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18 August 2012 | NewScientist | 17 DNA Trojan horse outwits cancer IT WORKED for the ancient Greeks, so why shouldn’t it work for us? Some cancers are resistant to chemotherapy, but we can attack them successfully by hiding drugs inside folded-up DNA. DNA origami involves folding a single strand of DNA into a complex pattern, creating a 3D structure. Baoquan Ding at the National Center for Nanoscience and Technology in Beijing, China, and colleagues loaded a tubular piece of folded DNA with doxorubicin, a chemotherapy drug. The DNA Trojan horse delivered a dose of the drug that proved lethal to human breast- cancer cells, even though they had developed resistance to doxorubicin (Journal of the American Chemical Society, DOI: 10.1021/ja304263n). “This is the first study to demonstrate that DNA origami can be used to circumvent drug resistance,” says Hao Yan at Arizona State University in Tempe, who jointly led the work. The cancer cells may not recognise the DNA origami as a threat in the way that free doxorubicin is, he suggests. The folded DNA might also alter the pH inside the cells, increasing the drug’s activity. Colliding black holes leave their imprint in space-time ripples DID monster black holes pull the first galaxies together, or were they born inside those galaxies? It’s a long-standing mystery. Now a new analysis of the gravitational ripples from colliding black holes could reveal the answer by helping astronomers reconstruct a crash rather than just surveying its aftermath. Most large galaxies we see have supermassive black holes at their centres. When these galaxies collide, their black holes merge into one even more massive beast, according to theory. Observations of the final black hole yield no information about the original black holes, however. So astronomers have been trying to look for gravitational waves. General relativity predicts that colliding black holes should emit such ripples in the fabric of space-time, including a wave called the ringdown that contains information about the final black hole’s mass and spin. Now computer simulations led by Ioannis Kamaretsos of the University of Cardiff, UK, show that the ringdown can also tell us HIGH-TECH cameras such as those that use thermal imaging can reveal anomalies on a landscape, such as patches of forest infected with a pathogen. Now they could be used to help identify skin problems. Doctors usually diagnose psoriasis by visually assessing how much skin is covered in lesions, as well as how reddened, thickened and scaly it has become. Such observations are highly subjective, so Francisco Tausk, at the University of Rochester, teamed up with colleagues at the Rochester Institute of Technology, both in New York, to find out whether imaging technology might be more accurate. In preliminary trials, thermal cameras proved adept at quantifying redness because the increased circulation underneath skin lesions makes them warmer (see image). Photographing skin under ultraviolet light highlighted hard plaques, which the researchers say contain an amino acid that may fluoresce. Both approaches picked out areas of skin that looked normal to the eye, suggesting they may be able to predict where lesions will develop. The team is now seeking funding for a clinical trial. Imaging catches psoriasis red-handed CHRISTYE SISSON/ROCHESTER INSTITUTE OF TECHNOLOGY the masses and spins of the two original black holes (arxiv.org/ abs/1207.0399). Some theories say the gravity of nascent black holes pulled matter together to form the first galaxies, but it remains unclear if the earliest black holes were massive enough to do this. By applying the new analysis to observations of the early universe, we might be able to settle that question at last. Although nobody has detected gravitational waves as yet, next- generation observatories may spot them within a few years. Corona mystery thrown for a loop THE surface of the sun is a pretty cool place. At least when you compare it with the corona, the sun’s upper atmosphere, which is nearly 400 times hotter. This huge temperature difference has long been a mystery, but a newly discovered feature of the sun’s magnetic field may help us get to the bottom of things. The sun’s tangled magnetic field includes huge loops that arch from the surface into the corona. We can see the loops because bright surface plasma flows along their curves. Richard Frazin at the University of Michigan, Ann Arbor, and his team were measuring the temperature of coronal loops during a solar minimum, a quiet phase which sees fewer sunspots and flares. They expected all loops to get hotter with height, since that was the case in measurements taken during more active phases. Surprisingly, some of the loops nearest the sun’s equator got colder near their tops. Frazin thinks these newly found “down loops” exist throughout the solar cycle and may be a symptom of whatever causes coronal heating (The Astrophysical Journal, DOI: 10.1088/0004- 637x/755/2/86). Clare Parnell at the University of St Andrews, UK, agrees that down loops are a new factor that any solar- heating model will need to include. GODDARD SPACE FLIGHT CENTRE/NASA For new stories every day, visit newscientist.com/news
