Proceedings of the Natural Academy of Sciences

Proceedings of the National Academy of Sciences RSS feed -- current issue
  • Solid-state structures of peapod bearings [Chemistry]
    [Jun 2014]

    A supramolecular combination of carbon nanotube and fullerene, so-called a peapod, has attracted much interest, not solely because of its physical properties but also for its unique assembled structures of carbonaceous entities. However, the detailed structural information available was not sufficient for in-depth understanding of its structural chemistry or for...
    Categories: Journal Articles
  • Optimizing antibiotic treatment protocols [Population Biology]
    [Jun 2014]

    The successful treatment of bacterial infections is the product of a collaboration between antibiotics and the host’s immune defenses. Nevertheless, in the design of antibiotic treatment regimens, few studies have explored the combined action of antibiotics and the immune response to clearing infections. Here, we use mathematical models to examine...
    Categories: Journal Articles
  • Spraying to see cancer cells [Inner Workings]
    [Jun 2014]

    In a Stanford University operating room, surgeons peer into the abdomen of a patient, scalpels delicately dancing under the bright lights. They’re removing a gastric tumor, hoping they can cut away every cancerous cell. Just outside the operating room, an unlikely group waits to lend a hand: they’re not medical...
    Categories: Journal Articles
  • Evolution of social monogamy in primates [Biological Sciences]
    [Apr 2014]

    Comparative analyses suggest that monogamous breeding systems evolved in mammals where feeding competition reduces range overlap between breeding females, preventing males from guarding more than one female at a time (1). In contrast, a recent analysis for primates suggests that monogamy evolved as a form of paternal care that reduces...
    Categories: Journal Articles
  • Infanticide still drives primate monogamy [Biological Sciences]
    [Apr 2014]

    For many years, it has been variously suggested that the evolution of monogamy in primates was due to paternal care, dispersed female ranging, or infanticide. It was therefore of little surprise to us that we should find that these traits are strongly associated with mating systems in primates (1). The...
    Categories: Journal Articles
  • Tropical montane plants lag behind climate [Biological Sciences]
    [Apr 2014]

    The recent paper by Freeman and Class Freeman (1) adds to a growing body of literature documenting the upslope distributional shifts of tropical montane species in response to climate change. Armed with just a handful of studies from the tropics, the authors compare upslope shift rates between tropical and nontropical...
    Categories: Journal Articles
  • Why do upslope shifts vary? More data needed [Biological Sciences]
    [Apr 2014]

    Global warming is causing a great many species to shift their distributions poleward and upslope around the world (1), whereas others appear unaffected. Reasons for this variation in response remain murky. One source of variation may be geographic: tropical species, adapted to relatively stable thermal environments, may be more sensitive...
    Categories: Journal Articles
  • Mapping the stochastic response of nanostructures [Engineering]
    [Apr 2014]

    Nanostructures are technological devices constructed on a nanometer length scale more than a thousand times thinner than a human hair. Due to the unique properties of matter at this scale, such devices offer great potential for creating novel materials and behaviors that can be leveraged to benefit mankind. This paper...
    Categories: Journal Articles
  • Cdc48{sdot}20S architecture [Biochemistry]
    [Apr 2014]

    ATP-dependent proteases maintain protein quality control and regulate diverse intracellular functions. Proteasomes are primarily responsible for these tasks in the archaeal and eukaryotic domains of life. Even the simplest of these proteases function as large complexes, consisting of the 20S peptidase, a barrel-like structure composed of four heptameric rings, and...
    Categories: Journal Articles
  • Dre2-Tah18 is required for RNR cofactor assembly [Biochemistry]
    [Apr 2014]

    Eukaryotic ribonucleotide reductases (RNRs) require a diferric-tyrosyl radical (FeIII2-Y•) cofactor to produce deoxynucleotides essential for DNA replication and repair. This metallocofactor is an important target of RNR-based therapeutics, although mechanisms of in vivo cofactor assembly, inactivation, and reactivation are poorly understood. Here, we demonstrate that the conserved Fe-S protein–diflavin reductase...
    Categories: Journal Articles
  • Measuring pKas of His in invisible protein states [Biophysics and Computational Biology]
    [Apr 2014]

    The histidine imidazole side chain plays a critical role in protein function and stability. Its importance for catalysis is underscored by the fact that histidines are localized to active sites in ∼50% of all enzymes. NMR spectroscopy has become an important tool for studies of histidine side chains through the...
    Categories: Journal Articles
  • Ionic control of K+ channel inactivation [Biophysics and Computational Biology]
    [Apr 2014]

    K+ efflux through K+ channels can be controlled by C-type inactivation, which is thought to arise from a conformational change near the channel’s selectivity filter. Inactivation is modulated by ion binding near the selectivity filter; however, the molecular forces that initiate inactivation remain unclear. We probe these driving forces by...
    Categories: Journal Articles
  • Ciliated epithelial cells from iPSCs [Cell Biology]
    [Apr 2014]

    Despite therapeutic advancement, pulmonary disease still remains a major cause of morbidity and mortality around the world. Opportunities to study human lung disease either in vivo or in vitro are currently limited. Using induced pluripotent stem cells (iPSCs), we generated mature multiciliated cells in a functional airway epithelium. Robust multiciliogenesis...
    Categories: Journal Articles
  • Heterogeneity profiling by hyaluronan probes [Cell Biology]
    [Apr 2014]

    Tumor heterogeneity confounds cancer diagnosis and the outcome of therapy, necessitating analysis of tumor cell subsets within the tumor mass. Elevated expression of hyaluronan (HA) and HA receptors, receptor for HA-mediated motility (RHAMM)/HA-mediated motility receptor and cluster designation 44 (CD44), in breast tumors correlates with poor outcome. We hypothesized that...
    Categories: Journal Articles
  • Role of Brf1 in pluripotency and differentiation [Developmental Biology]
    [Apr 2014]

    AU-rich element mRNA-binding proteins (AUBPs) are key regulators of development, but how they are controlled and what functional roles they play depends on cellular context. Here, we show that Brf1 (zfp36l1), an AUBP from the Zfp36 protein family, operates downstream of FGF/Erk MAP kinase signaling to regulate pluripotency and cell...
    Categories: Journal Articles
  • Humoral responses to Forssman after PROSTVAC-VF [Medical Sciences]
    [Apr 2014]

    Therapeutic cancer vaccines can be effective for treating patients, but clinical responses vary considerably from patient to patient. Early indicators of a favorable response are crucial for making individualized treatment decisions and advancing vaccine design, but no validated biomarkers are currently available. In this study, we used glycan microarrays to...
    Categories: Journal Articles
  • Saturable CQ transport via diverse PfCRT proteins [Microbiology]
    [Apr 2014]

    Mutations in the chloroquine resistance transporter (PfCRT) are the primary determinant of chloroquine (CQ) resistance in the malaria parasite Plasmodium falciparum. A number of distinct PfCRT haplotypes, containing between 4 and 10 mutations, have given rise to CQ resistance in different parts of the world. Here we present a detailed...
    Categories: Journal Articles
  • Population genomics of epidemic disease [Microbiology]
    [Apr 2014]

    We sequenced the genomes of 3,615 strains of serotype Emm protein 1 (M1) group A Streptococcus to unravel the nature and timing of molecular events contributing to the emergence, dissemination, and genetic diversification of an unusually virulent clone that now causes epidemic human infections worldwide. We discovered that the contemporary...
    Categories: Journal Articles
  • Ptf1a-/- cerebellar to brainstem transformation [Neuroscience]
    [Apr 2014]

    Model organism studies have demonstrated that cell fate specification decisions play an important role in normal brain development. Their role in human neurodevelopmental disorders, however, is poorly understood, with very few examples described. The cerebellum is an excellent system to study mechanisms of cell fate specification. Although signals from the...
    Categories: Journal Articles
  • Map homeostasis without individual channelostasis [Neuroscience]
    [Apr 2014]

    The maintenance of ion channel homeostasis, or channelostasis, is a complex puzzle in neurons with extensive dendritic arborization, encompassing a combinatorial diversity of proteins that encode these channels and their auxiliary subunits, their localization profiles, and associated signaling machinery. Despite this, neurons exhibit amazingly stereotypic, topographically continuous maps of several...
    Categories: Journal Articles