Two new mononuclear metal complexes involving the bidentate Schiff base ligand 2,4,6-trimethyl-N-[(pyridin-2-yl)methyl­idene]aniline (C15H16N2 or PM-TMA), [Mn(NCS)2(PM-TMA)2] (I) and [Ni(NCS)2(PM-TMA)2] (II), were synthesized and their structures determined by single-crystal X-ray diffraction. Although the title compounds crystallize in different crystal systems [triclinic for (I) and monoclinic for (II)], both asymmetric units consist of one-half of the complex mol­ecule, i.e. one metal(II) cation, one PM-TMA ligand, and one N-bound thio­cyanate anion. In both complexes, the metal(II) cation is located on a centre of inversion and adopts a distorted octa­hedral coordination environment defined by four N atoms from two symmetry-related PM-TMA ligands in the equatorial plane and two N atoms from two symmetry-related NCS− anions in a trans axial arrangement. The tri­methyl­benzene and pyridine rings of the PM-TMA ligand are oriented at dihedral angles of 74.18 (7) and 77.70 (12)° for (I) and (II), respectively. The subtle change in size of the central metal cations leads to a different crystal packing arrangement for (I) and (II) that is dominated by weak C—H⋯S, C—H⋯π, and π–π inter­actions. Hirshfeld surface analysis and two-dimensional fingerprint plots were used to qu­antify these inter­molecular contacts, and indicate that the most significant contacts in packing are H⋯H [48.1% for (I) and 54.9% for (II)], followed by H⋯C/C⋯H [24.1% for (I) and 15.7% for (II)], and H⋯S/S⋯H [21.1% for (I) and 21.1% for (II)].

In the crystal structure of the title compound, [Fe(NCS)2(C12H9NO)2(CH4O)2], the FeII cations are octa­hedrally coordinated by two N atoms of 4-benzoyl­pyridine ligands, two N atoms of two terminal iso­thio­cyanate anions and two methanol mol­ecules into discrete complexes that are located on centres of inversion. These complexes are linked via inter­molecular O—H⋯O hydrogen bonds between the methanol O—H H atoms and the carbonyl O atoms of the 4-benzoyl­pyridine ligands, forming layers parallel to (101). Powder X-ray diffraction proved that a pure sample was obtained but that this compound is unstable and transforms into an unknown crystalline phase within several weeks. However, the solvent mol­ecules can be removed by heating in a thermobalance, which for the aged sample as well as the title compound leads to the formation of a compound with the composition Fe(NCS)2(4-benzoyl­pyridine)2, which exhibits a powder pattern that is similar to that of Mn(NCS)2(4-benzoyl­pyridine)2.

The new heterometallic complex, aqua-1κO-bis­(μ2-2-imino­methyl-6-meth­oxy­phenolato-1κ2O1,O6:2κ2O1,N)bis­(thio­cyanato-1κN)calcium(II)copper(II), [CaCu(C8H8NO2)2(NCS)2(H2O)], has been synthesized using a one-pot reaction of copper powder, calcium oxide, o-vanillin and ammonium thio­cyanate in methanol under ambient conditions. The Schiff base ligand (C8H9NO2) is generated in situ from the condensation of o-vanillin and ammonia, which is released from the initial NH4SCN. The title compound consists of a discrete binuclear mol­ecule with a {Cu(μ-O)2Ca} core, in which the Cu⋯Ca distance is 3.4275 (6) Å. The coordination geometries of the four-coordinate copper atom in the [CuN2O2] chromophore and the seven-coordinate calcium atom in the [CaO5N2] chromophore can be described as distorted square planar and penta­gonal bipyramidal, respectively. In the crystal, O—H⋯S hydrogen bonds between the coordinating water mol­ecules and thio­cyanate groups form a supra­molecular chain with a zigzag-shaped calcium skeleton.

The title centrosymmetric NiII complex, [Ni(NCS)2(C15H22N2O2)2], crystallizes with one half mol­ecule in the asymmetric unit of the monoclinic unit cell. The complex adopts an octa­hedral coordination geometry with two mutually trans benzyl-2-(heptan-4-yl­idene)hydrazine-1-carboxyl­ate ligands in the equatorial plane with the axial positions occupied by N-bound thio­cyanato ligands. The overall conformation of the mol­ecule is also affected by two, inversion-related, intra­molecular C—H⋯O hydrogen bonds. The crystal structure features N—H⋯S, C—H⋯S and C—H⋯N hydrogen bonds together with C—H⋯π contacts that stack the complexes along the b-axis direction. The packing was further explored by Hirshfeld surface analysis. The thermal properties of the complex were also investigated by simultaneous TGA–DTA analyses.

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.

The Y128F single mutant of p-hydroxymandelate oxidase (Hmo) is capable of oxidizing mandelate to benzoate via a four-electron oxidative decarboxylation reaction. When benzoylformate (the product of the first two-electron oxidation) and hydrogen peroxide (an oxidant) were used as substrates the reaction did not proceed, suggesting that free hydrogen peroxide is not the committed oxidant in the second two-electron oxidation. How the flavin mononucleotide (FMN)-dependent four-electron oxidation reaction takes place remains elusive. Structural and biochemical explorations have shed new light on this issue. 15 high-resolution crystal structures of Hmo and its mutants liganded with or without a substrate reveal that oxidized FMN (FMNox) possesses a previously unknown electrophilic/nucleophilic duality. In the Y128F mutant the active-site perturbation ensemble facilitates the polarization of FMNox to a nucleophilic ylide, which is in a position to act on an α-ketoacid, forming an N5-acyl-FMNred dead-end adduct. In four-electron oxidation, an intramolecular disproportion­ation reaction via an N5-alkanol-FMNred C'α carbanion intermediate may account for the ThDP/PLP/NADPH-independent oxidative decarboxylation reaction. A synthetic 5-deaza-FMNox cofactor in combination with an α-hydroxyamide or α-ketoamide biochemically and structurally supports the proposed mechanism.

Fragment-based molecular-replacement methods can solve a macromolecular structure quasi-ab initio. ARCIMBOLDO, using a common secondary-structure or tertiary-structure template or a library of folds, locates these with Phaser and reveals the rest of the structure by density modification and autotracing in SHELXE. The latter stage is challenging when dealing with diffraction data at lower resolution, low solvent content, high β-sheet composition or situations in which the initial fragments represent a low fraction of the total scattering or where their accuracy is low. SEQUENCE SLIDER aims to overcome these complications by extending the initial polyalanine fragment with side chains in a multisolution framework. Its use is illustrated on test cases and previously unknown structures. The selection and order of fragments to be extended follows the decrease in log-likelihood gain (LLG) calculated with Phaser upon the omission of each single fragment. When the starting substructure is derived from a remote homolog, sequence assignment to fragments is restricted by the original alignment. Otherwise, the secondary-structure prediction is matched to that found in fragments and traces. Sequence hypotheses are trialled in a brute-force approach through side-chain building and refinement. Scoring the refined models through their LLG in Phaser may allow discrimination of the correct sequence or filter the best partial structures for further density modification and autotracing. The default limits for the number of models to pursue are hardware dependent. In its most economic implementation, suitable for a single laptop, the main-chain trace is extended as polyserine rather than trialling models with different sequence assignments, which requires a grid or multicore machine. SEQUENCE SLIDER has been instrumental in solving two novel structures: that of MltC from 2.7 Å resolution data and that of a pneumococcal lipoprotein with 638 residues and 35% solvent content.

The crystal structure of the mineral malayaite has been studied by single-crystal X-ray diffraction at a temperature of 20 K and by calculation of its phonon dispersion using density functional perturbation theory. The X-ray diffraction data show first-order satellite diffraction maxima at positions q = 0.2606 (8)b*, that are absent at room temperature. The computed phonon dispersion indicates unstable modes associated with dynamic displacements of the Ca atoms. The largest-frequency modulus of these phonon instabilities is located close to a wavevector of q = 0.3b*. These results indicate that the malayaite crystal structure is incommensurately modulated by static displacement of the Ca atoms at low temperatures, caused by the softening of an optic phonon with Bg symmetry.

The crystal structure of malayaite, CaSnOSiO4, at T = 20 K has been refined, based on the presence of satellite reflections with a modulation vector of 0.26b*. The structural modulation is attributed to a soft optic phonon, dominated by motion of the Ca atoms.

Staff had been on a pregnancy watch focused on the 3 1/2-year-old clouded leopard Jao Chu (JOW-chew) for four days. Jao Chu gave birth to the first cub at 6:04 p.m. and the second cub at 6:20 p.m.

The post Clouded leopard cubs born at National Zoo’s Front Royal campus on Valentine’s Day appeared first on Smithsonian Insider.

The words “box jelly” may bring to mind something sweet and tasty, but the banded box jelly of Bonaire is a highly venomous jellyfish with […]

The post “Ohboya!” It’s the Bonaire banded box jellyfish, a new species appeared first on Smithsonian Insider.

Faced with insufficient time and inadequate library resources to tackle the problem on their own, they instead posted a catalog of specimen images to Facebook and turned to their network of colleagues for help.

The post Facebook friends help scientists quickly identify nearly 5,000 fish specimens collected in Guyana 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.

For the first time in decades, researchers have found a new bird species in the United States. Based on a specimen collected in 1963 on Midway Atoll, Northwestern Hawaiian Islands, biologists have described a new species of seabird, Bryan’s shearwater

The post Bryan’s shearwater, new Hawaiian seabird species, discovered appeared first on Smithsonian Insider.

The Smithsonian-Mason School of Conservation, a unique program in terms of its academic offerings and contributions to the field of conservation, celebrated the completion of its expansive new academic facilities today, Oct. 18, at the Smithsonian Conservation Biology Institute in Front Royal, Va.

The post Smithsonian Conservation Biology Institute and George Mason University dedicate new academic facilities in Front Royal, Va. appeared first on Smithsonian Insider.

What crunchy food did Americans spend $5.5 billion on last year—with sales that spiked before snow and ice storms? If you guessed birdseed then you […]

The post Simple tips to keep your backyard birds healthy this winter appeared first on Smithsonian Insider.

Scientists at the Smithsonian Conservation Biology Institute (SCBI) have found that poaching is an emerging crisis for Asian elephants in Myanmar. Researchers first became aware […]

The post Elephant poaching crisis in Myanmar appeared first on Smithsonian Insider.

The Weeping Goldsmith, written as a first-person narrative, follows Botanist John Kress through nine years as he surveys Myanmar’s teak forests, bamboo thickets, timber plantations, rivers and mangroves to document its incredible botanical biodiversity.

The post Smithsonian botanist writes book on his discoveries in the secret land of Myanmar appeared first on Smithsonian Insider.

The scientists staked out dozens of the gingers night and day while the plants flowered, but no long-proboscid pollinator ever appeared. Climate change, they surmised, was responsible for the loss of this highly specialized and now, perhaps forever unknown insect.

The post With specialist pollinator absent, Himalayan gingers must adapt appeared first on Smithsonian Insider.

Muted moans of sadness punctuated the pandemonium that engulfed the Smithsonian’s National Zoo over the weekend as throngs of well-wishing visitors flooded through the Zoo’s […]

The post Bon Voyage Bao Bao! Washington loses its precious treasure appeared first on Smithsonian Insider.

Smithsonian scientists have discovered two new gecko species—the Lenya banded bent-toed gecko (Cyrtodactylus lenya) and Tenasserim Mountain bent-toed gecko (C. payarhtanesnsis)—in the little-studied lowland forests […]

The post Smithsonian Scientists Discover Two New Gecko Species in Vanishing Myanmar Rainforest appeared first on Smithsonian Insider.

The enanti­opure monopyrrolidine derivative (2S)-methyl (Z)-5-(2-tert-but­oxy-1-cyano-2-oxo­ethyl­idene)pyrrolidine-2-carboxyl­ate, C13H18N2O4, (1), represents a potential ligand and an attractive inter­mediate for the synthesis of chiral metal com­plexes. At the mol­ecular level, the com­pound features an intra­molecular N—H⋯O hydrogen bond; neighbouring mol­ecules inter­act via N—H⋯N contacts to form chains along [100]. Due to its elemental com­position, resonant scattering of the target com­pound is entirely insignificant for diffraction experiments with Mo Kα and small even for Cu Kα radiation. A preliminary study with the harder radiation type confirmed the chiral space group and the suitability of the single crystal chosen; as expected, the results concerning the absolute structure remained com­pletely inconclusive. A second data collection with the longer wavelength gave satisfactory quality indicators for the correct handedness of the mol­ecule, albeit with high standard uncertainties. The absolute configuration has been assessed independently: CD spectra for both enanti­omers of the target mol­ecule were calculated and the spectrum for the S-configured stereoisomer was in agreement with the experiment. The Cotton effect of (1) may be ascribed to π–π* transitions from HOMO to LUMO and from HOMO to LUMO+1. As both independent techniques agree with respect to the handedness of the target mol­ecule, the absolute structure may be assigned with a high degree of confidence.

(The Paypers) Forter has released the seventh edition of its Fraud Attack Index, tracking shifting behaviours...

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The Maya of Central America are thought to have been a kinder, gentler civilization, especially compared to the Aztecs of Mexico. At the peak of Mayan culture some 1,500 years ago, warfare seemed ritualistic, designed to extort ransom for captive royalty or to subjugate rival dynasties, with limited impact on the surrounding population. Only later, archeologists thought, did increasing drought and climate change lead to total warfare -- cities and dynasties were wiped off the map in so-called termination events -- and the collapse of the lowland Maya civilization around 1,000 A.D. (or C.E., current era). New evidence unearthed by National Science Foundation-funded researchers call all this into question, suggesting that the Maya engaged in scorched-earth military campaigns -- a strategy that aims to destroy anything of use, including cropland -- even at the height of their civilization, a time of prosperity and artistic sophistication. The finding also indicates that this increase in warfare, possibly associated with climate change and resource scarcity, was not the cause of the disintegration of the lowland Maya civilization.

Image credit: Francisco Estrada-Belli/Tulane

The U.S. National Academy of Sciences and the Royal Society, the national science academy of the U.K., released a joint publication today in Washington, D.C., that explains the clear evidence that humans are causing the climate to change, and that addresses a variety of other key questions commonly asked about climate change science.

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome -- commonly referred to as ME/CFS -- is a legitimate, serious, and complex systemic disease that frequently and dramatically limits the activities of affected individuals, says a new report from the Institute of Medicine.

When I was a kid, it was clear, when traveling with my family in summer—That we were cosmopolitan in attitude, but bohemian in cash.  We would criss-cross Europe, yes—  But we were car-camping, our luggage strapped to the roof of our shuddering VW fastback.  Lunch was sweaty cheese and days-old ham from an unrefrigerated metal cookie tin.  The bathrooms in our one-star hotels were. . . shared.

When I travel now with my teen daughters, I'd say we are basically middle-class—?  But due to the complexity of mom's travel points—?  We never know if we'll have a first or third world experience.

For instance, recently, using air miles, we flew United to Denver for free!  Mostly.  I splurged on the extra hundred dollars so we could actually sit together, rather than, as Basic Economy requires, being seated randomly all over the plane.  I did not allow any extra bags carried or checked, because my girls may one day go to college.

Kayak-ing the white water rapids of cheap car rentals, I'd found a company called ACE offering a tiny car that looked like a Yugo—  But, as they used to say at IKEA, "Impossible Price"! Upon arrival, I find out why. Our instructions? Walk past the Ground Transportation counter, get into "lane four," then turn left and walk half a mile, past all the Avis, Budget and Enterprise signs and wait, literally, and I quote, "under the sign that is blank."

 "I know that we're not Platinum members of anything," I grouse to my daughters, "but standing under a blank sign?  Can ACE at least not tape their logo up there?  It's so humiliating!"

"Maybe they didn't have enough money to commission a logo," says my older daughter.  Shuttle after shuttle whooshes by.

 "We'll be lucky if the car has four wheels!" says my younger.

Forty-five minutes later, the ACE shuttle finally arrives.  I'm strangely comforted that there are other passengers, as humiliated as we are.  We are the people too cheap to get a real rental car.  None of us make eye contact.  We study our crumpled Expedia printouts as though we are important business travelers splitting the atom.

We are shuttled to the far side of town.  Though not quite a van down by the river, the rental office is in fact a trailer. 

On the upside, we are led to a vehicle that, while splattered with mud, is a giant black Ford Explorer.  Added plus: it comes loaded with Sirius 1970's Radio!  The minus —  The first song that comes on is The Captain and Tenille, "You Better Shop Around!"

Next week: Running on Dr. Pepper, dry shampoo and Special K.

This content is from Southern California Public Radio. View the original story at SCPR.org.

A decade-by-decade display of how many active gas storage wells are still in use by Southern California Gas Company. Source: Division of Oil, Gas and Geothermal Resources and SoCalGas; Credit: Aaron Mendelson/KPCC

The Aliso Canyon gas leak broke out near Porter Ranch nearly four years ago. On Tuesday a City Councilman called for an investigation of a different underground gas field after troubling images surfaced on video. 

The video uses a special infrared camera to show a duck swimming in the Ballona Wetlands amid bubbles of gas. An environmental advocacy group, Food and Water Watch, says the gas is methane.  They released the video this week to push for the city to investigate the underground gas storage field in nearby Playa del Rey.

Southern California Gas Co. says the gas surfacing in the wetlands is naturally occurring and unrelated to its underground natural gas storage field in Playa del Rey.

This content is from Southern California Public Radio. View the original story at SCPR.org.

Celonis, a Germany-based...

For more than 120 years the Venus Table of the Dresden Codex -- an ancient Mayan book containing astronomical data -- has been of great interest to scholars around the world. The accuracy of its observations, especially the calculation of a kind of 'leap year' in the Mayan Calendar, was deemed an impressive curiosity used primarily for astrology.

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The Grolier Codex, an ancient document that is among the rarest books in the world, has been regarded with skepticism since it was reportedly unearthed by looters from a cave in Chiapas, Mexico, in the 1960s.

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A recent pan-European study has reviewed the factors which influence how annoyed a person feels about road traffic and aircraft noise. Among its findings, residents in terraced housing or apartments were less annoyed by road traffic noise than residents in semi-detached or detached housing.

A new study has assessed the annoyance caused by a combination of noises typically found on an industrial site. The results could help improve total noise annoyance prediction models. For example, it was found that ‘broadband’ noises, which consist of a wide range of frequencies, lead to more annoyance if they are combined with a specific additional set of low frequency noises, which can lead to an overall identical noise level.

A recent pan-European study has reviewed the factors which influence how annoyed a person feels about road traffic and aircraft noise. Among its findings, residents in terraced housing or apartments were less annoyed by road traffic noise than residents in semi-detached or detached housing.

The Alang-Sosiya shipbreaking yard in India is highly polluted with heavy metals, a study concludes. The researchers studied heavy metal contamination in sediments taken from the intertidal zone of the shipbreaking yard and compared them to a control site. The area was found to be ‘strongly polluted’ with copper, cobalt, manganese, lead and zinc.

Genpact sees over 100 clients closing their financial quarter digitally while others are doubling the pace of adoption of digital transformation.

The Akshaya Patra Foundation reduced the process time taken from planning the menu to delivery to schools by using mobility solution and automation.

An innovative reforestation technique has been used successfully to restore patches of forest in an area of Sardinia where traditional reforestation methods have previously failed. It was the first time the technique, known as the Miyawaki method, has been used to restore forests in a Mediterranean region.