreduction of UO 3 to UO 2 with regeneration of the acidic ionic liquid. The dissolution is achieved by use of the acidic ionic liquid N,N-dimethylacetimidium bis(trifluoromethanesulfonimide) in 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonimide) serving as the diluent. Bulk electrolysis performed at 1.0 V vs. Ag reference yields a dark brown-black uranium deposit (UO 2) on the cathode. Anodic oxidation of water in the presence of dimethylacetamide regenerates the acidic ionic liquid. We have demonstrated the individual steps in the cycle together with a sequential dissolution, electroreduction, and regeneration cycle.

Enantioselective oxidation of racemic lactic acid to D-lactic acid and pyruvic acid by Pseudomonas stutzeri SDM.

PubMed

Gao, Chao; Qiu, Jianhua; Li, Jingchen; Ma, Cuiqing; Tang, Hongzhi; Xu, Ping

2009-03-01

D-lactic acid and pyruvic acid are two important building block intermediates. Production of D-lactic acid and pyruvic acid from racemic lactic acid by biotransformation is economically interesting. Biocatalyst prepared from 9 g dry cell wt l(-1) of Pseudomonas stutzeri SDM could catalyze 45.00 g l(-1)DL-lactic acid into 25.23 g l(-1)D-lactic acid and 19.70 g l(-1) pyruvic acid in 10h. Using a simple ion exchange process, D-lactic acid and pyruvic acid were effectively separated from the biotransformation system. Co-production of d-lactic acid and pyruvic acid by enantioselective oxidation of racemic lactic acid is technically feasible.

Isoporphyrin Intermediate in Heme Oxygenase Catalysis

PubMed Central

Evans, John P.; Niemevz, Fernando; Buldain, Graciela; de Montellano, Paul Ortiz

2008-01-01

Human heme oxygenase-1 (hHO-1) catalyzes the O2- and NADPH-dependent oxidation of heme to biliverdin, CO, and free iron. The first step involves regiospecific insertion of an oxygen atom at the α-meso carbon by a ferric hydroperoxide and is predicted to proceed via an isoporphyrin π-cation intermediate. Here we report spectroscopic detection of a transient intermediate during oxidation by hHO-1 of α-meso-phenylheme-IX, α-meso-(p-methylphenyl)-mesoheme-III, and α-meso-(p-trifluoromethylphenyl)-mesoheme-III. In agreement with previous experiments (Wang, J., Niemevz, F., Lad, L., Huang, L., Alvarez, D. E., Buldain, G., Poulos, T. L., and Ortiz de Montellano, P. R. (2004) J. Biol. Chem. 279, 42593–42604), only the α-biliverdin isomer is produced with concomitant formation of the corresponding benzoic acid. The transient intermediate observed in the NADPH-P450 reductase-catalyzed reaction accumulated when the reaction was supported by H2O2 and exhibited the absorption maxima at 435 and 930 nm characteristic of an isoporphyrin. Product analysis by reversed phase high performance liquid chromatography and liquid chromatography electrospray ionization mass spectrometry of the product generated with H2O2 identified it as an isoporphyrin that, on quenching, decayed to benzoylbiliverdin. In the presence of H218O2, one labeled oxygen atom was incorporated into these products. The hHO-1-isoporphyrin complexes were found to have half-lives of 1.7 and 2.4 h for the p-trifluoromethyl- and p-methyl-substituted phenylhemes, respectively. The addition of NADPH-P450 reductase to the H2O2-generated hHO-1-isoporphyrin complex produced α-biliverdin, confirming its role as a reaction intermediate. Identification of an isoporphyrin intermediate in the catalytic sequence of hHO-1, the first such intermediate observed in hemoprotein catalysis, completes our understanding of the critical first step of heme oxidation. PMID:18487208

Cytoskeleton in motion: the dynamics of keratin intermediate filaments in epithelia.

PubMed

Windoffer, Reinhard; Beil, Michael; Magin, Thomas M; Leube, Rudolf E

2011-09-05

Epithelia are exposed to multiple forms of stress. Keratin intermediate filaments are abundant in epithelia and form cytoskeletal networks that contribute to cell type-specific functions, such as adhesion, migration, and metabolism. A perpetual keratin filament turnover cycle supports these functions. This multistep process keeps the cytoskeleton in motion, facilitating rapid and protein biosynthesis-independent network remodeling while maintaining an intact network. The current challenge is to unravel the molecular mechanisms underlying the regulation of the keratin cycle in relation to actin and microtubule networks and in the context of epithelial tissue function.

Cytoskeleton in motion: the dynamics of keratin intermediate filaments in epithelia

PubMed Central

Windoffer, Reinhard; Beil, Michael; Magin, Thomas M.

2011-01-01

Epithelia are exposed to multiple forms of stress. Keratin intermediate filaments are abundant in epithelia and form cytoskeletal networks that contribute to cell type–specific functions, such as adhesion, migration, and metabolism. A perpetual keratin filament turnover cycle supports these functions. This multistep process keeps the cytoskeleton in motion, facilitating rapid and protein biosynthesis–independent network remodeling while maintaining an intact network. The current challenge is to unravel the molecular mechanisms underlying the regulation of the keratin cycle in relation to actin and microtubule networks and in the context of epithelial tissue function. PMID:21893596

The viability of a nonenzymatic reductive citric acid cycle - Kinetics and thermochemistry

USGS Publications Warehouse

Ross, D.S.

2007-01-01

The likelihood of a functioning nonenzymatic reductive citric acid cycle, recently proposed as the precursor to biosynthesis on early Earth, is examined on the basis of the kinetics and thermochemistry of the acetate ??? pyruvate ??? oxaloacetate ??? malate sequence. Using data derived from studies of the Pd-catalyzed phosphinate reduction of carbonyl functions it is shown that the rate of conversion of pyruvate to malate with that system would have been much too slow to have played a role in the early chemistry of life, while naturally occurring reduction systems such as the fayalite-magnetite-quartz and pyrrhotite-pyrite-magnetite mineral assemblages would have provided even slower conversions. It is also shown that the production of pyruvate from acetate is too highly endoergic to be driven by a naturally occurring energy source such as pyrophosphate. It is thus highly doubtful that the cycle can operate at suitable rates without enzymes, and most unlikely that it could have participated in the chemistry leading to life. ?? 2006 Springer Science + Business Media B.V.

Quantitative RT-PCR Comparison of the Urea and Nitric Oxide Cycle Gene Transcripts in Adult Human Tissues

PubMed Central

Neill, Meaghan Anne; Aschner, Judy; Barr, Frederick; Summar, Marshall L.

2009-01-01

The urea cycle and nitric oxide cycle play significant roles in complex biochemical and physiologic reactions. These cycles have distinct biochemical goals including the clearance of waste nitrogen; the production of the intermediates ornithine, citrulline, and arginine for the urea cycle; and the production of nitric oxide for the nitric oxide pathway. Despite their disparate functions, the two pathways share two enzymes, argininosuccinic acid synthase and argininosuccinic acid lyase, and a transporter, citrin. Studying the gene expression of these enzymes is paramount in understanding these complex biochemical pathways. Here, we examine the expression of genes involved in the urea cycle and the nitric oxide cycle in a panel of eleven different tissue samples obtained from individual adults without known inborn errors of metabolism. In this study, the pattern of co-expressed enzymes provides a global view of the metabolic activity of the urea and nitric oxide cycles in human tissues. Our results show that these transcripts are differentially expressed in different tissues. The pattern of co-expressed enzymes provides a global view of the metabolic activity of the urea and nitric oxide cycles in human tissues. Using the co-expression profiles, we discovered that the combination of expression of enzyme transcripts as detected in our study, might serve to fulfill specific physiologic function(s) in tissue including urea production/nitrogen removal, arginine/citrulline production, nitric oxide production, and ornithine production. Our study reveals the importance of studying not only the expression profile of an enzyme of interest, but also studying the expression profiles of the other enzymes involved in a particular pathway so as to better understand the context of expression. The tissue patterns we observed highlight the variety of important functions they conduct and provide insight into many of the clinical observations from their disruption. PMID:19345634

Selective cerebral perfusion prevents abnormalities in glutamate cycling and neuronal apoptosis in a model of infant deep hypothermic circulatory arrest and reperfusion.

PubMed

Kajimoto, Masaki; Ledee, Dolena R; Olson, Aaron K; Isern, Nancy G; Robillard-Frayne, Isabelle; Des Rosiers, Christine; Portman, Michael A

2016-11-01

Deep hypothermic circulatory arrest is often required for the repair of complex congenital cardiac defects in infants. However, deep hypothermic circulatory arrest induces neuroapoptosis associated with later development of neurocognitive abnormalities. Selective cerebral perfusion theoretically provides superior neural protection possibly through modifications in cerebral substrate oxidation and closely integrated glutamate cycling. We tested the hypothesis that selective cerebral perfusion modulates glucose utilization, and ameliorates abnormalities in glutamate flux, which occur in association with neuroapoptosis during deep hypothermic circulatory arrest. Eighteen infant male Yorkshire piglets were assigned randomly to two groups of seven (deep hypothermic circulatory arrest or deep hypothermic circulatory arrest with selective cerebral perfusion for 60 minutes at 18℃) and four control pigs without cardiopulmonary bypass support. Carbon-13-labeled glucose as a metabolic tracer was infused, and gas chromatography-mass spectrometry and nuclear magnetic resonance were used for metabolic analysis in the frontal cortex. Following 2.5 h of cerebral reperfusion, we observed similar cerebral adenosine triphosphate levels, absolute levels of lactate and citric acid cycle intermediates, and carbon-13 enrichment among three groups. However, deep hypothermic circulatory arrest induced significant abnormalities in glutamate cycling resulting in reduced glutamate/glutamine and elevated γ-aminobutyric acid/glutamate along with neuroapoptosis, which were all prevented by selective cerebral perfusion. The data suggest that selective cerebral perfusion prevents these modifications in glutamate/glutamine/γ-aminobutyric acid cycling and protects the cerebral cortex from apoptosis. © The Author(s) 2016.

Acyl silicates and acyl aluminates as activated intermediates in peptide formation on clays

NASA Technical Reports Server (NTRS)

White, D. H.; Kennedy, R. M.; Macklin, J.

1984-01-01

Glycine reacts with heating on dried clays and other minerals to give peptides in much better yield than in the absence of mineral. This reaction was proposed to occur by way of an activated intermediate such as an acyl silicate or acyl aluminate analogous to acyl phosphates involved in several biochemical reactions including peptide bond synthesis. The proposed mechanism has been confirmed by trapping the intermediate, as well as by direct spectroscopic observation of a related intermediate. The reaction of amino acids on periodically dried mineral surfaces represents a widespead, geologically realistic setting for prebiotic peptide formation via in situ activation.

Gas-Phase Formation Rates of Nitric Acid and Its Isomers Under Urban Conditions

NASA Technical Reports Server (NTRS)

Okumura, M.; Mollner, A. K.; Fry, J. L.; Feng, L.

2005-01-01

Ozone formation in urban smog is controlled by a complex set of reactions which includes radical production from photochemical processes, catalytic cycles which convert NO to NO2, and termination steps that tie up reactive intermediates in long-lived reservoirs. The reaction OH + NO2 + M -4 HONO2 + M (la) is a key termination step because it transforms two short-lived reactive intermediates, OH and NO2, into relatively long-lived nitric acid. Under certain conditions (low VOC/NOx), ozone production in polluted urban airsheds can be highly sensitive to this reaction, but the rate parameters are not well constrained. This report summarizes the results of new laboratory studies of the OH + NO2 + M reaction including direct determination of the overall rate constant and branching ratio for the two reaction channels under atmospherically relevant conditions.

Advanced intermediate temperature sodium-nickel chloride batteries with ultra-high energy density

NASA Astrophysics Data System (ADS)

Li, Guosheng; Lu, Xiaochuan; Kim, Jin Y.; Meinhardt, Kerry D.; Chang, Hee Jung; Canfield, Nathan L.; Sprenkle, Vincent L.

2016-02-01

Sodium-metal halide batteries have been considered as one of the more attractive technologies for stationary electrical energy storage, however, they are not used for broader applications despite their relatively well-known redox system. One of the roadblocks hindering market penetration is the high-operating temperature. Here we demonstrate that planar sodium-nickel chloride batteries can be operated at an intermediate temperature of 190 °C with ultra-high energy density. A specific energy density of 350 Wh kg-1, higher than that of conventional tubular sodium-nickel chloride batteries (280 °C), is obtained for planar sodium-nickel chloride batteries operated at 190 °C over a long-term cell test (1,000 cycles), and it attributed to the slower particle growth of the cathode materials at the lower operating temperature. Results reported here demonstrate that planar sodium-nickel chloride batteries operated at an intermediate temperature could greatly benefit this traditional energy storage technology by improving battery energy density, cycle life and reducing material costs.

Poly(3-hydroxybutyrate) fuels the tricarboxylic acid cycle and de novo lipid biosynthesis during Bacillus anthracis sporulation.

PubMed

Sadykov, Marat R; Ahn, Jong-Sam; Widhelm, Todd J; Eckrich, Valerie M; Endres, Jennifer L; Driks, Adam; Rutkowski, Gregory E; Wingerd, Kevin L; Bayles, Kenneth W

2017-06-01

Numerous bacteria accumulate poly(3-hydroxybutyrate) (PHB) as an intracellular reservoir of carbon and energy in response to imbalanced nutritional conditions. In Bacillus spp., where PHB biosynthesis precedes the formation of the dormant cell type called the spore (sporulation), the direct link between PHB accumulation and efficiency of sporulation was observed in multiple studies. Although the idea of PHB as an intracellular carbon and energy source fueling sporulation was proposed several decades ago, the mechanisms underlying PHB contribution to sporulation have not been defined. Here, we demonstrate that PHB deficiency impairs Bacillus anthracis sporulation through diminishing the energy status of the cells and by reducing carbon flux into the tricarboxylic acid (TCA) cycle and de novo lipid biosynthesis. Consequently, this metabolic imbalance decreased biosynthesis of the critical components required for spore integrity and resistance, such as dipicolinic acid (DPA) and the spore's inner membrane. Supplementation of the PHB deficient mutant with exogenous fatty acids overcame these sporulation defects, highlighting the importance of the TCA cycle and lipid biosynthesis during sporulation. Combined, the results of this work reveal the molecular mechanisms of PHB contribution to B. anthracis sporulation and provide valuable insight into the metabolic requirements for this developmental process in Bacillus species. © 2017 John Wiley & Sons Ltd.

Pretreatment with oleic acid accelerates the entrance into the mitotic cycle of EGF-stimulated fibroblasts.

PubMed

Zugaza, J L; Casabiell, X A; Bokser, L; Eiras, A; Beiras, A; Casanueva, F F

1995-07-01

We have previously demonstrated that pretreatment of several cell lines with cis-unsaturated fatty acids, like oleic acid, blocks epidermal growth factor (EGF)-induced early ionic signals, and in particular the [Ca2+]i rise. In the present work we show that this blockade does not alter EGF-stimulated cellular proliferation evaluated by direct cell counting, but induces a powerful enhancement in the pulsed thymidine incorporation assay. The lack of effect of oleic acid on EGF-stimulated cellular proliferation was confirmed by repeated cell counts, cumulative thymidine incorporation, and protein synthesis, but a clear synergistic effect between oleic acid and EGF was again obtained by means of time course experiments with pulsed thymidine. Combined flow cytometry analysis and cell counts at earlier times in EGF-stimulated cells showed that oleic acids accelerates the entrance of cells into the replicative cycle leading to an earlier cell division. Afterward, these oleic acid-pretreated cells became delayed by an unknown compensatory mechanism in such a way that at 48 h post-EGF, the cell count in control and oleic acid-pretreated cells was equal. In conclusion (a) oleic acid accelerates or enhances the EGF mitogenic action and (b) in the long term cells compensate the initial perturbation with respect to untreated cells. As a side observation, the widely employed pulsed thymidine incorporation method as a measure of cell division could be extremely misleading unless experimental conditions are well controlled.

Synthesis and characterization of 3-ketohexadecanoic acid-1-14-C, DL-3-hydroxyhexadecanoic acid-1-14-C, and trans-2-hexadecenoic acid-1-14-C.

PubMed

Jones, J A; Blecher, M

1966-05-01

The chemical synthesis and characterization of three intermediates in the Beta oxidation of palmitic acid-1-(14)C by rat liver mitochondria, namely, 3-ketohexadecanoic acid-1-(14)C, DL-3-hydroxyhexadecanoic acid-1-(14)C, and trans-2-hexadecenoic acid-1-(14)C, are described.

Sarcocystis strixi, n. sp. from barred owls (Strix varia) definitive hosts and gamma interferon gene knockout mice as experimental intermediate host

USDA-ARS?s Scientific Manuscript database

Sarcocystis species have 2-host life cycles with the sexual cycle in the definitive hosts and an asexual cycle in the intermediate hosts. Raptors are definitive hosts for several species of Sarcocystis but intestinal infection with Sarcocystis has not been reported from Barred owls (Strix varia). He...

Steroid catechol degradation: disecoandrostane intermediates accumulated by Pseudomonas transposon mutant strains.

PubMed

Leppik, R A

1989-07-01

Eleven transposon mutant strains affected in bile acid catabolism were each found to form yellow, muconic-like intermediates from bile acids. To characterize these unstable intermediates, media from the growth of one of these mutants with deoxycholic acid was treated with ammonia, then the crude product was methylated with diazomethane. Four compounds were subsequently isolated; spectral evidence suggested that they were methyl 12 alpha-hydroxy-3-oxo-23,24-dinorchola-1,4-dien-22-oate, methyl 4-aza-12 beta-hydroxy-9(10)-secoandrosta-1,3,5-triene-9,17-dione-3-carboxyl ate, 4-aza-9 alpha, 12 beta-dihydroxy-9(10)-secoandrosta-1,3,5-trien-17-one-3- methyl carboxylate and 4 alpha-[3'-propionic acid]-5-amino-7 beta-hydroxy-7 alpha beta-methyl- 3a alpha, 4,7,7a-tetrahydro-1-indanone-delta-lactam. It is proposed that the mutants are blocked in the utilization of such muconic-like compounds as the 3,12 beta-dihydroxy-5,9,17-trioxo-4(5),9(10)- disecoandrostal (10),2-dien-4-oic acid formed from deoxycholic acid. A further mutant was examined, which converted deoxycholic acid to 12 alpha-hydroxyandrosta-1,4-dien-3,17-dione, but accumulated yellow products from steroids which lacked a 12 alpha-hydroxy function, such as chenodeoxycholic acid. The products from the latter acid were treated as above; spectral evidence suggested that the two compounds isolated were methyl 4-aza-7-hydroxy-9(10)-secoandrosta-1,3,5- triene-9,17-dione-3-carboxylate and 4 alpha-[1'alpha-hydroxy-3'-propionic acid]-5-amino-7a beta-methyl-3a alpha,4,7,7a-tetrahydro-1-indanone-delta-lactam.

Metabonomics Indicates Inhibition of Fatty Acid Synthesis, β-Oxidation, and Tricarboxylic Acid Cycle in Triclocarban-Induced Cardiac Metabolic Alterations in Male Mice.

PubMed

Xie, Wenping; Zhang, Wenpeng; Ren, Juan; Li, Wentao; Zhou, Lili; Cui, Yuan; Chen, Huiming; Yu, Wenlian; Zhuang, Xiaomei; Zhang, Zhenqing; Shen, Guolin; Li, Haishan

2018-02-14

Triclocarban (TCC) has been identified as a new environmental pollutant that is potentially hazardous to human health; however, the effects of short-term TCC exposure on cardiac function are not known. The aim of this study was to use metabonomics and molecular biology techniques to systematically elucidate the molecular mechanisms of TCC-induced effects on cardiac function in mice. Our results show that TCC inhibited the uptake, synthesis, and oxidation of fatty acids, suppressed the tricarboxylic acid (TCA) cycle, and increased aerobic glycolysis levels in heart tissue after short-term TCC exposure. TCC also inhibited the nuclear peroxisome proliferator-activated receptor α (PPARα), confirming its inhibitory effects on fatty acid uptake and oxidation. Histopathology and other analyses further confirm that TCC altered mouse cardiac physiology and pathology, ultimately affecting normal cardiac metabolic function. We elucidate the molecular mechanisms of TCC-induced harmful effects on mouse cardiac metabolism and function from a new perspective, using metabonomics and bioinformatics analysis data.

Dietary Deficiency of Essential Amino Acids Rapidly Induces Cessation of the Rat Estrous Cycle

PubMed Central

Bannai, Makoto; Ichimaru, Toru; Nakano, Sayako; Murata, Takuya; Higuchi, Takashi; Takahashi, Michio

2011-01-01

Reproductive functions are regulated by the sophisticated coordination between the neuronal and endocrine systems and are sustained by a proper nutritional environment. Female reproductive function is vulnerable to effects from dietary restrictions, suggesting a transient adaptation that prioritizes individual survival over reproduction until a possible future opportunity for satiation. This adaptation could also partially explain the existence of amenorrhea in women with anorexia nervosa. Because amino acid nutritional conditions other than caloric restriction uniquely alters amino acid metabolism and affect the hormonal levels of organisms, we hypothesized that the supply of essential amino acids in the diet plays a pivotal role in the maintenance of the female reproductive system. To test this hypothesis, we examined ovulatory cyclicity in female rats under diets that were deficient in threonine, lysine, tryptophan, methionine or valine. Ovulatory cyclicity was monitored by daily cytological evaluations of vaginal smears. After continuous feeding of the deficient diet, a persistent diestrus or anovulatory state was induced most quickly by the valine-deficient diet and most slowly by the lysine-deficient diet. A decline in the systemic insulin-like growth factor 1 level was associated with a dietary amino acid deficiency. Furthermore, a paired group of rats that were fed an isocaloric diet with balanced amino acids maintained normal estrous cyclicity. These disturbances of the estrous cycle by amino acid deficiency were quickly reversed by the consumption of a normal diet. The continuous anovulatory state in this study is not attributable to a decrease in caloric intake but to an imbalance in the dietary amino acid composition. With a shortage of well-balanced amino acid sources, reproduction becomes risky for both the mother and the fetus. It could be viewed as an adaptation to the diet, diverting resources away from reproduction and reallocating them to

Citric acid induces cell-cycle arrest and apoptosis of human immortalized keratinocyte cell line (HaCaT) via caspase- and mitochondrial-dependent signaling pathways.

PubMed

Ying, Tsung-Ho; Chen, Chia-Wei; Hsiao, Yu-Ping; Hung, Sung-Jen; Chung, Jing-Gung; Yang, Jen-Hung

2013-10-01

Citric acid is an alpha-hydroxyacid (AHA) widely used in cosmetic dermatology and skincare products. However, there is concern regarding its safety for the skin. In this study, we investigated the cytotoxic effects of citric acid on the human keratinocyte cell line HaCaT. HaCaT cells were treated with citric acid at 2.5-12.5 mM for different time periods. Cell-cycle arrest and apoptosis were investigated by 4,6-diamidino-2-phenylindole dihydrochloride (DAPI) staining, flow cytometry, western blot and confocal microscopy. Citric acid not only inhibited proliferation of HaCaT cells in a dose-dependent manner, but also induced apoptosis and cell cycle-arrest at the G2/M phase (before 24 h) and S phase (after 24 h). Citric acid increased the level of Bcl-2-associated X protein (BAX) and reduced the levels of B-cell lymphoma-2 (BCL-2), B-cell lymphoma-extra large (BCL-XL) and activated caspase-9 and caspase-3, which subsequently induced apoptosis via caspase-dependent and caspase-independent pathways. Citric acid also activated death receptors and increased the levels of caspase-8, activated BH3 interacting-domain death agonist (BID) protein, Apoptosis-inducing factor (AIF), and Endonuclease G (EndoG). Therefore, citric acid induces apoptosis through the mitochondrial pathway in the human keratinocyte cell line HaCaT. The study results suggest that citric acid is cytotoxic to HaCaT cells via induction of apoptosis and cell-cycle arrest in vitro.

Beta-oxidation as channeled reaction linked to citric acid cycle: evidence from measurements of mitochondrial pyruvate oxidation during fatty acid degradation.

PubMed

Förster, M E; Staib, W

1992-07-01

1. The kinetics of mitochondrial mammalian pyruvate dehydrogenase multienzyme complex (PDHC) is studied by the formation of CO2 using tracer amounts of [1-14C]pyruvate. It is found that the Hill plot results in a (pseudo-)cooperativity with a transition of n-1----3 at a pyruvate concentration about Ks. 2. Addition of L-carnitine, octanoate, palmitoyl-CoA or palmitate + L-carnitine + fatty acid-binding protein results in a Hill coefficient of n = 2 following the kinetics of pyruvate oxidation. 3. Addition of fatty acid-binding protein to an assay system oxidizing palmitate in presence of L-carnitine alters the pattern of the kinetics in the Hill plot so that an apparently lower level of L-carnitine is necessary for the reaction course of beta-degradation. 4. It is concluded that beta-degradation is a coordinated, multienzyme-complex based mechanism tightly linked to citric acid cycle and it is proposed that L-carnitine is actively involved into the reaction and not only functioning as carrier-molecule for transmembrane transport.

Flower abscission in Vitis vinifera L. triggered by gibberellic acid and shade discloses differences in the underlying metabolic pathways

PubMed Central

Domingos, Sara; Scafidi, Pietro; Cardoso, Vania; Leitao, Antonio E.; Di Lorenzo, Rosario; Oliveira, Cristina M.; Goulao, Luis F.

2015-01-01

Understanding abscission is both a biological and an agronomic challenge. Flower abscission induced independently by shade and gibberellic acid (GAc) sprays was monitored in grapevine (Vitis vinifera L.) growing under a soilless greenhouse system during two seasonal growing conditions, in an early and late production cycle. Physiological and metabolic changes triggered by each of the two distinct stimuli were determined. Environmental conditions exerted a significant effect on fruit set as showed by the higher natural drop rate recorded in the late production cycle with respect to the early cycle. Shade and GAc treatments increased the percentage of flower drop compared to the control, and at a similar degree, during the late production cycle. The reduction of leaf gas exchanges under shade conditions was not observed in GAc treated vines. The metabolic profile assessed in samples collected during the late cycle differently affected primary and secondary metabolisms and showed that most of the treatment-resulting variations occurred in opposite trends in inflorescences unbalanced in either hormonal or energy deficit abscission-inducing signals. Particularly concerning carbohydrates metabolism, sucrose, glucose, tricarboxylic acid metabolites and intermediates of the raffinose family oligosaccharides pathway were lower in shaded and higher in GAc samples. Altered oxidative stress remediation mechanisms and indolacetic acid (IAA) concentration were identified as abscission signatures common to both stimuli. According to the global analysis performed, we report that grape flower abscission mechanisms triggered by GAc application and C-starvation are not based on the same metabolic pathways. PMID:26157448

Deglacial Ocean Circulation Scheme at Intermediate Depths in the Tropical North Atlantic

NASA Astrophysics Data System (ADS)

Xie, R. C.; Marcantonio, F.; Schmidt, M. W.

2014-12-01

In the modern Atlantic Ocean, intermediate water circulation is largely governed by the southward flowing upper North Atlantic Deep Water (NADW) and the northward return flow Antarctic Intermediate Water (AAIW). During the last deglaciation, it is commonly accepted that the southward flow Glacial North Atlantic Intermediate Water, the glacial analogue of NADW, contributed significantly to past variations in intermediate water circulation. However, to date, there is no common consensus of the role AAIW played during the last deglaciation, especially across abrupt climate events such as the Heinrich 1 and the Younger Dryas. This study aims to reconstruct intermediate northern- and southern-sourced water circulation in the tropical North Atlantic during the past 22 kyr and attempts to confine the boundary between AAIW and northern-sourced intermediate waters in the past. High-resolution Nd isotopic compositions (ɛNd thereafter) of fish debris and bulk sediment acid-reductive leachate from the Southern Caribbean (VM12-107; 1079 m) are inconsistent, again casting concerns, as already raised by recent studies, on the reliability of the leachate method in extracting seawater ɛNd signature. This urges the need to carefully verify the seawater ɛNd integrity in sediment acid-reductive leachate in various oceanic settings. Fish debris Nd isotope record in our study displays a two-step decreasing trend from the early deglaciation to early Holocene. We interpret this as recording a two-step deglacial recovery of the upper NADW, given the assumption on a more radiogenic glacial northern-sourced water is valid. Comparing with authigenic ɛNd records in the Florida Straits [1] and the Demarara Rise [2], our new fish debris ɛNd results suggest that, in the tropical western North Atlantic, glacial and deglacial AAIW never penetrated beyond the lower depth limit of modern AAIW. [1] Xie et al., GCA (140) 2014; [2] Huang et al., EPSL (389) 2014

Succinic acid production from lignocellulosic hydrolysate by Basfia succiniciproducens

DOE PAGES

Salvachúa, Davinia; Smith, Holly; St. John, Peter C.; ...

2016-05-09

The production of chemicals alongside fuels will be essential to enhance the feasibility of lignocellulosic biorefineries. Succinic acid (SA), a naturally occurring C4-diacid, is a primary intermediate of the tricarboxylic acid cycle and a promising building block chemical that has received significant industrial attention. Basfia succiniciproducens is a relatively unexplored SA-producing bacterium with advantageous features such as broad substrate utilization, genetic tractability, and facultative anaerobic metabolism. Here B. succiniciproducens is evaluated in high xylose-content hydrolysates from corn stover and different synthetic media in batch fermentation. SA titers in hydrolysate at an initial sugar concentration of 60 g/L reached up tomore » 30 g/L, with metabolic yields of 0.69 g/g, and an overall productivity of 0.43 g/L/h. These results demonstrate that B. succiniciproducens may be an attractive platform organism for bio-SA production from biomass hydrolysates.« less

Sarcocystis jamaicensis, n. sp. from red-tailed hawks (Buteo jamaicensis) definitive host and IFN-Gamma gene knockout mice as experimental intermediate host

USDA-ARS?s Scientific Manuscript database

Sarcocystis species have 2-host life cycles with the sexual cycle in the definitive hosts and an asexual cycle in the intermediate hosts. The common buzzard (Buteo buteo) is the definitive host for 2 species of Sarcocystis; Sarcocystis (Frenkelia) microti (forms macroscopic, lobulated sarcocysts) an...

Detection of diastereomer peptides as the intermediates generating D-amino acids during acid hydrolysis of peptides.

PubMed

Miyamoto, Tetsuya; Sekine, Masae; Ogawa, Tetsuhiro; Hidaka, Makoto; Watanabe, Hidenori; Homma, Hiroshi; Masaki, Haruhiko

2016-11-01

In this study, we investigated whether the amino acid residues within peptides were isomerized (and the peptides converted to diastereomers) during the early stages of acid hydrolysis. We demonstrate that the model dipeptides L-Ala-L-Phe and L-Phe-L-Ala are epimerized to produce the corresponding diastereomers at a very early stage, prior to their acid hydrolytic cleavage to amino acids. Furthermore, the sequence-inverted dipeptides were generated via formation of a diketopiperazine during hydrolytic incubation, and these dipeptides were also epimerized. The proportion of diastereomers increased rapidly during incubation for 0.5-2 h. During acid hydrolysis, C-terminal residues of the model dipeptides were isomerized faster than N-terminal residues, consistent with the observation that the D-amino acid values of the C-terminal residues determined by the 0 h-extrapolating method were larger than those of the N-terminal residues. Thus, the artificial D-amino acid contents determined by the 0 h-extrapolating method appear to be products of the isomerization of amino acid residues during acid hydrolysis.

Helium process cycle

DOEpatents

Ganni, Venkatarao

2008-08-12

A unique process cycle and apparatus design separates the consumer (cryogenic) load return flow from most of the recycle return flow of a refrigerator and/or liquefier process cycle. The refrigerator and/or liquefier process recycle return flow is recompressed by a multi-stage compressor set and the consumer load return flow is recompressed by an independent consumer load compressor set that maintains a desirable constant suction pressure using a consumer load bypass control valve and the consumer load return pressure control valve that controls the consumer load compressor's suction pressure. The discharge pressure of this consumer load compressor is thereby allowed to float at the intermediate pressure in between the first and second stage recycle compressor sets. Utilizing the unique gas management valve regulation, the unique process cycle and apparatus design in which the consumer load return flow is separate from the recycle return flow, the pressure ratios of each recycle compressor stage and all main pressures associated with the recycle return flow are allowed to vary naturally, thus providing a naturally regulated and balanced floating pressure process cycle that maintains optimal efficiency at design and off-design process cycle capacity and conditions automatically.

Helium process cycle

DOEpatents

Ganni, Venkatarao

2007-10-09

A unique process cycle and apparatus design separates the consumer (cryogenic) load return flow from most of the recycle return flow of a refrigerator and/or liquefier process cycle. The refrigerator and/or liquefier process recycle return flow is recompressed by a multi-stage compressor set and the consumer load return flow is recompressed by an independent consumer load compressor set that maintains a desirable constant suction pressure using a consumer load bypass control valve and the consumer load return pressure control valve that controls the consumer load compressor's suction pressure. The discharge pressure of this consumer load compressor is thereby allowed to float at the intermediate pressure in between the first and second stage recycle compressor sets. Utilizing the unique gas management valve regulation, the unique process cycle and apparatus design in which the consumer load return flow is separate from the recycle return flow, the pressure ratios of each recycle compressor stage and all main pressures associated with the recycle return flow are allowed to vary naturally, thus providing a naturally regulated and balanced floating pressure process cycle that maintains optimal efficiency at design and off-design process cycle capacity and conditions automatically.

A Critical Review on the Effect of Docosahexaenoic Acid (DHA) on Cancer Cell Cycle Progression.

PubMed

Newell, Marnie; Baker, Kristi; Postovit, Lynne M; Field, Catherine J

2017-08-17

Globally, there were 14.1 million new cancer diagnoses and 8.2 million cancer deaths in 2012. For many cancers, conventional therapies are limited in their successes and an improved understanding of disease progression is needed in conjunction with exploration of alternative therapies. The long chain polyunsaturated fatty acid, docosahexaenoic acid (DHA), has been shown to enhance many cellular responses that reduce cancer cell viability and decrease proliferation both in vitro and in vivo. A small number of studies suggest that DHA improves chemotherapy outcomes in cancer patients. It is readily incorporated into cancer cell membranes and, as a result there has been considerable research regarding cell membrane initiated events. For example, DHA has been shown to mediate the induction of apoptosis/reduction of proliferation in vitro and in vivo. However, there is limited research into the effect of DHA on cell cycle regulation in cancer cells and the mechanism(s) by which DHA acts are not fully understood. The purpose of the current review is to provide a critical examination of the literature investigating the ability of DHA to stall progression during different cell cycle phases in cancer cells, as well as the consequences that these changes may have on tumour growth, independently and in conjunction with chemotherapy.

Copper-zinc superoxide dismutase is activated through a sulfenic acid intermediate at a copper ion entry site.

PubMed

Fetherolf, Morgan M; Boyd, Stefanie D; Taylor, Alexander B; Kim, Hee Jong; Wohlschlegel, James A; Blackburn, Ninian J; Hart, P John; Winge, Dennis R; Winkler, Duane D

2017-07-21

Metallochaperones are a diverse family of trafficking molecules that provide metal ions to protein targets for use as cofactors. The copper chaperone for superoxide dismutase (Ccs1) activates immature copper-zinc superoxide dismutase (Sod1) by delivering copper and facilitating the oxidation of the Sod1 intramolecular disulfide bond. Here, we present structural, spectroscopic, and cell-based data supporting a novel copper-induced mechanism for Sod1 activation. Ccs1 binding exposes an electropositive cavity and proposed "entry site" for copper ion delivery on immature Sod1. Copper-mediated sulfenylation leads to a sulfenic acid intermediate that eventually resolves to form the Sod1 disulfide bond with concomitant release of copper into the Sod1 active site. Sod1 is the predominant disulfide bond-requiring enzyme in the cytoplasm, and this copper-induced mechanism of disulfide bond formation obviates the need for a thiol/disulfide oxidoreductase in that compartment. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

An Oral Load of [13C3]Glycerol and Blood NMR Analysis Detect Fatty Acid Esterification, Pentose Phosphate Pathway, and Glycerol Metabolism through the Tricarboxylic Acid Cycle in Human Liver.

PubMed

Jin, Eunsook S; Sherry, A Dean; Malloy, Craig R

2016-09-02

Drugs and other interventions for high impact hepatic diseases often target biochemical pathways such as gluconeogenesis, lipogenesis, or the metabolic response to oxidative stress. However, traditional liver function tests do not provide quantitative data about these pathways. In this study, we developed a simple method to evaluate these processes by NMR analysis of plasma metabolites. Healthy subjects ingested [U-(13)C3]glycerol, and blood was drawn at multiple times. Each subject completed three visits under differing nutritional states. High resolution (13)C NMR spectra of plasma triacylglycerols and glucose provided new insights into a number of hepatic processes including fatty acid esterification, the pentose phosphate pathway, and gluconeogenesis through the tricarboxylic acid cycle. Fasting stimulated pentose phosphate pathway activity and metabolism of [U-(13)C3]glycerol in the tricarboxylic acid cycle prior to gluconeogenesis or glyceroneogenesis. Fatty acid esterification was transient in the fasted state but continuous under fed conditions. We conclude that a simple NMR analysis of blood metabolites provides an important biomarker of pentose phosphate pathway activity, triacylglycerol synthesis, and flux through anaplerotic pathways in mitochondria of human liver. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

Plasma acylcarnitine profiling indicates increased fatty acid oxidation relative to tricarboxylic acid cycle capacity in young, healthy low birth weight men.

PubMed

Ribel-Madsen, Amalie; Ribel-Madsen, Rasmus; Brøns, Charlotte; Newgard, Christopher B; Vaag, Allan A; Hellgren, Lars I

2016-10-01

We hypothesized that an increased, incomplete fatty acid beta-oxidation in mitochondria could be part of the metabolic events leading to insulin resistance and thereby an increased type 2 diabetes risk in low birth weight (LBW) compared with normal birth weight (NBW) individuals. Therefore, we measured fasting plasma levels of 45 acylcarnitine species in 18 LBW and 25 NBW men after an isocaloric control diet and a 5-day high-fat, high-calorie diet. We demonstrated that LBW men had higher C2 and C4-OH levels after the control diet compared with NBW men, indicating an increased fatty acid beta-oxidation relative to the tricarboxylic acid cycle flux. Also, they had higher C6-DC, C10-OH/C8-DC, and total hydroxyl-/dicarboxyl-acylcarnitine levels, which may suggest an increased fatty acid omega-oxidation in the liver. Furthermore, LBW and NBW men decreased several acylcarnitine levels in response to overfeeding, which is likely a result of an upregulation of fatty acid oxidation due to the dietary challenge. Moreover, C10-OH/C8-DC and total hydroxyl-/dicarboxyl-acylcarnitine levels tended to be negatively associated with the serum insulin level, and the total hydroxyl-/dicarboxyl-acylcarnitine level additionally tended to be negatively associated with the hepatic insulin resistance index. This indicates that an increased fatty acid omega-oxidation could be a compensatory mechanism to prevent an accumulation of lipid species that impair insulin signaling. © 2016 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of the American Physiological Society and The Physiological Society.

Diffusion of tricarboxylic acid cycle enzymes in the mitochondrial matrix in vivo. Evidence for restricted mobility of a multienzyme complex.

PubMed

Haggie, Peter M; Verkman, A S

2002-10-25

It has been proposed that enzymes in many metabolic pathways, including the tricarboxylic acid cycle in the mitochondrial matrix, are physically associated to facilitate substrate channeling and overcome diffusive barriers. We have used fluorescence recovery after photobleaching to measure the diffusional mobilities of chimeras consisting of green fluorescent protein (GFP) fused to the C terminus of four tricarboxylic acid cycle enzymes: malate dehydrogenase, citrate synthase, isocitrate dehydrogenase, and succinyl-CoA synthetase. The GFP-enzyme chimeras were localized selectively in the mitochondrial matrix in transfected Chinese hamster ovary (CHO) and COS7 cells. Laser photobleaching using a 0.7-microm diameter spot demonstrated restricted diffusion of the GFP-enzyme chimeras. Interestingly, all four chimeras had similar diffusional characteristics, approximately 45% of each chimera was mobile and had a diffusion coefficient of 4 x 10(-8) cm(2)/s. In contrast, unconjugated GFP in the mitochondrial matrix (targeted using COX8 leader sequence) diffused freely (nearly 100% mobility) with a greater diffusion coefficient of 20 x 10(-8) cm(2)/s. The mobility of the GFP-enzyme chimeras was insensitive to substrate source, ATP depletion, or inhibition of the adenine nucleotide translocase. These results indicate similar mobility characteristics of unrelated tricarboxylic acid cycle enzymes having different sizes and physical properties, providing biophysical evidence for a diffusible multienzyme complex in the mitochondrial matrix.

Open-Cycle Gas Turbine/Steam Turbine Combined Cycles with synthetic fuels from coal

NASA Technical Reports Server (NTRS)

Shah, R. P.; Corman, J. C.

1977-01-01

The Open-Cycle Gas Turbine/Steam Turbine Combined Cycle can be an effective energy conversion system for converting coal to electricity. The intermediate step in this energy conversion process is to convert the coal into a fuel acceptable to a gas turbine. This can be accomplished by producing a synthetic gas or liquid, and by removing, in the fuel conversion step, the elements in the fuel that would be harmful to the environment if combusted. In this paper, two open-cycle gas turbine combined systems are evaluated: one employing an integrated low-Btu gasifier, and one utilizing a semi-clean liquid fuel. A consistent technical/economic information base is developed for these two systems, and is compared with a reference steam plant burning coal directly in a conventional furnace.

Organic intermediates in the anaerobic biodegradation of coal to methane under laboratory conditions

USGS Publications Warehouse

Orem, William H.; Voytek, Mary A.; Jones, Elizabeth J.; Lerch, Harry E.; Bates, Anne L.; Corum, Margo D.; Warwick, Peter D.; Clark, Arthur C.

2010-01-01

Organic intermediates in coal fluids produced by anaerobic biodegradation of geopolymers in coal play a key role in the production of methane in natural gas reservoirs. Laboratory biodegradation experiments on sub-bituminous coal from Texas, USA, were conducted using bioreactors to examine the organic intermediates relevant to methane production. Production of methane in the bioreactors was linked to acetate accumulation in bioreactor fluid. Long chain fatty acids, alkanes (C19–C36) and various low molecular weight aromatics, including phenols, also accumulated in the bioreactor fluid and appear to be the primary intermediates in the biodegradation pathway from coal-derived geopolymers to acetate and methane.

Metabolic Engineering of Actinobacillus succinogenes Provides Insights into Succinic Acid Biosynthesis

PubMed Central

Guarnieri, Michael T.; Chou, Yat-Chen; Salvachúa, Davinia; Mohagheghi, Ali; St. John, Peter C.; Peterson, Darren J.; Bomble, Yannick J.

2017-01-01

ABSTRACT Actinobacillus succinogenes, a Gram-negative facultative anaerobe, exhibits the native capacity to convert pentose and hexose sugars to succinic acid (SA) with high yield as a tricarboxylic acid (TCA) cycle intermediate. In addition, A. succinogenes is capnophilic, incorporating CO2 into SA, making this organism an ideal candidate host for conversion of lignocellulosic sugars and CO2 to an emerging commodity bioproduct sourced from renewable feedstocks. In this work, we report the development of facile metabolic engineering capabilities in A. succinogenes, enabling examination of SA flux determinants via knockout of the primary competing pathways—namely, acetate and formate production—and overexpression of the key enzymes in the reductive branch of the TCA cycle leading to SA. Batch fermentation experiments with the wild-type and engineered strains using pentose-rich sugar streams demonstrate that the overexpression of the SA biosynthetic machinery (in particular, the enzyme malate dehydrogenase) enhances flux to SA. Additionally, removal of competitive carbon pathways leads to higher-purity SA but also triggers the generation of by-products not previously described from this organism (e.g., lactic acid). The resultant engineered strains also lend insight into energetic and redox balance and elucidate mechanisms governing organic acid biosynthesis in this important natural SA-producing microbe. IMPORTANCE Succinic acid production from lignocellulosic residues is a potential route for enhancing the economic feasibility of modern biorefineries. Here, we employ facile genetic tools to systematically manipulate competing acid production pathways and overexpress the succinic acid-producing machinery in Actinobacillus succinogenes. Furthermore, the resulting strains are evaluated via fermentation on relevant pentose-rich sugar streams representative of those from corn stover. Overall, this work demonstrates genetic modifications that can lead to succinic

Metabolic Engineering of Actinobacillus succinogenes Provides Insights into Succinic Acid Biosynthesis.

PubMed

Guarnieri, Michael T; Chou, Yat-Chen; Salvachúa, Davinia; Mohagheghi, Ali; St John, Peter C; Peterson, Darren J; Bomble, Yannick J; Beckham, Gregg T

2017-09-01

Actinobacillus succinogenes , a Gram-negative facultative anaerobe, exhibits the native capacity to convert pentose and hexose sugars to succinic acid (SA) with high yield as a tricarboxylic acid (TCA) cycle intermediate. In addition, A. succinogenes is capnophilic, incorporating CO 2 into SA, making this organism an ideal candidate host for conversion of lignocellulosic sugars and CO 2 to an emerging commodity bioproduct sourced from renewable feedstocks. In this work, we report the development of facile metabolic engineering capabilities in A. succinogenes , enabling examination of SA flux determinants via knockout of the primary competing pathways-namely, acetate and formate production-and overexpression of the key enzymes in the reductive branch of the TCA cycle leading to SA. Batch fermentation experiments with the wild-type and engineered strains using pentose-rich sugar streams demonstrate that the overexpression of the SA biosynthetic machinery (in particular, the enzyme malate dehydrogenase) enhances flux to SA. Additionally, removal of competitive carbon pathways leads to higher-purity SA but also triggers the generation of by-products not previously described from this organism (e.g., lactic acid). The resultant engineered strains also lend insight into energetic and redox balance and elucidate mechanisms governing organic acid biosynthesis in this important natural SA-producing microbe. IMPORTANCE Succinic acid production from lignocellulosic residues is a potential route for enhancing the economic feasibility of modern biorefineries. Here, we employ facile genetic tools to systematically manipulate competing acid production pathways and overexpress the succinic acid-producing machinery in Actinobacillus succinogenes Furthermore, the resulting strains are evaluated via fermentation on relevant pentose-rich sugar streams representative of those from corn stover. Overall, this work demonstrates genetic modifications that can lead to succinic acid

Metabolic Engineering of Actinobacillus succinogenes Provides Insights into Succinic Acid Biosynthesis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guarnieri, Michael T.; Chou, Yat -Chen; Salvachua, Davinia Rodriquez

Actinobacillus succinogenes, a Gram-negative facultative anaerobe, exhibits the native capacity to convert pentose and hexose sugars to succinic acid (SA) with high yield as a tricarboxylic acid (TCA) cycle intermediate. In addition, A. succinogenes is capnophilic, incorporating CO 2 into SA, making this organism an ideal candidate host for conversion of lignocellulosic sugars and CO 2 to an emerging commodity bioproduct sourced from renewable feedstocks. In this work, we report the development of facile metabolic engineering capabilities in A. succinogenes, enabling examination of SA flux determinants via knockout of the primary competing pathways—namely, acetate and formate production—and overexpression of themore » key enzymes in the reductive branch of the TCA cycle leading to SA. Batch fermentation experiments with the wild-type and engineered strains using pentose-rich sugar streams demonstrate that the overexpression of the SA biosynthetic machinery (in particular, the enzyme malate dehydrogenase) enhances flux to SA. Additionally, removal of competitive carbon pathways leads to higher-purity SA but also triggers the generation of by-products not previously described from this organism (e.g., lactic acid). The resultant engineered strains also lend insight into energetic and redox balance and elucidate mechanisms governing organic acid biosynthesis in this important natural SA-producing microbe. IMPORTANCE Succinic acid production from lignocellulosic residues is a potential route for enhancing the economic feasibility of modern biorefineries. Here, we employ facile genetic tools to systematically manipulate competing acid production pathways and overexpress the succinic acid-producing machinery in Actinobacillus succinogenes. Furthermore, the resulting strains are evaluated via fermentation on relevant pentose-rich sugar streams representative of those from corn stover. Altogether, this work demonstrates genetic modifications that can lead to succinic

Metabolic Engineering of Actinobacillus succinogenes Provides Insights into Succinic Acid Biosynthesis

DOE PAGES

Guarnieri, Michael T.; Chou, Yat -Chen; Salvachua, Davinia Rodriquez; ...

2017-06-16

Actinobacillus succinogenes, a Gram-negative facultative anaerobe, exhibits the native capacity to convert pentose and hexose sugars to succinic acid (SA) with high yield as a tricarboxylic acid (TCA) cycle intermediate. In addition, A. succinogenes is capnophilic, incorporating CO 2 into SA, making this organism an ideal candidate host for conversion of lignocellulosic sugars and CO 2 to an emerging commodity bioproduct sourced from renewable feedstocks. In this work, we report the development of facile metabolic engineering capabilities in A. succinogenes, enabling examination of SA flux determinants via knockout of the primary competing pathways—namely, acetate and formate production—and overexpression of themore » key enzymes in the reductive branch of the TCA cycle leading to SA. Batch fermentation experiments with the wild-type and engineered strains using pentose-rich sugar streams demonstrate that the overexpression of the SA biosynthetic machinery (in particular, the enzyme malate dehydrogenase) enhances flux to SA. Additionally, removal of competitive carbon pathways leads to higher-purity SA but also triggers the generation of by-products not previously described from this organism (e.g., lactic acid). The resultant engineered strains also lend insight into energetic and redox balance and elucidate mechanisms governing organic acid biosynthesis in this important natural SA-producing microbe. IMPORTANCE Succinic acid production from lignocellulosic residues is a potential route for enhancing the economic feasibility of modern biorefineries. Here, we employ facile genetic tools to systematically manipulate competing acid production pathways and overexpress the succinic acid-producing machinery in Actinobacillus succinogenes. Furthermore, the resulting strains are evaluated via fermentation on relevant pentose-rich sugar streams representative of those from corn stover. Altogether, this work demonstrates genetic modifications that can lead to succinic

Chemotherapy of colorectal liver metastases induces a rapid rise in intermediate blood monocytes which predicts treatment response

PubMed Central

Schauer, Dominic; Starlinger, Patrick; Alidzanovic, Lejla; Zajc, Philipp; Maier, Thomas; Feldman, Alexandra; Padickakudy, Robin; Buchberger, Elisabeth; Elleder, Vanessa; Spittler, Andreas; Stift, Judith; Pop, Lorand; Gruenberger, Birgit; Gruenberger, Thomas; Brostjan, Christine

2016-01-01

ABSTRACT We have previously reported that intermediate monocytes (CD14++/CD16+) were increased in colorectal cancer (CRC) patients, while the subset of pro-angiogenic TIE2-expressing monocytes (TEMs) was not significantly elevated. This study was designed to evaluate changes in frequency and function of intermediate monocytes and TEMs during chemotherapy and anti-angiogenic cancer treatment and their relation to treatment response. Monocyte populations were determined by flow cytometry in 60 metastasized CRC (mCRC) patients who received neoadjuvant chemotherapy with or without bevacizumab. Blood samples were taken before treatment, after two therapy cycles, at the end of neoadjuvant therapy and immediately before surgical resection of liver metastases. Neoadjuvant treatment resulted in a significant increase in circulating intermediate monocytes which was most pronounced after two cycles and positively predicted tumor response (AUC = 0.875, p = 0.005). With a cut-off value set to 1% intermediate monocytes of leukocytes, this parameter showed a predictive sensitivity and specificity of 75% and 88%. Anti-angiogenic therapy with bevacizumab had no impact on monocyte populations including TEMs. In 15 patients and six healthy controls, the gene expression profile and the migratory behavior of monocyte subsets was evaluated. The profile of intermediate monocytes suggested functions in antigen presentation, inflammatory cytokine production, chemotaxis and was remarkably stable during chemotherapy. Intermediate monocytes showed a preferential migratory response to tumor-derived signals in vitro and correlated with the level of CD14+/CD16+ monocytic infiltrates in the resected tumor tissue. In conclusion, the rapid rise of intermediate monocytes during chemotherapy may offer a simple marker for response prediction and a timely change in regimen. PMID:27471631

Life cycle, techno-economic and dynamic simulation assessment of bioelectrochemical systems: A case of formic acid synthesis.

PubMed

Shemfe, Mobolaji; Gadkari, Siddharth; Yu, Eileen; Rasul, Shahid; Scott, Keith; Head, Ian M; Gu, Sai; Sadhukhan, Jhuma

2018-05-01

A novel framework, integrating dynamic simulation (DS), life cycle assessment (LCA) and techno-economic assessment (TEA) of a bioelectrochemical system (BES), has been developed to study for the first time wastewater treatment by removal of chemical oxygen demand (COD) by oxidation in anode and thereby harvesting electron and proton for carbon dioxide reduction reaction or reuse to produce products in cathode. Increases in initial COD and applied potential increase COD removal and production (in this case formic acid) rates. DS correlations are used in LCA and TEA for holistic performance analyses. The cost of production of HCOOH is €0.015-0.005 g -1 for its production rate of 0.094-0.26 kg yr -1 and a COD removal rate of 0.038-0.106 kg yr -1 . The life cycle (LC) benefits by avoiding fossil-based formic acid production (93%) and electricity for wastewater treatment (12%) outweigh LC costs of operation and assemblage of BES (-5%), giving a net 61MJkg -1 HCOOH saving. Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.

Beta cell compensation for insulin resistance in Zucker fatty rats: increased lipolysis and fatty acid signalling.

PubMed

Nolan, C J; Leahy, J L; Delghingaro-Augusto, V; Moibi, J; Soni, K; Peyot, M-L; Fortier, M; Guay, C; Lamontagne, J; Barbeau, A; Przybytkowski, E; Joly, E; Masiello, P; Wang, S; Mitchell, G A; Prentki, M

2006-09-01

The aim of this study was to determine the role of fatty acid signalling in islet beta cell compensation for insulin resistance in the Zucker fatty fa/fa (ZF) rat, a genetic model of severe obesity, hyperlipidaemia and insulin resistance that does not develop diabetes. NEFA augmentation of insulin secretion and fatty acid metabolism were studied in isolated islets from ZF and Zucker lean (ZL) control rats. Exogenous palmitate markedly potentiated glucose-stimulated insulin secretion (GSIS) in ZF islets, allowing robust secretion at physiological glucose levels (5-8 mmol/l). Exogenous palmitate also synergised with glucagon-like peptide-1 and the cyclic AMP-raising agent forskolin to enhance GSIS in ZF islets only. In assessing islet fatty acid metabolism, we found increased glucose-responsive palmitate esterification and lipolysis processes in ZF islets, suggestive of enhanced triglyceride-fatty acid cycling. Interruption of glucose-stimulated lipolysis by the lipase inhibitor Orlistat (tetrahydrolipstatin) blunted palmitate-augmented GSIS in ZF islets. Fatty acid oxidation was also higher at intermediate glucose levels in ZF islets and steatotic triglyceride accumulation was absent. The results highlight the potential importance of NEFA and glucoincretin enhancement of insulin secretion in beta cell compensation for insulin resistance. We propose that coordinated glucose-responsive fatty acid esterification and lipolysis processes, suggestive of triglyceride-fatty acid cycling, play a role in the coupling mechanisms of glucose-induced insulin secretion as well as in beta cell compensation and the hypersecretion of insulin in obesity.

γ-Dodecelactone production from safflower oil via 10-hydroxy-12(Z)-octadecenoic acid intermediate by whole cells of Candida boidinii and Stenotrophomonas nitritireducens.

PubMed

Jo, Ye-Seul; An, Jung-Ung; Oh, Deok-Kun

2014-07-16

Candida boidinii was selected as a γ-dodecelactone producer because of the highest production of γ-dodecelactone from 10-hydroxy-12(Z)-octadecenoic acid among the 11 yeast strains tested. Under the reaction conditions of pH 5.5 and 25 °C with 5 g/L 10-hydroxy-12(Z)-octadecenoic acid and 30 g/L cells, whole C. boidinii cells produced 2.1 g/L γ-dodecelactone from 5 g/L 10-hydroxy-12(Z)-octadecenoic acid after 6 h, with a conversion yield of 64% (mol/mol) and a volumetric productivity of 350 mg/L/h. The production of γ-dodecelactone from safflower oil was performed by lipase hydrolysis reaction and two-step whole-cell biotransformation using Stenotrophomonas nitritireducens and C. boidinii. γ-Dodecelactone at 1.88 g/L was produced from 7.5 g/L safflower oil via 5 g/L 10-hydroxy-12(Z)-octadecenoic acid intermediate by these reactions after 8 h of reaction time, with a volumetric productivity of 235 mg/L/h and a conversion yield of 25% (w/w). To the best of the authors' knowledge, this is the highest volumetric productivity and conversion yield reported to date for the production of γ-lactone from natural oils.

Structure, bonding, and reactivity of reactant complexes and key intermediates.

PubMed

Soriano, Elena; Marco-Contelles, José

2011-01-01

Complexes of Pt and Au (gold(III) and cationic gold(I)) have shown an exceptional ability to promote a variety of organic transformations of unsaturated precursors due to their peculiar Lewis acid properties: the alkynophilic character of these soft metals and the π-acid activation of unsaturated groups promotes the intra- or intermolecular attack of a nucleophile. In this chapter we summarize the computational data reported on the structure, bonding, and reactivity of the reactant π-complexes and also on the key intermediate species.

Cell cycle arrest and induction of apoptosis by cajanin stilbene acid from Cajanus cajan in breast cancer cells.

PubMed

Fu, Yujie; Kadioglu, Onat; Wiench, Benjamin; Wei, Zuofu; Gao, Chang; Luo, Meng; Gu, Chengbo; Zu, Yuangang; Efferth, Thomas

2015-04-15

The low abundant cajanin stilbene acid (CSA) from Pigeon Pea (Cajanus cajan) has been shown to kill estrogen receptor α positive cancer cells in vitro and in vivo. Downstream effects such as cell cycle and apoptosis-related mechanisms have not been analyzed yet. We analyzed the activity of CSA by means of flow cytometry (cell cycle distribution, mitochondrial membrane potential, MMP), confocal laser scanning microscopy (MMP), DNA fragmentation assay (apoptosis), Western blotting (Bax and Bcl-2 expression, caspase-3 activation) as well as mRNA microarray hybridization and Ingenuity pathway analysis. CSA induced G2/M arrest and apoptosis in a concentration-dependent manner from 8.88 to 14.79 µM. The MMP broke down, Bax was upregulated, Bcl-2 downregulated and caspase-3 activated. Microarray profiling revealed that CSA affected BRCA-related DNA damage response and cell cycle-regulated chromosomal replication pathways. CSA inhibited breast cancer cells by DNA damage and cell cycle-related signaling pathways leading to cell cycle arrest and apoptosis. Copyright © 2015 Elsevier GmbH. All rights reserved.

The photochemical cycle of bacteriorhodopsin

NASA Technical Reports Server (NTRS)

Lozier, R. H.; Niederberger, W.

1977-01-01

The reaction cycle of bacteriorhodopsin in the purple membrane isolated from Halobacterium halobium has been studied by optical absorption spectroscopy using low-temperature and flash kinetic techniques. After absorption of light, bacteriorhodopsin passes through at least five distinct intermediates. The temperature and pH dependence of the absorbance changes suggests that branch points and/or reversible steps exist in this cycle. Flash spectroscopy in the presence of a pH-indicating dye shows that the transient release of a proton accompanies the photoreaction cycle. The proton release occurs from the exterior and the uptake is on the cytoplasmic side of the membrane, as required by the function of bacteriorhodopsin as a light-driven proton pump. Proton translocating steps connecting release and uptake are indicated by deuterium isotope effects on the kinetics of the cycle. The rapid decay of a light-induced linear dichroism shows that a chromophore orientation change occurs during the reaction cycle.

Resin-dentin bonds to EDTA-treated vs. acid-etched dentin using ethanol wet-bonding. Part II: Effects of mechanical cycling load on microtensile bond strengths.

PubMed

Sauro, Salvatore; Toledano, Manuel; Aguilera, Fatima Sánchez; Mannocci, Francesco; Pashley, David H; Tay, Franklin R; Watson, Timothy F; Osorio, Raquel

2011-06-01

To compare microtensile bond strengths (MTBS) subsequent to load cycling of resin bonded acid-etched or EDTA-treated dentin using a modified ethanol wet-bonding technique. Flat dentin surfaces were obtained from extracted human molars and conditioned using 37% H(3)PO(4) (PA) (15s) or 0.1M EDTA (60s). Five experimental adhesives and one commercial bonding agent were applied to the dentin and light-cured. Solvated experimental resins (50% ethanol/50% comonomers) were used as primers and their respective neat resins were used as the adhesives. The resin-bonded teeth were stored in distilled water (24h) or submitted to 5000 loading cycles of 90N. The bonded teeth were then sectioned in beams for MTBS. Modes of failure were examined by scanning electron microscopy. The most hydrophobic resin 1 gave the lowest bond strength values to both acid and EDTA-treated dentin. The hydrophobic resin 2 applied to EDTA-treated dentin showed lower bond strengths after cycling load but this did not occur when it was bonded to PA-etched dentin. Resins 3 and 4, which contained hydrophilic monomers, gave higher bond strengths to both EDTA-treated or acid-etched dentin and showed no significant difference after load cycling. The most hydrophilic resin 5 showed no significant difference in bond strengths after cycling loading when bonded to EDTA or phosphoric acid treated dentin but exhibited low bond strengths. The presence of different functional monomers influences the MTBS of the adhesive systems when submitted to cyclic loads. Adhesives containing hydrophilic comonomers are not affected by cycling load challenge especially when applied on EDTA-treated dentin followed by ethanol wet bonding. Copyright © 2011 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Photodegradation of lambda-cyhalothrin and cypermethrin in aqueous solution as affected by humic acid and/or copper: intermediates and degradation pathways.

PubMed

Xie, Jimin; Wang, Pingli; Liu, Jun; Lv, Xiaomeng; Jiang, Deli; Sun, Cheng

2011-11-01

The influence of coexisting humic acids (HA) or Cu²⁺ on the photodegradation of pesticides lambda-cyhalothrin (λ-CHT) and cypermethrin (CPM) in aqueous solution was studied under xenon lamp irradiation. The removal efficiency of pesticides λ-CHT and CPM were enhanced in the presence of either Cu²⁺ or HA but restrained in the presence of both Cu²⁺ and HA. The photodegradation of λ-CHT and CPM followed first-order reaction kinetics. The photodegradation intermediates of λ-CHT and CPM were determined using gas chromatography/mass spectrometry. Possible photodegradation pathways included decarboxylation, ester bond cleavage, dechlorination, and phenyl group removal. Copyright © 2011 SETAC.

Ultrasonic-assisted continuous methanolysis of Jatropha curcas oil in the appearance of biodiesel used as an intermediate solvent.

PubMed

Kumar, Gajendra; Singh, Vidhi; Kumar, Dharmendra

2017-11-01

A environmental friendly system for fast transesterification of Jatropha curcas oil was developed for the production of biodiesel using an ultrasonic-assisted continuous tank reactor in the presence of fatty acid methyl ester (FAMEs) used as a green (intermediate) solvent with potassium hydroxide used as a catalyst. This research provide a new biodiesel production process, the optimal condition for the reaction were established: reaction temperature 25°C oil to methanol molar ratio was 1:5, catalyst concentration 0.75wt% of oil, solvent concentration 7.5%, flow rate 241.68±0.80ml/min, ultrasonic amplitude 60% and ultrasonic cycles 0.7s, transesterification was completed within 1.09min (residence time). The purity and conversion of biodiesel was 98.75±0.50% analyzed by the reverse phase HPLC method. Copyright © 2017 Elsevier B.V. All rights reserved.

Evidence for Formation of a Radical-Mediated Flavin-N5 Covalent Intermediate.

PubMed

Dai, Yumin; Valentino, Hannah R; Sobrado, Pablo

2018-05-18

The redox-neutral reaction catalyzed by 2-haloacrylate hydratase (2-HAH) leads to the conversion of 2-chloroacrylate to pyruvate. Previous mechanistic studies demonstrated formation of a flavin-iminium ion as an important intermediate in the 2-HAH catalytic cycle. Time-resolved flavin absorbance studies were performed in this study and the data showed that the enzyme is capable of stabilizing both anionic and neutral flavin semiquinone species. The presence of a radical scavenger decreases the activity in a concentration-dependent manner. These data are consistent with the flavin iminium intermediate occurring via radical recombination. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The evolution of complex life cycles when parasite mortality is size- or time-dependent.

PubMed

Ball, M A; Parker, G A; Chubb, J C

2008-07-07

In complex cycles, helminth larvae in their intermediate hosts typically grow to a fixed size. We define this cessation of growth before transmission to the next host as growth arrest at larval maturity (GALM). Where the larval parasite controls its own growth in the intermediate host, in order that growth eventually arrests, some form of size- or time-dependent increase in its death rate must apply. In contrast, the switch from growth to sexual reproduction in the definitive host can be regulated by constant (time-independent) mortality as in standard life history theory. We here develop a step-wise model for the evolution of complex helminth life cycles through trophic transmission, based on the approach of Parker et al. [2003a. Evolution of complex life cycles in helminth parasites. Nature London 425, 480-484], but which includes size- or time-dependent increase in mortality rate. We assume that the growing larval parasite has two components to its death rate: (i) a constant, size- or time-independent component, and (ii) a component that increases with size or time in the intermediate host. When growth stops at larval maturity, there is a discontinuous change in mortality to a constant (time-independent) rate. This model generates the same optimal size for the parasite larva at GALM in the intermediate host whether the evolutionary approach to the complex life cycle is by adding a new host above the original definitive host (upward incorporation), or below the original definitive host (downward incorporation). We discuss some unexplored problems for cases where complex life cycles evolve through trophic transmission.

Study on the reactive transient α-λ3-iodanyl-acetophenone complex in the iodine(III)/PhI(I) catalytic cycle of iodobenzene-catalyzed α-acetoxylation reaction of acetophenone by electrospray ionization tandem mass spectrometry.

PubMed

Wang, Hao-Yang; Zhou, Juan; Guo, Yin-Long

2012-03-30

Hypervalent iodine compounds are important and widely used oxidants in organic chemistry. In 2005, Ochiai reported the PhI-catalyzed α-acetoxylation reaction of acetophenone by the oxidation of PhI with m-chloroperbenzoic acid (m-CPBA) in acetic acid. However, until now, the most critical reactive α-λ(3)-iodine alkyl acetophenone intermediate (3) had not been isolated or directly detected. Electrospray ionization tandem mass spectrometry (ESI-MS/MS) was used to intercept and characterize the transient reactive α-λ(3)-iodine alkyl acetophenone intermediate in the reaction solution. The trivalent iodine species was detected when PhI and m-CPBA in acetic acid were mixed, which indicated the facile oxidation of a catalytic amount of PhI(I) to the iodine(III) species by m-CPBA. Most importantly, 3·H(+) was observed at m/z 383 from the reaction solution and this ion gave the protonated α-acetoxylation product 4·H(+) at m/z 179 in MS/MS by an intramolecular reductive elimination of PhI. These ESI-MS/MS studies showed the existence of the reactive α-λ(3)-iodine alkyl acetophenone intermediate 3 in the catalytic cycle. Moreover, the gas-phase reactivity of 3·H(+) was consistent with the proposed solution-phase reactivity of the α-λ(3)-iodine alkyl acetophenone intermediate 3, thus confirming the reaction mechanism proposed by Ochiai. Copyright © 2012 John Wiley & Sons, Ltd.

Photochemical cycle of bacteriorhodopsin studied by resonance Raman spectroscopy.

PubMed

Stockburger, M; Klusmann, W; Gattermann, H; Massig, G; Peters, R

1979-10-30

Individual species of the photochemical cycle of bacteriorhodopsin, a retinal-protein complex of Halobacteria, were studied in aqueous suspensions of the "purple membrane" at room temperature by resonance Raman (RR) spectroscopy with flow systems. Two pronounced deuterium shifts were found in the RR spectra of the all-trans complex BR-570 in H2O-D2O suspensions. The first is ascribed to C=NH+ (C=ND+) stretching vibrations of the protonated Schiff base which links retinal to opsin. The second is assigned tentatively to an "X-H" ("X-D") bending mode, where "X" is an atom which carries an exchangeable proton. A RR spectrum of the 13-cis-retinal complex "BR-548" could be deduced from spectra of the dark-adapted purple membrane. The RR spectrum of the M-412 intermediate was monitored in a double-beam pump-probe experiment. The main vibrational features of the intermediate M' in the reaction M-412 in equilibrium hv M' leads to delta BR-570 could be deduced from a photostationary mixture of M-412 and M'. Difference procedures were applied to obtain RR spectra of the L-550 intermediate and of two new long-lived species, R1'-590 and R2-550. From kinetic data it is suggested that T1'-590 links the proton-translocating cycle to the "13-cis" cycle of BR-548. The protonation and isomeric states of the different species are discussed in light of the new spectroscopic and kinetic data. It is found that conformational changes during the photochemical cycle play an important role.

Advanced intermediate temperature sodium-nickel chloride batteries with ultra-high energy density.

PubMed

Li, Guosheng; Lu, Xiaochuan; Kim, Jin Y; Meinhardt, Kerry D; Chang, Hee Jung; Canfield, Nathan L; Sprenkle, Vincent L

2016-02-11

Sodium-metal halide batteries have been considered as one of the more attractive technologies for stationary electrical energy storage, however, they are not used for broader applications despite their relatively well-known redox system. One of the roadblocks hindering market penetration is the high-operating temperature. Here we demonstrate that planar sodium-nickel chloride batteries can be operated at an intermediate temperature of 190 °C with ultra-high energy density. A specific energy density of 350 Wh kg(-1), higher than that of conventional tubular sodium-nickel chloride batteries (280 °C), is obtained for planar sodium-nickel chloride batteries operated at 190 °C over a long-term cell test (1,000 cycles), and it attributed to the slower particle growth of the cathode materials at the lower operating temperature. Results reported here demonstrate that planar sodium-nickel chloride batteries operated at an intermediate temperature could greatly benefit this traditional energy storage technology by improving battery energy density, cycle life and reducing material costs.

Advanced intermediate temperature sodium–nickel chloride batteries with ultra-high energy density

PubMed Central

Li, Guosheng; Lu, Xiaochuan; Kim, Jin Y.; Meinhardt, Kerry D.; Chang, Hee Jung; Canfield, Nathan L.; Sprenkle, Vincent L.

2016-01-01

Sodium-metal halide batteries have been considered as one of the more attractive technologies for stationary electrical energy storage, however, they are not used for broader applications despite their relatively well-known redox system. One of the roadblocks hindering market penetration is the high-operating temperature. Here we demonstrate that planar sodium–nickel chloride batteries can be operated at an intermediate temperature of 190 °C with ultra-high energy density. A specific energy density of 350 Wh kg−1, higher than that of conventional tubular sodium–nickel chloride batteries (280 °C), is obtained for planar sodium–nickel chloride batteries operated at 190 °C over a long-term cell test (1,000 cycles), and it attributed to the slower particle growth of the cathode materials at the lower operating temperature. Results reported here demonstrate that planar sodium–nickel chloride batteries operated at an intermediate temperature could greatly benefit this traditional energy storage technology by improving battery energy density, cycle life and reducing material costs. PMID:26864635

Origin of the Reductive Tricarboxylic Acid (rTCA) Cycle-Type CO2 Fixation: A Perspective

PubMed Central

Fujishima, Kosuke

2017-01-01

The reductive tricarboxylic acid (rTCA) cycle is among the most plausible candidates for the first autotrophic metabolism in the earliest life. Extant enzymes fixing CO2 in this cycle contain cofactors at the catalytic centers, but it is unlikely that the protein/cofactor system emerged at once in a prebiotic process. Here, we discuss the feasibility of non-enzymatic cofactor-assisted drive of the rTCA reactions in the primitive Earth environments, particularly focusing on the acetyl-CoA conversion to pyruvate. Based on the energetic and mechanistic aspects of this reaction, we propose that the deep-sea hydrothermal vent environments with active electricity generation in the presence of various sulfide catalysts are a promising setting for it to progress. Our view supports the theory of an autotrophic origin of life from primordial carbon assimilation within a sulfide-rich hydrothermal vent.

Utilization of acidic α-amino acids as acyl donors: an effective stereo-controllable synthesis of aryl-keto α-amino acids and their derivatives.

PubMed

Wang, Lei; Murai, Yuta; Yoshida, Takuma; Okamoto, Masashi; Tachrim, Zetryana Puteri; Hashidoko, Yasuyuki; Hashimoto, Makoto

2014-05-16

Aryl-keto-containing α-amino acids are of great importance in organic chemistry and biochemistry. They are valuable intermediates for the construction of hydroxyl α-amino acids, nonproteinogenic α-amino acids, as well as other biofunctional components. Friedel-Crafts acylation is an effective method to prepare aryl-keto derivatives. In this review, we summarize the preparation of aryl-keto containing α-amino acids by Friedel-Crafts acylation using acidic α-amino acids as acyl-donors and Lewis acids or Brönsted acids as catalysts.

Redox Conversion of Chromium(VI) and Arsenic(III) with the Intermediates of Chromium(V) and Arsenic(IV) via AuPd/CNTs Electrocatalysis in Acid Aqueous Solution.

PubMed

Sun, Meng; Zhang, Gong; Qin, Yinghua; Cao, Meijuan; Liu, Yang; Li, Jinghong; Qu, Jiuhui; Liu, Huijuan

2015-08-04

Simultaneous reduction of Cr(VI) to Cr(III) and oxidation of As(III) to As(V) is a promising pretreatment process for the removal of chromium and arsenic from acid aqueous solution. In this work, the synergistic redox conversion of Cr(VI) and As(III) was efficiently achieved in a three-dimensional electrocatalytic reactor with synthesized AuPd/CNTs particles as electrocatalysts. The AuPd/CNTs facilitated the exposure of active Pd{111} facets and possessed an approximate two-electron-transfer pathway of oxygen reduction with the highly efficient formation of H2O2 as end product, resulting in the electrocatalytic reduction of 97.2 ± 2.4% of Cr(VI) and oxidation of 95.7 ± 4% of As(III). The electrocatalytic reduction of Cr(VI) was significantly accelerated prior to the electrocatalytic oxidation of As(III), and the effectiveness of Cr(VI)/As(III) conversion was favored at increased currents from 20 to 150 mA, decreased initial pH from 7 to 1 and concentrations of Cr(VI) and As(III) ranging from 50 to 1 mg/L. The crucial intermediates of Cr(V) and As(IV) and active free radicals HO(•) and O2(•-) were found for the first time, whose roles in the control of Cr(VI)/As(III) redox conversion were proposed. Finally, the potential applicability of AuPd/CNTs was revealed by their stability in electrocatalytic conversion over 10 cycles.

Intermediate stage of sleep and acute cerveau isolé preparation in the rat.

PubMed

User, P; Gioanni, H; Gottesmann, C

1980-01-01

The acute cerveau isole rat shows spindle bursts of large amplitude alternating with low voltage activity in the frontal cortex and continuous theta rhythm in the dorsal hippocampus. These patterns closely resemble an "intermediate" stage of sleep-waking cycle, when the forebrain structures seem to be functionally disconnected from the brainstem.

Intermediate treatments

Treesearch

John R. Jones; Wayne D. Shepperd

1985-01-01

Intermediate treatments are those applied after a new stand is successfully established and before the final harvest. These include not only intermediate cuttings - primarily thinning - but also fertilization, irrigation, and protection of the stand from damaging agents.

Mitochondrial overload and incomplete fatty acid oxidation contribute to skeletal muscle insulin resistance.

PubMed

Koves, Timothy R; Ussher, John R; Noland, Robert C; Slentz, Dorothy; Mosedale, Merrie; Ilkayeva, Olga; Bain, James; Stevens, Robert; Dyck, Jason R B; Newgard, Christopher B; Lopaschuk, Gary D; Muoio, Deborah M

2008-01-01

Previous studies have suggested that insulin resistance develops secondary to diminished fat oxidation and resultant accumulation of cytosolic lipid molecules that impair insulin signaling. Contrary to this model, the present study used targeted metabolomics to find that obesity-related insulin resistance in skeletal muscle is characterized by excessive beta-oxidation, impaired switching to carbohydrate substrate during the fasted-to-fed transition, and coincident depletion of organic acid intermediates of the tricarboxylic acid cycle. In cultured myotubes, lipid-induced insulin resistance was prevented by manipulations that restrict fatty acid uptake into mitochondria. These results were recapitulated in mice lacking malonyl-CoA decarboxylase (MCD), an enzyme that promotes mitochondrial beta-oxidation by relieving malonyl-CoA-mediated inhibition of carnitine palmitoyltransferase 1. Thus, mcd(-/-) mice exhibit reduced rates of fat catabolism and resist diet-induced glucose intolerance despite high intramuscular levels of long-chain acyl-CoAs. These findings reveal a strong connection between skeletal muscle insulin resistance and lipid-induced mitochondrial stress.

Metabolic changes associated with tumor metastasis, part 2: Mitochondria, lipid and amino acid metabolism.

PubMed

Porporato, Paolo E; Payen, Valéry L; Baselet, Bjorn; Sonveaux, Pierre

2016-04-01

Metabolic alterations are a hallmark of cancer controlling tumor progression and metastasis. Among the various metabolic phenotypes encountered in tumors, this review focuses on the contributions of mitochondria, lipid and amino acid metabolism to the metastatic process. Tumor cells require functional mitochondria to grow, proliferate and metastasize, but shifts in mitochondrial activities confer pro-metastatic traits encompassing increased production of mitochondrial reactive oxygen species (mtROS), enhanced resistance to apoptosis and the increased or de novo production of metabolic intermediates of the TCA cycle behaving as oncometabolites, including succinate, fumarate, and D-2-hydroxyglutarate that control energy production, biosynthesis and the redox state. Lipid metabolism and the metabolism of amino acids, such as glutamine, glutamate and proline are also currently emerging as focal control points of cancer metastasis.

METHOXYACETALDEHYDE, AN INTERMEDIATE METABOLITE OF 2-METHOXYETHANOL, IS IMMUNOSUPPRESSIVE IN THE RAT

EPA Science Inventory

2-Methoxyethanol (ME) is metabolized to 2-methoxyacetic acid (MAA) via the intermediate metabolite methoxyacetaldehyde (MAAD). oth ME and MAA have been shown in this laboratory to be immunosuppressive in rats following oral dosing. n this study, the plaque-forming cell (PFC) resp...

Studying Reaction Intermediates Formed at Graphenic Surfaces

NASA Astrophysics Data System (ADS)

Sarkar, Depanjan; Sen Gupta, Soujit; Narayanan, Rahul; Pradeep, Thalappil

2014-03-01

We report in-situ production and detection of intermediates at graphenic surfaces, especially during alcohol oxidation. Alcohol oxidation to acid occurs on graphene oxide-coated paper surface, driven by an electrical potential, in a paper spray mass spectrometry experiment. As paper spray ionization is a fast process and the time scale matches with the reaction time scale, we were able to detect the intermediate, acetal. This is the first observation of acetal formed in surface oxidation. The process is not limited to alcohols and the reaction has been extended to aldehydes, amines, phosphenes, sugars, etc., where reaction products were detected instantaneously. By combining surface reactions with ambient ionization and mass spectrometry, we show that new insights into chemical reactions become feasible. We suggest that several other chemical transformations may be studied this way. This work opens up a new pathway for different industrially and energetically important reactions using different metal catalysts and modified substrate.

Mechanistic studies of a novel C-S lyase in ergothioneine biosynthesis: the involvement of a sulfenic acid intermediate

PubMed Central

Song, Heng; Hu, Wen; Naowarojna, Nathchar; Her, Ampon Sae; Wang, Shu; Desai, Rushil; Qin, Li; Chen, Xiaoping; Liu, Pinghua

2015-01-01

Ergothioneine is a histidine thio-derivative isolated in 1909. In ergothioneine biosynthesis, the combination of a mononuclear non-heme iron enzyme catalyzed oxidative C-S bond formation reaction and a PLP-mediated C-S lyase (EgtE) reaction results in a net sulfur transfer from cysteine to histidine side-chain. This demonstrates a new sulfur transfer strategy in the biosynthesis of sulfur-containing natural products. Due to difficulties associated with the overexpression of Mycobacterium smegmatis EgtE protein, the proposed EgtE functionality remained to be verified biochemically. In this study, we have successfully overexpressed and purified M. smegmatis EgtE enzyme and evaluated its activities under different in vitro conditions: C-S lyase reaction using either thioether or sulfoxide as a substrate in the presence or absence of reductants. Results from our biochemical characterizations support the assignment of sulfoxide 4 as the native EgtE substrate and the involvement of a sulfenic acid intermediate in the ergothioneine C-S lyase reaction. PMID:26149121

Ultrathin dendrimer-graphene oxide composite film for stable cycling lithium-sulfur batteries.

PubMed

Liu, Wen; Jiang, Jianbing; Yang, Ke R; Mi, Yingying; Kumaravadivel, Piranavan; Zhong, Yiren; Fan, Qi; Weng, Zhe; Wu, Zishan; Cha, Judy J; Zhou, Henghui; Batista, Victor S; Brudvig, Gary W; Wang, Hailiang

2017-04-04

Lithium-sulfur batteries (Li-S batteries) have attracted intense interest because of their high specific capacity and low cost, although they are still hindered by severe capacity loss upon cycling caused by the soluble lithium polysulfide intermediates. Although many structure innovations at the material and device levels have been explored for the ultimate goal of realizing long cycle life of Li-S batteries, it remains a major challenge to achieve stable cycling while avoiding energy and power density compromises caused by the introduction of significant dead weight/volume and increased electrochemical resistance. Here we introduce an ultrathin composite film consisting of naphthalimide-functionalized poly(amidoamine) dendrimers and graphene oxide nanosheets as a cycling stabilizer. Combining the dendrimer structure that can confine polysulfide intermediates chemically and physically together with the graphene oxide that renders the film robust and thin (<1% of the thickness of the active sulfur layer), the composite film is designed to enable stable cycling of sulfur cathodes without compromising the energy and power densities. Our sulfur electrodes coated with the composite film exhibit very good cycling stability, together with high sulfur content, large areal capacity, and improved power rate.

Crystal structures of alkylperoxo and anhydride intermediates in an intradiol ring-cleaving dioxygenase

DOE PAGES

Knoot, Cory J.; Purpero, Vincent M.; Lipscomb, John D.

2014-12-29

Intradiol aromatic ring-cleaving dioxygenases use an active site, nonheme Fe 3+ to activate O 2 and catecholic substrates for reaction. The inability of Fe 3+ to directly bind O 2 presents a mechanistic conundrum. The reaction mechanism of protocatechuate 3,4-dioxygenase is investigated in this paper using the alternative substrate 4-fluorocatechol. This substrate is found to slow the reaction at several steps throughout the mechanistic cycle, allowing the intermediates to be detected in solution studies. When the reaction was initiated in an enzyme crystal, it was found to halt at one of two intermediates depending on the pH of the surroundingmore » solution. The X-ray crystal structure of the intermediate at pH 6.5 revealed the key alkylperoxo-Fe 3+ species, and the anhydride-Fe 3+ intermediate was found for a crystal reacted at pH 8.5. Intermediates of these types have not been structurally characterized for intradiol dioxygenases, and they validate four decades of spectroscopic, kinetic, and computational studies. In contrast to our similar in crystallo crystallographic studies of an Fe 2+-containing extradiol dioxygenase, no evidence for a superoxo or peroxo intermediate preceding the alkylperoxo was found. This observation and the lack of spectroscopic evidence for an Fe 2+ intermediate that could bind O 2 are consistent with concerted formation of the alkylperoxo followed by Criegee rearrangement to yield the anhydride and ultimately ring-opened product. Finally, structural comparison of the alkylperoxo intermediates from the intra- and extradiol dioxygenases provides a rationale for site specificity of ring cleavage.« less

Echinococcus multilocularis on Svalbard: introduction of an intermediate host has enabled the local life-cycle.

PubMed

Henttonen, H; Fuglei, E; Gower, C N; Haukisalmi, V; Ims, R A; Niemimaa, J; Yoccoz, N G

2001-12-01

The taeniid tapeworm Echinococcus multilocularis is here reported for the first time at the Svalbard Archipelago in the Norwegian Arctic. This new finding is interesting because the establishment of E. multilocularis is due to a recent anthropogenic introduction of its intermediate host--the sibling vole Microtus rossiaemeridionalis at Svalbard. The parasite itself has probably become naturally transferred to Svalbard due to migratory movements of its final host--the arctic fox Alopex lagopus between source areas for E. multilocularis in Siberia and Svalbard. We report macroscopically determined prevalence of E. multilocularis from a sample of 224 voles trapped in August in 1999 and 2000. The prevalence was among the highest ever recorded in intermediate hosts and was dependent on age and sex of the hosts approaching 100% in overwintered males. The high prevalence and the simplicity of the vole-arctic fox-E. multilocularis system at Svalbard makes it an eminent model system for further epidemiological studies.

Aspartate protects Lactobacillus casei against acid stress.

PubMed

Wu, Chongde; Zhang, Juan; Du, Guocheng; Chen, Jian

2013-05-01

The aim of this study was to investigate the effect of aspartate on the acid tolerance of L. casei. Acid stress induced the accumulation of intracellular aspartate in L. casei, and the acid-resistant mutant exhibited 32.5 % higher amount of aspartate than that of the parental strain at pH 4.3. Exogenous aspartate improved the growth performance and acid tolerance of Lactobacillus casei during acid stress. When cultivated in the presence of 50 mM aspartate, the biomass of cells increased 65.8 % compared with the control (without aspartate addition). In addition, cells grown at pH 4.3 with aspartate addition were challenged at pH 3.3 for 3 h, and the survival rate increased 42.26-fold. Analysis of the physiological data showed that the aspartate-supplemented cells exhibited higher intracellular pH (pHi), intracellular NH4 (+) content, H(+)-ATPase activity, and intracellular ATP pool. In addition, higher contents of intermediates involved in glycolysis and tricarboxylic acid cycle were observed in cells in the presence of aspartate. The increased contents of many amino acids including aspartate, arginine, leucine, isoleucine, and valine in aspartate-added cells may contribute to the regulation of pHi. Transcriptional analysis showed that the expression of argG and argH increased during acid stress, and the addition of aspartate induced 1.46- and 3.06-fold higher expressions of argG and argH, respectively, compared with the control. Results presented in this manuscript suggested that aspartate may protect L. casei against acid stress, and it may be used as a potential protectant during the production of probiotics.

A plant pathogenic bacterium exploits the tricarboxylic acid cycle metabolic pathway of its insect vector

PubMed Central

Nehela, Yasser; Hijaz, Faraj; Vincent, Christopher I.

2018-01-01

ABSTRACT Huanglongbing in citrus is caused by a phloem-limited, uncultivable, gram-negative α-proteobacterium, Candidatus Liberibacter asiaticus (CLas). CLas is transmitted by the phloem-sucking insect, Diaphorina citri (Hemiptera: Liviidae), in a persistent, circulative, and propagative manner. In this study, we investigated the metabolomic and respiration rates changes in D. citri upon infection with CLas using gas chromatography-mass spectrometry (GC-MS) and gas exchange analysis. The level of glycine, L-serine, L-threonine, and gamma-amino butyric acid were higher in CLas-infected D. citri, while L-proline, L-aspartic acid, and L-pyroglutamic acid were lower in CLas-infected D. citri compared with the control. Citric acid was increased in CLas-infected D. citri, whereas malic and succinic acids were reduced. Interestingly, most of the reduced metabolites such as malate, succinate, aspartate, and L-proline are required for the growth of CLas. The increase in citric acid, serine, and glycine indicated that CLas induced glycolysis and the tricarboxylic acid cycle (TCA) in its vector. In agreement with the GC-MS results, the gene expression results also indicated that glycolysis and TCA were induced in CLas-infected D. citri and this was accompanied with an increases in respiration rate. Phosphoric acid and most of the sugar alcohols were higher in CLas-infected D. citri, indicating a response to the biotic stress or cell damage. Only slight increases in the levels of few sugars were observed in CLas-infected D. citri, which indicated that sugars are tightly regulated by D. citri. Our results indicated that CLas induces nutrient and energetic stress in its host insect. This study may provide some insights into the mechanism of colonization of CLas in its vector. PMID:28594267

A plant pathogenic bacterium exploits the tricarboxylic acid cycle metabolic pathway of its insect vector.

PubMed

Killiny, Nabil; Nehela, Yasser; Hijaz, Faraj; Vincent, Christopher I

2018-01-01

Huanglongbing in citrus is caused by a phloem-limited, uncultivable, gram-negative α-proteobacterium, Candidatus Liberibacter asiaticus (CLas). CLas is transmitted by the phloem-sucking insect, Diaphorina citri (Hemiptera: Liviidae), in a persistent, circulative, and propagative manner. In this study, we investigated the metabolomic and respiration rates changes in D. citri upon infection with CLas using gas chromatography-mass spectrometry (GC-MS) and gas exchange analysis. The level of glycine, L -serine, L -threonine, and gamma-amino butyric acid were higher in CLas-infected D. citri, while L -proline, L -aspartic acid, and L -pyroglutamic acid were lower in CLas-infected D. citri compared with the control. Citric acid was increased in CLas-infected D. citri, whereas malic and succinic acids were reduced. Interestingly, most of the reduced metabolites such as malate, succinate, aspartate, and L -proline are required for the growth of CLas. The increase in citric acid, serine, and glycine indicated that CLas induced glycolysis and the tricarboxylic acid cycle (TCA) in its vector. In agreement with the GC-MS results, the gene expression results also indicated that glycolysis and TCA were induced in CLas-infected D. citri and this was accompanied with an increases in respiration rate. Phosphoric acid and most of the sugar alcohols were higher in CLas-infected D. citri, indicating a response to the biotic stress or cell damage. Only slight increases in the levels of few sugars were observed in CLas-infected D. citri, which indicated that sugars are tightly regulated by D. citri. Our results indicated that CLas induces nutrient and energetic stress in its host insect. This study may provide some insights into the mechanism of colonization of CLas in its vector.

Environmental Life Cycle Assessment of Diets with Improved Omega-3 Fatty Acid Profiles

PubMed Central

Coelho, Carla R. V.; Pernollet, Franck; van der Werf, Hayo M. G.

2016-01-01

A high incidence of cardiovascular disease is observed worldwide, and dietary habits are one of the risk factors for these diseases. Omega-3 polyunsaturated fatty acids in the diet help to prevent cardiovascular disease. We used life cycle assessment to analyse the potential of two strategies to improve the nutritional and environmental characteristics of French diets: 1) modifying diets by changing the quantities and proportions of foods and 2) increasing the omega-3 contents in diets by replacing mainly animal foods with equivalent animal foods having higher omega-3 contents. We also investigated other possibilities for reducing environmental impacts. Our results showed that a diet compliant with nutritional recommendations for macronutrients had fewer environmental impacts than the current average French diet. Moving from an omnivorous to a vegetarian diet further reduced environmental impacts. Increasing the omega-3 contents in animal rations increased Eicosapentaenoic Acid (EPA) and Docosahexaenoic Acid (DHA) in animal food products. Providing these enriched animal foods in human diets increased their EPA and DHA contents without affecting their environmental impacts. However, in diets that did not contain fish, EPA and DHA contents were well below the levels recommended by health authorities, despite the inclusion of animal products enriched in EPA and DHA. Reducing meat consumption and avoidable waste at home are two main avenues for reducing environmental impacts of diets. PMID:27504959

Environmental Life Cycle Assessment of Diets with Improved Omega-3 Fatty Acid Profiles.

PubMed

Coelho, Carla R V; Pernollet, Franck; van der Werf, Hayo M G

2016-01-01

A high incidence of cardiovascular disease is observed worldwide, and dietary habits are one of the risk factors for these diseases. Omega-3 polyunsaturated fatty acids in the diet help to prevent cardiovascular disease. We used life cycle assessment to analyse the potential of two strategies to improve the nutritional and environmental characteristics of French diets: 1) modifying diets by changing the quantities and proportions of foods and 2) increasing the omega-3 contents in diets by replacing mainly animal foods with equivalent animal foods having higher omega-3 contents. We also investigated other possibilities for reducing environmental impacts. Our results showed that a diet compliant with nutritional recommendations for macronutrients had fewer environmental impacts than the current average French diet. Moving from an omnivorous to a vegetarian diet further reduced environmental impacts. Increasing the omega-3 contents in animal rations increased Eicosapentaenoic Acid (EPA) and Docosahexaenoic Acid (DHA) in animal food products. Providing these enriched animal foods in human diets increased their EPA and DHA contents without affecting their environmental impacts. However, in diets that did not contain fish, EPA and DHA contents were well below the levels recommended by health authorities, despite the inclusion of animal products enriched in EPA and DHA. Reducing meat consumption and avoidable waste at home are two main avenues for reducing environmental impacts of diets.

Aprotinin may increase mortality in low and intermediate risk but not in high risk cardiac surgical patients compared to tranexamic acid and ε-aminocaproic acid -- a meta-analysis of randomised and observational trials of over 30.000 patients.

PubMed

Meybohm, Patrick; Herrmann, Eva; Nierhoff, Julia; Zacharowski, Kai

2013-01-01

To compare the effect of aprotinin with the effect of lysine analogues (tranexamic acid and ε-aminocaproic acid) on early mortality in three subgroups of patients: low, intermediate and high risk of cardiac surgery. We performed a meta-analysis of randomised controlled trials and observational with the following data sources: Medline, Cochrane Library, and reference lists of identified articles. The primary outcome measure was early (in-hospital/30-day) mortality. The secondary outcome measures were any transfusion of packed red blood cells within 24 hours after surgery, any re-operation for bleeding or massive bleeding, and acute renal dysfunction or failure within the selected cited publications, respectively. Out of 328 search results, 31 studies (15 trials and 16 observational studies) included 33,501 patients. Early mortality was significantly increased after aprotinin vs. lysine analogues with a pooled risk ratio (95% CI) of 1.58 (1.13-2.21), p<0.001 in the low (n = 14,297) and in the intermediate risk subgroup (1.42 (1.09-1.84), p<0.001; n = 14,427), respectively. Contrarily, in the subgroup of high risk patients (n = 4,777), the risk for mortality did not differ significantly between aprotinin and lysine analogues (1.03 (0.67-1.58), p = 0.90). Aprotinin may be associated with an increased risk of mortality in low and intermediate risk cardiac surgery, but presumably may has no effect on early mortality in a subgroup of high risk cardiac surgery compared to lysine analogues. Thus, decisions to re-license aprotinin in lower risk patients should critically be debated. In contrast, aprotinin might probably be beneficial in high risk cardiac surgery as it reduces risk of transfusion and bleeding complications.

Fatty acid-producing hosts

DOEpatents

Pfleger, Brian F; Lennen, Rebecca M

2013-12-31

Described are hosts for overproducing a fatty acid product such as a fatty acid. The hosts include an exogenous nucleic acid encoding a thioesterase and, optionally, an exogenous nucleic acid encoding an acetyl-CoA carboxylase, wherein an acyl-CoA synthetase in the hosts are functionally delected. The hosts prefereably include the nucleic acid encoding the thioesterase at an intermediate copy number. The hosts are preferably recominantly stable and growth-competent at 37.degree. C. Methods of producing a fatty acid product comprising culturing such hosts at 37.degree. C. are also described.

Low Power LDPC Code Decoder Architecture Based on Intermediate Message Compression Technique

NASA Astrophysics Data System (ADS)

Shimizu, Kazunori; Togawa, Nozomu; Ikenaga, Takeshi; Goto, Satoshi

Reducing the power dissipation for LDPC code decoder is a major challenging task to apply it to the practical digital communication systems. In this paper, we propose a low power LDPC code decoder architecture based on an intermediate message-compression technique which features as follows: (i) An intermediate message compression technique enables the decoder to reduce the required memory capacity and write power dissipation. (ii) A clock gated shift register based intermediate message memory architecture enables the decoder to decompress the compressed messages in a single clock cycle while reducing the read power dissipation. The combination of the above two techniques enables the decoder to reduce the power dissipation while keeping the decoding throughput. The simulation results show that the proposed architecture improves the power efficiency up to 52% and 18% compared to that of the decoder based on the overlapped schedule and the rapid convergence schedule without the proposed techniques respectively.

Intermediate hosts of the trematode Collyriclum faba (Plagiochiida: Collyriclidae) identified by an integrated morphological and genetic approach.

PubMed

Heneberg, Petr; Faltýnková, Anna; Bizos, Jiří; Malá, Milena; Žiak, Juraj; Literák, Ivan

2015-02-08

The cutaneous monostome trematode Collyriclum faba (Bremser in Schmalz, 1831) is a bird parasite with a hitherto unknown life cycle and highly focal occurrence across the Holarctic and Neotropic ecozones. Representative specimens of benthic organisms were sampled at multiple sites and dates within the known foci of C. faba occurrence in Slovakia. A combined approach involving detailed morphological examination and sequencing of two independent DNA loci was used for their analysis. We elucidated the complete life cycle of C. faba, which we determined to include the aquatic gastropod mollusk Bythinella austriaca (Frauenfeld, 1857) as the first intermediate host, the mayflies of the family Heptageniidae, Ecdyonurus venosus (Fabricius, 1775) and Rhithrogena picteti Sowa, 1971 x iridina (Kolenati, 1839), as the second intermediate hosts, and birds (primarily but not exclusively passeriform birds) as the definitive hosts. Bythinella austriaca occurs focally in the springs of tributaries of the Danube in the Alpine-Carpathian region. The restricted distribution of B. austriaca explains the highly focal distribution of C. faba noticed previously in spite of the broad distribution of its second intermediate and definitive host species. Utilization of both larval and adult Ephemeroptera spp. as the second intermediate hosts explains the known spectrum of the definitive host species, with the highest prevalence in species feeding on larvae of Ephemeroptera, such as Cinclus cinclus (Linnaeus, 1758) and Motacilla cinerea Tunstall, 1771, or adults of Ephemeroptera, such as Sylvia atricapilla (Linnaeus, 1758) and Regulus regulus (Linnaeus, 1758). In this study, we also determine the prevalence and DNA sequences of other immature trematode specimens found in the examined benthic organisms (particularly the families Microphallidae, Troglotrematidae and Nanophyetidae and Euryhelmis zelleri Grabda-Kazubska, 1980, Heterophyidae), and describe cercariae of C. faba. We determined the

Effector region of the translation elongation factor EF-Tu.GTP complex stabilizes an orthoester acid intermediate structure of aminoacyl-tRNA in a ternary complex.

PubMed Central

Förster, C; Limmer, S; Zeidler, W; Sprinzl, M

1994-01-01

tRNA(Val) from Escherichia coli was aminoacylated with [1-13C]valine and its complex with Thermus thermophilus elongation factor EF-Tu.GTP was analyzed by 13C NMR spectroscopy. The results suggest that the aminoacyl residue of the valyl-tRNA in ternary complex with bacterial EF-Tu and GTP is not attached to tRNA by a regular ester bond to either a 2'- or 3'-hydroxyl group; instead, an intermediate orthoester acid structure with covalent linkage to both vicinal hydroxyls of the terminal adenosine-76 is formed. Mutation of arginine-59 located in the effector region of EF-Tu, a conserved residue in protein elongation factors and the alpha subunits of heterotrimeric guanine nucleotide-binding regulatory proteins (G proteins), abolishes the stabilization of the orthoester acid structure of aminoacyl-tRNA. PMID:8183898

History of fatty acids

USDA-ARS?s Scientific Manuscript database

Fatty acids are basic renewable chemical building blocks that can be used as intermediates for a multitude of products. Today the global value of fatty acids exceeds 18 billion dollars and is expected to increase to nearly 26 billion over the period from 2014-2019. From it auspicious beginnings, the...

Evolution of complex life cycles in trophically transmitted helminths. I. Host incorporation and trophic ascent.

PubMed

Parker, G A; Ball, M A; Chubb, J C

2015-02-01

Links between parasites and food webs are evolutionarily ancient but dynamic: life history theory provides insights into helminth complex life cycle origins. Most adult helminths benefit by sexual reproduction in vertebrates, often high up food chains, but direct infection is commonly constrained by a trophic vacuum between free-living propagules and definitive hosts. Intermediate hosts fill this vacuum, facilitating transmission to definitive hosts. The central question concerns why sexual reproduction, and sometimes even larval growth, is suppressed in intermediate hosts, favouring growth arrest at larval maturity in intermediate hosts and reproductive suppression until transmission to definitive hosts? Increased longevity and higher growth in definitive hosts can generate selection for larger parasite body size and higher fecundity at sexual maturity. Life cycle length is increased by two evolutionary mechanisms, upward and downward incorporation, allowing simple (one-host) cycles to become complex (multihost). In downward incorporation, an intermediate host is added below the definitive host: models suggest that downward incorporation probably evolves only after ecological or evolutionary perturbations create a trophic vacuum. In upward incorporation, a new definitive host is added above the original definitive host, which subsequently becomes an intermediate host, again maintained by the trophic vacuum: theory suggests that this is plausible even under constant ecological/evolutionary conditions. The final cycle is similar irrespective of its origin (upward or downward). Insights about host incorporation are best gained by linking comparative phylogenetic analyses (describing evolutionary history) with evolutionary models (examining selective forces). Ascent of host trophic levels and evolution of optimal host taxa ranges are discussed. © 2015 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2015 European Society For Evolutionary

Low-Dose-Rate Brachytherapy Versus Cryotherapy in Low- and Intermediate-Risk Prostate Cancer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gestaut, Matthew M., E-mail: Matthew.Gestaut@BSWHealth.org; Cai, Wendi; Vyas, Shilpa

Purpose: Cryotherapy and brachytherapy are definitive local treatment options for low- to intermediate-risk prostate cancer. There are both prospective and retrospective data for brachytherapy, but the use of cryotherapy has been limited primarily to single-institution retrospective studies. Currently, no published evidence has compared low-dose-rate brachytherapy versus cryotherapy. Methods and Materials: Institutional review board approval was obtained to conduct a retrospective chart review of consecutive patients treated at our institution from 1990 to 2012. For inclusion, patients must have received a prostate cancer diagnosis and have been considered to have low- to intermediate-risk disease according to the National Comprehensive Cancer Networkmore » criteria. All patients received brachytherapy or cryotherapy treatment. Disease specifics and failure details were collected for all patients. Failure was defined as prostate-specific antigen nadir +2 ng/mL. Results: A total of 359 patients were analyzed. The groups comprised 50 low-risk cryotherapy (LRC), 92 intermediate-risk cryotherapy (IRC), 133 low-risk brachytherapy (LRB), and 84 intermediate-risk brachytherapy (IRB) patients. The median prostate-specific antigen follow-up periods were 85.6 months (LRC), 59.2 months (IRC), 74.9 months (LRB), and 59.8 months (IRB). The 5-year biochemical progression–free survival (bPFS) rate was 57.9% in the cryotherapy group versus 89.6% in the brachytherapy group (P<.0001). The 5-year bPFS rate was 70.0% (LRC), 51.4% (IRC), 89.4% (LRB), and 89.7% (IRB). The bPFS rate was significantly different between brachytherapy and cryotherapy for low- and intermediate-risk groups (P<.05). The mean nadir temperature reached for cryotherapy patients was −35°C (range, −96°C to −6°C). Cryotherapy used a median of 2 freeze-thaw cycles (range, 2-4 freeze-thaw cycles). Conclusions: Results from this study suggest that cryotherapy is inferior to brachytherapy for

Seasonal variation in abiotic factors and ferulic acid toxicity in snail-attractant pellets against the intermediate host snail Lymnaea acuminata.

PubMed

Agrahari, P; Singh, D K

2013-11-01

Laboratory evaluation was made to access the seasonal variations in abiotic environmental factors temperature, pH, dissolved oxygen, carbon dioxide, electrical conductivity and ferulic acid toxicity in snail-attractant pellets (SAP) against the intermediate host snail Lymnaea acuminata in each month of the years 2010 and 2011. On the basis of a 24-h toxicity assay, it was noted that lethal concentration values of 4.03, 3.73% and 4.45% in SAP containing starch and 4.16, 4.23% and 4.29% in SAP containing proline during the months of May, June and September, respectively, were most effective in killing the snails, while SAP containing starch/proline + ferulic acid was least effective in the month of January/February (24-h lethal concentration value was 7.67%/7.63% in SAP). There was a significant positive correlation between lethal concentration value of ferulic acid containing SAP and levels of dissolved O2 /pH of water in corresponding months. On the contrary, a negative correlation was observed between lethal concentration value and dissolved CO2 /temperature of test water in the same months. To ascertain that such a relationship between toxicity and abiotic factors is not co-incidental, the nervous tissue of treated (40% and 80% of 24-h lethal concentration value) and control group of snails was assayed for the activity of acetylcholinesterase (AChE) in each of the 12 months of the same year. There was a maximum inhibition of 58.43% of AChE, in snails exposed to 80% of the 24-h lethal concentration value of ferulic acid + starch in the month of May. This work shows conclusively that the best time to control snail population with SAP containing ferulic acid is during the months of May, June and September. © 2012 Blackwell Verlag GmbH.

In vitro ruminal biohydrogenation of eicosapentaenoic (EPA), docosapentaenoic (DPA), and docosahexaenoic acid (DHA) in cows and ewes: Intermediate metabolites and pathways.

PubMed

Toral, P G; Hervás, G; Leskinen, H; Shingfield, K J; Frutos, P

2018-04-25

A great deal of uncertainty still exists about intermediate metabolites and pathways explaining the biohydrogenation (BH) of 20- and 22-carbon polyunsaturated fatty acids (PUFA). Therefore, this study was conducted to provide further insight into the ruminal metabolism of 20:5 n-3 (EPA), 22:5 n-3 (DPA), and 22:6 n-3 (DHA), the main n-3 PUFA present in the marine lipids used in dairy ruminant feeding, and to examine potential differences between bovine and ovine. To meet this aim, we investigated the 20- and 22-carbon metabolites accumulated during in vitro incubation of EPA, DPA, and DHA with rumen inocula from cows and ewes. The PUFA were added at a dose of 2% incubated dry matter and digesta samples were analyzed after 24 h of incubation using complementary gas-liquid chromatography of fatty acid methyl esters and gas chromatography-mass spectrometry of 4,4-dimethyloxazoline derivatives. Results suggested that the main BH pathway of EPA and DPA would proceed via the reduction of the double bond closest to the carboxyl group (cis-5 in EPA and cis-7 in DPA); curiously, this mechanism seemed of much lower importance for DHA. Thus, DPA would not be a major intermediate product of DHA and their BH might actually follow separate pathways, with the accumulation of numerous unique metabolites in each case. A principal component analysis supported this hypothesis, with a clear separation between PUFA treatments in the score and loading plots. Within EPA and DPA groups, cow and ewe samples loaded separately from each other but not distant. No conjugated 20:5, 22:5, or 22:6 isomer compatible with the initial product of EPA, DPA, or DHA metabolism, respectively, was identified in the ruminal digesta, although this would not unequivocally exclude their transient formation. In this regard, results from DPA incubations provided the first indication that the metabolism of this very long chain PUFA may involve the formation of conjugated double bond structures. The BH of EPA, DPA

Biomedical research of novel biodegradable copoly(amino acid)s based on 6-aminocaproic acid and L-proline.

PubMed

Zhang, Weipeng; Shao, Jianmin

2010-08-01

The biomedical properties of novel biodegradable copoly(amino acid)s based on 6-aminocaproic acid and L-proline were analyzed in this article. The cytotoxicity of the copolymer films was tested in vitro using human embryonic kidney (HEK) 293 cells. The cell proliferation, cell cycle, cell apoptosis, and hemolysis of the polymers were also investigated. No significant cytotoxic response was detected statistically by cytotoxicity assay, and the results of cell apoptosis and cell cycle showed that there were no statistically significant differences in them. Generally, the cells spread and grew well on polymer film. Meanwhile, the extent of hemolysis on the polymers was acceptable. Evaluation of cytotoxicity by cell cycle and apoptosis as a supplementary assay is correspondingly discussed in this article. (c) 2010 Wiley Periodicals, Inc.

Aprotinin May Increase Mortality in Low and Intermediate Risk but Not in High Risk Cardiac Surgical Patients Compared to Tranexamic Acid and ε-Aminocaproic Acid – A Meta-Analysis of Randomised and Observational Trials of over 30.000 Patients

PubMed Central

Meybohm, Patrick; Herrmann, Eva; Nierhoff, Julia; Zacharowski, Kai

2013-01-01

Background To compare the effect of aprotinin with the effect of lysine analogues (tranexamic acid and ε-aminocaproic acid) on early mortality in three subgroups of patients: low, intermediate and high risk of cardiac surgery. Methods and Findings We performed a meta-analysis of randomised controlled trials and observational with the following data sources: Medline, Cochrane Library, and reference lists of identified articles. The primary outcome measure was early (in-hospital/30-day) mortality. The secondary outcome measures were any transfusion of packed red blood cells within 24 hours after surgery, any re-operation for bleeding or massive bleeding, and acute renal dysfunction or failure within the selected cited publications, respectively. Out of 328 search results, 31 studies (15 trials and 16 observational studies) included 33,501 patients. Early mortality was significantly increased after aprotinin vs. lysine analogues with a pooled risk ratio (95% CI) of 1.58 (1.13–2.21), p<0.001 in the low (n = 14,297) and in the intermediate risk subgroup (1.42 (1.09–1.84), p<0.001; n = 14,427), respectively. Contrarily, in the subgroup of high risk patients (n = 4,777), the risk for mortality did not differ significantly between aprotinin and lysine analogues (1.03 (0.67–1.58), p = 0.90). Conclusion Aprotinin may be associated with an increased risk of mortality in low and intermediate risk cardiac surgery, but presumably may has no effect on early mortality in a subgroup of high risk cardiac surgery compared to lysine analogues. Thus, decisions to re-license aprotinin in lower risk patients should critically be debated. In contrast, aprotinin might probably be beneficial in high risk cardiac surgery as it reduces risk of transfusion and bleeding complications. PMID:23483965

Testing of sealed lead-acid batteries

NASA Astrophysics Data System (ADS)

Bush, D. M.; Sealey, J. D.; Miller, D. W.

1984-02-01

Sealed lead acid batteries under development were tested. The goal was to develop a totally maintenance free sealed lead acid battery capable of deep discharge operation in a photovoltaic power system. Sealed lead acid batteries and a group of conventional, flooded lead acid batteries were exposed to a matrix test plan, with some approaching 1000 cycles. This performance was achieved with the standard National Electrical Manufacturers' Association cycle test, and the partial state of charge cycle test. Modes of failure are investigated.

Environmental impacts of producing bioethanol and biobased lactic acid from standalone and integrated biorefineries using a consequential and an attributional life cycle assessment approach.

PubMed

Parajuli, Ranjan; Knudsen, Marie Trydeman; Birkved, Morten; Djomo, Sylvestre Njakou; Corona, Andrea; Dalgaard, Tommy

2017-11-15

This study evaluates the environmental impacts of biorefinery products using consequential (CLCA) and attributional (ALCA) life cycle assessment (LCA) approaches. Within ALCA, economic allocation method was used to distribute impacts among the main products and the coproducts, whereas within the CLCA system expansion was adopted to avoid allocation. The study seeks to answer the questions (i) what is the environmental impacts of process integration?, and (ii) do CLCA and ALCA lead to different conclusions when applied to biorefinery?. Three biorefinery systems were evaluated and compared: a standalone system producing bioethanol from winter wheat-straw (system A), a standalone system producing biobased lactic acid from alfalfa (system B), and an integrated biorefinery system (system C) combining the two standalone systems and producing both bioethanol and lactic acid. The synergy of the integration was the exchange of useful energy necessary for biomass processing in the two standalone systems. The systems were compared against a common reference flow: "1MJ EtOH +1kg LA ", which was set on the basis of products delivered by the system C. Function of the reference flow was to provide service of both fuel (bioethanol) at 99.9% concentration (wt. basis) and biochemical (biobased lactic acid) in food industries at 90% purity; both products delivered at biorefinery gate. The environmental impacts of interest were global warming potential (GWP 100 ), eutrophication potential (EP), non-renewable energy (NRE) use and the agricultural land occupation (ALO). Regardless of the LCA approach adopted, system C performed better in most of the impact categories than both standalone systems. The process wise contribution to the obtained environmental impacts also showed similar impact pattern in both approaches. The study also highlighted that the recirculation of intermediate materials, e.g. C 5 sugar to boost bioethanol yield and that the use of residual streams in the energy

Abrupt changes of intermediate-water oxygen in the northwestern Pacific during the last 27 kyr

NASA Astrophysics Data System (ADS)

Ishizaki, Yui; Ohkushi, Ken'ichi; Ito, Takashi; Kawahata, Hodaka

2009-04-01

An oxygen minimum zone (OMZ) currently exists at intermediate water depths on the northern Japanese margin in the northwestern Pacific. The OMZ results largely from a combination of high surface-water productivity and poor ventilation of intermediate waters. We investigated the late Quaternary history (last 27 kyr) of the intensity of this OMZ using changes in benthic foraminiferal carbon isotopes and assemblages in a sediment core taken on the continental slope off Shimokita Peninsula, northern Japan, at a water depth of 975 m. The core was located well within the region of the present-day OMZ and high surface-water productivity. The benthic foraminiferal δ13C values, which indicate millennial-scale fluctuations of nutrient contents at the sediment-water interface, were 0.48‰ lower during the last glacial maximum (LGM) than during the late Holocene. These results do not indicate the formation of glacial intermediate waters of subarctic Pacific origin, but rather the large contribution of high-nutrient water masses such as the Antarctic Intermediate Water, implying that the regional circulation pattern during the LGM was similar to that of modern times. Benthic foraminiferal assemblages underwent major changes in response to changes in dissolved oxygen concentrations in ocean floor sediments. The lowest oxygen and highest nutrient conditions, marked by dysoxic taxa and negative values of benthic foraminiferal δ13C, occurred during the Bølling/Allerød (B/A) and Pre-Boreal warming events. Dysoxic conditions in this region during these intervals were possibly caused by high surface-water productivity at times of reduced intermediate-water ventilation in the northwestern Pacific. The benthic assemblages show dysoxic events on approx. 100- to 200-year cycles during the B/A, reflecting centennial-scale productivity changes related to freshwater cycles and surface-water circulation in the North Pacific.

PALADYN v1.0, a comprehensive land surface-vegetation-carbon cycle model of intermediate complexity

NASA Astrophysics Data System (ADS)

Willeit, Matteo; Ganopolski, Andrey

2016-10-01

PALADYN is presented; it is a new comprehensive and computationally efficient land surface-vegetation-carbon cycle model designed to be used in Earth system models of intermediate complexity for long-term simulations and paleoclimate studies. The model treats in a consistent manner the interaction between atmosphere, terrestrial vegetation and soil through the fluxes of energy, water and carbon. Energy, water and carbon are conserved. PALADYN explicitly treats permafrost, both in physical processes and as an important carbon pool. It distinguishes nine surface types: five different vegetation types, bare soil, land ice, lake and ocean shelf. Including the ocean shelf allows the treatment of continuous changes in sea level and shelf area associated with glacial cycles. Over each surface type, the model solves the surface energy balance and computes the fluxes of sensible, latent and ground heat and upward shortwave and longwave radiation. The model includes a single snow layer. Vegetation and bare soil share a single soil column. The soil is vertically discretized into five layers where prognostic equations for temperature, water and carbon are consistently solved. Phase changes of water in the soil are explicitly considered. A surface hydrology module computes precipitation interception by vegetation, surface runoff and soil infiltration. The soil water equation is based on Darcy's law. Given soil water content, the wetland fraction is computed based on a topographic index. The temperature profile is also computed in the upper part of ice sheets and in the ocean shelf soil. Photosynthesis is computed using a light use efficiency model. Carbon assimilation by vegetation is coupled to the transpiration of water through stomatal conductance. PALADYN includes a dynamic vegetation module with five plant functional types competing for the grid cell share with their respective net primary productivity. PALADYN distinguishes between mineral soil carbon, peat carbon, buried

The effect of oxaloacetic acid on tyrosinase activity and structure: Integration of inhibition kinetics with docking simulation.

PubMed

Gou, Lin; Lee, Jinhyuk; Hao, Hao; Park, Yong-Doo; Zhan, Yi; Lü, Zhi-Rong

2017-08-01

Oxaloacetic acid (OA) is naturally found in organisms and well known as an intermediate of citric acid cycle producing ATP. We evaluated the effects of OA on tyrosinase activity and structure via integrating methods of enzyme kinetics and computational simulations. OA was found to be a reversible inhibitor of tyrosinase and its induced mechanism was the parabolic non-competitive inhibition type (IC 50 =17.5±0.5mM and K i =6.03±1.36mM). Kinetic measurements by real-time interval assay showed that OA induced multi-phasic inactivation process composing with fast (k 1 ) and slow (k 2 ) phases. Spectrofluorimetry studies showed that OA mainly induced regional changes in the active site of tyrosinase accompanying with hydrophobic disruption at high dose. The computational docking simulations further revealed that OA could interact with several residues near the tyrosinase active site pocket such as HIS61, HIS259, HIS263, and VAL283. Our study provides insight into the mechanism by which energy producing intermediate such as OA inhibit tyrosinase and OA is a potential natural anti-pigmentation agent. Copyright © 2017 Elsevier B.V. All rights reserved.

Efficient synthesis and physicochemical characterization of natural danshensu, its S isomer and intermediates thereof

NASA Astrophysics Data System (ADS)

Sidoryk, Katarzyna; Filip, Katarzyna; Cmoch, Piotr; Łaszcz, Marta; Cybulski, Marcin

2018-02-01

The synthesis and molecular structure details of R- 3,4-dihydroxyphenyl lactic acid (danshensu) and related compounds, i.e. S isomer and the key intermediates have been described. Danshensu is an important water soluble phenolic acid of Salvia miltiorrhiza herb (danshen or red sag) with numerous applications in traditional Chinese medicine (TCM). Our synthetic approach was based on the Knoevenagel condensation of the protected 3,4-dihydroxybenzaldehyd and Meldrum acid derivative, followed by asymmetric Sharples dihydroxylation, reductive mono dehydroxylation and final deprotection. All compounds were characterized by various spectroscopic techniques: 1H-, 13C- magnetic resonance (NMR); Fourier-transformed infrared (FTIR); Raman, HR mass spectroscopy. For the determination of compound optical purities original HPLC methods were developed which allowed for the efficient resolution of danshensu R and S enantiomers as well as its intermediate enantiomers, using commercially available chiral stationary phases. Furthermore, in order to better understand danshensu specificity as a potential API in drug formulation, the physicochemical properties of the compounds were studied by thermal analysis, including differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA).

The development of Neoechinorhynchus buttnerae (Eoacanthocephala: Neoechinorhynchidae) in its intermediate host Cypridopsis vidua in Brazil.

PubMed

Lourenço, Felipe de Sousa; Morey, Germán Augusto Murrieta; Malta, José Celso de Oliveira

2018-06-26

The family Neoechinorhynchidae includes seven species of Neoechinorhynchus from freshwater fishes of Brazil. Although several Neoechinorhynchus species are cited infecting different fish species in Brazil, there is a lack of information concerning to their life cycle and the identification of the intermediate hosts. Thus, the aim of the present study was to describe the development of Neoechinorhynchus buttnerae in its intermediate host collected in a fish farm located in Rio Preto da Eva, Amazonas, Brazil. To verify the presence of N. buttnerae in the fish pond, twenty Colossoma macropomum were captured and analyzed, being corroborated the presence of this parasite species. Samples of plankton were also collected, finding the ostracod Cypridopsis vidua as the intermediate host. For the description of the larvae development, a laboratory experimental procedure was conducted by feeding the collected ostracods with the eggs of the adult specimens taken from the sampled fish. To observe the stages of development an artificial hatch was performed. Every stage of development was photographed, measured, drawn and described. The time of development of the immature stages of N. buttnerae was 29 days, reporting the stages: acanthor, acanthella (with eight developmental changes) and cystacanth. As high infections by N. buttnerae causes morphological damages to the intestine and may compromise the quality of C. macropomum and in consequence the production of fish farmers in the Brazilian Amazon region, the knowledge of its intermediate host and the understanding of its life cycle represents a useful information to prevent and combat infections by this parasite.

Analysis of trace inorganic anions in weak acid salts by single pump cycling-column-switching ion chromatography.

PubMed

Huang, Zhongping; Ni, Chengzhu; Zhu, Zhuyi; Pan, Zaifa; Wang, Lili; Zhu, Yan

2015-05-01

The application of ion chromatography with the single pump cycling-column-switching technique was described for the analysis of trace inorganic anions in weak acid salts within a single run. Due to the hydrogen ions provided by an anion suppressor electrolyzing water, weak acid anions could be transformed into weak acids, existing as molecules, after passing through the suppressor. Therefore, an anion suppressor and ion-exclusion column were adopted to achieve on-line matrix elimination of weak acid anions with high concentration for the analysis of trace inorganic anions in weak acid salts. A series of standard solutions consisting of target anions of various concentrations from 0.005 to 10 mg/L were analyzed, with correlation coefficients r ≥ 0.9990. The limits of detection were in the range of 0.67 to 1.51 μg/L, based on the signal-to-noise ratio of 3 and a 25 μL injection volume. Relative standard deviations for retention time, peak area, and peak height were all less than 2.01%. A spiking study was performed with satisfactory recoveries between 90.3 and 104.4% for all anions. The chromatographic system was successfully applied to the analysis of trace inorganic anions in five weak acid salts. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Levels of Arabidopsis thaliana Leaf Phosphatidic Acids, Phosphatidylserines, and Most Trienoate-Containing Polar Lipid Molecular Species Increase during the Dark Period of the Diurnal Cycle.

PubMed

Maatta, Sara; Scheu, Brad; Roth, Mary R; Tamura, Pamela; Li, Maoyin; Williams, Todd D; Wang, Xuemin; Welti, Ruth

2012-01-01

Previous work has demonstrated that plant leaf polar lipid fatty acid composition varies during the diurnal (dark-light) cycle. Fatty acid synthesis occurs primarily during the light, but fatty acid desaturation continues in the absence of light, resulting in polyunsaturated fatty acids reaching their highest levels toward the end of the dark period. In this work, Arabidopsis thaliana were grown at constant (21°C) temperature with 12-h light and 12-h dark periods. Collision induced dissociation time-of-flight mass spectrometry (MS) demonstrated that 16:3 and 18:3 fatty acid content in membrane lipids of leaves are higher at the end of the dark than at the end of the light period, while 16:1, 16:2, 18:0, and 18:1 content are higher at the end of the light period. Lipid profiling of membrane galactolipids, phospholipids, and lysophospholipids by electrospray ionization triple quadrupole MS indicated that the monogalactosyldiacylglycerol, phosphatidylglycerol, and phosphatidylcholine classes include molecular species whose levels are highest at end of the light period and others that are highest at the end of the dark period. The levels of phosphatidic acid (PA) and phosphatidylserine classes were higher at the end of the dark period, and molecular species within these classes either followed the class pattern or were not significantly changed in the diurnal cycle. Phospholipase D (PLD) is a family of enzymes that hydrolyzes phospholipids to produce PA. Analysis of several PLD mutant lines suggests that PLDζ2 and possibly PLDα1 may contribute to diurnal cycling of PA. The polar lipid compositional changes are considered in relation to recent data that demonstrate phosphatidylcholine acyl editing.

"Panta rhei": Perpetual cycling of the keratin cytoskeleton.

PubMed

Leube, Rudolf E; Moch, Marcin; Kölsch, Anne; Windoffer, Reinhard

2011-01-01

The filamentous cytoskeletal systems fulfil seemingly incompatible functions by maintaining a stable scaffolding to ensure tissue integrity and simultaneously facilitating rapid adaptation to intracellular processes and environmental stimuli. This paradox is particularly obvious for the abundant keratin intermediate filaments in epithelial tissues. The epidermal keratin cytoskeleton, for example, supports the protective and selective barrier function of the skin while enabling rapid growth and remodelling in response to physical, chemical and microbial challenges. We propose that these dynamic properties are linked to the perpetual re-cycling of keratin intermediate filaments that we observe in cultured cells. This cycle of assembly and disassembly is independent of protein biosynthesis and consists of distinct, temporally and spatially defined steps. In this way, the keratin cytoskeleton remains in constant motion but stays intact and is also able to restructure rapidly in response to specific regulatory cues as is needed, e.g., during division, differentiation and wound healing.

Diet-induced milk fat depression is associated with alterations in ruminal biohydrogenation pathways and formation of novel fatty acid intermediates in lactating cows.

PubMed

Ventto, Laura; Leskinen, Heidi; Kairenius, Piia; Stefański, Tomasz; Bayat, Ali R; Vilkki, Johanna; Shingfield, Kevin J

2017-02-01

The biohydrogenation theory of milk fat depression (MFD) attributes decreases in milk fat in cows to the formation of specific fatty acids (FA) in the rumen. Trans-10, cis-12-CLA is the only biohydrogenation intermediate known to inhibit milk fat synthesis, but it is uncertain if increased ruminal synthesis is the sole explanation of MFD. Four lactating cows were used in a 4×4 Latin square with a 2×2 factorial arrangement of treatments and 35-d experimental periods to evaluate the effect of diets formulated to cause differences in ruminal lipid metabolism and milk fat synthesis on the flow of FA and dimethyl acetal at the omasum. Treatments comprised total mixed rations based on grass silage with a forage:concentrate ratio of 35:65 or 65:35 containing 0 or 50 g/kg sunflower oil (SO). Supplementing the high-concentrate diet with SO lowered milk fat synthesis from -20·2 to -31·9 % relative to other treatments. Decreases in milk fat were accompanied by alterations in ruminal biohydrogenation favouring the trans-10 pathway and an increase in the formation of specific intermediates including trans-4 to trans-10-18 : 1, trans-8, trans-10-CLA, trans-9, cis-11-CLA and trans-10, cis-15-18 : 2. Flow of trans-10, cis-12-CLA at the omasum was greater on high- than low-concentrate diets but unaffected by SO. In conclusion, ruminal trans-10, cis-12-CLA formation was not increased on a diet causing MFD suggesting that other biohydrogenation intermediates or additional mechanisms contribute to the regulation of fat synthesis in the bovine mammary gland.

Free fatty acids block glucose-induced β-cell proliferation in mice by inducing cell cycle inhibitors p16 and p18.

PubMed

Pascoe, Jordan; Hollern, Douglas; Stamateris, Rachel; Abbasi, Munira; Romano, Lia C; Zou, Baobo; O'Donnell, Christopher P; Garcia-Ocana, Adolfo; Alonso, Laura C

2012-03-01

Pancreatic β-cell proliferation is infrequent in adult humans and is not increased in type 2 diabetes despite obesity and insulin resistance, suggesting the existence of inhibitory factors. Free fatty acids (FFAs) may influence proliferation. In order to test whether FFAs restrict β-cell proliferation in vivo, mice were intravenously infused with saline, Liposyn II, glucose, or both, continuously for 4 days. Lipid infusion did not alter basal β-cell proliferation, but blocked glucose-stimulated proliferation, without inducing excess β-cell death. In vitro exposure to FFAs inhibited proliferation in both primary mouse β-cells and in rat insulinoma (INS-1) cells, indicating a direct effect on β-cells. Two of the fatty acids present in Liposyn II, linoleic acid and palmitic acid, both reduced proliferation. FFAs did not interfere with cyclin D2 induction or nuclear localization by glucose, but increased expression of inhibitor of cyclin dependent kinase 4 (INK4) family cell cycle inhibitors p16 and p18. Knockdown of either p16 or p18 rescued the antiproliferative effect of FFAs. These data provide evidence for a novel antiproliferative form of β-cell glucolipotoxicity: FFAs restrain glucose-stimulated β-cell proliferation in vivo and in vitro through cell cycle inhibitors p16 and p18. If FFAs reduce proliferation induced by obesity and insulin resistance, targeting this pathway may lead to new treatment approaches to prevent diabetes.

Transcriptional Orchestration of the Global Cellular Response of a Model Pennate Diatom to Diel Light Cycling under Iron Limitation.

PubMed

Smith, Sarah R; Gillard, Jeroen T F; Kustka, Adam B; McCrow, John P; Badger, Jonathan H; Zheng, Hong; New, Ashley M; Dupont, Chris L; Obata, Toshihiro; Fernie, Alisdair R; Allen, Andrew E

2016-12-01

Environmental fluctuations affect distribution, growth and abundance of diatoms in nature, with iron (Fe) availability playing a central role. Studies on the response of diatoms to low Fe have either utilized continuous (24 hr) illumination or sampled a single time of day, missing any temporal dynamics. We profiled the physiology, metabolite composition, and global transcripts of the pennate diatom Phaeodactylum tricornutum during steady-state growth at low, intermediate, and high levels of dissolved Fe over light:dark cycles, to better understand fundamental aspects of genetic control of physiological acclimation to growth under Fe-limitation. We greatly expand the catalog of genes involved in the low Fe response, highlighting the importance of intracellular trafficking in Fe-limited diatoms. P. tricornutum exhibited transcriptomic hallmarks of slowed growth leading to prolonged periods of cell division/silica deposition, which could impact biogeochemical carbon sequestration in Fe-limited regions. Light harvesting and ribosome biogenesis transcripts were generally reduced under low Fe while transcript levels for genes putatively involved in the acquisition and recycling of Fe were increased. We also noted shifts in expression towards increased synthesis and catabolism of branched chain amino acids in P. tricornutum grown at low Fe whereas expression of genes involved in central core metabolism were relatively unaffected, indicating that essential cellular function is protected. Beyond the response of P. tricornutum to low Fe, we observed major coordinated shifts in transcript control of primary and intermediate metabolism over light:dark cycles which contribute to a new view of the significance of distinctive diatom pathways, such as mitochondrial glycolysis and the ornithine-urea cycle. This study provides new insight into transcriptional modulation of diatom physiology and metabolism across light:dark cycles in response to Fe availability, providing mechanistic

Transcriptional Orchestration of the Global Cellular Response of a Model Pennate Diatom to Diel Light Cycling under Iron Limitation

PubMed Central

McCrow, John P.; Badger, Jonathan H.; Zheng, Hong; New, Ashley M.; Dupont, Chris L.; Obata, Toshihiro; Fernie, Alisdair R.; Allen, Andrew E.

2016-01-01

Environmental fluctuations affect distribution, growth and abundance of diatoms in nature, with iron (Fe) availability playing a central role. Studies on the response of diatoms to low Fe have either utilized continuous (24 hr) illumination or sampled a single time of day, missing any temporal dynamics. We profiled the physiology, metabolite composition, and global transcripts of the pennate diatom Phaeodactylum tricornutum during steady-state growth at low, intermediate, and high levels of dissolved Fe over light:dark cycles, to better understand fundamental aspects of genetic control of physiological acclimation to growth under Fe-limitation. We greatly expand the catalog of genes involved in the low Fe response, highlighting the importance of intracellular trafficking in Fe-limited diatoms. P. tricornutum exhibited transcriptomic hallmarks of slowed growth leading to prolonged periods of cell division/silica deposition, which could impact biogeochemical carbon sequestration in Fe-limited regions. Light harvesting and ribosome biogenesis transcripts were generally reduced under low Fe while transcript levels for genes putatively involved in the acquisition and recycling of Fe were increased. We also noted shifts in expression towards increased synthesis and catabolism of branched chain amino acids in P. tricornutum grown at low Fe whereas expression of genes involved in central core metabolism were relatively unaffected, indicating that essential cellular function is protected. Beyond the response of P. tricornutum to low Fe, we observed major coordinated shifts in transcript control of primary and intermediate metabolism over light:dark cycles which contribute to a new view of the significance of distinctive diatom pathways, such as mitochondrial glycolysis and the ornithine-urea cycle. This study provides new insight into transcriptional modulation of diatom physiology and metabolism across light:dark cycles in response to Fe availability, providing mechanistic

Reactions of Criegee Intermediates with Non-Water Greenhouse Gases: Implications for Metal Free Chemical Fixation of Carbon Dioxide.

PubMed

Kumar, Manoj; Francisco, Joseph S

2017-09-07

High-level theoretical calculations suggest that a Criegee intermediate preferably interacts with carbon dioxide compared to two other greenhouse gases, nitrous oxide and methane. The results also suggest that the interaction between Criegee intermediates and carbon dioxide involves a cycloaddition reaction, which results in the formation of a cyclic carbonate-type adduct with a barrier of 6.0-14.0 kcal/mol. These results are in contrast to a previous assumption that the reaction occurs barrierlessly. The subsequent decomposition of the cyclic adduct into formic acid and carbon dioxide follows both concerted and stepwise mechanisms. The latter mechanism has been overlooked previously. Under formic acid catalysis, the concerted decomposition of the cyclic carbonate may be favored under tropospheric conditions. Considering that there is a strong nexus between carbon dioxide levels in the atmosphere and global warming, the high reactivity of Criegee intermediates could be utilized for designing efficient carbon capture technologies.

Interplay between cell cycle and autophagy induced by boswellic acid analog

PubMed Central

Pathania, Anup S.; Guru, Santosh K.; Kumar, Suresh; Kumar, Ashok; Ahmad, Masroor; Bhushan, Shashi; Sharma, Parduman R.; Mahajan, Priya; Shah, Bhahwal A.; Sharma, Simmi; Nargotra, Amit; Vishwakarma, Ram; Korkaya, Hasan; Malik, Fayaz

2016-01-01

In this study, we investigated the role of autophagy induced by boswellic acid analog BA145 on cell cycle progression in pancreatic cancer cells. BA145 induced robust autophagy in pancreatic cancer cell line PANC-1 and exhibited cell proliferation inhibition by inducing cells to undergo G2/M arrest. Inhibition of G2/M progression was associated with decreased expression of cyclin A, cyclin B, cyclin E, cdc2, cdc25c and CDK-1. Pre-treatment of cells with autophagy inhibitors or silencing the expression of key autophagy genes abrogated BA145 induced G2/M arrest and downregulation of cell cycle regulatory proteins. It was further observed that BA145 induced autophagy by targeting mTOR kinase (IC50 1 μM), leading to reduced expression of p-mTOR, p-p70S6K (T389), p-4EBP (T37/46) and p-S6 (S240/244). Notably, inhibition of mTOR signalling by BA145 was followed by attendant activation of AKT and its membrane translocation. Inhibition of Akt through pharmacological inhibitors or siRNAs enhanced BA145 mediated autophagy, G2/M arrest and reduced expression of G2/M regulators. Further studies revealed that BA145 arbitrated inhibition of mTOR led to the activation of Akt through IGFR/PI3k/Akt feedback loop. Intervention in IGFR/PI3k/Akt loop further depreciated Akt phosphorylation and its membrane translocation that culminates in augmented autophagy with concomitant G2/M arrest and cell death. PMID:27680387

Infrared and Visible Absolute and Difference Spectra of Bacteriorhodopsin Photocycle Intermediates

PubMed Central

Hendler, Richard W.; Meuse, Curtis W.; Braiman, Mark S.; Smith, Paul D.; Kakareka, John W.

2014-01-01

We have used new kinetic fitting procedures to obtain IR absolute spectra for intermediates of the main bacteriorhodopsin (bR) photocycle(s). The linear algebra-based procedures of Hendler et al. (2001) J. Phys. Chem. B, 105, 3319–3228, for obtaining clean absolute visible spectra of bR photocycle intermediates, were adapted for use with IR data. This led to isolation, for the first time, of corresponding clean absolute IR spectra, including the separation of the M intermediate into its MF and MS components from parallel photocycles. This in turn permitted the computation of clean IR difference spectra between pairs of successive intermediates, allowing for the most rigorous analysis to date of changes occurring at each step of the photocycle. The statistical accuracy of the spectral calculation methods allows us to identify, with great confidence, new spectral features. One of these is a very strong differential IR band at 1650 cm−1 for the L intermediate at room temperature that is not present in analogous L spectra measured at cryogenic temperatures. This band, in one of the noisiest spectral regions, has not been identified in any previous time-resolved IR papers, although retrospectively it is apparent as one of the strongest L absorbance changes in their raw data, considered collectively. Additionally, our results are most consistent with Arg82 as the primary proton-release group (PRG), rather than a protonated water cluster or H-bonded grouping of carboxylic residues. Notably, the Arg82 deprotonation occurs exclusively in the MF pathway of the parallel cycles model of the photocycle. PMID:21929858

Oxaloacetate-to-malate conversion by mineral photoelectrochemistry: implications for the viability of the reductive tricarboxylic acid cycle in prebiotic chemistry

NASA Astrophysics Data System (ADS)

Guzman, Marcelo I.; Martin, Scot T.

2008-10-01

The carboxylic acids produced by the reductive tricarboxylic acid (rTCA) cycle are possibly a biosynthetic core of initial life, although several steps such as the reductive kinetics of oxaloacetate (OAA) to malate (MA) are problematic by conventional chemical routes. In this context, we studied the kinetics of this reaction as promoted by ZnS mineral photoelectrochemistry. The quantum efficiency φMA of MA production from the photoelectrochemical reduction of OAA followed φMA=0.13 [OAA] (2.1×10-3+[OAA])-1 and was independent of temperature (5 to 50°C). To evaluate the importance of this forward rate under a prebiotic scenario, we also studied the temperature-dependent rate of the backward thermal decarboxylation of OAA to pyruvate (PA), which followed an Arrhenius behavior as log (k-2)=11.74 4956/T, where k-2 is in units of s-1. These measured rates were employed in conjunction with the indirectly estimated carboxylation rate of PA to OAA to assess the possible importance of mineral photoelectrochemistry in the conversion of OAA to MA under several scenarios of prebiotic conditions on early Earth. As an example, our analysis shows that there is 90% efficiency with a forward velocity of 3 yr/cycle for the OAA→MA step of the rTCA cycle at 280 K. Efficiency and velocity both decrease for increasing temperature. These results suggest high viability for mineral photoelectrochemistry as an enzyme-free engine to drive the rTCA cycle through the early aeons of early Earth, at least for the investigated OAA→MA step.

Heteromeric amino acid transporters. In search of the molecular bases of transport cycle mechanisms.

PubMed

Palacín, Manuel; Errasti-Murugarren, Ekaitz; Rosell, Albert

2016-06-15

Heteromeric amino acid transporters (HATs) are relevant targets for structural studies. On the one hand, HATs are involved in inherited and acquired human pathologies. On the other hand, these molecules are the only known examples of solute transporters composed of two subunits (heavy and light) linked by a disulfide bridge. Unfortunately, structural knowledge of HATs is scarce and limited to the atomic structure of the ectodomain of a heavy subunit (human 4F2hc-ED) and distant prokaryotic homologues of the light subunits that share a LeuT-fold. Recent data on human 4F2hc/LAT2 at nanometer resolution revealed 4F2hc-ED positioned on top of the external loops of the light subunit LAT2. Improved resolution of the structure of HATs, combined with conformational studies, is essential to establish the structural bases for light subunit recognition and to evaluate the functional relevance of heavy and light subunit interactions for the amino acid transport cycle. © 2016 Authors; published by Portland Press Limited.

Nicotinic Acid Metabolism, V. A Cobamide Coenzyme-Dependent Conversion of α-Methyleneglutaric Acid to Dimethylmaleic Acid

PubMed Central

Kung, H. F.; Cederbaum, S.; Tsai, L.; Stadtman, T. C.

1970-01-01

A new B12-coenzyme-dependent isomerization, catalyzed by extracts of a nicotinate-fermenting clostridium, results in the conversion of α-methyleneglutaric acid to dimethylmaleic acid. These two acids are intermediates in the multistep anaerobic process wherein nicotinate is converted, ultimately, to one mole each of propionate, acetate, carbon dioxide, and ammonia. Dimethylmaleic acid reacts in its anhydride form with 2,4-dinitrophenylhydrazine to form N-2′,4′-dinitrophenyl-anilino-3,4-dimethylmaleimide. The characteristic reddish color exhibited by the latter derivative in alkaline solution serves as a convenient quantitative assay for dimethylmaleic acid. Comparison of the 2,4-dinitrophenylhydrazine derivatives of the product of the enzymic reaction and of synthetic dimethylmaleic anhydride showed them to be identical in every respect. PMID:5266166

Shifting patterns of nitrogen excretion and amino acid catabolism capacity during the life cycle of the sea lamprey (Petromyzon marinus).

PubMed

Wilkie, Michael P; Claude, Jaime F; Cockshutt, Amanda; Holmes, John A; Wang, Yuxiang S; Youson, John H; Walsh, Patrick J

2006-01-01

The jawless fish, the sea lamprey (Petromyzon marinus), spends part of its life as a burrow-dwelling, suspension-feeding larva (ammocoete) before undergoing a metamorphosis into a free swimming, parasitic juvenile that feeds on the blood of fishes. We predicted that animals in this juvenile, parasitic stage have a great capacity for catabolizing amino acids when large quantities of protein-rich blood are ingested. The sixfold to 20-fold greater ammonia excretion rates (J(Amm)) in postmetamorphic (nonfeeding) and parasitic lampreys compared with ammocoetes suggested that basal rates of amino acid catabolism increased following metamorphosis. This was likely due to a greater basal amino acid catabolizing capacity in which there was a sixfold higher hepatic glutamate dehydrogenase (GDH) activity in parasitic lampreys compared with ammocoetes. Immunoblotting also revealed that GDH quantity was 10-fold and threefold greater in parasitic lampreys than in ammocoetes and upstream migrant lampreys, respectively. Higher hepatic alanine and aspartate aminotransferase activities in the parasitic lampreys also suggested an enhanced amino acid catabolizing capacity in this life stage. In contrast to parasitic lampreys, the twofold larger free amino acid pool in the muscle of upstream migrant lampreys confirmed that this period of natural starvation is accompanied by a prominent proteolysis. Carbamoyl phosphate synthetase III was detected at low levels in the liver of parasitic and upstream migrant lampreys, but there was no evidence of extrahepatic (muscle, intestine) urea production via the ornithine urea cycle. However, detection of arginase activity and high concentrations of arginine in the liver at all life stages examined infers that arginine hydrolysis is an important source of urea. We conclude that metamorphosis is accompanied by a metabolic reorganization that increases the capacity of parasitic sea lampreys to catabolize intermittently large amino acid loads arising

Agarose Gel Electrophoresis Reveals Structural Fluidity of a Phage T3 DNA Packaging Intermediate

PubMed Central

Serwer, Philip; Wright, Elena T.

2012-01-01

We find a new aspect of DNA packaging-associated structural fluidity for phage T3 capsids. The procedure is (1) glutaraldehyde cross-linking of in vivo DNA packaging intermediates for stabilization of structure and then (2) determining of effective radius by two-dimensional agarose gel electrophoresis (2d-AGE). The intermediates are capsids with incompletely packaged DNA (ipDNA) and without an external DNA segment; these intermediates are called ipDNA-capsids. We initially increase production of ipDNA-capsids by raising NaCl concentration during in vivo DNA packaging. By 2d-AGE, we find a new state of contracted shell for some particles of one previously identified ipDNA-capsid. The contracted shell-state is found when ipDNA length/mature DNA length (F) is above 0.17, but not at lower F. Some contracted-shell ipDNA-capsids have the phage tail; others do not. The contracted-shell ipDNA-capsids are explained by premature DNA maturation cleavage that makes accessible a contracted-shell intermediate of a cycle of the T3 DNA packaging motor. The analysis of ipDNA-capsids, rather than intermediates with uncleaved DNA, provides a simplifying strategy for a complete biochemical analysis of in vivo DNA packaging. PMID:22222979

Phosphatidylcholine and the CDP-Choline Cycle

PubMed Central

Fagone, Paolo; Jackowski, Suzanne

2012-01-01

The CDP-choline pathway of phosphatidylcholine (PtdCho) biosynthesis was first described more than 50 years ago. Investigation of the CDP-choline pathway in yeast provides a basis for understanding the CDP-choline pathway in mammals. PtdCho is considered as an intermediate in a cycle of synthesis and degradation, and the activity of a CDP-choline cycle is linked to subcellular membrane lipid movement. The components of the mammalian CDP-choline pathway include choline transport, choline kinase, phosphocholine cytidylyltransferase, and choline phosphotransferase activities. The protein isoforms and biochemical mechanisms of regulation of the pathway enzymes are related to their cell and tissue-specific functions. Regulated PtdCho turnover mediated by phospholipases or neuropathy target esterase participates in the mammalian CDP-choline cycle. Knockout mouse models define the biological functions of the CDP-choline cycle in mammalian cells and tissues. This article is part of a Special Issue entitled Phospholipids and Phospholipid Metabolism. PMID:23010477

Metabolically based liver damage pathophysiology in patients with urea cycle disorders - A new hypothesis.

PubMed

Ivanovski, Ivan; Ješić, Miloš; Ivanovski, Ana; Garavelli, Livia; Ivanovski, Petar

2017-11-28

The underlying pathophysiology of liver dysfunction in urea cycle disorders (UCDs) is still largely elusive. There is some evidence that the accumulation of urea cycle (UC) intermediates are toxic for hepatocyte mitochondria. It is possible that liver injury is directly caused by the toxicity of ammonia. The rarity of UCDs, the lack of checking of iron level in these patients, superficial knowledge of UC and an underestimation of the metabolic role of fumaric acid, are the main reasons that are responsible for the incomprehension of the mechanism of liver injury in patients suffering from UCDs. Owing to our routine clinical practice to screen for iron overload in severely ill neonates, with the focus on the newborns suffering from acute liver failure, we report a case of citrullinemia with neonatal liver failure and high blood parameters of iron overload. We hypothesize that the key is in the decreased-deficient fumaric acid production in the course of UC in UCDs that causes several sequentially intertwined metabolic disturbances with final result of liver iron overload. The presented hypothesis could be easily tested by examining the patients suffering from UCDs, for liver iron overload. This could be easily performed in countries with a high population and comprehensive national register for inborn errors of metabolism. Providing the hypothesis is correct, neonatal liver damage in patients having UCD can be prevented by the supplementation of pregnant women with fumaric or succinic acid, prepared in the form of iron supplementation pills. After birth, liver damage in patients having UCDs can be prevented by supplementation of these patients with zinc fumarate or zinc succinylate, as well.

Tetrapyrrole signal as a cell-cycle coordinator from organelle to nuclear DNA replication in plant cells

PubMed Central

Kobayashi, Yuki; Kanesaki, Yu; Tanaka, Ayumi; Kuroiwa, Haruko; Kuroiwa, Tsuneyoshi; Tanaka, Kan

2009-01-01

Eukaryotic cells arose from an ancient endosymbiotic association of prokaryotes, with plant cells harboring 3 genomes as the remnants of such evolution. In plant cells, plastid and mitochondrial DNA replication [organelle DNA replication (ODR)] occurs in advance of the subsequent cell cycles composed of nuclear DNA replication (NDR) and cell division. However, the mechanism by which replication of these genomes with different origins is coordinated is largely unknown. Here, we show that NDR is regulated by a tetrapyrrole signal in plant cells, which has been suggested as an organelle-to-nucleus retrograde signal. In synchronized cultures of the primitive red alga Cyanidioschyzon merolae, specific inhibition of A-type cyclin-dependent kinase (CDKA) prevented NDR but not ODR after onset of the cell cycle. In contrast, inhibition of ODR by nalidixic acid also resulted in inhibition of NDR, indicating a strict dependence of NDR on ODR. The requirement of ODR for NDR was bypassed by addition of the tetrapyrrole intermediates protoporphyrin IX (ProtoIX) or Mg-ProtoIX, both of which activated CDKA without inducing ODR. This scheme was also observed in cultured tobacco cells (BY-2), where inhibition of ODR by nalidixic acid prevented CDKA activation and NDR, and these inhibitions were circumvented by Mg-ProtoIX without inducing ODR. We thus show that tetrapyrrole-mediated organelle–nucleus replicational coupling is an evolutionary conserved process among plant cells. PMID:19141634

Transport and cycling of iron and hydrogen peroxide in a freshwater stream: Influence of organic acids

USGS Publications Warehouse

Scott, Durelle T.; Runkel, Robert L.; McKnight, Diane M.; Voelker, Bettina M.; Kimball, Briant A.; Carraway, Elizabeth R.

2003-01-01

An in-stream injection of two dissolved organic acids (phthalic and aspartic acids) was performed in an acidic mountain stream to assess the effects of organic acids on Fe photoreduction and H2O2 cycling. Results indicate that the fate of Fe is dependent on a net balance of oxidative and reductive processes, which can vary over a distance of several meters due to changes in incident light and other factors. Solution phase photoreduction rates were high in sunlit reaches and were enhanced by the organic acid addition but were also limited by the amount of ferric iron present in the water column. Fe oxide photoreduction from the streambed and colloids within the water column resulted in an increase in the diurnal load of total filterable Fe within the experimental reach, which also responded to increases in light and organic acids. Our results also suggest that Fe(II) oxidation increased in response to the organic acids, with the result of offsetting the increase in Fe(II) from photoreductive processes. Fe(II) was rapidly oxidized to Fe(III) after sunset and during the day within a well-shaded reach, presumably through microbial oxidation. H2O 2, a product of dissolved organic matter photolysis, increased downstream to maximum concentrations of 0.25 ??M midday. Kinetic calculations show that the buildup of H2O2 is controlled by reaction with Fe(III), but this has only a small effect on Fe(II) because of the small formation rates of H2O2 compared to those of Fe(II). The results demonstrate the importance of incorporating the effects of light and dissolved organic carbon into Fe reactive transport models to further our understanding of the fate of Fe in streams and lakes.

NUCLEIC ACID AND PROTEIN METABOLISM DURING THE MITOTIC CYCLE IN VICIA FABA

PubMed Central

Woodard, John; Rasch, Ellen; Swift, Hewson

1961-01-01

In order to investigate some of the cytochemical processes involved in interphase growth and culminating in cell division, a combined autoradiographic and microphotometric study of nucleic acids and proteins was undertaken on statistically seriated cells of Vicia faba root meristems. Adenine-8-C14 and uridine-H3 were used as ribonucleic acid (RNA) precursors, thymidine-H3 as a deoxyribonucleic acid (DNA) precursor, and phenylalanine-3-C14 as a protein precursor. Stains used in microphotometry were Feulgen (DNA), azure B (RNA), pH 2.0 fast green (total protein), and pH 8.1 fast green (histone). The autoradiographic data (representing rate of incorporation per organelle) and the microphotometric data (representing changes in amounts of the various components) indicate that the mitotic cycle may be divided into several metabolic phases, three predominantly anabolic (net increase), and a fourth phase predominantly catabolic (net decrease). The anabolic periods are: 1. Telophase to post-telophase during which there are high rates of accumulation of cytoplasmic and nucleolar RNA and nucleolar and chromosomal total protein. 2. Post-telophase to preprophase characterized by histone synthesis and a diphasic synthesis of DNA with the peak of synthesis at mid-interphase and a minor peak just preceding prophase. The minor peak is coincident with a relatively localized DNA synthesis in several chromosomal regions. This period is also characterized by minimal accumulations of cytoplasmic RNA and chromosomal and nucleolar total protein and RNA. 3. Preprophase to prophase in which there are again high rates of accumulation of cytoplasmic RNA, and nucleolar and chromosomal total protein and RNA. The catabolic phase is: 4. The mitotic division during which there are marked losses of cytoplasmic RNA and chromosomal and nucleolar total protein and RNA. PMID:13786522

Glucose and amino acid metabolism in rat brain during sustained hypoglycemia

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wong, K.L.; Tyce, G.M.

1983-04-01

The metabolism of glucose in brains during sustained hypoglycemia was studied. (U-/sup 14/C)Glucose (20 microCi) was injected into control rats, and into rats at 2.5 hr after a bolus injection of 2 units of insulin followed by a continuous infusion of 0.2 units/100 g rat/hr. This regimen of insulin injection was found to result in steady-state plasma glucose levels between 2.5 and 3.5 mumol per ml. In the brains of control rats carbon was transferred rapidly from glucose to glutamate, glutamine, gamma-aminobutyric acid and aspartate and this carbon was retained in the amino acids for at least 60 min. Inmore » the brains of hypoglycemic rats, the conversion of carbon from glucose to amino acids was increased in the first 15 min after injection. After 15 min, the specific activity of the amino acids decreased in insulin-treated rats but not in the controls. The concentrations of alanine, glutamate, and gamma-amino-butyric acid decreased, and the concentration of aspartate increased, in the brains of the hypoglycemic rats. The concentration of pyridoxal-5'-phosphate, a cofactor in many of the reactions whereby these amino acids are formed from tricarboxylic acid cycle intermediates, was less in the insulin-treated rats than in the controls. These data provide evidence that glutamate, glutamine, aspartate, and GABA can serve as energy sources in brain during insulin-induced hypoglycemia.« less

Amino acids rather than glucose account for the majority of cell mass in proliferating mammalian cells

PubMed Central

Hosios, Aaron M.; Hecht, Vivian C.; Danai, Laura V.; Johnson, Marc O.; Rathmell, Jeffrey C.; Steinhauser, Matthew L.; Manalis, Scott R.; Vander Heiden, Matthew G.

2016-01-01

Cells must duplicate their mass in order to proliferate. Glucose and glutamine are the major nutrients consumed by proliferating mammalian cells, but the extent to which these and other nutrients contribute to cell mass is unknown. We quantified the fraction of cell mass derived from different nutrients and find that the majority of carbon mass in cells is derived from other amino acids, which are consumed at much lower rates than glucose and glutamine. While glucose carbon has diverse fates, glutamine contributes most to protein, and this suggests that glutamine’s ability to replenish TCA cycle intermediates (anaplerosis) is primarily used for amino acid biosynthesis. These findings demonstrate that rates of nutrient consumption are indirectly associated with mass accumulation and suggest that high rates of glucose and glutamine consumption support rapid cell proliferation beyond providing carbon for biosynthesis. PMID:26954548

The urea cycle disorders.

PubMed

Helman, Guy; Pacheco-Colón, Ileana; Gropman, Andrea L

2014-07-01

The urea cycle is the primary nitrogen-disposal pathway in humans. It requires the coordinated function of six enzymes and two mitochondrial transporters to catalyze the conversion of a molecule of ammonia, the α-nitrogen of aspartate, and bicarbonate into urea. Whereas ammonia is toxic, urea is relatively inert, soluble in water, and readily excreted by the kidney in the urine. Accumulation of ammonia and other toxic intermediates of the cycle lead to predominantly neurologic sequelae. The disorders may present at any age from the neonatal period to adulthood, with the more severely affected patients presenting earlier in life. Patients are at risk for metabolic decompensation throughout life, often triggered by illness, fasting, surgery and postoperative states, peripartum, stress, and increased exogenous protein load. Here the authors address neurologic presentations of ornithine transcarbamylase deficiency in detail, the most common of the urea cycle disorders, neuropathology, neurophysiology, and our studies in neuroimaging. Special attention to late-onset presentations is given. Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.

Infrared and visible absolute and difference spectra of bacteriorhodopsin photocycle intermediates.

PubMed

Hendler, Richard W; Meuse, Curtis W; Braiman, Mark S; Smith, Paul D; Kakareka, John W

2011-09-01

We have used new kinetic fitting procedures to obtain infrared (IR) absolute spectra for intermediates of the main bacteriorhodopsin (bR) photocycle(s). The linear-algebra-based procedures of Hendler et al. (J. Phys. Chem. B, 105, 3319-3228 (2001)) for obtaining clean absolute visible spectra of bR photocycle intermediates were adapted for use with IR data. This led to isolation, for the first time, of corresponding clean absolute IR spectra, including the separation of the M intermediate into its M(F) and M(S) components from parallel photocycles. This in turn permitted the computation of clean IR difference spectra between pairs of successive intermediates, allowing for the most rigorous analysis to date of changes occurring at each step of the photocycle. The statistical accuracy of the spectral calculation methods allows us to identify, with great confidence, new spectral features. One of these is a very strong differential IR band at 1650 cm(-1) for the L intermediate at room temperature that is not present in analogous L spectra measured at cryogenic temperatures. This band, in one of the noisiest spectral regions, has not been identified in any previous time-resolved IR papers, although retrospectively it is apparent as one of the strongest L absorbance changes in their raw data, considered collectively. Additionally, our results are most consistent with Arg82 as the primary proton-release group (PRG), rather than a protonated water cluster or H-bonded grouping of carboxylic residues. Notably, the Arg82 deprotonation occurs exclusively in the M(F) pathway of the parallel cycles model of the photocycle. © 2011 Society for Applied Spectroscopy

Factors That Affect Oxygen Activation and Coupling of the Two Redox Cycles in the Aromatization Reaction Catalyzed by NikD, an Unusual Amino Acid Oxidase

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kommoju, Phaneeswara-Rao; Bruckner, Robert C.; Ferreira, Patricia

2009-10-21

NikD is a flavoprotein oxidase that catalyzes the oxidation of piperideine-2-carboxylate (P2C) to picolinate in a remarkable aromatization reaction comprising two redox cycles and at least one isomerization step. Tyr258 forms part of an 'aromatic cage' that surrounds the ring in picolinate and its precursors. Mutation of Tyr258 to Phe does not perturb the structure of nikD but does affect the coupling of the two redox cycles and causes a 10-fold decrease in turnover rate. Tyr258Phe catalyzes a quantitative two-electron oxidation of P2C, but only 60% of the resulting dihydropicolinate intermediate undergoes a second redox cycle to produce picolinate. Themore » mutation does not affect product yield with an alternate substrate (3,4-dehydro-l-proline) that is aromatized in a single two-electron oxidation step. Wild-type and mutant enzymes exhibit identical rate constants for oxidation of P2C to dihydropicolinate and isomerization of a reduced enzyme-dihydropicolinate complex. The observed rates are 200- and 10-fold faster, respectively, than the mutant turnover rate. Release of picolinate from Tyr258Phe is 100-fold faster than turnover. The presence of a bound substrate or product is a key factor in oxygen activation by wild-type nikD, as judged by the 10-75-fold faster rates observed for complexes of the reduced enzyme with picolinate, benzoate, or 1-cyclohexenoate, a 1-deaza-P2C analogue. The reduced Tyr258Phe-1-cyclohexenoate complex is 25-fold less reactive with oxygen than the wild-type complex. We postulate that mutation of Tyr258 causes subtle changes in active site dynamics that promote release of the reactive dihydropicolinate intermediate and disrupt the efficient synchronization of oxygen activation observed with wild-type nikD.« less

Electrochemical Detection of Transient Cobalt Hydride Intermediates of Electrocatalytic Hydrogen Production

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wiedner, Eric S.; Bullock, R. Morris

2016-07-06

We report the use of variable scan rate cyclic voltammetry to detect transient CoIIIH and CoIIH intermediates of electrocatalytic H2 production by CoII(dmgBF2)2(CH3CN)2 and [CoII(PtBu2NPh2)(CH3CN)3]2+. In both cases, reduction of the CoIIIH intermediate was observed to coincide with the CoII/I couple, and the resulting CoIIH intermediate is protonated by acid to afford H2. Our studies indicate that in electrocatalytic H2 production, protonation of CoIIH is rate-limiting for CoII(dmgBF2)2(CH3CN)2, and protonation of CoI is rate-limiting for [CoII(PtBu2NPh2)(CH3CN)3]2+. This research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy,more » Office of Science, Office of Basic Energy Sciences. Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.« less

Characteristics of NO cycle coupling with urea cycle in non-hyperammonemic carriers of ornithine transcarbamylase deficiency.

PubMed

Nagasaka, Hironori; Yorifuji, Tohru; Egawa, Hiroto; Inui, Ayano; Fujisawa, Tomoo; Komatsu, Haruki; Tsukahara, Hirokazu; Uemoto, Shinji; Inomata, Yukihiro

2013-07-01

Urea cycle deficient patients with prominent hyperammonemic often exhibit abnormal production of nitric oxide (NO), which reduces vascular tone, along with amino acid abnormalities. However, information related to the metabolic changes in heterozygotes of ornithine transcarbamylase deficiency (OTCD) lacking overt hyperammonemia is quite limited. We examined vascular mediators and amino acids in non-hyperammonemic heterozygotes. Twenty-four heterozygous OTCD adult females without hyperammonemic bouts, defined as non-hyperammonemic carriers, were enrolled. We measured blood amino acids constituting urea cycle and nitric oxide (NO) cycle. Blood concentrations of nitrate/nitrite (NOx) as stable NO-metabolites, asymmetric dimethylarginine (ADMA) inhibiting NO synthesis, and endothelin-1 (ET-1) raising vascular tone were also determined. NOx concentrations were significantly lower in non-hyperammonemic carriers (p < 0.01). However, ADMA and ET-1 levels in this group were comparable to those in the age-matched control group. Arginine and citrulline levels were also significantly lower in non-hyperammonemic carriers than in controls (p < 0.01). Of the 24 non-hyperammonemic carriers, 10 often developed headaches. Their daily NOx and arginine levels were significantly lower than those in headache-free carriers (p < 0.05). In three carriers receiving oral l-arginine, blood NOx concentrations were significantly higher. In two of those three, the occurrence of headaches was decreased. These results suggest that NO cycle coupling with the urea cycle is altered substantially even in non-hyperammonemic OTCD carriers, predisposing them to headaches. Copyright © 2013 Elsevier Inc. All rights reserved.

Loss of Mitochondrial Pyruvate Carrier 2 in the Liver Leads to Defects in Gluconeogenesis and Compensation via Pyruvate-Alanine Cycling.

PubMed

McCommis, Kyle S; Chen, Zhouji; Fu, Xiaorong; McDonald, William G; Colca, Jerry R; Kletzien, Rolf F; Burgess, Shawn C; Finck, Brian N

2015-10-06

Pyruvate transport across the inner mitochondrial membrane is believed to be a prerequisite for gluconeogenesis in hepatocytes, which is important for the maintenance of normoglycemia during prolonged food deprivation but also contributes to hyperglycemia in diabetes. To determine the requirement for mitochondrial pyruvate import in gluconeogenesis, mice with liver-specific deletion of mitochondrial pyruvate carrier 2 (LS-Mpc2(-/-)) were generated. Loss of MPC2 impaired, but did not completely abolish, hepatocyte conversion of labeled pyruvate to TCA cycle intermediates and glucose. Unbiased metabolomic analyses of livers from fasted LS-Mpc2(-/-) mice suggested that alterations in amino acid metabolism, including pyruvate-alanine cycling, might compensate for the loss of MPC2. Indeed, inhibition of pyruvate-alanine transamination further reduced mitochondrial pyruvate metabolism and glucose production by LS-Mpc2(-/-) hepatocytes. These data demonstrate an important role for MPC2 in controlling hepatic gluconeogenesis and illuminate a compensatory mechanism for circumventing a block in mitochondrial pyruvate import. Copyright © 2015 Elsevier Inc. All rights reserved.

Accumulation of 5-Oxoproline in Mouse Tissues After Inhibition of 5-Oxoprolinase and Administration of Amino Acids: Evidence for Function of the γ-Glutamyl Cycle*

PubMed Central

Van Der Werf, Paul; Stephani, Ralph A.; Meister, Alton

1974-01-01

5-Oxoprolinase catalyzes the conversion of 5-oxo-L-proline (L-pyroglutamate, L-2-pyrrolidone-5-carboxylate) to L-glutamate with concomitant stoichiometric cleavage of ATP to ADP and inorganic orthophosphate. In this reaction, a step in the γ-glutamyl cycle, 5-oxoproline (formed by the action of γ-glutamylcyclotransferase on γ-glutamyl amino acids, which are in turn formed by transpeptidation of amino acids with glutathione), is made available for glutathione synthesis. When mice are injected with L-2-imidazolidone-4-carboxylate, a competitive inhibitor of 5-oxoprolinase, they accumulate 5-oxoproline in their tissues (kidney, liver, brain, and eye) and excrete it in the urine. Mice given the inhibitor together with one of several L-amino acids accumulate and excrete much more 5-oxoproline than when they are given the inhibitor alone. Such augmentation of 5-oxoproline accumulation offers evidence for the function of the γ-glutamyl cycle in vivo and supports the view that 5-oxoproline is a quantitatively significant metabolite. Images PMID:4151516

Evolution of dispersal in spatially and temporally variable environments: The importance of life cycles.

PubMed

Massol, François; Débarre, Florence

2015-07-01

Spatiotemporal variability of the environment is bound to affect the evolution of dispersal, and yet model predictions strongly differ on this particular effect. Recent studies on the evolution of local adaptation have shown that the life cycle chosen to model the selective effects of spatiotemporal variability of the environment is a critical factor determining evolutionary outcomes. Here, we investigate the effect of the order of events in the life cycle on the evolution of unconditional dispersal in a spatially heterogeneous, temporally varying landscape. Our results show that the occurrence of intermediate singular strategies and disruptive selection are conditioned by the temporal autocorrelation of the environment and by the life cycle. Life cycles with dispersal of adults versus dispersal of juveniles, local versus global density regulation, give radically different evolutionary outcomes that include selection for total philopatry, evolutionary bistability, selection for intermediate stable states, and evolutionary branching points. Our results highlight the importance of accounting for life-cycle specifics when predicting the effects of the environment on evolutionarily selected trait values, such as dispersal, as well as the need to check the robustness of model conclusions against modifications of the life cycle. © 2015 The Author(s). Evolution © 2015 The Society for the Study of Evolution.

Investigation into the Physiological Significance of the Phytohormone Abscisic Acid in Perkinsus marinus, an Oyster Parasite Harboring a Nonphotosynthetic Plastid.

PubMed

Sakamoto, Hirokazu; Suzuki, Shigeo; Nagamune, Kisaburo; Kita, Kiyoshi; Matsuzaki, Motomichi

2017-07-01

Some organisms have retained plastids even after they have lost the ability to photosynthesize. Several studies of nonphotosynthetic plastids in apicomplexan parasites have shown that the isopentenyl pyrophosphate biosynthesis pathway in the organelle is essential for their survival. A phytohormone, abscisic acid, one of several compounds biosynthesized from isopentenyl pyrophosphate, regulates the parasite cell cycle. Thus, it is possible that the phytohormone is universally crucial, even in nonphotosynthetic plastids. Here, we examined this possibility using the oyster parasite Perkinsus marinus, which is a plastid-harboring cousin of apicomplexan parasites and has independently lost photosynthetic ability. Fluridone, an inhibitor of abscisic acid biosynthesis, blocked parasite growth and induced cell clustering. Nevertheless, abscisic acid and its intermediate carotenoids did not affect parasite growth or rescue the parasite from inhibition. Moreover, abscisic acid was not detected from the parasite using liquid chromatography mass spectrometry. Our findings show that abscisic acid does not play any significant roles in P. marinus. © 2016 The Authors. Journal of Eukaryotic Microbiology published by Wiley Periodicals, Inc. on behalf of International Society of Protistologists.

Oxidation of atenolol, propranolol, carbamazepine and clofibric acid by a biological Fenton-like system mediated by the white-rot fungus Trametes versicolor.

PubMed

Marco-Urrea, Ernest; Radjenović, Jelena; Caminal, Gloria; Petrović, Mira; Vicent, Teresa; Barceló, Damià

2010-01-01

Biological advanced oxidation of the pharmaceuticals clofibric acid (CA), carbamazepine (CBZP), atenolol (ATL) and propranolol (PPL) is reported for the first time. Extracellular oxidizing species were produced through a quinone redox cycling mechanism catalyzed by an intracellular quinone reductase and any of the ligninolytic enzymes of Trametes versicolor after addition of the lignin-derived quinone 2,6-dimethoxy-1,4-benzoquinone (DBQ) and Fe(3+)-oxalate in the medium. Time-course experiments with approximately 10mg L(-1) of initial pharmaceutical concentration resulted in percent degradations above 80% after 6h of incubation. Oxidation of pharmaceuticals was only observed under DBQ redox cycling conditions. A similar degradation pattern was observed when CBZP was added at the environmentally relevant concentration of 50 microg L(-1). Depletion of DBQ due to the attack of oxidizing agents was assumed to be the main limiting factor of pharmaceutical degradation. The main degradation products, that resulted to be pharmaceutical hydroxylated derivatives, were structurally elucidated. The detected 4- and 7-hydroxycarbamazepine intermediates of CBZP degradation were not reported to date. Total disappearance of intermediates was observed in all the experiments at the end of the incubation period. (c) 2009 Elsevier Ltd. All rights reserved.

The phylogeny and life cycle of two species of Profilicollis (Acanthocephala: Polymorphidae) in marine hosts off the Pacific coast of Chile.

PubMed

Rodríguez, S M; D'Elía, G; Valdivia, N

2017-09-01

Resolving complex life cycles of parasites is a major goal of parasitological research. The aim of this study was to analyse the life cycle of two species of the genus Profilicollis, the taxonomy of which is still unstable and life cycles unclear. We extracted individuals of Profilicollis from two species of crustaceans (intermediate hosts) and four species of seagulls (definitive hosts) from sandy-shore and estuarine habitats along the south-east Pacific coast of Chile. Mitochondrial DNA analyses showed that two species of Profilicollis infected intermediate hosts from segregated habitats: while P. altmani larvae infected exclusively molecrabs of the genus Emerita from fully marine habitats, P. antarcticus larvae infected the crab Hemigrapsus crenulatus from estuarine habitats. Moreover, P. altmani completed its life cycle in four seagulls, Chroicocephalus maculipennis, Leucopheus pipixcan, Larus modestus and L. dominicanus, while P. antarcticus, on the other hand, completed its life cycle in the kelp gull L. dominicanus. Accordingly, our results show that two congeneric parasites use different and spatially segregated species as intermediate hosts, and both are capable of infecting one species of definitive hosts. As such, our analyses allow us to shed light on a complex interaction network.

Synthesis of antiviral tetrahydrocarbazole derivatives by photochemical and acid-catalyzed C-H functionalization via intermediate peroxides (CHIPS).

PubMed

Gulzar, Naeem; Klussmann, Martin

2014-06-20

The direct functionalization of C-H bonds is an important and long standing goal in organic chemistry. Such transformations can be very powerful in order to streamline synthesis by saving steps, time and material compared to conventional methods that require the introduction and removal of activating or directing groups. Therefore, the functionalization of C-H bonds is also attractive for green chemistry. Under oxidative conditions, two C-H bonds or one C-H and one heteroatom-H bond can be transformed to C-C and C-heteroatom bonds, respectively. Often these oxidative coupling reactions require synthetic oxidants, expensive catalysts or high temperatures. Here, we describe a two-step procedure to functionalize indole derivatives, more specifically tetrahydrocarbazoles, by C-H amination using only elemental oxygen as oxidant. The reaction uses the principle of C-H functionalization via Intermediate PeroxideS (CHIPS). In the first step, a hydroperoxide is generated oxidatively using visible light, a photosensitizer and elemental oxygen. In the second step, the N-nucleophile, an aniline, is introduced by Brønsted-acid catalyzed activation of the hydroperoxide leaving group. The products of the first and second step often precipitate and can be conveniently filtered off. The synthesis of a biologically active compound is shown.

Artificial Autopolyploidization Modifies the Tricarboxylic Acid Cycle and GABA Shunt in Arabidopsis thaliana Col-0

NASA Astrophysics Data System (ADS)

Vergara, Fredd; Kikuchi, Jun; Breuer, Christian

2016-05-01

Autopolyploidy is a process whereby the chromosome set is multiplied and it is a common phenomenon in angiosperms. Autopolyploidy is thought to be an important evolutionary force that has led to the formation of new plant species. Despite its relevance, the consequences of autopolyploidy in plant metabolism are poorly understood. This study compares the metabolic profiles of natural diploids and artificial autotetraploids of Arabidopsis thaliana Col-0. Different physiological parameters are compared between diploids and autotetraploids using nuclear magnetic resonance (NMR), elemental analysis (carbon:nitrogen balance) and quantitative real-time PCR (qRT-PCR). The main difference between diploid and autotetraploid A. thaliana Col-0 is observed in the concentration of metabolites related to the tricarboxylic acid cycle (TCA) and γ-amino butyric acid (GABA) shunt, as shown by multivariate statistical analysis of NMR spectra. qRT-PCR shows that genes related to the TCA and GABA shunt are also differentially expressed between diploids and autotetraploids following similar trends as their corresponding metabolites. Solid evidence is presented to demonstrate that autopolyploidy influences core plant metabolic processes.

Redox regulation of protein tyrosine phosphatase 1B (PTP1B): Importance of steric and electronic effects on the unusual cyclization of the sulfenic acid intermediate to a sulfenyl amide

NASA Astrophysics Data System (ADS)

Sarma, Bani Kanta

2013-09-01

The redox regulation of protein tyrosine phosphatase 1B (PTP1B) via the unusual transformation of its sulfenic acid (PTP1B-SOH) to a cyclic sulfenyl amide intermediate is studied by using small molecule chemical models. These studies suggest that the sulfenic acids derived from the H2O2-mediated reactions o-amido thiophenols do not efficiently cyclize to sulfenyl amides and the sulfenic acids produced in situ can be trapped by using methyl iodide. Theoretical calculations suggest that the most stable conformer of such sulfenic acids are stabilized by nO → σ*S-OH orbital interactions, which force the -OH group to adopt a position trans to the S⋯O interaction, leading to an almost linear arrangement of the O⋯S-O moiety and this may be the reason for the slow cyclization of such sulfenic acids to their corresponding sulfenyl amides. On the other hand, additional substituents at the 6-position of o-amido phenylsulfenic acids that can induce steric environment and alter the electronic properties around the sulfenic acid moiety by S⋯N or S⋯O nonbonded interactions destabilize the sulfenic acids by inducing strain in the molecule. This may lead to efficient the cyclization of such sulfenic acids. This model study suggests that the amino acid residues in the close proximity of the sulfenic acid moiety in PTP1B may play an important role in the cyclization of PTP1B-SOH to produce the corresponding sulfenyl amide.

The Mammalian Cell Cycle Regulates Parvovirus Nuclear Capsid Assembly

PubMed Central

Riolobos, Laura; Domínguez, Carlos; Kann, Michael; Almendral, José M.

2015-01-01

It is unknown whether the mammalian cell cycle could impact the assembly of viruses maturing in the nucleus. We addressed this question using MVM, a reference member of the icosahedral ssDNA nuclear parvoviruses, which requires cell proliferation to infect by mechanisms partly understood. Constitutively expressed MVM capsid subunits (VPs) accumulated in the cytoplasm of mouse and human fibroblasts synchronized at G0, G1, and G1/S transition. Upon arrest release, VPs translocated to the nucleus as cells entered S phase, at efficiencies relying on cell origin and arrest method, and immediately assembled into capsids. In synchronously infected cells, the consecutive virus life cycle steps (gene expression, proteins nuclear translocation, capsid assembly, genome replication and encapsidation) proceeded tightly coupled to cell cycle progression from G0/G1 through S into G2 phase. However, a DNA synthesis stress caused by thymidine irreversibly disrupted virus life cycle, as VPs became increasingly retained in the cytoplasm hours post-stress, forming empty capsids in mouse fibroblasts, thereby impairing encapsidation of the nuclear viral DNA replicative intermediates. Synchronously infected cells subjected to density-arrest signals while traversing early S phase also blocked VPs transport, resulting in a similar misplaced cytoplasmic capsid assembly in mouse fibroblasts. In contrast, thymidine and density arrest signals deregulating virus assembly neither perturbed nuclear translocation of the NS1 protein nor viral genome replication occurring under S/G2 cycle arrest. An underlying mechanism of cell cycle control was identified in the nuclear translocation of phosphorylated VPs trimeric assembly intermediates, which accessed a non-conserved route distinct from the importin α2/β1 and transportin pathways. The exquisite cell cycle-dependence of parvovirus nuclear capsid assembly conforms a novel paradigm of time and functional coupling between cellular and virus life

The Drosophila Sp8 transcription factor Buttonhead prevents premature differentiation of intermediate neural progenitors

PubMed Central

Xie, Yonggang; Li, Xiaosu; Zhang, Xian; Mei, Shaolin; Li, Hongyu; Urso, Andreacarola; Zhu, Sijun

2014-01-01

Intermediate neural progenitor cells (INPs) need to avoid differentiation and cell cycle exit while maintaining restricted developmental potential, but mechanisms preventing differentiation and cell cycle exit of INPs are not well understood. In this study, we report that the Drosophila homolog of mammalian Sp8 transcription factor Buttonhead (Btd) prevents premature differentiation and cell cycle exit of INPs in Drosophila larval type II neuroblast (NB) lineages. We show that the loss of Btd leads to elimination of mature INPs due to premature differentiation of INPs into terminally dividing ganglion mother cells. We provide evidence to demonstrate that Btd prevents the premature differentiation by suppressing the expression of the homeodomain protein Prospero in immature INPs. We further show that Btd functions cooperatively with the Ets transcription factor Pointed P1 to promote the generation of INPs. Thus, our work reveals a critical mechanism that prevents premature differentiation and cell cycle exit of Drosophila INPs. DOI: http://dx.doi.org/10.7554/eLife.03596.001 PMID:25285448

Structural intermediates and directionality of the swiveling motion of Pyruvate Phosphate Dikinase

NASA Astrophysics Data System (ADS)

Minges, Alexander; Ciupka, Daniel; Winkler, Christian; Höppner, Astrid; Gohlke, Holger; Groth, Georg

2017-03-01

Pyruvate phosphate dikinase (PPDK) is a vital enzyme in cellular energy metabolism catalyzing the ATP- and Pi-dependent formation of phosphoenolpyruvate from pyruvate in C4 -plants, but the reverse reaction forming ATP in bacteria and protozoa. The multi-domain enzyme is considered an efficient molecular machine that performs one of the largest single domain movements in proteins. However, a comprehensive understanding of the proposed swiveling domain motion has been limited by not knowing structural intermediates or molecular dynamics of the catalytic process. Here, we present crystal structures of PPDKs from Flaveria, a model genus for studying the evolution of C4 -enzymes from phylogenetic ancestors. These structures resolve yet unknown conformational intermediates and provide the first detailed view on the large conformational transitions of the protein in the catalytic cycle. Independently performed unrestrained MD simulations and configurational free energy calculations also identified these intermediates. In all, our experimental and computational data reveal strict coupling of the CD swiveling motion to the conformational state of the NBD. Moreover, structural asymmetries and nucleotide binding states in the PPDK dimer support an alternate binding change mechanism for this intriguing bioenergetic enzyme.

Ferrocene-Promoted Long-Cycle Lithium-Sulfur Batteries.

PubMed

Mi, Yingying; Liu, Wen; Yang, Ke R; Jiang, Jianbing; Fan, Qi; Weng, Zhe; Zhong, Yiren; Wu, Zishan; Brudvig, Gary W; Batista, Victor S; Zhou, Henghui; Wang, Hailiang

2016-11-14

Confining lithium polysulfide intermediates is one of the most effective ways to alleviate the capacity fade of sulfur-cathode materials in lithium-sulfur (Li-S) batteries. To develop long-cycle Li-S batteries, there is an urgent need for material structures with effective polysulfide binding capability and well-defined surface sites; thereby improving cycling stability and allowing study of molecular-level interactions. This challenge was addressed by introducing an organometallic molecular compound, ferrocene, as a new polysulfide-confining agent. With ferrocene molecules covalently anchored on graphene oxide, sulfur electrode materials with capacity decay as low as 0.014 % per cycle were realized, among the best of cycling stabilities reported to date. With combined spectroscopic studies and theoretical calculations, it was determined that effective polysulfide binding originates from favorable cation-π interactions between Li + of lithium polysulfides and the negatively charged cyclopentadienyl ligands of ferrocene. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Pimelic acid, the first precursor of the Bacillus subtilis biotin synthesis pathway, exists as the free acid and is assembled by fatty acid synthesis.

PubMed

Manandhar, Miglena; Cronan, John E

2017-05-01

Biotin synthetic pathways are readily separated into two stages, synthesis of the seven carbon α, ω-dicarboxylic acid pimelate moiety and assembly of the fused heterocyclic rings. The biotin pathway genes responsible for pimelate moiety synthesis vary widely among bacteria whereas the ring synthesis genes are highly conserved. Bacillus subtilis seems to have redundant genes, bioI and bioW, for generation of the pimelate intermediate. Largely consistent with previous genetic studies it was found that deletion of bioW caused a biotin auxotrophic phenotype whereas deletion of bioI did not. BioW is a pimeloyl-CoA synthetase that converts pimelic acid to pimeloyl-CoA. The essentiality of BioW for biotin synthesis indicates that the free form of pimelic acid is an intermediate in biotin synthesis although this is not the case in E. coli. Since the origin of pimelic acid in Bacillus subtilis is unknown, 13 C-NMR studies were carried out to decipher the pathway for its generation. The data provided evidence for the role of free pimelate in biotin synthesis and the involvement of fatty acid synthesis in pimelate production. Cerulenin, an inhibitor of the key fatty acid elongation enzyme, FabF, markedly decreased biotin production by B. subtilis resting cells whereas a strain having a cerulenin-resistant FabF mutant produced more biotin. In addition, supplementation with pimelic acid fully restored biotin production in cerulenin-treated cells. These results indicate that pimelic acid originating from fatty acid synthesis pathway is a bona fide precursor of biotin in B. subtilis. © 2017 John Wiley & Sons Ltd.

A combined experimental and computational study of the mechanism of fructose dehydration to 5-hydroxymethylfurfural in dimethylsulfoxide using Amberlyst 70, PO 4 3-/niobic acid, or sulfuric acid catalysts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Jing; Das, Anirban; Assary, Rajeev S.

We report on a combined experimental and theoretical study of the acid catalyzed dehydration of d-fructose in dimethylsulfoxide (DMSO) using; Amberlyst 70, PO 4 3-/niobic acid, and sulfuric acid as catalysts. The reaction has been studied and intermediates characterized using; 13C, 1H, and 17O NMR, and high resolution electrospray ionization mass spectrometry (HR ESI–MS). High level G4MP2 theory calculations are used to understand the thermodynamic landscape for the reaction mechanism in DMSO. We have experimentally identified two key intermediates in the dehydration of fructose to form HMF that were also identified, using theory, as local minima on the potential surfacemore » for reaction. A third intermediate, a species capable of undergoing keto–enol tautomerism, was also experimentally detected. However, it was not possible to experimentally distinguish between the keto and the enol forms. These data with different catalysts are consistent with common intermediates along the reaction pathway from fructose to HMF in DMSO. The role of oxygen in producing acidic species in reactions carried out in DMSO in presence of air is also discussed.« less

Catabolism of α-Ketoglutarate by a sucA Mutant of Bradyrhizobium japonicum: Evidence for an Alternative Tricarboxylic Acid Cycle

PubMed Central

Green, Laura S.; Li, Youzhong; Emerich, David W.; Bergersen, Fraser J.; Day, David A.

2000-01-01

A complete tricarboxylic acid (TCA) cycle is generally considered necessary for energy production from the dicarboxylic acid substrates malate, succinate, and fumarate. However, a Bradyrhizobium japonicum sucA mutant that is missing α-ketoglutarate dehydrogenase is able to grow on malate as its sole source of carbon. This mutant also fixes nitrogen in symbiosis with soybean, where dicarboxylic acids are its principal carbon substrate. Using a flow chamber system to make direct measurements of oxygen consumption and ammonium excretion, we confirmed that bacteroids formed by the sucA mutant displayed wild-type rates of respiration and nitrogen fixation. Despite the absence of α-ketoglutarate dehydrogenase activity, whole cells of the mutant were able to decarboxylate α-[U-14C]ketoglutarate and [U-14C]glutamate at rates similar to those of wild-type B. japonicum, indicating that there was an alternative route for α-ketoglutarate catabolism. Because cell extracts from B. japonicum decarboxylated [U-14C]glutamate very slowly, the γ-aminobutyrate shunt is unlikely to be the pathway responsible for α-ketoglutarate catabolism in the mutant. In contrast, cell extracts from both the wild type and mutant showed a coenzyme A (CoA)-independent α-ketoglutarate decarboxylation activity. This activity was independent of pyridine nucleotides and was stimulated by thiamine PPi. Thin-layer chromatography showed that the product of α-ketoglutarate decarboxylation was succinic semialdehyde. The CoA-independent α-ketoglutarate decarboxylase, along with succinate semialdehyde dehydrogenase, may form an alternative pathway for α-ketoglutarate catabolism, and this pathway may enhance TCA cycle function during symbiotic nitrogen fixation. PMID:10781553

Studies of thermochemical water-splitting cycles

NASA Technical Reports Server (NTRS)

Remick, R. J.; Foh, S. E.

1980-01-01

Higher temperatures and more isothermal heat profiles of solar heat sources are developed. The metal oxide metal sulfate class of cycles were suited for solar heat sources. Electrochemical oxidation of SO2 and thermochemical reactions are presented. Electrolytic oxidation of sulfur dioxide in dilute sulfuric acid solutions were appropriate for metal oxide metal sulfate cycles. The cell voltage at workable current densities required for the oxidation of SO2 was critical to the efficient operation of any metal oxide metal sulfate cycle. A sulfur dioxide depolarized electrolysis cell for the splitting of water via optimization of the anode reaction is discussed. Sulfuric acid concentrations of 30 to 35 weight percent are preferred. Platinized platinum or smooth platinum gave the best anode kinetics at a given potential of the five materials examined.

Anaerobic organic acid metabolism of Candida zemplinina in comparison with Saccharomyces wine yeasts.

PubMed

Magyar, Ildikó; Nyitrai-Sárdy, Diána; Leskó, Annamária; Pomázi, Andrea; Kállay, Miklós

2014-05-16

Organic acid production under oxygen-limited conditions has been thoroughly studied in the Saccharomyces species, but practically never investigated in Candida zemplinina, which seems to be an acidogenic species under oxidative laboratory conditions. In this study, several strains of C. zemplinina were tested for organic acid metabolism, in comparison with Saccharomyces cerevisiae, Saccharomyces uvarum and Candida stellata, under fermentative conditions. Only C. stellata produced significantly higher acidity in simple minimal media (SM) with low sugar content and two different nitrogen sources (ammonia or glutamic acid) at low level. However, the acid profile differed largely between the Saccharomyces and Candida species and showed inverse types of N-dependence in some cases. Succinic acid production was strongly enhanced on glutamic acid in Saccharomyces species, but not in Candida species. 2-oxoglutarate production was strongly supported on ammonium nitrogen in Candida species, but remained low in Saccharomyces. Candida species, C. stellata in particular, produced more pyruvic acid regardless of N-sources. From the results, we concluded that the anaerobic organic acid metabolisms of C. zemplinina and C. stellata are different from each other and also from that of the Saccharomyces species. In the formation of succinic acid, the oxidative pathway from glutamic acid seems to play little or no role in C. zemplinina. The reductive branch of the TCA cycle, however, produces acidic intermediates (malic, fumaric, and succinic acid) in a level comparable with the production of the Saccharomyces species. An unidentified organic acid, which was produced on glutamic acid only by the Candida species, needs further investigation. Copyright © 2014 Elsevier B.V. All rights reserved.

Novel insights into the bioenergetics of mixed-acid fermentation: can hydrogen and proton cycles combine to help maintain a proton motive force?

PubMed

Trchounian, Armen; Gary Sawers, R

2014-01-01

Escherichia coli possesses four [NiFe]-hydrogenases that catalyze the reversible redox reaction of 2H(+) + 2e(-) ↔ H2. These enzymes together have the potential to form a hydrogen cycle across the membrane. Their activity, operational direction, and interaction with each other depend on the fermentation substrate and particularly pH. The enzymes producing H2 are likely able to translocate protons through the membrane. Moreover, the activity of some of these enzymes is dependent on the F0 F1 -ATPase, thus linking a proton cycle with the cycling of hydrogen. These two cycles are suggested to have a primary basic role in modulating the cell's energetics during mixed-acid fermentation, particularly in response to pH. Nevertheless, the mechanisms underlying the physical interactions between these enzyme complexes, as well as how this is controlled, are still not clearly understood. Here, we present a synopsis of the potential impact of proton-hydrogen cycling in fermentative bioenergetics. © 2013 International Union of Biochemistry and Molecular Biology.

Single center experience with endoscopic subureteral dextranomer/hyaluronic acid injection as first line treatment in 1,551 children with intermediate and high grade vesicoureteral reflux.

PubMed

Puri, Prem; Kutasy, Balazs; Colhoun, Eric; Hunziker, Manuela

2012-10-01

In recent years the endoscopic injection of dextranomer/hyaluronic acid has become an established alternative to long-term antibiotic prophylaxis and the surgical management of vesicoureteral reflux. We determined the safety and effectiveness of the endoscopic injection of dextranomer/hyaluronic acid as first line treatment for high grade vesicoureteral reflux. Between 2001 and 2010, 1,551 children (496 male, 1,055 female, median age 1.6 years) underwent endoscopic correction of intermediate and high grade vesicoureteral reflux using dextranomer/hyaluronic acid soon after the diagnosis of vesicoureteral reflux on initial voiding cystourethrogram. Vesicoureteral reflux was unilateral in 761 children and bilateral in 790. Renal scarring was detected in 369 (26.7%) of the 1,384 patients who underwent dimercapto-succinic acid imaging. Reflux grade in the 2,341 ureters was II in 98 (4.2%), III in 1,340 (57.3%), IV in 818 (34.9%) and V in 85 (3.6%). Followup ultrasound and voiding cystourethrogram were performed 3 months after the outpatient procedure, and renal ultrasound was performed annually thereafter. Patients were followed for 3 months to 10 years (median 5.6 years). Vesicoureteral reflux resolved after the first, second and third endoscopic injection of dextranomer/hyaluronic acid in 2,039 (87.1%), 264 (11.3%) and 38 (1.6%) ureters, respectively. Febrile urinary tract infections developed during followup in 69 (4.6%) patients. None of the patients in the series needed reimplantation of ureters or experienced any significant complications. Our results confirm the safety and efficacy of the endoscopic injection of dextranomer/hyaluronic acid in the eradication of high grade vesicoureteral reflux. We recommend this 15-minute outpatient procedure as the first line of treatment for high grade vesicoureteral reflux. Copyright © 2012 American Urological Association Education and Research, Inc. Published by Elsevier Inc. All rights reserved.

Analysis of a domestic refrigerator cycle with an ejector

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tomasek, M.L.; Radermacher, R.

1995-08-01

In this paper, an improved cooling cycle for a conventional domestic refrigerator-freezer utilizing an ejector for vapor precompression is analyzed using an idealized model Its energy efficiency is compared to that of the conventional refrigerator-freezer system. Emphasis is placed on off-design conditions. The ejector-enhanced refrigeration cycle consists of two evaporators that operate at different pressure and temperature levels. The ejector combines the vapor flows exiting the two evaporators into one at an intermediate pressure level The ejector cycle gives an increase of up to 12.4% in the coefficient of performance (COP) compared to that of a standard refrigerator-freezer refrigeration cycle.more » The analysis includes calculations on the optimum throat diameters of the ejector. The investigation on the off-design performance of the ejector cycle shows little dependency of energy consumption on constant ejector throat diameters.« less

Geochemical roots of autotrophic carbon fixation: hydrothermal experiments in the system citric acid, H 2O-(±FeS)-(±NiS)

NASA Astrophysics Data System (ADS)

Cody, G. D.; Boctor, N. Z.; Hazen, R. M.; Brandes, J. A.; Morowitz, Harold J.; Yoder, H. S.

2001-10-01

Recent theories have proposed that life arose from primitive hydrothermal environments employing chemical reactions analogous to the reductive citrate cycle (RCC) as the primary pathway for carbon fixation. This chemistry is presumed to have developed as a natural consequence of the intrinsic geochemistry of the young, prebiotic, Earth. There has been no experimental evidence, however, demonstrating that there exists a natural pathway into such a cycle. Toward this end, the results of hydrothermal experiments involving citric acid are used as a method of deducing such a pathway. Homocatalytic reactions observed in the citric acid-H2O experiments encompass many of the reactions found in modern metabolic systems, i.e., hydration-dehydration, retro-Aldol, decarboxylation, hydrogenation, and isomerization reactions. Three principal decomposition pathways operate to degrade citric acid under thermal and aquathermal conditions. It is concluded that the acid catalyzed βγ decarboxylation pathway, leading ultimately to propene and CO2, may provide the most promise for reaction network reversal under natural hydrothermal conditions. Increased pressure is shown to accelerate the principal decarboxylation reactions under strictly hydrothermal conditions. The effect of forcing the pH via the addition of NaOH reveals that the βγ decarboxylation pathway operates even up to intermediate pH levels. The potential for network reversal (the conversion of propene and CO2 up to a tricarboxylic acid) is demonstrated via the Koch (hydrocarboxylation) reaction promoted heterocatalytically with NiS in the presence of a source of CO. Specifically, an olefin (1-nonene) is converted to a monocarboxylic acid; methacrylic acid is converted to the dicarboxylic acid, methylsuccinic acid; and the dicarboxylic acid, itaconic acid, is converted into the tricarboxylic acid, hydroaconitic acid. A number of interesting sulfur-containing products are also formed that may provide for additional

Processing of the precursor of protamine P2 in mouse. Peptide mapping and N-terminal sequence analysis of intermediates.

PubMed Central

Carré-Eusèbe, D; Lederer, F; Lê, K H; Elsevier, S M

1991-01-01

Protamine P2, the major basic chromosomal protein of mouse spermatozoa, is synthesized as a precursor almost twice as long as the mature protein, its extra length arising from an N-terminal extension of 44 amino acid residues. This precursor is integrated into chromatin of spermatids, and the extension is processed during chromatin condensation in the haploid cells. We have studied processing in the mouse and have identified two intermediates generated by proteolytic cleavage of the precursor. H.p.l.c. separated protamine P2 from four other spermatid proteins, including the precursor and three proteins known to possess physiological characteristics expected of processing intermediates. Peptide mapping indicated that all of these proteins were structurally similar. Two major proteins were further purified by PAGE, transferred to poly(vinylidene difluoride) membranes and submitted to automated N-terminal sequence analysis. Both sequences were found within the deduced sequence of the precursor extension. The N-terminus of the larger intermediate, PP2C, was Gly-12, whereas the N-terminus of the smaller, PP2D, was His-21. Both processing sites involved a peptide bond in which the carbonyl function was contributed by an acidic amino acid. Images Fig. 1. Fig. 3. Fig. 4. PMID:1854346

Combined cycle plants: Yesterday, today, and tomorrow (review)

NASA Astrophysics Data System (ADS)

Ol'khovskii, G. G.

2016-07-01

Gas turbine plants (GTP) for a long time have been developed by means of increasing the initial gas temperature and improvement of the turbo-machines aerodynamics and the efficiency of the critical components air cooling within the framework of a simple thermodynamic cycle. The application of watercooling systems that were used in experimental turbines and studied approximately 50 years ago revealed the fundamental difficulties that prevented the practical implementation of such systems in the industrial GTPs. The steam cooling researches have developed more substantially. The 300 MW power GTPs with a closedloop steam cooling, connected in parallel with the intermediate steam heating line in the steam cycle of the combined cycle plant (CCP) have been built, tested, and put into operation. The designs and cycle arrangements of such GTPs and entire combined cycle steam plants have become substantially more complicated without significant economic benefits. As a result, the steam cooling of gas turbines has not become widespread. The cycles—complicated by the intermediate air cooling under compression and reheat of the combustion products under expansion and their heat recovery to raise the combustion chamber entry temperature of the air—were used, in particular, in the domestic power GTPs with a moderate (700-800°C) initial gas turbine entry temperature. At the temperatures being reached to date (1300-1450°C), only one company, Alstom, applies in their 240-300 MW GTPs the recycled fuel cycle under expansion of gases in the turbine. Although these GTPs are reliable, there are no significant advantages in terms of their economy. To make a forecast of the further improvement of power GTPs, a brief review and assessment of the water cooling and steam cooling of hot components and complication of the GTP cycle by the recycling of fuel under expansion of gases in the turbine has been made. It is quite likely in the long term to reach the efficiency for the

Environmental analysis of the life cycle emissions of 2-methyl tetrahydrofuran solvent manufactured from renewable resources.

PubMed

Slater, C Stewart; Savelski, Mariano J; Hitchcock, David; Cavanagh, Eduardo J

2016-01-01

An environmental analysis has been conducted to determine the cradle to gate life cycle emissions to manufacture the green solvent, 2-methyl tetrahydrofuran. The solvent is considered a greener chemical since it can be manufactured from renewable resources with a lower life cycle footprint. Analyses have been performed using different methods to show greenness in both its production and industrial use. This solvent can potentially be substituted for other ether and chlorinated solvents commonly used in organometallic and biphasic reactions steps in pharmaceutical and fine chemical syntheses. The 2-methyl tetrahydrofuran made from renewable agricultural by-products is marketed by Penn A Kem under the name ecoMeTHF™. The starting material, 2-furfuraldehyde (furfural), is produced from corn cob waste by converting the available pentosans by acid hydrolysis. An evaluation of each step in the process was necessary to determine the overall life cycle and specific CO2 emissions for each raw material/intermediate produced. Allocation of credits for CO2 from the incineration of solvents made from renewable feedstocks significantly reduced the overall carbon footprint. Using this approach, the overall life cycle emissions for production of 1 kg of ecoMeTHF™ were determined to be 0.191 kg, including 0.150 kg of CO2. Life cycle emissions generated from raw material manufacture represents the majority of the overall environmental impact. Our evaluation shows that using 2-methyl tetrahydrofuran in an industrial scenario results in a 97% reduction in emissions, when compared to typically used solvents such as tetrahydrofuran, made through a conventional chemical route.

A medium-chain fatty acid as an alternative energy source in mouse preimplantation development.

PubMed

Yamada, Mitsutoshi; Takanashi, Kazumi; Hamatani, Toshio; Hirayama, Akiyoshi; Akutsu, Hidenori; Fukunaga, Tomoko; Ogawa, Seiji; Sugawara, Kana; Shinoda, Kosaku; Soga, Tomoyoshi; Umezawa, Akihiro; Kuji, Naoaki; Yoshimura, Yasunori; Tomita, Masaru

2012-01-01

To further optimize the culturing of preimplantation embryos, we undertook metabolomic analysis of relevant culture media using capillary electrophoresis time-of-flight mass spectrometry (CE-TOFMS). We detected 28 metabolites: 23 embryo-excreted metabolites including 16 amino acids and 5 media-derived metabolites (e.g., octanoate, a medium-chain fatty acid (MCFA)). Due to the lack of information on MCFAs in mammalian preimplantation development, this study examined octanoate as a potential alternative energy source for preimplantation embryo cultures. No embryos survived in culture media lacking FAs, pyruvate, and glucose, but supplementation of octanoate rescued the embryonic development. Immunoblotting showed significant expression of acyl-CoA dehydrogenase and hydroxyacyl-CoA dehydrogenase, important enzymes for ß-oxidation of MCFAs, in preimplantation embryo. Furthermore, CE-TOFMS traced [1-(13)C(8)] octanoate added to the culture media into intermediate metabolites of the TCA cycle via ß-oxidation in mitochondria. These results are the first demonstration that octanoate could provide an efficient alternative energy source throughout preimplantation development.

Intermediate P* from soluble methane monooxygenase contains a diferrous cluster.

PubMed

Banerjee, Rahul; Meier, Katlyn K; Münck, Eckard; Lipscomb, John D

2013-06-25

During a single turnover of the hydroxylase component (MMOH) of soluble methane monooxygenase from Methylosinus trichosporium OB3b, several discrete intermediates are formed. The diiron cluster of MMOH is first reduced to the Fe(II)Fe(II) state (H(red)). O₂ binds rapidly at a site away from the cluster to form the Fe(II)Fe(II) intermediate O, which converts to an Fe(III)Fe(III)-peroxo intermediate P and finally to the Fe(IV)Fe(IV) intermediate Q. Q binds and reacts with methane to yield methanol and water. The rate constants for these steps are increased by a regulatory protein, MMOB. Previously reported transient kinetic studies have suggested that an intermediate P* forms between O and P in which the g = 16 EPR signal characteristic of the reduced diiron cluster of H(red) and O is lost. This was interpreted as signaling oxidation of the cluster, but a low level of accumulation of P* prevented further characterization. In this study, three methods for directly detecting and trapping P* are applied together to allow its spectroscopic and kinetic characterization. First, the MMOB mutant His33Ala is used to specifically slow the decay of P* without affecting its formation rate, leading to its nearly quantitative accumulation. Second, spectra-kinetic data collection is used to provide a sensitive measure of the formation and decay rate constants of intermediates as well as their optical spectra. Finally, the substrate furan is included to react with Q and quench its strong chromophore. The optical spectrum of P* closely mimics those of H(red) and O, but it is distinctly different from that of P. The reaction cycle rate constants allowed prediction of the times for maximal accumulation of the intermediates. Mössbauer spectra of rapid freeze-quench samples at these times show that the intermediates are formed at almost exactly the predicted levels. The Mössbauer spectra show that the diiron cluster of P*, quite unexpectedly, is in the Fe(II)Fe(II) state. Thus, the

Outcome after reduced chemotherapy for intermediate-risk neuroblastoma.

PubMed

Baker, David L; Schmidt, Mary L; Cohn, Susan L; Maris, John M; London, Wendy B; Buxton, Allen; Stram, Daniel; Castleberry, Robert P; Shimada, Hiroyuki; Sandler, Anthony; Shamberger, Robert C; Look, A Thomas; Reynolds, C Patrick; Seeger, Robert C; Matthay, Katherine K

2010-09-30

The survival rate among patients with intermediate-risk neuroblastoma who receive dose-intensive chemotherapy is excellent, but the survival rate among patients who receive reduced doses of chemotherapy for shorter periods of time is not known. We conducted a prospective, phase 3, nonrandomized trial to determine whether a 3-year estimated overall survival of more than 90% could be maintained with reductions in the duration of therapy and drug doses, using a tumor biology-based therapy assignment. Eligible patients had newly diagnosed, intermediate-risk neuroblastoma without MYCN amplification; these patients included infants (<365 days of age) who had stage 3 or 4 disease, children (≥365 days of age) who had stage 3 tumors with favorable histopathological features, and infants who had stage 4S disease with a diploid DNA index or unfavorable histopathological features. Patients who had disease with favorable histopathological features and hyperdiploidy were assigned to four cycles of chemotherapy, and those with an incomplete response or either unfavorable feature were assigned to eight cycles. Between 1997 and 2005, a total of 479 eligible patients were enrolled in this trial (270 patients with stage 3 disease, 178 with stage 4 disease, and 31 with stage 4S disease). A total of 323 patients had tumors with favorable biologic features, and 141 had tumors with unfavorable biologic features. Ploidy, but not histopathological features, was significantly predictive of the outcome. Severe adverse events without disease progression occurred in 10 patients (2.1%), including secondary leukemia (in 3 patients), death from infection (in 3 patients), and death at surgery (in 4 patients). The 3-year estimate (±SE) of overall survival for the entire group was 96±1%, with an overall survival rate of 98±1% among patients who had tumors with favorable biologic features and 93±2% among patients who had tumors with unfavorable biologic features. A very high rate of survival

Glutamate is the major anaplerotic substrate in the tricarboxylic acid cycle of isolated rumen epithelial and duodenal mucosal cells from beef cattle

USDA-ARS?s Scientific Manuscript database

This study aimed to determine the contribution of substrates to tricarboxylic acid (TCA) cycle fluxes in rumen epithelial (REC) and duodenal mucosal (DMC) cells isolated from bulls (n = 6) fed either a 75% forage (HF) or 75% concentrate (HC) diet. In separate incubations, [13C6]glucose, [13C5]glutam...

The Effect of Limited Diffusion and Wet–Dry Cycling on Reversible Polymerization Reactions: Implications for Prebiotic Synthesis of Nucleic Acids

PubMed Central

Higgs, Paul G.

2016-01-01

A long-standing problem for the origins of life is that polymerization of many biopolymers, including nucleic acids and peptides, is thermodynamically unfavourable in aqueous solution. If bond making and breaking is reversible, monomers and very short oligomers predominate. Recent experiments have shown that wetting and drying cycles can overcome this problem and drive the formation of longer polymers. In the dry phase, bond formation is favourable, but diffusion is restricted, and bonds only form between monomers that are initially close together. In the wet phase, some of the bonds are hydrolyzed. However, repositioning of the molecules allows new bonds to form in the next dry phase, leading to an increase in mean polymer length. Here, we consider a simple theoretical model that explains the effect of cycling. There is an equilibrium length distribution with a high mean length that could be achieved if diffusion occurred freely in the dry phase. This equilibrium is inaccessible without diffusion. A single dry cycle without diffusion leads to mean lengths much shorter than this. Repeated cycling leads to a significant increase in polymerization relative to a single cycle. In the most favourable case, cycling leads to the same equilibrium length distribution as would be achieved if free diffusion were possible in the dry phase. These results support the RNA World scenario by explaining a potential route to synthesis of long RNAs; however, they also imply that cycling would be beneficial to the synthesis of other kinds of polymers, including peptides, where bond formation involves a condensation reaction. PMID:27338479

The Effect of Limited Diffusion and Wet-Dry Cycling on Reversible Polymerization Reactions: Implications for Prebiotic Synthesis of Nucleic Acids.

PubMed

Higgs, Paul G

2016-06-08

A long-standing problem for the origins of life is that polymerization of many biopolymers, including nucleic acids and peptides, is thermodynamically unfavourable in aqueous solution. If bond making and breaking is reversible, monomers and very short oligomers predominate. Recent experiments have shown that wetting and drying cycles can overcome this problem and drive the formation of longer polymers. In the dry phase, bond formation is favourable, but diffusion is restricted, and bonds only form between monomers that are initially close together. In the wet phase, some of the bonds are hydrolyzed. However, repositioning of the molecules allows new bonds to form in the next dry phase, leading to an increase in mean polymer length. Here, we consider a simple theoretical model that explains the effect of cycling. There is an equilibrium length distribution with a high mean length that could be achieved if diffusion occurred freely in the dry phase. This equilibrium is inaccessible without diffusion. A single dry cycle without diffusion leads to mean lengths much shorter than this. Repeated cycling leads to a significant increase in polymerization relative to a single cycle. In the most favourable case, cycling leads to the same equilibrium length distribution as would be achieved if free diffusion were possible in the dry phase. These results support the RNA World scenario by explaining a potential route to synthesis of long RNAs; however, they also imply that cycling would be beneficial to the synthesis of other kinds of polymers, including peptides, where bond formation involves a condensation reaction.

Lactic Acid Bacteria in Durum Wheat Flour Are Endophytic Components of the Plant during Its Entire Life Cycle.

PubMed

Minervini, Fabio; Celano, Giuseppe; Lattanzi, Anna; Tedone, Luigi; De Mastro, Giuseppe; Gobbetti, Marco; De Angelis, Maria

2015-10-01

This study aimed at assessing the dynamics of lactic acid bacteria and other Firmicutes associated with durum wheat organs and processed products. 16S rRNA gene-based high-throughput sequencing showed that Lactobacillus, Streptococcus, Enterococcus, and Lactococcus were the main epiphytic and endophytic genera among lactic acid bacteria. Bacillus, Exiguobacterium, Paenibacillus, and Staphylococcus completed the picture of the core genus microbiome. The relative abundance of each lactic acid bacterium genus was affected by cultivars, phenological stages, other Firmicutes genera, environmental temperature, and water activity (aw) of plant organs. Lactobacilli, showing the highest sensitivity to aw, markedly decreased during milk development (Odisseo) and physiological maturity (Saragolla). At these stages, Lactobacillus was mainly replaced by Streptococcus, Lactococcus, and Enterococcus. However, a key sourdough species, Lactobacillus plantarum, was associated with plant organs during the life cycle of Odisseo and Saragolla wheat. The composition of the sourdough microbiota and the overall quality of leavened baked goods are also determined throughout the phenological stages of wheat cultivation, with variations depending on environmental and agronomic factors. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

Lactic Acid Bacteria in Durum Wheat Flour Are Endophytic Components of the Plant during Its Entire Life Cycle

PubMed Central

Minervini, Fabio; Celano, Giuseppe; Lattanzi, Anna; Tedone, Luigi; De Mastro, Giuseppe; De Angelis, Maria

2015-01-01

This study aimed at assessing the dynamics of lactic acid bacteria and other Firmicutes associated with durum wheat organs and processed products. 16S rRNA gene-based high-throughput sequencing showed that Lactobacillus, Streptococcus, Enterococcus, and Lactococcus were the main epiphytic and endophytic genera among lactic acid bacteria. Bacillus, Exiguobacterium, Paenibacillus, and Staphylococcus completed the picture of the core genus microbiome. The relative abundance of each lactic acid bacterium genus was affected by cultivars, phenological stages, other Firmicutes genera, environmental temperature, and water activity (aw) of plant organs. Lactobacilli, showing the highest sensitivity to aw, markedly decreased during milk development (Odisseo) and physiological maturity (Saragolla). At these stages, Lactobacillus was mainly replaced by Streptococcus, Lactococcus, and Enterococcus. However, a key sourdough species, Lactobacillus plantarum, was associated with plant organs during the life cycle of Odisseo and Saragolla wheat. The composition of the sourdough microbiota and the overall quality of leavened baked goods are also determined throughout the phenological stages of wheat cultivation, with variations depending on environmental and agronomic factors. PMID:26187970

De novo Fatty Acid Biosynthesis Contributes Significantly to Establishment of a Bioenergetically Favorable Environment for Vaccinia Virus Infection

PubMed Central

Greseth, Matthew D.; Traktman, Paula

2014-01-01

The poxvirus life cycle, although physically autonomous from the host nucleus, is nevertheless dependent upon cellular functions. A requirement for de novo fatty acid biosynthesis was implied by our previous demonstration that cerulenin, a fatty acid synthase inhibitor, impaired vaccinia virus production. Here we show that additional inhibitors of this pathway, TOFA and C75, reduce viral yield significantly, with partial rescue provided by exogenous palmitate, the pathway's end-product. Palmitate's major role during infection is not for phospholipid synthesis or protein palmitoylation. Instead, the mitochondrial import and β-oxidation of palmitate are essential, as shown by the impact of etomoxir and trimetazidine, which target these two processes respectively. Moreover, the impact of these inhibitors is exacerbated in the absence of exogenous glucose, which is otherwise dispensable for infection. In contrast to glucose, glutamine is essential for productive viral infection, providing intermediates that sustain the TCA cycle (anaplerosis). Cumulatively, these data suggest that productive infection requires the mitochondrial β-oxidation of palmitate which drives the TCA cycle and energy production. Additionally, infection causes a significant rise in the cellular oxygen consumption rate (ATP synthesis) that is ablated by etomoxir. The biochemical progression of the vaccinia life cycle is not impaired in the presence of TOFA, C75, or etomoxir, although the levels of viral DNA and proteins synthesized are somewhat diminished. However, by reversibly arresting infections at the onset of morphogenesis, and then monitoring virus production after release of the block, we determined that virion assembly is highly sensitive to TOFA and C75. Electron microscopic analysis of cells released into C75 revealed fragmented aggregates of viroplasm which failed to be enclosed by developing virion membranes. Taken together, these data indicate that vaccinia infection, and in

De novo fatty acid biosynthesis contributes significantly to establishment of a bioenergetically favorable environment for vaccinia virus infection.

PubMed

Greseth, Matthew D; Traktman, Paula

2014-03-01

The poxvirus life cycle, although physically autonomous from the host nucleus, is nevertheless dependent upon cellular functions. A requirement for de novo fatty acid biosynthesis was implied by our previous demonstration that cerulenin, a fatty acid synthase inhibitor, impaired vaccinia virus production. Here we show that additional inhibitors of this pathway, TOFA and C75, reduce viral yield significantly, with partial rescue provided by exogenous palmitate, the pathway's end-product. Palmitate's major role during infection is not for phospholipid synthesis or protein palmitoylation. Instead, the mitochondrial import and β-oxidation of palmitate are essential, as shown by the impact of etomoxir and trimetazidine, which target these two processes respectively. Moreover, the impact of these inhibitors is exacerbated in the absence of exogenous glucose, which is otherwise dispensable for infection. In contrast to glucose, glutamine is essential for productive viral infection, providing intermediates that sustain the TCA cycle (anaplerosis). Cumulatively, these data suggest that productive infection requires the mitochondrial β-oxidation of palmitate which drives the TCA cycle and energy production. Additionally, infection causes a significant rise in the cellular oxygen consumption rate (ATP synthesis) that is ablated by etomoxir. The biochemical progression of the vaccinia life cycle is not impaired in the presence of TOFA, C75, or etomoxir, although the levels of viral DNA and proteins synthesized are somewhat diminished. However, by reversibly arresting infections at the onset of morphogenesis, and then monitoring virus production after release of the block, we determined that virion assembly is highly sensitive to TOFA and C75. Electron microscopic analysis of cells released into C75 revealed fragmented aggregates of viroplasm which failed to be enclosed by developing virion membranes. Taken together, these data indicate that vaccinia infection, and in

Growth inhibitory effect of 4-phenyl butyric acid on human gastric cancer cells is associated with cell cycle arrest.

PubMed

Li, Long-Zhu; Deng, Hong-Xia; Lou, Wen-Zhu; Sun, Xue-Yan; Song, Meng-Wan; Tao, Jing; Xiao, Bing-Xiu; Guo, Jun-Ming

2012-01-07

To investigate the growth effects of 4-phenyl butyric acid (PBA) on human gastric carcinoma cells and their mechanisms. Moderately-differentiated human gastric carcinoma SGC-7901 and lowly-differentiated MGC-803 cells were treated with 5, 10, 20, 40, and 60 μmol/L PBA for 1-4 d. Cell proliferation was detected using the MTT colorimetric assay. Cell cycle distributions were examined using flow cytometry. The proliferation of gastric carcinoma cells was inhibited by PBA in a dose- and time-dependent fashion. Flow cytometry showed that SGC-7901 cells treated with low concentrations of PBA were arrested at the G₀/G₁ phase, whereas cells treated with high concentrations of PBA were arrested at the G₂/M phase. Although MGC-803 cells treated with low concentrations of PBA were also arrested at the G₀/ G₁ phase, cells treated with high concentrations of PBA were arrested at the S phase. The growth inhibitory effect of PBA on gastric cancer cells is associated with alteration of the cell cycle. For moderately-differentiated gastric cancer cells, the cell cycle was arrested at the G₀ /G₁ and G₂/M phases. For lowly-differentiated gastric cancer cells, the cell cycle was arrested at the G₀/G₁ and S phases.

Electrofishing power requirements in relation to duty cycle

USGS Publications Warehouse

Miranda, L.E.; Dolan, C.R.

2004-01-01

Under controlled laboratory conditions we measured the electrical peak power required to immobilize (i.e., narcotize or tetanize) fish of various species and sizes with duty cycles (i.e., percentage of time a field is energized) ranging from 1.5% to 100%. Electrofishing effectiveness was closely associated with duty cycle. Duty cycles of 10-50% required the least peak power to immobilize fish; peak power requirements increased gradually above 50% duty cycle and sharply below 10%. Small duty cycles can increase field strength by making possible higher instantaneous peak voltages that allow the threshold power needed to immobilize fish to radiate farther away from the electrodes. Therefore, operating within the 10-50% range of duty cycles would allow a larger radius of immobilization action than operating with higher duty cycles. This 10-50% range of duty cycles also coincided with some of the highest margins of difference between the electrical power required to narcotize and that required to tetanize fish. This observation is worthy of note because proper use of duty cycle could help reduce the mortality associated with tetany documented by some authors. Although electrofishing with intermediate duty cycles can potentially increase effectiveness of electrofishing, our results suggest that immobilization response is not fully accounted for by duty cycle because of a potential interaction between pulse frequency and duration that requires further investigation.

Annual cycle and spatial trends in fatty acid composition of suspended particulate organic matter across the Beaufort Sea shelf

NASA Astrophysics Data System (ADS)

Connelly, Tara L.; Businski, Tara N.; Deibel, Don; Parrish, Christopher C.; Trela, Piotr

2016-11-01

Fatty acid profiles of suspended particulate organic matter (POM) were determined over an annual cycle (September 2003 to August 2004) on the Beaufort Sea shelf, Canadian Arctic. Special emphasis was placed on the nutritional quality of the fatty acid pool available to zooplankton by examining spatial and temporal patterns in the proportions of total polyunsaturated fatty acids (PUFA) and the essential fatty acids 22:6n-3 (DHA) and 20:5n-3 (EPA). EPA and DHA were the two most abundant PUFA throughout the study period. A log-ratio multivariate (LRA) analysis revealed strong structure in fatty acid profiles related to season and depth. Dominant fatty acids accounting for the observed trend included 18:5n-3, 18:4n-3, 16:1n-7, 20:5n-3, 18:0 and 20:3n-3. We observed a shift in fatty acid profiles from summer to autumn (e.g., from 16:1n-7 and EPA to 18:5n-3 and 18:4n-3) that likely corresponded to a shift in the relative importance of diatoms versus dinoflagellates, prymnesiophytes and/or prasinophytes to the POM pool. Fatty acid composition during winter was dominated by more refractory saturated fatty acids. A surprising finding was the depth and seasonal trend of 20:3n-3, which was higher in winter, aligned with 18:0 in the LRA, but behaved differently than other n-3 PUFA. We interpret fatty acid profiles during summer to be predominantly driven by phytoplankton inputs, whereas fatty acid profiles in winter were dominated by fatty acids that were left over after consumption and/or were generated by heterotrophs. The highest diatom inputs (EPA, the diatom fatty acid marker), n-3/n-6 ratios, and C16 PUFA index were located in an upwelling region off Cape Bathurst. This study is the first annual time series of fatty acid profiles of POM in Arctic seas, expanding our knowledge of the composition of POM throughout the dark season.

The influence of alternative pathways of respiration that utilize branched-chain amino acids following water shortage in Arabidopsis.

PubMed

Pires, Marcel V; Pereira Júnior, Adilson A; Medeiros, David B; Daloso, Danilo M; Pham, Phuong Anh; Barros, Kallyne A; Engqvist, Martin K M; Florian, Alexandra; Krahnert, Ina; Maurino, Veronica G; Araújo, Wagner L; Fernie, Alisdair R

2016-06-01

During dark-induced senescence isovaleryl-CoA dehydrogenase (IVDH) and D-2-hydroxyglutarate dehydrogenase (D-2HGDH) act as alternate electron donors to the ubiquinol pool via the electron-transfer flavoprotein/electron-transfer flavoprotein:ubiquinone oxidoreductase (ETF/ETFQO) pathway. However, the role of this pathway in response to other stresses still remains unclear. Here, we demonstrated that this alternative pathway is associated with tolerance to drought in Arabidopsis. In comparison with wild type (WT) and lines overexpressing D-2GHDH, loss-of-function etfqo-1, d2hgdh-2 and ivdh-1 mutants displayed compromised respiration rates and were more sensitive to drought. Our results demonstrated that an operational ETF/ETFQO pathway is associated with plants' ability to withstand drought and to recover growth once water becomes replete. Drought-induced metabolic reprogramming resulted in an increase in tricarboxylic acid (TCA) cycle intermediates and total amino acid levels, as well as decreases in protein, starch and nitrate contents. The enhanced levels of the branched-chain amino acids in loss-of-function mutants appear to be related to their increased utilization as substrates for the TCA cycle under water stress. Our results thus show that mitochondrial metabolism is highly active during drought stress responses and provide support for a role of alternative respiratory pathways within this response. © 2015 John Wiley & Sons Ltd.

Rh(III)-Catalyzed Decarboxylative Coupling of Acrylic Acids with Unsaturated Oxime Esters: Carboxylic Acids Serve as Traceless Activators

PubMed Central

2015-01-01

α,β-Unsaturated carboxylic acids undergo Rh(III)-catalyzed decarboxylative coupling with α,β-unsaturated O-pivaloyl oximes to provide substituted pyridines in good yield. The carboxylic acid, which is removed by decarboxylation, serves as a traceless activating group, giving 5-substituted pyridines with very high levels of regioselectivity. Mechanistic studies rule out a picolinic acid intermediate, and an isolable rhodium complex sheds further light on the reaction mechanism. PMID:24512241

Effect of acetic acid on citric acid fermentation in an integrated citric acid-methane fermentation process.

PubMed

Xu, Jian; Chen, Yang-Qiu; Zhang, Hong-Jian; Tang, Lei; Wang, Ke; Zhang, Jian-Hua; Chen, Xu-Sheng; Mao, Zhong-Gui

2014-09-01

An integrated citric acid-methane fermentation process was proposed to solve the problem of extraction wastewater in citric acid fermentation process. Extraction wastewater was treated by anaerobic digestion and then recycled for the next batch of citric acid fermentation to eliminate wastewater discharge and reduce water resource consumption. Acetic acid as an intermediate product of methane fermentation was present in anaerobic digestion effluent. In this study, the effect of acetic acid on citric acid fermentation was investigated and results showed that lower concentration of acetic acid could promote Aspergillus niger growth and citric acid production. 5-Cyano-2,3-ditolyl tetrazolium chloride (CTC) staining was used to quantify the activity of A. niger cells, and the results suggested that when acetic acid concentration was above 8 mM at initial pH 4.5, the morphology of A. niger became uneven and the part of the cells' activity was significantly reduced, thereby resulting in deceasing of citric acid production. Effects of acetic acid on citric acid fermentation, as influenced by initial pH and cell number in inocula, were also examined. The result indicated that inhibition by acetic acid increased as initial pH declined and was rarely influenced by cell number in inocula.

Overexpression of the Coq8 Kinase in Saccharomyces cerevisiae coq Null Mutants Allows for Accumulation of Diagnostic Intermediates of the Coenzyme Q6 Biosynthetic Pathway*

PubMed Central

Xie, Letian X.; Ozeir, Mohammad; Tang, Jeniffer Y.; Chen, Jia Y.; Jaquinod, Sylvie-Kieffer; Fontecave, Marc; Clarke, Catherine F.; Pierrel, Fabien

2012-01-01

Most of the Coq proteins involved in coenzyme Q (ubiquinone or Q) biosynthesis are interdependent within a multiprotein complex in the yeast Saccharomyces cerevisiae. Lack of only one Coq polypeptide, as in Δcoq strains, results in the degradation of several Coq proteins. Consequently, Δcoq strains accumulate the same early intermediate of the Q6 biosynthetic pathway; this intermediate is therefore not informative about the deficient biosynthetic step in a particular Δcoq strain. In this work, we report that the overexpression of the protein Coq8 in Δcoq strains restores steady state levels of the unstable Coq proteins. Coq8 has been proposed to be a kinase, and we provide evidence that the kinase activity is essential for the stabilizing effect of Coq8 in the Δcoq strains. This stabilization results in the accumulation of several novel Q6 biosynthetic intermediates. These Q intermediates identify chemical steps impaired in cells lacking Coq4 and Coq9 polypeptides, for which no function has been established to date. Several of the new intermediates contain a C4-amine and provide information on the deamination reaction that takes place when para-aminobenzoic acid is used as a ring precursor of Q6. Finally, we used synthetic analogues of 4-hydroxybenzoic acid to bypass deficient biosynthetic steps, and we show here that 2,4-dihydroxybenzoic acid is able to restore Q6 biosynthesis and respiratory growth in a Δcoq7 strain overexpressing Coq8. The overexpression of Coq8 and the use of 4-hydroxybenzoic acid analogues represent innovative tools to elucidate the Q biosynthetic pathway. PMID:22593570

Overexpression of the Coq8 kinase in Saccharomyces cerevisiae coq null mutants allows for accumulation of diagnostic intermediates of the coenzyme Q6 biosynthetic pathway.

PubMed

Xie, Letian X; Ozeir, Mohammad; Tang, Jeniffer Y; Chen, Jia Y; Jaquinod, Sylvie-Kieffer; Fontecave, Marc; Clarke, Catherine F; Pierrel, Fabien

2012-07-06

Most of the Coq proteins involved in coenzyme Q (ubiquinone or Q) biosynthesis are interdependent within a multiprotein complex in the yeast Saccharomyces cerevisiae. Lack of only one Coq polypeptide, as in Δcoq strains, results in the degradation of several Coq proteins. Consequently, Δcoq strains accumulate the same early intermediate of the Q(6) biosynthetic pathway; this intermediate is therefore not informative about the deficient biosynthetic step in a particular Δcoq strain. In this work, we report that the overexpression of the protein Coq8 in Δcoq strains restores steady state levels of the unstable Coq proteins. Coq8 has been proposed to be a kinase, and we provide evidence that the kinase activity is essential for the stabilizing effect of Coq8 in the Δcoq strains. This stabilization results in the accumulation of several novel Q(6) biosynthetic intermediates. These Q intermediates identify chemical steps impaired in cells lacking Coq4 and Coq9 polypeptides, for which no function has been established to date. Several of the new intermediates contain a C4-amine and provide information on the deamination reaction that takes place when para-aminobenzoic acid is used as a ring precursor of Q(6). Finally, we used synthetic analogues of 4-hydroxybenzoic acid to bypass deficient biosynthetic steps, and we show here that 2,4-dihydroxybenzoic acid is able to restore Q(6) biosynthesis and respiratory growth in a Δcoq7 strain overexpressing Coq8. The overexpression of Coq8 and the use of 4-hydroxybenzoic acid analogues represent innovative tools to elucidate the Q biosynthetic pathway.

Transcriptional Orchestration of the Global Cellular Response of a Model Pennate Diatom to Diel Light Cycling under Iron Limitation

DOE PAGES

Smith, Sarah R.; Gillard, Jeroen T. F.; Kustka, Adam B.; ...

2016-12-14

Environmental fluctuations affect distribution, growth and abundance of diatoms in nature, with iron (Fe) availability playing a central role. Studies on the response of diatoms to low Fe have either utilized continuous (24 hr) illumination or sampled a single time of day, missing any temporal dynamics. We profiled the physiology, metabolite composition, and global transcripts of the pennate diatom Phaeodactylum tricornutum during steady-state growth at low, intermediate, and high levels of dissolved Fe over light:dark cycles, to better understand fundamental aspects of genetic control of physiological acclimation to growth under Fe-limitation. We greatly expand the catalog of genes involved inmore » the low Fe response, highlighting the importance of intracellular trafficking in Fe-limited diatoms. P. tricornutum exhibited transcriptomic hallmarks of slowed growth leading to prolonged periods of cell division/silica deposition, which could impact biogeochemical carbon sequestration in Fe-limited regions. Light harvesting and ribosome biogenesis transcripts were generally reduced under low Fe while transcript levels for genes putatively involved in the acquisition and recycling of Fe were increased. We also noted shifts in expression towards increased synthesis and catabolism of branched chain amino acids in P. tricornutum grown at low Fe whereas expression of genes involved in central core metabolism were relatively unaffected, indicating that essential cellular function is protected. Beyond the response of P. tricornutum to low Fe, we observed major coordinated shifts in transcript control of primary and intermediate metabolism over light:dark cycles which contribute to a new view of the significance of distinctive diatom pathways, such as mitochondrial glycolysis and the ornithine-urea cycle. This study provides new insight into transcriptional modulation of diatom physiology and metabolism across light:dark cycles in response to Fe availability, providing

Transcriptional Orchestration of the Global Cellular Response of a Model Pennate Diatom to Diel Light Cycling under Iron Limitation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smith, Sarah R.; Gillard, Jeroen T. F.; Kustka, Adam B.

Environmental fluctuations affect distribution, growth and abundance of diatoms in nature, with iron (Fe) availability playing a central role. Studies on the response of diatoms to low Fe have either utilized continuous (24 hr) illumination or sampled a single time of day, missing any temporal dynamics. We profiled the physiology, metabolite composition, and global transcripts of the pennate diatom Phaeodactylum tricornutum during steady-state growth at low, intermediate, and high levels of dissolved Fe over light:dark cycles, to better understand fundamental aspects of genetic control of physiological acclimation to growth under Fe-limitation. We greatly expand the catalog of genes involved inmore » the low Fe response, highlighting the importance of intracellular trafficking in Fe-limited diatoms. P. tricornutum exhibited transcriptomic hallmarks of slowed growth leading to prolonged periods of cell division/silica deposition, which could impact biogeochemical carbon sequestration in Fe-limited regions. Light harvesting and ribosome biogenesis transcripts were generally reduced under low Fe while transcript levels for genes putatively involved in the acquisition and recycling of Fe were increased. We also noted shifts in expression towards increased synthesis and catabolism of branched chain amino acids in P. tricornutum grown at low Fe whereas expression of genes involved in central core metabolism were relatively unaffected, indicating that essential cellular function is protected. Beyond the response of P. tricornutum to low Fe, we observed major coordinated shifts in transcript control of primary and intermediate metabolism over light:dark cycles which contribute to a new view of the significance of distinctive diatom pathways, such as mitochondrial glycolysis and the ornithine-urea cycle. This study provides new insight into transcriptional modulation of diatom physiology and metabolism across light:dark cycles in response to Fe availability, providing

Effect of various intermediate ceramic layers on the interfacial stability of zirconia core and veneering ceramics.

PubMed

Yoon, Hyung-In; Yeo, In-Sung; Yi, Yang-Jin; Kim, Sung-Hun; Lee, Jai-Bong; Han, Jung-Suk

2015-01-01

The purposes of this study were to evaluate the effects of intermediate ceramics on the adhesion between the zirconia core and veneer ceramics. The polished surfaces of fully sintered Y-TZP blocks received three different treatments: (1) connector (C), (2) liner (L) or (3) wash layer (W). All the treated zirconia blocks were veneered with either (a) fluorapatite glass-ceramic (E) or (b) feldspathic porcelain (V) and divided into four groups (CE, CV, LE and WV). For the control group, the testing surfaces of metal blocks were veneered with feldspathic porcelain (VM). A half of the samples in each group (n = 21) were exposed to thermocycling, while the other half of the specimens were stored at room temperature under dry conditions. All specimens were subjected to the shear test and the failed surfaces were microscopically examined. The elemental distribution at the zirconia core/veneer interface was analyzed. The specimens in Groups CE and CV exhibited significantly greater mean bond strength values than those in Groups LE and WV, respectively (p < 0.05). However, the mean bond strengths significantly decreased in the connector groups (CE and CV) after thermal cycling (p < 0.05). The elemental analysis suggested diffusion of ceramic substances into the zirconia surface. A glass-ceramic based connector is significantly more favorable to core/veneer adhesion than the other intermediate ceramics evaluated in the study. However, thermal cycling affected the bond strength at the core/veneer interface differently according to the intermediate ceramics.

Reactivity of Nucleic Acid Radicals

PubMed Central

Greenberg, Marc M.

2016-01-01

Nucleic acid oxidation plays a vital role in the etiology and treatment of diseases, as well as aging. Reagents that oxidize nucleic acids are also useful probes of the biopolymers’ structure and folding. Radiation scientists have contributed greatly to our understanding of nucleic acid oxidation using a variety of techniques. During the past two decades organic chemists have applied the tools of synthetic and mechanistic chemistry to independently generate and study the reactive intermediates produced by ionizing radiation and other nucleic acid damaging agents. This approach has facilitated resolving mechanistic controversies and lead to the discovery of new reactive processes. PMID:28529390

Gluconeogenesis is associated with high rates of tricarboxylic acid and pyruvate cycling in fasting northern elephant seals.

PubMed

Champagne, Cory D; Houser, Dorian S; Fowler, Melinda A; Costa, Daniel P; Crocker, Daniel E

2012-08-01

Animals that endure prolonged periods of food deprivation preserve vital organ function by sparing protein from catabolism. Much of this protein sparing is achieved by reducing metabolic rate and suppressing gluconeogenesis while fasting. Northern elephant seals (Mirounga angustirostris) endure prolonged fasts of up to 3 mo at multiple life stages. During these fasts, elephant seals maintain high levels of activity and energy expenditure associated with breeding, reproduction, lactation, and development while maintaining rates of glucose production typical of a postabsorptive mammal. Therefore, we investigated how fasting elephant seals meet the requirements of glucose-dependent tissues while suppressing protein catabolism by measuring the contribution of glycogenolysis, glycerol, and phosphoenolpyruvate (PEP) to endogenous glucose production (EGP) during their natural 2-mo postweaning fast. Additionally, pathway flux rates associated with the tricarboxylic acid (TCA) cycle were measured specifically, flux through phosphoenolpyruvate carboxykinase (PEPCK) and pyruvate cycling. The rate of glucose production decreased during the fast (F(1,13) = 5.7, P = 0.04) but remained similar to that of postabsorptive mammals. The fractional contributions of glycogen, glycerol, and PEP did not change with fasting; PEP was the primary gluconeogenic precursor and accounted for ∼95% of EGP. This large contribution of PEP to glucose production occurred without substantial protein loss. Fluxes through the TCA cycle, PEPCK, and pyruvate cycling were higher than reported in other species and were the most energetically costly component of hepatic carbohydrate metabolism. The active pyruvate recycling fluxes detected in elephant seals may serve to rectify gluconeogeneic PEP production during restricted anaplerotic inflow in these fasting-adapted animals.

Salinity Variations of the Intermediate Oyashio Waters and Their Relation with the Lunar Nodal Cycle

NASA Astrophysics Data System (ADS)

Rogachev, K. A.; Shlyk, N. V.

2018-01-01

New oceanographic observations in the period 1990-2015 revealed significant salinity variations in the Oyashio Current. In the last 26 years, the salinity of the upper layer decreased by 0.2 PSU. The most rapid changes in salinity and temperature have been observed in the last five years. The time series of salinity measurements is characterized by the high-amplitude fluctuations synchronized with the lunar nodal cycle (18.6 years); i.e., high salinity is observed in the period of strong tidal currents. Modulation of diurnal tidal currents with the K1 and O1 periods in the lunar nodal cycle is significant [8, 9]. The amplitude was maximal in 1988 and 2006 and minimal in 1997 and 2015. The characteristics of tidal currents in the Oyashio Current and Sea of Okhotsk are considered based on available data of drifting buoys over the Kruzenshtern and Kashevarov banks. The amplitude of salinity variations synchronized with the lunar cycle is approximately 0.1 PSU; therefore, it has made a significant contribution to the salinity decrease in recent years.

Remodeling of intermediate metabolism in the diatom Phaeodactylum tricornutum under nitrogen stress

PubMed Central

Levitan, Orly; Dinamarca, Jorge; Zelzion, Ehud; Lun, Desmond S.; Guerra, L. Tiago; Kim, Min Kyung; Kim, Joomi; Van Mooy, Benjamin A. S.; Bhattacharya, Debashish; Falkowski, Paul G.

2015-01-01

Diatoms are unicellular algae that accumulate significant amounts of triacylglycerols as storage lipids when their growth is limited by nutrients. Using biochemical, physiological, bioinformatics, and reverse genetic approaches, we analyzed how the flux of carbon into lipids is influenced by nitrogen stress in a model diatom, Phaeodactylum tricornutum. Our results reveal that the accumulation of lipids is a consequence of remodeling of intermediate metabolism, especially reactions in the tricarboxylic acid and the urea cycles. Specifically, approximately one-half of the cellular proteins are cannibalized; whereas the nitrogen is scavenged by the urea and glutamine synthetase/glutamine 2-oxoglutarate aminotransferase pathways and redirected to the de novo synthesis of nitrogen assimilation machinery, simultaneously, the photobiological flux of carbon and reductants is used to synthesize lipids. To further examine how nitrogen stress triggers the remodeling process, we knocked down the gene encoding for nitrate reductase, a key enzyme required for the assimilation of nitrate. The strain exhibits 40–50% of the mRNA copy numbers, protein content, and enzymatic activity of the wild type, concomitant with a 43% increase in cellular lipid content. We suggest a negative feedback sensor that couples photosynthetic carbon fixation to lipid biosynthesis and is regulated by the nitrogen assimilation pathway. This metabolic feedback enables diatoms to rapidly respond to fluctuations in environmental nitrogen availability. PMID:25548193

Loss of Mitochondrial Pyruvate Carrier 2 in Liver Leads to Defects in Gluconeogenesis and Compensation via Pyruvate-Alanine Cycling

PubMed Central

McCommis, Kyle S.; Chen, Zhouji; Fu, Xiaorong; McDonald, William G.; Colca, Jerry R.; Kletzien, Rolf F.; Burgess, Shawn C.; Finck, Brian N.

2015-01-01

SUMMARY Pyruvate transport across the inner mitochondrial membrane is believed to be a prerequisite step for gluconeogenesis in hepatocytes, which is important for maintenance of normoglycemia during prolonged food deprivation, but also contributes to hyperglycemia in diabetes. To determine the requirement for mitochondrial pyruvate import in gluconeogenesis, mice with liver-specific deletion of mitochondrial pyruvate carrier 2 (LS-Mpc2−/−) were generated. Loss of MPC2 impaired, but did not completely abolish, hepatocyte pyruvate metabolism, labelled pyruvate conversion to TCA cycle intermediates and glucose, and glucose production from pyruvate. Unbiased metabolomic analyses of livers from fasted LS-Mpc2−/− mice suggested that alterations in amino acid metabolism, including pyruvate-alanine cycling, might compensate for loss of MPC2. Indeed, inhibition of pyruvate-alanine transamination further reduced mitochondrial pyruvate metabolism and glucose production by LS-Mpc2−/− hepatocytes. These data demonstrate an important role for MPC2 in controlling hepatic gluconeogenesis and illuminate a compensatory mechanism for circumventing a block in mitochondrial pyruvate import. PMID:26344101

Effects of continuous triiodothyronine infusion on the tricarboxylic acid cycle in the normal immature swine heart under extracorporeal membrane oxygenation in vivo

PubMed Central

Kajimoto, Masaki; O'Kelly Priddy, Colleen M.; Ledee, Dolena R.; Xu, Chun; Isern, Nancy; Olson, Aaron K.

2014-01-01

Extracorporeal membrane oxygenation (ECMO) is frequently used in infants with postoperative cardiopulmonary failure. ECMO also suppresses circulating triiodothyronine (T3) levels and modifies myocardial metabolism. We assessed the hypothesis that T3 supplementation reverses ECMO-induced metabolic abnormalities in the immature heart. Twenty-two male Yorkshire pigs (age: 25–38 days) with ECMO received [2-13C]lactate, [2,4,6,8-13C4]octanoate (medium-chain fatty acid), and [U-13C]long-chain fatty acids as metabolic tracers either systemically (totally physiological intracoronary concentration) or directly into the coronary artery (high substrate concentration) for the last 60 min of each protocol. NMR analysis of left ventricular tissue determined the fractional contribution of these substrates to the tricarboxylic acid cycle. Fifty percent of the pigs in each group received intravenous T3 supplement (bolus at 0.6 μg/kg and then continuous infusion at 0.2 μg·kg−1·h−1) during ECMO. Under both substrate loading conditions, T3 significantly increased the fractional contribution of lactate with a marginal increase in the fractional contribution of octanoate. Both T3 and high substrate provision increased the myocardial energy status, as indexed by phosphocreatine concentration/ATP concentration. In conclusion, T3 supplementation promoted lactate metabolism to the tricarboxylic acid cycle during ECMO, suggesting that T3 releases the inhibition of pyruvate dehydrogenase. Manipulation of substrate utilization by T3 may be used therapeutically during ECMO to improve the resting energy state and facilitate weaning. PMID:24531815

Effects of continuous triiodothyronine infusion on the tricarboxylic acid cycle in the normal immature swine heart under extracorporeal membrane oxygenation in vivo.

PubMed

Kajimoto, Masaki; Priddy, Colleen M O'Kelly; Ledee, Dolena R; Xu, Chun; Isern, Nancy; Olson, Aaron K; Portman, Michael A

2014-04-15

Extracorporeal membrane oxygenation (ECMO) is frequently used in infants with postoperative cardiopulmonary failure. ECMO also suppresses circulating triiodothyronine (T3) levels and modifies myocardial metabolism. We assessed the hypothesis that T3 supplementation reverses ECMO-induced metabolic abnormalities in the immature heart. Twenty-two male Yorkshire pigs (age: 25-38 days) with ECMO received [2-(13)C]lactate, [2,4,6,8-(13)C4]octanoate (medium-chain fatty acid), and [U-(13)C]long-chain fatty acids as metabolic tracers either systemically (totally physiological intracoronary concentration) or directly into the coronary artery (high substrate concentration) for the last 60 min of each protocol. NMR analysis of left ventricular tissue determined the fractional contribution of these substrates to the tricarboxylic acid cycle. Fifty percent of the pigs in each group received intravenous T3 supplement (bolus at 0.6 μg/kg and then continuous infusion at 0.2 μg·kg(-1)·h(-1)) during ECMO. Under both substrate loading conditions, T3 significantly increased the fractional contribution of lactate with a marginal increase in the fractional contribution of octanoate. Both T3 and high substrate provision increased the myocardial energy status, as indexed by phosphocreatine concentration/ATP concentration. In conclusion, T3 supplementation promoted lactate metabolism to the tricarboxylic acid cycle during ECMO, suggesting that T3 releases the inhibition of pyruvate dehydrogenase. Manipulation of substrate utilization by T3 may be used therapeutically during ECMO to improve the resting energy state and facilitate weaning.

Storage Stability and Improvement of Intermediate Moisture Foods, Phase 3

NASA Technical Reports Server (NTRS)

Labuza, T. P.

1975-01-01

Methods were determined for the improvement of shelf-life stability of intermediate moisture foods (IMF). Microbial challenge studies showed that protection against molds and Staphylococcus aureus could be achieved by a combination of antimicrobial agents, humectants and food acids. Potassium sorbate and propylene glycol gave the best results. It was also confirmed that the maximum in heat resistance shown by vegetative pathogens at intermediate water activities also occurred in a solid food. Glycols and sorbitol both achieve browning inhibition because of their action as a medium for reaction and effect on viscosity of the adsorbed phase. Chemical availability results showed rapid lysine loss before visual discoloration occurred. This is being confirmed with a biological test using Tetrahymena pyriformis W. Accelerated temperature tests show that effectiveness of food antioxidants against rancidity development can be predicted; however, the protection factor changes with temperature. BHA was found to be the best antioxidant for iron catalyzed oxidation.

Physiology of Growth and Sporulation in Bacillus cereus I. Effect of Glutamic and Other Amino Acids

PubMed Central

Buono, F.; Testa, R.; Lundgren, D. G.

1966-01-01

Buono, F. (Syracuse University, Syracuse, N.Y.), R. Testa, and D. G. Lundgren. Physiology of growth and sporulation in Bacillus cereus. I. Effect of glutamic and other amino acids. J. Bacteriol. 91:2291–2299. 1966.—Growth and sporulation were studied in Bacillus cereus by use of an active culture technique and a synthetic medium. A high level of glutamic acid (70 mm) was required for optimal growth and glucose oxidation followed by sporulation even though relatively little glutamic acid was consumed (14 mm). Optimal growth occurred with a combination of 14 mm glutamic acid and 56 mm (NH4)2SO4, aspartic acid, or alanine. Ornithine or arginine at 70 mm could replace glutamic acid in the synthetic medium without affecting the normal growth cycle. Glutamic acid was not replaced by any other amino acid, by (NH4)2SO4, or by a combination of either α-ketoglutarate or pyruvate plus (NH4)2SO4. Enzyme assays of cell-free extracts prepared from cells harvested at different times were used to study the metabolism of glutamic acid. Glutamic-oxaloacetic and glutamic-pyruvate transaminases were completely activated (or derepressed) during early stages of sporulation (period of 6 to 8 hr). Alanine dehydrogenase responded in a similar manner, but the levels of this enzyme were much higher throughout the culture cycle. Neither glutamic dehydrogenase nor α-ketoglutarate dehydrogenase was detected. Sporulation in a replacement salts medium was studied with cells harvested at different times from the synthetic medium. Cultures 2 to 6 hr old were unable to sporulate in the replacement salts medium unless glutamic acid (7.0 mm) was present. By the 6th hr, cells were in the early stages of sporulation, showing spore septa development. Cultures 8 hr old sporulated in the replacement salts medium. Other metabolic intermediates able to replace glutamic acid in the replacement salts medium were alanine, aspartic acid, and glutamine at equimolar concentrations. Also, ammonium ions in

History of the discovery of the life cycle of Toxoplasma gondii.

PubMed

Dubey, J P

2009-07-01

It has been 100 years since the discovery of Toxoplasma gondii in 1908. Its full life cycle was not discovered until 1970 when it was found that it is a coccidian parasite of cats with all non-feline warm blooded animals (including humans) as intermediate hosts. The discovery of the environmentally resistant stage of the parasite, the oocyst, made it possible to explain its worldwide prevalence. In the present paper, events associated with the discovery of its life cycle are recalled.

Lipoic acid metabolism and mitochondrial redox regulation.

PubMed

Solmonson, Ashley D; DeBerardinis, Ralph J

2017-11-30

Lipoic acid is an essential cofactor for mitochondrial metabolism and is synthesized de novo using intermediates from mitochondrial fatty acid synthesis type II, S-adenosylmethionine and iron-sulfur clusters. This cofactor is required for catalysis by multiple mitochondrial 2-ketoacid dehydrogenase complexes, including pyruvate dehydrogenase, alpha-ketoglutarate dehydrogenase, and branched-chain ketoacid dehydrogenase. Lipoic acid also plays a critical role in stabilizing and regulating these multi-enzyme complexes.  Many of these dehydrogenases are regulated by reactive oxygen species, mediated through the disulfide bond of the prosthetic lipoyl moiety.  Collectively, its functions explain why lipoic acid is required for cell growth, mitochondrial activity and coordination of fuel metabolism. Lipoic acid is an essential cofactor for mitochondrial metabolism and is synthesized de novo using intermediates from mitochondrial fatty acid synthesis type II, S-adenosylmethionine and iron-sulfur clusters. This cofactor is required for catalysis by multiple mitochondrial 2-ketoacid dehydrogenase complexes, including pyruvate dehydrogenase, alpha-ketoglutarate dehydrogenase, and branched-chain ketoacid dehydrogenase. Lipoic acid also plays a critical role in stabilizing and regulating these multi-enzyme complexes.  Many of these dehydrogenases are regulated by reactive oxygen species, mediated through the disulfide bond of the prosthetic lipoyl moiety.  Collectively, its functions explain why lipoic acid is required for cell growth, mitochondrial activity and coordination of fuel metabolism. Copyright © 2017, The American Society for Biochemistry and Molecular Biology.

Glycyrrhizin and glycyrrhetinic acid inhibits alpha-naphthyl isothiocyanate-induced liver injury and bile acid cycle disruption.

PubMed

Wang, Haina; Fang, Zhong-Ze; Meng, Ran; Cao, Yun-Feng; Tanaka, Naoki; Krausz, Kristopher W; Gonzalez, Frank J

2017-07-01

Alpha-naphthyl isothiocyanate (ANIT) is a common hepatotoxicant experimentally used to reproduce the pathologies of drug-induced liver injury in humans, but the mechanism of its toxicity remains unclear. To determine the metabolic alterations following ANIT exposure, metabolomic analyses was performed by use of liquid chromatography-mass spectrometry. Partial least squares discriminant analysis (PLS-DA) of liver, serum, bile, ileum, and cecum of vehicle- and ANIT-treated mice revealed significant alterations of individual bile acids, including increased tauroursodeoxycholic acid, taurohydrodeoxycholic acid, taurochenodeoxycholic acid, and taurodeoxycholic acid, and decreased ω-, β- and tauro-α/β- murideoxycholic acid, cholic acid, and taurocholic acid in the ANIT-treated groups. In accordance with these changes, ANIT treatment altered the expression of mRNAs encoded by genes responsible for the metabolism and transport of bile acids and cholesterol. Pre-treatment of glycyrrhizin (GL) and glycyrrhetinic acid (GA) prevented ANIT-induced liver damage and reversed the alteration of bile acid metabolites and Cyp7a1, Npc1l1, Mttp, and Acat2 mRNAs encoding bile acid transport and metabolism proteins. These results suggested that GL/GA could prevent drug-induced liver injury and ensuing disruption of bile acid metabolism in humans. Published by Elsevier B.V.