Proceedings of the Natural Academy of Sciences

Proceedings of the National Academy of Sciences RSS feed -- current issue
  • MTHFD1 and severe combined immune deficiency [Biochemistry]
    [Jan 2015]

    An inborn error of metabolism associated with mutations in the human methylenetetrahydrofolate dehydrogenase 1 (MTHFD1) gene has been identified. The proband presented with SCID, megaloblastic anemia, and neurologic abnormalities, but the causal metabolic impairment is unknown. SCID has been associated with impaired purine nucleotide metabolism, whereas megaloblastic anemia has been...
    Categories: Journal Articles
  • Kinetic pathway of 40S recruitment to HCV IRES [Biophysics and Computational Biology]
    [Jan 2015]

    Translation initiation can occur by multiple pathways. To delineate these pathways by single-molecule methods, fluorescently labeled ribosomal subunits are required. Here, we labeled human 40S ribosomal subunits with a fluorescent SNAP-tag at ribosomal protein eS25 (RPS25). The resulting ribosomal subunits could be specifically labeled in living cells and in vitro....
    Categories: Journal Articles
  • Bacteria optimizes energy efficiency [Biophysics and Computational Biology]
    [Jan 2015]

    We are interested in the balance of energy and protein synthesis in bacterial growth. How has evolution optimized this balance? We describe an analytical model that leverages extensive literature data on growth laws to infer the underlying fitness landscape and to draw inferences about what evolution has optimized in Escherichia...
    Categories: Journal Articles
  • Remodeling diatom metabolism [Cell Biology]
    [Jan 2015]

    Diatoms are unicellular algae that accumulate significant amounts of triacylglycerols as storage lipids when their growth is limited by nutrients. Using biochemical, physiological, bioinformatics, and reverse genetic approaches, we analyzed how the flux of carbon into lipids is influenced by nitrogen stress in a model diatom, Phaeodactylum tricornutum. Our results...
    Categories: Journal Articles
  • mLnp1 stabilizes three-way junctions of the ER [Cell Biology]
    [Jan 2015]

    The endoplasmic reticulum (ER) consists of a polygonal network of sheets and tubules interconnected by three-way junctions. This network undergoes continual remodeling through competing processes: the branching and fusion of tubules forms new three-way junctions and new polygons, and junction sliding and ring closure leads to polygon loss. However, little...
    Categories: Journal Articles
  • Molecular-scale organization of bone [Chemistry]
    [Jan 2015]

    The remarkable properties of bone derive from a highly organized arrangement of coaligned nanometer-scale apatite platelets within a fibrillar collagen matrix. The origin of this arrangement is poorly understood and the crystal structures of hydroxyapatite (HAP) and the nonmineralized collagen fibrils alone do not provide an explanation. Moreover, little is...
    Categories: Journal Articles
  • Fnip1 and skeletal muscle fiber type specification [Developmental Biology]
    [Jan 2015]

    Mammalian skeletal muscle is broadly characterized by the presence of two distinct categories of muscle fibers called type I “red” slow twitch and type II “white” fast twitch, which display marked differences in contraction strength, metabolic strategies, and susceptibility to fatigue. The relative representation of each fiber type can have...
    Categories: Journal Articles
  • Carbonates in ALH 84001 and the Martian atmosphere [Earth, Atmospheric, and Planetary Sciences]
    [Jan 2015]

    Carbonate minerals provide critical information for defining atmosphere–hydrosphere interactions. Carbonate minerals in the Martian meteorite ALH 84001 have been dated to ∼3.9 Ga, and both C and O-triple isotopes can be used to decipher the planet’s climate history. Here we report Δ17O, δ18O, and δ13C data of ALH 84001 of...
    Categories: Journal Articles
  • Mg isotopes in mammals [Earth, Atmospheric, and Planetary Sciences]
    [Jan 2015]

    Geochemical inferences on ancient diet using bone and enamel apatite rely mainly on carbon isotope ratios (δ13C) and to a lesser extent on strontium/calcium (Sr/Ca) and barium/calcium (Ba/Ca) elemental ratios. Recent developments in nontraditional stable isotopes provide an unprecedented opportunity to use additional paleodietary proxies to disentangle complex diets such...
    Categories: Journal Articles
  • Increasing CO2 and the carbon cycle [Earth, Atmospheric, and Planetary Sciences]
    [Jan 2015]

    Feedbacks from the terrestrial carbon cycle significantly affect future climate change. The CO2 concentration dependence of global terrestrial carbon storage is one of the largest and most uncertain feedbacks. Theory predicts the CO2 effect should have a tropical maximum, but a large terrestrial sink has been contradicted by analyses of...
    Categories: Journal Articles
  • Global insect herbivore diet breadth [Ecology]
    [Jan 2015]

    Understanding variation in resource specialization is important for progress on issues that include coevolution, community assembly, ecosystem processes, and the latitudinal gradient of species richness. Herbivorous insects are useful models for studying resource specialization, and the interaction between plants and herbivorous insects is one of the most common and consequential...
    Categories: Journal Articles
  • Consistent warming impacts from multiple methods [Ecology]
    [Jan 2015]

    Inference about future climate change impacts typically relies on one of three approaches: manipulative experiments, historical comparisons (broadly defined to include monitoring the response to ambient climate fluctuations using repeat sampling of plots, dendroecology, and paleoecology techniques), and space-for-time substitutions derived from sampling along environmental gradients. Potential limitations of all...
    Categories: Journal Articles
  • Nanoscale vibrations as signature of life [Engineering]
    [Jan 2015]

    The existence of life in extreme conditions, in particular in extraterrestrial environments, is certainly one of the most intriguing scientific questions of our time. In this report, we demonstrate the use of an innovative nanoscale motion sensor in life-searching experiments in Earth-bound and interplanetary missions. This technique exploits the sensitivity...
    Categories: Journal Articles
  • Climate decouples productivity and carbon burial [Environmental Sciences]
    [Jan 2015]

    Understanding responses of oceanic primary productivity, carbon export, and burial to climate change is essential for model-based projection of biological feedbacks in a high-CO2 world. Here we compare estimates of productivity based on the composition of fossil diatom floras with organic carbon burial off Oregon in the Northeast Pacific across...
    Categories: Journal Articles
  • Bacteria-diatom metabolite cycling [Environmental Sciences]
    [Jan 2015]

    About half the carbon fixed by phytoplankton in the ocean is taken up and metabolized by marine bacteria, a transfer that is mediated through the seawater dissolved organic carbon (DOC) pool. The chemical complexity of marine DOC, along with a poor understanding of which compounds form the basis of trophic...
    Categories: Journal Articles
  • Evolution of hominid ethanol metabolism [Evolution]
    [Jan 2015]

    Paleogenetics is an emerging field that resurrects ancestral proteins from now-extinct organisms to test, in the laboratory, models of protein function based on natural history and Darwinian evolution. Here, we resurrect digestive alcohol dehydrogenases (ADH4) from our primate ancestors to explore the history of primate–ethanol interactions. The evolving catalytic properties...
    Categories: Journal Articles
  • Unmasking host-retrovirus macroevolution [Evolution]
    [Jan 2015]

    Although extensive research has demonstrated host-retrovirus microevolutionary dynamics, it has been difficult to gain a deeper understanding of the macroevolutionary patterns of host–retrovirus interactions. Here we use recent technological advances to infer broad patterns in retroviral diversity, evolution, and host–virus relationships by using a large-scale phylogenomic approach using endogenous retroviruses...
    Categories: Journal Articles
  • Natural selection and the evolution of modularity [Evolution]
    [Jan 2015]

    Modularity is a central concept in modern biology, providing a powerful framework for the study of living organisms on many organizational levels. Two central and related questions can be posed in regard to modularity: How does modularity appear in the first place, and what forces are responsible for keeping and/or...
    Categories: Journal Articles
  • Birth cohort modifies FTO-BMI association [Genetics]
    [Jan 2015]

    A substantial body of research has explored the relative roles of genetic and environmental factors on phenotype expression in humans. Recent research has also sought to identify gene–environment (or g-by-e) interactions, with mixed success. One potential reason for these mixed results may relate to the fact that genetic effects might...
    Categories: Journal Articles
  • miR-155 enhances CD8+ T-cell antitumor responses [Immunology and Inflammation]
    [Jan 2015]

    Lymphodepleting regimens are used before adoptive immunotherapy to augment the antitumor efficacy of transferred T cells by removing endogenous homeostatic “cytokine sinks.” These conditioning modalities, however, are often associated with severe toxicities. We found that microRNA-155 (miR-155) enabled tumor-specific CD8+ T cells to mediate profound antitumor responses in lymphoreplete hosts...
    Categories: Journal Articles