Proceedings of the Natural Academy of Sciences

Proceedings of the National Academy of Sciences RSS feed -- current issue
  • ABCA4 retinoid transport activity [Neuroscience]
    [Apr 2014]

    The visual cycle is a series of enzyme-catalyzed reactions which converts all-trans-retinal to 11-cis-retinal for the regeneration of visual pigments in rod and cone photoreceptor cells. Although essential for vision, 11-cis-retinal like all-trans-retinal is highly toxic due to its highly reactive aldehyde group and has to be detoxified by either...
    Categories: Journal Articles
  • Vesicular codelivery of AMPARs and N-cadherin [Neuroscience]
    [Apr 2014]

    The GluA2 subunit of AMPA-type glutamate receptors (AMPARs) regulates excitatory synaptic transmission in neurons. In addition, the transsynaptic cell adhesion molecule N-cadherin controls excitatory synapse function and stabilizes dendritic spine structures. At postsynaptic membranes, GluA2 physically binds N-cadherin, underlying spine growth and synaptic modulation. We report that N-cadherin binds to...
    Categories: Journal Articles
  • PDE4A loss puts aging PFC at risk for degeneration [Neuroscience]
    [Apr 2014]

    The pattern of neurodegeneration in Alzheimer’s disease (AD) is very distinctive: neurofibrillary tangles (NFTs) composed of hyperphosphorylated tau selectively affect pyramidal neurons of the aging association cortex that interconnect extensively through glutamate synapses on dendritic spines. In contrast, primary sensory cortices have few NFTs, even in late-stage disease. Understanding this...
    Categories: Journal Articles
  • EphA7 signaling in cortical dendritic maturation [Physics]
    [Apr 2014]

    The process by which excitatory neurons are generated and mature during the development of the cerebral cortex occurs in a stereotyped manner; coordinated neuronal birth, migration, and differentiation during embryonic and early postnatal life are prerequisites for selective synaptic connections that mediate meaningful neurotransmission in maturity. Normal cortical function depends...
    Categories: Journal Articles
  • In vivo thylakoid remodeling by state transitions [Plant Biology]
    [Apr 2014]

    Plants respond to changes in light quality by regulating the absorption capacity of their photosystems. These short-term adaptations use redox-controlled, reversible phosphorylation of the light-harvesting complexes (LHCIIs) to regulate the relative absorption cross-section of the two photosystems (PSs), commonly referred to as state transitions. It is acknowledged that state transitions...
    Categories: Journal Articles
  • Space, time, and number in neonates [Psychological and Cognitive Sciences]
    [Apr 2014]

    A rich concept of magnitude—in its numerical, spatial, and temporal forms—is a central foundation of mathematics, science, and technology, but the origins and developmental relations among the abstract concepts of number, space, and time are debated. Are the representations of these dimensions and their links tuned by extensive experience, or...
    Categories: Journal Articles
  • Value and salience in the human brain [Psychological and Cognitive Sciences]
    [Apr 2014]

    A large body of evidence has implicated the posterior parietal and orbitofrontal cortex in the processing of value. However, value correlates perfectly with salience when appetitive stimuli are investigated in isolation. Accordingly, considerable uncertainty has remained about the precise nature of the previously identified signals. In particular, recent evidence suggests...
    Categories: Journal Articles
  • Exploiting polypharmacology [Systems Biology]
    [Apr 2014]

    Polypharmacology (action of drugs against multiple targets) represents a tempting avenue for new drug development; unfortunately, methods capable of exploiting the known polypharmacology of drugs for target deconvolution are lacking. Here, we present an ensemble approach using elastic net regularization combined with mRNA expression profiling and previously characterized data on...
    Categories: Journal Articles
  • In This Issue [This Week in PNAS]
    [Apr 2014]

    Breast cancer gene implicated in brain size control Deletion of BRCA1 within the neural stemcell/progenitor compartment (Nestin-CRE) in an E12.5 mouse embryo displays abnormally high levels of apoptosis as defined by activated Caspase 3 signal (green). The breast cancer susceptibility gene 1 (BRCA1) is a tumor suppressor gene known to...
    Categories: Journal Articles
  • Catch of the day: the HTL translocon [Biochemistry]
    [Apr 2014]

    Protein transport is a fundamental activity for all living cells and an exciting area for scientific exploration (1, 2). In bacteria, the process depends on the concerted action of at least three membrane-embedded components: the ubiquitous SecYEG complex that forms the polypeptide-conducting membrane pore, the essential YidC insertase that works...
    Categories: Journal Articles
  • Plasmid segregation by a moving ATPase gradient [Cell Biology]
    [Apr 2014]

    Unlike the mitotic segregation of eukaryotic sister chromatids, DNA partitioning in bacteria is still not well understood. Bacterial high–copy-number plasmids can be stably maintained by random distribution of their copies during cell division. In contrast, the faithful transmission of low–copy-number plasmids and many chromosomes depends on an active process mediated...
    Categories: Journal Articles
  • Diet, dementia, and diabetes [Medical Sciences]
    [Apr 2014]

    It is becoming abundantly clear that the insight into the pathological process of Alzheimer’s disease (AD) provided through autosomal dominant variants of the condition is only a partial one. The formation and aggregation of Aβ and the phosphorylation and aggregation of tau are clearly part of the core pathogenesis. However,...
    Categories: Journal Articles
  • Diverse cells at the origin of lung adenocarcinoma [Medical Sciences]
    [Apr 2014]

    Oncogenic mutations in Kirsten rat sarcoma viral oncogene homologue (K-RAS) are found in a broad range of aggressive cancers in many tissues and are common in the most prevalent form of lung cancer, adenocarcinoma (1). Despite knowledge of K-RAS mutations for many years, patients with K-RAS mutant tumors remain without...
    Categories: Journal Articles
  • How biological vision succeeds [Neuroscience]
    [Apr 2014]

    Biological visual systems cannot measure the properties that define the physical world. Nonetheless, visually guided behaviors of humans and other animals are routinely successful. The purpose of this article is to consider how this feat is accomplished. Most concepts of vision propose, explicitly or implicitly, that visual behavior depends on...
    Categories: Journal Articles
  • Multidimensional spectroscopy of photoreactivity [Chemistry]
    [Apr 2014]

    Coherent multidimensional electronic spectroscopy is commonly used to investigate photophysical phenomena such as light harvesting in photosynthesis in which the system returns back to its ground state after energy transfer. By contrast, we introduce multidimensional spectroscopy to study ultrafast photochemical processes in which the investigated molecule changes permanently. Exemplarily, the...
    Categories: Journal Articles
  • Unexpected trapping of particles at a T junction [Engineering]
    [Apr 2014]

    A common element in physiological flow networks, as well as most domestic and industrial piping systems, is a T junction that splits the flow into two nearly symmetric streams. It is reasonable to assume that any particles suspended in a fluid that enters the bifurcation will leave it with the...
    Categories: Journal Articles
  • Tuning threshold voltage of SWNT transistors [Engineering]
    [Apr 2014]

    Tuning the threshold voltage of a transistor is crucial for realizing robust digital circuits. For silicon transistors, the threshold voltage can be accurately controlled by doping. However, it remains challenging to tune the threshold voltage of single-wall nanotube (SWNT) thin-film transistors. Here, we report a facile method to controllably n-dope...
    Categories: Journal Articles
  • Metal availability and N isotope fractionation [Environmental Sciences]
    [Apr 2014]

    Biological nitrogen fixation constitutes the main input of fixed nitrogen to Earth’s ecosystems, and its isotope effect is a key parameter in isotope-based interpretations of the N cycle. The nitrogen isotopic composition (δ15N) of newly fixed N is currently believed to be ∼–1‰, based on measurements of organic matter from...
    Categories: Journal Articles
  • River discharge from satellite images and AMHG [Environmental Sciences]
    [Apr 2014]

    Rivers provide critical water supply for many human societies and ecosystems, yet global knowledge of their flow rates is poor. We show that useful estimates of absolute river discharge (in cubic meters per second) may be derived solely from satellite images, with no ground-based or a priori information whatsoever. The...
    Categories: Journal Articles
  • Marked clones in Drosophila mosaics [Genetics]
    [Apr 2014]

    Chimaeras, fanciful beasts that drew their force from being composed of parts of disparate animals, have stimulated our collective imagination for centuries. In modern terms, chimaeras are composite animals consisting of genetically distinct cell populations and are called “mosaics” if the different cell types have emerged from the same zygote....
    Categories: Journal Articles