A bizarre change occurs in the mouth of a humpback whale during its development in the womb. Several dozen tooth buds sprout in a row […]

The post Paleo-detectives energize great whale mystery: how & when baleen evolved appeared first on Smithsonian Insider.

Two separate teams of scientists have identified major challenges for the development of life in what has recently become one of the most famous exoplanet […]

The post There’s more to extraterrestrial life than planets in “habitable zone” orbits appeared first on Smithsonian Insider.

The world’s most indestructible species, the tardigrade, an eight-legged micro-animal, also known as the water bear, will survive until the Sun dies, according to a […]

The post Study determines microscopic water bears will be Earth’s last survivors appeared first on Smithsonian Insider.

When fast radio bursts, or FRBs, were first detected in 2001, astronomers had never seen anything like them before. Since then, astronomers have found a […]

The post New study indicates mysterious fast radio bursts occur in universe every second appeared first on Smithsonian Insider.

With a non-stop babble of hums, grunts and shrill squeals as they argue over fish and defend their territories, the Amazon’s giant otters are one […]

The post With voices joined in chorus, giant otter families create a distinct sound signature appeared first on Smithsonian Insider.

Astronomers had a mystery on their hands. No matter where they looked, from inside the Milky Way to distant galaxies, they observed a puzzling glow […]

The post GBT Detection Unlocks Exploration of ‘Aromatic’ Interstellar Chemistry appeared first on Smithsonian Insider.

Every day, astronomers at the Harvard-Smithsonian Center for Astrophysics depend on computers to help them solve the mysteries of the universe, just as they did […]

The post Underpaid women “computers” mapped the universe in the 19th century appeared first on Smithsonian Insider.

Marine mammologist Matthew Leslie aims his crossbow from the bow of a moving boat at the dolphins riding the breaking waves below. A dolphin will […]

The post Some dolphins cross the Pacific more easily than others. Why that matters for protecting them appeared first on Smithsonian Insider.

When a natural disaster strikes, it devastates lives and homes, and can even destroy a culture’s identity and history. After a disaster, humanitarian response is […]

The post Protecting Puerto Rico’s heritage from another disaster appeared first on Smithsonian Insider.

Very early on, cockroach moms found out maternal care gave their offspring a better chance at survival. The cockroach parenting method—which includes feeding, guarding and […]

The post Helicopter cockroach moms have protected their young for millions of years appeared first on Smithsonian Insider.

In the early 20th century, Canada geese were considered endangered in the U.S. So in the 1950s and 1960s, birds from the Midwest were released […]

The post Study of bacteria inside guts of wild Canada geese shows greater danger than earlier studies exposed appeared first on Smithsonian Insider.

Little to nothing is known about how and where a small European songbird called the bluethroat spends much of the year. Now, Smithsonian scientists have […]

The post Scientists track a mysterious songbird using tiny backpack locators appeared first on Smithsonian Insider.

The outer membrane of Gram-negative bacteria is highly impermeable to hydrophilic molecules of larger than 600 Da, protecting these bacteria from toxins present in the environment. In order to transport nutrients across this impermeable membrane, Gram-negative bacteria utilize a diverse family of outer-membrane proteins called TonB-dependent transporters. The majority of the members of this family transport iron-containing substrates. However, it is becoming increasingly clear that TonB-dependent transporters target chemically diverse substrates. In this work, the structure and phylogenetic distribution of the TonB-dependent transporter YncD are investigated. It is shown that while YncD is present in some enteropathogens, including Escherichia coli and Salmonella spp., it is also widespread in Gammaproteobacteria and Betaproteobacteria of environmental origin. The structure of YncD was determined, showing that despite a distant evolutionary relationship, it shares structural features with the ferric citrate transporter FecA, including a compact positively charged substrate-binding site. Despite these shared features, it is shown that YncD does not contribute to the growth of E. coli in pure culture under iron-limiting conditions or with ferric citrate as an iron source. Previous studies of transcriptional regulation in E. coli show that YncD is not induced under iron-limiting conditions and is unresponsive to the ferric uptake regulator (Fur). These observations, combined with the data presented here, suggest that YncD is not responsible for the transport of an iron-containing substrate.

The biological processes related to protein homeostasis in Mycobacterium tuberculosis, the etiologic agent of tuberculosis, have recently been established as critical pathways for therapeutic intervention. Proteins of particular interest are ClpC1 and the ClpC1–ClpP1–ClpP2 proteasome complex. The structure of the potent antituberculosis macrocyclic depsipeptide ecumicin complexed with the N-terminal domain of ClpC1 (ClpC1-NTD) is presented here. Crystals of the ClpC1-NTD–ecumicin complex were monoclinic (unit-cell parameters a = 80.0, b = 130.0, c = 112.0 Å, β = 90.07°; space group P21; 12 complexes per asymmetric unit) and diffracted to 2.5 Å resolution. The structure was solved by molecular replacement using the self-rotation function to resolve space-group ambiguities. The new structure of the ecumicin complex showed a unique 1:2 (target:ligand) stoichiometry exploiting the intramolecular dyad in the α-helical fold of the target N-terminal domain. The structure of the ecumicin complex unveiled extensive interactions in the uniquely extended N-terminus, a critical binding site for the known cyclopeptide complexes. This structure, in comparison with the previously reported rufomycin I complex, revealed unique features that could be relevant for understanding the mechanism of action of these potential antituberculosis drug leads. Comparison of the ecumicin complex and the ClpC1-NTD-L92S/L96P double-mutant structure with the available structures of rufomycin I and cyclomarin A complexes revealed a range of conformational changes available to this small N-terminal helical domain and the minor helical alterations involved in the antibiotic-resistance mechanism. The different modes of binding and structural alterations could be related to distinct modes of action.

Death-associated protein kinase 1 (DAPK1) is a serine/threonine protein kinase that regulates apoptosis and autophagy. DAPK1 is considered to be a therapeutic target for amyloid-β deposition, endometrial adenocarcinomas and acute ischemic stroke. Here, the potent inhibitory activity of the natural anthraquinone purpurin against DAPK1 phosphorylation is shown. Thermodynamic analysis revealed that while the binding affinity of purpurin is similar to that of CPR005231, which is a DAPK1 inhibitor with an imidazopyridazine moiety, the binding of purpurin was more enthalpically favorable. In addition, the inhibition potencies were correlated with the enthalpic changes but not with the binding affinities. Crystallographic analysis of the DAPK1–purpurin complex revealed that the formation of a hydrogen-bond network is likely to contribute to the favorable enthalpic changes and that stabilization of the glycine-rich loop may cause less favorable entropic changes. The present findings indicate that purpurin may be a good lead compound for the discovery of inhibitors of DAPK1, and the observation of enthalpic changes could provide important clues for drug development.

Mycoplasma hyopneumoniae is a prokaryotic pathogen that colonizes the respiratory ciliated epithelial cells in swine. Infected animals suffer respiratory lesions, causing major economic losses in the porcine industry. Characterization of the immunodominant membrane-associated proteins from M. hyopneumoniae may be instrumental in the development of new therapeutic approaches. Here, the crystal structure of P46, one of the main surface-antigen proteins, from M. hyopneumoniae is presented and shows N- and C-terminal α/β domains connected by a hinge. The structures solved in this work include a ligand-free open form of P46 (3.1 Å resolution) and two ligand-bound structures of P46 with maltose (2.5 Å resolution) and xylose (3.5 Å resolution) in open and closed conformations, respectively. The ligand-binding site is buried in the cleft between the domains at the hinge region. The two domains of P46 can rotate with respect to each other, giving open or closed alternative conformations. In agreement with this structural information, sequence analyses show similarities to substrate-binding members of the ABC transporter superfamily, with P46 facing the extracellular side as a functional subunit. In the structure with xylose, P46 was also bound to a high-affinity (Kd = 29 nM) Fab fragment from a monoclonal antibody, allowing the characterization of a structural epitope in P46 that exclusively involves residues from the C-terminal domain. The Fab structure in the complex with P46 shows only small conformational rearrangements in the six complementarity-determining regions (CDRs) with respect to the unbound Fab (the structure of which is also determined in this work at 1.95 Å resolution). The structural information that is now available should contribute to a better understanding of sugar nutrient intake by M. hyopneumoniae. This information will also allow the design of protocols and strategies for the generation of new vaccines against this important swine pathogen.

Tidal Freshwater Wetlands focuses on wetlands found in North America and Europe near the mouths of rivers that flow into estuaries like the Chesapeake Bay.

The post New book reveals tidal freshwater wetlands are on frontlines of global change appeared first on Smithsonian Insider.

Benjamin Ziman, Peter Karabinis, Paul Barghouth, and Nestor J. Oviedo

Nutrient availability upon feeding leads to an increase in body size in the planarian Schmidtea mediterranea. However, it remains unclear how food consumption integrates with cell division at the organismal level. Here we show that Sirtuins is evolutionarily conserved in planarians and specifically demonstrate that Sirtuin-1 (Smed-Sirt-1) regulates organismal growth by impairing both feeding behavior and intestinal morphology. Disruption of Smed-Sirt-1 with either RNAi or pharmacological treatment leads to reduced animal growth. Conversely, enhancement of Smed-Sirt-1 with resveratrol accelerates growth. Differences in growth rates were associated with changes in the amount of time to locate food and overall consumption. Furthermore, Smed-Sirt-1(RNAi) animals displayed reduced cell death and increased stem cell proliferation accompanied by impaired expression of intestinal lineage progenitors and reduced branching of the gut. Altogether, our findings indicate Sirtuin-1 is a crucial metabolic hub capable of controlling animal behavior, tissue renewal and morphogenesis of the adult intestine.

Su Ming Sun, Amandine Batte, Mireille Tittel-Elmer, Sophie van der Horst, Tibor van Welsem, Gordon Bean, Trey Ideker, Fred van Leeuwen, and Haico van Attikum

Eukaryotic chromosomes are replicated in interphase and the two newly duplicated sister chromatids are held together by the cohesin complex and several cohesin auxiliary factors. Sister chromatid cohesion is essential for accurate chromosome segregation during mitosis, yet has also been implicated in other processes, including DNA damage repair, transcription and DNA replication. To assess how cohesin and associated factors functionally interconnect and coordinate with other cellular processes, we systematically mapped genetic interactions of 17 cohesin genes centered on quantitative growth measurements of >52,000 gene pairs in budding yeast. Integration of synthetic genetic interactions unveiled a cohesin functional map that constitutes 373 genetic interactions, revealing novel functional connections with post-replication repair, microtubule organization and protein folding. Accordingly, we show that the microtubule-associated protein Irc15 and the prefoldin complex members Gim3, Gim4 and Yke2 are new factors involved in sister chromatid cohesion. Our genetic interaction map thus provides a unique resource for further identification and functional interrogation of cohesin proteins. Since mutations in cohesin proteins have been associated with cohesinopathies and cancer, it may also identify cohesin interactions relevant in disease etiology.

Julian Chollet, Alexander Dünkler, Anne Bäuerle, Laura Vivero-Pol, Medhanie A. Mulaw, Thomas Gronemeyer, and Nils Johnsson

Yeast cells select the position of their new bud at the beginning of each cell cycle. The recruitment of the septins to this prospective bud site is one of the critical events in a complex assembly pathway that culminates in the outgrowth of a new daughter cell. Hereby, the septin-rods follow the high concentration of Cdc42_GTP that is generated by the focused localization of its GEF Cdc24. We show that shortly before budding Cdc24 not only activates Cdc42 but also transiently interacts with Cdc11, the septin subunit that caps both ends of the septin rods. Mutations in Cdc24 reducing the affinity to Cdc11 impair septin recruitment and decrease the stability of the polarity patch. The interaction between septins and Cdc24 thus reinforces bud assembly at sites where septin structures are formed. Once the septins polymerize into the ring, Cdc24 is found at the cortex of the bud and directs its further outgrowth from this position.

Kelly L. Dunlevy, Valentina Medvedeva, Jade E. Wilson, Mohammed Hoque, Trinity Pellegrin, Adam Maynard, Madison M. Kremp, Jason S. Wasserman, Andrey Poleshko, and Richard A. Katz

A large fraction of epigenetically silent heterochromatin is anchored to the nuclear periphery via "tethering proteins" that function to bridge heterochromatin and the nuclear membrane or nuclear lamina. We identified previously a human tethering protein, PRR14, that binds heterochromatin through an N-terminal domain, but the mechanism and regulation of nuclear lamina association remained to be investigated. Here we identify an evolutionarily conserved PRR14 nuclear lamina binding domain (LBD) that is both necessary and sufficient for positioning of PRR14 at the nuclear lamina. We also show that PRR14 associates dynamically with the nuclear lamina, and provide evidence that such dynamics are regulated through phosphorylation-dephosphorylation of the LBD. Furthermore, we identified a PP2A phosphatase recognition motif within the evolutionarily conserved PRR14 C-terminal Tantalus domain. Disruption of this motif affected PRR14 localization to the nuclear lamina. The overall findings demonstrate a heterochromatin anchoring mechanism whereby the PRR14 tether simultaneously binds heterochromatin and the nuclear lamina through two separable, modular domains. The findings also describe an optimal PRR14 LBD fragment that could be used for efficient targeting of fusion proteins to the nuclear lamina.

To understand the long-term effects of a prolonged tropical storm in the Panama Canal watershed, Robert Stallard, staff scientist at the Smithsonian Tropical Research Institute and research hydrologist at the U.S. Geological Survey, and Armando Ubeda, the LightHawk Mesoamerica program manager, organized four flights over the watershed to create a digital map of landslide scars.

The post Smithsonian hydrologist discovers that rainfall has dried up Panama’s drinking water appeared first on Smithsonian Insider.

The pendant took Grand Prize in the National Saul Bell Design Competition in 2008 and features a beautiful 3.76-ct pink tourmaline from Nigeria.

The post Pink tourmaline “Nautilus” pendant enters National Gem Collection appeared first on Smithsonian Insider.

During a press conference Friday, July 22 at the Smithsonian's National Air and Space Museum, NASA announced that Gale Crater will be the landing site for the Mars Science Laboratory. Scheduled to launch in late 2011 and arrive at Mars in August 2012, the Mars Science Laboratory is a rover that will assess the planet’s “habitability”—if it ever was, or is today, an environment able to support microbial life.

The post Gale Crater to be landing site for NASA’s Mars Science Laboratory appeared first on Smithsonian Insider.

The National Museum of Natural History’s gem collection has a new addition: the Cindy Chao Black Label Masterpiece Royal Butterfly Brooch. Created by Chao in […]

The post Butterfly Brooch Enters National Gem Collection appeared first on Smithsonian Insider.

Recent airborne geophysical surveys near Decorah, Iowa are providing an unprecedented look at a 470-million-year-old meteorite crater concealed beneath bedrock and sediments. The aerial surveys, […]

The post Iowa meteorite crater confirmed appeared first on Smithsonian Insider.

The post The Forgotten Dinosaur Hunter appeared first on Smithsonian Insider.

Forget what you thought you knew about geology. Some minerals can roll up like flaky Belgian piroulines. For the last several decades, mining operations in […]

The post Rolled-Up Mystery Mineral may cause Craving for Piroulines appeared first on Smithsonian Insider.

Oysters are keystone organisms in estuaries around the world, influencing water quality, constructing habitat and providing food for humans and wildlife. Yet their populations in […]

The post Ancient Native-American methods may be key to sustainable oyster harvests appeared first on Smithsonian Insider.

At 7:05 pm (EDT), Thursday, Sept. 8, NASA plans to launch a spacecraft to a near-Earth asteroid named Bennu. Among that spacecraft’s five instruments is […]

The post Asteroid Mission carries Student X-ray Experiment appeared first on Smithsonian Insider.

Have an upset stomach? Pop a chalky, chewable antacid. Maybe you’ve got a painful cut or burn. No problem; reach for a healing ointment or […]

The post Glittering, mesmerizing, lifesaving: Hospital exhibit showcases minerals used in medicine appeared first on Smithsonian Insider.

The Jamaican golden swallow was last seen in 1982. From 1994 to 2012, Smithsonian ornithologist Gary Graves combed the island of Jamaica to document several […]

The post After a nearly 20-year search, this Jamaican bird is probably extinct appeared first on Smithsonian Insider.

Structural investigations of amorphous and nanocrystalline phases forming in solution are historically challenging. Few methods are capable of in situ atomic structural analysis and rigorous control of the system. A mixed-flow reactor (MFR) is used for total X-ray scattering experiments to examine the short- and long-range structure of phases in situ with pair distribution function (PDF) analysis. The adaptable experimental setup enables data collection for a range of different system chemistries, initial supersaturations and residence times. The age of the sample during analysis is controlled by adjusting the flow rate. Faster rates allow for younger samples to be examined, but if flow is too fast not enough data are acquired to average out excess signal noise. Slower flow rates form older samples, but at very slow speeds particles settle and block flow, clogging the system. Proper background collection and subtraction is critical for data optimization. Overall, this MFR method is an ideal scheme for analyzing the in situ structures of phases that form during crystal growth in solution. As a proof of concept, high-resolution total X-ray scattering data of amorphous and crystalline calcium phosphates and amorphous calcium carbonate were collected for PDF analysis.

Under the anomalous transmission condition in the Bragg mode, X-ray interference fringes were observed between two beams with different hyperbolic trajectories in a very weakly bent plane-parallel perfect crystal with negative strain gradient. The origin of the fringes was analysed based on the dynamical theory of diffraction for a distorted crystal. In the reflected beam from the entrance surface, the interference fringes were observed between once- and twice-reflected beams from the back surface. In the transmitted beam from the back surface, the interference fringes were observed between the direct beam and once-reflected beam from the entrance surface. In the emitted beam from the lateral surface, the interference fringes were observed between the beams after different numbers of reflections in the crystal. The multiply reflected beams were formed by a combined result of long propagation length along the beam direction with large divergence of the refracted beams when the strain gradient was negative. The period of these interference fringes was sensitive to very weak strain, of the order of 10−7.

Relativistic electron diffraction depends on linear and quadratic terms in the electric potential, the latter being neglected in the frequently used relativistically corrected Schrödinger equation. The quadratic electric potential term modifies atomic scattering amplitudes in particular for large-angle scattering and backscattering. The respective correction increases with increasing scattering angle, increasing atomic number and increasing kinetic energy. Conventional tabulations for electron scattering and its large-angle extrapolations can be amended in closed form by a universal correction based on the screened Coulomb potential squared.

This work studies the elastic scattering behavior of electron vortices when propagating through amorphous samples. A formulation of the multislice approach in cylindrical coordinates is used to theoretically investigate the redistribution of intensity between different angular momentum components due to scattering. To corroborate and elaborate on our theoretical results, extensive numerical simulations are performed on three model systems (Si3N4, Fe0.8B0.2, Pt) for a wide variety of experimental parameters to quantify the purity of the vortices, the net angular momentum transfer, and the variability of the results with respect to the random relative position between the electron beam and the scattering atoms. These results will help scientists to further improve the creation of electron vortices and enhance applications involving them.

A novel approach for finding and evaluating structural models of small metallic nanoparticles is presented. Rather than fitting a single model with many degrees of freedom, libraries of clusters from multiple structural motifs are built algorithmically and individually refined against experimental pair distribution functions. Each cluster fit is highly constrained. The approach, called cluster-mining, returns all candidate structure models that are consistent with the data as measured by a goodness of fit. It is highly automated, easy to use, and yields models that are more physically realistic and result in better agreement to the data than models based on cubic close-packed crystallographic cores, often reported in the literature for metallic nanoparticles.

A mysterious nocturnal animal was leaving its tracks on the delicate mirrors of the telescopes at the Smithsonian's Whipple Observatory in Arizona. With a little ingenuity and a live trap, the mystery was solved. The visitor proved to be a ringtail cat, a member of the raccoon family.

The post Astronomers solve mystery of dusty foot trails crossing telescope mirrors appeared first on Smithsonian Insider.

George Smith, a marine biologist at the Smithsonian Environmental Research Center, explains his work of finding ways to prevent invasive species from being released in Baltimore Harbor in the ballast water of large ships.

The post Preventing ballast-water invasions of alien species appeared first on Smithsonian Insider.

Leafcutter Ants—an amazing species that has been employing agriculture and antibiotics for some 50 million years.

The post Leafcutter ants—first in agiculture and antibiotics appeared first on Smithsonian Insider.

The post Meet Our Scientist: National Zoo veterinarian Katharine Hope appeared first on Smithsonian Insider.