Science Concentrates MICROFLUIDICS FOOD SCIENCE
‘Guillotine’ slices cells in half
▸ Organic onions are richer in flavonoids
special to C&EN
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C&EN | CEN.ACS.ORG | JULY 3, 2017
The process of repairing wounds to individual cells isn’t well understood. What’s needed to improve that understanding is a method that can quickly damage many cells in a controlled way. To do this, Sindy K. Y. Tang of Stanford University and coworkers designed a microfluidic “guillotine” that slices single-cell organisms in half as they squeeze past a plastic blade (Proc. Natl. Acad. Sci. USA 2017, DOI: 10.1073/ pnas.1705059114). The researchers have tested the knifelike device on individual cells of the protozoan Stentor coeruleus, which are typically 100 to 200 µm wide but A microfluidic “guillotine” can stretch up to 1 mm. At slow flow rates, slices a single Stentor the knife tip cuts each cell into two approxcoeruleus cell in half as it imately equal pieces, which are shunted flows past the blade. into separate channels. Many of these cell pieces survive and regenerate within 24 to 48 hours. At higher flow rates, the knife ruptures the cell into multiple pieces, spilling the cell’s contents. Fewer of these cells survive. In both flow regimes, bits of cell membranes stick to the knife and clog up the device. The researchers find that encapsulating each cell in a water droplet cleans away the debris and increases the throughput. They were able to cut the cells at a rate of 64 cells per minute, which is more than 200 times as fast as manually cutting with a handheld needle. Such rapid wounding makes it possible to study cohorts of cells at the same stage of the repair process.—CELIA ARNAUD
PROCESS CHEMISTRY
anie.201704882). The synthetic route (shown) begins with lithiation of allene gas to produce allenyllithium, a compound so reactive that it’s usually made and used only at -78 °C. Such cryogenic conditions typically limit the use of allenyllithium. By using a continuous-flow process for the reaction, the chemists controlled the allene lithiation reaction so that they could use allenyllithium at about 0 °C. After lithiation, the compound undergoes transmetalation with zinc. The resulting intermediate is then used with a chiral (1S,2R)-N-pyrrolidinyl-norephedrine ligand to asymmetrically propargylate a β-amino aldehyde, producing the desired chiral homopropargyl β-amino alcohol.—BETHANY HALFORD
▸ Flow reaction tames allenyllithium When chemists at Pfizer were looking to make a chiral homopropargyl β-amino alcohol en route to one of their clinical candidates, they wanted to improve their six-step route. Teaming up with researchers at continuous-flow research firm Snapdragon Chemistry, led by Yuan-Qing Fang and Matthew M. Bio, they made the desired compound in just two steps from commercially available starting materials (Angew. Chem. Int. Ed. 2017, DOI: 10.1002/ O
H
H
H
H Allene
Li n-Hexyllithium
O
N H
H
O Chiral zinc complex
O O
N H
OH Chiral homopropargyl 𝝱-amino alcohol
C R E D I T: P RO C. NAT L . ACAD. S C I . USA ( GUI LLOTI NE ) ; S HU T T ERSTO C K ( ON I O N S )
Many shoppers believe organic vegetables are healthier than their conventionally grown counterparts. But previous studies of differences between the two types of produce have relied on vegetables bought off the shelf or have encompassed just a couple of years of side-by-side growth, making it difficult to rule out the effects of annual differences in weather or other factors. Researchers from the Teagasc Ashtown Food Research Centre have now compared organic and conventional cultivation of two varieties of onions grown in the same location over six seasons. They report that organic onions contain a significantly higher amount of two types of flavonoids, which are compounds that some studies have shown may protect against chronic health conditions such as cardiovascular Organically grown disease, diabetes, Red Baron onions and cancer (J. (shown) have Agric. Food Chem. higher levels of 2017, DOI: 10.1021/ flavonoids, on acs.jafc.7b01352). average, than Between 2009 and conventionally 2014, the team grown ones. grew Red Baron (red) and Hyskin (yellow) onions using both conventional cultivation, which includes the use of mineral fertilizers and synthetic pesticides, and European Union organic farming methods, which largely exclude those practices. They analyzed the compounds, including red anthocyanin flavonoids and the yellow flavonoid quercetin, in freeze-dried onion extracts using high-performance liquid chromatography and other techniques. Overall, the total flavonoid content was 10 to 50% higher by dry weight in the organic onions. The team attributes the flavonoid gap primarily to the differences in soil management and pest control. In organic farming, plants experience more stress, explains study author Dilip K. Rai, which prompts them to generate secondary metabolites such as flavonoids as a defense mechanism.—ALLA KATSNELSON,
