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Arctic and Antarctic ozone depletion [Earth, Atmospheric, and Planetary Sciences]

PNAS Early Edition Articles - Mon, 04/14/2014 - 13:08
Antarctic ozone depletion is associated with enhanced chlorine from anthropogenic chlorofluorocarbons and heterogeneous chemistry under cold conditions. The deep Antarctic “hole” contrasts with the generally weaker depletions observed in the warmer Arctic. An unusually cold Arctic stratospheric season occurred in 2011, raising the question of how the Arctic ozone chemistry...

Marine bacterial taxon with large carbon footprint [Environmental Sciences]

PNAS Early Edition Articles - Mon, 04/14/2014 - 13:08
Marine dissolved organic carbon (DOC) encompasses one of the largest reservoirs of carbon on Earth. Heterotrophic bacteria are the primary biotic force regulating the fate of this material, yet the capacity of individual strains to significantly contribute to carbon cycling is unknown. Here we quantified the ability of a single...

Host-derived PFTs in immunity [Immunology]

PNAS Early Edition Articles - Mon, 04/14/2014 - 13:08
Aerolysins are virulence factors belonging to the bacterial β-pore–forming toxin superfamily. Surprisingly, numerous aerolysin-like proteins exist in vertebrates, but their biological functions are unknown. βγ-CAT, a complex of an aerolysin-like protein subunit (two βγ-crystallin domains followed by an aerolysin pore-forming domain) and two trefoil factor subunits, has been identified in...

Assessing the effects of anthropogenic aerosols [Environmental Sciences]

PNAS Early Edition Articles - Mon, 04/14/2014 - 13:08
Atmospheric aerosols affect weather and global general circulation by modifying cloud and precipitation processes, but the magnitude of cloud adjustment by aerosols remains poorly quantified and represents the largest uncertainty in estimated forcing of climate change. Here we assess the effects of anthropogenic aerosols on the Pacific storm track, using...

Preventing influenza by targeting host receptors [Microbiology]

PNAS Early Edition Articles - Mon, 04/14/2014 - 13:08
There is a need for new approaches for the control of influenza given the burden caused by annual seasonal outbreaks, the emergence of viruses with pandemic potential, and the development of resistance to current antiviral drugs. We show that multivalent biologics, engineered using carbohydrate-binding modules specific for sialic acid, mask...

von Willebrand factor links sodium to thrombosis [Physiology]

PNAS Early Edition Articles - Mon, 04/14/2014 - 13:08
Hypercoagulability increases risk of thrombi that cause cardiovascular events. Here we identify plasma sodium concentration as a factor that modulates blood coagulability by affecting the production of von Willebrand factor (vWF), a key initiator of the clotting cascade. We find that elevation of salt over a range from the lower...

Acetyl-CoA cleavage and CO release in D. mccartyi [Microbiology]

PNAS Early Edition Articles - Mon, 04/14/2014 - 13:08
The acetyl-CoA “Wood–Ljungdahl” pathway couples the folate-mediated one-carbon (C1) metabolism to either CO2 reduction or acetate oxidation via acetyl-CoA. This pathway is distributed in diverse anaerobes and is used for both energy conservation and assimilation of C1 compounds. Genome annotations for all sequenced strains of Dehalococcoides mccartyi, an important bacterium...

Measuring pKas of His in invisible protein states [Biophysics and Computational Biology]

PNAS Early Edition Articles - Mon, 04/14/2014 - 13:08
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...

Vacuolar K+ controls stomatal activity [Plant Biology]

PNAS Early Edition Articles - Mon, 04/14/2014 - 13:08
Stomatal movements rely on alterations in guard cell turgor. This requires massive K+ bidirectional fluxes across the plasma and tonoplast membranes. Surprisingly, given their physiological importance, the transporters mediating the energetically uphill transport of K+ into the vacuole remain to be identified. Here, we report that, in Arabidopsis guard cells,...

Tau mutants bind tubulin with enhanced affinity [Biophysics and Computational Biology]

PNAS Early Edition Articles - Mon, 04/14/2014 - 13:08
Tau is a microtubule binding protein that forms pathological aggregates in the brain in Alzheimer’s disease and other tauopathies. Disease etiology is thought to arise from loss of native interactions between tau and microtubules, as well as from gain of toxicity tied to tau aggregation, although neither mechanism is well...

Tetherin antagonism by Vpu protects HIV from ADCC [Microbiology]

PNAS Early Edition Articles - Mon, 04/14/2014 - 13:08
Tetherin is an IFN-inducible transmembrane protein that inhibits the detachment of enveloped viruses from infected cells. HIV-1 overcomes this restriction factor by expressing HIV-1 viral protein U (Vpu), which down-regulates and degrades tetherin. We report that mutations in Vpu that impair tetherin antagonism increase the susceptibility of HIV-infected cells to...

Stochastic epigenetic variation and evolution [Evolution]

PNAS Early Edition Articles - Mon, 04/14/2014 - 13:08
Evolution by gene duplication is generally accepted as one of the crucial driving forces for the gain of new complexity and functions, but the formation of pseudogenes remains a problem for this mechanism. Here we expand on earlier ideas that epigenetic modifications can drive neo- and subfunctionalization in evolution by...

Mesocircuit dysfunction after severe brain injury [Neuroscience]

PNAS Early Edition Articles - Mon, 04/14/2014 - 13:08
Although disorders of consciousness (DOCs) demonstrate widely varying clinical presentations and patterns of structural injury, global down-regulation and bilateral reductions in metabolism of the thalamus and frontoparietal network are consistent findings. We test the hypothesis that global reductions of background synaptic activity in DOCs will associate with changes in the...

Alphaviral infection triggers pathologic bone loss [Microbiology]

PNAS Early Edition Articles - Mon, 04/14/2014 - 13:08
Arthritogenic alphaviruses including Ross River virus (RRV), Sindbis virus, and chikungunya virus cause worldwide outbreaks of musculoskeletal disease. The ability of alphaviruses to induce bone pathologies remains poorly defined. Here we show that primary human osteoblasts (hOBs) can be productively infected by RRV. RRV-infected hOBs produced high levels of inflammatory...

Sfp1, a protein mediating sea star tenacity [Cell Biology]

PNAS Early Edition Articles - Mon, 04/14/2014 - 13:08
Sea stars adhere firmly but temporarily to various substrata as a result of underwater efficient adhesive secretions released by their tube feet. Previous studies showed that this material is mainly made up of proteins, which play a key role in its adhesiveness and cohesiveness. Recently, we solubilized the majority of...

Younger Dryas warming and deglaciation in Scotland [Earth, Atmospheric, and Planetary Sciences]

PNAS Early Edition Articles - Mon, 04/14/2014 - 13:08
The Younger Dryas Stadial (YDS; ∼12,900–11,600 y ago) in the Northern Hemisphere is classically defined by abrupt cooling and renewed glaciation during the last glacial–interglacial transition. Although this event involved a global reorganization of atmospheric and oceanic circulation [Denton GH, Alley RB, Comer GC, Broecker WS (2005) Quat Sci Rev...

Humoral responses to Forssman after PROSTVAC-VF [Medical Sciences]

PNAS Early Edition Articles - Mon, 04/14/2014 - 13:08
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...

Uridylation of miRNAs and 5' cleavage products [Genetics]

PNAS Early Edition Articles - Mon, 04/14/2014 - 13:08
In plants, methylation catalyzed by HEN1 (small RNA methyl transferase) prevents microRNAs (miRNAs) from degradation triggered by uridylation. How methylation antagonizes uridylation of miRNAs in vivo is not well understood. In addition, 5′ RNA fragments (5′ fragments) produced by miRNA-mediated RNA cleavage can be uridylated in plants and animals. However,...

MoS2/WSe2 van der Waals heterostructures [Applied Physical Sciences]

PNAS Early Edition Articles - Mon, 04/14/2014 - 13:08
Semiconductor heterostructures are the fundamental platform for many important device applications such as lasers, light-emitting diodes, solar cells, and high-electron-mobility transistors. Analogous to traditional heterostructures, layered transition metal dichalcogenide heterostructures can be designed and built by assembling individual single layers into functional multilayer structures, but in principle with atomically sharp...

Discovery of LPMO activity on hemicelluloses [Biochemistry]

PNAS Early Edition Articles - Mon, 04/14/2014 - 13:08
The recently discovered lytic polysaccharide monooxygenases (LPMOs) are known to carry out oxidative cleavage of glycoside bonds in chitin and cellulose, thus boosting the activity of well-known hydrolytic depolymerizing enzymes. Because biomass-degrading microorganisms tend to produce a plethora of LPMOs, and considering the complexity and copolymeric nature of the plant...
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