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  • 1
    Online Resource
    Online Resource
    American Association for the Advancement of Science (AAAS) ; 2021
    In:  Science Vol. 373, No. 6553 ( 2021-07-23), p. 425-430
    In: Science, American Association for the Advancement of Science (AAAS), Vol. 373, No. 6553 ( 2021-07-23), p. 425-430
    Abstract: The Crab Nebula is a bright source of gamma rays powered by the Crab Pulsar’s rotational energy through the formation and termination of a relativistic electron-positron wind. We report the detection of gamma rays from this source with energies from 5 × 10 −4 to 1.1 peta–electron volts with a spectrum showing gradual steepening over three energy decades. The ultrahigh-energy photons imply the presence of a peta–electron volt electron accelerator (a pevatron) in the nebula, with an acceleration rate exceeding 15% of the theoretical limit. We constrain the pevatron’s size between 0.025 and 0.1 parsecs and the magnetic field to ≈110 microgauss. The production rate of peta–electron volt electrons, 2.5 × 10 36 ergs per second, constitutes 0.5% of the pulsar spin-down luminosity, although we cannot exclude a contribution of peta–electron volt protons to the production of the highest-energy gamma rays.
    Type of Medium: Online Resource
    ISSN: 0036-8075 , 1095-9203
    RVK:
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    Language: English
    Publisher: American Association for the Advancement of Science (AAAS)
    Publication Date: 2021
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  • 2
    Online Resource
    Online Resource
    Proceedings of the National Academy of Sciences ; 2021
    In:  Proceedings of the National Academy of Sciences Vol. 118, No. 38 ( 2021-09-21)
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 118, No. 38 ( 2021-09-21)
    Abstract: Natural spider silk with extraordinary mechanical properties is typically spun from more than one type of spidroin. Although the main components of various spider silks have been widely studied, little is known about the molecular role of the minor silk components in spidroin self-assembly and fiber formation. Here, we show that the minor component of spider eggcase silk, TuSp2, not only accelerates self-assembly but remarkably promotes molecular chain alignment of spidroins upon physical shearing. NMR structure of the repetitive domain of TuSp2 reveals that its dimeric structure with unique charged surface serves as a platform to recruit different domains of the main eggcase component TuSp1. Artificial fiber spun from the complex between TuSp1 and TuSp2 minispidroins exhibits considerably higher strength and Young’s modulus than its native counterpart. These results create a framework for rationally designing silk biomaterials based on distinct roles of silk components.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    RVK:
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    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2021
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  • 3
    In: Brain, Oxford University Press (OUP), Vol. 146, No. 8 ( 2023-08-01), p. 3373-3391
    Abstract: GGC repeat expansion in the 5′ untranslated region (UTR) of NOTCH2NLC is associated with a broad spectrum of neurological disorders, especially neuronal intranuclear inclusion disease (NIID). Studies have found that GGC repeat expansion in NOTCH2NLC induces the formation of polyglycine (polyG)-containing protein, which is involved in the formation of neuronal intranuclear inclusions. However, the mechanism of neurotoxicity induced by NOTCH2NLC GGC repeats is unclear. Here, we used NIID patient-specific induced pluripotent stem cell (iPSC)-derived 3D cerebral organoids (3DCOs) and cellular models to investigate the pathophysiological mechanisms of NOTCH2NLC GGC repeat expansion. IPSC-derived 3DCOs and cellular models showed the deposition of polyG-containing intranuclear inclusions. The NOTCH2NLC GGC repeats could induce the upregulation of autophagic flux, enhance integrated stress response and activate EIF2α phosphorylation. Bulk RNA sequencing for iPSC-derived neurons and single-cell RNA sequencing (scRNA-seq) for iPSC-derived 3DCOs revealed that NOTCH2NLC GGC repeats may be associated with dysfunctions in ribosome biogenesis and translation. Moreover, NOTCH2NLC GGC repeats could induce the NPM1 nucleoplasm translocation, increase nucleolar stress, impair ribosome biogenesis and induce ribosomal RNA sequestration, suggesting dysfunction of membraneless organelles in the NIID cellular model. Dysfunctions in ribosome biogenesis and phosphorylated EIF2α and the resulting increase in the formation of G3BP1-positive stress granules may together lead to whole-cell translational inhibition, which may eventually cause cell death. Interestingly, scRNA-seq revealed that NOTCH2NLC GGC repeats may be associated with a significantly decreased proportion of immature neurons while 3DCOs were developing. Together, our results underscore the value of patient-specific iPSC-derived 3DCOs in investigating the mechanisms of polyG diseases, especially those caused by repeats in human-specific genes.
    Type of Medium: Online Resource
    ISSN: 0006-8950 , 1460-2156
    RVK:
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2023
    detail.hit.zdb_id: 1474117-9
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  • 4
    Online Resource
    Online Resource
    Oxford University Press (OUP) ; 2020
    In:  Brain Vol. 143, No. 6 ( 2020-06-01), p. e47-e47
    In: Brain, Oxford University Press (OUP), Vol. 143, No. 6 ( 2020-06-01), p. e47-e47
    Type of Medium: Online Resource
    ISSN: 0006-8950 , 1460-2156
    RVK:
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2020
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    SSG: 12
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  • 5
    Online Resource
    Online Resource
    Proceedings of the National Academy of Sciences ; 2018
    In:  Proceedings of the National Academy of Sciences Vol. 115, No. 9 ( 2018-02-27), p. 2210-2215
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 115, No. 9 ( 2018-02-27), p. 2210-2215
    Abstract: Growing evidence shows that generation of reactive oxygen species (ROS) derived from antibiotic-induced metabolic perturbation contribute to antibiotic lethality. However, our knowledge of the mechanisms by which antibiotic-induced oxidative stress actually kills cells remains elusive. Here, we show that oxidation of dCTP underlies ROS-mediated antibiotic lethality via induction of DNA double-strand breaks (DSBs). Deletion of mazG -encoded 5-OH-dCTP–specific pyrophosphohydrolase potentiates antibiotic killing of stationary-phase mycobacteria, but did not affect antibiotic efficacy in exponentially growing cultures. Critically, the effect of mazG deletion on potentiating antibiotic killing is associated with antibiotic-induced ROS and accumulation of 5-OH-dCTP. Independent lines of evidence presented here indicate that the increased level of DSBs observed in the ΔmazG mutant is a dead-end event accounting for enhanced antibiotic killing. Moreover, we provided genetic evidence that 5-OH-dCTP is incorporated into genomic DNA via error-prone DNA polymerase DnaE2 and repair of 5-OH-dC lesions via the endonuclease Nth leads to the generation of lethal DSBs. This work provides a mechanistic view of ROS-mediated antibiotic lethality in stationary phase and may have broad implications not only with respect to antibiotic lethality but also to the mechanism of stress-induced mutagenesis in bacteria.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    RVK:
    RVK:
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2018
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  • 6
    Online Resource
    Online Resource
    Proceedings of the National Academy of Sciences ; 2016
    In:  Proceedings of the National Academy of Sciences Vol. 113, No. 18 ( 2016-05-03), p. 4964-4969
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 113, No. 18 ( 2016-05-03), p. 4964-4969
    Abstract: The maize opaque2 ( o2 ) mutant has a high nutritional value but it develops a chalky endosperm that limits its practical use. Genetic selection for o2 modifiers can convert the normally chalky endosperm of the mutant into a hard, vitreous phenotype, yielding what is known as quality protein maize (QPM). Previous studies have shown that enhanced expression of 27-kDa γ-zein in QPM is essential for endosperm modification. Taking advantage of genome-wide association study analysis of a natural population, linkage mapping analysis of a recombinant inbred line population, and map-based cloning, we identified a quantitative trait locus ( qγ27 ) affecting expression of 27-kDa γ-zein. qγ27 was mapped to the same region as the major o2 modifier ( o2 modifier1 ) on chromosome 7 near the 27-kDa γ-zein locus. qγ27 resulted from a 15.26-kb duplication at the 27-kDa γ-zein locus, which increases the level of gene expression. This duplication occurred before maize domestication; however, the gene structure of qγ27 appears to be unstable and the DNA rearrangement frequently occurs at this locus. Because enhanced expression of 27-kDa γ-zein is critical for endosperm modification in QPM, qγ27 is expected to be under artificial selection. This discovery provides a useful molecular marker that can be used to accelerate QPM breeding.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    RVK:
    RVK:
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2016
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    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
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  • 7
    In: Science, American Association for the Advancement of Science (AAAS), Vol. 367, No. 6475 ( 2020-01-17), p. 272-277
    Abstract: One great challenge in understanding the history of life is resolving the influence of environmental change on biodiversity. Simulated annealing and genetic algorithms were used to synthesize data from 11,000 marine fossil species, collected from more than 3000 stratigraphic sections, to generate a new Cambrian to Triassic biodiversity curve with an imputed temporal resolution of 26 ± 14.9 thousand years. This increased resolution clarifies the timing of known diversification and extinction events. Comparative analysis suggests that partial pressure of carbon dioxide ( P co 2 ) is the only environmental factor that seems to display a secular pattern similar to that of biodiversity, but this similarity was not confirmed when autocorrelation within that time series was analyzed by detrending. These results demonstrate that fossil data can provide the temporal and taxonomic resolutions necessary to test (paleo)biological hypotheses at a level of detail approaching those of long-term ecological analyses.
    Type of Medium: Online Resource
    ISSN: 0036-8075 , 1095-9203
    RVK:
    RVK:
    Language: English
    Publisher: American Association for the Advancement of Science (AAAS)
    Publication Date: 2020
    detail.hit.zdb_id: 128410-1
    detail.hit.zdb_id: 2066996-3
    detail.hit.zdb_id: 2060783-0
    SSG: 11
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  • 8
    Online Resource
    Online Resource
    Proceedings of the National Academy of Sciences ; 2014
    In:  Proceedings of the National Academy of Sciences Vol. 111, No. 46 ( 2014-11-18)
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 111, No. 46 ( 2014-11-18)
    Abstract: Comparative genomic analyses among closely related species can greatly enhance our understanding of plant gene and genome evolution. We report de novo-assembled AA-genome sequences for Oryza nivara , Oryza glaberrima , Oryza barthii , Oryza glumaepatula , and Oryza meridionalis . Our analyses reveal massive levels of genomic structural variation, including segmental duplication and rapid gene family turnover, with particularly high instability in defense-related genes. We show, on a genomic scale, how lineage-specific expansion or contraction of gene families has led to their morphological and reproductive diversification, thus enlightening the evolutionary process of speciation and adaptation. Despite strong purifying selective pressures on most Oryza genes, we documented a large number of positively selected genes, especially those genes involved in flower development, reproduction, and resistance-related processes. These diversifying genes are expected to have played key roles in adaptations to their ecological niches in Asia, South America, Africa and Australia. Extensive variation in noncoding RNA gene numbers, function enrichment, and rates of sequence divergence might also help account for the different genetic adaptations of these rice species. Collectively, these resources provide new opportunities for evolutionary genomics, numerous insights into recent speciation, a valuable database of functional variation for crop improvement, and tools for efficient conservation of wild rice germplasm.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    RVK:
    RVK:
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2014
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    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
    Location Call Number Limitation Availability
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