2,704 research outputs found
OCRL1 engages with the F-BAR protein pacsin 2 to promote biogenesis of membrane-trafficking intermediates
Mutation of the inositol 5-phosphatase OCRL1 causes Lowe syndrome and Dent-2 disease. Loss of OCRL1 function perturbs several cellular processes, including membrane traffic, but the underlying mechanisms remain poorly defined. Here we show that OCRL1 is part of the membrane-trafficking machinery operating at the trans-Golgi network (TGN)/endosome interface. OCRL1 interacts via IPIP27A with the F-BAR protein pacsin 2. OCRL1 and IPIP27A localize to mannose 6-phosphate receptor (MPR)–containing trafficking intermediates, and loss of either protein leads to defective MPR carrier biogenesis at the TGN and endosomes. OCRL1 5-phosphatase activity, which is membrane curvature sensitive, is stimulated by IPIP27A-mediated engagement of OCRL1 with pacsin 2 and promotes scission of MPR-containing carriers. Our data indicate a role for OCRL1, via IPIP27A, in regulating the formation of pacsin 2–dependent trafficking intermediates and reveal a mechanism for coupling PtdIns(4,5)P2 hydrolysis with carrier biogenesis on endomembranes
From z>6 to z~2: Unearthing Galaxies at the Edge of the Dark Ages
Galaxies undergoing formation and evolution can now be observed over a time
baseline of some 12 Gyr. An inherent difficulty with high-redshift observations
is that the objects are very faint and the best resolution (HST) is only ~0.5
kpc. Such studies thereby combine in a highly synergistic way with the great
detail that can be obtained for nearby galaxies. 3 new developments are
highlighted. First is the derivation of stellar masses for galaxies from SEDs
using HST and now Spitzer data, and dynamical masses from both sub-mm
observations of CO lines and near-IR observations of optical lines like Halpha.
A major step has been taken with evidence that points to the z~2-3 LBGs having
masses that are a few x 10^10 Msolar. Second is the discovery of a population
of evolved red galaxies at z~2-3 which appear to be the progenitors of the more
massive early-type galaxies of today, with dynamical masses around a few x
10^11 Msolar. Third are the remarkable advances that have occurred in
characterizing dropout galaxies to z~6 and beyond, < 1 Gyr from recombination.
The HST ACS has played a key role here, with the dropout technique being
applied to i & z images in several deep ACS fields, yielding large samples of
these objects. This has allowed a detailed determination of their properties
and meaningful comparisons against lower-z samples. The use of cloning
techniques has overcome many of the strong selection biases affecting the study
of these objects. A clear trend of size with redshift has been identified, and
its impact on the luminosity density and SFR estimated. There is a significant
though modest decrease in the SFR from z~2.5 to z~6. The latest data also allow
for the first robust determination of the LF at z~6. Finally, the latest UDF
ACS and NICMOS data has resulted in the detection of some galaxies at z~7-8.Comment: 18 pages, 8 figures. To appear in Penetrating Bars through Masks of
Cosmic Dust: The Hubble Tuning Fork Strikes a New Note, eds. D. Block, K.
Freeman, R. Groess, I. Puerari, & E.K. Block (Dordrecht: Kluwer), in pres
The Meissner effect in a strongly underdoped cuprate above its critical temperature
The Meissner effect and the associated perfect "bulk" diamagnetism together
with zero resistance and gap opening are characteristic features of the
superconducting state. In the pseudogap state of cuprates unusual diamagnetic
signals as well as anomalous proximity effects have been detected but a
Meissner effect has never been observed. Here we have probed the local
diamagnetic response in the normal state of an underdoped La1.94Sr0.06CuO4
layer (up to 46 nm thick, critical temperature Tc' < 5 K) which was brought
into close contact with two nearly optimally doped La1.84Sr0.16CuO4 layers (Tc
\approx 32 K). We show that the entire 'barrier' layer of thickness much larger
than the typical c axis coherence lengths of cuprates exhibits a Meissner
effect at temperatures well above Tc' but below Tc. The temperature dependence
of the effective penetration depth and superfluid density in different layers
indicates that superfluidity with long-range phase coherence is induced in the
underdoped layer by the proximity to optimally doped layers; however, this
induced order is very sensitive to thermal excitation.Comment: 7 pages, 7 figures + Erratu
Fully gapped topological surface states in BiSe films induced by a d-wave high-temperature superconductor
Topological insulators are a new class of materials, that exhibit robust
gapless surface states protected by time-reversal symmetry. The interplay
between such symmetry-protected topological surface states and symmetry-broken
states (e.g. superconductivity) provides a platform for exploring novel quantum
phenomena and new functionalities, such as 1D chiral or helical gapless
Majorana fermions, and Majorana zero modes which may find application in
fault-tolerant quantum computation. Inducing superconductivity on topological
surface states is a prerequisite for their experimental realization. Here by
growing high quality topological insulator BiSe films on a d-wave
superconductor BiSrCaCuO using molecular beam epitaxy,
we are able to induce high temperature superconductivity on the surface states
of BiSe films with a large pairing gap up to 15 meV. Interestingly,
distinct from the d-wave pairing of BiSrCaCuO, the
proximity-induced gap on the surface states is nearly isotropic and consistent
with predominant s-wave pairing as revealed by angle-resolved photoemission
spectroscopy. Our work could provide a critical step toward the realization of
the long sought-after Majorana zero modes.Comment: Nature Physics, DOI:10.1038/nphys274
Grain Alignment in Molecular Clouds
One of the most informative techniques of studying magnetic fields in
molecular clouds is based on the use of starlight polarization and polarized
emission arising from aligned dust. How reliable the interpretation of the
polarization maps in terms of magnetic fields is the issue that the grain
alignment theory addresses.
I briefly review basic physical processes involved in grain alignment.Comment: 8 papes, 1 figures, to appear in Zermatt proceeding
Luminescent Organic–Inorganic Hybrids of Functionalized Mesoporous Silica SBA-15 by Thio-Salicylidene Schiff Base
Novel organic–inorganic mesoporous luminescent hybrid material N, N′-bis(salicylidene)-thiocarbohydrazide (BSTC-SBA-15) has been obtained by co-condensation of tetraethyl orthosilicate and the organosilane in the presence of Pluronic P123 surfactant as a template. N,N′-bis(salicylidene)-thiocarbohydrazide (BSTC) grafted to the coupling agent 3-(triethoxysilyl)-propyl isocyanate (TESPIC) was used as the precursor for the preparation of mesoporous materials. In addition, for comparison, SBA-15 doped with organic ligand BSTC was also synthesized, denoted as BSTC/SBA-15. This organic–inorganic hybrid material was well-characterized by X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy (HRTEM), and photoluminescence spectra, which reveals that they all have high surface area, uniformity in the mesostructure. The resulting materials (BSTC-SBA-15 and BSTC/SBA-15) exhibit regular uniform microstructures, and no phase separation happened for the organic and the inorganic compounds was covalently linked through Si–O bonds via a self-assemble process. Furthermore, the two materials have different luminescence range: BSTC/SBA-15 presents the strong dominant green luminescence, while BSTC-functionalized material BSTC-SBA-15 shows the dominant blue emission
Enhanced Microwave Absorption Properties of Intrinsically Core/shell Structured La0.6Sr0.4MnO3Nanoparticles
The intrinsically core/shell structured La0.6Sr0.4MnO3nanoparticles with amorphous shells and ferromagnetic cores have been prepared. The magnetic, dielectric and microwave absorption properties are investigated in the frequency range from 1 to 12 GHz. An optimal reflection loss of −41.1 dB is reached at 8.2 GHz with a matching thickness of 2.2 mm, the bandwidth with a reflection loss less than −10 dB is obtained in the 5.5–11.3 GHz range for absorber thicknesses of 1.5–2.5 mm. The excellent microwave absorption properties are a consequence of the better electromagnetic matching due to the existence of the protective amorphous shells, the ferromagnetic cores, as well as the particular core/shell microstructure. As a result, the La0.6Sr0.4MnO3nanoparticles with amorphous shells and ferromagnetic cores may become attractive candidates for the new types of electromagnetic wave absorption materials
Refractory dispersion promotes conduction disturbance and arrhythmias in a Scn5a+/− mouse model
Accentuated right ventricular (RV) gradients in action potential duration (APD) have been implicated in the arrhythmogenicity observed in Brugada syndrome in studies assuming that ventricular effective refractory periods (VERPs) vary in concert with APDs. The present experiments use a genetically modified mouse model to explore spatial heterogeneities in VERP that in turn might affect conduction velocity, thereby causing arrhythmias. Activation latencies, APDs and VERPs recorded during programmed S1S2 protocols were compared in RV and left ventricular (LV) epicardia and endocardia of Langendorff-perfused wild-type (WT) and Scn5a+/− hearts. Scn5a+/− and WT hearts showed similar patterns of shorter VERPs in RV than LV epicardia, and in epicardia than endocardia. However, Scn5a+/− hearts showed longer VERPs, despite shorter APD90s, than WT in all regions examined. The pro- and anti-arrhythmic agents flecainide and quinidine increased regional VERPs despite respectively decreasing and increasing the corresponding APD90s particularly in Scn5a+/− RV epicardia. In contrast, Scn5a+/− hearts showed greater VERP gradients between neighbouring regions, particularly RV transmural gradients, than WT (9.1 ± 1.1 vs. 5.7 ± 0.5 ms, p < 0.05, n = 12). Flecainide increased (to 21 ± 0.9 ms, p < 0.05, n = 6) but quinidine decreased (to 4.5 ± 0.5 ms, p < 0.05, n = 6) these gradients, particularly across the Scn5a+/− RV. Finally, Scn5a+/− hearts showed greater conduction slowing than WT following S2 stimuli, particularly with flecainide administration. Rather than arrhythmogenesis resulting from increased transmural repolarization gradients in an early, phase 2, reentrant excitation mechanism, the present findings implicate RV VERP gradients in potential reentrant mechanisms involving impulse conduction slowed by partial refractoriness
Dufulin Activates HrBP1 to Produce Antiviral Responses in Tobacco
BACKGROUND: Dufulin is a new antiviral agent that is highly effective against plant viruses and acts by activating systemic acquired resistance (SAR) in plants. In recent years, it has been used widely to prevent and control tobacco and rice viral diseases in China. However, its targets and mechanism of action are still poorly understood. METHODOLOGY/PRINCIPAL FINDINGS: Here, differential in-gel electrophoresis (DIGE) and classical two-dimensional electrophoresis (2-DE) techniques were combined with mass spectrometry (MS) to identify the target of Dufulin. More than 40 proteins were found to be differentially expressed (≥1.5 fold or ≤1.5 fold) upon Dufulin treatment in Nicotiana tabacum K(326). Based on annotations in the Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) databases, these proteins were found to be related to disease resistance. Directed acyclic graph (DAG) analysis of the various pathways demonstrated harpin binding protein-1 (HrBP1) as the target of action of Dufulin. Additionally, western blotting, semi-quantitative reverse transcription polymerase chain reaction (RT-PCR), and real time PCR analyses were also conducted to identify the specific mechanism of action of Dufulin. Our results show that activation of HrBP1 triggers the salicylic acid (SA) signaling pathway and thereby produces antiviral responses in the plant host. A protective assay based on lesion counting further confirmed the antiviral activity of Dufulin. CONCLUSION: This study identified HrBP1 as a target protein of Dufulin and that Dufulin can activate the SA signaling pathway to induce host plants to generate antiviral responses
Polymicrobial Nature of Chronic Diabetic Foot Ulcer Biofilm Infections Determined Using Bacterial Tag Encoded FLX Amplicon Pyrosequencing (bTEFAP)
Diabetic extremity ulcers are associated with chronic infections. Such ulcer infections are too often followed by amputation because there is little or no understanding of the ecology of such infections or how to control or eliminate this type of chronic infection. A primary impediment to the healing of chronic wounds is biofilm phenotype infections. Diabetic foot ulcers are the most common, disabling, and costly complications of diabetes. Here we seek to derive a better understanding of the polymicrobial nature of chronic diabetic extremity ulcer infections. spp. and against difficult to culture bacteria such as anaerobes. While PCR methods also have bias, further work is now needed in comparing traditional culture results to high-resolution molecular diagnostic methods such as bTEFAP
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