Science Concentrates ASTROCHEMISTRY
Success and loss for ExoMars 2016 Orbiter arrives safely to map Mars’s trace gases, but lander crashes on surface The missing Mars lander Schiaparelli, meant to touch down on the Red Planet on Oct. 19, has been spotted, confirming that its landing did not go as planned. Two days after the craft went silent during its descent, NASA’s Mars Reconnaissance Orbiter sent back images of Mars’s surface highlighting Schiaparelli’s remains at the intended landing site. ExoMars 2016, a joint mission with the European Space Agency (ESA) and Russia’s Roscosmos, launched Schiaparelli along with another craft, the Trace Gas Orbiter (TGO), in March. TGO successfully maneuvered into orbit around Mars and “is now ready for science,” said Johann-Dietrich Woerner, ESA’s director general, at a briefing at ESA’s mission control center in Darmstadt, Germany, earlier this month. The lander, however, crashed and likely exploded. Data transmitted from the lander before impact suggest that a computer glitch caused its braking system to malfunction. The lander then slammed into Mars’s surface at greater than 300 km per hour. Andrea Accomazzo, head of ESA’s solar
system and planetary missions division, confirmed that the lander’s braking rockets did fire, but only for a few seconds, “a time much shorter than we were expecting.” Schiaparelli was intended to In this artist’s test technologies that would rendition, the be used on a rover planned for ExoMars 2016 launch in 2020. mission’s TGO, carrying the Schiaparelli On Oct. 21, NASA released lander, prepares to orbit Mars. images from its orbiter showing a “before” picture of Mars’s unblemished surface followed by an “after” signature for water ice—1 meter below picture of the surface marred by a black Mars’s surface. speck. Scientists are particularly interested in At the briefing, the ExoMars team did its Mars’s production of methane. On Earth, best to shift focus from the lander’s malmicrobes are responsible for producing function to TGO, which will orbit Mars for most atmospheric methane, but the gas can four years. also be produced by geological processes. With cameras and spectrometers far NASA’s rover Curiosity detected a spike more sensitive than ESA’s previous orof methane on Mars two years ago, the biter, Mars Express, TGO will map trace source of which remains a mystery. Scienatmospheric gases such as nitrogen oxides, tists hope that TGO might help identify acetylene, and methane over the seasons. where and when methane is produced on TGO will also be able to detect hydrogen—a Mars.—ELIZABETH WILSON
Solid-state iron-bismuth compound created Elusive compound completes iron pnictide series The first-ever solid-state material reported to contain iron-bismuth bonds, FeBi2, has been prepared by a team led by Danna E. Freedman of Northwestern University (ACS Cent. Sci. 2016,
DOI: 10.1021/acscentsci.6b00287). Iron and bismuth each react with multiple elements across the periodic table but are largely immiscible with each other, despite the fact that iron readily combines with all of the other group 15 elements to form superconducting materials. Chemists currently don’t understand the lack of reactivity between iron and bismuth.
FeBi2 is the first solid-state material reported with ironbismuth bonds (Fe is red, Bi is purple).
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C&EN | CEN.ACS.ORG | OCTOBER 31, 2016
Freedman and colleagues created FeBi2 by combining the two elements in a diamond anvil cell at 30 gigapascals and 1,500 K. In the crystal structure, each iron atom is coordinated by eight bismuth atoms arranged into squares above and below the iron. The squares of bismuth atoms sit twisted relative to each other. The high pressure stabilizes the Fe–Bi bonds in the material, which is also held together by Bi–Bi bonds. The Fe–Bi bond lengths are 0.2719 nm, while the Bi–Bi interactions range from 0.2948 to 0.3419 nm. The researchers were able to decompress the FeBi2 down to 3 GPa before it decomposed. That behavior suggests that there might be a way to quickly cool and slowly decompress the material to study and perhaps even use it at ambient pressure—0.0001 GPa—and low temperature, the researchers say.—JYLLIAN KEMSLEY
CREDIT: ESA/ATG MEDIALAB ( TGO AND LANDER); ACS CENT. SCI. (CRYSTAL STRUCTURE)
INORGANIC CHEMISTRY
RENEWABLES
CREDIT: DAVID SCHARF/SCIENCE SOURCE
Formaldehyde salvages lignin During biomass processing, tens of millions of metric tons of lignin waste are produced each year. This wasteful sludge could be avoided by simply adding formaldehyde in the early stages of the processing, chemists report. The formaldehyde treatment chemically protects the natural polymer lignin so that it can be transformed into valuable chemical feedstocks. Lignin accounts for as much as 30% of plants and trees and is made up of valuable aromatic subunits. “Lignin is one of the few natural sources of aromatics, and aromatics are absolutely essential in our chemical industry,” says Jeremy S. Luterbacher, a chemist at the Swiss Federal Institute of Technology, Lausanne (EPFL), who spearheaded the work. Despite its rich molecular makeup, lignin becomes a waste product because the process that’s used to separate it from a plant’s cellulose and hemicellulose components— which are valuable biofuel feedstocks—causes irreversible C–C bonds to form within the lignin, creating a sludge. Luterbacher’s team found that formaldehyde could chemically prevent those C–C bonds from forming at two key positions (Science 2016, DOI: 10.1126/science. aaf7810). Formaldehyde adds a hydroxymethyl group at a nucleophilic position on one of lignin’s aromatic components and creates a 1,3-dioxane at a position that can become an electrophile. These two blocking strategies prevent irreversible C–C bond formation between the nucleophile and electrophile in the lignin. So far, Luterbacher and colleagues have scaled the reaction up to 1 L. They’ve also patented the process and are currently deciding whether to move forward by starting their own company or by partnering with an existing firm.—BETHANY
HALFORD
Hookworms, which are about 10 mm long, spit out a soup of molecules that modulate their hosts’ immune system.
DRUG DISCOVERY
Looking for asthma therapies in worm spit Protein secreted by hookworms helps block immune responses associated with asthma in mice A bloodsucking parasitic worm that latches onto the lining of our gut doesn’t sound like a helpful organism. But a new study suggests that the spit from such a parasite could inspire treatments for inflammatory diseases such as asthma. An international team of researchers reports that a protein secreted by hookworms reduces inflammation in the lungs of asthmatic mice (Sci. Transl. Med. 2016, DOI: 10.1126/scitranslmed.aaf8807). The protein works not by suppressing the mouse’s entire immune system, but by regulating only certain immune cells involved in allergic responses. This feat suggests that the molecule could lead to relatively safe therapeutics. “Right now, we use a lot of drugs with potent side effects that can make people immunocompromised,” says Joel V. Weinstock of Tufts University School of Medicine, who was not involved in the work. “If we could understand these pathways that a little old worm uses, then there is the possibility to develop powerful but very safe drugs.” Weinstock was one of the first scientists in the 1990s to draw a possible connection between parasitic worms, known as helminths, and inflammatory diseases such as asthma, ulcerative colitis, and allergies. He and other researchers noticed that, in the developed world, improved sanitation made worm infections almost nonexistent, while the incidence of these immune diseases had increased significantly. That and other data led the scientists to wonder if the absence of the parasites disrupted the regulation of some people’s immune systems. In these increasingly common dis-
eases, a person’s immune system lashes out at typically innocuous substances, such as pollen or even the body’s own cells, leading to harmful inflammation. Recently, several clinical trials have shown that infecting patients with some parasitic worms can reduce that chronic inflammation. But a treatment based on infecting people with parasites presents many problems. Severine Navarro, who is a research fellow in Alex Loukas’s lab at James Cook University, and colleagues decided to go looking for an alternative. In particular, they searched for a molecular explanation for how hookworms can invade our guts, feed off our red blood cells for years, and never get rejected by our immune systems. The team focused on a soup of molecules that hookworms secrete when they invade a host. The scientists wondered if some of those molecules programmed the hosts’ immune system to stand down. AIP-2, a protein they found in the secretion soup, reduced signs of airway inflammation and improved lung function in mice given an asthmalike condition. Further experiments suggested that the protein works through promoting the development of immune cells that regulate cells involved in attacking allergens or the body’s own tissue. These regulatory cells calm those attackers. Navarro says she and her colleagues are sifting through the worm’s secretions to find other immune-modulating molecules. They are also working on producing a smaller version of AIP-2 that retains its activity but would be easier to produce and deliver as a therapeutic.—MICHAEL
TORRICE OCTOBER 31, 2016 | CEN.ACS.ORG | C&EN
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