Neutron interference from a split-crystal interferometer.

The first successful operation of a neutron interferometer with a separate beam-recombining crystal is reported. This result was achieved at the neutron interferometry setup S18 at the ILL in Grenoble by a collaboration between TU Wien, ILL, Grenoble, and INRIM, Torino. While previous interferometers have been machined out of a single-crystal block, in this work two crystals were successfully aligned on nanoradian and picometre scales, as required to obtain neutron interference. As a decisive proof-of-principle demonstration, this opens the door to a new generation of neutron interferometers and exciting applications.

Insecticidal Activity of a Destruxin-Containing Extract of Metarhizium brunneum Against Ceratitis capitata (Diptera: Tephritidae).

Tephritid fruit flies are major pests that limit fruit production around the world; they cause important damages, increasing directly and indirectly annual costs, and their management is predominately based on the use of chemical insecticides. This research investigated the insecticidal activity of the crude extract obtained of Metarhizium brunneum Petch EAMb 09/01-Su strain and its capacity to secrete secondary metabolites including destruxins (dtx). Dtx A and A2 had insecticidal activity against Ceratitis capitata (Wiedemann) when administered per os. The crude extract of seven Metarhizium and one Beauveria isolates were evaluated per os against medfly adults. The crude extracts of the isolate EAMb 09/01-Su resulted in mortality ranging between 95 and 100% at 48 h. The high-pressure liquid chromatography profile showed two active peaks (F5B and F6 subfractions) related with dtx A2 and dtx A, which caused 70 and 100% mortality on C. capitata at 48 h postfeeding, respectively. The LC50 was 104.92 ppm of dtx A, contained in the F6 subfraction, and the LT50 was 4.16 h at a concentration of 400 ppm of dtx A contained in the F6 subfraction. Moreover, the average survival time of adults exposed to this subfraction was 12.6 h with only 1 h of exposure. The insecticide metabolites of the F6 subfraction of the EAMb 09/01-Su isolate retained >90% of its insecticidal activity after exposure to 60°C for 2 h and 120°C for 20 min. These results highlight the potential of this strain as a source of new insecticidal compounds of natural origin for fruit fly control.

Quantum Hall resistance standard in graphene devices under relaxed experimental conditions.

The quantum Hall effect provides a universal standard for electrical resistance that is theoretically based on only the Planck constant h and the electron charge e. Currently, this standard is implemented in GaAs/AlGaAs, but graphene's electronic properties have given hope for a more practical device. Here, we demonstrate that the experimental conditions necessary for the operation of devices made of high-quality graphene grown by chemical vapour deposition on silicon carbide can be extended and significantly relaxed compared with those for state-of-the-art GaAs/AlGaAs devices. In particular, the Hall resistance can be accurately quantized to within 1 × 10(-9) over a 10 T wide range of magnetic flux density, down to 3.5 T, at a temperature of up to 10 K or with a current of up to 0.5 mA. This experimental simplification highlights the great potential of graphene in the development of user-friendly and versatile quantum standards that are compatible with broader industrial uses beyond those in national metrology institutes. Furthermore, the measured agreement of the quantized Hall resistance in graphene and GaAs/AlGaAs, with an ultimate uncertainty of 8.2 × 10(-11), supports the universality of the quantum Hall effect. This also provides evidence of the relation of the quantized Hall resistance with h and e, which is crucial for the new Système International d'unités to be based on fixing such fundamental constants of nature.

Quantum Hall resistance standards from graphene grown by chemical vapour deposition on silicon carbide.

Replacing GaAs by graphene to realize more practical quantum Hall resistance standards (QHRS), accurate to within 10(-9) in relative value, but operating at lower magnetic fields than 10 T, is an ongoing goal in metrology. To date, the required accuracy has been reported, only few times, in graphene grown on SiC by Si sublimation, under higher magnetic fields. Here, we report on a graphene device grown by chemical vapour deposition on SiC, which demonstrates such accuracies of the Hall resistance from 10 T up to 19 T at 1.4 K. This is explained by a quantum Hall effect with low dissipation, resulting from strongly localized bulk states at the magnetic length scale, over a wide magnetic field range. Our results show that graphene-based QHRS can replace their GaAs counterparts by operating in as-convenient cryomagnetic conditions, but over an extended magnetic field range. They rely on a promising hybrid and scalable growth method and a fabrication process achieving low-electron-density devices.

High Electron Mobility in Epitaxial Graphene on 4H-SiC(0001) via post-growth annealing under hydrogen.

We investigate the magneto-transport properties of epitaxial graphene single-layer on 4H-SiC(0001), grown by atmospheric pressure graphitization in Ar, followed by H2 intercalation. We directly demonstrate the importance of saturating the Si dangling bonds at the graphene/SiC(0001) interface to achieve high carrier mobility. Upon successful Si dangling bonds elimination, carrier mobility increases from 3 000 cm(2)V(-1)s(-1) to >11 000 cm(2)V(-1)s(-1) at 0.3 K. Additionally, graphene electron concentration tends to decrease from a few 10(12) cm(-2) to less than 10(12) cm(-2). For a typical large (30 × 280 µm(2)) Hall bar, we report the observation of the integer quantum Hall states at 0.3 K with well developed transversal resistance plateaus at Landau level filling factors of ν = 2, 6, 10, 14... 42 and Shubnikov de Haas oscillation of the longitudinal resistivity observed from about 1 T. In such a device, the Hall state quantization at ν = 2, at 19 T and 0.3 K, can be very robust: the dissipation in electronic transport can stay very low, with the longitudinal resistivity lower than 5 mΩ, for measurement currents as high as 250 µA. This is very promising in the view of an application in metrology.

Occurrence of plant growth regulators in Psilotum nudum.

The endogenous content of the auxin indole-3-acetic acid (IAA), the cytokinins trans-zeatin (tZ), trans-zeatin riboside (tZR), dihydrozeatin (DHZ), dihydrozeatin riboside (DHZR), isopentenyladenine (iP) and isopentenyladenosine (iPR), the gibberellins GA(1), GA(3), GA(4), GA(7), GA(9) and GA(20) in the rhizome and aerial shoots during and after sporogenesis were measured by high-performance liquid chromatography-tandem mass spectrometry in the fern Psilotum nudum. The present study shows, for the first time, the presence of the auxin IAA, the cytokinins tZR, DHZR and iP, and the gibberellins GA(4), GA(9) and GA(20) in the rhizome and aerial shoots of this species and suggests a possible role of gibberellins in the evolution of ferns.

Toll-like receptor 2 is critical for induction of Reg3 beta expression and intestinal clearance of Yersinia pseudotuberculosis.

OBJECTIVE: Yersinia pseudotuberculosis causes ileitis and mesenteric lymphadenitis by mainly invading the Peyer's patches that are positioned in the terminal ileum. Whereas toll-like-receptor 2 (TLR2) controls mucosal inflammation by detecting certain microbiota-derived signals, its exact role in protecting Peyer's patches against bacterial invasion has not been defined. DESIGN: Wild-type, Tlr2-, Nod2- and MyD88-deficient animals were challenged by Y pseudotuberculosis via the oral or systemic route. The role of microbiota in conditioning Peyer's patches against Yersinia through TLR2 was assessed by delivering, ad libitum, exogenous TLR2 agonists in drinking water to germ-free and streptomycin-treated animals. Bacterial eradication from Peyer's patches was measured by using a colony-forming unit assay. Expression of cryptdins and the c-type lectin Reg3 beta was quantified by quantitative reverse transcriptase polymerase chain reaction analysis. RESULTS: Our data demonstrated that Tlr2-deficient mice failed to limit Yersinia dissemination from the Peyer's patches and succumbed to sepsis independently of nucleotide-binding and oligomerisation domain 2 (NOD2). Recognition of both microbiota-derived and myeloid differentiation factor 88 (MyD88)-mediated elicitors was found to be critically involved in gut protection against Yersinia-induced lethality, while TLR2 was dispensable to systemic Yersinia infection. Gene expression analyses revealed that optimal epithelial transcript level of the anti-infective Reg3 beta requires TLR2 activation. Consistently, Yersinia infection triggered TLR2-dependent Reg3 beta expression in Peyer's patches. Importantly, oral treatment with exogenous TLR2 agonists in germ-free animals was able to further enhance Yersinia-induced expression of Reg3 beta and to restore intestinal resistance to Yersinia. Lastly, genetic ablation of Reg3 beta resulted in impaired clearance of the bacterial load in Peyer's patches. CONCLUSIONS: TLR2/REG3 beta is thus an essential component in conditioning epithelial defence signalling pathways against bacterial invasion.

Interspecific control of non-symbiotic carbon partitioning in the rhizosphere of a grass-clover association: Bromus madritensis-Trifolium angustifolium.

Grass-legume interaction in the rhizosphere was investigated in a greenhouse experiment with two annual species, bromegrass Bromus madritensis (L.) and clover Trifolium angustifolium (L.) grown in mono and mixed cultures. Partitioning of below-ground carbon between roots, respiration, and soil was measured after separate 2 h-labelling of each species with 14CO2 followed by a 9 d chase period. At the time of labelling, clover nodules were not yet fixing N2. Bromegrass grew much faster than clover. Shoot biomass of bromegrass was greater in the presence of clover than in monoculture. By contrast, both shoot and root biomass of clover was less in the presence of bromegrass than in monoculture. Carbon assimilation during the period of labelling was proportional to shoot biomass and partitioning above and below-ground did not differ among treatments. Absolute amounts of labelled C allocated to rhizosphere respiration was more in bromegrass than in clover (respectively 1.38 mg C against 0.75 mg C in monoculture and 1.79 mg C and 0.63 mg C in mixed culture). However, when expressed as a percentage of below-ground C allocation, rhizosphere respiration was lower in bromegrass than in clover, respectively, 38% and 45% in monoculture. In mixed culture, this percentage increased by 7.3% for clover, and 3.5% for bromegrass, thus indicating that the interspecific effect of grass was higher than that of clover. The percentage of below-ground C in a soil solution of clover in mixed culture was more than 2-fold that measured in monoculture. It was also significantly correlated with the percentage of below-ground C in respiration. These results provided evidence that the grass-legume mixture has the potential to influence the rhizosphere processes of each species in more than an additive way and that the effect of the interaction was stronger on clover than on bromegrass. The possible implications of this in grass-legume competition are discussed.

Web alert: Cell-to-cell contact and extracellular matrix.

A selection of World Wide Web sites relevant to papers published in this issue of Current Opinion in Cell Biology.

Membrane permeability. Membranes and sorting. Web alert.

A selection of World Wide Web sites relevant to papers published in this issue of Current Opinion in Cell Biology.

Nucleus and gene expression: Web alert.

A selection of World Wide Web sites relevant to papers published in this issue of Current Opinion in Cell Biology.

Raft-partitioning of the ubiquitin ligases Cbl and Nedd4 upon IgE-triggered cell signaling.

The high affinity receptor for IgE, FcepsilonRI on mast cells and basophils plays an essential role in immunological defense. Upon multivalent antigen binding, FcepsilonRI becomes phoshorylated by the protein-tyrosine kinase Lyn, as a result of receptor clustering in lipid rafts. FcepsilonRI has been shown to be ubiquitinated. Ubiquitination can lead to degradation by proteasomes, but it can also act as a sorting signal to internalize proteins destined to the endosomal/lysosomal pathway. We have analyzed whether FcepsilonRI ubiquitination takes place within rafts. We report biochemical and imaging evidence in rat basoleukemia cells for the presence of ubiquitinated FcepsilonRI in clustered rafts upon receptor activation. Moreover, we demonstrated that the ubiquitin ligases Cbl and Nedd4 colocalize with FcepsilonRI patches and showed that both ligases become associated with lipid rafts after activation of IgE signaling. Because Cbl is known to interact with the FcepsilonRI signaling complex, ubiquitination is likely to be an important parameter regulating IgE-triggered signaling occurring in rafts.

Web alert

A selection of World Wide Web sites relevant to papers published in this issue of Current Opinion in Cell Biology.

Cell-to-cell contact and extracellular matrix. Web alert.

A selection of World Wide Web sites relevant to papers published in this issue of Current Opinion in Cell Biology.

Apical membrane targeting of Nedd4 is mediated by an association of its C2 domain with annexin XIIIb.

Nedd4 is a ubiquitin protein ligase (E3) containing a C2 domain, three or four WW domains, and a ubiquitin ligase HECT domain. We have shown previously that the C2 domain of Nedd4 is responsible for its Ca(2+)-dependent targeting to the plasma membrane, particularly the apical region of epithelial MDCK cells. To investigate this apical preference, we searched for Nedd4-C2 domain-interacting proteins that might be involved in targeting Nedd4 to the apical surface. Using immobilized Nedd4-C2 domain to trap interacting proteins from MDCK cell lysate, we isolated, in the presence of Ca(2+), a approximately 35-40-kD protein that we identified as annexin XIII using mass spectrometry. Annexin XIII has two known isoforms, a and b, that are apically localized, although XIIIa is also found in the basolateral compartment. In vitro binding and coprecipitation experiments showed that the Nedd4-C2 domain interacts with both annexin XIIIa and b in the presence of Ca(2+), and the interaction is direct and optimal at 1 microM Ca(2+). Immunofluorescence and immunogold electron microscopy revealed colocalization of Nedd4 and annexin XIIIb in apical carriers and at the apical plasma membrane. Moreover, we show that Nedd4 associates with raft lipid microdomains in a Ca(2+)-dependent manner, as determined by detergent extraction and floatation assays. These results suggest that the apical membrane localization of Nedd4 is mediated by an association of its C2 domain with the apically targeted annexin XIIIb.

Different properties of two isoforms of annexin XIII in MDCK cells.

Annexins form a family of proteins that are widely expressed and known to bind membranes in the presence of calcium. Two isoforms of the annexin XIII subfamily are expressed in epithelia. We previously reported that annexin XIIIb is apically localized in MDCK cells and that it is involved in raft-mediated delivery of apical proteins. We have now analyzed the properties of annexin XIIIa, which differs from annexin XIIIb by a deletion of 41 amino acids in the amino-terminal domain, and is distributed both apically and basolaterally. Annexin XIIIa binding to membranes is independent of calcium but requires its myristoyl amino-terminal modification, as observed with annexin XIIIb. Our biochemical and functional data show that annexin XIIIa behaves differently in the apical and in the basolateral compartments. Whereas annexin XIIIa apically can associate with rafts independently of calcium, the basolateral pool requires calcium for this. Annexin XIIIa, like annexin XIIIb, stimulates apical transport of influenza virus hemagglutinin but, in contrast, only annexin XIIIa inhibits basolateral transport of vesicular stomatitis virus G protein. Our results suggest that annexin XIIIa and XIIIb have specific roles in epithelial cells, and because of their structural similarities, these isoforms offer interesting tools for unravelling the functions of annexins.

Rapid determination of chlorogenic acid and related compounds in sunflower seeds by high-performance liquid chromatography/atmospheric pressure chemical ionization mass spectrometry.

High-performance liquid chromatography (HPLC) in combination with atmospheric pressure chemical ionization mass spectrometry (APcI-MS) was applied to the determination of the phenolic fraction found in methanolic extracts of sunflower seeds (mainly chlorogenic acid and derived compounds). These extracts were directly separated by HPLC and detected by both negative and positive APcI-MS. Abundant structural information about these compounds can be obtained even at low extraction cone voltages. This method has been shown to be a rapid and effective method for the analysis of crude extracts from sunflower seeds.