Erratum for the Research Article "Reducing foods environmental impacts through producers and consumers" by J. Poore and T. Nemecek
Source: ScienceNOW - February 21, 2019 Category: Science Tags: Errata Source Type: news
Latrophilin GPCRs direct synapse specificity by coincident binding of FLRTs and teneurins
Bidirectional signaling by cell adhesion molecules is thought to mediate synapse formation, but the mechanisms involved remain elusive. We found that the adhesion G protein–coupled receptors latrophilin-2 and latrophilin-3 selectively direct formation of perforant-path and Schaffer-collateral synapses, respectively, to hippocampal CA1-region neurons. Latrophilin-3 binds to two transcellular ligands: fibronectin leucine-rich repeat transmembrane proteins (FLRTs) and teneurins. In transgenic mice in vivo, both binding activities were required for input-specific synapse formation, which suggests that coincident binding ...
Source: ScienceNOW - February 21, 2019 Category: Science Authors: Sando, R., Jiang, X., Südhof, T. C. Tags: Neuroscience, Online Only r-articles Source Type: news
Structures and operating principles of the replisome
Visualization in atomic detail of the replisome that performs concerted leading– and lagging–DNA strand synthesis at a replication fork has not been reported. Using bacteriophage T7 as a model system, we determined cryo–electron microscopy structures up to 3.2-angstroms resolution of helicase translocating along DNA and of helicase-polymerase-primase complexes engaging in synthesis of both DNA strands. Each domain of the spiral-shaped hexameric helicase translocates sequentially hand-over-hand along a single-stranded DNA coil, akin to the way AAA+ ATPases (adenosine triphosphatases) unfold peptides. Two l...
Source: ScienceNOW - February 21, 2019 Category: Science Authors: Gao, Y., Cui, Y., Fox, T., Lin, S., Wang, H., de Val, N., Zhou, Z. H., Yang, W. Tags: Biochemistry, Online Only r-articles Source Type: news
Ubiquitin-dependent chloroplast-associated protein degradation in plants
Chloroplasts contain thousands of nucleus-encoded proteins that are imported from the cytosol by translocases in the chloroplast envelope membranes. Proteolytic regulation of the translocases is critically important, but little is known about the underlying mechanisms. We applied forward genetics and proteomics in Arabidopsis to identify factors required for chloroplast outer envelope membrane (OEM) protein degradation. We identified SP2, an Omp85-type β-barrel channel of the OEM, and CDC48, a cytosolic AAA+ (ATPase associated with diverse cellular activities) chaperone. Both proteins acted in the same pathway as the ...
Source: ScienceNOW - February 21, 2019 Category: Science Authors: Ling, Q., Broad, W., Trösch, R., Töpel, M., Demiral Sert, T., Lymperopoulos, P., Baldwin, A., Jarvis, R. P. Tags: Botany, Cell Biology, Online Only r-articles Source Type: news
Choreographed entanglement dances: Topological states of quantum matter
It has long been thought that all different phases of matter arise from symmetry breaking. Without symmetry breaking, there would be no pattern, and matter would be featureless. However, it is now clear that for quantum matter at zero temperature, even symmetric disordered liquids can have features, giving rise to topological phases of quantum matter. Some of the topological phases are highly entangled (that is, have topological order), whereas others are weakly entangled (that is, have symmetry-protected trivial order). This Review provides a brief summary of these zero-temperature states of matter and their emergent prop...
Source: ScienceNOW - February 21, 2019 Category: Science Authors: Wen, X.-G. Tags: Online Only, Physics review Source Type: news
Technology Feature | Shotgunning the messenger: Single-cell RNA sequencing
Source: ScienceNOW - February 21, 2019 Category: Science Authors: Dove, A. Tags: opms-sups Source Type: news
Hachimoji DNA and RNA: A genetic system with eight building blocks
We report DNA- and RNA-like systems built from eight nucleotide "letters" (hence the name "hachimoji") that form four orthogonal pairs. These synthetic systems meet the structural requirements needed to support Darwinian evolution, including a polyelectrolyte backbone, predictable thermodynamic stability, and stereoregular building blocks that fit a Schrödinger aperiodic crystal. Measured thermodynamic parameters predict the stability of hachimoji duplexes, allowing hachimoji DNA to increase the information density of natural terran DNA. Three crystal structures show that the synthetic building blocks...
Source: ScienceNOW - February 21, 2019 Category: Science Authors: Hoshika, S., Leal, N. A., Kim, M.-J., Kim, M.-S., Karalkar, N. B., Kim, H.-J., Bates, A. M., Watkins, N. E., SantaLucia, H. A., Meyer, A. J., DasGupta, S., Piccirilli, J. A., Ellington, A. D., SantaLucia, J., Georgiadis, M. M., Benner, S. A. Tags: Biochemistry, Molecular Biology reports Source Type: news
The sleep-wake cycle regulates brain interstitial fluid tau in mice and CSF tau in humans
The sleep-wake cycle regulates interstitial fluid (ISF) and cerebrospinal fluid (CSF) levels of β-amyloid (Aβ) that accumulates in Alzheimer’s disease (AD). Furthermore, chronic sleep deprivation (SD) increases Aβ plaques. However, tau, not Aβ, accumulation appears to drive AD neurodegeneration. We tested whether ISF/CSF tau and tau seeding and spreading were influenced by the sleep-wake cycle and SD. Mouse ISF tau was increased ~90% during normal wakefulness versus sleep and ~100% during SD. Human CSF tau also increased more than 50% during SD. In a tau seeding-and-spreading model, chronic SD inc...
Source: ScienceNOW - February 21, 2019 Category: Science Authors: Holth, J. K., Fritschi, S. K., Wang, C., Pedersen, N. P., Cirrito, J. R., Mahan, T. E., Finn, M. B., Manis, M., Geerling, J. C., Fuller, P. M., Lucey, B. P., Holtzman, D. M. Tags: Medicine, Diseases reports Source Type: news
A pharmacological master key mechanism that unlocks the selectivity filter gate in K+ channels
Potassium (K+) channels have been evolutionarily tuned for activation by diverse biological stimuli, and pharmacological activation is thought to target these specific gating mechanisms. Here we report a class of negatively charged activators (NCAs) that bypass the specific mechanisms but act as master keys to open K+ channels gated at their selectivity filter (SF), including many two-pore domain K+ (K2P) channels, voltage-gated hERG (human ether-à-go-go–related gene) channels and calcium (Ca2+)–activated big-conductance potassium (BK)–type channels. Functional analysis, x-ray crystallography, and ...
Source: ScienceNOW - February 21, 2019 Category: Science Authors: Schewe, M., Sun, H., Mert, U., Mackenzie, A., Pike, A. C. W., Schulz, F., Constantin, C., Vowinkel, K. S., Conrad, L. J., Kiper, A. K., Gonzalez, W., Musinszki, M., Tegtmeier, M., Pryde, D. C., Belabed, H., Nazare, M., de Groot, B. L., Decher, N., Fakler, Tags: Biochemistry reports Source Type: news
Tunable intrinsic strain in two-dimensional transition metal electrocatalysts
Tuning surface strain is a powerful strategy for tailoring the reactivity of metal catalysts. Traditionally, surface strain is imposed by external stress from a heterogeneous substrate, but the effect is often obscured by interfacial reconstructions and nanocatalyst geometries. Here, we report on a strategy to resolve these problems by exploiting intrinsic surface stresses in two-dimensional transition metal nanosheets. Density functional theory calculations indicate that attractive interactions between surface atoms lead to tensile surface stresses that exert a pressure on the order of 105 atmospheres on the surface atoms...
Source: ScienceNOW - February 21, 2019 Category: Science Authors: Wang, L., Zeng, Z., Gao, W., Maxson, T., Raciti, D., Giroux, M., Pan, X., Wang, C., Greeley, J. Tags: Chemistry reports Source Type: news
The eruptive tempo of Deccan volcanism in relation to the Cretaceous-Paleogene boundary
Late Cretaceous records of environmental change suggest that Deccan Traps (DT) volcanism contributed to the Cretaceous-Paleogene boundary (KPB) ecosystem crisis. However, testing this hypothesis requires identification of the KPB in the DT. We constrain the location of the KPB with high-precision argon-40/argon-39 data to be coincident with changes in the magmatic plumbing system. We also found that the DT did not erupt in three discrete large pulses and that>90% of DT volume erupted in
Source: ScienceNOW - February 21, 2019 Category: Science Authors: Sprain, C. J., Renne, P. R., Vanderkluysen, L., Pande, K., Self, S., Mittal, T. Tags: Geochemistry, Geophysics reports Source Type: news
U-Pb constraints on pulsed eruption of the Deccan Traps across the end-Cretaceous mass extinction
Temporal correlation between some continental flood basalt eruptions and mass extinctions has been proposed to indicate causality, with eruptive volatile release driving environmental degradation and extinction. We tested this model for the Deccan Traps flood basalt province, which, along with the Chicxulub bolide impact, is implicated in the Cretaceous-Paleogene (K-Pg) extinction approximately 66 million years ago. We estimated Deccan eruption rates with uranium-lead (U-Pb) zircon geochronology and resolved four high-volume eruptive periods. According to this model, maximum eruption rates occurred before and after the K-P...
Source: ScienceNOW - February 21, 2019 Category: Science Authors: Schoene, B., Eddy, M. P., Samperton, K. M., Keller, C. B., Keller, G., Adatte, T., Khadri, S. F. R. Tags: Geochemistry, Geophysics reports Source Type: news
Catalytic reductive [4 + 1]-cycloadditions of vinylidenes and dienes
Cycloaddition reactions provide direct and convergent routes to cycloalkanes, making them valuable targets for the development of synthetic methods. Whereas six-membered rings are readily accessible from Diels-Alder reactions, cycloadditions that generate five-membered rings are comparatively limited in scope. Here, we report that dinickel complexes catalyze [4 + 1]-cycloaddition reactions of 1,3-dienes. The C1 partner is a vinylidene equivalent generated from the reductive activation of a 1,1-dichloroalkene in the presence of stoichiometric zinc. Intermolecular and intramolecular variants of the reaction are described, an...
Source: ScienceNOW - February 21, 2019 Category: Science Authors: Zhou, Y.-Y., Uyeda, C. Tags: Chemistry reports Source Type: news
A degenerate Fermi gas of polar molecules
Experimental realization of a quantum degenerate gas of molecules would provide access to a wide range of phenomena in molecular and quantum sciences. However, the very complexity that makes ultracold molecules so enticing has made reaching degeneracy an outstanding experimental challenge over the past decade. We now report the production of a degenerate Fermi gas of ultracold polar molecules of potassium-rubidium. Through coherent adiabatic association in a deeply degenerate mixture of a rubidium Bose-Einstein condensate and a potassium Fermi gas, we produce molecules at temperatures below 0.3 times the Fermi temperature....
Source: ScienceNOW - February 21, 2019 Category: Science Authors: De Marco, L., Valtolina, G., Matsuda, K., Tobias, W. G., Covey, J. P., Ye, J. Tags: Physics reports Source Type: news
Keyhole threshold and morphology in laser melting revealed by ultrahigh-speed x-ray imaging
We used ultrahigh-speed synchrotron x-ray imaging to quantify the phenomenon of vapor depressions (also known as keyholes) during laser melting of metals as practiced in additive manufacturing. Although expected from welding and inferred from postmortem cross sections of fusion zones, the direct visualization of the keyhole morphology and dynamics with high-energy x-rays shows that (i) keyholes are present across the range of power and scanning velocity used in laser powder bed fusion; (ii) there is a well-defined threshold from conduction mode to keyhole based on laser power density; and (iii) the transition follows the s...
Source: ScienceNOW - February 21, 2019 Category: Science Authors: Cunningham, R., Zhao, C., Parab, N., Kantzos, C., Pauza, J., Fezzaa, K., Sun, T., Rollett, A. D. Tags: Physics reports Source Type: news
A Josephson relation for fractionally charged anyons
Anyons occur in two-dimensional electron systems as excitations with fractional charge in the topologically ordered states of the fractional quantum Hall effect (FQHE). Their dynamics are of utmost importance for topological quantum phases and possible decoherence-free quantum information approaches, but observing these dynamics experimentally is challenging. Here, we report on a dynamical property of anyons: the long-predicted Josephson relation fJ = e*V/h for charges e* = e/3 and e/5, where e is the charge of the electron and h is Planck’s constant. The relation manifests itself as marked signatures in the dependen...
Source: ScienceNOW - February 21, 2019 Category: Science Authors: Kapfer, M., Roulleau, P., Santin, M., Farrer, I., Ritchie, D. A., Glattli, D. C. Tags: Physics reports Source Type: news
Scalable and safe synthetic organic electroreduction inspired by Li-ion battery chemistry
Reductive electrosynthesis has faced long-standing challenges in applications to complex organic substrates at scale. Here, we show how decades of research in lithium-ion battery materials, electrolytes, and additives can serve as an inspiration for achieving practically scalable reductive electrosynthetic conditions for the Birch reduction. Specifically, we demonstrate that using a sacrificial anode material (magnesium or aluminum), combined with a cheap, nontoxic, and water-soluble proton source (dimethylurea), and an overcharge protectant inspired by battery technology [tris(pyrrolidino)phosphoramide] can allow for mult...
Source: ScienceNOW - February 21, 2019 Category: Science Authors: Peters, B. K., Rodriguez, K. X., Reisberg, S. H., Beil, S. B., Hickey, D. P., Kawamata, Y., Collins, M., Starr, J., Chen, L., Udyavara, S., Klunder, K., Gorey, T. J., Anderson, S. L., Neurock, M., Minteer, S. D., Baran, P. S. Tags: Chemistry r-articles Source Type: news
Nobel laureate Steven Chu assumes term as AAAS president
Source: ScienceNOW - February 21, 2019 Category: Science Authors: Hoy, A. Q. Tags: a-affairs Source Type: news
Empowering Latina scientists
Source: ScienceNOW - February 21, 2019 Category: Science Authors: Bernal, X. E., Rojas, B., Pinto-E, M. A., Mendoza-Henao, A. M., Herrera-Montes, A., Herrera-Montes, M. I., del Pilar Caceres Franco, A., 254 signatories Tags: letters Source Type: news