Free University of Berlin

About: Free University of Berlin is a education organization based out in Berlin, Germany. It is known for research contribution in the topics: Population & Context (language use). The organization has 35195 authors who have published 66525 publications receiving 2094403 citations. The organization is also known as: FU Berlin.

Microplastic in terrestrial ecosystems

Abstract: Research shifts from ecotoxicology to ecosystem effects and Earth system feedbacks Concern about microplastics (plastic particles <5 mm) polluting different environmental compartments is mounting. Research has recently begun to embrace terrestrial systems, having initially focused at least a decade earlier on marine and aquatic ecosystems (1–3). The early research agenda on microplastics in both aquatic and terrestrial systems was mainly ecotoxicological. It included laboratory tests on individual organisms, often well-established test species (4), and also targeted selected soil properties and processes. Such research is necessary to establish baseline mechanisms, which is important because microplastics differ from other pollutants. Many of their effects appear to be mediated by physical parameters, such as particle shape and size, rather than overt chemically mediated toxicity. Moreover, their effects are mostly sublethal or even nominally positive. Although the study of other global change factors has tended to focus at the level of the ecosystem, research on microplastic is only now on the verge of this wider view.

Structure of the Tet repressor-tetracycline complex and regulation of antibiotic resistance

Abstract: The most frequently occurring resistance of Gram-negative bacteria against tetracyclines is triggered by drug recognition of the Tet repressor. This causes dissociation of the repressor-operator DNA complex and enables expression of the resistance protein TetA, which is responsible for active efflux of tetracycline. The 2.5 angstrom resolution crystal structure of the homodimeric Tet repressor complexed with tetracycline-magnesium reveals detailed drug recognition. The orientation of the operator-binding helix-turn-helix motifs of the repressor is inverted in comparison with other DNA binding proteins. The repressor-drug complex is unable to interact with DNA because the separation of the DNA binding motifs is 5 angstroms wider than usually observed.

Photosynthetic O2 Formation Tracked by Time-Resolved X-ray Experiments

Abstract: Plants and cyanobacteria produce atmospheric dioxygen from water, powered by sunlight and catalyzed by a manganese complex in photosystem II. A classic S-cycle model for oxygen evolution involves five states, but only four have been identified. The missing S4 state is particularly important because it is directly involved in dioxygen formation. Now progress comes from an x-ray technique that can monitor redox and structural changes in metal centers in real time with 10-microsecond resolution. We show that in the O2-formation step, an intermediate is formed—the enigmatic S4 state. Its creation is identified with a deprotonation process rather than the expected electron-transfer mechanism. Subsequent electron transfer would give an additional S4′ state, thus extending the fundamental S-state cycle of dioxygen formation.

Single-ion heat engine at maximum power.

Abstract: We propose an experimental scheme to realize a nanoheat engine with a single ion. An Otto cycle may be implemented by confining the ion in a linear Paul trap with tapered geometry and coupling it to engineered laser reservoirs. The quantum efficiency at maximum power is analytically determined in various regimes. Moreover, Monte Carlo simulations of the engine are performed that demonstrate its feasibility and its ability to operate at a maximum efficiency of 30% under realistic conditions.

Incomplete and Inaccurate Vocal Imitation after Knockdown of FoxP2 in Songbird Basal Ganglia Nucleus Area X

Abstract: The gene encoding the forkhead box transcription factor, FOXP2, is essential for developing the full articulatory power of human language. Mutations of FOXP2 cause developmental verbal dyspraxia (DVD), a speech and language disorder that compromises the fluent production of words and the correct use and comprehension of grammar. FOXP2 patients have structural and functional abnormalities in the striatum of the basal ganglia, which also express high levels of FOXP2. Since human speech and learned vocalizations in songbirds bear behavioral and neural parallels, songbirds provide a genuine model for investigating the basic principles of speech and its pathologies. In zebra finch Area X, a basal ganglia structure necessary for song learning, FoxP2 expression increases during the time when song learning occurs. Here, we used lentivirus-mediated RNA interference (RNAi) to reduce FoxP2 levels in Area X during song development. Knockdown of FoxP2 resulted in an incomplete and inaccurate imitation of tutor song. Inaccurate vocal imitation was already evident early during song ontogeny and persisted into adulthood. The acoustic structure and the duration of adult song syllables were abnormally variable, similar to word production in children with DVD. Our findings provide the first example of a functional gene analysis in songbirds and suggest that normal auditory-guided vocal motor learning requires FoxP2.