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Τρίτη 12 Μαΐου 2020


Airfoil-like mechanics generate thrust on the anterior body of swimming fishes [Engineering]
The anterior body of many fishes is shaped like an airfoil turned on its side. With an oscillating angle to the swimming direction, such an airfoil experiences negative pressure due to both its shape and pitching movements. This negative pressure acts as thrust forces on the anterior body. Here, we...
Proceedings of the National Academy of Sciences current issue
11h
The structure of helical lipoprotein lipase reveals an unexpected twist in lipase storage [Biophysics and Computational Biology]
Lipases are enzymes necessary for the proper distribution and utilization of lipids in the human body. Lipoprotein lipase (LPL) is active in capillaries, where it plays a crucial role in preventing dyslipidemia by hydrolyzing triglycerides from packaged lipoproteins. Thirty years ago, the existence of a condensed and inactive LPL oligomer...
Proceedings of the National Academy of Sciences current issue
11h
Global-scale brittle plastic rheology at the cometesimals merging of comet 67P/Churyumov-Gerasimenko [Earth, Atmospheric, and Planetary Sciences]
Observations of comet nuclei indicate that the main constituent is a mix of ice and refractory materials characterized by high porosity (70–75%) and low bulk strength (10−4–10−6 MPa); however, the nature and physical properties of these materials remain largely unknown. By combining surface inspection of comet 67P/Churyumov–Gerasimenko and three-dimensional (3D)...
Proceedings of the National Academy of Sciences current issue
11h
Effects of an HIV-1 maturation inhibitor on the structure and dynamics of CA-SP1 junction helices in virus-like particles [Biophysics and Computational Biology]
HIV-1 maturation involves conversion of the immature Gag polyprotein lattice, which lines the inner surface of the viral membrane, to the mature capsid protein (CA) lattice, which encloses the viral RNA. Maturation inhibitors such as bevirimat (BVM) bind within six-helix bundles, formed by a segment that spans the junction between...
Proceedings of the National Academy of Sciences current issue
11h
The Great Oxidation Event expanded the genetic repertoire of arsenic metabolism and cycling [Environmental Sciences]
The rise of oxygen on the early Earth about 2.4 billion years ago reorganized the redox cycle of harmful metal(loids), including that of arsenic, which doubtlessly imposed substantial barriers to the physiology and diversification of life. Evaluating the adaptive biological responses to these environmental challenges is inherently difficult because of...
Proceedings of the National Academy of Sciences current issue
11h
Quantitative analysis of amino acid metabolism in liver cancer links glutamate excretion to nucleotide synthesis [Biophysics and Computational Biology]
Many cancer cells consume glutamine at high rates; counterintuitively, they simultaneously excrete glutamate, the first intermediate in glutamine metabolism. Glutamine consumption has been linked to replenishment of tricarboxylic acid cycle (TCA) intermediates and synthesis of adenosine triphosphate (ATP), but the reason for glutamate excretion is unclear. Here, we dynamically profile...
Proceedings of the National Academy of Sciences current issue
11h
Reply to Serra et al.: Nucleotide substitutions in plant viroid genomes that multiply in phytopathogenic fungi [Biological Sciences]
This is our response to the letter by Serra et al. (1), which questioned our recent paper (2) describing plant viroid infections in phytopathogenic fungi. In this study, full-length monomeric cDNA clones of seven plant viroid RNA genomes were produced using oligonucleotide synthesis (2). We opted for the monomeric version...
Proceedings of the National Academy of Sciences current issue
11h
Pan-cancer analysis identifies mutations in SUGP1 that recapitulate mutant SF3B1 splicing dysregulation [Biophysics and Computational Biology]
The gene encoding the core spliceosomal protein SF3B1 is the most frequently mutated gene encoding a splicing factor in a variety of hematologic malignancies and solid tumors. SF3B1 mutations induce use of cryptic 3′ splice sites (3′ss), and these splicing errors contribute to tumorigenesis. However, it is unclear how widespread...
Proceedings of the National Academy of Sciences current issue
11h
The structural basis for inhibition of ribosomal translocation by viomycin [Biochemistry]
Viomycin, an antibiotic that has been used to fight tuberculosis infections, is believed to block the translocation step of protein synthesis by inhibiting ribosomal subunit dissociation and trapping the ribosome in an intermediate state of intersubunit rotation. The mechanism by which viomycin stabilizes this state remains unexplained. To address this,...
Proceedings of the National Academy of Sciences current issue
11h
Intracellular Ca2+ regulation of H+/Ca2+ antiporter YfkE mediated by a Ca2+ mini-sensor [Biophysics and Computational Biology]
The H+/Ca2+ (calcium ion) antiporter (CAX) plays an important role in maintaining cellular Ca2+ homeostasis in bacteria, yeast, and plants by promoting Ca2+ efflux across the cell membranes. However, how CAX facilitates Ca2+ balance in response to dynamic cytosolic Ca2+ perturbations is unknown. Here, we identified a type of Ca2+...
Proceedings of the National Academy of Sciences current issue
11h
Amyloid assembly is dominated by misregistered kinetic traps on an unbiased energy landscape [Biophysics and Computational Biology]
Atomistic description of protein fibril formation has been elusive due to the complexity and long time scales of the conformational search. Here, we develop a multiscale approach combining numerous atomistic simulations in explicit solvent to construct Markov State Models (MSMs) of fibril growth. The search for the in-register fully bound...
Proceedings of the National Academy of Sciences current issue
11h
The evolutionary scaling of cellular traits imposed by the drift barrier [Evolution]
Owing to internal homeostatic mechanisms, cellular traits may experience long periods of stable selective pressures, during which the stochastic forces of drift and mutation conspire to generate variation. However, even in the face of invariant selection, the drift barrier defined by the genetic effective population size, which is negatively associated...
Proceedings of the National Academy of Sciences current issue
11h
Molecular dysregulation of ciliary polycystin-2 channels caused by variants in the TOP domain [Biophysics and Computational Biology]
Genetic variants in PKD2 which encodes for the polycystin-2 ion channel are responsible for many clinical cases of autosomal dominant polycystic kidney disease (ADPKD). Despite our strong understanding of the genetic basis of ADPKD, we do not know how most variants impact channel function. Polycystin-2 is found in organelle membranes,...
Proceedings of the National Academy of Sciences current issue
11h
Geometric charges and nonlinear elasticity of two-dimensional elastic metamaterials [Physics]
Problems of flexible mechanical metamaterials, and highly deformable porous solids in general, are rich and complex due to their nonlinear mechanics and the presence of nontrivial geometrical effects. While numeric approaches are successful, analytic tools and conceptual frameworks are largely lacking. Using an analogy with electrostatics, and building on recent...
Proceedings of the National Academy of Sciences current issue
11h
Inner ear sensory system changes as extinct crocodylomorphs transitioned from land to water [Earth, Atmospheric, and Planetary Sciences]
Major evolutionary transitions, in which animals develop new body plans and adapt to dramatically new habitats and lifestyles, have punctuated the history of life. The origin of cetaceans from land-living mammals is among the most famous of these events. Much earlier, during the Mesozoic Era, many reptile groups also moved...
Proceedings of the National Academy of Sciences current issue
11h
Reply to Zhang et al.: The differential role of LRRK2 variants in nested leprosy phenotypes [Biological Sciences]
We thank Dr. Zhang et al. (1) for their thought-provoking comments and addition of exciting results to our recent study that identifies an overlap in the genetic control of type-1 reaction (T1R) and Parkinson’s disease (PD) (2). To put the comments by Zhang et al. into context, the purpose and...
Proceedings of the National Academy of Sciences current issue
11h
Honey bee virus causes context-dependent changes in host social behavior [Ecology]
Anthropogenic changes create evolutionarily novel environments that present opportunities for emerging diseases, potentially changing the balance between host and pathogen. Honey bees provide essential pollination services, but intensification and globalization of honey bee management has coincided with increased pathogen pressure, primarily due to a parasitic mite/virus complex. Here, we investigated...
Proceedings of the National Academy of Sciences current issue
11h
Aseismic transient slip on the Gofar transform fault, East Pacific Rise [Earth, Atmospheric, and Planetary Sciences]
Oceanic transform faults display a unique combination of seismic and aseismic slip behavior, including a large globally averaged seismic deficit, and the local occurrence of repeating magnitude (M) ∼6 earthquakes with abundant foreshocks and seismic swarms, as on the Gofar transform of the East Pacific Rise and the Blanco Ridge...
Proceedings of the National Academy of Sciences current issue
11h
Cell atlas of aqueous humor outflow pathways in eyes of humans and four model species provides insight into glaucoma pathogenesis [Cell Biology]
Increased intraocular pressure (IOP) represents a major risk factor for glaucoma, a prevalent eye disease characterized by death of retinal ganglion cells; lowering IOP is the only proven treatment strategy to delay disease progression. The main determinant of IOP is the equilibrium between production and drainage of aqueous humor, with...
Proceedings of the National Academy of Sciences current issue
11h
Phenological responses of temperate and boreal trees to warming depend on ambient spring temperatures, leaf habit, and geographic range [Ecology]
Changes in plant phenology associated with climate change have been observed globally. What is poorly known is whether and how phenological responses to climate warming will differ from year to year, season to season, habitat to habitat, or species to species. Here, we present 5 y of phenological responses to...
Proceedings of the National Academy of Sciences current issue
11h
Noise-driven cellular heterogeneity in circadian periodicity [Cell Biology]
Nongenetic cellular heterogeneity is associated with aging and disease. However, the origins of cell-to-cell variability are complex and the individual contributions of different factors to total phenotypic variance are still unclear. Here, we took advantage of clear phenotypic heterogeneity of circadian oscillations in clonal cell populations to investigate the underlying...
Proceedings of the National Academy of Sciences current issue
11h
Multiple agents managing a harmful species population should either work together to control it or split their duties to eradicate it [Economic Sciences]
The management of harmful species, including invasive species, pests, parasites, and diseases, is a major global challenge. Harmful species cause severe damage to ecosystems, biodiversity, agriculture, and human health. In particular, managing harmful species often requires cooperation among multiple agents, such as landowners, agencies, and countries. Each agent may have...
Proceedings of the National Academy of Sciences current issue
11h
Drosophila as a model for studying cystic fibrosis pathophysiology of the gastrointestinal system [Cell Biology]
Cystic fibrosis (CF) is a recessive disease caused by mutations in the CF transmembrane conductance regulator (CFTR) gene. The most common symptoms include progressive lung disease and chronic digestive conditions. CF is the first human genetic disease to benefit from having five different species of animal models. Despite the phenotypic...
Proceedings of the National Academy of Sciences current issue
11h
Quasi-Fermi level splitting in nanoscale junctions from ab initio [Applied Physical Sciences]
The splitting of quasi-Fermi levels (QFLs) represents a key concept utilized to describe finite-bias operations of semiconductor devices, but its atomic-scale characterization remains a significant challenge. Herein, the nonequilibrium QFL or electrochemical potential profiles within single-molecule junctions obtained from the first-principles multispace constrained-search density-functional formalism are presented. Benchmarking the standard...
Proceedings of the National Academy of Sciences current issue
11h
Hurricane effects on Neotropical lizards span geographic and phylogenetic scales [Evolution]
Extreme climate events such as droughts, cold snaps, and hurricanes can be powerful agents of natural selection, producing acute selective pressures very different from the everyday pressures acting on organisms. However, it remains unknown whether these infrequent but severe disruptions are quickly erased by quotidian selective forces, or whether they...
Proceedings of the National Academy of Sciences current issue
11h
High-speed interferometric imaging reveals dynamics of neuronal deformation during the action potential [Applied Physical Sciences]
Neurons undergo nanometer-scale deformations during action potentials, and the underlying mechanism has been actively debated for decades. Previous observations were limited to a single spot or the cell boundary, while movement across the entire neuron during the action potential remained unclear. Here we report full-field imaging of cellular deformations accompanying...
Proceedings of the National Academy of Sciences current issue
11h
Evolution of a high-performance and functionally robust musculoskeletal system in salamanders [Evolution]
The evolution of ballistic tongue projection in plethodontid salamanders—a high-performance and thermally robust musculoskeletal system—is ideal for examining how the components required for extreme performance in animal movement are assembled in evolution. Our comparative data on whole-organism performance measured across a range of temperatures and the musculoskeletal morphology of the...
Proceedings of the National Academy of Sciences current issue
11h
Observation of indentation-induced shear bands in a metal-organic framework glass [Applied Physical Sciences]
Metal−organic framework (MOF) glasses are a newly emerged family of melt-quenched glasses. Recently, several intriguing features, such as ultrahigh glass-forming ability and low liquid fragility, have been discovered in a number of zeolitic imidazolate frameworks (ZIFs) that are a subset of MOFs. However, the fracture behavior of ZIF glasses has...
Proceedings of the National Academy of Sciences current issue
11h
MAPK-directed activation of the whitefly transcription factor CREB leads to P450-mediated imidacloprid resistance [Agricultural Sciences]
The evolution of insect resistance to pesticides poses a continuing threat to agriculture and human health. While much is known about the proximate molecular and biochemical mechanisms that confer resistance, far less is known about the regulation of the specific genes/gene families involved, particularly by trans-acting factors such as signal-regulated...
Proceedings of the National Academy of Sciences current issue
11h
Collective decision-making by rational agents with differing preferences [Applied Mathematics]
Collective decisions can emerge from individual-level interactions between members of a group. These interactions are often seen as social feedback rules, whereby individuals copy the decisions they observe others making, creating a coherent group decision. The benefit of these behavioral rules to the individual agent can be understood as a...
Proceedings of the National Academy of Sciences current issue
11h
Fibroblast rejuvenation by mechanical reprogramming and redifferentiation [Applied Biological Sciences]
Over the course of the aging process, fibroblasts lose contractility, leading to reduced connective-tissue stiffness. A promising therapeutic avenue for functional rejuvenation of connective tissue is reprogrammed fibroblast replacement, although major hurdles still remain. Toward this, we recently demonstrated that the laterally confined growth of fibroblasts on micropatterned substrates induces...
Proceedings of the National Academy of Sciences current issue
11h
Rainfall anomalies are a significant driver of cropland expansion [Sustainability Science]
Rainfall anomalies have long occupied center stage in policy discussions, and understanding their impacts on agricultural production has become more important as climate change intensifies. However, the global scale of rainfall-induced productivity shocks on changes in cropland is yet to be quantified. Here we identify how rainfall anomalies impact observed...
Proceedings of the National Academy of Sciences current issue
11h
Global control of bacterial nitrogen and carbon metabolism by a PTSNtr-regulated switch [Agricultural Sciences]
The nitrogen-related phosphotransferase system (PTSNtr) of Rhizobium leguminosarum bv. viciae 3841 transfers phosphate from PEP via PtsP and NPr to two output regulators, ManX and PtsN. ManX controls central carbon metabolism via the tricarboxylic acid (TCA) cycle, while PtsN controls nitrogen uptake, exopolysaccharide production, and potassium homeostasis, each of which...
Proceedings of the National Academy of Sciences current issue
11h
Colloidal stability of the living cell [Biochemistry]
Cellular function is generally depicted at the level of functional pathways and detailed structural mechanisms, based on the identification of specific protein–protein interactions. For an individual protein searching for its partner, however, the perspective is quite different: The functional task is challenged by a dense crowd of nonpartners obstructing the...
Proceedings of the National Academy of Sciences current issue
11h
A promising front in the war on inequality [Social Sciences]
Over the last half century, earnings and income inequality have increased within many countries, although the timing and extent of the increase have been variable. This development has engendered a large stream of social science research that has successfully identified some of the main culprits behind the takeoff in inequality....
Proceedings of the National Academy of Sciences current issue
11h
Proteomics illuminates fat as key tissue in aging [Chemistry]
Proteomics, defined broadly as the large-scale study of genes at the level of proteins, has entirely revolutionized our understanding of the chemical composition and organization of biological systems. Over the past two decades, mass spectrometry-based proteomics has emerged as the dominant technique owing to its quantitative measurements in even highly...
Proceedings of the National Academy of Sciences current issue
11h
Stressed DNA replication generates stressed DNA [Genetics]
Much of our understanding of eukaryotic replication dynamics, origin, and polymerase usage and replication factors has come from studies using the yeast Saccharomyces cerevisiae. From the definition of replication origins using plasmid transformation (1, 2) and two-dimensional gel electrophoresis (3), identification of replication factors using various genetic screens for cell...
Proceedings of the National Academy of Sciences current issue
11h
NORs on human acrocentric chromosome p-arms are active by default and can associate with nucleoli independently of rDNA [Cell Biology]
Nucleoli, the sites of ribosome biogenesis and the largest structures in human nuclei, form around nucleolar organizer regions (NORs) comprising ribosomal DNA (rDNA) arrays. NORs are located on the p-arms of the five human acrocentric chromosomes. Defining the rules of engagement between these p-arms and nucleoli takes on added significance...
Proceedings of the National Academy of Sciences current issue
11h
K6-linked SUMOylation of BAF regulates nuclear integrity and DNA replication in mammalian cells [Cell Biology]
Barrier-to-autointegration factor (BAF) is a highly conserved protein in metazoans that has multiple functions during the cell cycle. We found that BAF is SUMOylated at K6, and that this modification is essential for its nuclear localization and function, including nuclear integrity maintenance and DNA replication. K6-linked SUMOylation of BAF promotes...
Proceedings of the National Academy of Sciences current issue
11h

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