Doping dependence of the chemical potential and surface electronic structure in YBa2Cu3O6+x and La2-xSrxCuO4 using hard x-ray photoemission spectroscopy

The electronic structure of YBa2Cu3O6+x and La2-xSrxCuO4 for various values of x has been investigated using hard x-ray photoemission spectroscopy. The experimental results establish that the cleaving of YBa2Cu3O6+x compounds occurs predominantly in the BaCuO3 complex leading to charged surfaces at higher x and to uncharged surfaces at lower x values. The bulk component of the core level spectra exhibits a shift in binding energy as a function of x, from which a shift of the chemical potential as a function of hole concentration in the CuO2 layers could be derived. The doping dependence of the chemical potential across the transition from a Mott-Hubbard insulator to a Fermi-liquid-like metal is very different in these two series of compounds. In agreement with previous studies in the literature the chemical potential shift in La2-xSrxCuO4 is close to zero for small hole concentrations. In YBa2Cu3O6+x, similar to all other doped cuprates studied so far, a strong shift of the chemical potential at low hole doping is detected. However, the results for the inverse charge susceptibility at small x shows a large variation between different doped cuprates. The results are discussed in view of various theoretical models. None of these models turns out to be satisfactory.Comment: 18 pages, 15 figure

Phosphorylation of serine 225 in hepatitis C virus NS5A regulates protein-protein interactions.

Hepatitis C virus (HCV) non-structural protein 5A (NS5A) is a phosphoprotein that plays key, yet poorly defined, roles in both virus genome replication and virion assembly/release. It has been proposed that differential phosphorylation could act as a switch to regulate the various functions of NS5A, however the mechanistic details of the role of this post-translational modification in the virus life cycle remains obscure. We previously reported (Ross-Thriepland et al, 2015) a role for phosphorylation at serine 225 (S225) of NS5A in the regulation of JFH-1 (genotype 2a) genome replication. A phosphoablatant (S225A) mutation resulted in a 10-fold reduction in replication and a perinuclear restricted distribution of NS5A, whereas the corresponding phosphomimetic mutation (S225D) had no phenotype. To determine the molecular mechanisms underpinning this phenotype we conducted a label-free proteomics approach to identify cellular NS5A interaction partners. This analysis 30 revealed that the S225A mutation disrupted the interactions of NS5A with a number of cellular proteins, in particular the nucleosome assembly protein 1-like protein 1 (NAP1L1), bridging integrator 1 (Bin1, also known as Amphiphysin II) and vesicle associated membrane protein-associated protein A (VAP-A). These interactions were validated by immunoprecipitation/western blotting, immunofluorescence and proximity ligation assay. Importantly, siRNA-mediated knockdown of NAP1L1, Bin1 or VAP-A impaired viral genome replication and recapitulated the perinuclear redistribution of NS5A seen in the S225A mutant. These results demonstrate that S225 phosphorylation regulates the interactions of NS5A with a defined subset of cellular proteins. Furthermore, these interactions regulate both HCV genome replication and the subcellular localisation of replication complexes. IMPORTANCE Hepatitis C virus is an important human pathogen. The viral nonstructural 5A protein (NS5A) is the target for new antiviral drugs. NS5A has multiple functions during the virus life cycle, but the biochemical details of these roles remain obscure. NS5A is known to be phosphorylated by cellular protein kinases, and in this study, we set out to determine whether this modification is required for the binding of NS5A to other cellular proteins. We identified 3 such proteins and show that they interacted only with NS5A that was phosphorylated on a specific residue. Furthermore, these proteins were required for efficient virus replication and the ability of NS5A to spread throughout the cytoplasm of the cell. Our results help to define the function of NS5A and may contribute to an understanding of the mode of action of the highly potent antiviral drugs that are targeted to NS5A

The inner junction protein CFAP20 functions in motile and non-motile cilia and is critical for vision

Motile and non-motile cilia are associated with mutually-exclusive genetic disorders. Motile cilia propel sperm or extracellular fluids, and their dysfunction causes primary ciliary dyskinesia. Non-motile cilia serve as sensory/signalling antennae on most cell types, and their disruption causes single-organ ciliopathies such as retinopathies or multi-system syndromes. CFAP20 is a ciliopathy candidate known to modulate motile cilia in unicellular eukaryotes. We demonstrate that in zebrafish, cfap20 is required for motile cilia function, and in C. elegans, CFAP-20 maintains the structural integrity of non-motile cilia inner junctions, influencing sensory-dependent signalling and development. Human patients and zebrafish with CFAP20 mutations both exhibit retinal dystrophy. Hence, CFAP20 functions within a structural/functional hub centered on the inner junction that is shared between motile and non-motile cilia, and is distinct from other ciliopathy-associated domains or macromolecular complexes. Our findings suggest an uncharacterised pathomechanism for retinal dystrophy, and potentially for motile and non-motile ciliopathies in general

Kristallwachstum und Transport im Normalzustand von elektron-dotierten Hochtemperatursupraleitern

The present thesis deals with the improvement of the growth and annealing parameters as well as the influence of oxygen impurities on the structural and electronic properties of Re2-xCexCuO4 (Re = La, Pr, Nd, Sm) single crystals. For transport measurements a sample set of high quality single crystals of Nd2-xCexCuO4 was available, which covers the major part of the phase diagram on the electron doped side of the cuprate high temperature superconductors. The resulting unusual transport data of the optimally doped and overdoped crystals can be explained within conventional Boltzmann transport theory when applying a two-band model with anisotropic scattering rates.In der vorliegenden Arbeit werden verbesserte Wachstumsbedingungen und Temperparameter sowie der Einfluss von Sauerstoffstörstellen auf die strukturellen und elektronischen Eigenschaften von Re2-xCexCuO4 (Re = La, Pr, Nd, Sm) Einkristallen diskutiert. Für die Transportmessungen stand ein hochreiner Nd2-xCexCuO4 Probensatz zur Verfügung, der einen großen Bereich des elektron-dotierten Phasendiagramms der Kuprat Hochtemperatursupraleiter abdeckt. Die sich ergebenden ungewöhnlichen Transportdaten im optimalen und überdotierten Bereich können im Rahmen konventioneller Boltzmann-Transporttheorie erklärt werden, indem ein Zwei-Band Modell mit anisotropen Streuraten angewandt wird

Alteration of the nuclear pore complex in Ca(2+)-mediated cell death

Cell death requires coordinated intracellular signalling before disassembly of cell architecture by degradative enzymes. Although the death signalling cascades that involve the mitochondria, the ER and the plasma membrane have been extensively characterized, only a handful of studies have examined the functional and structural alterations of the nuclear pore complex (NPC) during neuronal death. Here, we show that during excitotoxic neuronal degeneration calpains redistributed across the nuclear envelope and mediated the degradation of NPC components causing altered permeability of the nuclear membrane. In primary dissociated neurons, simultaneous recording of cytosolic [Ca(2+)] and localization of fluorescent proteins showed that the onset of Ca(2+) overload signalled a progressive increase in the diffusion of small reporter molecules across the nuclear envelope. Later, calpain-mediated changes in nuclear pore permeability allowed accumulation of large proteins in the nucleus. Further, in a model of excitotoxic neuronal degeneration in Caenorhabditis elegans, we found similar nuclear changes and redistribution of fluorescent probes across the nuclear membrane in dying neurons. Our findings strongly suggest that increased leakiness of the nuclear barrier affects nucleocytoplasmic transport, alters the localization of proteins across the nuclear envelope and it is likely to be involved in Ca(2+)-dependent cell death, including ischemic neuronal demise

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This paper describes a plugin architecture for medical image processing, which enables a "sandbox " approach for researchers and developers to extend current medical image processing techniques. By tracking these new or modified procedures, the human computer interface can be adjusted to accommodate such changes. This, in turn, allows clinicians to immediately utilize new analysis methods in a productive, yet familiar, diagnostic environment

Scanning angle interference microscopy reveals cell dynamics at the nanoscale

Emerging questions in cell biology necessitate nanometer-scale imaging in live cells. Here we present scanning angle interference microscopy, capable of localizing fluorescent objects with nanometer-scale precision along the optical axis in motile cellular structures. We use this approach to resolve nano-topographical features of the cell membrane and cytoskeleton, as well as the temporal evolution, three-dimensional architecture, and nano-scale dynamics of focal adhesion complexes

Integrin-Linked Kinase Controls Microtubule Dynamics Required for Plasma Membrane Targeting of Caveolae

Caveolae are specialized compartments of the plasma membrane that are involved in signaling, endocytosis, and cholesterol transport. Their formation requires the transport of caveolin-1 to the plasma membrane, but the molecular mechanisms regulating the transport are largely unknown. Here, we identify a critical role for adhesion-mediated signaling through β1 integrins and integrin-linked kinase (ILK) in caveolae formation. Mice lacking β1 integrins or ILK in keratinocytes have dramatically reduced numbers of plasma membrane caveolae in vivo, which is due to impaired transport of caveolin-1-containing vesicles along microtubules (MT) to the plasma membrane. Mechanistically, ILK promotes the recruitment of the F-actin binding protein IQGAP1 to the cell cortex, which, in turn, cooperates with its effector mDia1 to locally stabilize MTs and to allow stable insertion of caveolae into the plasma membrane. Our results assign an important role to the integrin/ILK complex for caveolar trafficking to the cell surface