SCIENCE & TECHNOLOGY CONCENTRATES
NEW CLASS OF RIBOZYMES FOUND
Fluorine chemistry has flourished during the past few years as organic chemists have been pressed to find easy, safe, and affordable fluorination reactions for making drug and agrochemical candidates. In the latest example, Patrick S. Fier and John F. Hartwig of the University of California, Berkeley, have created a method for selective C–H fluorination of nitrogen heterocycles (Science 2013, DOI: 10.1126/science.1243759). Heterocycles such as 2-fluoropyridines are highly sought after because their electronic properAcetonitrile, ties enable them to readily one hour, room temperature R R + AgF2 undergo further reactions to prepare more complex N N F derivatives and to help imR = various groups prove the potency of drugs. But fluorinated pyridines haven’t been readily available. Fier and Hartwig took inspiration from the classic Chichibabin pyridine amination reaction, in which sodium in NaNH2 binds to the ring nitrogen and then activates an adjacent C–H bond to add NH2 to the carbon. In the new work, the researchers used AgF2, whereby the silver binds to nitrogen and assists in installing fluorine on the adjacent carbon (shown). “This reaction will find immediate use because it is so easy to perform and provides access to high-value fluorinated heterocycles that are otherwise cumbersome to come by,” says organofluorine synthesis expert Tobias Ritter of Harvard University.—SR
MUMMIFIED BEEF JERKY FOUND IN PYRAMIDS Ancient Egyptians sent their elite to the afterlife well stocked for a long journey, with items as varied as jewels, hair combs, and even mummified beef jerky. Now, a team of researchers led by the University of Bristol’s Richard P. Evershed has found Preserved beef that, in some cases, the embalming agents ecules indicative found in the tomb of used to preserve meat were more valuable of Pistacia resins Egyptian Queen Tiye. in a mummified than ones commonly used to mummify people (Proc. Natl. Acad. Sci. USA 2013, meat sample DOI: 10.1073/pnas.1315160110). The team found in the tomb of Queen Tiye, wife determined that one sample of desiccated, of Amenhotep III, whose desalted meat was preserved with a resin decades-long reign is known for rived from the plant genus Pistacia, which being a particularly prosperous includes pistachio nut plants. In anera. Her high status may explain cient Egypt, Pistacia resins were why the beef in her tomb CO2H was treated with Pistacia H luxury items used to flavor meat, preserve wine, and resins instead of the animal H produce incense. The fat used to preserve meat mumteam identified oleanon- O mies that were buried with less H ic acid, isomasticadienoimportant people, the researchers ic acid, and other organic molnote.—SE Oleanonic acid CEN.ACS.ORG
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PROC. NATL. ACAD. SCI. USA
For the first time in almost a decade, biochemists have found a new class of ribozymes. These molecules are ribonucleic acids that catalyze chemical reactions and may play a role in gene regulation. By using bioinformatics tools to mine genome sequences, Ronald R. Breaker and coworkers at Yale University have found a new class of self-cleaving ribozymes, which they have dubbed twister ribozymes because their structural motif—three loops connected by double-stranded stems—resembles an Egyptian hieroglyph that translates as “twisted flax” (Nat. Chem. Biol. 2013, DOI: 10.1038/nchembio.1386). In addition to the core structural motif, the ribozymes also have two pseudoknots (structures that look like knots but aren’t actually knots in a topological sense) that are necessary for catalysis. The researchers originally found the twister ribozymes in Clostridia bacteria, but they have since identified them in many other bacteria and in some eukaryotes. They have found a total of almost 2,700 twister ribozymes so far. The ribozymes tend to be found in the same region of bacterial genomes as hammerhead ribozymes, suggesting that the two types of ribozymes may be functionally interchangeable.—CHA
FLUORINE CHEMISTS STRIKE AGAIN
NOVEMBER 25, 2013
VERMILION’S RED-TOGRAY TRANSFORMATION The use of powdered mercury sulfide, HgS, as a brilliant red pigment dates to ancient times in both Europe and Asia. But vermilion, as the pigment is known in Europe, turns gray or black over time. Various analyses have turned up several mercury compounds as possible degradation products, but scientists seeking to understand the causes of pigment darkening and ways to avoid it lacked a mechanism. By combining X-ray diffraction and theoretical studies, a team led by Fabiana Da Pieve of the Free University of Brussels, in Belgium, and Conor Hogan of Italy’s National Research Council now proposes a pathway for the darkening process (Phys. Rev. Lett. 2013, DOI: 10.1103/physrevlett.111.208302). They suggest that Cl– ions carried by water droplets in humid air adsorb onto the surface of HgS and form Hg3S2Cl2. Sulfur in Hg3S2Cl2 then reacts with O2 to form SO2, which escapes as a gas. Mercury atoms left behind form Hg34+ clusters that are stimulated by light to produce Hg and Hg2Cl2, which can liberate additional Hg. Hg is likely the source of the gray color, although
SCIENCE & TECHNOLOGY CONCENTRATES
to that escape artistry. According to a new report, however, mutations to just seven amino acids are the ones that truly mattered over a 35-year period (Science 2013, DOI: 10.1126/science.1244730). All seven of these amino acids are in hemagglutinin, a glycoprotein on the surface of the flu virus. Six of the seven align next to one another on the protein’s receptor binding site. Derek J. Smith of the University of Cambridge, Ron A. M. Fouchier of Erasmus Medical Center in the Netherlands, and colleagues made this discovery in the H3N2 flu subtype, which contributes to seasonal outbreaks. In strains that emerged between 1968 and 2003, five of the seven key amino acids were involved in the strain’s evolution more than once. “These findings have potentially far-reaching consequences for understanding the evolutionary mechanisms that govern influenza viruses,” the team writes.—CD
FREDERIK VANMEERT/U OF ANTWERP
kinson’s (see page 11), but scientists are also investigating naturally occurring substances as causative agents. A research team led by Joan W. Bennett and Jason R. Richardson of Rutgers University and Gary W. Miller of Emory University reports that a chemical commonly released by fungus causes Parkinson’s-like symptoms in fruit flies (Proc. Natl. Acad. Sci. USA 2013, DOI: 10.1073/pnas.1318830110). The compound, 1-octen-3-ol, is one of the volatiles responsible for mold’s characteristic odor. When the researchers exposed fruit flies to a low (0.5 ppm) dose of the chemical, the insects’ movements slowed, similar to Parkinson’s patients. In addition, dopamineproducing nerve OH cells in the flies’ brains died, another hallmark of the 1-Octen-3-ol neurodegenerative disease. The team proposes that 1-octen3-ol interferes with dopamine transport in the brain: The survival rate of flies with a faulty transport protein in their neurons dropped after exposure to the compound. The results suggest that regular exposure to chemicals emitted by mold—a common problem in water-damaged buildings— might have neurotoxic consequences, Bennett says.—LKW
additional experiments are necessary to confirm its presence, the researchers note.—JK
RNA CAN ADOPT CUBELIKE FOLD DNA at chromosome ends and other cellular locations can fold into cubelike conformations called G-quadruplexes, and these structures may play a role in cancer development. Researchers had proposed that RNA G-quadruplexes exist in cells as well, but evidence was scarce. Now, Shankar Balasubramanian of the University of Cambridge and coworkers have confirmed the presence of the RNA structures in cells by trapping them with G-quadruplex-specific antibodies (Nat. Chem. 2013, DOI: 10.1038/ nchem.1805). They used the antibodies to fluorescently label and image the RNA structures and identified small molecules that bind and sequester them. “Our findings provide substantive evidence for the presence of RNA G-quadruplex structures within the human transcriptome,” the team says. The biological function of these structures isn’t known yet, but the new study is an important first step toward being able to determine what role they play in cells.—SB
FLU HAS SEVEN GO-TO MUTATIONS
MOLD AS A PARKINSON’S RISK FACTOR
Every year brings a new version of the vaccine for seasonal flu, because the virus can mutate and evade antibodies already present in the body. It might seem as though scores of mutations have contributed
Because only a small number of genes have been solidly linked to Parkinson’s disease, researchers have been searching for environmental contaminants that might trigger the nervous system disorder. Man-made chemicals such as pesticides have been strongly associated with Par-
In this model, flu hemagglutinin is shown as a trimer (white, black, and gray). The receptor binding site is yellow, and the seven key amino acids are shown in red. CEN.ACS.ORG
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NOVEMBER 25, 2013
IF FOOL’S GOLD FAILS IN SOLAR CELLS, TRY ITS COUSIN
SCIENCE /A AAS
A paint chip from a 14th-century Spanish mural shows its original red vermilion layer topped with gray.
Pyrite, or iron sulfide, has proved to be fool’s gold for photovoltaics, failing to help solar cells reach theoretical predictions of 20% efficiency, the ratio of sunlight in to electricity out. Researchers could strike actual gold, however, with a cousin of pyrite, nanocrystalline Fe2GeS4 (J. Am. Chem. Soc. 2013, DOI: 10.1021/ja408333y). Previous theoretical work showed that not only would Fe2GeS4 readily absorb visible light, much like pyrite, but the germanium cousin would be more thermodynamically stable. To assess Fe2GeS4’s photovoltaic promise, Amy L. Prieto and Sarah J. Fredrick of Colorado State University synthesized Fe2GeS4 nanocrystals and used UV-visible spectrometry to find that they absorb visible light. From photoelectrochemical tests, the researchers found that when exposed to green light, thin films of Fe2GeS4 produce a modest current. Fe2GeS4 may be appealing to solar-cell makers because it’s chemically simpler and less expensive than other photovoltaic materials, the researchers suggest, though they haven’t yet determined the material’s optoelectronic properties. Devising ways to cut air exposure to reduce oxidation and tweaking film thickness should boost its current density, the researchers add.—PK
