Conceptual mechanization studies for a horizon definition spacecraft electrical power subsystem

Solar cell-battery electrical power subsystem for horizon definition spacecraf

Surface specific peptide immobilization on radiografted polymers as potential screening assays for antiangiogenic immunotherapy

International audienceAngiogenesis is a key process of cancer development and metastasis. It's inhibition is an important and promising strategy to block tumor growth and invasion. One of these approaches, based on antiangiogenic immunotherapy, is the recognition of a specific region of an angiogenic growth factor, called VEGF-A, by monoclonal antibodies. Thus, we aimed to design a novel assay to screen potential monoclonal antibodies directed against VEGF-A. In a first approach, we chose to perform covalent coupling of angiogenesis active cyclopeptides onto biocompatible thermoplastic transparent PVDF films and to fully characterize the chemical structure, the surface state and the biochemical properties of the synthesized devices. Electron beam radiation created radical sites on PVDF films without adding any toxic chemicals. These primary radicals and some induced peroxides were used as initiators for acrylic acid polymerization. Under our experimental conditions, surface grafting was favoured. Functionalization of PVDF-g-PAA films with peptides via a spacer arm was possible by performing two subsequent coupling reactions. EDC was used as coupling agent. Spacer arm saturation of the film surface was achieved for 25 mol% yield meaning that one spacer arm on four carboxylic acids were covalently bound. Peptide immobilization resulted in binding 10 times less leading to a final 3 mol% yield. Binding densities are governed by their individual space requirements. Each chemical step has been followed by FTIR in ATR mode, NMR using HR MAS technique and XPS. From XPS results, a layer of peptide covered PVDF-g-PAA film surface. The amounts of covalently immobilized peptide were determined using indirect UV spectroscopy on supernatant reaction solution. Yields were correlated with high resolution NMR results. The peptide/antibody recognition validated our system showing the conservation of peptide tridimensional structure with a positive response to specific antibodies. Because of the covalent protein linkage to PVDF films, a simple cleaning with immunoaffinity chromatography buffer allows the films to be reused

Structural and Functional Analysis of a β2-Adrenergic Receptor Complex with GRK5.

The phosphorylation of agonist-occupied G-protein-coupled receptors (GPCRs) by GPCR kinases (GRKs) functions to turn off G-protein signaling and turn on arrestin-mediated signaling. While a structural understanding of GPCR/G-protein and GPCR/arrestin complexes has emerged in recent years, the molecular architecture of a GPCR/GRK complex remains poorly defined. We used a comprehensive integrated approach of cross-linking, hydrogen-deuterium exchange mass spectrometry (MS), electron microscopy, mutagenesis, molecular dynamics simulations, and computational docking to analyze GRK5 interaction with the β2-adrenergic receptor (β2AR). These studies revealed a dynamic mechanism of complex formation that involves large conformational changes in the GRK5 RH/catalytic domain interface upon receptor binding. These changes facilitate contacts between intracellular loops 2 and 3 and the C terminus of the β2AR with the GRK5 RH bundle subdomain, membrane-binding surface, and kinase catalytic cleft, respectively. These studies significantly contribute to our understanding of the mechanism by which GRKs regulate the function of activated GPCRs. PAPERCLIP

Thermoelectric spin voltage in graphene

In recent years, new spin-dependent thermal effects have been discovered in ferromagnets, stimulating a growing interest in spin caloritronics, a field that exploits the interaction between spin and heat currents. Amongst the most intriguing phenomena is the spin Seebeck effect, in which a thermal gradient gives rise to spin currents that are detected through the inverse spin Hall effect. Non-magnetic materials such as graphene are also relevant for spin caloritronics, thanks to efficient spin transport, energy-dependent carrier mobility and unique density of states. Here, we propose and demonstrate that a carrier thermal gradient in a graphene lateral spin valve can lead to a large increase of the spin voltage near to the graphene charge neutrality point. Such an increase results from a thermoelectric spin voltage, which is analogous to the voltage in a thermocouple and that can be enhanced by the presence of hot carriers generated by an applied current. These results could prove crucial to drive graphene spintronic devices and, in particular, to sustain pure spin signals with thermal gradients and to tune the remote spin accumulation by varying the spin-injection bias

Root vacuolar sequestration and suberization are prominent responses of Pistacia spp. rootstocks during salinity stress

Understanding the mechanisms of stress tolerance in diverse species is needed to enhance crop performance under conditions such as high salinity. Plant roots, in particular in grafted agricultural crops, can function as a boundary against external stresses in order to maintain plant fitness. However, limited information exists for salinity stress responses of woody species and their rootstocks. Pistachio (Pistacia spp.) is a tree nut crop with relatively high salinity tolerance as well as high genetic heterogeneity. In this study, we used a microscopy-based approach to investigate the cellular and structural responses to salinity stress in the roots of two pistachio rootstocks, Pistacia integerrima (PGI) and a hybrid, P. atlantica x P. integerrima (UCB1). We analyzed root sections via fluorescence microscopy across a developmental gradient, defined by xylem development, for sodium localization and for cellular barrier differentiation via suberin deposition. Our cumulative data suggest that the salinity response in pistachio rootstock species is associated with both vacuolar sodium ion (Na+) sequestration in the root cortex and increased suberin deposition at apoplastic barriers. Furthermore, both vacuolar sequestration and suberin deposition correlate with the root developmental gradient. We observed a higher rate of Na+ vacuolar sequestration and reduced salt-induced leaf damage in UCB1 when compared to P. integerrima. In addition, UCB1 displayed higher basal levels of suberization, in both the exodermis and endodermis, compared to P. integerrima. This difference was enhanced after salinity stress. These cellular characteristics are phenotypes that can be taken into account during screening for sodium-mediated salinity tolerance in woody plant species

D 4 dopamine receptor high-resolution structures enable the discovery of selective agonists

Dopamine receptors are G protein-coupled receptors implicated in many neurological disorders. Different families of dopamine receptors are involved in different signaling pathways, so specificity is a key goal of therapeutics. Wang et al. present high-resolution crystal structures of the DRD4 dopamine receptor bound to the antipsychotic drug nemonapride. The high resolution of the structures facilitated ligand docking, and a DRD4-selective agonist was identified by computational screening of a large library, experimental testing of compounds with the best docking scores, and iterative cycles of docking and testing analogs of those compounds. The identified agonist had a high affinity for DRD4 and no measurable affinity for DRD2 or DRD3. Science , this issue p. [381][1] [1]: /lookup/doi/10.1126/science.aan546

High fidelity optical preparation and coherent Larmor precession of a single hole in an InGaAs quantum dot molecule

We employ ultrafast pump-probe spectroscopy with photocurrent readout to directly probe the dynamics of a single hole spin in a single, electrically tunable self-assembled quantum dot molecule formed by vertically stacking InGaAs quantum dots. Excitons with defined spin configurations are initialized in one of the two dots using circularly polarized picosecond pulses. The time-dependent spin configuration is probed by the spin selective optical absorption of the resulting few Fermion complex. Taking advantage of sub-5 ps electron tunneling to an orbitally excited state of the other dot, we initialize a single hole spin with a purity of >96%, i.e., much higher than demonstrated in previous single dot experiments. Measurements in a lateral magnetic field monitor the coherent Larmor precession of the single hole spin with no observable loss of spin coherence within the ~300 ps hole lifetime. Thereby, the purity of the hole spin initialization remains unchanged for all investigated magnetic fields

Two-dimensional discrete wavelet analysis of multiparticle event topology in heavy ion collisions

The event-by-event analysis of multiparticle production in high energy hadron and nuclei collisions can be performed using the discrete wavelet transformation. The ring-like and jet-like structures in two-dimensional angular histograms are well extracted by wavelet analysis. For the first time the method is applied to the jet-like events with background simulated by event generators, which are developed to describe nucleus-nucleus collisions at LHC energies. The jet positions are located quite well by the discrete wavelet transformation of angular particle distribution even in presence of strong background.Comment: 6 pages, 6 figure

Crystal Structure of an LSD-Bound Human Serotonin Receptor

SummaryThe prototypical hallucinogen LSD acts via serotonin receptors, and here we describe the crystal structure of LSD in complex with the human serotonin receptor 5-HT2B. The complex reveals conformational rearrangements to accommodate LSD, providing a structural explanation for the conformational selectivity of LSD's key diethylamide moiety. LSD dissociates exceptionally slow from both 5-HT2BR and 5-HT2AR—a major target for its psychoactivity. Molecular dynamics (MD) simulations suggest that LSD's slow binding kinetics may be due to a "lid" formed by extracellular loop 2 (EL2) at the entrance to the binding pocket. A mutation predicted to increase the mobility of this lid greatly accelerates LSD's binding kinetics and selectively dampens LSD-mediated β-arrestin2 recruitment. This study thus reveals an unexpected binding mode of LSD; illuminates key features of its kinetics, stereochemistry, and signaling; and provides a molecular explanation for LSD's actions at human serotonin receptors.PaperCli