Woolhouse 2008 Nat

Woolhouse 2008 Nat - NEWS & VIEWS different parts of a...

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different parts of a solid sample 5 . The authors turned to nanophysics for an answer to this problem 6,7 : specifically, the fact that a tiny crystal comparable in size to the wavelength of ultraviolet light (around 200–400 nano- metres) can provide an environment homo- geneous enough to minimize sample effects. Applying a technique developed by their own group 7 , they used an aqueous nanocrystalline suspension to trap all the photons from the ultraviolet light source. Taking their earlier measurements on a related solid ketone as a reference, they were able to calculate an accu- rate value for the quantum yield of their new reaction. That value was 3.3. For one photon to be activating more than one molecule (a quantum yield of 1.0), the reaction must be proceeding through a remarkable quantum chain pro cess 8 , with electronic excitations cycling through the crystal as bonds on different rings open and close. Any energy not used in the chain pro cess probably led to loss of the included water (the crystal was prepared as an aque- ous ‘mono hydrate’), the crumbling of the crystal, and recrystallization of the acetylene product. In 1959, in his famous talk ‘There’s plenty of room at the bottom’, Richard Feynman raised what was, in retrospect, an irresistible ques- tion 9 : “What would the properties of materials be if we could really arrange the atoms the way we want them?” Answers to this question can, and have, been sought in all states of matter — gas, liquid and solid. By effectively ‘spring- loading’ a molecule so that, when touched by light, it transferred its energy to a nearest neighbour, Kuzmanich et al. 3 establish a new connection between unimolecular and bimo- lecular reactivity. We can now start to wonder what further use we might make of the tech- nique; whether, for example, the signal ampli- fication provided by its domino-like behaviour might be useful for sensor-based materials and applications. With our rapidly growing knowledge of the structures and properties of organic solids 2 , Ruzicka’s morgue-like crystals will probably continue to reveal themselves as surprisingly lively places. Leonard R. MacGillivray is in the Department of Chemistry, University of Iowa, Iowa City, Iowa 52242, USA. e-mail: len-macgillivray@uiowa.edu 1. Dunitz, J. D., Schomaker, V. & Trueblood, K. N. J. Phys. Chem. 92, 856–867 (1988). 2. Desiraju, G. R. Angew. Chem. Int. Edn 46, 8342–8356 (2007). 3. Kuzmanich, G. et al. J. Am. Chem. Soc. 130, 1140–1141 (2008). 4. Choi, T., Peterfy, K., Khan, S. I. & Garcia-Garibay, M. A. J. Am. Chem. Soc. 118, 12477–12478 (1996). 5. Daglen, B. C., Harris, J. D., Dax, C. D. & Tyler, D. R. Rev. Sci. Instrum. 78, 074104 (2007). 6. Buc˘ar, D.-K. & MacGillivray, L. R. J. Am. Chem. Soc. 129, 32–33 (2007). 7. Veerman, M., Resendiz, M. J. E. & Garcia-Garibay, M. A. Org. Lett. 8, 2615–2617 (2006). 8. Gillmore, J. G. et al. Macromolecules 38, 7684–7694 (2005). 9. www.zyvex.com/nanotech/feynman.html EPIDEMIOLOGY Emerging diseases go global Mark E. J. Woolhouse Novel human infections continue to appear all over the world, but the risk is higher in some regions than others. Identification of emerging-disease ‘hotspots’ will help target surveillance work.
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