Research Center Caesar

Bonn, Germany

Research Center Caesar

Bonn, Germany
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Schroder S.,Gladstone | Schroder S.,University of California at San Francisco | Herker E.,Gladstone | Herker E.,Heinrich Pette Institute | And 23 more authors.
Molecular Cell | Year: 2013

Lysine acetylation regulates transcription by targeting histones and nonhistone proteins. Here we report that the central regulator of transcription, RNA polymerase II, is subject to acetylation in mammalian cells. Acetylation occurs at eight lysines within the C-terminal domain (CTD) of the largest polymerase subunit and is mediated by p300/KAT3B. CTD acetylation is specifically enriched downstream of the transcription start sites of polymerase-occupied genes genome-wide, indicating a role in early stages of transcription initiation or elongation. Mutation oflysines or p300 inhibitor treatment causes the loss of epidermal growth-factor-induced expression of c-Fos and Egr2, immediate-early genes with promoter-proximally paused polymerases, but does not affect expression or polymerase occupancy at housekeeping genes. Our studies identify acetylation as a new modification of the mammalian RNA polymerase II required for the induction of growth factor response genes. © 2013 Elsevier Inc.

Schonichen A.,Max Planck Institute of Molecular Physiology | Schonichen A.,University of California at San Francisco | Mannherz H.G.,Max Planck Institute of Molecular Physiology | Mannherz H.G.,Ruhr University Bochum | And 14 more authors.
Journal of Cell Science | Year: 2013

Formins are actin polymerization factors that are known to nucleate and elongate actin filaments at the barbed end. In the present study we show that human FHOD1 lacks actinnucleation and elongation capacity, but acts as an actin bundling factor with capping activity toward the filament barbed end. Constitutively active FHOD1 associates with actin filaments in filopodia and lamellipodia at the leading edge, where it moves with the actinretrograde flow. At the base of lamellipodia, FHOD1 is enriched in nascent, bundled actinarcs as well as in more mature stress fibers. This function requires actin-binding domains located N-terminally to the canonical FH1-FH2 element. The bundling phenotype is maintained in the presence of tropomyosin, confirmed by electron microscopy showing assembly of5 to 10 actin filaments into parallel, closely spaced filament bundles. Taken together, our data suggest a model in which FHOD1 stabilizes actin filaments by protecting barbed ends from depolymerization with its dimeric FH2 domain, whereas the region N-terminal to the FH1 domain mediates F-actin bundling by simultaneously binding to the sides of adjacentF-actin filaments. © 2013. Published by The Company of Biologists Ltd.

von Cube F.,University of Bonn | von Cube F.,Research Center Caesar | Niegemann J.,Karlsruhe Institute of Technology | Matyssek C.,Max Planck Institute of Microstructure Physics | And 4 more authors.
Optical Materials Express | Year: 2011

Scanning transmission electron microscopy in combination with electron energy-loss spectroscopy is a powerful tool for the spatial and spectral characterization of the plasmonic modes of lithographically defined photonic meta-atoms. As an example, we present a size dependence study of the resonance energies of the plasmonic modes of a series of isolated split-ring resonators. Furthermore, we show that the comparison of the plasmonic maps of a split-ring resonator and the corresponding complementary split-ring resonator allows a direct visualization of Babinet's principle. Our experiments are in good agreement with numerical calculations based on a discontinuous Galerkin time-domain approach. © 2011 Optical Society of America.

Palm M.,Max Planck Institute Für Eisenforschung | Engberding N.,Max Planck Institute Für Eisenforschung | Stein F.,Max Planck Institute Für Eisenforschung | Kelm K.,German Aerospace Center | Irsen S.,Research Center Caesar
Acta Materialia | Year: 2012

The formation and stability of Al-rich Ti-Al phases is reviewed and the kinetics of the phase transformations and evolution of lamellar TiAl + r-TiAl 2 microstructures is discussed. For this a couple of Ti-60 at.% Al alloys were processed by different techniques to generate different initial microstructures. The kinetics were studied by annealing the differently processed alloys for 1, 10, 100 and 1000 h at temperatures between 800 and 1000°C and then analysing the quenched microstructures by optical, scanning electron, and transmission electron microscopy. In addition, in situ heating and cooling experiments using differential thermal analysis and transmission electron microscopy were performed to verify the results obtained for the quenched samples. The results conclusively show why the metastable phases h-TiAl 2 and Ti 3Al 5 form. The stability and transformation of the metastable phases have been determined in dependence on time and temperature and the kinetics of the two different mechanisms by which the stable phase r-TiAl 2 forms have been established. The effects of differing initial microstructures on the evolution of the microstructure with time and temperature are discussed. © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Schulze N.,University of Duisburg - Essen | Graessl M.,University of Duisburg - Essen | Soares A.B.,Bernhard Nocht Institute for Tropical Medicine | Geyer M.,Research Center Caesar | And 2 more authors.
Journal of Cell Science | Year: 2014

The formin FHOD1 (formin homology 2 domain containing protein 1) can act as a capping and bundling protein in vitro. In cells, active FHOD1 stimulates the formation of ventral stress fibers. However, the cellular mechanisms by which this phenotype is produced and the physiological relevance of FHOD1 function are not currently understood. Here, we first show that FHOD1 controls the formation of two distinct stress fiber precursors differentially. On the one hand, it inhibits dorsal fiber growth, which requires the polymerization of parallel bundles of long actin filaments. On the other hand, it stimulates transverse arcs that are formed by the fusion of short antiparallel actin filaments. This combined action is crucial for the maturation of stress fibers and their spatio-temporal organization, and a lack of FHOD1 function perturbs dynamic cell behavior during cell migration. Furthermore, we show that the GTPase-binding and formin homology 3 domains (GBD and FH3) are responsible for stress fiber association and colocalization with myosin. Surprisingly, a version of FHOD1 that lacks these domains nevertheless retains its full capacity to stimulate arc and ventral stress fiber formation. Based on our findings, we propose a mechanism in which FHOD1 promotes the formation of short actin filaments and transiently associates with transverse arcs, thus providing tight temporal and spatial control of the formation and turnover of transverse arcs into mature ventral stress fibers during dynamic cell behavior. © 2014. Published by The Company of Biologists Ltd.

Detsch R.,BioCer Entwicklungs GmbH | Schaefer S.,University of Bayreuth | Deisinger U.,University of Bayreuth | Ziegler G.,BioCer Entwicklungs GmbH | And 4 more authors.
Journal of Biomaterials Applications | Year: 2011

Various biomaterials have been developed for the use as bone substitutes for bone defects. To optimize their integration and functionality, they should be adapted to the individual defect. Rapid prototyping is a manufacturing method to tailor materials to the 3D geometry of the defect. Especially 3D printing allows the manufacture of implants, the shape of which can be designed to fit the bone defect using anatomical information obtained from the patient. 3D printing of calcium phosphates, which are well established as bone substitutes, involves a sintering step after gluing the granules together by a binder liquid. In this study, we analyzed if and how these 3D printed calcium phosphate surfaces can be resorbed by osteoclast-like cells. On 3D printed scaffold surfaces consisting of pure HA and Β-TCP as well as a biphasic mixture of HA and TCP the osteoclastic cell differentiation was studied. In this regard, cell proliferation, differentiation, and activation were analyzed with the monocytic cell line RAW 264.7. The results show that osteoclast-like cells were able to resorb calcium phosphate surfaces consisting of granules. Furthermore, biphasic calcium phosphate ceramics exhibit, because of their osteoclastic activation ability, the most promising surface properties to serve as 3D printed bone substitute scaffolds. © 2010 The Author(s).

PubMed | Free University of Berlin, Humboldt University of Berlin and Research Center Caesar
Type: | Journal: Methods in molecular biology (Clifton, N.J.) | Year: 2016

As a transformative approach in neuroscience and cell biology, optogenetics grants control over manifold cellular events with unprecedented spatiotemporal definition, reversibility, and noninvasiveness. Sensory photoreceptors serve as genetically encoded, light-regulated actuators and hence embody the cornerstone of optogenetics. To expand the scope of optogenetics, ever more naturally occurring photoreceptors are being characterized, and synthetic photoreceptors with customized, light-regulated function are being engineered. Perturbational control over intracellular cyclic-nucleotide-monophosphate (cNMP) levels is achieved via sensory photoreceptors that catalyze the making and breaking of these second messengers in response to light. To facilitate discovery, engineering and quantitative characterization of such light-regulated cNMP actuators, we have developed an efficient fluorometric assay. Both the formation and the hydrolysis of cNMPs are accompanied by proton release which can be quantified with the fluorescent pH indicator 2,7-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein (BCECF). This assay equally applies to nucleotide cyclases, e.g., blue-light-activated bPAC, and to cNMP phosphodiesterases, e.g., red-light-activated LAPD. Key benefits include potential for parallelization and automation, as well as suitability for both purified enzymes and crude cell lysates. The BCECF assay hence stands to accelerate discovery and characterization of light-regulated actuators of cNMP metabolism.

Wallace D.J.,Research Center Caesar | Fitzpatrick D.,Max Planck Florida Institute for Neuroscience | Kerr J.N.D.,Research Center Caesar
Current Biology | Year: 2016

A recent study shows conclusively that the koniocellular layers of the marmoset dorsal lateral geniculate nucleus have binocularly responsive neurons. This adds a new twist to the traditional view about binocular processing in the primate visual system and raises questions about the role of dorsal lateral geniculate nucleus in early binocular processing. © 2016 Elsevier Ltd.

Wiedemann U.,University of Bonn | Karapetyan K.,University of Bonn | Dan C.,University of Bonn | Pritzkau D.,University of Bonn | And 3 more authors.
Optics Express | Year: 2010

Applications of subwavelength-diameter optical fibres in nonlinear optics require precise knowledge of the submicrometre fibre waist diameter. We demonstrate a new technique for optical measurement of the diameter based on second-and third-harmonic generation with an accuracy of better than 2%. To generate the harmonic light, inter-modal phase matching must be achieved. We find that the phase-matching condition allows us to unambiguously deduce the fibre diameter from the wavelength of the harmonic light. High-resolution scanning electron microscope imaging is used to verify the results. © 2010 Optical Society of America.

PubMed | Max Planck Florida Institute for Neuroscience and research center caesar
Type: Journal Article | Journal: Current biology : CB | Year: 2016

A recent study shows conclusively that the koniocellular layers of the marmoset dorsal lateral geniculate nucleus have binocularly responsive neurons. This adds a new twist to the traditional view about binocular processing in the primate visual system and raises questions about the role of dorsal lateral geniculate nucleus in early binocular processing.

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