Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title><jats:p>Theoretical modelling predicts very unusual structures and properties of materials at extreme pressure and temperature conditions<jats:sup>1,2</jats:sup>. Hitherto, their synthesis and investigation above 200 gigapascals have been hindered both by the technical complexity of ultrahigh-pressure experiments and by the absence of relevant in situ methods of materials analysis. Here we report on a methodology developed to enable experiments at static compression in the terapascal regime with laser heating. We apply this method to realize pressures of about 600 and 900 gigapascals in a laser-heated double-stage diamond anvil cell<jats:sup>3</jats:sup>, producing a rhenium–nitrogen alloy and achieving the synthesis of rhenium nitride Re<jats:sub>7</jats:sub>N<jats:sub>3</jats:sub>—which, as our theoretical analysis shows, is only stable under extreme compression. Full chemical and structural characterization of the materials, realized using synchrotron single-crystal X-ray diffraction on microcrystals in situ, demonstrates the capabilities of the methodology to extend high-pressure crystallography to the terapascal regime.</jats:p>

<jats:title>Abstract</jats:title><jats:p>The RNA world concept<jats:sup>1</jats:sup> is one of the most fundamental pillars of the origin of life theory<jats:sup>2–4</jats:sup>. It predicts that life evolved from increasingly complex self-replicating RNA molecules<jats:sup>1,2,4</jats:sup>. The question of how this RNA world then advanced to the next stage, in which proteins became the catalysts of life and RNA reduced its function predominantly to information storage, is one of the most mysterious chicken-and-egg conundrums in evolution<jats:sup>3–5</jats:sup>. Here we show that non-canonical RNA bases, which are found today in transfer and ribosomal RNAs<jats:sup>6,7</jats:sup>, and which are considered to be relics of the RNA world<jats:sup>8–12</jats:sup>, are able to establish peptide synthesis directly on RNA. The discovered chemistry creates complex peptide-decorated RNA chimeric molecules, which suggests the early existence of an RNA–peptide world<jats:sup>13</jats:sup> from which ribosomal peptide synthesis<jats:sup>14</jats:sup> may have emerged<jats:sup>15,16</jats:sup>. The ability to grow peptides on RNA with the help of non-canonical vestige nucleosides offers the possibility of an early co-evolution of covalently connected RNAs and peptides<jats:sup>13,17,18</jats:sup>, which then could have dissociated at a higher level of sophistication to create the dualistic nucleic acid–protein world that is the hallmark of all life on Earth.</jats:p>

<jats:title>Abstract</jats:title><jats:p>Comprehensive assessments of species’ extinction risks have documented the extinction crisis<jats:sup>1</jats:sup> and underpinned strategies for reducing those risks<jats:sup>2</jats:sup>. Global assessments reveal that, among tetrapods, 40.7% of amphibians, 25.4% of mammals and 13.6% of birds are threatened with extinction<jats:sup>3</jats:sup>. Because global assessments have been lacking, reptiles have been omitted from conservation-prioritization analyses that encompass other tetrapods<jats:sup>4–7</jats:sup>. Reptiles are unusually diverse in arid regions, suggesting that they may have different conservation needs<jats:sup>6</jats:sup>. Here we provide a comprehensive extinction-risk assessment of reptiles and show that at least 1,829 out of 10,196 species (21.1%) are threatened—confirming a previous extrapolation<jats:sup>8</jats:sup> and representing 15.6 billion years of phylogenetic diversity. Reptiles are threatened by the same major factors that threaten other tetrapods—agriculture, logging, urban development and invasive species—although the threat posed by climate change remains uncertain. Reptiles inhabiting forests, where these threats are strongest, are more threatened than those in arid habitats, contrary to our prediction. Birds, mammals and amphibians are unexpectedly good surrogates for the conservation of reptiles, although threatened reptiles with the smallest ranges tend to be isolated from other threatened tetrapods. Although some reptiles—including most species of crocodiles and turtles—require urgent, targeted action to prevent extinctions, efforts to protect other tetrapods, such as habitat preservation and control of trade and invasive species, will probably also benefit many reptiles.</jats:p>

<jats:title>Abstract</jats:title><jats:p>Many policies attempt to help extremely poor households build sustainable sources of income. Although economic interventions have predominated historically<jats:sup>1,2</jats:sup>, psychosocial support has attracted substantial interest<jats:sup>3–5</jats:sup>, particularly for its potential cost-effectiveness. Recent evidence has shown that multi-faceted ‘graduation’ programmes can succeed in generating sustained changes<jats:sup>6,7</jats:sup>. Here we show that a multi-faceted intervention can open pathways out of extreme poverty by relaxing capital and psychosocial constraints. We conducted a four-arm randomized evaluation among extremely poor female beneficiaries already enrolled in a national cash transfer government programme in Niger. The three treatment arms included group savings promotion, coaching and entrepreneurship training, and then added either a lump-sum cash grant, psychosocial interventions, or both the cash grant and psychosocial interventions. All three arms generated positive effects on economic outcomes and psychosocial well-being, but there were notable differences in the pathways and the timing of effects. Overall, the arms with psychosocial interventions were the most cost-effective, highlighting the value of including well-designed psychosocial components in government-led multi-faceted interventions for the extreme poor.</jats:p>

<jats:title>Abstract</jats:title><jats:p>Many age-dependent neurodegenerative diseases, such as Alzheimer’s and Parkinson’s, are characterized by abundant inclusions of amyloid filaments. Filamentous inclusions of the proteins tau, amyloid-β, α-synuclein and transactive response DNA-binding protein (TARDBP; also known as TDP-43) are the most common<jats:sup>1,2</jats:sup>. Here we used structure determination by cryogenic electron microscopy to show that residues 120–254 of the lysosomal type II transmembrane protein 106B (TMEM106B) also form amyloid filaments in human brains. We determined the structures of TMEM106B filaments from a number of brain regions of 22 individuals with abundant amyloid deposits, including those resulting from sporadic and inherited tauopathies, amyloid-β amyloidoses, synucleinopathies and TDP-43 proteinopathies, as well as from the frontal cortex of 3 individuals with normal neurology and no or only a few amyloid deposits. We observed three TMEM106B folds, with no clear relationships between folds and diseases. TMEM106B filaments correlated with the presence of a 29-kDa sarkosyl-insoluble fragment and globular cytoplasmic inclusions, as detected by an antibody specific to the carboxy-terminal region of TMEM106B. The identification of TMEM106B filaments in the brains of older, but not younger, individuals with normal neurology indicates that they form in an age-dependent manner.</jats:p>