Proceedings of the Natural Academy of Sciences

Proceedings of the National Academy of Sciences RSS feed -- current issue
  • Cdc42 dynamics control directional growth [Microbiology]
    [Jan 2014]

    Polarized cells reorient their direction of growth in response to environmental cues. In the fungus Candida albicans, the Rho-family small GTPase, Cdc42, is essential for polarized hyphal growth and Ca2+ influx is required for the tropic responses of hyphae to environmental cues, but the regulatory link between these systems is...
    Categories: Journal Articles
  • Inner rod function in type III secretion [Microbiology]
    [Jan 2014]

    Type III secretion machines are essential for the biology of many bacteria that are pathogenic or symbiotic for animals, plants, or insects. They exert their function by delivering bacterial effector proteins into target eukaryotic cells. The core component of these machines is the needle complex, a multiprotein structure that spans...
    Categories: Journal Articles
  • Sex differences in structural connectome [Neuroscience]
    [Jan 2014]

    Sex differences in human behavior show adaptive complementarity: Males have better motor and spatial abilities, whereas females have superior memory and social cognition skills. Studies also show sex differences in human brains but do not explain this complementarity. In this work, we modeled the structural connectome using diffusion tensor imaging...
    Categories: Journal Articles
  • Direct conversion models ALS astrocyte toxicity [Neuroscience]
    [Jan 2014]

    Amyotrophic lateral sclerosis (ALS) causes motor neuron degeneration, paralysis, and death. Accurate disease modeling, identifying disease mechanisms, and developing therapeutics is urgently needed. We previously reported motor neuron toxicity through postmortem ALS spinal cord-derived astrocytes. However, these cells can only be harvested after death, and their expansion is limited. We...
    Categories: Journal Articles
  • Brain connectivity predicted by network measures [Neuroscience]
    [Jan 2014]

    The complex relationship between structural and functional connectivity, as measured by noninvasive imaging of the human brain, poses many unresolved challenges and open questions. Here, we apply analytic measures of network communication to the structural connectivity of the human brain and explore the capacity of these measures to predict resting-state...
    Categories: Journal Articles
  • SHP-EID1 crystal structure [Pharmacology]
    [Jan 2014]

    Small heterodimer partner (SHP) is an orphan nuclear receptor that functions as a transcriptional repressor to regulate bile acid and cholesterol homeostasis. Although the precise mechanism whereby SHP represses transcription is not known, E1A-like inhibitor of differentiation (EID1) was isolated as a SHP-interacting protein and implicated in SHP repression. Here...
    Categories: Journal Articles
  • Field trials for bioethanol applications [Plant Biology]
    [Jan 2014]

    Lignin is one of the main factors determining recalcitrance to enzymatic processing of lignocellulosic biomass. Poplars (Populus tremula x Populus alba) down-regulated for cinnamoyl-CoA reductase (CCR), the enzyme catalyzing the first step in the monolignol-specific branch of the lignin biosynthetic pathway, were grown in field trials in Belgium and France...
    Categories: Journal Articles
  • Role of strigolactone in abiotic stress response [Plant Biology]
    [Jan 2014]

    This report provides direct evidence that strigolactone (SL) positively regulates drought and high salinity responses in Arabidopsis. Both SL-deficient and SL-response [more axillary growth (max)] mutants exhibited hypersensitivity to drought and salt stress, which was associated with shoot- rather than root-related traits. Exogenous SL treatment rescued the drought-sensitive phenotype of...
    Categories: Journal Articles
  • Democratic decisions establish stable authorities [Social Sciences]
    [Jan 2014]

    Individuals usually punish free riders but refuse to sanction those who cooperate but do not punish. This missing second-order peer punishment is a fundamental problem for the stabilization of cooperation. To solve this problem, most societies today have implemented central authorities that punish free riders and tax evaders alike, such...
    Categories: Journal Articles
  • In This Issue [This Week in PNAS]
    [Jan 2014]

    Democracy encourages broadly beneficial institutional choices Although humans are typically willing to punish so-called free riders—people who use public resources without contributing to them—most people balk at sanctioning community members who refuse to punish others. Modern societies usually address this threat to collective action by installing central authorities such as...
    Categories: Journal Articles
  • Profile of Paul Schulze-Lefert [Profiles]
    [Jan 2014]

    Growing up on his family’s farm in northwestern Germany, Paul Schulze-Lefert received an early introduction to plant biology that blossomed into a lifelong interest. In a fruitful career as a plant biologist, Schulze-Lefert has played a crucial role in elucidating mechanisms by which the plant immune system detects and fights...
    Categories: Journal Articles
  • No-splash theorems for fluid interfaces [Mathematics]
    [Jan 2014]

    The article (1) by Gancedo and Strain in PNAS studies how singularities may develop in the initially smooth interfaces separating two or more incompressible fluids. The fluids and interfaces are assumed to evolve by either of the two standard systems of equations from fluid mechanics, namely the surface quasi-geostrophic (SQG)...
    Categories: Journal Articles
  • Unraveling the challenges of pertussis [Medical Sciences]
    [Jan 2014]

    The article by Warfel et al. in PNAS is noteworthy (1) because it shows that in nonhuman primate pertussis challenge models, acellular pertussis vaccines protect against disease but are ineffective in preventing infection and transmission to other animals. This highly relevant model sheds light on reasons that we are experiencing...
    Categories: Journal Articles
  • Sex difference in human brain architecture [Neuroscience]
    [Jan 2014]

    In PNAS, a report by Ingalhalikar et al. (1) has the makings of a landmark paper. Here I would like to briefly suggest why. Biomedical research in general, and neuroscience in particular, has been built on a false assumption. I refer to the assumption that one may safely ignore potential...
    Categories: Journal Articles
  • Species interactions and fisheries management [Ecology]
    [Jan 2014]

    Overfishing and environmental change have triggered many severe and unexpected consequences. As existing communities have collapsed, new ones have become established, fundamentally transforming ecosystems to those that are often less productive for fisheries, more prone to cycles of booms and busts, and thus less manageable. We contend that the failure...
    Categories: Journal Articles
  • X-ray nanocrystallographic reconstruction [Applied Mathematics]
    [Jan 2014]

    X-ray nanocrystallography allows the structure of a macromolecule to be determined from a large ensemble of nanocrystals. However, several parameters, including crystal sizes, orientations, and incident photon flux densities, are initially unknown and images are highly corrupted with noise. Autoindexing techniques, commonly used in conventional crystallography, can determine orientations using...
    Categories: Journal Articles
  • Vanadium ortho-diphosphate sodium ion battery [Applied Physical Sciences]
    [Jan 2014]

    Sodium ion batteries offer promising opportunities in emerging utility grid applications because of the low cost of raw materials, yet low energy density and limited cycle life remain critical drawbacks in their electrochemical operations. Herein, we report a vanadium-based ortho-diphosphate, Na7V4(P2O7)4PO4, or VODP, that significantly reduces all these drawbacks. Indeed,...
    Categories: Journal Articles
  • Imaging of wave functions [Applied Physical Sciences]
    [Jan 2014]

    The basis for a quantum-mechanical description of matter is electron wave functions. For atoms and molecules, their spatial distributions and phases are known as orbitals. Although orbitals are very powerful concepts, experimentally only the electron densities and -energy levels are directly observable. Regardless whether orbitals are observed in real space...
    Categories: Journal Articles
  • Mechanically interacting mammary acini [Applied Physical Sciences]
    [Jan 2014]

    Cells and multicellular structures can mechanically align and concentrate fibers in their ECM environment and can sense and respond to mechanical cues by differentiating, branching, or disorganizing. Here we show that mammary acini with compromised structural integrity can interconnect by forming long collagen lines. These collagen lines then coordinate and...
    Categories: Journal Articles
  • High-throughput multicolor ZMW instrument [Applied Physical Sciences]
    [Jan 2014]

    Zero-mode waveguides provide a powerful technology for studying single-molecule real-time dynamics of biological systems at physiological ligand concentrations. We customized a commercial zero-mode waveguide-based DNA sequencer for use as a versatile instrument for single-molecule fluorescence detection and showed that the system provides long fluorophore lifetimes with good signal to noise...
    Categories: Journal Articles