By using small-angle neutron scattering (SANS) reinforced by scanning electron microscopy, the fine structure of catalysts for polymer electrolyte fuel cells has been investigated. The experimental data resulting from contrast variation with mixed light and heavy water (H2O/D2O) are well described by a core–shell model with fluctuations in concentration between water and Nafion.

The effects of relative humidity on a tetragonal crystal form of hen egg white lysozyme are studied via in situ laboratory X-ray powder diffraction.

Book review

The design and assembly of two 3D-printed holders for high-throughput in meso in situ fixed-target crystallographic data collection are described.

A new approach to variable-temperature measurements is presented, where the sample temperature changes continuously as a function of position.

Exact and approximate formulas for equatorial aberration of a continuous-scan Si strip detector are compared.

An algorithm, based on the matching of q-vectors pairs, is combined with three-dimensional pattern matching using a nearest-neighbors approach to index Laue and monochromatic serial crystallography data recorded on small unit cell samples.

A software package for Grazing Incident Wide Angle X-ray Scattering (GIWAXS) geared toward weakly ordered materials, including: scattering intensity normalization/uncertainty, scattering pattern indexing, and refractive shift correction.

Most articles dealing with R2TSi3 compounds are only interested in one specific composite or in a series of composites with varying T elements while keeping R fixed (or vice versa). The present work gives an overview of the complete range of 2:1:3 silicides, similar those of Hoffmann & Pöttgen (2001) and Pan et al. (2013). In contrast to the work of Hoffmann & Pöttgen (2001), reasons for formation of the different symmetries and superstructures are discussed. Here, crystallographic properties are in[the] focus, whereas physical and magnetic properties are omitted because those are given by Pan et al. (2013). READS LIKE AN ABSTRACT, please re-write and remove references if possible. Should be two sentences max.

A putative open reading frame encoding GTP cyclohydrolase I from Listeria monocytogenes was expressed in a recombinant Escherichia coli strain. The recombinant protein was purified and was confirmed to convert GTP to dihydroneopterin triphosphate (Km = 53 µM; vmax = 180 nmol mg−1 min−1). The protein was crystallized from 1.3 M sodium citrate pH 7.3 and the crystal structure was solved at a resolution of 2.4 Å (Rfree = 0.226) by molecular replacement using human GTP cyclohydrolase I as a template. The protein is a D5-symmetric decamer with ten topologically equivalent active sites. Screening a small library of about 9000 compounds afforded several inhibitors with IC50 values in the low-micromolar range. Several inhibitors had significant selectivity with regard to human GTP cyclohydrolase I. Hence, GTP cyclohydrolase I may be a potential target for novel drugs directed at microbial infections, including listeriosis, a rare disease with high mortality.

This study presents the crystal structure of a thiol variant of the human mitochondrial branched-chain aminotransferase protein. Human branched-chain aminotransferase (hBCAT) catalyzes the transamination of the branched-chain amino acids leucine, valine and isoleucine and α-ketoglutarate to their respective α-keto acids and glutamate. hBCAT activity is regulated by a CXXC center located approximately 10 Å from the active site. This redox-active center facilitates recycling between the reduced and oxidized states, representing hBCAT in its active and inactive forms, respectively. Site-directed mutagenesis of the redox sensor (Cys315) results in a significant loss of activity, with no loss of activity reported on the mutation of the resolving cysteine (Cys318), which allows the reversible formation of a disulfide bond between Cys315 and Cys318. The crystal structure of the oxidized form of the C318A variant was used to better understand the contributions of the individual cysteines and their oxidation states. The structure reveals the modified CXXC center in a conformation similar to that in the oxidized wild type, supporting the notion that its regulatory mechanism depends on switching the Cys315 side chain between active and inactive conformations. Moreover, the structure reveals conformational differences in the N-terminal and inter-domain region that may correlate with the inactivated state of the CXXC center.

Successes in animal health care presents many new challenges for veterinarians. Longer life spans in captivity mean zoo animals are now experiencing age-related health problems that their zoo predecessors never lived long enough to develop—like diabetes in cheetahs, arthritis in big cats and dental issues for coatis.

The post Golden years at the Zoo: Veterinarians work to help animals live longer, stay healthy appeared first on Smithsonian Insider.

If intelligent and more advanced civilizations exist on other planets then its a good bet that some of these civilizations turned to asteroid mining long ago. If so, the hallmarks of their mining activities, such as unusual dirty halos of cast-off dust and debris around large asteroids, might be detectable from earth.

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A new bacterial genome sequence could help researchers solve a mystery as to how microorganisms produce a highly toxic form of mercury.

The post New bacteria genome may help solve mystery of how methylmercury is made appeared first on Smithsonian Insider.

This image of lawyer Clarence S. Darrow (center) talking with group of men in Dayton, Tenn., in July 1925 is one of 10 photographs from […]

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Suzan Murray, chief veterinary medical officer at the Smithsonian’s National Zoological Park, recently returned from Hanoi, where she led a team of scientists training pathologists from Laos, Cambodia and Vietnam to better sample, recognize and detect wildlife diseases in hopes of preventing emerging pandemic disease.

The post Q&A: National Zoo veterinarian Suzan Murray is working to halt pandemic disease in hotspots around the world appeared first on Smithsonian Insider.

Even dying stars could host planets with life – and if such life exists, we might be able to detect it within the next decade. […]

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The impact of industrial fishing on coastal ecosystems has been studied for many years. But how it affects food webs in the open ocean―a vast […]

The post Scientists find impact of open-ocean industrial fishing within centuries of bird bones appeared first on Smithsonian Insider.

A new study of microorganisms living on the skin and in the intestines of North America vultures (black and turkey vultures) has turned up a […]

The post Vultures remarkably tolerant to deadly bacteria, study reveals appeared first on Smithsonian Insider.

Point your smartphone at the skeleton of a vampire bat mounted in a museum case, wait a minute and you will see it wiggle, jump […]

The post New App adds Virtual Flesh to Victorian-era Bone exhibit appeared first on Smithsonian Insider.

Through sheer coincidence, two Smithsonian researchers at the National Zoological Park have discovered that 18 percent of the white-tailed deer population in the Eastern United […]

The post Smithsonian study reveals white-tailed deer in eastern U.S. are infected with a malaria parasite appeared first on Smithsonian Insider.

Crustaceans that thrive in the vastness of the open ocean have no place to hide from their predators. Consequently, many creatures that live at depths […]

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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.

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.

Osiris Martinez-Guzman, Mathilda M. Willoughby, Arushi Saini, Jonathan V. Dietz, Iryna Bohovych, Amy E. Medlock, Oleh Khalimonchuk, and Amit R. Reddi

Heme is a cofactor and signaling molecule that is essential for much of aerobic life. All heme-dependent processes in eukaryotes require that heme is trafficked from its site of synthesis in the mitochondria to hemoproteins located throughout the cell. However, the mechanisms governing the mobilization of heme out of the mitochondria, and the spatio-temporal dynamics of these processes, are poorly understood. Herein, using genetically encoded fluorescent heme sensors, we developed a live cell assay to monitor heme distribution dynamics between the mitochondrial inner-membrane, where heme is synthesized, and the mitochondrial matrix, cytosol, and nucleus. Surprisingly, heme trafficking to the nucleus is ~25% faster than to the cytosol or mitochondrial matrix, which are nearly identical, potentially supporting a role for heme as a mitochondrial-nuclear retrograde signal. Moreover, we discovered that the heme synthetic enzyme, 5-aminolevulinic acid synthase (ALAS), and GTPases in control of the mitochondrial dynamics machinery, Mgm1 and Dnm1, and ER contact sites, Gem1, regulate the flow of heme between the mitochondria and nucleus. Overall, our results indicate that there are parallel pathways for the distribution of bioavailable heme.

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.

Javad Fahanik-babaei, Bahareh Rezaee, Maryam Nazari, Nihad Torabi, Reza Saghiri, Remy Sauve, and Afsaneh Eliassi

We have determined the electropharmacological properties of a new potassium channel from brain mitochondrial membrane by planar lipid bilayer method. Our results showed the presence of a channel with a conductance of 150 pS at potentials between 0 and –60 mV in 200 cis/50 trans mM KCl solutions.

The channel was voltage-independent, with an open probability value ~0.6 at different voltages. ATP did not affect current amplitude and Po at positive and negative voltages. Notably, adding iberiotoxin, charybdotoxin, lidocaine, and margatoxin had no effect on the channel behavior. Similarly, no changes were observed by decreasing the cis-pH to 6. Interestingly, the channel was inhibited by adding sodium in a dose dependent manner. Our results also indicated a significant increase in mitochondrial complex IV activity and membrane potential and decrease in complex I activity and mitochondrial ROS production in the presence of sodium ions.

We propose that inhibition of mitochondrial K⁺ transport by Na ions on K⁺ channel opening may be important for cell protection and ATP synthesis.

As average annual temperatures increase, mosquitoes have also been on the move—up the mountains of the Hawaiian islands. Once a refuge for native birds susceptible […]

The post Scientists race to find genetic clues as malaria decimates rare Hawaiian honeycreepers 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.

Appendices B4 and B5 of Cayron [Acta Cryst. (2019), A75, 411–437] contain equations involving the point group and the metric tensor in which the equality symbol should be substituted by the inclusion symbol.

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.

Forensic anthropologists from the Smithsonian's National Museum of Natural History discover African remains at a Colonial burial site in Maryland. Follow them as they study the remains, reconstruct the face and body, and share what they learn about the African experience in the Chesapeake in the 1600s.

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Join National Zoo Conservation Biologist Brian Gratwicke in his work to save Panama's amphibians from extinction. You can also catch up on his dispatches from the field on the Panamanian Amphibian Rescue and Conservation Project's blog: http://amphibianrescue.org/

The post Meet our Scientist: Brian Gratwicke, Amphibian Avenger appeared first on Smithsonian Insider.

National Zoo Veterinarian Katharine Hope treats about 2,000 animals from 400 different species. She and her colleagues care for a variety of animals, from small baby flamingos to adult Asian elephants, so there's no such thing as an average day.

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Digging up early human and animal remains from the field in Africa, performing examination and publishing research about her findings, then enticing and educating the public about the implications are all in a week's work for Briana Pobiner.

The post Meet Our Scientist–Briana Pobiner, human origins researcher at the National Museum of Natural History appeared first on Smithsonian Insider.

Tom Crouch, Senior curator in the National Air and Space Museum's Aeronautics Division, discusses Thaddeus Lowe and the birth of American aerial reconnaissance during the Civil War. This presentation was recorded on May 11, 2011 on the National Mall.

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Meet the Smithsonian's Matthew Carrano, curator of Dinosauria at the Smithsonian's National Museum of Natural History in Washington, D.C. Matthew studies all things dinosaur, but focuses on the evolutionary history of predatory (meat eating) dinosaurs.

The post Meet Our Scientist: Matthew Carrano, curator of dinosauria at the Smithsonian’s National Museum of Natural History appeared first on Smithsonian Insider.

Clip from silent edited film "Bryson Jones Travelogue: Lure of the West" (ca. 1927) shows Mount Rushmore National Memorial under construction, including blasting off cliff face, scaffolding, men working, and the completed monument.

The post Construction of Mount Rushmore National Memorial from the Smithsonian’s Human Studies Film Archives appeared first on Smithsonian Insider.

Smithsonian planetary geologists Sharon Purdy and Maria Banks explain how you can take your very own photo of Mars.

The post Scientists Maria Banks and Sharon Purdy explain how to take your own photo of Mars. appeared first on Smithsonian Insider.

Millions, if not billions, of specimens reside in the world’s natural history collections, but most of these have not been carefully studied, or even looked […]

The post Using digitized Botany specimens, AI excels in simple curatorial tasks appeared first on Smithsonian Insider.

In the structure of the title salt, second-order Jahn–Teller distortion of the coordination octa­hedra around V ions is reflected by coexistence of short V—O bonds and trans-positioned long V—F bonds, with four equatorial V—F distances being inter­mediate in magnitude. Hydrogen bonding of the anions is restricted to F-atom acceptors only, with particularly strong N–H⋯F inter­actions [N⋯F = 2.5072 (15) Å] established by axial and cis-positioned equatorial F atoms.

The development of antiviral strategies requires a clear understanding of the principles that control the protein arrangements in viral shells. Considered here are those capsids that violate the paradigmatic Caspar and Klug (CK) model, and it is shown that the important structural features of such anomalous shells from the Picobirnaviridae, Flaviviridae and Leviviridae families can be revealed by models in the form of spherical icosahedral packings of equivalent rhombic structural units (SUs). These SUs are composed of protein dimers forming the investigated capsids which, as shown here, are based on the rhombic triacontahedron (RT) geometry. How to modify the original CK approach in order to make it compatible with the considered rhombic tessellations of a sphere is also discussed. Analogies between capsids self-assembled from dimers and trimers are demonstrated. This analysis reveals the principles controlling the localization of receptor proteins (which recognize the host cell) on the capsid surface.

In the structure of the title salt, (C7H12N6)[VOF5], second-order Jahn–Teller distortion of the coordination octahedra around V ions is reflected by coexistence of short V—O bonds [1.5767 (12) Å] and trans-positioned long V—F bonds [2.0981 (9) Å], with four equatorial V—F distances being intermediate in magnitude [1.7977 (9)–1.8913 (9) Å]. Hydrogen bonding of the anions is restricted to F-atom acceptors only, with particularly strong N–H...F interactions [N...F = 2.5072 (15) Å] established by axial and cis-positioned equatorial F atoms. Hirshfeld surface analysis indicates that the most important interactions are overwhelmingly H...F/F...H, accounting for 74.4 and 36.8% of the contacts for the individual anions and cations, respectively. Weak CH...F and CH...N bonds are essential for generation of three-dimensional structure.

An efficient synthesis of 1-aryl­isochromeno[3,4-d][1,2,3]triazol-5(1H)-ones, involving the diazo­tization of 3-amino-4-aryl­amino-1H-isochromen-1-ones in weakly acidic solution, has been developed and the spectroscopic characterization and crystal structures of four examples are reported. The mol­ecules of 1-phenyl­isochromeno[3,4-d][1,2,3]triazol-5(1H)-one, C15H9N3O2, (I), are linked into sheets by a combination of C—H⋯N and C—H⋯O hydrogen bonds, while the structures of 1-(2-methyl­phen­yl)isochromeno[3,4-d][1,2,3]triazol-5(1H)-one, C16H11N3O2, (II), and 1-(3-chloro­phen­yl)isochromeno[3,4-d][1,2,3]triazol-5(1H)-one, C15H8ClN3O2, (III), each contain just one hydrogen bond which links the mol­ecules into simple chains, which are further linked into sheets by π-stacking inter­actions in (II) but not in (III). In the structure of 1-(4-chloro­phen­yl)isochromeno[3,4-d][1,2,3]triazol-5(1H)-one, (IV), isomeric with (III), a combination of C—H⋯O and C—H⋯π(arene) hydrogen bonds links the mol­ecules into sheets. When com­pound (II) was exposed to a strong acid in methanol, qu­anti­tative conversion occurred to give the ring-opened transesterification product methyl 2-[4-hy­droxy-1-(2-methyl­phen­yl)-1H-1,2,3-triazol-5-yl]benzoate, C17H15N3O3, (V), where the mol­ecules are linked by paired O—H⋯O hydrogen bonds to form centrosymmetric dimers.

Christopher R. Mahone
Apr 8, 2020; 133:jcs237057-jcs237057
CELL SCIENCE AT A GLANCE

Full Text:

The molecular mechanism used by many bacteria to kill neighboring cells has redundancy built into its genetic makeup, which could allow for the mechanism to be expressed in different environments, say researchers at Penn State and the University of Wisconsin-Madison. Their new study provides insights into the molecular mechanisms of competition among bacteria. "Many organisms, including humans, acquire bacteria from their environment," said Tim Miyashiro, a biochemist and molecular biologist at Penn State and the leader of the research team. "These bacteria can contribute to functions within the host organism, like how our gut bacteria help us digest food. We're interested in the interactions among bacteria cells, and between bacteria and their hosts, to better understand these mutually beneficial symbiotic relationships." Cells of the bioluminescent bacteria Vibrio fisheri take up residence in the light organ of newly hatched bobtail squid. At night, the bacteria produce a blue glow that researchers believe obscures a squid's silhouette and helps protect it from predators. The light organ has pockets, or crypts, in the squid's skin that provide nutrients and a safe environment for the bacteria. "When the squid hatches, it doesn't yet have any bacteria in its light organ," said Miyashiro. "But bacteria in the environment quickly colonize the squid's light organ." Some of these different bacteria strains can coexist, but others can't. "Microbial symbioses are essentially universal in animals, and are crucial to the health and development of both partners," says Irwin Forseth, a program director in the National Science Foundation's Division of Integrative Organismal Systems, which funded the research. "The results from this study highlight the role small genetic changes can play in microbe interactions. Increased understanding will allow us to better predict organisms' performance in changing environments."

Image credit: Andrew Cecere