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Methane (CH 4 ), the most abundant hydrocarbon in the atmosphere, originates largely from biogenic sources 1 linked to an increasing number of organisms occurring in oxic and anoxic environments. Traditionally, biogenic CH 4 has been regarded as the final product of anoxic decomposition of organic matter by methanogenic archaea. However, plants 2 , 3 , fungi 4 , algae 5 and cyanobacteria 6 can produce CH 4 in the presence of oxygen. Although methanogens are known to produce CH 4 enzymatically during anaerobic energy metabolism 7 , the requirements and pathways for CH 4 production by non-methanogenic cells are poorly understood. Here, we demonstrate that CH 4 formation by Bacillus subtilis and Escherichia coli is triggered by free iron and reactive oxygen species (ROS), which are generated by metabolic activity and enhanced by oxidative stress. ROS-induced methyl radicals, which are derived from organic compounds containing sulfur- or nitrogen-bonded methyl groups, are key intermediates that ultimately lead to CH 4 production. We further show CH 4 production by many other model organisms from the Bacteria, Archaea and Eukarya domains, including in several human cell lines. All these organisms respond to inducers of oxidative stress by enhanced CH 4 formation. Our results imply that all living cells probably possess a common mechanism of CH 4 formation that is based on interactions among ROS, iron and methyl donors, opening new perspectives for understanding biochemical CH 4 formation and cycling. Methane formation by a ROS-mediated process is linked to metabolic activity and is identified as a conserved feature across living systems.

Collagen is a force-bearing, hierarchical structural protein important to all connective tissue. In tendon collagen, high load even below macroscopic failure level creates mechanoradicals by homolytic bond scission, similar to polymers. The location and type of initial rupture sites critically decide on both the mechanical and chemical impact of these micro-ruptures on the tissue, but are yet to be explored. We here use scale-bridging simulations supported by gel electrophoresis and mass spectrometry to determine breakage points in collagen. We find collagen crosslinks, as opposed to the backbone, to harbor the weakest bonds, with one particular bond in trivalent crosslinks as the most dominant rupture site. We identify this bond as sacrificial, rupturing prior to other bonds while maintaining the material’s integrity. Also, collagen’s weak bonds funnel ruptures such that the potentially harmful mechanoradicals are readily stabilized. Our results suggest this unique failure mode of collagen to be tailored towards combatting an early onset of macroscopic failure and material ageing. Collagen is an important structural protein in connective tissue, but the effect of location and type of micro-ruptures in the structure on the overall tissue is not well understood. Here, the authors use scale-bridging simulations to determine the breakage points in collagen, and how the failure mode helps to prevent material ageing

As established nearly a century ago, mechanoradicals originate from homolytic bond scission in polymers. The existence, nature and biological relevance of mechanoradicals in proteins, instead, are unknown. We here show that mechanical stress on collagen produces radicals and subsequently reactive oxygen species, essential biological signaling molecules. Electron-paramagnetic resonance (EPR) spectroscopy of stretched rat tail tendon, atomistic molecular dynamics simulations and quantum-chemical calculations show that the radicals form by bond scission in the direct vicinity of crosslinks in collagen. Radicals migrate to adjacent clusters of aromatic residues and stabilize on oxidized tyrosyl radicals, giving rise to a distinct EPR spectrum consistent with a stable dihydroxyphenylalanine (DOPA) radical. The protein mechanoradicals, as a yet undiscovered source of oxidative stress, finally convert into hydrogen peroxide. Our study suggests collagen I to have evolved as a radical sponge against mechano-oxidative damage and proposes a mechanism for exercise-induced oxidative stress and redox-mediated pathophysiological processes. The existence, nature and biological relevance of mechanoradicals in proteins are unknown. Here authors show that mechanical stress on collagen produces radicals and subsequently reactive oxygen species and suggest that collagen I evolved as a radical sponge against mechano-oxidative damage.

Responding to the UN programme “The Economics of Ecosystems and Biodiversity” (TEEB), TEEB-DE (2012–2018) was a science–policy interface (SPI) set up in Germany with the objective of mobilising scientific expertise for a better consideration of biodiversity and ecosystem services in political and corporate decision-making. The aim of this paper is to contribute to an assessment of TEEB-DE by analysing its objectives, structure, processes and outputs. The analysis is guided by a theoretical framework that takes credibility, relevance and legitimacy (CRELE) as normative criteria for examining SPIs. Methodologically, the paper relies on a fine-grained analysis of published documents and interviews with key figures of TEEB-DE. The results allow for a preliminary assessment of TEEB-DE in regard to CRELE and illuminate how its conceptual foundation—namely the ecosystem services concept—was discussed in the public realm. We also consider a number of trade-offs which the coordinators of TEEB-DE had to negotiate. In conclusion, we identify some proposals for designing future SPIs in the domain of biodiversity and nature conservation in Germany such as paying greater attention to policy windows, broadening the thematic scope beyond economics and providing better opportunities for debate and contestation.

In Deutschland befindet sich der Naturschutz traditionell in einem Zwiespalt: Auf der einen Seite üben Naturschützer(innen) Kritik an wirtschaftlichem und technologischem Fortschritt sowie steigendem Konsum. Andererseits ist die Naturschutzszene mit einem wenig nachhaltigen Lebens- und Wirtschaftsmodell verzahnt. Vor diesem Hintergrund diskutieren wir einige Beobachtungen und Thesen zu den Beziehungen zwischen dem Naturschutz in Deutschland und den Forderungen nach weitreichenden sozial-ökologischen Transformationen.

Nach Meinung von Hans Fehr, Lehrstuhl für Finanzwissenschaft, Universität Würzburg, belastet der aktuelle Gesetzentwurf zur Reform der Rentenversicherung pauschal die Beitragszahler, konterkariert die eingeleitete Anhebung des Rentenzugangsalters und hilft nur wenig gegen die künftig steigende Altersarmut Martin Werding, Universität Bochum, sieht in den Reformpläne der Großen Koalition eine Vernachlässigung der Verbesserung der längerfristigen Perspektiven für die Rentenfinanzierung. Für Axel Börsch-Supan, Max-Planck-Institut für Sozialrecht und Sozialpolitik, München, sind die Beschlüsse der neuen Großen Koalition »kurzsichtig und einseitig: Die Wohltaten kommen der älteren Generation zugute, während es die zukünftigen Beitragszahler finanzieren müssen, die ohnehin durch den demographischen Wandel gebeutelt werden.« Alfred Boss, Institut für Weltwirtschaft Kiel, bezeichnet die Rentenreform als einen Schritt in die falsche Richtung, die Verlieren seien die nicht begünstigten Rentner und die Beitragszahler. Jörg Asmussen, Bundesministerium für Arbeit und Soziales, stellt die Überlegungen der Regierungskoalition vor. Er unterstreicht, dass an einer demographiefesten Rentenversicherung festgehalten wird, aber mit dem Rentenpaket gerechtere Ansprüche geschaffen werden. Nach Ansicht von Enzo Weber, IAB, Nürnberg, und Universität Regensburg, passen nicht alle Teile des Rentenpakets in eine wirksame Gesamtstrategie. In der Summe der finanziellen Belastungen werden Chancen auf eine Stärkung von Erwerbsanreizen durch eine Beitragssenkung vertan. Markus Kurth, MdB, Bündnis 90/Die Grünen, sieht durch die Rentenpläne Spielräume für die sozialpolitisch wichtigen Verbesserungen auf Jahre zugestellt.

Collagen is a force-bearing, hierarchical structural protein important to all connective tissue. In tendon collagen, high load even below macroscopic failure level creates mechanoradicals by homolytic bond scission, similar to polymers. The location and type of initial rupture sites critically decide on both the mechanical and chemical impact of these micro-ruptures on the tissue, but are yet to be explored. We here use scale-bridging simulations supported by gel electrophoresis and mass spectrometry to determine breakage points in collagen. We find collagen crosslinks, as opposed to the backbone, to harbor the weakest bonds, with one particular bond in trivalent crosslinks as the most dominant rupture site. We identify this bond as sacrificial, rupturing prior to other bonds while maintaining the material's integrity. Also, collagen's weak bonds funnel ruptures such that the potentially harmful mechanoradicals are readily stabilized. Our results suggest this unique failure mode of collagen to be tailored towards combatting an early onset of macroscopic failure and material ageing. Competing Interest Statement The authors have declared no competing interest. Footnotes * Update of Acknowledgements.

Here we uncover collagen, the main structural protein of all connective tissues, as a redox-active material. We identify dihydroxyphenylalanine (DOPA) residues, post-translational oxidation products of tyrosine residues, to be common in collagen derived from different connective tissues. We observe that these DOPA residues endow collagen with substantial radical scavenging capacity. When reducing radicals, DOPA residues work as redox relay: they convert to the quinone and generate hydrogen peroxide. In this dual function, DOPA outcompetes its amino acid precursors and ascorbic acid. Our results establish DOPA residues as redox-active side chains of collagens, probably protecting connective tissues against radicals formed under mechanical stress and/or inflammation.Competing Interest StatementThe authors have declared no competing interest.