A combined biophysical approach was applied to map gas-docking sites within murine neuroglobin (Ngb), revealing snapshots of events that might govern activity and dynamics in this unique hexacoordinate globin, which is most likely to be involved in gas-sensing in the central nervous system and for which a precise mechanism of action remains to be elucidated. The application of UV–visible microspectroscopy in crystallo, solution X-ray absorption near-edge spectroscopy and X-ray diffraction experiments at 15–40 K provided the structural characterization of an Ngb photolytic intermediate by cryo-trapping and allowed direct observation of the relocation of carbon monoxide within the distal heme pocket after photodissociation. Moreover, X-ray diffraction at 100 K under a high pressure of dioxygen, a physiological ligand of Ngb, unravelled the existence of a storage site for O2 in Ngb which coincides with Xe-III, a previously described docking site for xenon or krypton. Notably, no other secondary sites were observed under our experimental conditions.

Human septins 3, 9 and 12 are the only members of a specific subgroup of septins that display several unusual features, including the absence of a C-terminal coiled coil. This particular subgroup (the SEPT3 septins) are present in rod-like octameric protofilaments but are lacking in similar hexameric assemblies, which only contain representatives of the three remaining subgroups. Both hexamers and octamers can self-assemble into mixed filaments by end-to-end association, implying that the SEPT3 septins may facilitate polymerization but not necessarily function. These filaments frequently associate into higher order complexes which associate with biological membranes, triggering a wide range of cellular events. In the present work, a complete compendium of crystal structures for the GTP-binding domains of all of the SEPT3 subgroup members when bound to either GDP or to a GTP analogue is provided. The structures reveal a unique degree of plasticity at one of the filamentous interfaces (dubbed NC). Specifically, structures of the GDP and GTPγS complexes of SEPT9 reveal a squeezing mechanism at the NC interface which would expel a polybasic region from its binding site and render it free to interact with negatively charged membranes. On the other hand, a polyacidic region associated with helix α5', the orientation of which is particular to this subgroup, provides a safe haven for the polybasic region when retracted within the interface. Together, these results suggest a mechanism which couples GTP binding and hydrolysis to membrane association and implies a unique role for the SEPT3 subgroup in this process. These observations can be accounted for by constellations of specific amino-acid residues that are found only in this subgroup and by the absence of the C-terminal coiled coil. Such conclusions can only be reached owing to the completeness of the structural studies presented here.

Solute carriers are a large class of transporters that play key roles in normal and disease physiology. Among the solute carriers, heteromeric amino-acid transporters (HATs) are unique in their quaternary structure. LAT1–CD98hc, a HAT, transports essential amino acids and drugs across the blood–brain barrier and into cancer cells. It is therefore an important target both biologically and therapeutically. During the course of this work, cryo-EM structures of LAT1–CD98hc in the inward-facing conformation and in either the substrate-bound or apo states were reported to 3.3–3.5 Å resolution [Yan et al. (2019), Nature (London), 568, 127–130]. Here, these structures are analyzed together with our lower resolution cryo-EM structure, and multibody 3D auto-refinement against single-particle cryo-EM data was used to characterize the dynamics of the interaction of CD98hc and LAT1. It is shown that the CD98hc ectodomain and the LAT1 extracellular surface share no substantial interface. This allows the CD98hc ectodomain to have a high degree of movement within the extracellular space. The functional implications of these aspects are discussed together with the structure determination.

p-Hydroxymandelate oxidase (Hmo) is a flavin mononucleotide (FMN)-dependent enzyme that oxidizes mandelate to benzoylformate. How the FMN-dependent oxidation is executed by Hmo remains unclear at the molecular level. A continuum of snapshots from crystal structures of Hmo and its mutants in complex with physiological/nonphysiological substrates, products and inhibitors provides a rationale for its substrate enantioselectivity/promiscuity, its active-site geometry/reactivity and its direct hydride-transfer mechanism. A single mutant, Y128F, that extends the two-electron oxidation reaction to a four-electron oxidative decarboxylation reaction was unexpectedly observed. Biochemical and structural approaches, including biochemistry, kinetics, stable isotope labeling and X-ray crystallo­graphy, were exploited to reach these conclusions and provide additional insights.

Olfactomedins are a family of modular proteins found in multicellular organisms that all contain five-bladed β-propeller olfactomedin (OLF) domains. In support of differential functions for the OLF propeller, the available crystal structures reveal that only some OLF domains harbor an internal calcium-binding site with ligands derived from a triad of residues. For the myocilin OLF domain (myoc-OLF), ablation of the ion-binding site (triad Asp, Asn, Asp) by altering the coordinating residues affects the stability and overall structure, in one case leading to misfolding and glaucoma. Bioinformatics analysis reveals a variety of triads with possible ion-binding characteristics lurking in OLF domains in invertebrate chordates such as Arthropoda (Asp–Glu–Ser), Nematoda (Asp–Asp–His) and Echinodermata (Asp–Glu–Lys). To test ion binding and to extend the observed connection between ion binding and distal structural rearrangements, consensus triads from these phyla were installed in the myoc-OLF. All three protein variants exhibit wild-type-like or better stability, but their calcium-binding properties differ, concomitant with new structural deviations from wild-type myoc-OLF. Taken together, the results indicate that calcium binding is not intrinsically destabilizing to myoc-OLF or required to observe a well ordered side helix, and that ion binding is a differential feature that may underlie the largely elusive biological function of OLF propellers.

Monoheme c-type cytochromes are important electron transporters in all domains of life. They possess a common fold hallmarked by three α-helices that surround a covalently attached heme. An intriguing feature of many monoheme c-type cytochromes is their capacity to form oligomers by exchanging at least one of their α-helices, which is often referred to as 3D domain swapping. Here, the crystal structure of NirC, a c-type cytochrome co-encoded with other proteins involved in nitrite reduction by the opportunistic pathogen Pseudomonas aeruginosa, has been determined. The crystals diffracted anisotropically to a maximum resolution of 2.12 Å (spherical resolution of 2.83 Å) and initial phases were obtained by Fe-SAD phasing, revealing the presence of 11 NirC chains in the asymmetric unit. Surprisingly, these protomers arrange into one monomer and two different types of 3D domain-swapped dimers, one of which shows pronounced asymmetry. While the simultaneous observation of monomers and dimers probably reflects the interplay between the high protein concentration required for crystallization and the structural plasticity of monoheme c-type cytochromes, the identification of conserved structural motifs in the monomer together with a comparison with similar proteins may offer new leads to unravel the unknown function of NirC.

A lipid droplet (LD) core of a cell consists mainly of neutral lipids, triacylglycerols and/or steryl esters (SEs). The structuration of these lipids inside the core is still under debate. Lipid segregation inside LDs has been observed but is sometimes suggested to be an artefact of LD isolation and chemical fixation. LD imaging in their native state and in unaltered cellular environments appears essential to overcome these possible technical pitfalls. Here, imaging techniques for ultrastructural study of native LDs in cellulo are provided and it is shown that LDs are organized structures. Cryo soft X-ray tomography and deep-ultraviolet (DUV) transmittance imaging are showing a partitioning of SEs at the periphery of the LD core. Furthermore, DUV transmittance and tryptophan/tyrosine auto-fluorescence imaging on living cells are combined to obtain complementary information on cell chemical contents. This multimodal approach paves the way for a new label-free organelle imaging technique in living cells.

This paper reports on the two-scale fractal structure of chromatin organization in the nucleus of the HeLa cell.

This work presents the crystal structure determination of two elusive polymorphs of furazidin, an antibacterial agent, employing a combination of crystal structure prediction (CSP) calculations and an NMR crystallography approach. Two previously uncharacterized neat crystal forms, one of which has two symmetry-independent molecules (form I), whereas the other one is a Z' = 1 polymorph (form II), crystallize in P21/c and P1 space groups, respectively, and both are built by different conformers, displaying different intermolecular interactions. It is demonstrated that the usage of either CSP or NMR crystallography alone is insufficient to successfully elucidate the above-mentioned crystal structures, especially in the case of the Z' = 2 polymorph. In addition, cases of serendipitous agreement in terms of 1H or 13C NMR data obtained for the CSP-generated crystal structures different from the ones observed in the laboratory (false-positive matches) are analyzed and described. While for the majority of analyzed crystal structures the obtained agreement with the NMR experiment is indicative of some structural features in common with the experimental structure, the mentioned serendipity observed in exceptional cases points to the necessity of caution when using an NMR crystallography approach in crystal structure determination.

A recent study of dog bones excavated from archaeological sites on the Channel Islands of California has cast new light on the past ecology of the islands and the impact that domestic dogs--brought to the islands by Native Americans more than 6,000 years ago—may have once had on the islands’ animals and ecosystems.

The post Dog bones reveal ecological history of California’s Channel Islands appeared first on Smithsonian Insider.

New measurements show that the Milky Way is bigger and more massive than previous data suggested, putting us on equal footing with our neighbor. Specifically, the Milky Way is 15 percent larger in size and contains 50 percent more mass. That is the cosmic equivalent of a 5-foot-5, 140-pound man suddenly bulking up to the size of a 6-foot-3, 210-pound NFL linebacker.

The post New research reveals our galaxy is much larger than we thought appeared first on Smithsonian Insider.

A new Smithsonian study that examines 10 million years of the evolution of tiny coral-like organisms called cupuladriid bryzoans has revealed that some species of this organism lingered on earth for more than one million years after the event that ultimately caused their extinction: the rising of the Isthmus of Panama.

The post Fossils of tiny cupuladriid colonies reveal extinction can lag more than one million years after its cause appeared first on Smithsonian Insider.

Testing caterpillars’ taste buds is no simple task. Just like your local salad bar, plants in the wild come in different shapes, textures and flavors. Herbivores rely on each of these cues to tell them what to eat. Deciphering this code is Lind’s task. He’s examining 40 different plant species – half invasive, half native.

The post Salad science: Coaxing caterpillars to reveal the secrets of their leafy desires appeared first on Smithsonian Insider.

A new census of tropical sulfur butterflies (Aphrissa statira) migrating across the Panama Canal has revealed the central role that weather plays in determining why populations of these lemon-yellow insects vary from year to year.

The post A dry spring in Panama means more sulfur butterflies, study reveals appeared first on Smithsonian Insider.

In a series of ongoing experiments on Barro Colorado Island in the Panama Canal, Kays and other researchers are using camera traps, radio collars and palm nuts with tracking transmitters attached to them to take a closer look at the nut-hoarding strategies of the agouti.

The post Camera traps & radio collars reveal hoarding strategies of the South American agouti appeared first on Smithsonian Insider.

Birds do it. Bees do it. And in a laboratory in northern California, scientists using bumblebees recently figured out the best way to measure it--vertical lift!

The post Laboratory tests reveal precise way to measure vertical lift in bumblebees and other small insects and birds appeared first on Smithsonian Insider.

Long before dawn on a recent morning, Katie Milton and a group of stalwart volunteers, each armed with flashlight and compass, spread out into the jungle to take up positions at 35 listening stations marked on maps of the island.

The post Census reveals 1,200 howler monkeys living on Barro Colorado Island appeared first on Smithsonian Insider.

To understand the effects of road salting on ants, Michael Kaspari of the Smithsonian Tropical Research Institute and the University of Oklahoma led a team that looked at how ant colonies are affected by these conditions; their research is published in a recent issue of the journal Ecological Entomology.

The post Study reveals road salt may promote health and well-being of roadside ant colonies appeared first on Smithsonian Insider.

An instrument on board NASA's Solar Dynamics Observatory, developed by Smithsonian scientists, is giving unprecedented views of the Sun's innermost corona 24 hours a day, 7 days a week.

The post Smithsonian instrument reveals Sun’s innermost corona appeared first on Smithsonian Insider.

Evidence for a diversified sea-based economy among North American inhabitants dating from 12,200 to 11,400 years ago is emerging from three sites on California's Channel Islands.

The post New archaeological evidence reveals California’s Channel Islands as North America’s earliest seafaring economy appeared first on Smithsonian Insider.

In recent research on Santa Rosa Island off the coast of Southern California, isotope readings of carbon and nitrogen found in the bones of Chumash Indians and domestic dogs excavated from archaeological sites show that both humans and dogs have nearly identical signatures of stable isotopes.

The post Ancient bond between humans and dogs revealed in isotopic signatures of their bones appeared first on Smithsonian Insider.

The discovery of a pattern of X-ray “stripes” in the remains of an exploded star may provide the first direct evidence that a cosmic event […]

The post X-ray stripes in exploded star may reveal highest energies of cosmic rays produced in our Galaxy appeared first on Smithsonian Insider.

The new research reveals that from the period between 1100-1600 small agricultural settlements up and down the Delaware River Valley caused a 50-percent increase in sediment runoff into the Delaware River.

The post Study reveals environmental impact of American Indian farms centuries before Europeans arrived in North America appeared first on Smithsonian Insider.

By compiling and comparing long-term data from stranding records and visual sighting records, both taken from nearly every ocean basin in the world, Pyenson verified that stranding records “faithfully reflect the number of species and the relative abundance” found in live surveys.

The post Stranding records are faithful reflection of live whale and dolphin populations, new study reveals appeared first on Smithsonian Insider.

One of the most challenging aspects of this research is simply studying these insects as they are falling, says Yanoviak, a tropical arthropod ecologist at the University of Arkansas, Little Rock. Small body size, rapid descent, and the long distances that they can fall, make accurate data taking a challenge.

The post Lofty experiments with gliding ants reveals secrets of their unusual flight appeared first on Smithsonian Insider.

A new study shows that the desert tortoise, thought to be a single species for the last 150 years, is in fact two separate and distinct species, based on DNA evidence and biological and geographical distinctions.

The post New study reveals desert tortoise is actually two distinct species appeared first on Smithsonian Insider.

Gray whales survived many cycles of global cooling and warming over the past few million years, likely by exploiting a more varied diet than they do today, according to a new study by University of California, Berkeley, and Smithsonian Institution paleontologists.

The post Varied diet has allowed gray whales to survive millions of years, study reveals appeared first on Smithsonian Insider.

Small tissue samples collected from 238 wild turtles at 15 different locations across their range in Southern Mexico, Belize and Guatemala revealed a “surprising lack” of genetic structure, the scientists write in a recent paper in the journal Conservation Genetics.

The post Endangered river turtle’s genes reveal ancient influence of Maya Indians appeared first on Smithsonian Insider.

The far-out planet, named 55 Cancri e, is twice as big as Earth and nearly nine times more massive. It is most likely composed of rocky material, similar to Earth, supplemented with light elements such as water and hydrogen gas. Scientists estimate the planet’s surface is much hotter than ours: close to 2,700 degrees Celsius.

The post Stellar eclipse gives glimpse of exoplanet: New data reveals a ‘super-Earth’ next door, astronomically speaking appeared first on Smithsonian Insider.

A new study on the dodo’s island home of Mauritius in the Indian Ocean, paints a picture of this unusual bird as an intrepid survivor on par with the giant tortoise for its resiliency.

The post Dodo bird a resilient island survivor before the arrival of humans, study reveals appeared first on Smithsonian Insider.

New observations by NASA's Wide-field Infrared Survey Explorer, or WISE, show there are significantly fewer near-Earth asteroids in the mid-size range than previously thought.

The post Infrared survey reveals fewer near-Earth asteroids than previously thought appeared first on Smithsonian Insider.

In a new paper, Avi Loeb, of the Harvard-Smithsonian Center for Astrophysics, and Edwin Turner, Princeton University, suggest a new technique for finding aliens: look for their city lights.

The post City lights could reveal E.T. civilization appeared first on Smithsonian Insider.

Astronomers are confident the Cygnus X-1 system contains a black hole, and with these latest studies they have remarkably precise values of its mass, spin, and distance from Earth.

The post New details on birth of black hole Cygnus X-1 revealed by Chandra X-ray Observatory appeared first on Smithsonian Insider.

Ornithologists Carla Dove and Storrs Olson used 700- to 1,100-year-old feathers from a long extinct species of Hawaiian ibis to help determine the bird’s place in the ibis family tree. The feathers are the only known plumage of any of the prehistorically extinct birds that once inhabited the Hawaiian Islands.

The post Fossil feathers from a Hawaiian cave help reveal lineage of extinct, flightless ibis appeared first on Smithsonian Insider.

A recent decline in Ovenbirds (Seiurus aurocapilla), a ground-nesting migratory songbird, in forests in the northern Midwest United States is being linked by scientists to a seemingly unlikely culprit: earthworms.

The post Earthworms to blame for decline of Ovenbirds in northern Midwest forests, study reveals appeared first on Smithsonian Insider.

Smithsonian Conservation Biology Institute scientists and collaborators have found that the island scrub-jay’s population on Santa Cruz Island—its only habitat—is significantly smaller than previously believed […]

The post New count reveals scrub-jay on Santa Cruz Island is among rarest bird species in the U.S. appeared first on Smithsonian Insider.

Found in well preserved shale deposits the fossils are so detailed that scientists were able to determine they represent two previously unknown species.

The post Discovery of new prehistoric mosquitoes reveal these blood-suckers have changed little in 46 million years appeared first on Smithsonian Insider.

Using echolocation alone the bats found, identified and captured insects perched motionless and silent on the leaves of plants.

The post Common tropical bat uses echolocation with precision previously considered impossible, new experiments reveal appeared first on Smithsonian Insider.

Small migratory male birds that winter in a stressful environment age faster than those that winter in a high-quality habitat, according to research stemming from […]

The post Small migratory birds age faster in stressful places, study reveals appeared first on Smithsonian Insider.

Among vertebrates few animals rival poison dart frogs for their vibrant electric blue, yellow, red and orange skin colors. Some experts have long believed these […]

The post Poison dart frog toxins best suited for deterring biting arthropods, research reveals appeared first on Smithsonian Insider.

Cheeseburgers. Ice cream. French fries. These are a few of the culprits, doctors warn us, responsible for atherosclerosis, a disease commonly known as hardening of […]

The post Ancient mummies reveal atherosclerosis is very likely just a part of aging appeared first on Smithsonian Insider.

Recent spectroscopic analysis of macaroni penguin (Eudyptes chrysolophus) crest feathers and king penguin (Aptenodytes patagonicus) neck feathers have shown they contain a yellow pigment that […]

The post Yellow pigment in penguin feathers is chemically distinct, spectroscopic studies reveal appeared first on Smithsonian Insider.

Douglas Owsley, the division head for physical anthropology at the Smithsonian’s National Museum of Natural History, presented today a forensic analysis of 17th-century human remains […]

The post Forensic analysis of 17th-century human remains at Jamestown, Va., reveals evidence of survival cannibalism appeared first on Smithsonian Insider.

W49A might be one of the best-kept secrets in our galaxy. This star-forming region shines 100 times brighter than the Orion nebula, but is so […]

The post SMA reveals giant star cluster in the making appeared first on Smithsonian Insider.

A newly released study focusing on an extinct species, the Caribbean monk seal (Monachus tropicalis), has revealed just how evolutionarily unique its only two living […]

The post Too valuable to lose: Extinct relative reveals rarity of last two remaining monk seal species appeared first on Smithsonian Insider.

The name Panama is said to mean “abundance of fish.” Now a new study estimates that between 1950 and 2010, the amount of fish taken […]

The post Panamanian fish catch is vastly under-reported, study reveals appeared first on Smithsonian Insider.

Einstein’s Theory of General Relativity predicts that accelerated masses emit gravitational waves, or ripples in space-time. Even though gravitational waves have yet to be detected […]

The post Gemini reveals a gravitational wave source in hiding appeared first on Smithsonian Insider.

Defining what makes a star “Sun-like” is as difficult as defining what makes a planet “Earth-like.” A solar twin should have a temperature, mass, and […]

The post Sun-like stars reveal their ages 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.

Cassiopeia A, or Cas A for short, is one of the most well studied supernova remnants in our galaxy. But it still holds major surprises.  […]

The post 3-D Map of Supernova Remnant Reveals Frothy Interior appeared first on Smithsonian Insider.