20 research outputs found

    Mitochondrial lipidomes are tissue specific – low cholesterol contents relate to UCP1 activity

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    Lipid composition is conserved within sub-cellular compartments to maintain cell function. Lipidomic analyses of liver, muscle, white and brown adipose tissue (BAT) mitochondria revealed substantial differences in their glycerophospholipid (GPL) and free cholesterol (FC) contents. The GPL to FC ratio was 50-fold higher in brown than white adipose tissue mitochondria. Their purity was verified by comparison of proteomes with ER and mitochondria-associated membranes. A lipid signature containing PC and FC, calculated from the lipidomic profiles, allowed differentiation of mitochondria from BAT of mice housed at different temperatures. Elevating FC in BAT mitochondria prevented uncoupling protein (UCP) 1 function, whereas increasing GPL boosted it. Similarly, STARD3 overexpression facilitating mitochondrial FC import inhibited UCP1 function in primary brown adipocytes, whereas a knockdown promoted it. We conclude that the mitochondrial GPL/FC ratio is key for BAT function and propose that targeting it might be a promising strategy to promote UCP1 activity

    Mobility in a Globalised World 2016

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    The term mobility has different meanings in the following science disciplines. In economics, mobility is the ability of an individual or a group to improve their economic status in relation to income and wealth within their lifetime or between generations. In information systems and computer science, mobility is used for the concept of mobile computing, in which a computer is transported by a person during normal use. Logistics creates by the design of logistics networks the infrastructure for the mobility of people and goods. Electric mobility is one of today’s solutions from engineering perspective to reduce the need of energy resources and environmental impact. Moreover, for urban planning, mobility is the crunch question about how to optimise the different needs for mobility and how to link different transportation systems. In this publication we collected the ideas of practitioners, researchers, and government officials regarding the different modes of mobility in a globalised world, focusing on both domestic and international issues

    Mobility in a Globalised World 2012

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    The term mobility has different meanings in the following science disciplines. In economics, mobility is the ability of an individual or a group to improve their economic status in relation to income and wealth within their lifetime or between generations. In information systems and computer science, mobility is used for the concept of mobile computing, in which a computer is transported by a person during normal use. By designing logistics networks, logistics creates the infrastructure for the mobility of people and goods. Electric mobility is one of today’s solutions from an engineering perspective to the problem of reducing the need for energy resources and environmental impact. Finally, for urban planning, mobility is the crunch question as to how to optimise the different needs for mobility and how to link different transportation systems. In this publication we have collected the ideas of practitioners, researchers, and government officials about the different modes of mobility in a globalised world, focusing on both domestic and international issues

    GZum neuen Wasserhaushaltsgesetz

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    Energetics and kinetics of lactate fermentation to acetate and propionate via methylmalonyl-CoA or acrylyl-CoA

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    Fermentation balances and growth yields were determined with various bacteria fermenting lactate to acetate plus propionate either via methylmalonyl-CoA or via acrylyl-CoA. All strains fermented lactate to acetate plus propionate at approximately a 1:2 ratio. Growth yields of Propionibacterium freudenreichii were more than twice as high as those of Clostridium homopropionicum or Veillonella parvula. Hydrogen was formed as a side product to a significant extent only by V. parvula and Pelobacter propionicus; the latter formed hydrogen preferentially when using ethanol as substrate. Acrylyl-CoA reductase of C. homopropionicum and Clostridium neopropionicum was found nearly exclusively in the cytoplasm thus confirming that this reduction step is unlikely to be involved in energy conservation. C. homopropionicum exhibited higher KS and higher Wmax values, as well as higher specific substrate turnover rates than P. freudenreichii. The results allow us to conclude that C. homopropionicum using the acrylyl-CoA pathway with low growth yield obtains its specific competitive advantage compared to P. freudenreichii not through higher substrate affinity or metabolic shift toward enhanced acetate-plus-hydrogen formation but through faster specific substrate turnover

    A Periplasmic and Extracellular c-Type Cytochrome of Geobacter sulfurreducens Acts as a Ferric Iron Reductase and as an Electron Carrier to Other Acceptors or to Partner Bacteria

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    An extracellular electron carrier excreted into the growth medium by cells of Geobacter sulfurreducens was identified as a c-type cytochrome. The cytochrome was found to be distributed in about equal amounts in the membrane fraction, the periplasmic space, and the surrounding medium during all phases of growth with acetate plus fumarate. It was isolated from periplasmic preparations and purified to homogeneity by cationexchange chromatography, gel filtration, and hydrophobic interaction chromatography. The electrophoretically homogeneous cytochrome had a molecular mass of 9.57 6 0.02 kDa and exhibited in its reduced state absorption maxima at wavelengths of 552, 522, and 419 nm. The midpoint redox potential determined by redox titration was 20.167 V. With respect to molecular mass, redox properties, and molecular features, this cytochrome exhibited its highest similarity to the cytochromes c of Desulfovibrio salexigens and Desulfuromonas acetoxidans. The G. sulfurreducens cytochrome c reduced ferrihydrite (Fe(OH)3), Fe(III) nitrilotriacetic acid, Fe(III) citrate, and manganese dioxide at high rates. Elemental sulfur, anthraquinone disulfonate, and humic acids were reduced more slowly. G. sulfurreducens reduced the cytochrome with acetate as an electron donor and oxidized it with fumarate. Wolinella succinogenes was able to reduce externally provided cytochrome c of G. sulfurreducens with molecular hydrogen or formate as an electron donor and oxidized it with fumarate or nitrate as an electron acceptor. A coculture could be established in which G. sulfurreducens reduced the cytochrome with acetate, and the reduced cytochrome was reoxidized by W. succinogenes in the presence of nitrate. We conclude that this cytochrome can act as iron(III) reductase for electron transfer to insoluble iron hydroxides or to sulfur, manganese dioxide, or other oxidized compounds, and it can transfer electrons to partner bacteria

    A Periplasmic and Extracellular c-Type Cytochrome of Geobacter sulfurreducens Acts as a Ferric Iron Reductase and as an Electron Carrier to Other Acceptors or to Partner Bacteria

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    An extracellular electron carrier excreted into the growth medium by cells of Geobacter sulfurreducens was identified as a c-type cytochrome. The cytochrome was found to be distributed in about equal amounts in the membrane fraction, the periplasmic space, and the surrounding medium during all phases of growth with acetate plus fumarate. It was isolated from periplasmic preparations and purified to homogeneity by cation-exchange chromatography, gel filtration, and hydrophobic interaction chromatography. The electrophoretically homogeneous cytochrome had a molecular mass of 9.57 ± 0.02 kDa and exhibited in its reduced state absorption maxima at wavelengths of 552, 522, and 419 nm. The midpoint redox potential determined by redox titration was −0.167 V. With respect to molecular mass, redox properties, and molecular features, this cytochrome exhibited its highest similarity to the cytochromes c of Desulfovibrio salexigens and Desulfuromonas acetoxidans. The G. sulfurreducens cytochrome c reduced ferrihydrite (Fe(OH)(3)), Fe(III) nitrilotriacetic acid, Fe(III) citrate, and manganese dioxide at high rates. Elemental sulfur, anthraquinone disulfonate, and humic acids were reduced more slowly. G. sulfurreducens reduced the cytochrome with acetate as an electron donor and oxidized it with fumarate. Wolinella succinogenes was able to reduce externally provided cytochrome c of G. sulfurreducens with molecular hydrogen or formate as an electron donor and oxidized it with fumarate or nitrate as an electron acceptor. A coculture could be established in which G. sulfurreducens reduced the cytochrome with acetate, and the reduced cytochrome was reoxidized by W. succinogenes in the presence of nitrate. We conclude that this cytochrome can act as iron(III) reductase for electron transfer to insoluble iron hydroxides or to sulfur, manganese dioxide, or other oxidized compounds, and it can transfer electrons to partner bacteria

    The fermenting bacterium Malonomonas rubra is phylogenetically related to sulfur-reducing bacteria and contains a c-type cytochrome similar to those of sulfur and sulfate reducers

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    Malonomonas rubra is a microaerotolerant fermenting bacterium which can maintain its energy metabolism for growth by decarboxylation of malonate to acetate. 16S rRNA sequence analysis revealed that M. rubra is closely related to the cluster of mesophilic sulfur-reducing bacteria within the delta subclass of the Proteobacteria, with the fermenting bacterium Pelobacter acidigallici and the sulfur reducers Desulfuromusa kysingii, D. bakii and D. succinoxidans as closest relatives. The cells contain high amounts (up to 12% of the total cell protein content) of a c-type cytochrome which is present mainly (> 60%) in the cytoplasm and to minor parts in the periplasm (> 20%) and associated with the membrane fraction (> 10%), independent of the growth substrate. This cytochrome is a tetraheme cytochrome of 13,700 Da molecular mass with a midpoint redox potential of -0.210 V.M. rubra does not reduce sulfur or ferric iron compounds. Since this cytochrome appears not to be involved in the energy metabolism it is concluded that it is a remnant of sulfur-reducing ancestors of this bacterium, without a conceivable physiological function in its present energy metabolism
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