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Vol 450|1 November 2007 RESEARCH HIGHLIGHTS MOLECULAR NEUROBIOLOGY Active resilience Extraordinary sound Cell 131, 391–404 (2007) A molecule known as BDNF may provide Nature Phys. doi:10.1038/nphys774 a pivotal distinction between people who (2007) succumb to conditions such as depression Light squeezed through a hole or post-traumatic stress disorder and the of smaller diameter than its majority who do not. wavelength can emerge in a Eric Nestler of the University of Texas collimated beam when the Southwestern Medical Center in Dallas and hole is set in a periodic array his colleagues had previously identified mice of indentations. This counter- that avoided social contact with cage-mates intuitive phenomenon is known after repeated ‘social defeat’ — brought as “extraordinary optical transmission”. Now researchers about by forced encounters with more in Spain have shown that an aggressive mice. analogous effect can be achieved The researchers found that resilience with sound waves. to stress in this social-defeat model is an Using their understanding of active process in which stress-induced firing the role of surface plasmons in the in part of the brain’s neuronal circuitry optical case, Francisco Garcia-Vidal associated with reward and drug addiction at the Autonomous University is suppressed. This lowers levels of brain- of Madrid and his colleagues derived neurotrophic factor (BDNF), and designed systems of holes and mice with a natural variation in their BDNF grooves in which acoustic surface gene were resilient to stress. The researchers waves have a similar effect, also found high levels of BDNF in a region producing a beam of sound through associated with reward in post-mortem cunningly contrived interference brains of people with a history of depression. and reinforcement. The authors think this effect might be applied in ECOLOGY non-destructive materials testing Smelly fish and medical ultrasound. Proc. R. Soc. B doi:10.1098/rspb.2007.1283 (2007) Fish that have been exposed to even very MICROBIOLOGY Institue of Technology in Pasadena, Ron low levels of a common pollutant are Weiss at Princeton University, New Jersey, shunned by their conspecifics, according to A time to die and their colleagues report engineering research by Ashley Ward at the University Science 318, 652–655 (2007); Proc. Natl Acad. Sci. a system into populations of E. coli that of Sydney and his co-workers. The effect USA doi:10.1073/pnas.0704256104 (2007) allows a specific pattern of gene expression may put the tainted fish at increased risk of Bacteria communicate with each other to a only when both populations are present in predation. greater extent, and in more ways, than was sufficient numbers. They suggest that such The research looks at the effect of low levels once thought. Hanna Engelberg-Kulka of systems could be used to engineer specific of 4-nonylphenol, a surfactant sometimes the Hebrew University in Jerusalem and her responses in artificial biofilms. found in shampoos and soaps, on schooling colleagues report that Escherichia coli can send Intriguingly, three years ago these labs in juvenile banded killifish (Fundulus out messages that encourage their neighbours engineered a ‘neighbour killing’ system diaphanous, pictured below). Unexposed fish to kill themselves. The ‘extracellular death into bacteria quite similar to that now being were unwilling to school with fish that had factor’ involved turns out to be a chain of five reported (L. You et al. Nature 428, 868–871; been exposed for as little as an hour to levels amino acids that seems to be produced by the 2004). This may be the first example of G. MESZAROS/VISUALS UNLIMITED G. MESZAROS/VISUALS commonly found in sewage outflows. degradation of a metabolic enzyme, glucose-6- synthetic biology anticipating a function only phosphate dehydrogenase. later revealed in nature. The authors suggest that the ability to RELATIVISTIC PHYSICS coordinate cell death may allow bacteria to Hot at any speed release nutrients from a Phys. Rev. Lett. 99, 170601 (2007) proportion of individuals According to the theory of special relativity, when the population is measurements of length and time differ under stress, or to defeat depending on the relative velocity of the phage attacks by means observer and the thing being measured. similar to a ‘scorched- Einstein and other prominent physicists earth’ policy. believed that the measured temperature of Meanwhile, Frances a gas would also depend on the speed of the Arnold at the California observer. 4 NATURE|Vol 450|1 November 2007 RESEARCH HIGHLIGHTS JOURNAL CLUB James E. Ferrell Stanford University School of Medicine, California, USA Work by Peter Hänggi of the University PLANETARY SCIENCE A systems biologist encourages of Augsburg in Germany and his modelling by the millions. collaborators contradicts those early Identical twins calculations. The group’s one-dimensional Astrophys J. 669, L89–L92 (2007) In a typical modelling study, we models of particles in a gas show that the Astronomers have identified a star that is in write down equations, solve them, same temperature will be observed regardless many ways indistinguishable from the Sun. and see whether they account for of the observer’s speed. The team admits, Peruvian astronomers Jorge Meléndez of known data. If they do, we claim however, that this may not be true of two- or the Australian National University, and Iván to understand some bit of biology. three-dimensional gases, and believes that Ramírez at the McDonald Observatory of the One huge caveat is that many other further study is needed. University of Texas in Austin report that the models might have matched the parameters of HIP 56948, one of four ‘solar data just as well. CLIMATE CHANGE twins’ they have been studying, are exactly Researchers from Peking the same as the Sun’s, within the constraints University in Beijing and the Irreducible sensitivity of observational accuracy. Unlike previous University of California, Science 318, 629–632; 582–583 (2007) solar twins, this star — which resides 200 San Francisco, have devised a Decades of intensive work on climate change satisfying way of dealing with this have done little to narrow the range of problem (W. Ma et al. Mol. Syst. uncertainty over Earth’s climate sensitivity Biol. 2, 70; 2006). — the amount of global warming to be Their starting point was epithelial expected under carbon dioxide levels twice patterning in the fruitfly Drosophila. those of the pre-industrial world, which During embryogenesis, a system the Intergovernmental Panel on Climate known as the ‘segment polarity Change puts at between 2 °C and 4.5 °C. network’ generates repeating stripes Nor can a substantially better estimate be of gene expression. The stripes are expected in the future, according to Gerard initially fuzzy and later become Roe and Marcia Baker of the University of sharp. Ma et al. set out to see what Washington in Seattle. simple gene circuits were best suited Their mathematical analysis stresses to this sharpening process. that normally distributed uncertainties They formulated differential- in the feedbacks associated with climate equation models for about 14 million processes make ruling out a long tail of high ways of connecting two or three sensitivities unrealistic. In an accompanying light years away in the constellation of Draco segmentation genes, then randomly Perspective, Myles Allen and David Frame — shares the Sun’s low lithium content. In chose 100 sets of parameters at the University of Oxford, UK, argue that addition, HIP 56948, like the Sun, has no that defined the strength of the this is not a problem for setting policy, accompanying ‘hot Jupiter’ in close orbit. interactions for each gene. They because the concentrations of carbon dioxide Such solar twins are useful for various S. MCCARTNEY/SPL then carried out computations for associated with specific warmings can be calibrations, the authors say; they are also of each combination to determine much better constrained. potential interest to researchers involved in which of them converted fuzzy the search for extraterrestrial intelligence. stripes into sharp ones. CHEMISTRY Many topologies worked for at CHEMICAL PHYSICS least one parameter set. But only Clicking without copper a fraction worked for more than Proc. Natl Acad. Sci. USA 104, 16793–16797 (2007) Nano steams ahead one or two. Interestingly, the most Proteins can be quite easily labelled for Phys. Rev. Lett. doi:10.1103/PhysRevLett.99.178103 robust topologies were all variations studies in living cells, but other types of (2007) on the same design — each had molecule are trickier to track. One possibility Nanoparticles may exhibit chemotaxis three sub-circuits, one ‘stripe is to use a two-step technique: first get the — directed motion along a gradient of generator’ motif and two bistable cell’s own machinery to add a chemical chemical concentration previously seen at the ‘response sharpeners’. These ‘socket’ to the molecule of interest, then add microscale only for living cells. findings give hope that complex a trackable reagent that fits easily into that Ayusman Sen, Darrell Velegol and their networks may be decomposed socket. ‘Click’ chemistry — so named for the colleagues at Pennsylvania State University into modular sub-circuits with ease of assembly — might be helpful for this have shown previously that nanorods made understandable functions. second step, but normally depends on toxic with platinum at one end and gold at the Comprehensively examining copper compounds. other move through a solution of hydrogen millions of models is a lot of Now Carolyn Bertozzi and her colleagues peroxide, owing to the catalytic production work, but is not impossible. And, at the University of California, Berkeley, of oxygen gas. Now they report that in a as Ma et al. show, it can yield report using a cyclooctyne onto which peroxide gradient the rods — 370 nm wide important insight that could not fluorine atoms have been added to carry out and 2 μm long — move ‘uphill’ towards the have been derived from studies of the same sort of click reaction without the fuel source, because the increase in speed at one or two.

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