Zuletzt publiziert

  • Zeitschriftenartikel

    Correlative microscopy approach for biology using X-ray holography, X-ray scanning diffraction and STED microscopy 

    Bernhardt, M.; Nicolas, J.-D.; Osterhoff, M.; Mittelstädt, H.; Reuss, M.; Harke, B.; Wittmeier, A.; Sprung, M.; Köster, S.; Salditt, T.
    Nature Communications 2018; 9(1): Art. 3641
    We present a correlative microscopy approach for biology based on holographic X-ray imaging, X-ray scanning diffraction, and stimulated emission depletion (STED) microscopy. All modalities are combined into the same synchrotron endstation. In this way, labeled and unlabeled structures in cells are visualized in a complementary manner. We map out the fluorescently labeled actin cytoskeleton in heart tissue cells and superimpose the data with phase maps from X-ray holography. Furthermore, an array of local far-field diffraction patterns is recorded in the regime of small-angle X-ray scattering (scanning SAXS), which can be interpreted in terms of biomolecular shape and spatial correlations of all contributing scattering constituents. We find that principal directions of anisotropic diffraction patterns coincide to a certain degree with the actin fiber directions and that actin stands out in the phase maps from holographic recordings. In situ STED recordings are proposed to formulate models for diffraction data based on co-localization constraints
    Dokument ansehen Zusammenfassung
  • Zeitschriftenartikel

    Spatial Distribution of Mucilage in the Rhizosphere Measured With Infrared Spectroscopy 

    Holz, Maire; Leue, Martin; Ahmed, Mutez A.; Benard, Pascal; Gerke, Horst H.; Carminati, Andrea
    Frontiers in Environmental Science 2018; 6: Art. 87
    Mucilage is receiving increasing attention because of its putative effects on plant growth, but so far no method is available to measure its spatial distribution in the rhizosphere.We tested whether the C-H signal related to mucilage fatty acids is detectable by infrared spectroscopy and if this method can be used to determine the spatial distribution of mucilage in the rhizosphere. Maize plants were grown in rhizoboxes filled with soil free of organic matter. Infrared measurements were carried out along transects perpendicular as well as axially to the root channels. The perpendicular gradients of the C-H proportions showed a decrease of C-H with increasing distance: 0.8mm apart from the root center the C-H signals achieved a level near zero. The measured concentrations of mucilage were comparable with results obtained in previous studies, which encourages the use of infrared spectroscopy to quantitatively image mucilage in the rhizosphere.
    Dokument ansehen Zusammenfassung
  • Zeitschriftenartikel

    Mixed-species versus monocultures in plantation forestry: Development, benefits, ecosystem services and perspectives for the future 

    Liu, Corsa Lok Ching; Kuchma, Oleksandra; Krutovsky, Konstantin V.
    Global Ecology and Conservation 2018; 15
    Plantation forests are increasing rapidly in the world in order to alleviate deforestation and degradation of natural forests, along with providing various goods and services. While monoculture plantations have been the dominant type of plantation in practice and well-recorded in research, in the face of intensifying climate change and resource scarcity, there is a growing interest in mixed-species plantations. Agroforestry systems are also catching the attention of foresters, smallholders and landowners. However, there are relatively limited number of studies on successful species mixtures. This paper first reviews the progression of monocultures and mixed-species, followed by the comparisons of advantages, disadvantages and effects on the surrounding natural ecosystems between these two types of plantations. The paper further investigates combinations of species with complementary traits for efficient use of limiting resources associated with improvement in growth development and production of tree species, as well as examining some other challenges in mixed-species. In addition, it is helpful to select and combine tree/crop species in mixtures based on complementary traits that maximise positive and minimise negative interactions and using the advance molecular technologies for genetic analysis. With careful design and proper management, mixed-species plantations with two, three or four species can be more productive and have more advantages in biodiversity, economy and forest health over monocultures. Many researchers are still working on different projects to explore the potential benefits and to promote the applications of mixed-species plantations and agroforestry.
    Dokument ansehen Zusammenfassung
  • Zeitschriftenartikel

    Testing the plant pneumatic method to estimate xylem embolism resistance in stems of temperate trees 

    Zhang, Ya; Lamarque, Laurent J.; Torres-Ruiz, José M.; Schuldt, Bernhard; Karimi, Zohreh; Li, Shan; Qin, De-Wen; Bittencourt, Paulo; Burlett, Régis; Cao, Kun-Fang; et al.
    Delzon, SylvainOliveira, RafaelPereira, LucianoJansen, Steven
    Tree Physiology 2018; 38(7) p.1016-1025
    Methods to estimate xylem embolism resistance generally rely on hydraulic measurements, which can be far from straightforward. Recently, a pneumatic method based on air flow measurements of terminal branch ends was proposed to construct vulnerability curves by linking the amount of air extracted from a branch with the degree of embolism. We applied this novel technique for 10 temperate tree species, including six diffuse, two ring-porous and two gymnosperm species, and compared the pneumatic curves with hydraulic ones obtained from either the flow-centrifuge or the hydraulic-bench dehydration method. We found that the pneumatic method provides a good estimate of the degree of xylem embolism for all angiosperm species. The xylem pressure at 50% and 88% loss of hydraulic conductivity (i.e., Ψ50 and Ψ88) based on the methods applied showed a strongly significant correlation for all eight angiosperms. However, the pneumatic method showed significantly reduced Ψ50 values for the two conifers. Our findings suggest that the pneumatic method could provide a fast and accurate approach for angiosperms due to its convenience and feasibility, at least within the range of embolism resistances covered by our samples.
    Dokument ansehen Zusammenfassung
  • Zeitschriftenartikel

    Disentangling Transient Charge Density and Metal-Ligand Covalency in Photoexcited Ferricyanide with Femtosecond Resonant Inelastic Soft X-ray Scattering. 

    Jay, Raphael M.; Norell, Jesper; Eckert, Sebastian; Hantschmann, Markus; Beye, Martin; Kennedy, Brian; Quevedo, Wilson; Schlotter, William F.; Dakovski, Georgi L.; Minitti, Michael P.; et al.
    Hoffmann, Matthias C.Mitra, AnkushMoeller, Stefan P.Nordlund, DennisZhang, WenkaiLiang, Huiyang W.Kunnus, KristjanKubiček, KatharinaTechert, Simone A.Lundberg, MarcusWernet, PhilippeGaffney, KellyOdelius, MichaelFöhlisch, Alexander
    The Journal of Physical Chemistry Letters 2018; 9(12) p.3538-3543
    Soft X-ray spectroscopies are ideal probes of the local valence electronic structure of photocatalytically active metal sites. Here, we apply the selectivity of time-resolved resonant inelastic X-ray scattering at the iron L-edge to the transient charge distribution of an optically excited charge-transfer state in aqueous ferricyanide. Through comparison to steady-state spectra and quantum chemical calculations, the coupled effects of valence-shell closing and ligand-hole creation are experimentally and theoretically disentangled and described in terms of orbital occupancy, metal-ligand covalency, and ligand field splitting, thereby extending established steady-state concepts to the excited-state domain. π-Back-donation is found to be mainly determined by the metal site occupation, whereas the ligand hole instead influences σ-donation. Our results demonstrate how ultrafast resonant inelastic X-ray scattering can help characterize local charge distributions around catalytic metal centers in short-lived charge-transfer excited states, as a step toward future rationalization and tailoring of photocatalytic capabilities of transition-metal complexes.
    Dokument ansehen Zusammenfassung
  • Zeitschriftenartikel

    Assigning crystallographic electron densities with free energy calculations-The case of the fluoride channel Fluc. 

    Ariz-Extreme, Igor; Hub, Jochen S.
    PLOS ONE 2018; 13(5): Art. e0196751
    Approximately 90% of the structures in the Protein Data Bank (PDB) were obtained by X-ray crystallography or electron microscopy. Whereas the overall quality of structure is considered high, thanks to a wide range of tools for structure validation, uncertainties may arise from density maps of small molecules, such as organic ligands, ions or water, which are non-covalently bound to the biomolecules. Even with some experience and chemical intuition, the assignment of such disconnected electron densities is often far from obvious. In this study, we suggest the use of molecular dynamics (MD) simulations and free energy calculations, which are well-established computational methods, to aid in the assignment of ambiguous disconnected electron densities. Specifically, estimates of (i) relative binding affinities, for instance between an ion and water, (ii) absolute binding free energies, i.e., free energies for transferring a solute from bulk solvent to a binding site, and (iii) stability assessments during equilibrium simulations may reveal the most plausible assignments. We illustrate this strategy using the crystal structure of the fluoride specific channel (Fluc), which contains five disconnected electron densities previously interpreted as four fluoride and one sodium ion. The simulations support the assignment of the sodium ion. In contrast, calculations of relative and absolute binding free energies as well as stability assessments during free MD simulations suggest that four of the densities represent water molecules instead of fluoride. The assignment of water is compatible with the loss of these densities in the non-conductive F82I/F85I mutant of Fluc. We critically discuss the role of the ion force fields for the calculations presented here. Overall, these findings indicate that MD simulations and free energy calculations are helpful tools for modeling water and ions into crystallographic density maps.
    Dokument ansehen Zusammenfassung
  • Zeitschriftenartikel

    Velvet domain protein VosA represses the zinc cluster transcription factor SclB regulatory network for Aspergillus nidulans asexual development, oxidative stress response and secondary metabolism. 

    Thieme, Karl G.; Gerke, Jennifer; Sasse, Christoph; Valerius, Oliver; Thieme, Sabine; Karimi, Razieh; Heinrich, Antje K.; Finkernagel, Florian; Smith, Kristina; Bode, Helge B.; et al.
    Freitag, MichaelRam, Arthur F. J.Braus, Gerhard H.
    PLOS Genetics 2018; 14(7): Art. e1007511
    The NF-κB-like velvet domain protein VosA (viability of spores) binds to more than 1,500 promoter sequences in the filamentous fungus Aspergillus nidulans. VosA inhibits premature induction of the developmental activator gene brlA, which promotes asexual spore formation in response to environmental cues as light. VosA represses a novel genetic network controlled by the sclB gene. SclB function is antagonistic to VosA, because it induces the expression of early activator genes of asexual differentiation as flbC and flbD as well as brlA. The SclB controlled network promotes asexual development and spore viability, but is independent of the fungal light control. SclB interactions with the RcoA transcriptional repressor subunit suggest additional inhibitory functions on transcription. SclB links asexual spore formation to the synthesis of secondary metabolites including emericellamides, austinol as well as dehydroaustinol and activates the oxidative stress response of the fungus. The fungal VosA-SclB regulatory system of transcription includes a VosA control of the sclB promoter, common and opposite VosA and SclB control functions of fungal development and several additional regulatory genes. The relationship between VosA and SclB illustrates the presence of a convoluted surveillance apparatus of transcriptional control, which is required for accurate fungal development and the linkage to the appropriate secondary metabolism.
    Dokument ansehen Zusammenfassung
  • Zeitschriftenartikel

    Crystal Structure of the Human tRNA Guanine Transglycosylase Catalytic Subunit QTRT1 

    Johannsson, Sven; Neumann, Piotr; Ficner, Ralf
    Biomolecules 2018; 8(3): Art. 81
    RNA modifications have been implicated in diverse and important roles in all kingdoms of life with over 100 of them present on tRNAs. A prominent modification at the wobble base of four tRNAs is the 7-deaza-guanine derivative queuine which substitutes the guanine at position 34. This exchange is catalyzed by members of the enzyme class of tRNA guanine transglycosylases (TGTs). These enzymes incorporate guanine substituents into tRNAAsp, tRNAAsn tRNAHis, and tRNATyr in all kingdoms of life. In contrast to the homodimeric bacterial TGT, the active eukaryotic TGT is a heterodimer in solution, comprised of a catalytic QTRT1 subunit and a noncatalytic QTRT2 subunit. Bacterial TGT enzymes, that incorporate a queuine precursor, have been identified or proposed as virulence factors for infections by pathogens in humans and therefore are valuable targets for drug design. To date no structure of a eukaryotic catalytic subunit is reported, and differences to its bacterial counterpart have to be deducted from sequence analysis and models. Here we report the first crystal structure of a eukaryotic QTRT1 subunit and compare it to known structures of the bacterial TGT and murine QTRT2. Furthermore, we were able to determine the crystal structure of QTRT1 in complex with the queuine substrate.
    Dokument ansehen Zusammenfassung
  • Zeitschriftenartikel

    Comparative Genomics and Description of Putative Virulence Factors of Melissococcus plutonius, the Causative Agent of European Foulbrood Disease in Honey Bees 

    Djukic, Marvin; Erler, Silvio; Leimbach, Andreas; Grossar, Daniela; Charrière, Jean-Daniel; Gauthier, Laurent; Hartken, Denise; Dietrich, Sascha; Nacke, Heiko; Daniel, Rolf; et al.
    Poehlein, Anja
    Genes 2018; 9(8): Art. 419
    In Europe, approximately 84% of cultivated crop species depend on insect pollinators, mainly bees. Apis mellifera (the Western honey bee) is the most important commercial pollinator worldwide. The Gram-positive bacterium Melissococcus plutonius is the causative agent of European foulbrood (EFB), a global honey bee brood disease. In order to detect putative virulence factors, we sequenced and analyzed the genomes of 14 M. plutonius strains, including two reference isolates. The isolates do not show a high diversity in genome size or number of predicted protein-encoding genes, ranging from 2.021 to 2.101 Mbp and 1589 to 1686, respectively. Comparative genomics detected genes that might play a role in EFB pathogenesis and ultimately in the death of the honey bee larvae. These include bacteriocins, bacteria cell surface- and host cell adhesion-associated proteins, an enterococcal polysaccharide antigen, an epsilon toxin, proteolytic enzymes, and capsule-associated proteins. In vivo expression of three putative virulence factors (endo-alpha-N-acetylgalactosaminidase, enhancin and epsilon toxin) was verified using naturally infected larvae. With our strain collection, we show for the first time that genomic differences exist between non-virulent and virulent typical strains, as well as a highly virulent atypical strain, that may contribute to the virulence of M. plutonius. Finally, we also detected a high number of conserved pseudogenes (75 to 156) per genome, which indicates genomic reduction during evolutionary host adaptation.
    Dokument ansehen Zusammenfassung
  • Zeitschriftenartikel

    Dinitrogen Splitting Coupled to Protonation 

    Silantyev, Gleb A.; Förster, Moritz; Schluschaß, Bastian; Abbenseth, Josh; Würtele, Christian; Volkmann, Christian; Holthausen, Max C.; Schneider, Sven
    Angewandte Chemie International Edition 2017; 56(21) p.5872-5876
    Dokument ansehen
  • Zeitschriftenartikel

    A Square-Planar Osmium(II) Complex 

    Abbenseth, Josh; Diefenbach, Martin; Bete, Sarah C.; Würtele, Christian; Volkmann, Christian; Demeshko, Serhiy; Holthausen, Max C.; Schneider, Sven
    Chemical Communications 2017; 53(40) p.5511-5514
    Dokument ansehen
  • Zeitschriftenartikel

    Chemical Non-Innocence of an Aliphatic PNP Pincer Ligand 

    Schneck, Felix; Finger, Markus; Tromp, Moniek; Schneider, Sven
    Chemistry - A European Journal 2016; 23(1) p.33-37
    Dokument ansehen
  • Zeitschriftenartikel

    A Terminal Osmium(IV) Nitride: Ammonia Formation and Ambiphilic Reactivity 

    Schendzielorz, Florian S.; Finger, Markus; Volkmann, Christian; Würtele, Christian; Schneider, Sven
    Angewandte Chemie International Edition 2016; 55(38) p.11417-11420
    Dokument ansehen
  • Zeitschriftenartikel

    Conversion of Dinitrogen into Acetonitrile under Ambient Conditions 

    Klopsch, Isabel; Kinauer, Markus; Finger, Markus; Würtele, Christian; Schneider, Sven
    Angewandte Chemie International Edition 2016; 55(15) p.4786-4789
    Dokument ansehen
  • Zeitschriftenartikel

    Influence of Pore Characteristics on the Fate and Distribution of Newly Added Carbon 

    Quigley, Michelle Y.; Negassa, Wakene C.; Guber, Andrey K.; Rivers, Mark L.; Kravchenko, Alexandra N.
    Frontiers in Environmental Science 2018; 6: Art. 51
    Pores create a transportation network within a soil matrix, which controls the flow of air, water, and movement of microorganisms. The flow of air, water, and movement of microbes, in turn, control soil carbon dynamics. Computed microtomography (μCT) allows for the visualization of pore structure at micron scale, but quantitative information on contribution of pores to the fate and protection of soil carbon, essential for modeling, is still lacking. This study uses the natural difference between carbon isotopes of C3 and C4 plants to determine how the presence of pores of different sizes affects spatial distribution patterns of newly added carbon immediately after plant termination and then after 1-month incubation. We considered two contrasting soil structure scenarios: soil with the structure kept intact and soil for which the structure was destroyed via sieving. For the experiment, soil was collected from 0–15 cm depth at a 20-year continuous maize (Zea mays L., C4 plant) experiment into which cereal rye (Secale cereale L., C3 plant) was planted. Intact soil fragments (5–6mm) were procured after 3 months rye growth in a greenhouse. Pore characteristics of the fragments were determined through μCT imaging. Each fragment was sectioned and total carbon, total nitrogen, d13C, and d15N were measured. The results indicate that, prior to incubation, greater presence of 40–90μm pores was associated with higher levels of C3 carbon, pointing to the positive role of these pores in transport of new C inputs. Nevertheless, after incubation, the association became negative, indicating greater losses of newly added C in such pores. These trends were statistically significant in destroyed-structure soil and numerical in intact-structure soil. In soils of intact-structures, after incubation, higher levels of total carbon were associated with greater abundance of 6.5–15 and 15–40μm pores, indicating a lower carbon loss associated with these pores. The results indicate that, in the studied soil, pores of 40–90μm size range are associated with the fast influx of new C followed by its quick decomposition, while pores <40μmtend to be associated with C protection.
    Dokument ansehen Zusammenfassung
  • Zeitschriftenartikel

    Aboveground Forest Biomass Estimation Combining L- and P-Band SAR Acquisitions 

    Schlund, Michael; Davidson, Malcolm
    Remote Sensing 2018; 10(7): Art. 1151
    While considerable research has focused on using either L-band or P-band SAR (Synthetic Aperture Radar) on their own for forest biomass retrieval, the use of the two bands simultaneously to improve forest biomass retrieval remains less explored. In this paper, we make use of L- and P-band airborne SAR and in situ data measured in the field together with laser scanning data acquired over one hemi-boreal (Remningstorp) and one boreal (Krycklan) forest study area in Sweden. We fit statistical models to different combinations of topographic-corrected SAR backscatter and forest heights estimated from PolInSAR for the biomass estimation, and evaluate retrieval performance in terms of R2 and using 10-fold cross-validation. The study shows that specific combinations of radar observables from L- and P-band lead to biomass predictions that are more accurate in comparison with single-band retrievals. The correlations and accuracies between the combinations of SAR features and aboveground biomass are consistent across the two study areas, whereas the retrieval performance varied for individual bands. P-band-based retrievals were more accurate than L-band for the hemi-boreal Remningstorp site and less accurate than L-band for the boreal Krycklan site. The aboveground biomass levels as well as the ground topography differ between the two sites. The results suggest that P-band is more sensitive to higher biomass and L-band to lower biomass forests. The forest height from PolInSAR improved the results at L-band in the higher biomass substantially, whereas no improvement was observed at P-band in both study areas. These results are relevant in the context of combining information over boreal forests from future low-frequency SAR missions such as the European Space Agency (ESA) BIOMASS mission, which will operate at P-band, and future L-band missions planned by several space agencies.
    Dokument ansehen Zusammenfassung
  • Zeitschriftenartikel

    Establishment of Apomixis in Diploid F2 Hybrids and Inheritance of Apospory From F1 to F2 Hybrids of the Ranunculus auricomus Complex 

    Barke, Birthe H.; Daubert, Mareike; Hörandl, Elvira
    Frontiers in Plant Science 2018; 9: Art. 1111
    Hybridization and polyploidization play important roles in plant evolution but it is still not fully clarified how these evolutionary forces contribute to the establishment of apomicts. Apomixis, the asexual reproduction via seed formation, comprises several essential alterations in development compared to the sexual pathway. Furthermore, most natural apomicts were found to be polyploids and/or hybrids. The Ranunculus auricomus complex comprises diploid sexual and polyploid apomictic species and represents an excellent model system to gain knowledge on origin and evolution of apomixis in natural plant populations. In this study, the second generation of synthetically produced homoploid (2x) and heteroploid (3x) hybrids derived from sexual R. auricomus species was analyzed for aposporous initial cell formation by DIC microscopy. Complete manifestation of apomixis was determined by measuring single mature seeds by flow cytometric seed screen. Microscopic analysis of the female gametophyte formation indicated spontaneous occurrence of aposporous initial cells and several developmental irregularities. The frequency of apospory was found to depend on dosage effects since a significant increase in apospory was observed, when both F1 parents, rather than just one, were aposporous. Other than in the F1 generation, diploid Ranunculus F2 hybrids formed BIII seeds and fully apomictic seeds. The results indicate that hybridization rather than polyploidization seems to be the functional activator of apomictic reproduction in the synthetic Ranunculus hybrids. In turn, at least two hybrid generations are required to establish apomictic seed formation.
    Dokument ansehen Zusammenfassung
  • Zeitschriftenartikel

    Cross-Cultural Comparison between German, French and Dutch Consumer Preferences for Meat Substitutes 

    Weinrich, Ramona
    Sustainability 2018; 10(6): Art. 1819
    Sustainability is becoming an increasingly important consideration for consumers when purchasing food. As meat production has a significant impact on the environment, meat substitutes are becoming more and more popular in Europe. However, consumers who regularly buy meat substitutes are still the exception. Although there are some initial results indicating why this proportion is still low, most research has been concentrated in the Netherlands. This paper aims to compare reasons for consuming or not consuming meat substitutes in three European countries—Germany, the Netherlands and France. As very little is known about the underlying reasons, an explorative approach was chosen. Focus group discussions were carried out in all three countries, six altogether. The results show that all participants can enumerate meat substitutes. The main reason for not consuming meat substitutes is the taste of meat. Further, eating habits seem to be fixed and convenience might also be an impediment to reducing meat consumption in favour of meat substitutes, as is confusion regarding healthy eating.
    Dokument ansehen Zusammenfassung
  • Zeitschriftenartikel

    Modular Neural Mechanisms for Gait Phase Tracking, Prediction, and Selection in Personalizable Knee-Ankle-Foot-Orthoses 

    Braun, Jan-Matthias; Wörgötter, Florentin; Manoonpong, Poramate
    Frontiers in Neurorobotics 2018; 12: Art. 37
    Orthoses for the lower limbs support patients to perform movements that they could not perform on their own. In traditional devices, generic gait models for a limited set of supportedmovements restrict the patientsmobility and device acceptance. To overcome such limitations, we propose a modular neural control approach with user feedback for personalizable Knee-Ankle-Foot-Orthoses (KAFO). The modular controller consists of two main neural components: neural orthosis control for gait phase tracking and neural internal models for gait prediction and selection. A user interface providing online feedback allows the user to shape the control output that adjusts the knee damping parameter of a KAFO. The accuracy and robustness of the control approach were investigated in different conditions including walking on flat ground and descending stairs as well as stair climbing. We show that the controller accurately tracks and predicts the user’s movements and generates corresponding gaits. Furthermore, based on the modular control architecture, the controller can be extended to support various distinguishable gaits depending on differences in sensory feedback.
    Dokument ansehen Zusammenfassung
  • Zeitschriftenartikel

    Measuring Public Concerns? Developing a Moral Concerns Scale Regarding Non-Product Related Process and Production Methods 

    Sonntag, Winnie; Spiller, Achim
    Sustainability 2018; 10(5): Art. 1375
    In recent years, citizens have been more frequently scrutinizing non-product related process and production methods (npr-PPM) of various products, such as food, out of moral considerations. In 2014, theWorld Trade Organization’s (WTO) Dispute Settlement Body reached a landmark decision and accepted an European Union (EU)-wide import ban of seal products under the justification of Art. XX (a) General Agreement on Tariffs and Trade (GATT) due to “public moral concerns”. However, up to now there has been no valid and reliable scale to quantify moral concerns. Therefore, we developed a tool—the Moral Concerns Scale (MCS)—to measure moral concerns of a society about, for example, animal welfare or child labor in a valid and reliable manner for npr-PPM. This scale was developed and tested in two independent studies with German citizens (in 2016 and 2017) using three case studies: hens laying eggs in battery cages, the inhumane killing of seals, and the use of child labor. According to the results of both studies, the reliability and validity of the developed scale can be confirmed.
    Dokument ansehen Zusammenfassung

View more