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Ten million tonnes of impact spherules at 12.8 ka [Earth, Atmospheric, and Planetary Sciences]

PNAS Early Edition Articles - Mon, 05/20/2013 - 12:46
Airbursts/impacts by a fragmented comet or asteroid have been proposed at the Younger Dryas onset (12.80 ± 0.15 ka) based on identification of an assemblage of impact-related proxies, including microspherules, nanodiamonds, and iridium. Distributed across four continents at the Younger Dryas boundary (YDB), spherule peaks have been independently confirmed in...

Entropy-driven crystal formation [Physics]

PNAS Early Edition Articles - Mon, 05/20/2013 - 12:46
In heteroepitaxy, lattice mismatch between the deposited material and the underlying surface strongly affects nucleation and growth processes. The effect of mismatch is well studied in atoms with growth kinetics typically dominated by bond formation with interaction lengths on the order of one lattice spacing. In contrast, less is understood...

Evolution of flightlessness in diving birds [Evolution]

PNAS Early Edition Articles - Mon, 05/20/2013 - 12:46
Flight is a key adaptive trait. Despite its advantages, flight has been lost in several groups of birds, notably among seabirds, where flightlessness has evolved independently in at least five lineages. One hypothesis for the loss of flight among seabirds is that animals moving between different media face tradeoffs between...

Anti-CD47 primes antitumor T-cell response [Medical Sciences]

PNAS Early Edition Articles - Mon, 05/20/2013 - 12:46
Mobilization of the T-cell response against cancer has the potential to achieve long-lasting cures. However, it is not known how to harness antigen-presenting cells optimally to achieve an effective antitumor T-cell response. In this study, we show that anti-CD47 antibody–mediated phagocytosis of cancer by macrophages can initiate an antitumor T-cell...

Genetic screens to identify pathogenic variants [Genetics]

PNAS Early Edition Articles - Mon, 05/20/2013 - 12:46
In many individuals suspected of the common cancer predisposition Lynch syndrome, variants of unclear significance (VUS), rather than an obviously pathogenic mutations, are identified in one of the DNA mismatch repair (MMR) genes. The uncertainty of whether such VUS inactivate MMR, and therefore are pathogenic, precludes targeted healthcare for both...

Visual arrestin interaction with AP-2 in rods [Medical Sciences]

PNAS Early Edition Articles - Mon, 05/20/2013 - 12:46
Arrestins bind ligand-activated, phosphorylated G protein-coupled receptors (GPCRs) and terminate the activation of G proteins. Additionally, nonvisual arrestin/GPCR complex can initiate G protein-independent intracellular signals through their ability to act as scaffolds that bring other signaling molecules to the internalized GPCR. Like nonvisual arrestins, vertebrate visual arrestin (ARR1) terminates G...

Inhibition of MSC differentiation by NF-{kappa}B [Medical Sciences]

PNAS Early Edition Articles - Mon, 05/20/2013 - 12:46
Mesenchymal stem cell (MSC)-based transplantation is a promising therapeutic approach for bone regeneration and repair. In the realm of therapeutic bone regeneration, the defect or injured tissues are frequently inflamed with an abnormal expression of inflammatory mediators. Growing evidence suggests that proinflammatory cytokines inhibit osteogenic differentiation and bone formation. Thus,...

Cryoelectron tomography of HCV [Microbiology]

PNAS Early Edition Articles - Mon, 05/20/2013 - 12:46
Hepatitis C virus (HCV) is a major cause of chronic liver disease, with an estimated 170 million people infected worldwide. Low yields, poor stability, and inefficient binding to conventional EM grids have posed significant challenges to the purification and structural analysis of HCV. In this report, we generated an infectious...

Intracellular pH imaging with bioluminescence [Chemistry]

PNAS Early Edition Articles - Mon, 05/20/2013 - 12:45
Regulation of an intracellular acidic environment plays a pivotal role in biological processes and functions. However, spatiotemporal analysis of the acidification in complex tissues of living subjects persists as an important challenge. We developed a photo-inactivatable bioluminescent indicator, based on a combination of luciferase-fragment complementation and a photoreaction of a...

Diet affects susceptibility to E. coli O157:H7 [Microbiology]

PNAS Early Edition Articles - Mon, 05/20/2013 - 12:45
The likelihood that a single individual infected with the Shiga toxin (Stx)-producing, food-borne pathogen Escherichia coli O157:H7 will develop a life-threatening sequela called the hemolytic uremic syndrome is unpredictable. We reasoned that conditions that enhance Stx binding and uptake within the gut after E. coli O157:H7 infection should result in...

Deliberate reduction of HA and NA for live vaccine [Microbiology]

PNAS Early Edition Articles - Mon, 05/20/2013 - 12:45
A long-held dogma posits that strong presentation to the immune system of the dominant influenza virus glycoprotein antigens neuraminidase (NA) and hemagglutinin (HA) is paramount for inducing protective immunity against influenza virus infection. We have deliberately violated this dogma by constructing a recombinant influenza virus strain of A/PR8/34 (H1N1) in...

Superconductivity and magnetism in Fe1-xPdxTe [Physics]

PNAS Early Edition Articles - Mon, 05/20/2013 - 12:45
The attractive/repulsive relationship between superconductivity and magnetic ordering has fascinated the condensed matter physics community for a century. In the early days, magnetic impurities doped into a superconductor were found to quickly suppress superconductivity. Later, a variety of systems, such as cuprates, heavy fermions, and Fe pnictides, showed superconductivity in...

Nematic boojums on colloidal handlebodies [Applied Physical Sciences]

PNAS Early Edition Articles - Mon, 05/20/2013 - 12:45
Topological defects that form on surfaces of ordered media, dubbed boojums, are ubiquitous in superfluids, liquid crystals (LCs), Langmuir monolayers, and Bose–Einstein condensates. They determine supercurrents in superfluids, impinge on electrooptical switching in polymer-dispersed LCs, and mediate chemical response at nematic-isotropic fluid interfaces, but the role of surface topology in...

Glutaredoxin contains GIY-YIG endonuclease motif [Plant Biology]

PNAS Early Edition Articles - Mon, 05/20/2013 - 12:45
Glutaredoxins (Grxs) have been identified across taxa as important mediators in various physiological functions. A chloroplastic monothiol glutaredoxin, AtGRXS16 from Arabidopsis thaliana, comprises two distinct functional domains, an N-terminal domain (NTD) with GlyIleTyr-TyrIleGly (GIY-YIG) endonuclease motif and a C-terminal Grx module, to coordinate redox regulation and DNA cleavage in chloroplasts....

Ecosystem services in the Panama Canal watershed [Sustainability Science]

PNAS Early Edition Articles - Mon, 05/20/2013 - 12:45
Land cover change in watersheds affects the supply of a number of ecosystem services, including water supply, the production of timber and nontimber forest products, the provision of habitat for forest species, and climate regulation through carbon sequestration. The Panama Canal watershed is currently being reforested to protect the dry-season...

Circadian clock and hair cycle [Cell Biology]

PNAS Early Edition Articles - Mon, 05/20/2013 - 12:45
Regenerative cycling of hair follicles offers an unique opportunity to explore the role of circadian clock in physiological tissue regeneration. We focused on the role of circadian clock in actively proliferating transient amplifying cells, as opposed to quiescent stem cells. We identified two key sites of peripheral circadian clock activity...

Measuring microbubble viscosity using FLIM [Applied Physical Sciences]

PNAS Early Edition Articles - Mon, 05/20/2013 - 12:45
Encapsulated microbubbles are well established as highly effective contrast agents for ultrasound imaging. There remain, however, some significant challenges to fully realize the potential of microbubbles in advanced applications such as perfusion mapping, targeted drug delivery, and gene therapy. A key requirement is accurate characterization of the viscoelastic surface properties...

Mesoamerican monsoon 22,000-y history [Earth, Atmospheric, and Planetary Sciences]

PNAS Early Edition Articles - Mon, 05/20/2013 - 12:45
The dominant controls on global paleomonsoon strength include summer insolation driven by precession cycles, ocean circulation through its influence on atmospheric circulation, and sea-surface temperatures. However, few records from the summer North American Monsoon system are available to test for a synchronous response with other global monsoons to shared forcings....

Community-based adaptation & community relocations [Sustainability Science]

PNAS Early Edition Articles - Mon, 05/20/2013 - 12:45
This article presents governance and institutional strategies for climate-induced community relocations. In Alaska, repeated extreme weather events coupled with climate change-induced coastal erosion impact the habitability of entire communities. Community residents and government agencies concur that relocation is the only adaptation strategy that can protect lives and infrastructure. Community relocation...

Prosaptide & prosaposin activate GPR37 & GPR37L1 [Neuroscience]

PNAS Early Edition Articles - Mon, 05/20/2013 - 12:45
GPR37 (also known as Pael-R) and GPR37L1 are orphan G protein-coupled receptors that are almost exclusively expressed in the nervous system. We screened these receptors for potential activation by various orphan neuropeptides, and these screens yielded a single positive hit: prosaptide, which promoted the endocytosis of GPR37 and GPR37L1, bound...
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