Volume 524 Number 7566

Editorials

FDA vulnerability revealed p.387

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

doi: 10.1038/524387a

News

News Features

News & Views

Superlattice substitution p.418

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

doi: 10.1038/524418a

Surviving import failure p.419

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

doi: 10.1038/nature14644

Lipid gymnastics p.420

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

doi: 10.1038/nature15202

Positrons ride the wave p.422

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

doi: 10.1038/524422a

Gene transfer in complex cells p.423

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

doi: 10.1038/nature15205

A stable narrow-band X-ray laser p.424

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

doi: 10.1038/524424a

Articles

Endosymbiotic origin and differential loss of eukaryotic genes p.427

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.

doi: 10.1038/nature14963

Letters

Atomic inner-shell laser at 1.5-ångström wavelength pumped by an X-ray free-electron laser p.446

Since the invention of the first lasers in the visible-light region, research has aimed to produce short-wavelength lasers that generate coherent X-rays; the shorter the wavelength, the better the imaging resolution of the laser and the shorter the pulse duration, leading to better temporal resolution in probe measurements. Recently, free-electron lasers based on self-amplified spontaneous emission have made it possible to generate a hard-X-ray laser (that is, the photon energy is of the order of ten kiloelectronvolts) in an ångström-wavelength regime, enabling advances in fields from ultrafast X-ray spectrosopy to X-ray quantum optics. An atomic laser based on neon atoms and pumped by a soft-X-ray (that is, a photon energy of less than one kiloelectronvolt) free-electron laser has been achieved at a wavelength of 14 nanometres. Here, we use a copper target and report a hard-X-ray inner-shell atomic laser operating at a wavelength of 1.5 ångströms. X-ray free-electron laser pulses with an intensity of about 1019 watts per square centimetre tuned to the copper K-absorption edge produced sufficient population inversion to generate strong amplified spontaneous emission on the copper Kα lines. Furthermore, we operated the X-ray free-electron laser source in a two-colour mode, with one colour tuned for pumping and the other for the seed (starting) light for the laser.

doi: 10.1038/nature14894

Substitutional doping in nanocrystal superlattices p.450

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.

doi: 10.1038/nature14872

Western US intermountain seismicity caused by changes in upper mantle flow p.458

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.

doi: 10.1038/nature14867

The pre-vertebrate origins of neurogenic placodes p.462

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.

doi: 10.1038/nature14657

Sidekick 2 directs formation of a retinal circuit that detects differential motion p.466

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.

doi: 10.1038/nature14682

SEC14L2 enables pan-genotype HCV replication in cell culture p.471

Hepatitis C virus cannot replicate in cell culture unless it possesses adaptive mutations; here, expression of cellular factor SEC14L2 is shown to allow replication of diverse hepatitis C virus genotypes in several hepatoma cell lines by enhancing vitamin E-mediated protection against lipid peroxidation.

doi: 10.1038/nature14899

A cytosolic network suppressing mitochondria-mediated proteostatic stress and cell death p.481

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.

doi: 10.1038/nature14859

Mistargeted mitochondrial proteins activate a proteostatic response in the cytosol p.485

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.

doi: 10.1038/nature14951

Structural basis for stop codon recognition in eukaryotes p.493

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.

doi: 10.1038/nature14896

Conformational dynamics of a class C G-protein-coupled receptor p.497

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.

doi: 10.1038/nature14679