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Science Advances

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https://www.readbyqxmd.com/read/28808686/a-conformational-checkpoint-between-dna-binding-and-cleavage-by-crispr-cas9
#1
Yavuz S Dagdas, Janice S Chen, Samuel H Sternberg, Jennifer A Doudna, Ahmet Yildiz
The Cas9 endonuclease is widely used for genome engineering applications by programming its single-guide RNA, and ongoing work is aimed at improving the accuracy and efficiency of DNA targeting. DNA cleavage of Cas9 is controlled by the conformational state of the HNH nuclease domain, but the mechanism that governs HNH activation at on-target DNA while reducing cleavage activity at off-target sites remains poorly understood. Using single-molecule Förster resonance energy transfer, we identified an intermediate state of Streptococcus pyogenes Cas9, representing a conformational checkpoint between DNA binding and cleavage...
August 2017: Science Advances
https://www.readbyqxmd.com/read/28808685/structure-of-a-1-5-mda-adhesin-that-binds-its-antarctic-bacterium-to-diatoms-and-ice
#2
Shuaiqi Guo, Corey A Stevens, Tyler D R Vance, Luuk L C Olijve, Laurie A Graham, Robert L Campbell, Saeed R Yazdi, Carlos Escobedo, Maya Bar-Dolev, Victor Yashunsky, Ido Braslavsky, David N Langelaan, Steven P Smith, John S Allingham, Ilja K Voets, Peter L Davies
Bacterial adhesins are modular cell-surface proteins that mediate adherence to other cells, surfaces, and ligands. The Antarctic bacterium Marinomonas primoryensis uses a 1.5-MDa adhesin comprising over 130 domains to position it on ice at the top of the water column for better access to oxygen and nutrients. We have reconstructed this 0.6-μm-long adhesin using a "dissect and build" structural biology approach and have established complementary roles for its five distinct regions. Domains in region I (RI) tether the adhesin to the type I secretion machinery in the periplasm of the bacterium and pass it through the outer membrane...
August 2017: Science Advances
https://www.readbyqxmd.com/read/28808684/constraining-the-rate-of-oceanic-deoxygenation-leading-up-to-a-cretaceous-oceanic-anoxic-event-oae-2-94-ma
#3
Chadlin M Ostrander, Jeremy D Owens, Sune G Nielsen
The rates of marine deoxygenation leading to Cretaceous Oceanic Anoxic Events are poorly recognized and constrained. If increases in primary productivity are the primary driver of these episodes, progressive oxygen loss from global waters should predate enhanced carbon burial in underlying sediments-the diagnostic Oceanic Anoxic Event relic. Thallium isotope analysis of organic-rich black shales from Demerara Rise across Oceanic Anoxic Event 2 reveals evidence of expanded sediment-water interface deoxygenation ~43 ± 11 thousand years before the globally recognized carbon cycle perturbation...
August 2017: Science Advances
https://www.readbyqxmd.com/read/28808683/in-situ-generation-of-n-unsubstituted-imines-from-alkyl-azides-and-their-applications-for-imine-transfer-via-copper-catalysis
#4
Lu Hu, Yahu A Liu, Xuebin Liao
Although azides have been widely used in nitrene transfer reactions, in situ generation of N-H imines from azides for downstream transformations has rarely been explored. We report copper-mediated formation of N-unsubstituted aliphatic imines from easily available aliphatic azides using a customized phenanthroline-based ligand (L1*). Through trapping in situ-generated N-H imines, multisubstituted pyridines or indoles were readily synthesized. (13)C-labeled azide was used as part of an isotope labeling study, which suggests that the construction of pyridine derivatives involves a three-component dehydrogenative condensation...
August 2017: Science Advances
https://www.readbyqxmd.com/read/28808682/effects-of-population-dispersal-on-regional-signaling-networks-an-example-from-northern-iroquoia
#5
John P Hart, Jennifer Birch, Christian Gates St-Pierre
The dispersal of Iroquoian groups from St. Lawrence River valley during the 15th and 16th centuries A.D. has been a source of archaeological inquiry for decades. Social network analysis presented here indicates that sites from Jefferson County, New York at the head of the St. Lawrence River controlled interactions within regional social signaling networks during the 15th century A.D. Measures indicate that Jefferson County sites were in brokerage liaison positions between sites in New York and Ontario. In the network for the subsequent century, to which no Jefferson County sites are assigned, no single group took the place of Jefferson County in controlling network flow...
August 2017: Science Advances
https://www.readbyqxmd.com/read/28808681/comment-on-how-will-induced-seismicity-in-oklahoma-respond-to-decreased-saltwater-injection-rates-by-c-langenbruch-and-m-d-zoback
#6
Thomas H W Goebel, Jacob I Walter, Kyle Murray, Emily E Brodsky
The state of Oklahoma has experienced an unprecedented increase in earthquake activity since 2009, likely driven by large-scale wastewater injection operations. Statewide injection rates peaked in early 2015 and steadily decreased thereafter, approximately coinciding with collapsing oil prices and regulatory action. If seismic activity is primarily driven by fluid injection, a noticeable seismogenic response to the decrease in injection rates is expected. Langenbruch and Zoback suggest that "the probability of potentially damaging larger events, should significantly decrease by the end of 2016 and approach historic levels within a few years...
August 2017: Science Advances
https://www.readbyqxmd.com/read/28808680/early-formation-of-planetary-building-blocks-inferred-from-pb-isotopic-ages-of-chondrules
#7
Jean Bollard, James N Connelly, Martin J Whitehouse, Emily A Pringle, Lydie Bonal, Jes K Jørgensen, Åke Nordlund, Frédéric Moynier, Martin Bizzarro
The most abundant components of primitive meteorites (chondrites) are millimeter-sized glassy spherical chondrules formed by transient melting events in the solar protoplanetary disk. Using Pb-Pb dates of 22 individual chondrules, we show that primary production of chondrules in the early solar system was restricted to the first million years after the formation of the Sun and that these existing chondrules were recycled for the remaining lifetime of the protoplanetary disk. This finding is consistent with a primary chondrule formation episode during the early high-mass accretion phase of the protoplanetary disk that transitions into a longer period of chondrule reworking...
August 2017: Science Advances
https://www.readbyqxmd.com/read/28808679/a-two-billion-year-history-for-the-lunar-dynamo
#8
Sonia M Tikoo, Benjamin P Weiss, David L Shuster, Clément Suavet, Huapei Wang, Timothy L Grove
Magnetic studies of lunar rocks indicate that the Moon generated a core dynamo with surface field intensities of ~20 to 110 μT between at least 4.25 and 3.56 billion years ago (Ga). The field subsequently declined to <~4 μT by 3.19 Ga, but it has been unclear whether the dynamo had terminated by this time or just greatly weakened in intensity. We present analyses that demonstrate that the melt glass matrix of a young regolith breccia was magnetized in a ~5 ± 2 μT dynamo field at ~1 to ~2.5 Ga. These data extend the known lifetime of the lunar dynamo by at least 1 billion years...
August 2017: Science Advances
https://www.readbyqxmd.com/read/28808678/interest-in-stem-is-contagious-for-students-in-biology-chemistry-and-physics-classes
#9
Zahra Hazari, Geoff Potvin, Jennifer D Cribbs, Allison Godwin, Tyler D Scott, Leidy Klotz
We report on a study of the effect of peers' interest in high school biology, chemistry, and physics classes on students' STEM (science, technology, engineering, and mathematics)-related career intentions and course achievement. We define an interest quorum as a science class where students perceive a high level of interest for the subject matter from their classmates. We hypothesized that students who experience such an interest quorum are more likely to choose STEM careers. Using data from a national survey study of students' experiences in high school science, we compared the effect of five levels of peer interest reported in biology, chemistry, and physics courses on students' STEM career intentions...
August 2017: Science Advances
https://www.readbyqxmd.com/read/28798962/structural-pathway-of-regulated-substrate-transfer-and-threading-through-an-hsp100-disaggregase
#10
Célia Deville, Marta Carroni, Kamila B Franke, Maya Topf, Bernd Bukau, Axel Mogk, Helen R Saibil
Refolding aggregated proteins is essential in combating cellular proteotoxic stress. Together with Hsp70, Hsp100 chaperones, including Escherichia coli ClpB, form a powerful disaggregation machine that threads aggregated polypeptides through the central pore of tandem adenosine triphosphatase (ATPase) rings. To visualize protein disaggregation, we determined cryo-electron microscopy structures of inactive and substrate-bound ClpB in the presence of adenosine 5'-O-(3-thiotriphosphate), revealing closed AAA+ rings with a pronounced seam...
August 2017: Science Advances
https://www.readbyqxmd.com/read/28798961/leaking-privacy-and-shadow-profiles-in-online-social-networks
#11
David Garcia
Social interaction and data integration in the digital society can affect the control that individuals have on their privacy. Social networking sites can access data from other services, including user contact lists where nonusers are listed too. Although most research on online privacy has focused on inference of personal information of users, this data integration poses the question of whether it is possible to predict personal information of nonusers. This article tests the shadow profile hypothesis, which postulates that the data given by the users of an online service predict personal information of nonusers...
August 2017: Science Advances
https://www.readbyqxmd.com/read/28798960/sequence-encoded-colloidal-origami-and-microbot-assemblies-from-patchy-magnetic-cubes
#12
Koohee Han, C Wyatt Shields, Nidhi M Diwakar, Bhuvnesh Bharti, Gabriel P López, Orlin D Velev
Colloidal-scale assemblies that reconfigure on demand may serve as the next generation of soft "microbots," artificial muscles, and other biomimetic devices. This requires the precise arrangement of particles into structures that are preprogrammed to reversibly change shape when actuated by external fields. The design and making of colloidal-scale assemblies with encoded directional particle-particle interactions remain a major challenge. We show how assemblies of metallodielectric patchy microcubes can be engineered to store energy through magnetic polarization and release it on demand by microscale reconfiguration...
August 2017: Science Advances
https://www.readbyqxmd.com/read/28798959/confining-metal-halide-perovskites-in-nanoporous-thin-films
#13
Stepan Demchyshyn, Janina Melanie Roemer, Heiko Groiß, Herwig Heilbrunner, Christoph Ulbricht, Dogukan Apaydin, Anton Böhm, Uta Rütt, Florian Bertram, Günter Hesser, Markus Clark Scharber, Niyazi Serdar Sariciftci, Bert Nickel, Siegfried Bauer, Eric Daniel Głowacki, Martin Kaltenbrunner
Controlling the size and shape of semiconducting nanocrystals advances nanoelectronics and photonics. Quantum-confined, inexpensive, solution-derived metal halide perovskites offer narrowband, color-pure emitters as integral parts of next-generation displays and optoelectronic devices. We use nanoporous silicon and alumina thin films as templates for the growth of perovskite nanocrystallites directly within device-relevant architectures without the use of colloidal stabilization. We find significantly blue-shifted photoluminescence emission by reducing the pore size; normally infrared-emitting materials become visibly red, and green-emitting materials become cyan and blue...
August 2017: Science Advances
https://www.readbyqxmd.com/read/28798958/biofunctionalized-conductive-polymers-enable-efficient-co2-electroreduction
#14
Halime Coskun, Abdalaziz Aljabour, Phil De Luna, Dominik Farka, Theresia Greunz, David Stifter, Mahmut Kus, Xueli Zheng, Min Liu, Achim W Hassel, Wolfgang Schöfberger, Edward H Sargent, Niyazi Serdar Sariciftci, Philipp Stadler
Selective electrocatalysts are urgently needed for carbon dioxide (CO2) reduction to replace fossil fuels with renewable fuels, thereby closing the carbon cycle. To date, noble metals have achieved the best performance in energy yield and faradaic efficiency and have recently reached impressive electrical-to-chemical power conversion efficiencies. However, the scarcity of precious metals makes the search for scalable, metal-free, CO2 reduction reaction (CO2RR) catalysts all the more important. We report an all-organic, that is, metal-free, electrocatalyst that achieves impressive performance comparable to that of best-in-class Ag electrocatalysts...
August 2017: Science Advances
https://www.readbyqxmd.com/read/28798957/holographic-deep-learning-for-rapid-optical-screening-of-anthrax-spores
#15
YoungJu Jo, Sangjin Park, JaeHwang Jung, Jonghee Yoon, Hosung Joo, Min-Hyeok Kim, Suk-Jo Kang, Myung Chul Choi, Sang Yup Lee, YongKeun Park
Establishing early warning systems for anthrax attacks is crucial in biodefense. Despite numerous studies for decades, the limited sensitivity of conventional biochemical methods essentially requires preprocessing steps and thus has limitations to be used in realistic settings of biological warfare. We present an optical method for rapid and label-free screening of Bacillus anthracis spores through the synergistic application of holographic microscopy and deep learning. A deep convolutional neural network is designed to classify holographic images of unlabeled living cells...
August 2017: Science Advances
https://www.readbyqxmd.com/read/28798956/heat-conduction-tuning-by-wave-nature-of-phonons
#16
Jeremie Maire, Roman Anufriev, Ryoto Yanagisawa, Aymeric Ramiere, Sebastian Volz, Masahiro Nomura
The world communicates to our senses of vision, hearing, and touch in the language of waves, because light, sound, and even heat essentially consist of microscopic vibrations of different media. The wave nature of light and sound has been extensively investigated over the past century and is now widely used in modern technology. However, the wave nature of heat has been the subject of mostly theoretical studies because its experimental demonstration, let alone practical use, remains challenging due to its extremely short wavelengths...
August 2017: Science Advances
https://www.readbyqxmd.com/read/28782042/polycomb-repressive-complex-1-modifies-transcription-of-active-genes
#17
Michelle Pherson, Ziva Misulovin, Maria Gause, Kathie Mihindukulasuriya, Amanda Swain, Dale Dorsett
This study examines the role of Polycomb repressive complex 1 (PRC1) at active genes. The PRC1 and PRC2 complexes are crucial for epigenetic silencing during development of an organism. They are recruited to Polycomb response elements (PREs) and establish silenced domains over several kilobases. Recent studies show that PRC1 is also directly recruited to active genes by the cohesin complex. Cohesin participates broadly in control of gene transcription, but it is unknown whether cohesin-recruited PRC1 also plays a role in transcriptional control of active genes...
August 2017: Science Advances
https://www.readbyqxmd.com/read/28782041/a-bimodal-activation-mechanism-underlies-scorpion-toxin-induced-pain
#18
Shilong Yang, Fan Yang, Bei Zhang, Bo Hyun Lee, Bowen Li, Lei Luo, Jie Zheng, Ren Lai
Venomous animals use peptide toxins for hunting and self-defense. To achieve these goals, toxins need to bind to their targets with high affinity due to the small amount that a single bite or sting can deliver. The scorpion toxin BmP01 is linked to sting-induced excruciating pain; however, the reported minimum concentrations for activating TRPV1 channel or inhibiting voltage-gated potassium (Kv) channels (both in the micromolar range) appear too high to be biologically relevant. We show that the effective concentration of BmP01 is highly pH-dependent-it increases by about 10-fold in inhibiting Kv channels upon a 1-U drop in pH but decreases more than 100-fold in activating TRPV1...
August 2017: Science Advances
https://www.readbyqxmd.com/read/28782040/stress-drops-of-induced-and-tectonic-earthquakes-in-the-central-united-states-are-indistinguishable
#19
Yihe Huang, William L Ellsworth, Gregory C Beroza
Induced earthquakes currently pose a significant hazard in the central United States, but there is considerable uncertainty about the severity of their ground motions. We measure stress drops of 39 moderate-magnitude induced and tectonic earthquakes in the central United States and eastern North America. Induced earthquakes, more than half of which are shallower than 5 km, show a comparable median stress drop to tectonic earthquakes in the central United States that are dominantly strike-slip but a lower median stress drop than that of tectonic earthquakes in the eastern North America that are dominantly reverse-faulting...
August 2017: Science Advances
https://www.readbyqxmd.com/read/28782039/control-of-nacre-biomineralization-by-pif80-in-pearl-oyster
#20
So Yeong Bahn, Byung Hoon Jo, Yoo Seong Choi, Hyung Joon Cha
Molluscan nacre is a fascinating biomineral consisting of a highly organized calcium carbonate composite that provides unique fracture toughness and an iridescent color. Organisms elaborately control biomineralization using organic macromolecules. We propose the involvement of the matrix protein Pif80 from the pearl oyster Pinctada fucata in the development of the inorganic phase during nacre biomineralization, based on experiments using the recombinant form of Pif80. Through interactions with calcium ions, Pif80 participates in the formation of polymer-induced liquid precursor-like amorphous calcium carbonate granules and stabilizes these granules by forming calcium ion-induced coacervates...
August 2017: Science Advances
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