Cover stories: Making the neutrino scattering cover
Source: ScienceNOW - September 14, 2017 Category: Science Tags: Physics multimedia Source Type: news
A cargo-sorting DNA robot
Two critical challenges in the design and synthesis of molecular robots are modularity and algorithm simplicity. We demonstrate three modular building blocks for a DNA robot that performs cargo sorting at the molecular level. A simple algorithm encoding recognition between cargos and their destinations allows for a simple robot design: a single-stranded DNA with one leg and two foot domains for walking, and one arm and one hand domain for picking up and dropping off cargos. The robot explores a two-dimensional testing ground on the surface of DNA origami, picks up multiple cargos of two types that are initially at unordere...
Source: ScienceNOW - September 14, 2017 Category: Science Authors: Thubagere, A. J., Li, W., Johnson, R. F., Chen, Z., Doroudi, S., Lee, Y. L., Izatt, G., Wittman, S., Srinivas, N., Woods, D., Winfree, E., Qian, L. Tags: Biochemistry, Online Only r-articles Source Type: news
The form and function of channelrhodopsin
Channelrhodopsins are light-gated ion channels that, via regulation of flagellar function, enable single-celled motile algae to seek ambient light conditions suitable for photosynthesis and survival. These plant behavioral responses were initially investigated more than 150 years ago. Recently, major principles of function for light-gated ion channels have been elucidated by creating channelrhodopsins with kinetics that are accelerated or slowed over orders of magnitude, by discovering and designing channelrhodopsins with altered spectral properties, by solving the high-resolution channelrhodopsin crystal structure, and by...
Source: ScienceNOW - September 14, 2017 Category: Science Authors: Deisseroth, K., Hegemann, P. Tags: Neuroscience, Online Only review Source Type: news
Sponsored Collection | SPReading the word: The importance of binding kinetics
Source: ScienceNOW - September 14, 2017 Category: Science Tags: Botany, Cell Biology, Medicine, Diseases, Neuroscience, Pharmacology, Toxicology opms-sups Source Type: news
Webinar | Deciphering cancer: Understanding tumor invasion and the metastatic microenvironment
Source: ScienceNOW - September 14, 2017 Category: Science Authors: Lyden, D. C., Rafii, S. Tags: Biochemistry, Cell Biology, Development, Medicine, Diseases, Molecular Biology opms-sups Source Type: news
Technology Feature | Agreeable antibodies: Antibody validation challenges and solutions
Source: ScienceNOW - September 14, 2017 Category: Science Authors: Dove, A. Tags: opms-sups Source Type: news
A Neolithic expansion, but strong genetic structure, in the independent history of New Guinea
New Guinea shows human occupation since ~50 thousand years ago (ka), independent adoption of plant cultivation ~10 ka, and great cultural and linguistic diversity today. We performed genome-wide single-nucleotide polymorphism genotyping on 381 individuals from 85 language groups in Papua New Guinea and find a sharp divide originating 10 to 20 ka between lowland and highland groups and a lack of non–New Guinean admixture in the latter. All highlanders share ancestry within the last 10 thousand years, with major population growth in the same period, suggesting population structure was reshaped following the Neolithic l...
Source: ScienceNOW - September 14, 2017 Category: Science Authors: Bergström, A., Oppenheimer, S. J., Mentzer, A. J., Auckland, K., Robson, K., Attenborough, R., Alpers, M. P., Koki, G., Pomat, W., Siba, P., Xue, Y., Sandhu, M. S., Tyler-Smith, C. Tags: Anthropology, Genetics reports Source Type: news
Potential role of intratumor bacteria in mediating tumor resistance to the chemotherapeutic drug gemcitabine
Growing evidence suggests that microbes can influence the efficacy of cancer therapies. By studying colon cancer models, we found that bacteria can metabolize the chemotherapeutic drug gemcitabine (2',2'-difluorodeoxycytidine) into its inactive form, 2',2'-difluorodeoxyuridine. Metabolism was dependent on the expression of a long isoform of the bacterial enzyme cytidine deaminase (CDDL), seen primarily in Gammaproteobacteria. In a colon cancer mouse model, gemcitabine resistance was induced by intratumor Gammaproteobacteria, dependent on bacterial CDDL expression, and abrogated by cotreatment with the antibiotic ciprofloxa...
Source: ScienceNOW - September 14, 2017 Category: Science Authors: Geller, L. T., Barzily-Rokni, M., Danino, T., Jonas, O. H., Shental, N., Nejman, D., Gavert, N., Zwang, Y., Cooper, Z. A., Shee, K., Thaiss, C. A., Reuben, A., Livny, J., Avraham, R., Frederick, D. T., Ligorio, M., Chatman, K., Johnston, S. E., Mosher, C. Tags: Medicine, Diseases reports Source Type: news
Thirst-associated preoptic neurons encode an aversive motivational drive
Water deprivation produces a drive to seek and consume water. How neural activity creates this motivation remains poorly understood. We used activity-dependent genetic labeling to characterize neurons activated by water deprivation in the hypothalamic median preoptic nucleus (MnPO). Single-cell transcriptional profiling revealed that dehydration-activated MnPO neurons consist of a single excitatory cell type. After optogenetic activation of these neurons, mice drank water and performed an operant lever-pressing task for water reward with rates that scaled with stimulation frequency. This stimulation was aversive, and instr...
Source: ScienceNOW - September 14, 2017 Category: Science Authors: Allen, W. E., DeNardo, L. A., Chen, M. Z., Liu, C. D., Loh, K. M., Fenno, L. E., Ramakrishnan, C., Deisseroth, K., Luo, L. Tags: Cell Biology reports Source Type: news
DNA replication-coupled histone modification maintains Polycomb gene silencing in plants
Propagation of patterns of gene expression through the cell cycle requires prompt restoration of epigenetic marks after the twofold dilution caused by DNA replication. Here we show that the transcriptional repressive mark H3K27me3 (histone H3 lysine 27 trimethylation) is restored in replicating plant cells through DNA replication–coupled modification of histone variant H3.1. Plants evolved a mechanism for efficient K27 trimethylation on H3.1, which is essential for inheritance of the silencing memory from mother to daughter cells. We illustrate how this mechanism establishes H3K27me3-mediated silencing during the dev...
Source: ScienceNOW - September 14, 2017 Category: Science Authors: Jiang, D., Berger, F. Tags: Botany, Genetics reports Source Type: news
Distinct phases of Polycomb silencing to hold epigenetic memory of cold in Arabidopsis
Gene silencing by Polycomb complexes is central to eukaryotic development. Cold-induced epigenetic repression of FLOWERING LOCUS C (FLC) in the plant Arabidopsis provides an opportunity to study initiation and maintenance of Polycomb silencing. Here, we show that a subset of Polycomb repressive complex 2 factors nucleate silencing in a small region within FLC, locally increasing H3K27me3 levels. This nucleation confers a silenced state that is metastably inherited, with memory held in the local chromatin. Metastable memory is then converted to stable epigenetic silencing through separate Polycomb factors, which spread acro...
Source: ScienceNOW - September 14, 2017 Category: Science Authors: Yang, H., Berry, S., Olsson, T. S. G., Hartley, M., Howard, M., Dean, C. Tags: Botany reports Source Type: news
Fabrication of fillable microparticles and other complex 3D microstructures
We describe a microfabrication method, termed StampEd Assembly of polymer Layers (SEAL), and create injectable pulsatile drug-delivery microparticles, pH sensors, and 3D microfluidic devices that we could not produce using traditional 3D printing. SEAL allows us to generate microstructures with complex geometry at high resolution, produce fully enclosed internal cavities containing a solid or liquid, and use potentially any thermoplastic material without processing additives. (Source: ScienceNOW)
Source: ScienceNOW - September 14, 2017 Category: Science Authors: McHugh, K. J., Nguyen, T. D., Linehan, A. R., Yang, D., Behrens, A. M., Rose, S., Tochka, Z. L., Tzeng, S. Y., Norman, J. J., Anselmo, A. C., Xu, X., Tomasic, S., Taylor, M. A., Lu, J., Guarecuco, R., Langer, R., Jaklenec, A. Tags: Materials Science reports Source Type: news
Soft x-ray excitonics
The dynamic response of excitons in solids is central to modern condensed-phase physics, material sciences, and photonic technologies. However, study and control have hitherto been limited to photon energies lower than the fundamental band gap. Here we report application of attosecond soft x-ray and attosecond optical pulses to study the dynamics of core-excitons at the L2,3 edge of Si in silicon dioxide (SiO2). This attosecond x-ray absorption near-edge spectroscopy (AXANES) technique enables direct probing of the excitons’ quasiparticle character, tracking of their subfemtosecond relaxation, the measurement of exci...
Source: ScienceNOW - September 14, 2017 Category: Science Authors: Moulet, A., Bertrand, J. B., Klostermann, T., Guggenmos, A., Karpowicz, N., Goulielmakis, E. Tags: Physics reports Source Type: news
Highly efficient electrocaloric cooling with electrostatic actuation
Solid-state refrigeration offers potential advantages over traditional cooling systems, but few devices offer high specific cooling power with a high coefficient of performance (COP) and the ability to be applied directly to surfaces. We developed a cooling device with a high intrinsic thermodynamic efficiency using a flexible electrocaloric (EC) polymer film and an electrostatic actuation mechanism. Reversible electrostatic forces reduce parasitic power consumption and allow efficient heat transfer through good thermal contacts with the heat source or heat sink. The EC device produced a specific cooling power of 2.8 watts...
Source: ScienceNOW - September 14, 2017 Category: Science Authors: Ma, R., Zhang, Z., Tong, K., Huber, D., Kornbluh, R., Ju, Y. S., Pei, Q. Tags: Engineering, Materials Science reports Source Type: news
DNA sequence-directed shape change of photopatterned hydrogels via high-degree swelling
Shape-changing hydrogels that can bend, twist, or actuate in response to external stimuli are critical to soft robots, programmable matter, and smart medicine. Shape change in hydrogels has been induced by global cues, including temperature, light, or pH. Here we demonstrate that specific DNA molecules can induce 100-fold volumetric hydrogel expansion by successive extension of cross-links. We photopattern up to centimeter-sized gels containing multiple domains that undergo different shape changes in response to different DNA sequences. Experiments and simulations suggest a simple design rule for controlled shape change. B...
Source: ScienceNOW - September 14, 2017 Category: Science Authors: Cangialosi, A., Yoon, C., Liu, J., Huang, Q., Guo, J., Nguyen, T. D., Gracias, D. H., Schulman, R. Tags: Materials Science reports Source Type: news
Observation of coherent elastic neutrino-nucleus scattering
The coherent elastic scattering of neutrinos off nuclei has eluded detection for four decades, even though its predicted cross section is by far the largest of all low-energy neutrino couplings. This mode of interaction offers new opportunities to study neutrino properties and leads to a miniaturization of detector size, with potential technological applications. We observed this process at a 6.7 confidence level, using a low-background, 14.6-kilogram CsI[Na] scintillator exposed to the neutrino emissions from the Spallation Neutron Source at Oak Ridge National Laboratory. Characteristic signatures in energy and time, pred...
Source: ScienceNOW - September 14, 2017 Category: Science Authors: Akimov, D., Albert, J. B., An, P., Awe, C., Barbeau, P. S., Becker, B., Belov, V., Brown, A., Bolozdynya, A., Cabrera-Palmer, B., Cervantes, M., Collar, J. I., Cooper, R. J., Cooper, R. L., Cuesta, C., Dean, D. J., Detwiler, J. A., Eberhardt, A., Efremenk Tags: Physics reports Source Type: news
Biological fabrication of cellulose fibers with tailored properties
We present an approach that allows biological incorporation of exogenous molecules into cotton fibers to tailor the material’s functionality. In vitro model cultures of upland cotton (Gossypium hirsutum) are incubated with 6-carboxyfluorescein–glucose and dysprosium–1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid–glucose, where the glucose moiety acts as a carrier capable of traveling from the vascular connection to the outermost cell layer of the ovule epidermis, becoming incorporated into the cellulose fibers. This yields fibers with unnatural properties such as fluorescence or magnetism....
Source: ScienceNOW - September 14, 2017 Category: Science Authors: Natalio, F., Fuchs, R., Cohen, S. R., Leitus, G., Fritz-Popovski, G., Paris, O., Kappl, M., Butt, H.-J. Tags: Materials Science reports Source Type: news
Structures of the CRISPR genome integration complex
We present crystal structures of Cas1-Cas2 bound to both donor and target DNA in intermediate and product integration complexes, as well as a cryo–electron microscopy structure of the full CRISPR locus integration complex, including the accessory protein IHF (integration host factor). The structures show unexpectedly that indirect sequence recognition dictates integration site selection by favoring deformation of the repeat and the flanking sequences. IHF binding bends the DNA sharply, bringing an upstream recognition motif into contact with Cas1 to increase both the specificity and efficiency of integration. These r...
Source: ScienceNOW - September 14, 2017 Category: Science Authors: Wright, A. V., Liu, J.-J., Knott, G. J., Doxzen, K. W., Nogales, E., Doudna, J. A. Tags: Biochemistry, Molecular Biology r-articles Source Type: news
Not just Salk
Source: ScienceNOW - September 14, 2017 Category: Science Authors: Greider, C., Hopkins, N., Steitz, J., Amon, A., Asai, D., Barres, B., Bass, B., Bassler, B., Birgeneau, R., Bjorkman, P., Botchan, M., Brugge, J., Cech, T., Colwell, R., Craig, N., deLange, T., Eisen, M., Gottesman, S., Green, R., Handelsman, J., Kimble, Tags: letters Source Type: news