Journal: Science Advances

Abbreviation

Sci Adv

Publisher

AAAS

Journal Volumes

ISSN

2375-2548

Description

Filters

2015 - 2019872020 - 2026296
Reset filters

Search Results

Publications 1 - 10 of 383
  • Biodegradation of synthetic polymers in soils: Tracking carbon into CO2 and microbial biomass
    Item type: Journal Article
    Zumstein, Michael T.; Schintlmeister, Arno; Nelson, Taylor F.; et al. (2018)
    Science Advances
    Plastic materials are widely used in agricultural applications to achieve food security for the growing world population. The use of biodegradable instead of nonbiodegradable polymers in single-use agricultural applications, including plastic mulching, promises to reduce plastic accumulation in the environment. We present a novel approach that allows tracking of carbon from biodegradable polymers into CO2 and microbial biomass. The approach is based on 13C-labeled polymers and on isotope-specific analytical methods, including nanoscale secondary ion mass spectrometry (NanoSIMS). Our results unequivocally demonstrate the biodegradability of poly(butylene adipate-co-terephthalate) (PBAT), an important polyester used in agriculture, in soil. Carbon from each monomer unit of PBAT was used by soil microorganisms, including filamentous fungi, to gain energy and to form biomass. This work advances both our conceptual understanding of polymer biodegradation and the methodological capabilities to assess this process in natural and engineered environments.
  • Cenozoic megatooth sharks occupied extremely high trophic positions
    Item type: Journal Article
    Kast, Emma R.; Griffiths, Michael L.; Kim, Sora L.; et al. (2022)
    Science Advances
    Trophic position is a fundamental characteristic of animals, yet it is unknown in many extinct species. In this study, we ground-truth the 15N/14N ratio of enameloid-bound organic matter (δ15NEB) as a trophic level proxy by comparison to dentin collagen δ15N and apply this method to the fossil record to reconstruct the trophic level of the megatooth sharks (genus Otodus). These sharks evolved in the Cenozoic, culminating in Otodus megalodon, a shark with a maximum body size of more than 15 m, which went extinct 3.5 million years ago. Very high δ15NEB values (22.9 ± 4.4‰) of O. megalodon from the Miocene and Pliocene show that it occupied a higher trophic level than is known for any marine species, extinct or extant. δ15NEB also indicates a dietary shift in sharks of the megatooth lineage as they evolved toward the gigantic O. megalodon, with the highest trophic level apparently reached earlier than peak size.
  • Multicomponent new particle formation from sulfuric acid, ammonia, and biogenic vapors
    Item type: Journal Article
    Lehtipalo, Katrianne; Yan, Chao; Dada, Lubna; et al. (2018)
    Science Advances
    A major fraction of atmospheric aerosol particles, which affect both air quality and climate, form from gaseous precursors in the atmosphere. Highly oxygenated organic molecules (HOMs), formed by oxidation of biogenic volatile organic compounds, are known to participate in particle formation and growth. However, it is not well understood how they interact with atmospheric pollutants, such as nitrogen oxides (NOx) and sulfur oxides (SOx) from fossil fuel combustion, as well as ammonia (NH3) from livestock and fertilizers. Here, we show how NOx suppresses particle formation, while HOMs, sulfuric acid, and NH3 have a synergistic enhancing effect on particle formation. We postulate a novel mechanism, involving HOMs, sulfuric acid, and ammonia, which is able to closely reproduce observations of particle formation and growth in daytime boreal forest and similar environments. The findings elucidate the complex interactions between biogenic and anthropogenic vapors in the atmospheric aerosol system.
  • Mapping a functional cancer genome atlas of tumor suppressors in mouse liver using AAV-CRISPR-mediated direct in vivo screening
    Item type: Journal Article
    Wang, Guangchuan; Chow, Ryan D.; Ye, Lupeng; et al. (2018)
    Science Advances
    Cancer genomics consortia have charted the landscapes of numerous human cancers. Whereas some mutations were found in classical oncogenes and tumor suppressors, others have not yet been functionally studied in vivo. To date, a comprehensive assessment of how these genes influence oncogenesis is lacking. We performed direct high-throughput in vivo mapping of functional variants in an autochthonous mouse model of cancer. Using adeno-associated viruses (AAVs) carrying a single-guide RNA (sgRNA) library targeting putative tumor suppressor genes significantly mutated in human cancers, we directly pool-mutagenized the livers of Cre-inducible CRISPR (clustered regularly interspaced short palindromic repeats)–associated protein 9 (Cas9) mice. All mice that received the AAV-mTSG library developed liver cancer and died within 4 months. We used molecular inversion probe sequencing of the sgRNA target sites to chart the mutational landscape of these tumors, revealing the functional consequence of multiple variants in driving liver tumorigenesis in immunocompetent mice. AAV-mediated autochthonous CRISPR screens provide a powerful means for mapping a provisional functional cancer genome atlas of tumor suppressors in vivo.
  • Escaping undesired gas-phase chemistry: Microwave-driven selectivity enhancement in heterogeneous catalytic reactors
    Item type: Journal Article
    Ramirez Galilea, Adrian; Hueso, José L.; Abián, María; et al. (2019)
    Science Advances
    Research in solid-gas heterogeneous catalytic processes is typically aimed toward optimization of catalyst composition to achieve a higher conversion and, especially, a higher selectivity. However, even with the most selective catalysts, an upper limit is found: Above a certain temperature, gas-phase reactions become important and their effects cannot be neglected. Here, we apply a microwave field to a catalyst-support ensemble capable of direct microwave heating (MWH). We have taken extra precautions to ensure that (i) the solid phase is free from significant hot spots and (ii) an accurate estimation of both solid and gas temperatures is obtained. MWH allows operating with a catalyst that is significantly hotter than the surrounding gas, achieving a high conversion on the catalyst while reducing undesired homogeneous reactions. We demonstrate the concept with the CO2-mediated oxidative dehydrogenation of isobutane, but it can be applied to any system with significant undesired homogeneous contributions.
  • Hallmarks of Alpha- And Betacoronavirus non-structural protein 7+8 complexes
    Item type: Journal Article
    Krichel, Boris; Bylapudi, Ganesh; Schmidt, Christina; et al. (2021)
    Science Advances
    Coronaviruses infect many different species including humans. The last two decades have seen three zoonotic coronaviruses, with SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) causing a pandemic in 2020. Coronaviral non-structural proteins (nsps) form the replication-transcription complex (RTC). Nsp7 and nsp8 interact with and regulate the RNA-dependent RNA-polymerase and other enzymes in the RTC. However, the structural plasticity of nsp7+8 complexes has been under debate. Here, we present the framework of nsp7+8 complex stoichiometry and topology based on native mass spectrometry and complementary biophysical techniques of nsp7+8 complexes from seven coronaviruses in the genera Alpha- and Betacoronavirus including SARS-CoV-2. Their complexes cluster into three groups, which systematically form either heterotrimers or heterotetramers or both, exhibiting distinct topologies. Moreover, even at high protein concentrations, SARS-CoV-2 nsp7+8 consists primarily of heterotetramers. From these results, the different assembly paths can be pinpointed to specific residues and an assembly model proposed.
  • Structures of wild-type and selected CMT1X mutant connexin 32 gap junction channels and hemichannels
    Item type: Journal Article
    Qi, Chao; Lavriha, Pia; Bayraktar, Erva; et al. (2023)
    Science Advances
    In myelinating Schwann cells, connection between myelin layers is mediated by gap junction channels (GJCs) formed by docked connexin 32 (Cx32) hemichannels (HCs). Mutations in Cx32 cause the X-linked Charcot-Marie-Tooth disease (CMT1X), a degenerative neuropathy without a cure. A molecular link between Cx32 dysfunction and CMT1X pathogenesis is still missing. Here, we describe the high-resolution cryo-electron cryo-myography (cryo-EM) structures of the Cx32 GJC and HC, along with two CMT1X-linked mutants, W3S and R22G. While the structures of wild-type and mutant GJCs are virtually identical, the HCs show a major difference: In the W3S and R22G mutant HCs, the amino-terminal gating helix partially occludes the pore, consistent with a diminished HC activity. Our results suggest that HC dysfunction may be involved in the pathogenesis of CMT1X.
  • The genetic mechanism of selfishness and altruism in parent-offspring coadaptation
    Item type: Journal Article
    Wu, Min; Walser, Jean-Claude; Sun, Lei; et al. (2020)
    Science Advances
    The social bond between parents and offspring is characterized by coadaptation and balance between altruistic and selfish tendencies. However, its underlying genetic mechanism remains poorly understood. Using transcriptomic screens in the subsocial European earwig, Forficula auricularia, we found the expression of more than 1600 genes associated with experimentally manipulated parenting. We identified two genes, Th and PebIII, each showing evidence of differential coexpression between treatments in mothers and their offspring. In vivo RNAi experiments confirmed direct and indirect genetic effects of Th and PebIII on behavior and fitness, including maternal food provisioning and reproduction, and offspring development and survival. The direction of the effects consistently indicated a reciprocally altruistic function for Th and a reciprocally selfish function for PebIII. Further metabolic pathway analyses suggested roles for Th-restricted endogenous dopaminergic reward, PebIII-mediated chemical communication and a link to insulin signaling, juvenile hormone, and vitellogenin in parent-offspring coadaptation and social evolution.
  • Revisiting the scale of mantle plume-induced hot spot swells
    Item type: Journal Article
    Liu , Liang; Morgan , Jason P.; Xu , Yi-Gang; et al. (2025)
    Science Advances
    Hotspot swells have typically been associated with mantle plume upwelling, yet the origins of much broader but lower superswells remain unclear. This study first reveals that swell width increases while height decreases at younger seafloor ages; it is possible for a single hot spot swell size to approach that of a superswell. Compressible numerical models replicate the observed trend. Modeling results suggest that both hot spot swells and superswells can form from interactions between mantle plumes and oceanic plates. Beneath young seafloors, the lateral redistribution of restitic, hence buoyant and relatively low-viscosity, lower lithospheric mantle due to plume impingement explains the formation of superswell-like morphology. These models effectively demonstrate lithospheric lid effects on mantle melting and support a reassessment of conventional methods for estimating core heat flux.
  • Onset of slab mantle melting in Earth's lower mantle: Evidence from ferropericlase in superdeep diamonds
    Item type: Journal Article
    Ni , Peng; Shirey , Steven B.; Walter , Michael J.; et al. (2025)
    Science Advances
    Ferropericlase ([Mgₓ,Feₓ₋₁]O), the most common inclusion in sublithospheric diamonds, has a poorly understood crystallization history and depth of origin. Nineteen microscopic ferropericlase grains with different Mg#s were released from Juína and Kankan diamonds with mantle-like carbon, for Mg and Fe isotopic analysis. Two groups of ferropericlase inclusions can be distinguished with respect to diamond growth: high-Mg# inclusions with mantle-like Mg and Fe (δ²⁶Mg = -0.23 ± 0.22‰; δ⁵⁶Fe = 0.00 ± 0.14‰) inferred to be preexisting and lower Mg# inclusions with non-mantle-like heavy Fe (δ⁵⁶Fe up to +0.3‰) and light Mg (δ²⁶Mg down to -1.4‰) inferred to be coeval. We propose that coeval ferropericlase inclusions formed by melting of hydrated and carbonated peridotitic slab components subducted to lower mantle depths. Continuous reaction of these melts with surrounding reduced, dry slab harzburgite can produce the large range in Mg# and Ni contents of our ferropericlase suite-a heretofore unexplained feature of global ferropericlase data.
Publications 1 - 10 of 383