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Direct measurement of DNA dielectric constant [Biophysics and Computational Biology]

PNAS Early Edition Articles - Mon, 08/18/2014 - 13:12
The electric polarizability of DNA, represented by the dielectric constant, is a key intrinsic property that modulates DNA interaction with effector proteins. Surprisingly, it has so far remained unknown owing to the lack of experimental tools able to access it. Here, we experimentally resolved it by detecting the ultraweak polarization...

Systems vaccinology [Biological Sciences]

PNAS Early Edition Articles - Mon, 08/18/2014 - 13:12
Homo sapiens are genetically diverse, but dramatic demographic and socioeconomic changes during the past century have created further diversification with respect to age, nutritional status, and the incidence of associated chronic inflammatory disorders and chronic infections. These shifting demographics pose new challenges for vaccination, as emerging evidence suggests that age,...

Reactivating the mammalian inactive X chromosome [Cell Biology]

PNAS Early Edition Articles - Mon, 08/18/2014 - 13:12
X-chromosome inactivation (XCI), the random transcriptional silencing of one X chromosome in somatic cells of female mammals, is a mechanism that ensures equal expression of X-linked genes in both sexes. XCI is initiated in cis by the noncoding Xist RNA, which coats the inactive X chromosome (Xi) from which it...

Rescue of arrested RNAPII by H2B deubiquitylation [Genetics]

PNAS Early Edition Articles - Mon, 08/18/2014 - 13:12
Histone H2B monoubiquitylation plays an important role in RNA polymerase II (RNAPII) elongation. Whether this modification responds to RNAPII stalling is not yet known. We report that both yeast and human cells undergo a rapid and significant H2B deubiquitylation after exposure to UV irradiation. This deubiquitylation occurs concurrently with UV-induced...

Gyrification from constrained cortical expansion [Biophysics and Computational Biology]

PNAS Early Edition Articles - Mon, 08/18/2014 - 13:12
The exterior of the mammalian brain—the cerebral cortex—has a conserved layered structure whose thickness varies little across species. However, selection pressures over evolutionary time scales have led to cortices that have a large surface area to volume ratio in some organisms, with the result that the brain is strongly convoluted...

Label-free probe of TAT peptide binding to vesicles [Biophysics and Computational Biology]

PNAS Early Edition Articles - Mon, 08/18/2014 - 13:12
The transacting activator of transduction (TAT) protein plays a key role in the progression of AIDS. Studies have shown that a +8 charged sequence of amino acids in the protein, called the TAT peptide, enables the TAT protein to penetrate cell membranes. To probe mechanisms of binding and translocation of...

Submesoscale oil spill transport [Environmental Sciences]

PNAS Early Edition Articles - Mon, 08/18/2014 - 13:12
Reliable forecasts for the dispersion of oceanic contamination are important for coastal ecosystems, society, and the economy as evidenced by the Deepwater Horizon oil spill in the Gulf of Mexico in 2010 and the Fukushima nuclear plant incident in the Pacific Ocean in 2011. Accurate prediction of pollutant pathways and...

Evolution of the African pygmy phenotype [Anthropology]

PNAS Early Edition Articles - Mon, 08/18/2014 - 13:12
The evolutionary history of the human pygmy phenotype (small body size), a characteristic of African and Southeast Asian rainforest hunter-gatherers, is largely unknown. Here we use a genome-wide admixture mapping analysis to identify 16 genomic regions that are significantly associated with the pygmy phenotype in the Batwa, a rainforest hunter-gatherer...

Mannan-induced inflammation [Immunology and Inflammation]

PNAS Early Edition Articles - Mon, 08/18/2014 - 13:12
Psoriasis (Ps) and psoriasis arthritis (PsA) are poorly understood common diseases, induced by unknown environmental factors, affecting skin and articular joints. A single i.p. exposure to mannan from Saccharomyces cerevisiae induced an acute inflammation in inbred mouse strains resembling human Ps and PsA-like disease, whereas multiple injections induced a relapsing...

Artificial adaptive camouflage skins [Engineering]

PNAS Early Edition Articles - Mon, 08/18/2014 - 13:12
Octopus, squid, cuttlefish, and other cephalopods exhibit exceptional capabilities for visually adapting to or differentiating from the coloration and texture of their surroundings, for the purpose of concealment, communication, predation, and reproduction. Long-standing interest in and emerging understanding of the underlying ultrastructure, physiological control, and photonic interactions has recently led...

Diffraction from cells yields protein structure [Biophysics and Computational Biology]

PNAS Early Edition Articles - Mon, 08/18/2014 - 13:12
It has long been known that toxins produced by Bacillus thuringiensis (Bt) are stored in the bacterial cells in crystalline form. Here we describe the structure determination of the Cry3A toxin found naturally crystallized within Bt cells. When whole Bt cells were streamed into an X-ray free-electron laser beam we...

Pseudomonas triggers CFTR-mediated ASL secretion [Physiology]

PNAS Early Edition Articles - Mon, 08/18/2014 - 13:12
Cystic fibrosis (CF) is an autosomal recessive genetic disorder caused by mutations in the gene encoding for the anion channel cystic fibrosis transmembrane conductance regulator (CFTR). Several organs are affected in CF, but most of the morbidity and mortality comes from lung disease. Recent data show that the initial consequence...

Adaptive growth factor delivery for bone repair [Medical Sciences]

PNAS Early Edition Articles - Mon, 08/18/2014 - 13:12
Traumatic wounds and congenital defects that require large-scale bone tissue repair have few successful clinical therapies, particularly for craniomaxillofacial defects. Although bioactive materials have demonstrated alternative approaches to tissue repair, an optimized materials system for reproducible, safe, and targeted repair remains elusive. We hypothesized that controlled, rapid bone formation in...

Climate change threatens desert fishes [Environmental Sciences]

PNAS Early Edition Articles - Mon, 08/18/2014 - 13:12
Protecting hydrologic connectivity of freshwater ecosystems is fundamental to ensuring species persistence, ecosystem integrity, and human well-being. More frequent and severe droughts associated with climate change are poised to significantly alter flow intermittence patterns and hydrologic connectivity in dryland streams of the American Southwest, with deleterious effects on highly endangered...

Opposite effects of hybridization [Evolution]

PNAS Early Edition Articles - Mon, 08/18/2014 - 13:12
Hybridization is not a mere reproductive dead end but has been suggested to play a central role in speciation, for example, by introducing adaptive genetic variation. Our previous study uncovered a unique consequence of hybridization in Formica ants. In a population including two isolated but partially introgressed genetic groups, the...

Orientation-dependent X-ray dark-field tomography [Physics]

PNAS Early Edition Articles - Mon, 08/18/2014 - 13:12
Grating-based X-ray dark-field imaging is a novel technique for obtaining image contrast for object structures at size scales below setup resolution. Such an approach appears particularly beneficial for medical imaging and nondestructive testing. It has already been shown that the dark-field signal depends on the direction of observation. However, up...

Vaccines against poverty [Biological Sciences]

PNAS Early Edition Articles - Mon, 08/18/2014 - 13:12
With the 2010s declared the Decade of Vaccines, and Millennium Development Goals 4 and 5 focused on reducing diseases that are potentially vaccine preventable, now is an exciting time for vaccines against poverty, that is, vaccines against diseases that disproportionately affect low- and middle-income countries (LMICs). The Global Burden of...

In-group favoritism in children's punishment [Psychological and Cognitive Sciences]

PNAS Early Edition Articles - Mon, 08/18/2014 - 13:12
When enforcing norms for cooperative behavior, human adults sometimes exhibit in-group bias. For example, third-party observers punish selfish behaviors committed by out-group members more harshly than similar behaviors committed by in-group members. Although evidence suggests that children begin to systematically punish selfish behavior around the age of 6 y, the...

Microbial co-occurrence in streams [Environmental Sciences]

PNAS Early Edition Articles - Mon, 08/18/2014 - 13:12
Recent studies highlight linkages among the architecture of ecological networks, their persistence facing environmental disturbance, and the related patterns of biodiversity. A hitherto unresolved question is whether the structure of the landscape inhabited by organisms leaves an imprint on their ecological networks. We analyzed, based on pyrosequencing profiling of the...

Woody-plant encroachment and livestock production [Sustainability Science]

PNAS Early Edition Articles - Mon, 08/18/2014 - 13:12
A large fraction of the world grasslands and savannas are undergoing a rapid shift from herbaceous to woody-plant dominance. This land-cover change is expected to lead to a loss in livestock production (LP), but the impacts of woody-plant encroachment on this crucial ecosystem service have not been assessed. We evaluate...
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