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Comment on "Water harvesting from air with metal-organic frameworks powered by natural sunlight"

2017-11-23T10:41:52-08:00

Kim et al. (Reports, 28 April 2017, p. 430) describe a method for harvesting water from air, using a metal-organic framework (MOF) as the adsorbent. The process as described in the paper is, however, inadequate, and the system cannot deliver the claimed amount of liquid water in an arid climate. A modification of the process design and the use of more suitable MOFs may be more likely to achieve the goals targeted by Kim et al.




Response to Comment on "Water harvesting from air with metal-organic frameworks powered by natural sunlight"

2017-11-23T10:41:52-08:00

The Comment by Meunier states that the process we described in our report cannot deliver the claimed amount of liquid water in an arid climate. This statement is not valid because the parameters presented in our study were inappropriately combined to draw misguided conclusions.




Blurring disciplinary boundaries

2017-11-23T10:41:52-08:00




News at a glance

2017-11-23T10:41:52-08:00






















Tougher than hell

2017-11-23T10:41:52-08:00




Into the hot zone

2017-11-23T10:41:52-08:00




Why do Earth's equatorial waves head east?

2017-11-23T10:41:52-08:00




Editing peptide presentation to T cells

2017-11-23T10:41:52-08:00




Viruses hijack a host lncRNA to replicate

2017-11-23T10:41:52-08:00




As the extension, so the twist

2017-11-23T10:41:52-08:00




Enhancing the RNA engineering toolkit

2017-11-23T10:41:52-08:00




The way forward for vector control

2017-11-23T10:41:52-08:00




Channelrhodopsin reveals its dark secrets

2017-11-23T10:41:52-08:00




Quantum interference beyond the fringe

2017-11-23T10:41:52-08:00




Valuing water for sustainable development

2017-11-23T10:41:52-08:00




Common grounds

2017-11-23T10:41:52-08:00




Making the future

2017-11-23T10:41:52-08:00







Mexico's logging threatens butterflies

2017-11-23T10:41:52-08:00




China's new era of ecological civilization

2017-11-23T10:41:52-08:00




NextGen VOICES: Research resolutions

2017-11-23T10:41:52-08:00




Ecuador's sharks face threats from within

2017-11-23T10:41:52-08:00










AAAS Council reminder

2017-11-23T10:41:52-08:00




Brightening nights across the globe

2017-11-23T10:41:52-08:00




The makings of the primate brain

2017-11-23T10:41:52-08:00




Precise transcriptome engineering

2017-11-23T10:41:52-08:00




Behavioral universality across size scales

2017-11-23T10:41:52-08:00




Nailing down the proton magnetic moment

2017-11-23T10:41:52-08:00




In network science, change is good

2017-11-23T10:41:52-08:00




Two snapshots of the TAPBPR-MHC I complex

2017-11-23T10:41:52-08:00







A tale of two receptors

2017-11-23T10:41:52-08:00




The inner workings of an optogenetic tool

2017-11-23T10:41:52-08:00




Tuning diamagnetism with current

2017-11-23T10:41:52-08:00




Purifying ethylene with flexible zeolites

2017-11-23T10:41:52-08:00




Fluid waves with topological origins

2017-11-23T10:41:52-08:00




Getting twisted with metamaterials

2017-11-23T10:41:52-08:00




Packing rubidium into quantum degeneracy

2017-11-23T10:41:52-08:00




Dissolved inorganic carbon fixers revealed

2017-11-23T10:41:52-08:00







Control the vector, beat the disease

2017-11-23T10:41:52-08:00




Host RNA helps promote viral replication

2017-11-23T10:41:52-08:00




A nuclear off-switch for fibrosis

2017-11-23T10:41:52-08:00




Tumor immunity flounders without FIP200

2017-11-23T10:41:52-08:00




Prickly problems of cacti phylogeny

2017-11-23T10:41:52-08:00




Rescuing remyelination

2017-11-23T10:41:52-08:00




Determining the twist of structured light

2017-11-23T10:41:52-08:00




Coactivator starts and stalls

2017-11-23T10:41:52-08:00




Getting help from Mother Nature

2017-11-23T10:41:52-08:00




Mosquito symbiont malaria defense

2017-11-23T10:41:52-08:00




High-symmetry silver

2017-11-23T10:41:52-08:00




RNA editing with CRISPR-Cas13

2017-11-23T10:41:52-08:00

Nucleic acid editing holds promise for treating genetic disease, particularly at the RNA level, where disease-relevant sequences can be rescued to yield functional protein products. Type VI CRISPR-Cas systems contain the programmable single-effector RNA-guided ribonuclease Cas13. We profiled type VI systems in order to engineer a Cas13 ortholog capable of robust knockdown and demonstrated RNA editing by using catalytically inactive Cas13 (dCas13) to direct adenosine-to-inosine deaminase activity by ADAR2 (adenosine deaminase acting on RNA type 2) to transcripts in mammalian cells. This system, referred to as RNA Editing for Programmable A to I Replacement (REPAIR), which has no strict sequence constraints, can be used to edit full-length transcripts containing pathogenic mutations. We further engineered this system to create a high-specificity variant and minimized the system to facilitate viral delivery. REPAIR presents a promising RNA-editing platform with broad applicability for research, therapeutics, and biotechnology.




Molecular and cellular reorganization of neural circuits in the human lineage

2017-11-23T10:41:52-08:00

To better understand the molecular and cellular differences in brain organization between human and nonhuman primates, we performed transcriptome sequencing of 16 regions of adult human, chimpanzee, and macaque brains. Integration with human single-cell transcriptomic data revealed global, regional, and cell-type–specific species expression differences in genes representing distinct functional categories. We validated and further characterized the human specificity of genes enriched in distinct cell types through histological and functional analyses, including rare subpallial-derived interneurons expressing dopamine biosynthesis genes enriched in the human striatum and absent in the nonhuman African ape neocortex. Our integrated analysis of the generated data revealed diverse molecular and cellular features of the phylogenetic reorganization of the human brain across multiple levels, with relevance for brain function and disease.




Structure-property relationships from universal signatures of plasticity in disordered solids

2017-11-23T10:41:52-08:00

When deformed beyond their elastic limits, crystalline solids flow plastically via particle rearrangements localized around structural defects. Disordered solids also flow, but without obvious structural defects. We link structure to plasticity in disordered solids via a microscopic structural quantity, "softness," designed by machine learning to be maximally predictive of rearrangements. Experimental results and computations enabled us to measure the spatial correlations and strain response of softness, as well as two measures of plasticity: the size of rearrangements and the yield strain. All four quantities maintained remarkable commonality in their values for disordered packings of objects ranging from atoms to grains, spanning seven orders of magnitude in diameter and 13 orders of magnitude in elastic modulus. These commonalities link the spatial correlations and strain response of softness to rearrangement size and yield strain, respectively.




Ten-month-old infants infer the value of goals from the costs of actions

2017-11-23T10:41:52-08:00

Infants understand that people pursue goals, but how do they learn which goals people prefer? We tested whether infants solve this problem by inverting a mental model of action planning, trading off the costs of acting against the rewards actions bring. After seeing an agent attain two goals equally often at varying costs, infants expected the agent to prefer the goal it attained through costlier actions. These expectations held across three experiments that conveyed cost through different physical path features (height, width, and incline angle), suggesting that an abstract variable—such as "force," "work," or "effort"—supported infants’ inferences. We modeled infants’ expectations as Bayesian inferences over utility-theoretic calculations, providing a bridge to recent quantitative accounts of action understanding in older children and adults.




The fundamental advantages of temporal networks

2017-11-23T10:41:52-08:00

Most networked systems of scientific interest are characterized by temporal links, meaning the network’s structure changes over time. Link temporality has been shown to hinder many dynamical processes, from information spreading to accessibility, by disrupting network paths. Considering the ubiquity of temporal networks in nature, we ask: Are there any advantages of the networks’ temporality? We use an analytical framework to show that temporal networks can, compared to their static counterparts, reach controllability faster, demand orders of magnitude less control energy, and have control trajectories, that are considerably more compact than those characterizing static networks. Thus, temporality ensures a degree of flexibility that would be unattainable in static networks, enhancing our ability to control them.




Major role of nitrite-oxidizing bacteria in dark ocean carbon fixation

2017-11-23T10:41:52-08:00

Carbon fixation by chemoautotrophic microorganisms in the dark ocean has a major impact on global carbon cycling and ecological relationships in the ocean’s interior, but the relevant taxa and energy sources remain enigmatic. We show evidence that nitrite-oxidizing bacteria affiliated with the Nitrospinae phylum are important in dark ocean chemoautotrophy. Single-cell genomics and community metagenomics revealed that Nitrospinae are the most abundant and globally distributed nitrite-oxidizing bacteria in the ocean. Metaproteomics and metatranscriptomics analyses suggest that nitrite oxidation is the main pathway of energy production in Nitrospinae. Microautoradiography, linked with catalyzed reporter deposition fluorescence in situ hybridization, indicated that Nitrospinae fix 15 to 45% of inorganic carbon in the mesopelagic western North Atlantic. Nitrite oxidation may have a greater impact on the carbon cycle than previously assumed.




An interferon-independent lncRNA promotes viral replication by modulating cellular metabolism

2017-11-23T10:41:52-08:00

Viruses regulate host metabolic networks to improve their survival. The molecules that are responsive to viral infection and regulate such metabolic changes are hardly known, but are essential for understanding viral infection. Here we identify a long noncoding RNA (lncRNA) that is induced by multiple viruses, but not by type I interferon (IFN-I), and facilitates viral replication in mouse and human cells. In vivo deficiency of lncRNA-ACOD1 (a lncRNA identified by its nearest coding gene Acod1, aconitate decarboxylase 1) significantly attenuates viral infection through IFN-I–IRF3 (interferon regulatory factor 3)–independent pathways. Cytoplasmic lncRNA-ACOD1 directly binds the metabolic enzyme glutamic-oxaloacetic transaminase (GOT2) near the substrate niche, enhancing its catalytic activity. Recombinant GOT2 protein and its metabolites could rescue viral replication upon lncRNA-ACOD1 deficiency and increase lethality. This work reveals a feedback mechanism of virus-induced lncRNA-mediated metabolic promotion of viral infection and a potential target for developing broad-acting antiviral therapeutics.




Architecture of eukaryotic mRNA 3'-end processing machinery

2017-11-23T10:41:52-08:00

Newly transcribed eukaryotic precursor messenger RNAs (pre-mRNAs) are processed at their 3' ends by the ~1-megadalton multiprotein cleavage and polyadenylation factor (CPF). CPF cleaves pre-mRNAs, adds a polyadenylate tail, and triggers transcription termination, but it is unclear how its various enzymes are coordinated and assembled. Here, we show that the nuclease, polymerase, and phosphatase activities of yeast CPF are organized into three modules. Using electron cryomicroscopy, we determined a 3.5-angstrom-resolution structure of the ~200-kilodalton polymerase module. This revealed four β propellers, in an assembly markedly similar to those of other protein complexes that bind nucleic acid. Combined with in vitro reconstitution experiments, our data show that the polymerase module brings together factors required for specific and efficient polyadenylation, to help coordinate mRNA 3'-end processing.




Structure of the TAPBPR-MHC I complex defines the mechanism of peptide loading and editing

2017-11-23T10:41:52-08:00

Adaptive immunity is shaped by a selection of peptides presented on major histocompatibility complex class I (MHC I) molecules. The chaperones Tapasin (Tsn) and TAP-binding protein–related (TAPBPR) facilitate MHC I peptide loading and high-affinity epitope selection. Despite the pivotal role of Tsn and TAPBPR in controlling the hierarchical immune response, their catalytic mechanism remains unknown. Here, we present the x-ray structure of the TAPBPR–MHC I complex, which delineates the central step of catalysis. TAPBPR functions as peptide selector by remodeling the MHC I α2-1-helix region, stabilizing the empty binding groove, and inserting a loop into the groove that interferes with peptide binding. The complex explains how mutations in MHC I–specific chaperones cause defects in antigen processing and suggests a unifying mechanism of peptide proofreading.




Crystal structure of a TAPBPR-MHC I complex reveals the mechanism of peptide editing in antigen presentation

2017-11-23T10:41:52-08:00

Central to CD8+ T cell–mediated immunity is the recognition of peptide–major histocompatibility complex class I (p–MHC I) proteins displayed by antigen-presenting cells. Chaperone-mediated loading of high-affinity peptides onto MHC I is a key step in the MHC I antigen presentation pathway. However, the structure of MHC I with a chaperone that facilitates peptide loading has not been determined. We report the crystal structure of MHC I in complex with the peptide editor TAPBPR (TAP-binding protein–related), a tapasin homolog. TAPBPR remodels the peptide-binding groove of MHC I, resulting in the release of low-affinity peptide. Changes include groove relaxation, modifications of key binding pockets, and domain adjustments. This structure captures a peptide-receptive state of MHC I and provides insights into the mechanism of peptide editing by TAPBPR and, by analogy, tapasin.




Control of zeolite framework flexibility and pore topology for separation of ethane and ethylene

2017-11-23T10:41:52-08:00

The discovery of new materials for separating ethylene from ethane by adsorption, instead of using cryogenic distillation, is a key milestone for molecular separations because of the multiple and widely extended uses of these molecules in industry. This technique has the potential to provide tremendous energy savings when compared with the currently used cryogenic distillation process for ethylene produced through steam cracking. Here we describe the synthesis and structural determination of a flexible pure silica zeolite (ITQ-55). This material can kinetically separate ethylene from ethane with an unprecedented selectivity of ~100, owing to its distinctive pore topology with large heart-shaped cages and framework flexibility. Control of such properties extends the boundaries for applicability of zeolites to challenging separations.




Three-dimensional mechanical metamaterials with a twist

2017-11-23T10:41:52-08:00

Rationally designed artificial materials enable mechanical properties that are inaccessible with ordinary materials. Pushing on an ordinary linearly elastic bar can cause it to be deformed in many ways. However, a twist, the counterpart of optical activity in the static case, is strictly zero. The unavailability of this degree of freedom hinders applications in terms of mode conversion and the realization of advanced mechanical designs using coordinate transformations. Here, we aim at realizing microstructured three-dimensional elastic chiral mechanical metamaterials that overcome this limitation. On overall millimeter-sized samples, we measure twists per axial strain exceeding 2°/%. Scaling up the number of unit cells for fixed sample dimensions, the twist is robust due to metamaterial stiffening, indicating a characteristic length scale and bringing the aforementioned applications into reach.




Topological origin of equatorial waves

2017-11-23T10:41:52-08:00

Topology sheds new light on the emergence of unidirectional edge waves in a variety of physical systems, from condensed matter to artificial lattices. Waves observed in geophysical flows are also robust to perturbations, which suggests a role for topology. We show a topological origin for two well-known equatorially trapped waves, the Kelvin and Yanai modes, owing to the breaking of time-reversal symmetry by Earth’s rotation. The nontrivial structure of the bulk Poincaré wave modes encoded through the first Chern number of value 2 guarantees the existence of these waves. This invariant demonstrates that ocean and atmospheric waves share fundamental properties with topological insulators and that topology plays an unexpected role in Earth’s climate system.




Creation of a Bose-condensed gas of 87Rb by laser cooling

2017-11-23T10:41:52-08:00

Protocols for attaining quantum degeneracy in atomic gases almost exclusively rely on evaporative cooling, a time-consuming final step associated with substantial atom loss. We demonstrate direct laser cooling of a gas of rubidium-87 (87Rb) atoms to quantum degeneracy. The method is fast and induces little atom loss. The atoms are trapped in a two-dimensional optical lattice that enables cycles of compression to increase the density, followed by Raman sideband cooling to decrease the temperature. From a starting number of 2000 atoms, 1400 atoms reach quantum degeneracy in 300 milliseconds, as confirmed by a bimodal velocity distribution. The method should be broadly applicable to many bosonic and fermionic species and to systems where evaporative cooling is not possible.




Double-trap measurement of the proton magnetic moment at 0.3 parts per billion precision

2017-11-23T10:41:52-08:00

Precise knowledge of the fundamental properties of the proton is essential for our understanding of atomic structure as well as for precise tests of fundamental symmetries. We report on a direct high-precision measurement of the magnetic moment μp of the proton in units of the nuclear magneton μN. The result, μp = 2.79284734462 (±0.00000000082) μN, has a fractional precision of 0.3 parts per billion, improves the previous best measurement by a factor of 11, and is consistent with the currently accepted value. This was achieved with the use of an optimized double–Penning trap technique. Provided a similar measurement of the antiproton magnetic moment can be performed, this result will enable a test of the fundamental symmetry between matter and antimatter in the baryonic sector at the 10–10 level.




Current-induced strong diamagnetism in the Mott insulator Ca2RuO4

2017-11-23T10:41:52-08:00

Mott insulators can host a surprisingly diverse set of quantum phenomena when their frozen electrons are perturbed by various stimuli. Superconductivity, metal-insulator transition, and colossal magnetoresistance induced by element substitution, pressure, and magnetic field are prominent examples. Here we report strong diamagnetism in the Mott insulator calcium ruthenate (Ca2RuO4) induced by dc electric current. The application of a current density of merely 1 ampere per centimeter squared induces diamagnetism stronger than that in other nonsuperconducting materials. This change is coincident with changes in the transport properties as the system becomes semimetallic. These findings suggest that dc current may be a means to control the properties of materials in the vicinity of a Mott insulating transition.




New Products

2017-11-23T10:41:52-08:00










Learning to be a mentor

2017-11-23T10:41:52-08:00




Structural insights into ion conduction by channelrhodopsin 2

2017-11-23T10:41:52-08:00

The light-gated ion channel channelrhodopsin 2 (ChR2) from Chlamydomonas reinhardtii is a major optogenetic tool. Photon absorption starts a well-characterized photocycle, but the structural basis for the regulation of channel opening remains unclear. We present high-resolution structures of ChR2 and the C128T mutant, which has a markedly increased open-state lifetime. The structure reveals two cavities on the intracellular side and two cavities on the extracellular side. They are connected by extended hydrogen-bonding networks involving water molecules and side-chain residues. Central is the retinal Schiff base that controls and synchronizes three gates that separate the cavities. Separate from this network is the DC gate that comprises a water-mediated bond between C128 and D156 and interacts directly with the retinal Schiff base. Comparison with the C128T structure reveals a direct connection of the DC gate to the central gate and suggests how the gating mechanism is affected by subtle tuning of the Schiff base’s interactions.