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Volume 524 Issue 7566, 27 August 2015

Gold nanocrystals visualized doping a semiconductor superlattice without disrupting the ordered arrays. Doping � widely used in semiconductors, diluted magnetic materials and phosphors � is a process in which extraneous atoms are introduced into a host material in order to improve or create new electronic, magnetic and optical properties. Christopher Murray and colleagues introduce the concept of substitutional doping in nanocrystal superlattices, where artificial atoms (uniform nanocrystals) are used instead of atoms. They demonstrate the random incorporation of gold nanocrystals into a semiconductor (CdSe or PbSe) nanocrystal superlattice, where one nanocrystal can be replaced with another of the same size but different composition. The conductivity of the resulting material is modulated by metallic percolation pathways controlled by the density and distribution of the dopants. The use of self-assembly means that this novel technique should be widely applicable to a range of different materials and compositions. Cover image: Ella Marushchenko.

Editorial

  • A politically charged advisory committee meeting may have tipped the scales in favour of a mildly effective female libido drug.

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Comment

  • California's current extreme drought must be a lesson for managing water in a warmer, more densely populated world, say Amir AghaKouchak and colleagues.

    • Amir AghaKouchak
    • David Feldman
    • Jay Lund
    Comment
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Books & Arts

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Correspondence

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News & Views

  • What happens if some of the particles of a superlattice — an array of identical nanoscale crystals — are replaced with foreign ones? It emerges that the properties of superlattices can be radically altered in this way. See Letter p.450

    • Daniel Vanmaekelbergh
    News & Views
  • Two studies reveal that dysfunction in organelles called mitochondria causes the toxic accumulation of mitochondrial proteins in the cell's cytosolic fluid, and identify ways in which damage is mitigated. See Letters p.481 & p.485

    • Cole M. Haynes
    News & Views
  • Crystal structures of the bacterial protein PglK uncover structural features that suggest how the protein 'flips' lipid-bound oligosaccharide molecules from one side of the cell membrane to the other. See Article p.433

    • Alice Verchère
    • Anant K. Menon
    News & Views
  • Experiments reveal that positrons — the antimatter equivalents of electrons — can be rapidly accelerated using a plasma wave. The findings pave the way to high-energy electron–positron particle colliders. See Letter p.442

    • Philippe Piot
    News & Views
  • A comparative genomic study shows that, during evolution, nucleus-containing cells acquired DNA from bacteria primarily by endosymbiosis — the uptake and integration of one cell by another. See Article p.427

    • John M. Archibald
    News & Views
  • An atomic laser operating at the shortest wavelength yet achieved has been created by bombarding a copper foil with two X-ray pulses tuned to slightly different energies. The results may lead to ultrastable X-ray lasers. See Letter p.446

    • Linda Young
    News & Views
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Article

  • Eukaryotes acquired their prokaryotic genes in two episodes of evolutionary influx corresponding to the origin of mitochondria and plastids, respectively, followed by extensive differential gene loss, uncovering a massive imprint of endosymbiosis in the nuclear genomes of complex cells.

    • Chuan Ku
    • Shijulal Nelson-Sathi
    • William F. Martin
    Article
  • The X-ray crystal structure of the ABC transporter PglK, which facilitates the flipping of lipid-linked oligosaccharides (LLOs) in C. jejuni, in inward- and outward-facing states is solved; the structures and follow-up biochemical experiments support an unprecedented mechanism in which the polyprenyl tail of LLO remains partially embedded in the lipid bilayer, and the pyrophosphate-oligosaccharide head group is flipped into the outward-facing cavity after ATP is hydrolysed.

    • Camilo Perez
    • Sabina Gerber
    • Kaspar P. Locher
    Article
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Letter

  • A particle accelerator that is two orders of magnitude more efficient than conventional radio-frequency accelerators is described in which positrons (rather than electrons) at the front of a bunch transfer their energy to a substantial number of positrons at the rear of the same bunch by exciting a wakefield in the plasma.

    • S. Corde
    • E. Adli
    • G. Yocky
    Letter
  • Substitutional atomic doping is a process by which atomic defects are introduced into a host material, altering its properties; substitutional doping of cadmium selenide or lead selenide nanocrystal lattices with gold nanocrystals has now been achieved, the key being to ensure that the dopant nanocrystals are similar in size to the host nanocrystals.

    • Matteo Cargnello
    • Aaron C. Johnston-Peck
    • Christopher B. Murray
    Letter
  • A new method for catalysing the cross-coupling of two different aryl electrophiles is described; the principle of this method, which involves cooperation between two metal catalysts that are selective towards different substrates, should be generally useful in catalysis.

    • Laura K. G. Ackerman
    • Matthew M. Lovell
    • Daniel J. Weix
    Letter
  • Results from mantle flow models reveal a relationship between seismicity away from the plate boundary in the western United States and the rate change of the vertical normal stress from mantle flow, showing that mantle flow plays an important part in shaping topography, tectonics and seismic hazard within such intraplate settings.

    • Thorsten W. Becker
    • Anthony R. Lowry
    • Chunquan Yu
    Letter
  • A study showing that tunicates possess a proto-placodal ectoderm that produces neurons with dual neurosecretory and chemosensory function, which may represent the ancestral origin of placode-derived neurons in vertebrates.

    • Philip Barron Abitua
    • T. Blair Gainous
    • Michael Levine
    Letter
  • The mouse retinal ganglion cell type known as the W3B-RGC, which detects motion of objects against a moving background, is shown to receive strong specific and excitatory input from amacrine cells expressing vesicular glutamine transporter 3; this selective connection is mediated by homophilic interactions of the recognition molecule sidekick 2 (Sdk2), which is expressed on both cells, and disruption of this connection affects object motion detection in W3B-RGCs.

    • Arjun Krishnaswamy
    • Masahito Yamagata
    • Joshua R. Sanes
    Letter
  • A new pathway of mitochondria-mediated cell death termed mitochondrial precursor over-accumulation stress (mPOS) is identified that could explain the link between mitochondrial dysfunction and misfolding of cytosolic proteins during ageing and disease; the pathway is triggered not only by mutations affecting the core protein import machineries, but also by conditions that interfere with mitochondrial inner membrane integrity and function, and a large network of genes that suppress mPOS in favour of cell survival is also identified.

    • Xiaowen Wang
    • Xin Jie Chen
    Letter
  • Mitochondrial dysfunction and cellular protein homeostasis failure are hallmarks of many diseases and age-associated pathologies; this study shows that the mitochondrial import defect of nuclear-encoded proteins triggers a cellular pathway, termed unfolded protein response activated by mistargeting of proteins (UPRam), that acts to minimize the stress caused by non-imported mitochondrial precursor proteins in order to sustain cellular protein homeostasis and organismal fitness.

    • Lidia Wrobel
    • Ulrike Topf
    • Agnieszka Chacinska
    Letter
  • All eukaryotes utilize a single termination factor, eRF1, to halt translation when the ribosome encounters one of three possible stop codons; here electron cryo-microscopy structures of ribosome–eRF1 complexes in the process of recognizing each stop codon reveal how stop codons are discriminated from sense codons.

    • Alan Brown
    • Sichen Shao
    • V. Ramakrishnan
    Letter
  • smFRET is used to probe the activation mechanism of two full-length mammalian glutamate receptors, revealing that the extracellular ligand-binding domains of these G-protein-coupled receptors interconvert between three confirmations (resting, activated and a short-lived intermediate state), and that the efficacy of an orthosteric agonist correlates with the degree of occupancy of the active state.

    • Reza Vafabakhsh
    • Joshua Levitz
    • Ehud Y. Isacoff
    Letter
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Corrigendum

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Erratum

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Technology Feature

  • The United Kingdom aims to sequence 100,000 human genomes by 2017. But screening them for disease-causing variants will require innovative software.

    • Vivien Marx

    Collection:

    Technology Feature
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Column

  • Seek and cultivate professional relationships to advance your career, says Peter Fiske.

    • Peter Fiske
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Q&A

  • Arie Meir describes his route from a PhD in biophysics to a leadership position assessing projects for the philanthropic arm of Google.

    • Monya Baker
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Brief Communications Arising

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