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of using different pathways, and scrutinized the elements europium, samarium and neodymium. The team was able to count the fraction of isotopes of each element, concluding that one process dominated in one star and the alternative in the other star.

While not surprising, the finding happily suggests that scientists’ understanding of nucleosynthesis “is not wildly mistaken”, the authors write.

ANIMAL BEHAVIOUR

Coming out of their shellsProc. R. Soc. Lond. B doi:10.1098/rspb.2008.0025 (2008)Mark Briffa and colleagues at the University of Plymouth, UK, have detected the first signs of personality among crustaceans.

Briffa’s team devised a new statistical method to differentiate between natural variability in responses of individual European hermit crabs (Pagurus bernhardus, pictured right) to different situations, and a consistent trend in responses that reflects a ‘personality’.

P. bernhardus retreats into its commandeered shell at any sign of danger. The team timed how long crabs took to re-emerge from their shells in a variety of situations. Some bold crabs consistently emerged sooner than others.

NANOTECHNOLOGY

Cells on a rollNano Lett. doi:10.1021/nl073322a (2008)Sorting cells in the lab generally means labelling them with chemicals and using expensive cell-sorting equipment. Robert Langer and collaborators at the Massachusetts Institute of Technology have instead capitalized on the natural proclivity of some cells to roll along surfaces, including the insides of blood vessels, to sort them. On coating part of a flow chamber with a ligand called P-selectin, Langer and his colleagues found that cells with the right receptors rolled with the flow until they reached the edge of the coating. The cells then continued to roll along this edge, diverting from the direction of flow at angles of up to 8.6°.

ECOLOGY

Egregious edge effectsProc. Natl Acad. Sci. USA doi:10.1073/pnas.0800460105 (2008)How wide is a forest edge? For a fifth of the beetle species found in New Zealand, ‘edge effects’ — the suite of differences that

characterize the fringes of a forest fragment, including increased light and wind — influence the abundance of species more than 250 metres inside the boundary of the forest.

Robert Ewers of Imperial College London and Raphael Didham of the University of Canterbury, Christchurch, New Zealand, also found that edge effects penetrated a full kilometre into the forest for one in eight of a number of common beetle species, a much greater distance than previously reported for invertebrates.

CHEMISTRY

Cobalt couplingJ. Am. Chem. Soc. doi:10.1021/ja800738d (2008)Chemists have found a new way to carry out the most basic, but often the most challenging, of chemical reactions — making carbon–carbon bonds. Robert Bergman and his colleagues at the University of California, Berkeley, have developed a nitrogen-containing cobalt reaction system that makes otherwise docile carbon–hydrogen bonds reactive. Cobalt-containing molecules are first reacted with nitric oxide. The resulting complex holds on to a target molecule — a simple alkene with a carbon–hydrogen bond — while this reacts with another similar alkene. The two molecules become joined by a brand new carbon–carbon bond. Chemists trying to make complex drug molecules now have another trick to try.

Masayuki InoueGraduate School of Pharmaceutical Sciences, University of Tokyo, Japan

A synthetic chemist takes inspiration from sketching structures.

I enjoy drawing chemical structures of complex natural products and imagining how their polar functional groups, such as –OH and –NH2, interact with biopolymers. I usually first draw a carbon framework of the molecule on paper and then add the required groups. Of course, this order of ‘functionalizations’ has almost nothing to do with any synthetic scheme I might use for that molecule. Tedious multi-step manipulations are often needed just to introduce one oxygen or nitrogen. Making a molecule will never be as easy as drawing one.

Many research groups are trying to make it easier by devising one-step introductions of complete polar groups into carbon frameworks. One of the latest examples comes from Mark Chen and Christina White (Science, 318, 783–787; 2007). They used a new iron catalyst and hydrogen peroxide to convert specific hydrogens to hydroxyl groups on the carbon skeletons of a variety of molecules.

The catalyst seems to be able to differentiate a site of functionalization from other potentially oxidizable C–H bonds by the balance of two factors: electron-richness and steric accessibility of the bond. Chen and White were able to oxidize the antimalarial natural product (+)-artemisinin at just one predicted position to produce (+)-10β-hydroxyartemisinin. Their work represents a definite advance in the direct functionalization of carbon skeletons.

Every chemist dreams about placing functional groups anywhere they want as easily as drawing them on paper. The direct C–H oxidation reaction should allow us to perform such manipulations and holds great promise for simplifying the synthesis of complex molecules.

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NATURE|Vol 452|20 March 2008 RESEARCH HIGHLIGHTS

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