Concealed d-wave pairs in the s± condensate of iron-based superconductors.

A central question in iron-based superconductivity is the mechanism by which the paired electrons minimize their strong mutual Coulomb repulsion. In most unconventional superconductors, Coulomb repulsion is minimized through the formation of higher angular momentum Cooper pairs, with Fermi surface nodes in the pair wavefunction. The apparent absence of such nodes in the iron-based superconductors has led to a belief they form an s-wave ([Formula: see text]) singlet state, which changes sign between the electron and hole pockets.

Tracking Se Assimilation and Speciation through the Rice Plant - Nutrient Competition, Toxicity and Distribution.

Up to 1 billion people are affected by low intakes of the essential nutrient selenium (Se) due to low concentrations in crops. Biofortification of this micronutrient in plants is an attractive way of increasing dietary Se levels. We investigated a promising method of Se biofortification of rice seedlings, as rice is the primary staple for 3 billion people, but naturally contains low Se concentrations.

Scalable Fabrication of Integrated Nanophotonic Circuits on Arrays of Thin Single Crystal Diamond Membrane Windows.

Diamond has emerged as a promising platform for nanophotonic, optical, and quantum technologies. High-quality, single crystalline substrates of acceptable size are a prerequisite to meet the demanding requirements on low-level impurities and low absorption loss when targeting large photonic circuits. Here, we describe a scalable fabrication method for single crystal diamond membrane windows that achieves three major goals with one fabrication method: providing high quality diamond, as confirmed by Raman spectroscopy; achieving homogeneously thin membranes, enabled by ion implantation; and providing compatibility with established planar fabrication via lithography and vertical etching.

Leukocyte responses to immobilized patterns of CXCL8.

The attachment of neutrophils to the endothelial surface and their migration towards the site of inflammation following chemokine gradients play an essential role in the innate immune response. Chemokines adhere to glycosaminoglycans on the endothelial surface to be detected by leukocytes and trigger their movement along surface- bound gradients in a process called haptotaxis. In assays to systematically study the response of leukocytes to surface-bound compounds both the spatial arrangement of the compound as well as the mode of immobilization need to be controlled.

Cadherin-11 localizes to focal adhesions and promotes cell-substrate adhesion.

Cadherin receptors have a well-established role in cell-cell adhesion, cell polarization and differentiation. However, some cadherins also promote cell and tissue movement during embryonic development and tumour progression. In particular, cadherin-11 is upregulated during tumour and inflammatory cell invasion, but the mechanisms underlying cadherin-11 stimulated cell migration are still incompletely understood.

Chemical bath deposition of textured and compact zinc oxide thin films on vinyl-terminated polystyrene brushes.

In this study we investigated the influence of an organic polystyrene brush on the deposition of ZnO thin films under moderate conditions. On a non-modified SiO x surface, island growth is observed, whereas the polymer brush induces homogeneous film growth. A chemical modification of the polystyrene brushes during the mineralization process occurs, which enables stronger interaction between the then polar template and polar ZnO crystallites in solution.

Isolation of a wide range of minerals from a thermally treated plant: Equisetum arvense, a Mare's tale.

Silica is the second most abundant biomineral being exceeded in nature only by biogenic CaCO3. Many land plants (such as rice, cereals, cucumber, etc.) deposit silica in significant amounts to reinforce their tissues and as a systematic response to pathogen attack.

Practical limitations of superresolution imaging due to conventional sample preparation revealed by a direct comparison of CLSM, SIM and dSTORM.

We evaluate the suitability of conventional sample preparation and labelling methods for two superresolution techniques, structured illumination microscopy and direct stochastic optical reconstruction microscopy, by a comparison to established confocal laser scanning microscopy. We show that SIM is compatible with standard fixation procedures and immunofluorescence labelling protocols and improves resolution by a factor of two compared to confocal laser scanning microscopy. With direct stochastic optical reconstruction microscopy, fluorophores can theoretically be localized with much higher precision.

Template-controlled mineralization: Determining film granularity and structure by surface functionality patterns.

We present a promising first example towards controlling the properties of a self-assembling mineral film by means of the functionality and polarity of a substrate template. In the presented case, a zinc oxide film is deposited by chemical bath deposition on a nearly topography-free template structure composed of a pattern of two self-assembled monolayers with different chemical functionality. We demonstrate the template-modulated morphological properties of the growing film, as the surface functionality dictates the granularity of the growing film.

Metal nanoclusters: Protein corona formation and implications for biological applications.

Metal nanoclusters (NCs) are a new type of nanoprobe with great potential in various biological applications. For biocompatible and efficient utilization of NCs, a thorough understanding of their interactions with biological systems is highly important. Herein, we focus on recent studies addressing interactions between metal NCs and proteins as well as implications for their further biological application.

Studying early stages of fibronectin fibrillogenesis in living cells by atomic force microscopy.

Fibronectin (FN) is an extracellular matrix protein that can be assembled by cells into large fibrillar networks, but the dynamics of FN remodeling and the transition through intermediate fibrillar stages are incompletely understood. Here we used a combination of fluorescence microscopy and time-lapse atomic force microscopy (AFM) to visualize initial stages of FN fibrillogenesis in living fibroblasts at high resolution. Initial FN nanofibrils form within <5 min of cell-matrix contact and subsequently extend at a rate of 0.

A self-reporting tetrazole-based linker for the biofunctionalization of gold nanorods.

A photochemical approach based on nitrile imine-mediated tetrazole-ene cycloaddition is introduced to functionalize gold nanorods with biomolecules. For this purpose, a bifunctional, photoreactive linker containing thioctic acid as the Au anchoring group and a tetrazole moiety for the light-induced reaction with maleimide-capped DNA was prepared. The tetrazole-based reaction on the nanoparticles' surface results in a fluorescent pyrazoline product allowing for the spectroscopic monitoring of the reaction.

Cell type-specific adaptation of cellular and nuclear volume in micro-engineered 3D environments.

Bio-functionalized three-dimensional (3D) structures fabricated by direct laser writing (DLW) are structurally and mechanically well-defined and ideal for systematically investigating the influence of three-dimensionality and substrate stiffness on cell behavior. Here, we show that different fibroblast-like and epithelial cell lines maintain normal proliferation rates and form functional cell-matrix contacts in DLW-fabricated 3D scaffolds of different mechanics and geometry. Furthermore, the molecular composition of cell-matrix contacts forming in these 3D micro-environments and under conventional 2D culture conditions is identical, based on the analysis of several marker proteins (paxillin, phospho-paxillin, phospho-focal adhesion kinase, vinculin, β1-integrin).

Genetic evidence for a microtubule-capture mechanism during polarised growth of Aspergillus nidulans.

The cellular switch from symmetry to polarity in eukaryotes depends on the microtubule (MT) and actin cytoskeletons. In fungi such as Schizosaccharomyces pombe or Aspergillus nidulans, the MT cytoskeleton determines the sites of actin polymerization through cortical cell-end marker proteins. Here we describe A.

New QM/MM implementation of the DFTB3 method in the gromacs package.

The approximate density-functional tight-binding theory method DFTB3 has been implemented in the quantum mechanics/molecular mechanics (QM/MM) framework of the Gromacs molecular simulation package. We show that the efficient smooth particle-mesh Ewald implementation of Gromacs extends to the calculation of QM/MM electrostatic interactions. Further, we make use of the various free-energy functionalities provided by Gromacs and the PLUMED plugin.

Polymer blend lithography for metal films: large-area patterning with over 1 billion holes/inch(2).

Polymer blend lithography (PBL) is a spin-coating-based technique that makes use of the purely lateral phase separation between two immiscible polymers to fabricate large area nanoscale patterns. In our earlier work (Huang et al. 2012), PBL was demonstrated for the fabrication of patterned self-assembled monolayers.

Geometric quantum noise of spin.

The presence of geometric phases is known to affect the dynamics of the systems involved. Here, we consider a quantum degree of freedom, moving in a dissipative environment, whose dynamics is described by a Langevin equation with quantum noise. We show that geometric phases enter the stochastic noise terms.

Low affinity binding of plasma proteins to lipid-coated quantum dots as observed by in situ fluorescence correlation spectroscopy.

Protein binding to lipid-coated nanoparticles has been pursued quantitatively by using fluorescence correlation spectroscopy. The binding of three important plasma proteins to lipid-enwrapped quantum dots (QDs) shows very low affinity, with an apparent dissociation coefficient in the range of several hundred micromolar. Thus, the tendency to adsorb is orders of magnitude weaker than for QDs coated with dihydrolipoic acid.

High-resolution X-ray absorption spectroscopy of iron carbonyl complexes.

We apply high-energy-resolution fluorescence-detected (HERFD) X-ray absorption near-edge spectroscopy (XANES) to study iron carbonyl complexes. Mono-, bi-, and tri-nuclear carbonyl complexes and pure carbonyl complexes as well as carbonyl complexes containing hydrocarbon ligands are considered. The HERFD-XANES spectra reveal multiple pre-edge peaks with individual signatures for each complex, which could not be detected previously with conventional XANES spectroscopy.

Rac-mediated Stimulation of Phospholipase Cγ2 Amplifies B Cell Receptor-induced Calcium Signaling.

The Rho GTPase Rac is crucially involved in controlling multiple B cell functions, including those regulated by the B cell receptor (BCR) through increased cytosolic Ca(2+). The underlying molecular mechanisms and their relevance to the functions of intact B cells have thus far remained unknown. We have previously shown that the activity of phospholipase Cγ2 (PLCγ2), a key constituent of the BCR signalosome, is stimulated by activated Rac through direct protein-protein interaction.

Single-molecule force spectroscopy of membrane proteins from membranes freely spanning across nanoscopic pores.

Single-molecule force spectroscopy (SMFS) provides detailed insight into the mechanical (un)folding pathways and structural stability of membrane proteins. So far, SMFS could only be applied to membrane proteins embedded in native or synthetic membranes adsorbed to solid supports. This adsorption causes experimental limitations and raises the question to what extent the support influences the results obtained by SMFS.

Ultra-large scale AFM of lipid droplet arrays: investigating the ink transfer volume in dip pen nanolithography.

There are only few quantitative studies commenting on the writing process in dip-pen nanolithography with lipids. Lipids are important carrier ink molecules for the delivery of bio-functional patters in bio-nanotechnology. In order to better understand and control the writing process, more information on the transfer of lipid material from the tip to the substrate is needed.

Ligand-Dependent Nanoparticle Clustering within Lipid Membranes Induced by Surrounding Medium.

The interactions between hydrophobic or semihydrophobic gold and silver nanoparticles (NPs) and a dimyristoylphosphatidylcholine (DMPC) bilayer as a model cell membrane in two ionic solutions result in the structural reorganization within the bilayer manifested as locally increased nanomechanical compaction in the vicinity of NP clusters as well as changed overall thermotropic properties. The effects of NP surface charge and hydrophobicity were examined using AFM imaging, force spectroscopy and IR spectroscopy. The NP clustering occurred during hydration process of dry films containing both the DMPC molecules and the NPs by the mechanism in which the number of bilayer deformations was reduced by NP clustering.

Quantitating membrane bleb stiffness using AFM force spectroscopy and an optical sideview setup.

AFM-based force spectroscopy in combination with optical microscopy is a powerful tool for investigating cell mechanics and adhesion on the single cell level. However, standard setups featuring an AFM mounted on an inverted light microscope only provide a bottom view of cell and AFM cantilever but cannot visualize vertical cell shape changes, for instance occurring during motile membrane blebbing. Here, we have integrated a mirror-based sideview system to monitor cell shape changes resulting from motile bleb behavior of Xenopus cranial neural crest (CNC) cells during AFM elasticity and adhesion measurements.

A photolithographic approach to spatially resolved cross-linked nanolayers.

The preparation of cross-linked nanosheets with 1-2 nm thickness and predefined shape was achieved by lithographic immobilization of trimethacryloyl thioalkanoates onto the surface of Si wafers, which were functionalized with 2-(phenacylthio)acetamido groups via a photoinduced reaction. Subsequent cross-linking via free radical polymerization as well as a phototriggered Diels-Alder reaction under mild conditions on the surface led to the desired nanosheets. Electrospray ionization mass spectrometry (ESI-MS), X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), as well as infrared reflection-absorption spectroscopy (IRRAS) confirmed the success of individual surface-modification and cross-linking reactions.