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Dragomir Milovanovic, Yumei Wu, Xin Bian, Pietro De Camilli
Neurotransmitter containing synaptic vesicles (SVs) form tight clusters at synapses. These clusters act as a reservoir from which SVs are drawn for exocytosis during sustained activity. Several components associated with synaptic vesicles likely to help forming such clusters have been reported, including synapsin. Here we found that synapsin can form a distinct liquid phase in an aqueous environment. Other scaffolding proteins could co-assemble into this condensate, but were not necessary for its formation...
July 5, 2018: Science
Joon Sang Kang, Man Li, Huan Wu, Huuduy Nguyen, Yongjie Hu
Improving thermal management of small scale devices requires developing materials with high thermal conductivities. The semiconductor boron arsenide (BAs) is an attractive target due to ab initio calculation indicating single crystals have an ultrahigh thermal conductivity. We synthesized BAs single crystals with undetectable defects, and measured a room temperature thermal conductivity of 1300 W/mK. Our spectroscopy study in conjunction with atomistic theory reveals that the unique band structure of BAs allows for very long phonon mean free paths and strong high-order anharmonicity through the four-phonon process...
July 5, 2018: Science
Fei Tian, Bai Song, Xi Chen, Navaneetha K Ravichandran, Yinchuan Lv, Ke Chen, Sean Sullivan, Jaehyun Kim, Yuanyuan Zhou, Te-Huan Liu, Miguel Goni, Zhiwei Ding, Jingying Sun, Geethal Amila Gamage Udalamatta Gamage, Haoran Sun, Hamidreza Ziyaee, Shuyuan Huyan, Liangzi Deng, Jianshi Zhou, Aaron J Schmidt, Shuo Chen, Ching-Wu Chu, Pinshane Y Huang, David Broido, Li Shi, Gang Chen, Zhifeng Ren
Conventional theory predicts that ultrahigh lattice thermal conductivity can only occur in crystals composed of strongly-bonded light elements, and that it is limited by anharmonic three-phonon processes. We report experimental evidence that is a departure from these long-held criteria. We measured a local room-temperature thermal conductivity exceeding 1000 W m-1 K-1 and an average bulk value reaching 900 W m-1 K-1 in bulk boron arsenide (BAs) crystals, where boron and arsenic are light and heavy elements, respectively...
July 5, 2018: Science
Sheng Li, Qiye Zheng, Yinchuan Lv, Xiaoyuan Liu, Xiqu Wang, Pinshane Y Huang, David G Cahill, Bing Lv
The high density of heat generated in power electronics and optoelectronic devices is a critical bottleneck in their application. New, high thermally-conducting materials are needed to effectively dissipate heat and thereby enable enhanced performance of power controls, solid-state lighting, communication, and security systems. We report our experimental discovery of high thermal conductivity of 1000 ± 90 W/m/K at room temperature in cubic boron arsenide (BAs) grown through modified chemical vapor transport technique...
July 5, 2018: Science
A Mura, A Adriani, J E P Connerney, S Bolton, F Altieri, F Bagenal, B Bonfond, B M Dinelli, J-C Gérard, T Greathouse, D Grodent, S Levin, B Mauk, M L Moriconi, J Saur, J H Waite, M Amoroso, A Cicchetti, F Fabiano, G Filacchione, D Grassi, A Migliorini, R Noschese, A Olivieri, G Piccioni, C Plainaki, G Sindoni, R Sordini, F Tosi, D Turrini
Jupiter's aurorae are produced in its upper atmosphere when incoming high-energy electrons precipitate along the planet's magnetic field lines. A northern and a southern main auroral oval are visible, surrounded by small emission features associated with the Galilean moons. We present infrared observations, obtained with the Juno spacecraft, showing that in the case of Io, this emission exhibits a swirling pattern that is similar in appearance to a von Kármán vortex street. Well downstream of the main auroral spots the extended tail is split in two...
July 5, 2018: Science
Mingjian Du, Zhijian J Chen
The binding of DNA to cyclic GMP-AMP synthase (cGAS) leads to the production of the secondary messenger cyclic GMP-AMP (cGAMP), which activates innate immune responses. Here, we show that DNA binding to cGAS robustly induced the formation of liquidlike droplets in which cGAS was activated. The disordered and positively charged cGAS N terminus enhanced cGAS-DNA phase separation by increasing the valencies of DNA binding. Long DNA was more efficient in promoting cGAS liquid phase separation and cGAS enzyme activity than short DNA...
July 5, 2018: Science
L Huber, R Suzuki, T Krüger, E Frey, A R Bausch
Active systems can produce a far greater variety of ordered patterns than conventional equilibrium systems. Especially, transitions between disorder and either polar- or nematically-ordered phases have been predicted and observed in two-dimensional active systems. However, coexistence between phases of different types of order has not been reported. We demonstrate the emergence of dynamic coexistence of ordered states with fluctuating nematic and polar symmetry in an actomyosin motility assay. Combining experiments with agent-based simulations, we identify sufficiently weak interactions that lack a clear alignment symmetry as a prerequisite for coexistence...
June 28, 2018: Science
Jiho Yoo, Mengyu Wu, Ying Yin, Mark A Herzik, Gabriel C Lander, Seok-Yong Lee
Calcium transport plays an important role in regulating mitochondrial physiology and pathophysiology. The mitochondrial calcium uniporter (MCU) is a calcium-selective ion channel that is the primary mediator for calcium uptake into the mitochondrial matrix. Here we present the cryo-electron microscopy structure of the full-length MCU from Neurospora crassa to an overall resolution of ~3.7 Å. Our structure reveals a tetrameric architecture, with the soluble and transmembrane domains adopting different symmetric arrangements within the channel...
June 28, 2018: Science
Sung Joon Ahn, Pilkyung Moon, Tae-Hoon Kim, Hyun-Woo Kim, Ha-Chul Shin, Eun Hye Kim, Hyun Woo Cha, Se-Jong Kahng, Philip Kim, Mikito Koshino, Young-Woo Son, Cheol-Woong Yang, Joung Real Ahn
Quantum states of quasiparticles in solids are dictated by symmetry. We experimentally demonstrate Dirac electrons in a two-dimensional quasicrystal without translational symmetry. A dodecagonal quasicrystalline order was realized by epitaxial growth of twisted bilayer graphene rotated exactly 30°. The graphene quasicrystal was grown up to a millimeter scale on an SiC (0001) surface while maintaining the single rotation angle over an entire sample and was successfully isolated from a substrate, demonstrating its structural and chemical stability under ambient conditions...
June 28, 2018: Science
Xin Gong, Hongwu Qian, Pingping Cao, Xin Zhao, Qiang Zhou, Jianlin Lei, Nieng Yan
The Hedgehog (Hh) pathway involved in development and regeneration is activated by the extracellular binding of Hh to the membrane receptor Patched (Ptch). We report the cryo-EM structures of human Ptch1 alone and in complex with the N-terminal domain of human Sonic hedgehog (ShhN) at resolutions of 3.9 Å and 3.6 Å, respectively. Ptch1 comprises two interacting extracellular domains ECD1 and ECD2 and twelve transmembrane segments (TMs), with TMs 2-6 constituting the sterol-sensing domain (SSD). Two steroid-shaped densities are resolved in both structures, one enclosed by ECD1/2, and the other on the membrane-facing cavity of SSD...
June 28, 2018: Science
George H Allen, Tamlin M Pavelsky
The turbulent surfaces of rivers and streams are natural hotspots of biogeochemical exchange with the atmosphere. At the global scale, the total river-atmosphere flux of trace gasses such as CO2 depends on the proportion of Earth's surface that is covered by the fluvial network, yet the total surface area of rivers and streams is poorly constrained. We used a global database of planform river hydromorphology and a statistical approach to show that global river and stream surface area at mean annual discharge is 773,000 ± 79,000 km2 (0...
June 28, 2018: Science
Won-Ki Cho, Jan-Hendrik Spille, Micca Hecht, Choongman Lee, Charles Li, Valentin Grube, Ibrahim I Cisse
Models of gene control have emerged from genetic and biochemical studies, with limited consideration of the spatial organization and dynamics of key components in living cells. Here we used live cell super-resolution and light sheet imaging to study the organization and dynamics of the Mediator coactivator and RNA polymerase II (Pol II) directly. Mediator and Pol II each form small transient and large stable clusters in living embryonic stem cells. Mediator and Pol II are colocalized in the stable clusters, which associate with chromatin, have properties of phase-separated condensates, and are sensitive to transcriptional inhibitors...
June 21, 2018: Science
Austin M Evans, Lucas R Parent, Nathan C Flanders, Ryan P Bisbey, Edon Vitaku, Matthew S Kirschner, Richard D Schaller, Lin X Chen, Nathan C Gianneschi, William R Dichtel
Polymerizing monomers into periodic two-dimensional (2D) networks provides structurally precise, layered macromolecular sheets that exhibit desirable mechanical, optoelectrotronic, and molecular transport properties. 2D covalent organic frameworks (COFs) offer broad monomer scope but are generally isolated as powders comprised of aggregated nanometer-scale crystallites. Here we control 2D COF formation using a two-step procedure, in which monomers are added slowly to preformed nanoparticle seeds. The resulting 2D COFs are isolated as single-crystalline, micron-sized particles...
June 21, 2018: Science
Ramón A Alvarez, Daniel Zavala-Araiza, David R Lyon, David T Allen, Zachary R Barkley, Adam R Brandt, Kenneth J Davis, Scott C Herndon, Daniel J Jacob, Anna Karion, Eric A Kort, Brian K Lamb, Thomas Lauvaux, Joannes D Maasakkers, Anthony J Marchese, Mark Omara, Stephen W Pacala, Jeff Peischl, Allen L Robinson, Paul B Shepson, Colm Sweeney, Amy Townsend-Small, Steven C Wofsy, Steven P Hamburg
Methane emissions from the U.S. oil and natural gas supply chain were estimated using ground-based, facility-scale measurements and validated with aircraft observations in areas accounting for ~30% of U.S. gas production. When scaled up nationally, our facility-based estimate of 2015 supply chain emissions is 13 ± 2 Tg/y, equivalent to 2.3% of gross U.S. gas production. This value is ~60% higher than the U.S. EPA inventory estimate, likely because existing inventory methods miss emissions released during abnormal operating conditions...
June 21, 2018: Science
Benjamin R Sabari, Alessandra Dall'Agnese, Ann Boija, Isaac A Klein, Eliot L Coffey, Krishna Shrinivas, Brian J Abraham, Nancy M Hannett, Alicia V Zamudio, John C Manteiga, Charles H Li, Yang E Guo, Daniel S Day, Jurian Schuijers, Eliza Vasile, Sohail Malik, Denes Hnisz, Tong Ihn Lee, Ibrahim I Cisse, Robert G Roeder, Phillip A Sharp, Arup K Chakraborty, Richard A Young
Super-enhancers (SEs) are clusters of enhancers that cooperatively assemble a high density of transcriptional apparatus to drive robust expression of genes with prominent roles in cell identity. Here, we demonstrate that the SE-enriched transcriptional coactivators BRD4 and MED1 form nuclear puncta at SEs that exhibit properties of liquid-like condensates and are disrupted by chemicals that perturb condensates. The intrinsically disordered regions (IDRs) of BRD4 and MED1 can form phase-separated droplets and MED1-IDR droplets can compartmentalize and concentrate transcription apparatus from nuclear extracts...
June 21, 2018: Science
Shasha Chong, Claire Dugast-Darzacq, Zhe Liu, Peng Dong, Gina M Dailey, Claudia Cattoglio, Alec Heckert, Sambashiva Banala, Luke Lavis, Xavier Darzacq, Robert Tjian
Many eukaryotic transcription factors (TFs) contain intrinsically disordered low-complexity domains (LCDs), but how they drive transactivation remains unclear. Here, live-cell single-molecule imaging reveals that TF-LCDs form local high-concentration interaction hubs at synthetic and endogenous genomic loci. TF-LCD hubs stabilize DNA binding, recruit RNA polymerase II (Pol II), and activate transcription. LCD-LCD interactions within hubs are highly dynamic, display selectivity with binding partners, and are differentially sensitive to disruption by hexanediols...
June 21, 2018: Science
Xiao Wang, William E Allen, Matthew A Wright, Emily L Sylwestrak, Nikolay Samusik, Sam Vesuna, Kathryn Evans, Cindy Liu, Charu Ramakrishnan, Jia Liu, Garry P Nolan, Felice-Alessio Bava, Karl Deisseroth
Retrieving high-content gene-expression information while retaining 3D positional anatomy at cellular resolution has been difficult, limiting integrative understanding of structure and function in complex biological tissues. Here we develop and apply a technology for 3D intact-tissue RNA sequencing, termed STARmap (Spatially-resolved Transcript Amplicon Readout Mapping), which integrates hydrogel-tissue chemistry, targeted signal amplification, and in situ sequencing. The capabilities of STARmap were tested by mapping 160 to 1,020 genes simultaneously in sections of mouse brain at single-cell resolution with high efficiency, accuracy and reproducibility...
June 21, 2018: Science
S Mattila, M Pérez-Torres, A Efstathiou, P Mimica, M Fraser, E Kankare, A Alberdi, M Á Aloy, T Heikkilä, P G Jonker, P Lundqvist, I Martí-Vidal, W P S Meikle, C Romero-Cañizales, S J Smartt, S Tsygankov, E Varenius, A Alonso-Herrero, M Bondi, C Fransson, R Herrero-Illana, T Kangas, R Kotak, N Ramírez-Olivencia, P Väisänen, R J Beswick, D L Clements, R Greimel, J Harmanen, J Kotilainen, K Nandra, T Reynolds, S Ryder, N A Walton, K Wiik, G Östlin
Tidal disruption events (TDEs) are transient flares produced when a star is ripped apart by the gravitational field of a supermassive black hole (SMBH). We have observed a transient source in the western nucleus of the merging galaxy pair Arp 299 that radiated >1.5 × 1052 erg in the infrared and radio but was not luminous at optical or x-ray wavelengths. We interpret this as a TDE with much of its emission reradiated at infrared wavelengths by dust. Efficient reprocessing by dense gas and dust may explain the difference between theoretical predictions and observed luminosities of TDEs...
June 14, 2018: Science
Chenguang Qiu, Fei Liu, Lin Xu, Bing Deng, Mengmeng Xiao, Jia Si, Li Lin, Zhiyong Zhang, Jian Wang, Hong Guo, Hailin Peng, Lian-Mao Peng
An efficient way to reduce the power is to lower the supply voltage VDD , but this voltage is restricted by the 60 millivolts per decade thermionic limit of subthreshold swing (SS) in field-effect transistors (FETs). We show that a graphene Dirac source (DS) with a much narrower electron density distribution around the Fermi level than that of conventional FETs can lower SS. A DS-FET with a carbon nanotube channel provided an average SS of 40 millivolt per decade over four decades of current at room temperature and high device current I60 of up to 40 microampere per micrometer at 60 millivolts per decade...
June 14, 2018: Science
Nitzan Gonen, Chris R Futtner, Sophie Wood, S Alexandra Garcia-Moreno, Isabella M Salamone, Shiela C Samson, Ryohei Sekido, Francis Poulat, Danielle M Maatouk, Robin Lovell-Badge
Cell fate decisions require appropriate regulation of key genes. Sox9 , a direct target of SRY, is pivotal in mammalian sex determination. In vivo high-throughput chromatin accessibility techniques, transgenic assays, and genome editing revealed several novel gonadal regulatory elements in the 2-megabase gene desert upstream of Sox9 Although others are redundant, Enh13, a 557-base pair element located 565 kilobases 5', is essential to initiate mouse testis development; its deletion giving XY females with Sox9 transcript levels equivalent to XX gonads...
June 14, 2018: Science
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