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  • Health Reference Center Academic (Gale)  (9)
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  • 1
    In: Ecohydrology, January 2016, Vol.9(1), pp.93-100
    Description: We investigated changes in respiration across nighttime and daytime in a headwater stream. For this, we conducted consecutive nighttime and daytime experiments injecting the bioreactive tracer resazurin in two reaches with different riparian canopy densities (different levels of photosynthetically active radiation) to compare respiration rate coefficients. We found that even though stream water temperatures measured above the streambed at day and night (half‐day timescale) were different within each reach and across reaches (95% confidence level), apparent respiration rate coefficients were not different across nighttime and daytime conditions (95% confidence level). A likely explanation for this is that the bulk of stream respiration takes place in the hyporheic zone, where diel fluctuations of stream temperature and photosynthetically active radiation are considerably attenuated and where temperature is not measured in routine investigations of stream metabolism. Our results suggest that community respiration in headwater streams may not need to be ‘corrected’ for temperature between daytime and nighttime, even though instantaneous changes in respiration are expected to occur from a pure biological perspective. Copyright © 2015 John Wiley & Sons, Ltd.
    Keywords: Community Respiration ; Resazurin ; Smart Tracers ; Diel Fluctuations ; Headwater Stream ; Hyporheic Zone ; Stream Temperature ; Stream Metabolism
    ISSN: 1936-0584
    E-ISSN: 1936-0592
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  • 2
    In: European Journal of Personality, November 2018, Vol.32(6), pp.705-720
    Description: The constructs grit and conscientiousness are closely connected. However, this relationship has not been analysed while accounting for the complex structure of conscientiousness and the multifaceted conception of grit (perseverance of effort; consistency of interest). In this study, we analysed the connection while considering the hierarchical structure of conscientiousness, differentiating between a superordinate factor, a first‐level common factor (industriousness), and lower level unique factors. Drawing on two samples ( = 413,  = 15.29, and  = 530,  = 31.75), we applied an extension procedure for confirmatory factor analysis that enables a simultaneous investigation of the relationships on all levels. The perseverance facet of grit was tightly aligned to the common factors (95% shared variance) and was strongly related to the industriousness factor. Consistency shared less variance with the common factors of conscientiousness (53%), but it was additionally correlated with the self‐discipline facet. The results for the global grit scale were most similar to the results for perseverance. Grit appears to be a construct that combines the superordinate and industrious aspects of conscientiousness and shares the unique aspect of the self‐discipline facet; this suggests that grit and its facets can be fully integrated into the hierarchical structure of conscientiousness.
    Keywords: Grit ; Conscientiousness ; Industriousness ; Construct Differentiation ; Extension Procedure For Confirmatory Factor Analysis
    ISSN: 0890-2070
    E-ISSN: 1099-0984
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  • 3
    In: Macromolecular Reaction Engineering, August 2018, Vol.12(4), pp.n/a-n/a
    Description: High molecular weight polyethylene furanoate (PEF) is a potential replacement for polyethylene terephthalate. Ring‐opening‐polymerization of PEF can represent a viable alternative to the classical polycondensation process, provided that a synthesis route is available to supply high purity cycles in high yields. In this work, cyclic oligomers of PEF are produced by cyclodepolymerization (CDP). Reactions are performed in different high boiling solvents and 2‐methylnaphthalene (2‐MN) is chosen as a favorable reaction solvent for a detailed analysis of the reaction equilibrium behavior of cyclic and linear PEF. Such equilibrium can be described by the well‐known model of Jacobson and Stockmayer. The corresponding equilibrium constants are first determined by fitting a set of equilibrium data. Based on this description of the reaction, a kinetic model is then developed and validated by comparison with experimental data. Finally, selective precipitation is shortly explored as a practical purification method which, together with CDP, can enable a large scale process for the production of high purity cyclic PEF oligomers for ring‐opening‐polymerization. for the production of cyclic oligomers of polyethylene furanoate (PEF) is performed. This is the first step in the production of the renewable resource based polymer PEF by ring‐opening polymerization (ROP). Several solvents are examined to evaluate their performance in CDP reactions. Finally a kinetic model is developed and validated, able to describe the equilibration of cyclic and linear oligomers at different concentrations.
    Keywords: Cyclodepolymerization ; Kinetic Modeling ; Renewable Resource Based Polymers
    ISSN: 1862-832X
    E-ISSN: 1862-8338
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  • 4
    Language: English
    In: Nature, 09 July 2014, Vol.513
    Description: Photosynthesis, a process catalysed by plants, algae and cyanobacteria converts sunlight to energy thus sustaining all higher life on Earth. Two large membrane protein complexes, photosystem I and II (PSI and PSII), act in series to catalyse the light-driven reactions in photosynthesis. PSII catalyses the light-driven water splitting process, which maintains the Earth's oxygenic atmosphere. In this process, the oxygen-evolving complex (OEC) of PSII cycles through five states, S0 to S4, in which four electrons are sequentially extracted from the OEC in four light-driven charge-separation events. Here we describe time resolved experiments on PSII nano/microcrystals from Thermosynechococcus elongatus performed with the recently developed technique of serial femtosecond crystallography. Structures have been determined from PSII in the dark S1 state and after double laser excitation (putative S3 state) at 5 and 5.5 Å resolution, respectively. The results provide evidence that PSII undergoes significant conformational changes at the electron acceptor side and at the Mn4CaO5 core of the OEC. These include an elongation of the metal cluster, accompanied by changes in the protein environment, which could allow for binding of the second substrate water molecule between the more distant protruding Mn (referred to as the 'dangler' Mn) and the Mn3CaOx cubane in the S2 to S3 transition, as predicted by spectroscopic and computational studies. This work shows the great potential for time-resolved serial femtosecond crystallography for investigation of catalytic processes in biomolecules.
    Keywords: Catalysis (Homogeneous), Catalysis (Heterogeneous), Solar (Fuels), Photosynthesis (Natural and Artificial), Bio-Inspired, Hydrogen and Fuel Cells, Electrodes - Solar, Charge Transport, Materials and Chemistry By Design, Synthesis (Novel Materials), Synthesis (Self-Assembly)
    ISSN: 00280836
    E-ISSN: 14764687
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  • 5
    Language: English
    In: Science (New York, N.Y.), 15 December 2006, Vol.314(5806), pp.1720-4
    Description: Organics found in comet 81P/Wild 2 samples show a heterogeneous and unequilibrated distribution in abundance and composition. Some organics are similar, but not identical, to those in interplanetary dust particles and carbonaceous meteorites. A class of aromatic-poor organic material is also present. The organics are rich in oxygen and nitrogen compared with meteoritic organics. Aromatic compounds are present, but the samples tend to be relatively poorer in aromatics than are meteorites and interplanetary dust particles. The presence of deuterium and nitrogen-15 excesses suggest that some organics have an interstellar/protostellar heritage. Although the variable extent of modification of these materials by impact capture is not yet fully constrained, a diverse suite of organic compounds is present and identifiable within the returned samples.
    Keywords: Meteoroids ; Organic Chemicals -- Analysis
    ISSN: 00368075
    E-ISSN: 1095-9203
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  • 6
    Language: English
    In: Science (New York, N.Y.), 11 January 2013, Vol.339(6116), pp.227-230
    Description: The Trypanosoma brucei cysteine protease cathepsin B (TbCatB), which is involved in host protein degradation, is a promising target to develop new treatments against sleeping sickness, a fatal disease caused by this protozoan parasite. The structure of the mature, active form of TbCatB has so far not provided sufficient information for the design of a safe and specific drug against T. brucei. By combining two recent innovations, in vivo crystallization and serial femtosecond crystallography, we obtained the room-temperature 2.1 angstrom resolution structure of the fully glycosylated precursor complex of TbCatB. The structure reveals the mechanism of native TbCatB inhibition and demonstrates that new biomolecular information can be obtained by the "diffraction-before-destruction" approach of x-ray free-electron lasers from hundreds of thousands of individual microcrystals.
    Keywords: Cathepsin B -- Chemistry ; Protozoan Proteins -- Chemistry ; Trypanosoma Brucei Brucei -- Enzymology
    ISSN: 00368075
    E-ISSN: 1095-9203
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  • 7
    In: Nature Methods, 2012, Vol.9(3), p.259
    Description: Protein crystallization in cells has been observed several times in nature. However, owing to their small size these crystals have not yet been used for X-ray crystallographic analysis. We prepared nano-sized in vivo-grown crystals of Trypanosoma brucei enzymes and applied the emerging method of free-electron laser-based serial femtosecond crystallography to record interpretable diffraction data. This combined approach will open new opportunities in structural systems biology.
    Keywords: Biology;
    ISSN: 1548-7091
    E-ISSN: 15487105
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  • 8
    In: FEBS Journal, August 2008, Vol.275(16), pp.4097-4110
    Description: The neonatal Fc receptor (FcRn) is a major histocompatibility complex class I‐related molecule that regulates the half‐life of IgG and albumin. In addition, FcRn directs the transport of IgG across both mucosal epithelium and placenta and also enhances phagocytosis in neutrophils. This new knowledge gives incentives for the design of IgG and albumin‐based diagnostics and therapeutics. To study FcRn and to select and characterize FcRn binders, large quantities of soluble human FcRn are needed. In this report, we explored the impact of two free cysteine residues (C48 and C251) of the FcRn heavy chain on the overall structure and function of soluble human FcRn and described an improved bacterial production strategy based on removal of these residues, yielding ∼ 70 mg·L of fermentation of refolded soluble human FcRn. The structural and functional integrity was proved by CD, surface plasmon resonance and MALDI‐TOF peptide mapping analyses. The strategy may generally be translated to the large‐scale production of other major histocompatibility complex class I‐related molecules with nonfunctional unpaired cysteine residues. Furthermore, the anti‐FcRn response in goats immunized with the FcRn heavy chain alone was analyzed following affinity purification on heavy chain‐coupled Sepharose. Importantly, purified antibodies blocked the binding of both ligands to soluble human FcRn and were thus directed to both binding sites. This implies that the FcRn heavy chain, without prior assembly with human β2‐microglobulin, contains the relevant epitopes found in soluble human FcRn, and is therefore sufficient to obtain binders to either ligand‐binding site. This finding will greatly facilitate the selection and characterization of such binders.
    Keywords: Antigenic Properties ; Bacterial Expression ; Maldi‐Tof Peptide Mapping ; Soluble Human Neonatal Fc Receptor Shfcrn ; Unpaired Cysteines
    ISSN: 1742-464X
    E-ISSN: 1742-4658
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  • 9
    Language: English
    In: Nature Methods, 29 January 2012, Vol.9(3)
    Description: X-ray free electron laser (X-FEL)-based serial femtosecond crystallography is an emerging method with potential to rapidly advance the challenging field of membrane protein structural biology. Here we recorded interpretable diffraction data from micrometer-sized lipidic sponge phase crystals of the Blastochloris viridis photosynthetic reaction center delivered into an X-FEL beam using a sponge phase micro-jet.
    Keywords: Catalysis (Homogeneous), Catalysis (Heterogeneous), Solar (Fuels), Photosynthesis (Natural and Artificial), Bio-Inspired, Hydrogen and Fuel Cells, Electrodes - Solar, Charge Transport, Materials and Chemistry By Design, Synthesis (Novel Materials), Synthesis (Self-Assembly) ; Biology
    ISSN: 1548-7091
    E-ISSN: 1548-7105
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