SCIENCE & TECHNOLOGY CONCENTRATES
IMMUNE CELLS AND FLU SHOT REACTIONS
REMOTELY CHIRAL AMINES
Some people end up feeling crappy after a flu shot, some don’t. Researchers have found a link between complaints of shortterm aches and fever after a flu injection and inherent elevated levels of a type of immune cell in those people’s bodies (Nat. Immunol. 2016, DOI: 10.1038/ni.3328). This unexpected immunological discovery, from an international team led by Adrian C. Hayday of King’s College London, carries important implications for understanding postimmunization adverse reactions. The immune cells, known as transitional B cells, produce antibodies and are also associated with some autoimmune diseases, suggesting that people who experience adverse reactions to flu shots may be more at risk for developing autoimmune diseases later in life. The new knowledge could also be important for cancer patients receiving immunotherapy, Hayday tells C&EN. The team injected 178 healthy volunteers with the UK H1N1 Pandremix vaccine, which protects against the swine flu responsible for an outbreak in 2009. In addition to the B-cell discovery, the researchers also gained insight into the role of vaccine adjuvants. Many vaccines, including Pandremix, contain adjuvants to boost efficacy, but their mechanisms of action have remained unclear. Within 24 hours of receiving the H1N1 vaccine, the volunteers’ bodies produced a burst of lymphocytes, a process that may have been boosted by the adjuvant.—EKW
Amines with stereocenters three OR R´´ R1 R2 N or four carbon atoms from the + R´ amine nitrogen atom, called γOBz and δ-chiral amines, are imporLigand–CuH Reductive relay hydroamination tant structural features in many drugs and natural products. So NR1R2 A single-step reductive R´´ it would be nice if they were easy relay hydroamination to make. But chemists have not converts allylic R´ starting materials been able to controllably add to γ-chiral amines, OR = alcohol, ester, or amines and other functional 1 2 ether; R´, R´´, R , and R = in which the chiral groups to positions more than various organic groups; center is remote from and Bz = benzoyl one or two carbons from chiral the amine C–N bond. centers without resorting to multistep procedures. Stephen L. Buchwald of Massachusetts Institute of Technology and coworkers have now devised a single-step reaction that creates γ-chiral amines from allylic alcohols, allylic esters, and allylic ethers and makes δ-chiral amines from allylic epoxides (Nat. Chem. 2016, DOI: 10.1038/nchem.2418). The reaction can also be used to sequentially aminate substrates with more than one allylic group. The copper hydridecatalyzed procedure, which the MIT researchers call reductive relay hydroamination, works by installing an amino group three or four carbon atoms from one of the allylic starting material’s double-bonded carbons, which is converted to a chiral center as part of the reaction.—SB
Type 2 diabetics who take chromium supplements to increase the sensitivity of their cells to insulin may want to rethink the practice. A study has found that in cells the Cr(III) in the compounds is oxidized to Cr(V) and Cr(VI), forms of chromium that are known to be toxic (Angew. Chem. Int. Ed. 2016, DOI: 10.1002/ anie.201509065). Researchers led by Peter A. Lay of the University of Sydney previously proposed that Cr(III) supplements enhance insulin sensitivity in diabetics because the chromium is oxidized, but they had not proven that the problematic forms were found in cells. Working in mice adipose cells treated with Cr(III), Lay’s team used microfocus X-ray absorption near-edge structure, or µ-XANES,
ANGEW. CHEM. INT. ED.
CHROMIUM THERAPY FOR DIABETICS IS RISKY
analysis to show that Cr(III), Cr(V), and Cr(VI) were all unambiguously present in the cells. They propose that the unfortunate oxidation can take place in a cell’s When adipose cells (top, showing phosphorus signal) are exposed to Cr(III), they oxidize the metal into Cr(V) and Cr(VI), creating chromium hot spots (arrows, bottom).
mostly reducing environment because cell signaling pathways, including those involved in insulin processing, often use hydrogen peroxide, a strong oxidizer. “In light of these findings, there is a need for epidemiological studies to ascertain whether Cr(III) supplements alter cancer risk,” the researchers note.—SE CEN.ACS.ORG
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PEROVSKITE SOLAR CELLS LOVE THE BLUES The efficiency with which silicon solar cells convert sunlight to electricity can be boosted by forming a tandem structure that couples a standard silicon cell with one based on a tailor-made perovskite compound, a study shows (Science 2016, DOI: 10.1126/science. aad5845). The aim in designing these tandem cells is to capture a broader portion of the solar spectrum by coupling two or more materials that absorb complementary wavelength regions. Researchers have tried altering the composition of perovskite-type metal halides to absorb light in the highenergy blue portion of the solar spectrum in order to pair the material with silicon, which absorbs lower-energy light. But the perovskites prepared thus far, most of which are related to methylammonium lead triiodide, decompose on prolonged exposure to light and heat. A team led by University of Oxford physicist Henry J. Snaith may have come up with a solution. The researchers report that [HC(NH2)2]0.83Cs0.17Pb(I0.6Br0.4)3 absorbs light strongly in the blue region and is highly stable. By combining that compound with a 19% efficient silicon cell, the researchers showed that they could produce
SCIENCE & TECHNOLOGY CONCENTRATES
a tandem cell with a conversion efficiency of more than 25%.—MJ
NEWLY ENGINEERED TISSUE SHEDS LIGHT ON FIBROCARTILAGE Fibrocartilage is a type of tissue, such as that in the knee meniscus, that consists of aligned fibrous microdomains with nonfibrous proteoglycan-rich microdomain inclusions. The role of these different domains in growth and development, aging, and disease is not well understood. Dawn M. Elliott of the University of Delaware, Robert L. Mauck of the University of Pennsylvania, and coworkers have now quantified the proteoglycan microdomains in knee fibrocartilage from fetal, juvenile, and adult cows and from adult humans and assessed the tissue’s response to strain (Nat. Mater. 2016, DOI: 10.1038/nmat4520). The number of proteoglycan microdomains reached a steady state
WOOJIN HAN AND SU CHIN HEO
Heterogeneous tissue-engineered constructs reproduce the microstructural, micromechanical, and mechanobiological features of natural fibrocartilage. This image shows interactions between fibrous (red) and proteoglycan-rich (blue) microdomains.
at the juvenile stage, they found, but the size of the proteoglycan domains continued to increase throughout aging. In humans, the size, but not the number, of inclusions correlated with age, body mass index, and diagnosis of osteoarthritis. The researchers separately engineered fibrocartilage by seeding cells on a polymer scaffold. One type of cell deposits the collagen matrix, and another type of cell deposits proteoglycans. The mechanical and signaling response of the engineered tissue to tensile strain matched that of the natural tissue. The engineered tissue thus provides a new tool for scientists to develop treatments for disease or injury, the researchers conclude.—CHA
INSOLUBLE CATALYST WORKS WONDERS A growing number of chemists are turning to water as an environmentally friendly
N
by-product of this degradation, magnesium hydroxide, spurs calcium phosphate formation near + the screw. This (pinacol)B–Si(CH3)2Ph Si(CH3)2Ph activity, in turn, O O helps induce R´ R R´ R bone growth, says R,R´= various groups, team member HyungPh = phenyl Seop Han of the Korea Institute of alternative to standard organic solvents— Science & Technology. The screws, which water is abundant, inexpensive, nonflamwere approved by the Korea Food & Drug mable, and nontoxic. In one example, Shū Administration in April, help fractures heal Kobayashi and coworkers at the University completely in about a year, he adds.—MD of Tokyo have been exploring the use of nonimmobilized chiral heterogeneous PLANT COMPOUND catalysts in water. Although the catalysts are insoluble in water, they nevertheless MIMICS BACTERIAL can mediate reactions between lipophilic COMMUNICATIONS reagents. The Tokyo researchers have now paired copper acetylacetonate with a chiral Bacteria often coordinate efforts chemibipyridine ligand for the enantioselective cally with their neighbors using a process addition of silylboronates to a range of α,βcalled quorum sensing. The microbes reunsaturated acceptor molecules (J. Am. lease molecules that they all recognize as Chem. Soc. 2015, DOI: 10.1021/jacs.5b11418). signals for common activities such as formThe products feature a chiral silyl group, ing a biofilm or releasing toxic virulence which is a convenient placeholder for a C–C factors to attack a host. A study has now or C–O bond that can be formed in later found that a compound made by plants, steps. The new reactions only proceed in rosmarinic acid, can mimic the actions of water and don’t work in organic solvents a common class of quorum-sensing molwhen the catalyst or reactants are soluble. ecules (Sci. Signaling 2016, DOI: 10.1126/ The team believes water plays a prominent scisignal.aaa8271). Plants may use rosmarole in constructing and stabilizing sterically rinic acid to protect themselves against confined, rigid transition states and accelerinfections by butting into bacterial converating subsequent protonation leading to the sations, a strategy scientists could adopt high yields and enantioselectivities.—SR in the design of new antimicrobial drugs. Through computational modeling and microcalorimetry experiments, Tino Krell of MAGNESIUM’S the Spanish National Research Council and colleagues found that rosmarinic acid can MEDICAL METTLE bind to a known quorum-sensing regulator Metal corrosion is usually a bad thing, protein used by the pathogenic bacteria but in some instances it can be beneficial, Pseudomonas aeruginosa. The compound is even therapeutic. For example, scientists more potent than the bacteria’s own quohave been developing biodegradable rum-sensing molecule, a homoserine lacmetal alloys that appear to promote healOH ing when used as replacements for conO OH OH ventional noncorrosive metal pins and O screws used to fix broken bones. A team of O South Korean and Canadian researchers has now shown how magnesium screws HO laced with calcium and zinc—elements OH known to promote bone health—help heal Rosmarinic acid small fractures in hands and wrists (Proc. Natl. Acad. Sci. USA 2016, DOI: 10.1073/ tone, binding tighter to the regulator and pnas.1518238113). Using a variety of techstimulating greater levels of gene expresniques, including fluorescence microscopy sion. The researchers think rosmarinic acid and energy-dispersive X-ray spectroscopy, makes bacteria vulnerable by forcing them the team tracked the water-driven degrato jump the gun on a sensing response bedation of screws inside patients at Ajou fore they have sufficient numbers to reach University Hospital for several months. A a quorum.—MT A water-insoluble chiral copper catalyst manages to orchestrate asymmetric silyl additions in water.
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Cu HO
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