Proceedings of the Natural Academy of Sciences

Proceedings of the National Academy of Sciences RSS feed -- current issue
  • Phase transitions in dense hydrogen and deuterium [Physics]
    [Apr 2014]

    Raman spectroscopy of dense hydrogen and deuterium performed to 325 GPa at 300 K reveals previously unidentified transitions. Detailed analysis of the spectra from multiple experimental runs, together with comparison with previous infrared and Raman measurements, provides information on structural modifications of hydrogen as a function of density through the...
    Categories: Journal Articles
  • Hybridization gap and Fano resonance in SmB6 [Physics]
    [Apr 2014]

    Hybridization between conduction electrons and the strongly interacting f-electrons in rare earth or actinide compounds may result in new states of matter. Depending on the exact location of the concomitant hybridization gap with respect to the Fermi energy, a heavy fermion or an insulating ground state ensues. To study this...
    Categories: Journal Articles
  • Displacive transformations in colloidal crystals [Physics]
    [Apr 2014]

    The degree to which DNA-linked particle crystals, particularly those composed of micrometer-scale colloids, are able to dynamically evolve or whether they are kinetically arrested after formation remains poorly understood. Here, we study a recently observed displacive transformation in colloidal binary superlattice crystals, whereby a body-centered cubic to face-centered cubic transformation...
    Categories: Journal Articles
  • Science icescapes [Science and Culture]
    [Apr 2014]

    Scientists will go to the ends of the earth for data. They will drop themselves on a featureless ice sheet to measure a temperature or float down a mosquito-infested river for a few tablespoons of water. Seattle-based photographer Chris Linder follows them and uses his camera to bring science’s epic...
    Categories: Journal Articles
  • Testing for executive function in gibbons [Inner Workings]
    [Apr 2014]

    It is a commonly held assumption that we humans have a unique thinking ability that distinguishes us from other animals. However, every time scientists have tested that assumption—whether testing for self-recognition in a mirror, the existence of language, problem-solving ability, knowing what another is thinking (or “theory of mind”), deception,...
    Categories: Journal Articles
  • Imaging cycler microscopy [Biological Sciences]
    [Jan 2014]

    The article in PNAS by Gerdes et al. (1) adds to the evidence that spectral resolution limits of fluorescence microscopy can be overcome by reiterative cycles of tagging, imaging, and bleaching of fluorophores attached to ligands for target biomolecules. In fact, the robotic imaging cycler microscopes are based on this...
    Categories: Journal Articles
  • Highly multiplexed technologies [Biological Sciences]
    [Jan 2014]

    We are surprised by the concerns raised by Schubert et al. (1) regarding the quantitative nature and methodological approaches presented in our recent PNAS report (2). I will attempt to clarify some of confusion and misstatements, as several errors and misrepresentation of our data are stated in the critique. The...
    Categories: Journal Articles
  • Integrative pre-Columbian settlement model [Biological Sciences]
    [Jan 2014]

    Achilli et al. (1) present unique evidence concerning human mitogenomes and argue that such data are sufficient to generate a consensus scenario for the first settlement of the Americas. Here, we challenge their statement of having achieved a reconciling model because it ignores coherent ideas recently proposed by many researchers....
    Categories: Journal Articles
  • SQ-Dox nanoassemblies for anticancer therapy [Biochemistry]
    [Jan 2014]

    We identified that the chemical linkage of the anticancer drug doxorubicin onto squalene, a natural lipid precursor of the cholesterol’s biosynthesis, led to the formation of squalenoyl doxorubicin (SQ-Dox) nanoassemblies of 130-nm mean diameter, with an original “loop-train” structure. This unique nanomedicine demonstrates: (i) high drug payload, (ii) decreased toxicity...
    Categories: Journal Articles
  • Mechanics of myosin XXI [Biochemistry]
    [Jan 2014]

    Myosin XXI is the only myosin expressed in Leishmania parasites. Although it is assumed that it performs a variety of motile functions, the motor’s oligomerization states, cargo-binding, and motility are unknown. Here we show that binding of a single calmodulin causes the motor to adopt a monomeric state and to...
    Categories: Journal Articles
  • Apo-phytochromes modulate bacterial photosynthesis [Biochemistry]
    [Jan 2014]

    Bacteriophytochromes (BphPs) are light-sensing regulatory proteins encoded by photosynthetic and nonphotosynthetic bacteria. This protein class has been characterized structurally, but its biological activities remain relatively unexplored. Two BphPs in the anoxygenic photosynthetic bacterium Rhodopseudomonas palustris, designated regulatory proteins RpBphP2 and RpBphP3, are configured as light-regulated histidine kinases, which initiate a...
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  • TRIM14 builds mitochondrial antiviral signalosome [Microbiology]
    [Jan 2014]

    Innate immunity provides the first line of host defense against invading microbial pathogens. This defense involves retinoic acid-inducible gene-I–like receptors that detect viral RNA and activate the mitochondrial antiviral-signaling (MAVS) protein, an adaptor protein, leading to activation of the innate antiviral immune response. The mechanisms by which the MAVS signalosome...
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  • ParP mediates polar sequestration of CheA [Microbiology]
    [Jan 2014]

    Bacterial chemotaxis proteins are organized into ordered arrays. In peritrichous organisms, such as Escherichia coli, stochastic assembly processes are thought to account for the placement of chemotaxis arrays, which are nonuniformly distributed. In contrast, we previously found that chemotactic signaling arrays in polarly flagellated vibrios are uniformly polar and that...
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  • MCV vFLIPs inhibit TBK1 activation [Microbiology]
    [Jan 2014]

    Apoptosis, NF-κB activation, and IRF3 activation are a triad of intrinsic immune responses that play crucial roles in the pathogenesis of infectious diseases, cancer, and autoimmunity. FLIPs are a family of viral and cellular proteins initially found to inhibit apoptosis and more recently to either up- or down-regulate NF-κB. As...
    Categories: Journal Articles
  • Gate in voltage-gated proton channels [Neuroscience]
    [Jan 2014]

    Voltage-gated proton (Hv1) channels play important roles in the respiratory burst, in pH regulation, in spermatozoa, in apoptosis, and in cancer metastasis. Unlike other voltage-gated cation channels, the Hv1 channel lacks a centrally located pore formed by the assembly of subunits. Instead, the proton permeation pathway in the Hv1 channel...
    Categories: Journal Articles
  • Tissue specificity of MISS effects in vivo [Physiology]
    [Jan 2014]

    Estrogen receptor alpha (ERα) activation functions AF-1 and AF-2 classically mediate gene transcription in response to estradiol (E2). A fraction of ERα is targeted to plasma membrane and elicits membrane-initiated steroid signaling (MISS), but the physiological roles of MISS in vivo are poorly understood. We therefore generated a mouse with...
    Categories: Journal Articles
  • Active visual sampling [Psychological and Cognitive Sciences]
    [Jan 2014]

    Human vision is an active process in which information is sampled during brief periods of stable fixation in between gaze shifts. Foveal analysis serves to identify the currently fixated object and has to be coordinated with a peripheral selection process of the next fixation location. Models of visual search and...
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  • Integrated model of root vascular patterning [Plant Biology]
    [Jan 2014]

    As multicellular organisms grow, positional information is continually needed to regulate the pattern in which cells are arranged. In the Arabidopsis root, most cell types are organized in a radially symmetric pattern; however, a symmetry-breaking event generates bisymmetric auxin and cytokinin signaling domains in the stele. Bidirectional cross-talk between the...
    Categories: Journal Articles
  • AtAtg8 cleavage specificity by AtAtg4 proteases [Plant Biology]
    [Jan 2014]

    Autophagy is a highly conserved biological process during which double membrane bound autophagosomes carry intracellular cargo material to the vacuole or lysosome for degradation and/or recycling. Autophagosome biogenesis requires Autophagy 4 (Atg4) cysteine protease-mediated processing of ubiquitin-like Atg8 proteins. Unlike single Atg4 and Atg8 genes in yeast, the Arabidopsis genome...
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  • Biomarkers of sex differences in vaccine responses [Systems Biology]
    [Jan 2014]

    Females have generally more robust immune responses than males for reasons that are not well-understood. Here we used a systems analysis to investigate these differences by analyzing the neutralizing antibody response to a trivalent inactivated seasonal influenza vaccine (TIV) and a large number of immune system components, including serum cytokines...
    Categories: Journal Articles