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  • Chemistry  (230)
  • Cells, Cultured
  • American Association for the Advancement of Science (AAAS)  (245)
  • MDPI Publishing
  • 2015-2019  (245)
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  • 1
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2016-07-08
    Description: Separation and purification are critical industrial processes for separating components of chemical mixtures, and these processes account for about half of industrial energy usage (1). Gas mixtures of compounds with very similar physical properties are particularly difficult to separate. On pages 137 and 141 of this issue, Cadiau et al. (2) and Cui et al. (3), respectively, show that microporous materials can be designed to have high adsorption capacity and selectivity for particular hydrocarbons, enabling energy-efficient separation. Author: Jerry Y. S. Lin
    Keywords: Chemistry
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  • 2
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2016-05-27
    Description: Biomass-degrading microorganisms use lytic polysaccharide monooxygenase (LPMO) enzymes to help digest cellulose, chitin, and starch. By cleaving otherwise inaccessible crystalline cellulose chains, these enzymes provide access to hydrolytic enzymes. LPMOs are of interest to biotechnology because efficient depolymerization of cellulose is a major bottleneck for the production of biologically based chemicals and fuels. On page 1098 of this issue, Kracher et al. (1) compare LPMO-reducing substrates in fungi from different taxonomic groups and lifestyles, based on both biochemical and genomic evidence. The results provide insights into reductive activation of LPMO that are important for developing more efficient industrial enzymes for lignocellulose biorefineries. Author: Angel T. Martínez
    Keywords: Chemistry
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  • 3
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2016-03-25
    Description: Author: Marc S. Lavine
    Keywords: Chemistry
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  • 4
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-02-16
    Keywords: Chemistry
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  • 5
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-02-16
    Description: The comment and response concerning the report of oxidation of methane to methanol by water (Reports, 5 May 2017, p. 523) do not fully capture the implications of thermodynamic limitations. A nonisothermal process in which each cycle requires a large temperature swing and permits only substoichiometric methane conversion surely could not be carried out on any practical scale.
    Keywords: Chemistry
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  • 6
    Publication Date: 2018-02-16
    Description: Labinger argues that stepwise reaction of methane with water to produce methanol and hydrogen will never be commercially feasible because of its substoichiometric basis with respect to the active site and the requirement of a large temperature swing. This comment is not touching any new ground, beyond describing the thermodynamic feasibility, thermal cycling, and the role of water as discussed previously. Most important, it does not have a solid numerical basis.
    Keywords: Chemistry
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  • 7
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-07-27
    Keywords: Chemistry
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  • 8
    Publication Date: 2018-07-27
    Description: Vinyl carbocations have been the subject of extensive experimental and theoretical studies over the past five decades. Despite this long history in chemistry, the utility of vinyl cations in chemical synthesis has been limited, with most reactivity studies focusing on solvolysis reactions or intramolecular processes. Here we report synthetic and mechanistic studies of vinyl cations generated through silylium–weakly coordinating anion catalysis. We find that these reactive intermediates undergo mild intermolecular carbon-carbon bond–forming reactions, including carbon-hydrogen (C–H) insertion into unactivated sp 3 C–H bonds and reductive Friedel-Crafts reactions with arenes. Moreover, we conducted computational studies of these alkane C–H functionalization reactions and discovered that they proceed through nonclassical, ambimodal transition structures. This reaction manifold provides a framework for the catalytic functionalization of hydrocarbons using simple ketone derivatives.
    Keywords: Chemistry
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  • 9
    Publication Date: 2018-06-22
    Description: It is commonly assumed that recognition and discrimination of chirality, both in nature and in artificial systems, depend solely on spatial effects. However, recent studies have suggested that charge redistribution in chiral molecules manifests an enantiospecific preference in electron spin orientation. We therefore reasoned that the induced spin polarization may affect enantiorecognition through exchange interactions. Here we show experimentally that the interaction of chiral molecules with a perpendicularly magnetized substrate is enantiospecific. Thus, one enantiomer adsorbs preferentially when the magnetic dipole is pointing up, whereas the other adsorbs faster for the opposite alignment of the magnetization. The interaction is not controlled by the magnetic field per se, but rather by the electron spin orientations, and opens prospects for a distinct approach to enantiomeric separations.
    Keywords: Chemistry
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  • 10
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-06-29
    Keywords: Chemistry
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  • 11
    Publication Date: 2018-12-14
    Description: Theory has established the importance of geometric phase (GP) effects in the adiabatic dynamics of molecular systems with a conical intersection connecting the ground- and excited-state potential energy surfaces, but direct observation of their manifestation in chemical reactions remains a major challenge. Here, we report a high-resolution crossed molecular beams study of the H + HD -〉 H 2 + D reaction at a collision energy slightly above the conical intersection. Velocity map ion imaging revealed fast angular oscillations in product quantum state–resolved differential cross sections in the forward scattering direction for H 2 products at specific rovibrational levels. The experimental results agree with adiabatic quantum dynamical calculations only when the GP effect is included.
    Keywords: Chemistry
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  • 12
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-08-17
    Keywords: Chemistry
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  • 13
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-08-17
    Keywords: Chemistry
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  • 14
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-08-17
    Description: The chemistry of the carbonyl group is essential to modern organic synthesis. The preparation of substituted, enantioenriched 1,3- or 1,5-dicarbonyls is well developed, as their disconnection naturally follows from the intrinsic polarity of the carbonyl group. By contrast, a general enantioselective access to quaternary stereocenters in acyclic 1,4-dicarbonyl systems remains an unresolved problem, despite the tremendous importance of 2,3-substituted 1,4-dicarbonyl motifs in natural products and drug scaffolds. Here we present a broad enantioselective and stereodivergent strategy to access acyclic, polysubstituted 1,4-dicarbonyls via acid-catalyzed [3,3]-sulfonium rearrangement starting from vinyl sulfoxides and ynamides. The stereochemistry at sulfur governs the absolute sense of chiral induction, whereas the double bond geometry dictates the relative configuration of the final products.
    Keywords: Chemistry
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  • 15
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-08-17
    Keywords: Chemistry
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  • 16
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-08-17
    Description: With the recent soaring production of natural gas, the use of methane and other light hydrocarbon feedstocks as starting materials in synthetic transformations is becoming increasingly economically attractive, although it remains chemically challenging. We report the development of photocatalytic C–H amination, alkylation, and arylation of methane, ethane, and higher alkanes under visible light irradiation at ambient temperature. High catalytic efficiency (turnover numbers up to 2900 for methane and 9700 for ethane) and selectivity were achieved using abundant, inexpensive cerium salts as photocatalysts. Ligand-to-metal charge transfer excitation generated alkoxy radicals from simple alcohols that in turn acted as hydrogen atom transfer catalysts. The mixed-phase gas/liquid reaction was adapted to continuous flow, enabling the efficient use of gaseous feedstocks in scalable photocatalytic transformations.
    Keywords: Chemistry
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  • 17
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-08-24
    Keywords: Chemistry
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  • 18
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-08-24
    Keywords: Chemistry
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  • 19
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-08-31
    Keywords: Chemistry
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  • 20
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-08-31
    Description: Intrigued by the potential of nanoscale machines, scientists have long attempted to control molecular motion. We monitored the individual 0.7-nanometer steps of a single molecular hopper as it moved in an electric field along a track in a nanopore controlled by a chemical ratchet. The hopper demonstrated characteristics desired in a moving molecule: defined start and end points, processivity, no chemical fuel requirement, directional motion, and external control. The hopper was readily functionalized to carry cargos. For example, a DNA molecule could be ratcheted along the track in either direction, a prerequisite for nanopore sequencing.
    Keywords: Chemistry
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  • 21
    Publication Date: 2018-09-21
    Description: Phosphorothioate nucleotides have emerged as powerful pharmacological substitutes of their native phosphodiester analogs with important translational applications in antisense oligonucleotide (ASO) therapeutics and cyclic dinucleotide (CDN) synthesis. Stereocontrolled installation of this chiral motif has long been hampered by the systemic use of phosphorus(III) [P(III)]–based reagent systems as the sole practical means of oligonucleotide assembly. A fundamentally different approach is described herein: the invention of a P(V)-based reagent platform for programmable, traceless, diastereoselective phosphorus-sulfur incorporation. The power of this reagent system is demonstrated through the robust and stereocontrolled synthesis of various nucleotidic architectures, including ASOs and CDNs, via an efficient, inexpensive, and operationally simple protocol.
    Keywords: Chemistry
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  • 22
    Publication Date: 2018-09-21
    Description: Here we report an anomalous porous molecular crystal built of C–H···N-bonded double-layered roof-floor components and wall components of a segregatively interdigitated architecture. This complicated porous structure consists of only one type of fully aromatic multijoint molecule carrying three identical dipyridylphenyl wedges. Despite its high symmetry, this molecule accomplishes difficult tasks by using two of its three wedges for roof-floor formation and using its other wedge for wall formation. Although a C–H···N bond is extremely labile, the porous crystal maintains its porosity until thermal breakdown of the C–H···N bonds at 202°C occurs, affording a nonporous polymorph. Though this nonporous crystal survives even at 325°C, it can retrieve the parent porosity under acetonitrile vapor. These findings show how one can translate simplicity into ultrahigh complexity.
    Keywords: Chemistry
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  • 23
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-09-28
    Keywords: Chemistry
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  • 24
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-09-28
    Keywords: Chemistry
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  • 25
    Publication Date: 2018-09-28
    Description: Some of the simplest and most powerful carbon-carbon bond forming strategies take advantage of readily accessible ubiquitous motifs: carbonyls and olefins. Here we report a fundamentally distinct mode of reactivity between carbonyls and olefins that differs from established acid-catalyzed carbonyl-ene, Prins, and carbonyl-olefin metathesis reaction paths. A range of epsilon, zeta-unsaturated ketones undergo Brønsted acid–catalyzed intramolecular cyclization to provide tetrahydrofluorene products via the formation of two new carbon-carbon bonds. Theoretical calculations and accompanying mechanistic studies suggest that this carbocyclization reaction proceeds through the intermediacy of a transient oxetane formed by oxygen atom transfer. The complex polycyclic frameworks in this product class appear as common substructures in organic materials, bioactive natural products, and recently developed pharmaceuticals.
    Keywords: Chemistry
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  • 26
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-09-28
    Description: Alkene aminoarylation with a single, bifunctional reagent is a concise synthetic strategy. We report a catalytic protocol for the addition of arylsulfonylacetamides across electron-rich alkenes with complete anti-Markovnikov regioselectivity and excellent diastereoselectivity to provide 2,2-diarylethylamines. In this process, single-electron alkene oxidation enables carbon-nitrogen bond formation to provide a key benzylic radical poised for a Smiles-Truce 1,5-aryl shift. This reaction is redox-neutral, exhibits broad functional group compatibility, and occurs at room temperature with loss of sulfur dioxide. As this process is driven by visible light, uses readily available starting materials, and demonstrates convergent synthesis, it is well suited for use in a variety of synthetic endeavors.
    Keywords: Chemistry
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  • 27
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-10-05
    Keywords: Chemistry
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  • 28
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-10-05
    Keywords: Chemistry
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  • 29
    Publication Date: 2018-10-05
    Description: Photocatalysis based on optically active, "plasmonic" metal nanoparticles has emerged as a promising approach to facilitate light-driven chemical conversions under far milder conditions than thermal catalysis. However, an understanding of the relation between thermal and electronic excitations has been lacking. We report the substantial light-induced reduction of the thermal activation barrier for ammonia decomposition on a plasmonic photocatalyst. We introduce the concept of a light-dependent activation barrier to account for the effect of light illumination on electronic and thermal excitations in a single unified picture. This framework provides insight into the specific role of hot carriers in plasmon-mediated photochemistry, which is critically important for designing energy-efficient plasmonic photocatalysts.
    Keywords: Chemistry
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  • 30
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-10-12
    Keywords: Chemistry
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  • 31
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-10-12
    Keywords: Chemistry
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  • 32
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-10-12
    Description: Single-electron reduction of a carbonyl to a ketyl enables access to a polarity-reversed platform of reactivity for this cornerstone functional group. However, the synthetic utility of the ketyl radical is hindered by the strong reductants necessary for its generation, which also limit its reactivity to net reductive mechanisms. We report a strategy for net redox-neutral generation and reaction of ketyl radicals. The in situ conversion of aldehydes to α-acetoxy iodides lowers their reduction potential by more than 1 volt, allowing for milder access to the corresponding ketyl radicals and an oxidative termination event. Upon subjecting these iodides to a dimanganese decacarbonyl precatalyst and visible light irradiation, an atom transfer radical addition (ATRA) mechanism affords a broad scope of vinyl iodide products with high Z -selectivity.
    Keywords: Chemistry
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  • 33
    Publication Date: 2018-10-12
    Description: Reactions that form a product with the same reactive functionality as that of one of the starting compounds frequently end in oligomerization. As a salient example, selective aldol coupling of the smallest, though arguably most useful, enolizable aldehyde, acetaldehyde, with just one partner substrate has proven to be extremely challenging. Here, we report a highly enantioselective Mukaiyama aldol reaction with the simple triethylsilyl (TES) and tert -butyldimethylsilyl (TBS) enolates of acetaldehyde and various aliphatic and aromatic acceptor aldehydes. The reaction is catalyzed by recently developed, strongly acidic imidodiphosphorimidates (IDPi), which, like enzymes, display a confined active site but, like small-molecule catalysts, have a broad substrate scope. The process is scalable, fast, efficient (0.5 to 1.5 mole % catalyst loading), and greatly simplifies access to highly valuable silylated acetaldehyde aldols.
    Keywords: Chemistry
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  • 34
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-12-21
    Keywords: Chemistry
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  • 35
    Publication Date: 2018-12-21
    Description: Single-molecule magnets (SMMs) containing only one metal center may represent the lower size limit for molecule-based magnetic information storage materials. Their current drawback is that all SMMs require liquid-helium cooling to show magnetic memory effects. We now report a chemical strategy to access the dysprosium metallocene cation [(Cp i Pr5 )Dy(Cp*)] + (Cp i Pr5 , penta-iso-propylcyclopentadienyl; Cp *, pentamethylcyclopentadienyl), which displays magnetic hysteresis above liquid-nitrogen temperatures. An effective energy barrier to reversal of the magnetization of U eff = 1541 wave number is also measured. The magnetic blocking temperature of T B = 80 kelvin for this cation overcomes an essential barrier toward the development of nanomagnet devices that function at practical temperatures.
    Keywords: Chemistry
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  • 36
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2016-04-29
    Description: Author: Jake Yeston
    Keywords: Chemistry
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  • 37
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2016-03-18
    Description: Author: Marc S. Lavine
    Keywords: Chemistry
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  • 38
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2016-03-18
    Description: Water plays a central role in scientific disciplines ranging from geology to astronomy to biology. Yet it is an extraordinarily dif cult liquid to understand because of its complex, ever-changing patterns of hydrogen bonds. Studies of small water clusters have provided important insights into the concerted hydrogen-bond motions that can occur in water. These studies are also crucial for developing an accurate potential function for simulating the properties of liquid water and ice (1). On page 1310 of this issue, Richardson et al. (2) provide evidence for a concerted type of motion in which two hydrogen bonds in a water cluster are broken simultaneously (see the figure). The results have implications for many areas of scientific study, including the chemistry of polar solvents, the conformations of proteins, and the dissolution of ions in minerals. Author: David C. Clary
    Keywords: Chemistry
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  • 39
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2016-03-18
    Description: Author: Jake Yeston
    Keywords: Chemistry
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  • 40
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2016-03-04
    Description: Lower olefins, particularly ethylene (C2H4), propylene (C3H6), and butylene (C4H8), are important intermediates in the manufacture of products such as plastics, solvents, paints, and medicines. They are produced worldwide in amounts exceeding 200 million tons per year (see the photo) (1), mostly from crude oil. More recent approaches use methanol or synthesis gas (syngas; a mixture of carbon monoxide and hydrogen) as feedstocks, but capital investments are high and/or selectivities to lower olefins limited. A bifunctional catalyst reported by Jiao et al. on page 1065 of this issue (2) enables the direct conversion of synthesis gas to lower olefins with a surprisingly high selectivity. Author: Krijn P. de Jong
    Keywords: Chemistry
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  • 41
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-10-19
    Keywords: Chemistry
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  • 42
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-10-19
    Description: The development of highly reactive and stereoselective catalytic systems is required not only to improve existing synthetic methods but also to invent distinct chemical reactions. Herein, a homogenized combination of nickel-based Lewis acid–surfactant-combined catalysts and single-walled carbon nanotubes is shown to exhibit substantial activity in water. In addition to the enhanced reactivity, stereoselective performance and long-term stability were demonstrated in asymmetric conjugate addition reactions of aldoximes to furnish chiral nitrones in high yields with excellent selectivities. The practical and straightforward application of the designed catalysts in water provides an expedient, environmentally benign, and highly efficient pathway to access optically active compounds.
    Keywords: Chemistry
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  • 43
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-11-02
    Keywords: Chemistry
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  • 44
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-12-14
    Keywords: Chemistry
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  • 45
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-10-26
    Keywords: Chemistry
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  • 46
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-11-02
    Description: Exploration of intermediates that enable chemoselective cycloaddition reactions and expeditious construction of fused- or bridged-ring systems is a continuous challenge for organic synthesis. As an intermediate of interest, the oxyallyl cation has been harnessed to synthesize architectures containing seven-membered rings via (4+3) cycloaddition. However, its potential to access five-membered skeletons is underdeveloped, largely due to the thermally forbidden (3+2) pathway. Here, the combination of a tailored precursor and a Pd(0) catalyst generates a Pd-oxyallyl intermediate that cyclizes with conjugated dienes to produce a diverse array of tetrahydrofuran skeletons. The cycloaddition overrides conventional (4+3) selectivity by proceeding through a stepwise pathway involving a Pd-allyl transfer and ring closure sequence. Subsequent treatment of the (3+2) adducts with a palladium catalyst converts the heterocycles to the carbocyclic cyclopentanones.
    Keywords: Chemistry
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  • 47
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-11-16
    Keywords: Chemistry
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  • 48
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-08-10
    Keywords: Chemistry
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  • 49
    Publication Date: 2018-08-10
    Description: Understanding the practical limitations of chemical reactions is critically important for efficiently planning the synthesis of compounds in pharmaceutical, agrochemical, and specialty chemical research and development. However, literature reports of the scope of new reactions are often cursory and biased toward successful results, severely limiting the ability to predict reaction outcomes for untested substrates. We herein illustrate strategies for carrying out large-scale surveys of chemical reactivity by using a material-sparing nanomole-scale automated synthesis platform with greatly expanded synthetic scope combined with ultrahigh-throughput matrix-assisted laser desorption/ionization–time-of-flight mass spectrometry (MALDI-TOF MS).
    Keywords: Chemistry
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  • 50
    Publication Date: 2018-08-24
    Description: Researchers around the world have observed the formation of molecularly ordered structures of unknown origin on the surface of titanium dioxide (TiO 2 ) photocatalysts exposed to air and solution. Using a combination of atomic-scale microscopy and spectroscopy, we show that TiO 2 selectively adsorbs atmospheric carboxylic acids that are typically present in parts-per-billion concentrations while effectively repelling other adsorbates, such as alcohols, that are present in much higher concentrations. The high affinity of the surface for carboxylic acids is attributed to their bidentate binding. These self-assembled monolayers have the unusual property of being both hydrophobic and highly water-soluble, which may contribute to the self-cleaning properties of TiO 2 . This finding is relevant to TiO 2 photocatalysis, because the self-assembled carboxylate monolayers block the undercoordinated surface cation sites typically implicated in photocatalysis.
    Keywords: Chemistry
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  • 51
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-08-31
    Keywords: Chemistry
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  • 52
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-08-31
    Keywords: Chemistry
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  • 53
    Publication Date: 2018-08-31
    Description: The alkaline earth metals calcium (Ca), strontium (Sr), and barium (Ba) typically engage in chemical bonding as classical main-group elements through their n s and n p valence orbitals, where n is the principal quantum number. Here we report the isolation and spectroscopic characterization of eight-coordinate carbonyl complexes M(CO) 8 (where M = Ca, Sr, or Ba) in a low-temperature neon matrix. Analysis of the electronic structure of these cubic O h -symmetric complexes reveals that the metal–carbon monoxide (CO) bonds arise mainly from [M(d )] -〉 (CO) 8 backdonation, which explains the strong observed red shift of the C-O stretching frequencies. The corresponding radical cation complexes were also prepared in gas phase and characterized by mass-selected infrared photodissociation spectroscopy, confirming adherence to the 18-electron rule more conventionally associated with transition metal chemistry.
    Keywords: Chemistry
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  • 54
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-09-07
    Keywords: Chemistry
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  • 55
    Publication Date: 2018-09-07
    Description: Mystery surrounds the transition from gas-phase hydrocarbon precursors to terrestrial soot and interstellar dust, which are carbonaceous particles formed under similar conditions. Although polycyclic aromatic hydrocarbons (PAHs) are known precursors to high-temperature carbonaceous-particle formation, the molecular pathways that initiate particle formation are unknown. We present experimental and theoretical evidence for rapid molecular clustering–reaction pathways involving radicals with extended conjugation. These radicals react with other hydrocarbon species to form covalently bound complexes that promote further growth and clustering by regenerating resonance-stabilized radicals through low-barrier hydrogen-abstraction and hydrogen-ejection reactions. Such radical–chain reaction pathways may lead to covalently bound clusters of PAHs and other hydrocarbons that would otherwise be too small to condense at high temperatures, thus providing the key mechanistic steps for rapid particle formation and surface growth by hydrocarbon chemisorption.
    Keywords: Chemistry
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  • 56
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-09-14
    Keywords: Chemistry
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  • 57
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-04-27
    Keywords: Chemistry
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  • 58
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-04-27
    Keywords: Chemistry
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  • 59
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-04-27
    Description: Basic heteroarenes are a ubiquitous feature of pharmaceuticals and bioactive molecules, and Minisci-type additions of radical nucleophiles are a leading method for their elaboration. Despite many Minisci-type protocols that result in the formation of stereocenters, exerting control over the absolute stereochemistry at these centers remains an unmet challenge. We report a process for addition of prochiral radicals, generated from amino acid derivatives, to pyridines and quinolines. Our method offers excellent control of both enantioselectivity and regioselectivity. An enantiopure chiral Brønsted acid catalyst serves both to activate the substrate and induce asymmetry, while an iridium photocatalyst mediates the required electron transfer processes. We anticipate that this method will expedite access to enantioenriched small-molecule building blocks bearing versatile basic heterocycles.
    Keywords: Chemistry
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  • 60
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-05-25
    Keywords: Chemistry
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  • 61
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-05-25
    Keywords: Chemistry
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  • 62
    Publication Date: 2018-10-26
    Description: Primary amines are essential constituents of biologically active molecules and versatile intermediates in the synthesis of drugs and agrochemicals. However, their preparation from easily accessible alkenes remains challenging. Here, we report a general strategy to access primary amines from alkenes through an operationally simple iron-catalyzed aminochlorination reaction. A stable hydroxylamine derivative and benign sodium chloride act as the respective nitrogen and chlorine sources. The reaction proceeds at room temperature under air; tolerates a large scope of aliphatic and conjugated alkenes, including densely functionalized substrates; and provides excellent anti-Markovnikov regioselectivity with respect to the amino group. The reactivity of the 2-chloroalkylamine products, an understudied class of amphoteric molecules, enables facile access to linear or branched aliphatic amines, aziridines, aminonitriles, azido amines, and homoallylic amines.
    Keywords: Chemistry
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  • 63
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-11-09
    Keywords: Chemistry
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  • 64
    Publication Date: 2018-11-09
    Description: Despite the enormous potential for the use of stereospecific cross-coupling reactions to rationally manipulate the three-dimensional structure of organic molecules, the factors that control the transfer of stereochemistry in these reactions remain poorly understood. Here we report a mechanistic and synthetic investigation into the use of enantioenriched alkylboron nucleophiles in stereospecific Pd-catalyzed Suzuki cross-coupling reactions. By developing a suite of molecular descriptors of phosphine ligands, we could apply predictive statistical models to select or design distinct ligands that respectively promoted stereoinvertive and stereoretentive cross-coupling reactions. Stereodefined branched structures were thereby accessed through the predictable manipulation of absolute stereochemistry, and a general model for the mechanism of alkylboron transmetallation was proposed.
    Keywords: Chemistry
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  • 65
    Publication Date: 2018-11-16
    Description: Heterobiaryls composed of pyridine and diazine rings are key components of pharmaceuticals and are often central to pharmacological function. We present an alternative approach to metal-catalyzed cross-coupling to make heterobiaryls using contractive phosphorus C–C couplings, also termed phosphorus ligand coupling reactions. The process starts by regioselective phosphorus substitution of the C–H bonds para to nitrogen in two successive heterocycles; ligand coupling is then triggered via acidic alcohol solutions to form the heterobiaryl bond. Mechanistic studies imply that ligand coupling is an asynchronous process involving migration of one heterocycle to the ipso position of the other around a central pentacoordinate P(V) atom. The strategy can be applied to complex drug-like molecules containing multiple reactive sites and polar functional groups, and also enables convergent coupling of drug fragments and late-stage heteroarylation of pharmaceuticals.
    Keywords: Chemistry
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  • 66
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-07-06
    Keywords: Chemistry
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  • 67
    Publication Date: 2018-07-06
    Description: Conical intersections play a critical role in excited-state dynamics of polyatomic molecules because they govern the reaction pathways of many nonadiabatic processes. However, ultrafast probes have lacked sufficient spatial resolution to image wave-packet trajectories through these intersections directly. Here, we present the simultaneous experimental characterization of one-photon and two-photon excitation channels in isolated CF 3 I molecules using ultrafast gas-phase electron diffraction. In the two-photon channel, we have mapped out the real-space trajectories of a coherent nuclear wave packet, which bifurcates onto two potential energy surfaces when passing through a conical intersection. In the one-photon channel, we have resolved excitation of both the umbrella and the breathing vibrational modes in the CF 3 fragment in multiple nuclear dimensions. These findings benchmark and validate ab initio nonadiabatic dynamics calculations.
    Keywords: Chemistry
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  • 68
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-07-13
    Keywords: Chemistry
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  • 69
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-06-22
    Keywords: Chemistry
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  • 70
    Publication Date: 2015-04-11
    Description: Protein phosphorylation regulates virtually all biological processes. Although protein kinases are popular drug targets, targeting protein phosphatases remains a challenge. Here, we describe Sephin1 (selective inhibitor of a holophosphatase), a small molecule that safely and selectively inhibited a regulatory subunit of protein phosphatase 1 in vivo. Sephin1 selectively bound and inhibited the stress-induced PPP1R15A, but not the related and constitutive PPP1R15B, to prolong the benefit of an adaptive phospho-signaling pathway, protecting cells from otherwise lethal protein misfolding stress. In vivo, Sephin1 safely prevented the motor, morphological, and molecular defects of two otherwise unrelated protein-misfolding diseases in mice, Charcot-Marie-Tooth 1B, and amyotrophic lateral sclerosis. Thus, regulatory subunits of phosphatases are drug targets, a property exploited here to safely prevent two protein misfolding diseases.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4490275/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4490275/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Das, Indrajit -- Krzyzosiak, Agnieszka -- Schneider, Kim -- Wrabetz, Lawrence -- D'Antonio, Maurizio -- Barry, Nicholas -- Sigurdardottir, Anna -- Bertolotti, Anne -- 309516/European Research Council/International -- MC_U105185860/Medical Research Council/United Kingdom -- R01-NS55256/NS/NINDS NIH HHS/ -- Medical Research Council/United Kingdom -- New York, N.Y. -- Science. 2015 Apr 10;348(6231):239-42. doi: 10.1126/science.aaa4484.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Medical Research Council Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge, CB2 0QH, UK. ; Division of Genetics and Cell Biology, San Raffaele Scientific Institute, 20132 Milan, Italy. ; Medical Research Council Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge, CB2 0QH, UK. aberto@mrc-lmb.cam.ac.uk.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25859045" target="_blank"〉PubMed〈/a〉
    Keywords: Amyotrophic Lateral Sclerosis/drug therapy/metabolism/pathology ; Animals ; Cells, Cultured ; Charcot-Marie-Tooth Disease/drug therapy/metabolism/pathology ; Disease Models, Animal ; Endoplasmic Reticulum Stress/drug effects ; Enzyme Inhibitors/metabolism/pharmacokinetics/*pharmacology/toxicity ; Guanabenz/*analogs & derivatives/chemical ; synthesis/metabolism/pharmacology/toxicity ; HeLa Cells ; Humans ; Mice ; Mice, Transgenic ; Molecular Targeted Therapy ; Phosphorylation ; Protein Folding ; Protein Phosphatase 1/*antagonists & inhibitors ; Proteostasis Deficiencies/*drug therapy/*prevention & control ; Signal Transduction
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  • 71
    Publication Date: 2015-06-20
    Description: The inactive X chromosome (Xi) serves as a model to understand gene silencing on a global scale. Here, we perform "identification of direct RNA interacting proteins" (iDRiP) to isolate a comprehensive protein interactome for Xist, an RNA required for Xi silencing. We discover multiple classes of interactors-including cohesins, condensins, topoisomerases, RNA helicases, chromatin remodelers, and modifiers-that synergistically repress Xi transcription. Inhibiting two or three interactors destabilizes silencing. Although Xist attracts some interactors, it repels architectural factors. Xist evicts cohesins from the Xi and directs an Xi-specific chromosome conformation. Upon deleting Xist, the Xi acquires the cohesin-binding and chromosomal architecture of the active X. Our study unveils many layers of Xi repression and demonstrates a central role for RNA in the topological organization of mammalian chromosomes.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Minajigi, Anand -- Froberg, John E -- Wei, Chunyao -- Sunwoo, Hongjae -- Kesner, Barry -- Colognori, David -- Lessing, Derek -- Payer, Bernhard -- Boukhali, Myriam -- Haas, Wilhelm -- Lee, Jeannie T -- R01-DA-38695/DA/NIDA NIH HHS/ -- R03-MH97478/MH/NIMH NIH HHS/ -- New York, N.Y. -- Science. 2015 Jul 17;349(6245). pii: aab2276. doi: 10.1126/science.aab2276. Epub 2015 Jun 18.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Howard Hughes Medical Institute; Department of Molecular Biology, Massachusetts General Hospital, Boston, MA, USA; Department of Genetics, Harvard Medical School, Boston, MA, USA. ; Massachusetts General Hospital Cancer Center, Charlestown, Boston, MA; Department of Medicine, Harvard Medical School, Boston, MA, USA. ; Howard Hughes Medical Institute; Department of Molecular Biology, Massachusetts General Hospital, Boston, MA, USA; Department of Genetics, Harvard Medical School, Boston, MA, USA. lee@molbio.mgh.harvard.edu.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26089354" target="_blank"〉PubMed〈/a〉
    Keywords: Adenosine Triphosphatases/metabolism ; Animals ; Cell Cycle Proteins/*metabolism ; Cells, Cultured ; Chromatin Assembly and Disassembly ; Chromosomal Proteins, Non-Histone/*metabolism ; DNA-Binding Proteins/metabolism ; Embryonic Stem Cells/metabolism ; Fibroblasts/metabolism ; Gene Knockdown Techniques ; Gene Silencing ; Mice ; Multiprotein Complexes/metabolism ; Nucleic Acid Conformation ; Proteomics ; RNA Helicases/metabolism ; RNA, Long Noncoding/*metabolism ; X Chromosome/chemistry/genetics/*metabolism ; *X Chromosome Inactivation
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  • 72
    Publication Date: 2015-05-09
    Description: Efforts to identify host determinants for malaria have been hindered by the absence of a nucleus in erythrocytes, which precludes genetic manipulation in the cell in which the parasite replicates. We used cultured red blood cells derived from hematopoietic stem cells to carry out a forward genetic screen for Plasmodium falciparum host determinants. We found that CD55 is an essential host factor for P. falciparum invasion. CD55-null erythrocytes were refractory to invasion by all isolates of P. falciparum because parasites failed to attach properly to the erythrocyte surface. Thus, CD55 is an attractive target for the development of malaria therapeutics. Hematopoietic stem cell-based forward genetic screens may be valuable for the identification of additional host determinants of malaria pathogenesis.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4465434/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4465434/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Egan, Elizabeth S -- Jiang, Rays H Y -- Moechtar, Mischka A -- Barteneva, Natasha S -- Weekes, Michael P -- Nobre, Luis V -- Gygi, Steven P -- Paulo, Joao A -- Frantzreb, Charles -- Tani, Yoshihiko -- Takahashi, Junko -- Watanabe, Seishi -- Goldberg, Jonathan -- Paul, Aditya S -- Brugnara, Carlo -- Root, David E -- Wiegand, Roger C -- Doench, John G -- Duraisingh, Manoj T -- 100140/Wellcome Trust/United Kingdom -- 1K08AI103034-01A1/AI/NIAID NIH HHS/ -- K01 DK098285/DK/NIDDK NIH HHS/ -- K01DK098285/DK/NIDDK NIH HHS/ -- K08 AI103034/AI/NIAID NIH HHS/ -- K12-HD000850/HD/NICHD NIH HHS/ -- R01AI091787/AI/NIAID NIH HHS/ -- New York, N.Y. -- Science. 2015 May 8;348(6235):711-4. doi: 10.1126/science.aaa3526.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Immunology and Infectious Diseases, Harvard T. H. Chan School of Public Health, Boston, MA, USA. Division of Infectious Diseases, Boston Children's Hospital, Boston, MA, USA. ; Department of Immunology and Infectious Diseases, Harvard T. H. Chan School of Public Health, Boston, MA, USA. Department of Global Health and Center for Drug Discovery and Innovation, University of South Florida, Tampa, FL, USA. ; Department of Immunology and Infectious Diseases, Harvard T. H. Chan School of Public Health, Boston, MA, USA. ; Department of Pediatrics, Harvard Medical School and Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA, USA. ; Cambridge Institute for Medical Research, University of Cambridge, Cambridge, UK. ; Department of Cell Biology, Harvard Medical School, Boston, MA, USA. ; Japanese Red Cross Kinki Block Blood Center, Osaka, Japan. ; Japanese Red Cross Kyushu Block Blood Center, Fukuoka, Japan. ; Department of Laboratory Medicine, Boston Children's Hospital and Harvard Medical School, Boston, MA, USA. ; The Broad Institute of Harvard and Massachussetts Insititute of Technology, Cambridge, MA, USAA. ; Department of Immunology and Infectious Diseases, Harvard T. H. Chan School of Public Health, Boston, MA, USA. The Broad Institute of Harvard and Massachussetts Insititute of Technology, Cambridge, MA, USAA. mduraisi@hsph.harvard.edu.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25954012" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Antigens, CD44/genetics ; Antigens, CD55/*genetics ; Cell Differentiation/genetics ; Cells, Cultured ; Erythrocytes/cytology/metabolism/*parasitology ; Genetic Testing ; Hematopoietic Stem Cells/cytology ; Host-Parasite Interactions/*genetics ; Humans ; Malaria, Falciparum/*genetics/*parasitology ; Plasmodium falciparum/*pathogenicity ; RNA, Small Interfering/genetics
    Print ISSN: 0036-8075
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    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 73
    Publication Date: 2015-09-01
    Description: Human mutations that truncate the massive sarcomere protein titin [TTN-truncating variants (TTNtvs)] are the most common genetic cause for dilated cardiomyopathy (DCM), a major cause of heart failure and premature death. Here we show that cardiac microtissues engineered from human induced pluripotent stem (iPS) cells are a powerful system for evaluating the pathogenicity of titin gene variants. We found that certain missense mutations, like TTNtvs, diminish contractile performance and are pathogenic. By combining functional analyses with RNA sequencing, we explain why truncations in the A-band domain of TTN cause DCM, whereas truncations in the I band are better tolerated. Finally, we demonstrate that mutant titin protein in iPS cell-derived cardiomyocytes results in sarcomere insufficiency, impaired responses to mechanical and beta-adrenergic stress, and attenuated growth factor and cell signaling activation. Our findings indicate that titin mutations cause DCM by disrupting critical linkages between sarcomerogenesis and adaptive remodeling.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4618316/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4618316/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hinson, John T -- Chopra, Anant -- Nafissi, Navid -- Polacheck, William J -- Benson, Craig C -- Swist, Sandra -- Gorham, Joshua -- Yang, Luhan -- Schafer, Sebastian -- Sheng, Calvin C -- Haghighi, Alireza -- Homsy, Jason -- Hubner, Norbert -- Church, George -- Cook, Stuart A -- Linke, Wolfgang A -- Chen, Christopher S -- Seidman, J G -- Seidman, Christine E -- EB017103/EB/NIBIB NIH HHS/ -- HG005550/HG/NHGRI NIH HHS/ -- HL007374/HL/NHLBI NIH HHS/ -- HL115553/HL/NHLBI NIH HHS/ -- HL125807/HL/NHLBI NIH HHS/ -- K08 HL125807/HL/NHLBI NIH HHS/ -- T32 HL007208/HL/NHLBI NIH HHS/ -- Department of Health/United Kingdom -- Howard Hughes Medical Institute/ -- New York, N.Y. -- Science. 2015 Aug 28;349(6251):982-6. doi: 10.1126/science.aaa5458.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Division of Cardiovascular Medicine, Brigham and Women's Hospital, Boston, MA 02115, USA. jthinson@partners.org cseidman@genetics.med.harvard.edu. ; Department of Biomedical Engineering, Boston University, Boston, MA 02215, USA. The Wyss Institute for Biologically Inspired Engineering at Harvard University, Boston, MA 02115, USA. ; Department of Genetics, Harvard Medical School, Boston, MA 02115, USA. ; Division of Cardiovascular Medicine, Beth Israel Deaconess Medical Center, Boston, MA 02215, USA. ; Department of Cardiovascular Physiology, Ruhr University Bochum, MA 3/56 D-44780, Bochum, Germany. ; The Wyss Institute for Biologically Inspired Engineering at Harvard University, Boston, MA 02115, USA. Department of Genetics, Harvard Medical School, Boston, MA 02115, USA. ; Cardiovascular and Metabolic Sciences, Max Delbruck Center for Molecular Medicine, Berlin, Germany. ; Division of Cardiovascular Medicine, Brigham and Women's Hospital, Boston, MA 02115, USA. Department of Genetics, Harvard Medical School, Boston, MA 02115, USA. Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA. ; Cardiovascular and Metabolic Sciences, Max Delbruck Center for Molecular Medicine, Berlin, Germany. DZHK (German Center for Cardiovascular Research), Partner Site Berlin, Berlin, Germany. ; National Institute for Health Research (NIHR) Biomedical Research Unit in Cardiovascular Disease at Royal Brompton and Harefield National Health Service (NHS) Foundation Trust, Imperial College London, London, UK. National Heart Centre and Duke-National University, Singapore, Singapore. ; Division of Cardiovascular Medicine, Brigham and Women's Hospital, Boston, MA 02115, USA. Department of Genetics, Harvard Medical School, Boston, MA 02115, USA. Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA. jthinson@partners.org cseidman@genetics.med.harvard.edu.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26315439" target="_blank"〉PubMed〈/a〉
    Keywords: Adrenergic beta-Agonists/pharmacology ; Cardiomyopathy, Dilated/*genetics/pathology/*physiopathology ; Cells, Cultured ; Connectin/chemistry/*genetics/*physiology ; Heart Rate ; Humans ; Induced Pluripotent Stem Cells/*physiology ; Isoproterenol/pharmacology ; Mutant Proteins/chemistry/physiology ; *Mutation, Missense ; Myocardial Contraction ; Myocytes, Cardiac/*physiology ; RNA/genetics/metabolism ; Sarcomeres/*physiology/ultrastructure ; Sequence Analysis, RNA ; Signal Transduction ; Stress, Physiological
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  • 74
    Publication Date: 2015-06-06
    Description: Aneuploidy in human eggs is the leading cause of pregnancy loss and several genetic disorders such as Down syndrome. Most aneuploidy results from chromosome segregation errors during the meiotic divisions of an oocyte, the egg's progenitor cell. The basis for particularly error-prone chromosome segregation in human oocytes is not known. We analyzed meiosis in more than 100 live human oocytes and identified an error-prone chromosome-mediated spindle assembly mechanism as a major contributor to chromosome segregation defects. Human oocytes assembled a meiotic spindle independently of either centrosomes or other microtubule organizing centers. Instead, spindle assembly was mediated by chromosomes and the small guanosine triphosphatase Ran in a process requiring ~16 hours. This unusually long spindle assembly period was marked by intrinsic spindle instability and abnormal kinetochore-microtubule attachments, which favor chromosome segregation errors and provide a possible explanation for high rates of aneuploidy in human eggs.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4477045/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4477045/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Holubcova, Zuzana -- Blayney, Martyn -- Elder, Kay -- Schuh, Melina -- MC_U105192711/Medical Research Council/United Kingdom -- New York, N.Y. -- Science. 2015 Jun 5;348(6239):1143-7. doi: 10.1126/science.aaa9529.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Medical Research Council, Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, Cambridge CB2 0QH, UK. ; Bourn Hall Clinic, Bourn, Cambridge CB23 2TN, UK. ; Medical Research Council, Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, Cambridge CB2 0QH, UK. mschuh@mrc-lmb.cam.ac.uk.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26045437" target="_blank"〉PubMed〈/a〉
    Keywords: Anaphase ; *Aneuploidy ; Animals ; Cells, Cultured ; *Chromosome Segregation ; Female ; Green Fluorescent Proteins/genetics/metabolism ; Humans ; Kinetochores/metabolism ; *Meiosis ; Mice ; Microtubule-Associated Proteins/genetics/metabolism ; Microtubule-Organizing Center/metabolism ; Oocytes/*pathology ; Spindle Apparatus/*metabolism ; ran GTP-Binding Protein/metabolism
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  • 75
    Publication Date: 2015-09-05
    Description: Growing up on a dairy farm protects children from allergy, hay fever, and asthma. A mechanism linking exposure to this endotoxin (bacterial lipopolysaccharide)-rich environment with protection has remained elusive. Here we show that chronic exposure to low-dose endotoxin or farm dust protects mice from developing house dust mite (HDM)-induced asthma. Endotoxin reduced epithelial cell cytokines that activate dendritic cells (DCs), thus suppressing type 2 immunity to HDMs. Loss of the ubiquitin-modifying enzyme A20 in lung epithelium abolished the protective effect. A single-nucleotide polymorphism in the gene encoding A20 was associated with allergy and asthma risk in children growing up on farms. Thus, the farming environment protects from allergy by modifying the communication between barrier epithelial cells and DCs through A20 induction.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Schuijs, Martijn J -- Willart, Monique A -- Vergote, Karl -- Gras, Delphine -- Deswarte, Kim -- Ege, Markus J -- Madeira, Filipe Branco -- Beyaert, Rudi -- van Loo, Geert -- Bracher, Franz -- von Mutius, Erika -- Chanez, Pascal -- Lambrecht, Bart N -- Hammad, Hamida -- New York, N.Y. -- Science. 2015 Sep 4;349(6252):1106-10. doi: 10.1126/science.aac6623.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Laboratory of Immunoregulation, VIB Inflammation Research Center, Ghent, Belgium. Department of Internal Medicine, Ghent University, Ghent, Belgium. ; Department of Respiratory Medicine, Assistance Publique Hopitaux de Marseille, UMR INSERM U1067 CNRS 7333, Aix Marseille University, Marseille, France. ; Dr. von Hauner Children's Hospital, Ludwig-Maximilians-Universitat, Munich, Germany. ; Unit of Molecular Signal Transduction, VIB Inflammation Research Center, Ghent, Belgium. Department of Biomedical Molecular Biology, Ghent University, Ghent, Belgium. ; Center for Drug Research, Department of Pharmacy, Ludwig Maximilians University, Butenandtstrasse 5-13, D-81377 Munich, Germany. ; Laboratory of Immunoregulation, VIB Inflammation Research Center, Ghent, Belgium. Department of Internal Medicine, Ghent University, Ghent, Belgium. Department of Pulmonary Medicine, Erasmus Medical Center, Rotterdam, Netherlands. hamida.hammad@ugent.be bart.lambrecht@ugent.be. ; Laboratory of Immunoregulation, VIB Inflammation Research Center, Ghent, Belgium. Department of Internal Medicine, Ghent University, Ghent, Belgium. hamida.hammad@ugent.be bart.lambrecht@ugent.be.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26339029" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Asthma/immunology/prevention & control ; Cells, Cultured ; Child ; DNA-Binding Proteins/*biosynthesis ; Dairying ; Dendritic Cells/immunology ; Dust/*immunology ; Female ; Humans ; Hygiene Hypothesis ; Hypersensitivity/enzymology/immunology/*prevention & control ; Inhalation Exposure ; Intracellular Signaling Peptides and Proteins/*biosynthesis ; Lipopolysaccharides/*immunology ; Lung/*enzymology/immunology ; Mice ; Mice, Inbred C57BL ; Nuclear Proteins/*biosynthesis ; Pyroglyphidae/*immunology ; Respiratory Mucosa/*enzymology/immunology
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  • 76
    Publication Date: 2015-08-08
    Description: Cytoplasmic aggregation of TDP-43, accompanied by its nuclear clearance, is a key common pathological hallmark of amyotrophic lateral sclerosis and frontotemporal dementia (ALS-FTD). However, a limited understanding of this RNA-binding protein (RBP) impedes the clarification of pathogenic mechanisms underlying TDP-43 proteinopathy. In contrast to RBPs that regulate splicing of conserved exons, we found that TDP-43 repressed the splicing of nonconserved cryptic exons, maintaining intron integrity. When TDP-43 was depleted from mouse embryonic stem cells, these cryptic exons were spliced into messenger RNAs, often disrupting their translation and promoting nonsense-mediated decay. Moreover, enforced repression of cryptic exons prevented cell death in TDP-43-deficient cells. Furthermore, repression of cryptic exons was impaired in ALS-FTD cases, suggesting that this splicing defect could potentially underlie TDP-43 proteinopathy.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Ling, Jonathan P -- Pletnikova, Olga -- Troncoso, Juan C -- Wong, Philip C -- P50AG05146/AG/NIA NIH HHS/ -- New York, N.Y. -- Science. 2015 Aug 7;349(6248):650-5. doi: 10.1126/science.aab0983.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, MD 21205-2196, USA. ; Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, MD 21205-2196, USA. Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21205-2196, USA. ; Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, MD 21205-2196, USA. Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205-2196, USA. wong@jhmi.edu.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26250685" target="_blank"〉PubMed〈/a〉
    Keywords: Amyotrophic Lateral Sclerosis/*genetics ; Animals ; Base Sequence ; Cells, Cultured ; Cysteine Endopeptidases/genetics ; DNA-Binding Proteins/genetics/*physiology ; Embryonic Stem Cells ; Exons/*genetics ; Frontotemporal Dementia/*genetics ; Gene Knockout Techniques ; HeLa Cells ; Humans ; Mice ; Molecular Sequence Data ; Protein Isoforms/genetics ; *RNA Splicing ; RNA Stability ; RNA, Messenger/metabolism ; Sequence Analysis, DNA
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  • 77
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    Unknown
    American Association for the Advancement of Science (AAAS)
    Publication Date: 2015-04-04
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Jacobs, Madeleine -- New York, N.Y. -- Science. 2015 Apr 3;348(6230):150. doi: 10.1126/science.348.6230.150.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉A former editor-in-chief of C&EN, Madeleine Jacobs was CEO of ACS until she retired at the end of 2014. For more on life and careers, visit sciencecareers.sciencemag.org. Send your story to SciCareerEditor@aaas.org.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25838387" target="_blank"〉PubMed〈/a〉
    Keywords: *Career Choice ; Chemistry ; Female ; Humans ; *Journalism ; *Women, Working
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  • 78
    Publication Date: 2015-07-18
    Description: Secretion of the cytokine interleukin-1beta (IL-1beta) by macrophages, a major driver of pathogenesis in atherosclerosis, requires two steps: Priming signals promote transcription of immature IL-1beta, and then endogenous "danger" signals activate innate immune signaling complexes called inflammasomes to process IL-1beta for secretion. Although cholesterol crystals are known to act as danger signals in atherosclerosis, what primes IL-1beta transcription remains elusive. Using a murine model of atherosclerosis, we found that cholesterol crystals acted both as priming and danger signals for IL-1beta production. Cholesterol crystals triggered neutrophils to release neutrophil extracellular traps (NETs). NETs primed macrophages for cytokine release, activating T helper 17 (TH17) cells that amplify immune cell recruitment in atherosclerotic plaques. Therefore, danger signals may drive sterile inflammation, such as that seen in atherosclerosis, through their interactions with neutrophils.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Warnatsch, Annika -- Ioannou, Marianna -- Wang, Qian -- Papayannopoulos, Venizelos -- MC_UP_1202/13/Medical Research Council/United Kingdom -- New York, N.Y. -- Science. 2015 Jul 17;349(6245):316-20. doi: 10.1126/science.aaa8064. Epub 2015 Jul 16.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Mill Hill Laboratory, Francis Crick Institute, London NW7 1AA, UK. ; Mill Hill Laboratory, Francis Crick Institute, London NW7 1AA, UK. veni.p@crick.ac.uk.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26185250" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Apolipoproteins E/genetics ; Atherosclerosis/*immunology ; Cells, Cultured ; Cholesterol/chemistry/immunology ; Disease Models, Animal ; Extracellular Traps/*immunology ; Humans ; Inflammasomes/immunology ; Inflammation/immunology ; Interleukin-1beta/*biosynthesis/genetics ; Macrophages/*immunology ; Mice ; Mice, Mutant Strains ; Neutrophils/*immunology ; Signal Transduction ; Th17 Cells/immunology ; Transcription, Genetic
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  • 79
    Publication Date: 2015-01-24
    Description: The 26S proteasome is a key player in eukaryotic protein quality control and in the regulation of numerous cellular processes. Here, we describe quantitative in situ structural studies of this highly dynamic molecular machine in intact hippocampal neurons. We used electron cryotomography with the Volta phase plate, which allowed high fidelity and nanometer precision localization of 26S proteasomes. We undertook a molecular census of single- and double-capped proteasomes and assessed the conformational states of individual complexes. Under the conditions of the experiment-that is, in the absence of proteotoxic stress-only 20% of the 26S proteasomes were engaged in substrate processing. The remainder was in the substrate-accepting ground state. These findings suggest that in the absence of stress, the capacity of the proteasome system is not fully used.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Asano, Shoh -- Fukuda, Yoshiyuki -- Beck, Florian -- Aufderheide, Antje -- Forster, Friedrich -- Danev, Radostin -- Baumeister, Wolfgang -- New York, N.Y. -- Science. 2015 Jan 23;347(6220):439-42. doi: 10.1126/science.1261197.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Molecular Structural Biology, Max-Planck Institute of Biochemistry, 82152 Martinsried, Germany. ; Department of Molecular Structural Biology, Max-Planck Institute of Biochemistry, 82152 Martinsried, Germany. baumeist@biochem.mpg.de.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25613890" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Cells, Cultured ; Hippocampus/*cytology/enzymology ; Neurons/*enzymology/*ultrastructure ; Proteasome Endopeptidase Complex/*chemistry ; Protein Conformation ; Rats ; Stress, Physiological
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  • 80
    Publication Date: 2015-09-26
    Description: Cellular senescence is a terminal stress-activated program controlled by the p53 and p16(INK4a) tumor suppressor proteins. A striking feature of senescence is the senescence-associated secretory phenotype (SASP), a pro-inflammatory response linked to tumor promotion and aging. We have identified the transcription factor GATA4 as a senescence and SASP regulator. GATA4 is stabilized in cells undergoing senescence and is required for the SASP. Normally, GATA4 is degraded by p62-mediated selective autophagy, but this regulation is suppressed during senescence, thereby stabilizing GATA4. GATA4 in turn activates the transcription factor NF-kappaB to initiate the SASP and facilitate senescence. GATA4 activation depends on the DNA damage response regulators ATM and ATR, but not on p53 or p16(INK4a). GATA4 accumulates in multiple tissues, including the aging brain, and could contribute to aging and its associated inflammation.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kang, Chanhee -- Xu, Qikai -- Martin, Timothy D -- Li, Mamie Z -- Demaria, Marco -- Aron, Liviu -- Lu, Tao -- Yankner, Bruce A -- Campisi, Judith -- Elledge, Stephen J -- AG009909/AG/NIA NIH HHS/ -- AG017242/AG/NIA NIH HHS/ -- AG046174/AG/NIA NIH HHS/ -- DP1 OD006849/OD/NIH HHS/ -- DP1OD006849/OD/NIH HHS/ -- GM44664/GM/NIGMS NIH HHS/ -- Howard Hughes Medical Institute/ -- New York, N.Y. -- Science. 2015 Sep 25;349(6255):aaa5612. doi: 10.1126/science.aaa5612.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Genetics, Harvard Medical School, Division of Genetics, Brigham and Women's Hospital, Howard Hughes Medical Institute, Boston, MA 02115, USA. ; Buck Institute for Research on Aging, Novato, CA 94945, USA. ; Department of Genetics, Harvard Medical School, Boston, MA 02115, USA. ; Department of Genetics, Harvard Medical School, Division of Genetics, Brigham and Women's Hospital, Howard Hughes Medical Institute, Boston, MA 02115, USA. selledge@genetics.med.harvard.edu.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26404840" target="_blank"〉PubMed〈/a〉
    Keywords: Aging/*genetics/metabolism ; Animals ; Ataxia Telangiectasia Mutated Proteins/metabolism ; Autophagy/*genetics ; Brain/metabolism ; Cell Aging/*genetics ; Cell Cycle/genetics ; Cells, Cultured ; Cyclin-Dependent Kinase Inhibitor p16 ; *DNA Damage ; Fibroblasts ; GATA4 Transcription Factor/genetics/*metabolism ; Gene Expression Profiling ; Humans ; Inflammation/*genetics ; Interleukin-1alpha/genetics/metabolism ; Mice ; Mice, Inbred C57BL ; MicroRNAs/genetics/metabolism ; NF-kappa B/metabolism ; Phenotype ; Promoter Regions, Genetic ; Tumor Necrosis Factor Receptor-Associated Peptides and ; Proteins/genetics/metabolism ; Tumor Suppressor Protein p53/metabolism
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  • 81
    Publication Date: 2015-02-24
    Description: Pancreatic beta cells lower insulin release in response to nutrient depletion. The question of whether starved beta cells induce macroautophagy, a predominant mechanism maintaining energy homeostasis, remains poorly explored. We found that, in contrast to many mammalian cells, macroautophagy in pancreatic beta cells was suppressed upon starvation. Instead, starved beta cells induced lysosomal degradation of nascent secretory insulin granules, which was controlled by protein kinase D (PKD), a key player in secretory granule biogenesis. Starvation-induced nascent granule degradation triggered lysosomal recruitment and activation of mechanistic target of rapamycin that suppressed macroautophagy. Switching from macroautophagy to insulin granule degradation was important to keep insulin secretion low upon fasting. Thus, beta cells use a PKD-dependent mechanism to adapt to nutrient availability and couple autophagy flux to secretory function.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Goginashvili, Alexander -- Zhang, Zhirong -- Erbs, Eric -- Spiegelhalter, Coralie -- Kessler, Pascal -- Mihlan, Michael -- Pasquier, Adrien -- Krupina, Ksenia -- Schieber, Nicole -- Cinque, Laura -- Morvan, Joelle -- Sumara, Izabela -- Schwab, Yannick -- Settembre, Carmine -- Ricci, Romeo -- New York, N.Y. -- Science. 2015 Feb 20;347(6224):878-82. doi: 10.1126/science.aaa2628.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institut de Genetique et de Biologie Moleculaire et Cellulaire (IGBMC), INSERM, CNRS, Universite de Strasbourg, 67404 Illkirch, France. ; Cell Biology and Biophysics Unit, European Molecular Biology Laboratory (EMBL), 69117 Heidelberg, Germany. ; Dulbecco Telethon Institute and Telethon Institute of Genetics and Medicine (TIGEM), 80131 Naples, Italy. ; Dulbecco Telethon Institute and Telethon Institute of Genetics and Medicine (TIGEM), 80131 Naples, Italy. Medical Genetics, Department of Medical and Translational Science Unit, Federico II University, Via Pansini 5, 80131 Naples, Italy. ; Institut de Genetique et de Biologie Moleculaire et Cellulaire (IGBMC), INSERM, CNRS, Universite de Strasbourg, 67404 Illkirch, France. Nouvel Hopital Civil, Laboratoire de Biochimie et de Biologie Moleculaire, Universite de Strasbourg, 67091 Strasbourg, France. romeo.ricci@igbmc.fr.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25700520" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; *Autophagy ; Cells, Cultured ; Fasting ; Humans ; Insulin/*secretion ; Insulin-Secreting Cells/*physiology/secretion/ultrastructure ; Mice ; Mice, Mutant Strains ; Mice, Transgenic ; Mitogen-Activated Protein Kinase 13/genetics ; Protein Kinase C/physiology ; Secretory Vesicles/*physiology/secretion
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  • 82
    Publication Date: 2015-02-24
    Description: Mutations in sunlight-induced melanoma arise from cyclobutane pyrimidine dimers (CPDs), DNA photoproducts that are typically created picoseconds after an ultraviolet (UV) photon is absorbed at thymine or cytosine. We found that in melanocytes, CPDs are generated for 〉3 hours after exposure to UVA, a major component of the radiation in sunlight and in tanning beds. These "dark CPDs" constitute the majority of CPDs and include the cytosine-containing CPDs that initiate UV-signature C--〉T mutations. Dark CPDs arise when UV-induced reactive oxygen and nitrogen species combine to excite an electron in fragments of the pigment melanin. This creates a quantum triplet state that has the energy of a UV photon but induces CPDs by energy transfer to DNA in a radiation-independent manner. Melanin may thus be carcinogenic as well as protective against cancer. These findings also validate the long-standing suggestion that chemically generated excited electronic states are relevant to mammalian biology.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4432913/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4432913/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Premi, Sanjay -- Wallisch, Silvia -- Mano, Camila M -- Weiner, Adam B -- Bacchiocchi, Antonella -- Wakamatsu, Kazumasa -- Bechara, Etelvino J H -- Halaban, Ruth -- Douki, Thierry -- Brash, Douglas E -- 2 P50 CA121974/CA/NCI NIH HHS/ -- P30 DK034989/DK/NIDDK NIH HHS/ -- P30 DK34989/DK/NIDDK NIH HHS/ -- P50 CA121974/CA/NCI NIH HHS/ -- New York, N.Y. -- Science. 2015 Feb 20;347(6224):842-7. doi: 10.1126/science.1256022.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, CT 06520, USA. ; Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, CT 06520, USA. Departamento de Bioquimica, Instituto de Quimica, Universidade de Sao Paulo, Sao Paulo 05513-970 SP, Brazil. ; Department of Dermatology, Yale University School of Medicine, New Haven, CT 06520, USA. ; Department of Chemistry, Fujita Health University School of Health Sciences, Toyoake, Aichi 470-1192, Japan. ; Departamento de Bioquimica, Instituto de Quimica, Universidade de Sao Paulo, Sao Paulo 05513-970 SP, Brazil. Departamento de Ciencias Exatas e da Terra, Universidade Federal de Sao Paulo, Diadema, Sao Paulo 09972-270 SP, Brazil. ; Department of Dermatology, Yale University School of Medicine, New Haven, CT 06520, USA. Yale Comprehensive Cancer Center, Yale University School of Medicine, New Haven, CT 06520, USA. ; INAC/LCIB UMR-E3 CEA-UJF/Commissariat a l'Energie Atomique (CEA), 38054 Grenoble Cedex 9, France. ; Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, CT 06520, USA. Yale Comprehensive Cancer Center, Yale University School of Medicine, New Haven, CT 06520, USA. douglas.brash@yale.edu.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25700512" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Cells, Cultured ; Cytosine/metabolism ; DNA/chemistry/genetics/*radiation effects ; DNA Damage/*genetics ; Energy Transfer ; Humans ; Melanins/chemistry/*metabolism ; Melanocytes/metabolism/*radiation effects ; Melanoma/*genetics ; Mice ; Mice, Inbred C57BL ; Mutagenesis ; Mutation ; Neoplasms, Radiation-Induced/*genetics ; Photons ; Pyrimidine Dimers/*metabolism ; Receptor, Melanocortin, Type 1/genetics ; Skin Neoplasms/*genetics ; Sunlight/adverse effects ; Thymine/metabolism ; Ultraviolet Rays
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  • 83
    Publication Date: 2016-02-26
    Description: Voltage-gated CaV1.2 channels (L-type calcium channel alpha1C subunits) are critical mediators of transcription-dependent neural plasticity. Whether these channels signal via the influx of calcium ion (Ca(2+)), voltage-dependent conformational change (VDeltaC), or a combination of the two has thus far been equivocal. We fused CaV1.2 to a ligand-gated Ca(2+)-permeable channel, enabling independent control of localized Ca(2+) and VDeltaC signals. This revealed an unexpected dual requirement: Ca(2+) must first mobilize actin-bound Ca(2+)/calmodulin-dependent protein kinase II, freeing it for subsequent VDeltaC-mediated accumulation. Neither signal alone sufficed to activate transcription. Signal order was crucial: Efficiency peaked when Ca(2+) preceded VDeltaC by 10 to 20 seconds. CaV1.2 VDeltaC synergistically augmented signaling by N-methyl-d-aspartate receptors. Furthermore, VDeltaC mistuning correlated with autistic symptoms in Timothy syndrome. Thus, nonionic VDeltaC signaling is vital to the function of CaV1.2 in synaptic and neuropsychiatric processes.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Li, Boxing -- Tadross, Michael R -- Tsien, Richard W -- New York, N.Y. -- Science. 2016 Feb 19;351(6275):863-7. doi: 10.1126/science.aad3647.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Neuroscience and Physiology and New York University Neuroscience Institute, New York, NY 10016, USA. ; Department of Molecular and Cellular Physiology, Beckman Center, School of Medicine, Stanford University, Stanford, CA 94305, USA. Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA. tadrossm@janelia.hhmi.org. ; Department of Neuroscience and Physiology and New York University Neuroscience Institute, New York, NY 10016, USA. Department of Molecular and Cellular Physiology, Beckman Center, School of Medicine, Stanford University, Stanford, CA 94305, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26912895" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Autistic Disorder/genetics/metabolism ; Calcium Channel Blockers/pharmacology ; Calcium Channels, L-Type/chemistry/*metabolism ; *Calcium Signaling ; Calcium-Calmodulin-Dependent Protein Kinase Type 2/*metabolism ; Cells, Cultured ; Cyclic AMP Response Element-Binding Protein/metabolism ; *Gene Expression Regulation ; HEK293 Cells ; Hippocampus/cytology ; Humans ; Long QT Syndrome/genetics/metabolism ; Neuronal Plasticity/*genetics ; Neurons/drug effects/*metabolism ; Nimodipine/pharmacology ; Protein Conformation/drug effects ; Rats ; Rats, Sprague-Dawley ; Receptors, N-Methyl-D-Aspartate/metabolism ; Synapses/metabolism ; Syndactyly/genetics/metabolism
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  • 84
    Publication Date: 2016-01-23
    Description: Differentiated macrophages can self-renew in tissues and expand long term in culture, but the gene regulatory mechanisms that accomplish self-renewal in the differentiated state have remained unknown. Here we show that in mice, the transcription factors MafB and c-Maf repress a macrophage-specific enhancer repertoire associated with a gene network that controls self-renewal. Single-cell analysis revealed that, in vivo, proliferating resident macrophages can access this network by transient down-regulation of Maf transcription factors. The network also controls embryonic stem cell self-renewal but is associated with distinct embryonic stem cell-specific enhancers. This indicates that distinct lineage-specific enhancer platforms regulate a shared network of genes that control self-renewal potential in both stem and mature cells.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Soucie, Erinn L -- Weng, Ziming -- Geirsdottir, Laufey -- Molawi, Kaaweh -- Maurizio, Julien -- Fenouil, Romain -- Mossadegh-Keller, Noushine -- Gimenez, Gregory -- VanHille, Laurent -- Beniazza, Meryam -- Favret, Jeremy -- Berruyer, Carole -- Perrin, Pierre -- Hacohen, Nir -- Andrau, J-C -- Ferrier, Pierre -- Dubreuil, Patrice -- Sidow, Arend -- Sieweke, Michael H -- P01AG036695/AG/NIA NIH HHS/ -- New York, N.Y. -- Science. 2016 Feb 12;351(6274):aad5510. doi: 10.1126/science.aad5510. Epub 2016 Jan 21.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Centre d'Immunologie de Marseille-Luminy, Universite Aix-Marseille, UM2, Campus de Luminy, Case 906, 13288 Marseille Cedex 09, France. INSERM, U1104, Marseille, France. CNRS, UMR 7280, Marseille, France. Centre de Recherche en Cancerologie de Marseille, INSERM (U1068), CNRS (U7258), Universite Aix-Marseille (UM105), Marseille, France. sieweke@ciml.univ-mrs.fr erinn.soucie@inserm.fr arend@stanford.edu. ; Department of Pathology, Stanford University, Stanford, CA 94305-5324, USA. ; Centre d'Immunologie de Marseille-Luminy, Universite Aix-Marseille, UM2, Campus de Luminy, Case 906, 13288 Marseille Cedex 09, France. INSERM, U1104, Marseille, France. CNRS, UMR 7280, Marseille, France. ; Centre d'Immunologie de Marseille-Luminy, Universite Aix-Marseille, UM2, Campus de Luminy, Case 906, 13288 Marseille Cedex 09, France. INSERM, U1104, Marseille, France. CNRS, UMR 7280, Marseille, France. Max-Delbruck-Centrum fur Molekulare Medizin in der Helmholtz-Gemeinschaft, 10 Robert-Rossle-Strasse, 13125 Berlin, Germany. ; Broad Institute of Harvard University and MIT, Cambridge, MA 02142, USA. ; Centre d'Immunologie de Marseille-Luminy, Universite Aix-Marseille, UM2, Campus de Luminy, Case 906, 13288 Marseille Cedex 09, France. INSERM, U1104, Marseille, France. CNRS, UMR 7280, Marseille, France. Institut de Genetique Moleculaire de Montpellier, CNRS UMR 5535, 1919 Route de Mende, 34293 Montpellier, France. ; Centre de Recherche en Cancerologie de Marseille, INSERM (U1068), CNRS (U7258), Universite Aix-Marseille (UM105), Marseille, France. ; Department of Pathology, Stanford University, Stanford, CA 94305-5324, USA. Department of Genetics, Stanford University, Stanford, CA 94305, USA. sieweke@ciml.univ-mrs.fr erinn.soucie@inserm.fr arend@stanford.edu. ; Centre d'Immunologie de Marseille-Luminy, Universite Aix-Marseille, UM2, Campus de Luminy, Case 906, 13288 Marseille Cedex 09, France. INSERM, U1104, Marseille, France. CNRS, UMR 7280, Marseille, France. Max-Delbruck-Centrum fur Molekulare Medizin in der Helmholtz-Gemeinschaft, 10 Robert-Rossle-Strasse, 13125 Berlin, Germany. sieweke@ciml.univ-mrs.fr erinn.soucie@inserm.fr arend@stanford.edu.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26797145" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Cell Differentiation/*genetics ; Cell Lineage/*genetics ; Cell Proliferation ; Cells, Cultured ; Down-Regulation ; Embryonic Stem Cells/*cytology ; Enhancer Elements, Genetic/*physiology ; *Gene Expression Regulation ; Gene Regulatory Networks ; Macrophages/*cytology ; MafB Transcription Factor/metabolism ; Mice ; Proto-Oncogene Proteins c-maf/metabolism ; Single-Cell Analysis ; Transcriptional Activation
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  • 85
    Publication Date: 2015-11-07
    Description: In a classical view of hematopoiesis, the various blood cell lineages arise via a hierarchical scheme starting with multipotent stem cells that become increasingly restricted in their differentiation potential through oligopotent and then unipotent progenitors. We developed a cell-sorting scheme to resolve myeloid (My), erythroid (Er), and megakaryocytic (Mk) fates from single CD34(+) cells and then mapped the progenitor hierarchy across human development. Fetal liver contained large numbers of distinct oligopotent progenitors with intermingled My, Er, and Mk fates. However, few oligopotent progenitor intermediates were present in the adult bone marrow. Instead, only two progenitor classes predominate, multipotent and unipotent, with Er-Mk lineages emerging from multipotent cells. The developmental shift to an adult "two-tier" hierarchy challenges current dogma and provides a revised framework to understand normal and disease states of human hematopoiesis.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Notta, Faiyaz -- Zandi, Sasan -- Takayama, Naoya -- Dobson, Stephanie -- Gan, Olga I -- Wilson, Gavin -- Kaufmann, Kerstin B -- McLeod, Jessica -- Laurenti, Elisa -- Dunant, Cyrille F -- McPherson, John D -- Stein, Lincoln D -- Dror, Yigal -- Dick, John E -- Canadian Institutes of Health Research/Canada -- Medical Research Council/United Kingdom -- Wellcome Trust/United Kingdom -- New York, N.Y. -- Science. 2016 Jan 8;351(6269):aab2116. doi: 10.1126/science.aab2116. Epub 2015 Nov 5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Princess Margaret Cancer Centre, University Health Network, University of Toronto, Toronto, Ontario, Canada. Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada. ; Princess Margaret Cancer Centre, University Health Network, University of Toronto, Toronto, Ontario, Canada. ; Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada. Ontario Institute for Cancer Research, Toronto, Ontario, Canada. ; Wellcome Trust, Medical Research Council Cambridge Stem Cell Institute, Department of Haematology, University of Cambridge, Cambridge, UK. ; Ecole Polytechnique Federale de Lausanne, LMC, Station 12, Lausanne, CH-1015, Switzerland. ; Medical Biophysics, University of Toronto, Toronto, Ontario, Canada. Ontario Institute for Cancer Research, Toronto, Ontario, Canada. ; The Hospital for Sick Children Research Institute, University of Toronto, Ontario, Canada. ; Princess Margaret Cancer Centre, University Health Network, University of Toronto, Toronto, Ontario, Canada. Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada. jdick@uhnres.utoronto.ca.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26541609" target="_blank"〉PubMed〈/a〉
    Keywords: Adult ; Antigens, CD34/analysis ; Cell Lineage/genetics/*physiology ; Cell Separation ; Cells, Cultured ; Erythroid Cells/*cytology ; Fetal Blood/cytology ; Gene Expression Profiling ; Hematopoiesis/genetics/*physiology ; Humans ; Liver/cytology/embryology ; Megakaryocyte Progenitor Cells/*cytology ; Megakaryocytes/*cytology ; Multipotent Stem Cells/cytology ; Myeloid Cells/*cytology ; Transcription, Genetic
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  • 86
    Publication Date: 2016-09-02
    Description: Effective differentiation of prochiral carbon–hydrogen (C–H) bonds on a single methylene carbon via asymmetric metal insertion remains a challenge. Here, we report the discovery of chiral acetyl-protected aminoethyl quinoline ligands that enable asymmetric palladium insertion into prochiral C–H bonds on a single methylene carbon center. We apply these palladium complexes to catalytic enantioselective functionalization of β-methylene C–H bonds in aliphatic amides. Using bidentate ligands to accelerate C–H activation of otherwise unreactive monodentate substrates is crucial for outcompeting the background reaction driven by substrate-directed cyclopalladation, thereby avoiding erosion of enantioselectivity. The potential of ligand acceleration in C–H activation is also demonstrated by enantioselective β-C–H arylation of simple carboxylic acids without installing directing groups.
    Keywords: Chemistry
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  • 87
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2017-08-11
    Description: Vicinal diamines are a common structural motif in bioactive natural products, therapeutic agents, and molecular catalysts, motivating the continuing development of efficient, selective, and sustainable technologies for their preparation. We report an operationally simple and environmentally friendly protocol that converts alkenes and sodium azide—both readily available feedstocks—to 1,2-diazides. Powered by electricity and catalyzed by Earth-abundant manganese, this transformation proceeds under mild conditions and exhibits exceptional substrate generality and functional group compatibility. Using standard protocols, the resultant 1,2-diazides can be smoothly reduced to vicinal diamines in a single step, with high chemoselectivity. Mechanistic studies are consistent with metal-mediated azidyl radical transfer as the predominant pathway, enabling dual carbon-nitrogen bond formation.
    Keywords: Chemistry
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  • 88
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2017-08-18
    Keywords: Chemistry
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  • 89
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2017-08-18
    Keywords: Chemistry
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  • 90
    Publication Date: 2017-08-18
    Description: In methanogenic archaea, the carbon dioxide (CO 2 ) fixation and methane-forming steps are linked through the heterodisulfide reductase (HdrABC)–[NiFe]-hydrogenase (MvhAGD) complex that uses flavin-based electron bifurcation to reduce ferredoxin and the heterodisulfide of coenzymes M and B. Here, we present the structure of the native heterododecameric HdrABC-MvhAGD complex at 2.15-angstrom resolution. HdrB contains two noncubane [4Fe-4S] clusters composed of fused [3Fe-4S]-[2Fe-2S] units sharing 1 iron (Fe) and 1 sulfur (S), which were coordinated at the CCG motifs. Soaking experiments showed that the heterodisulfide is clamped between the two noncubane [4Fe-4S] clusters and homolytically cleaved, forming coenzyme M and B bound to each iron. Coenzymes are consecutively released upon one-by-one electron transfer. The HdrABC-MvhAGD atomic model serves as a structural template for numerous HdrABC homologs involved in diverse microbial metabolic pathways.
    Keywords: Chemistry
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  • 91
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2017-08-25
    Keywords: Chemistry
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  • 92
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2017-09-01
    Keywords: Chemistry
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  • 93
    Publication Date: 2017-08-25
    Description: Current catalytic processes involving carbon-carbon bond activation rely on -unsaturated coupling partners. Exploiting the concept of transfer hydrogenative coupling, we report a ruthenium(0)-catalyzed cycloaddition of benzocyclobutenones that functionalizes two adjacent saturated diol carbon-hydrogen bonds. These regio- and diastereoselective processes enable convergent construction of type II polyketide substructures.
    Keywords: Chemistry
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  • 94
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2017-08-25
    Keywords: Chemistry
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  • 95
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2017-08-25
    Description: We imaged the interfacial structure and dynamics of water in a microscopically confined geometry, in three dimensions and on millisecond time scales, with a structurally illuminated wide-field second harmonic microscope. The second harmonic images reported on the orientational order of interfacial water, induced by charge-dipole interactions between water molecules and surface charges. The images were converted into surface potential maps. Spatially resolved surface acid dissociation constant (p K a,s ) values were determined for the silica deprotonation reaction by following pH-induced chemical changes on the curved and confined surfaces of a glass microcapillary immersed in aqueous solutions. These values ranged from 2.3 to 10.7 along the wall of a single capillary because of surface heterogeneities. Water molecules that rotate along an oscillating external electric field were also imaged.
    Keywords: Chemistry
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  • 96
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2017-08-25
    Keywords: Chemistry
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  • 97
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2017-09-01
    Keywords: Chemistry
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  • 98
    Publication Date: 2017-09-01
    Description: Copper ions exchanged into zeolites are active for the selective catalytic reduction (SCR) of nitrogen oxides (NO x ) with ammonia (NH 3 ), but the low-temperature rate dependence on copper (Cu) volumetric density is inconsistent with reaction at single sites. We combine steady-state and transient kinetic measurements, x-ray absorption spectroscopy, and first-principles calculations to demonstrate that under reaction conditions, mobilized Cu ions can travel through zeolite windows and form transient ion pairs that participate in an oxygen (O 2 )–mediated Cu I -〉Cu II redox step integral to SCR. Electrostatic tethering to framework aluminum centers limits the volume that each ion can explore and thus its capacity to form an ion pair. The dynamic, reversible formation of multinuclear sites from mobilized single atoms represents a distinct phenomenon that falls outside the conventional boundaries of a heterogeneous or homogeneous catalyst.
    Keywords: Chemistry
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  • 99
    Publication Date: 2017-09-01
    Description: All-c is -multifluorinated cycloalkanes exhibit intriguing electronic properties. In particular, they display extremely high dipole moments perpendicular to the aliphatic ring, making them highly desired motifs in material science. Very few such motifs have been prepared, as their syntheses require multistep sequences from diastereoselectively prefunctionalized precursors. Herein we report a synthetic strategy to access these valuable materials via the rhodium–cyclic (alkyl)(amino)carbene (CAAC)–catalyzed hydrogenation of readily available fluorinated arenes in hexane. This route enables the scalable single-step preparation of an abundance of multisubstituted and multifluorinated cycloalkanes, including all- cis -1,2,3,4,5,6-hexafluorocyclohexane as well as cis-configured fluorinated aliphatic heterocycles.
    Keywords: Chemistry
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2016-11-04
    Description: Author: Jake Yeston
    Keywords: Chemistry
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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