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Nature press release for 21 June issue

June 21, 2001

[411924] CHEMISTRY: BEADY WHEN WET (pp924-927; N&V)
French physicists Pascale Aussillous and David Quéré of the Colle'ge de France in Paris show this week how to move a liquid across a surface without wetting it. By coating water droplets with a fine powder, the researchers turn them into tiny beads that roll over glass without sticking or leaving any trace. These ‘liquid marbles’ behave less like liquids and more like soft solids — as if made from very squishy rubber.
The researchers think their non-stick droplets could find a variety of technological uses. They experience so little friction that very small forces induce motion. This might be useful in the emerging technology of microfluidics, where tiny quantities of liquid are shunted around on a surface such as a silicon chip for chemical or biological analysis.
To stop the droplets from sticking to the surface or merging with one another, Aussillous and Quéré give them a non-stick coat made from water-repelling powder. Droplets of powder-coated water a millimetre or so across form into nearly perfect spheres that sit on top of glass. Normal water droplets form a lens shape because of water’s attraction to glass.
In an accompanying News and Views article, L. Mahadevan of the University of Cambridge, UK, discusses the background and implications of this work.
CONTACT:
David Quere tel +33 1 44 27 10 66, e-mail quere@ext.jussieu.fr
L. Mahadevan e-mail l.mahadevan@damtp.cam.ac.uk

[411908] LIFELINES: FLIES TURN THEIR NOSES UP AT HEARING (p908)
Researchers have found that the fruitfly Drosophila melanogaster switches its ears on with an ingenious lock-and-key mechanism. The third segment of the fly’s antenna rotates in response to sound, such as the courtship song of another fruitfly, causing a hook on this segment to lock into a pit on the second segment.
Vibrations of this hook then activate the auditory receptors attached to its sides. In a Brief Communication, Martin Göpfert and Daniel Robert of the University of Zurich, Switzerland, describe how this rotational mechanism allows the fly to avoid mixing up hearing and smelling (the third antennal segment is also packed with olfactory sensors). “Flies did not turn their nose into an ear, they turn their nose to hear,” they conclude.
CONTACT:
Martin Göpfert tel +41 1 635 4820, e-mail mgoepfer@zool.unizh.ch

[411909] LIFELINES: SUN TRAP STRUCTURE (pp909-917; N&V)
This week, the crystal structure of photosystem I — part of the photosynthetic apparatus of all plants and many bacteria — at 2.5 Ã resolution reveals how an extensive array of antenna chlorophylls harnesses solar energy.
Photosystem I is a large photosynthetic assembly of membrane proteins and other factors. Petra Fromme of the Technical University of Berlin, Germany, and colleagues have solved its structure after decades of painstaking work, during which the group perfected the biochemical preparation of the complex and the quality of its crystals.
Photosystems come in two different but related forms: type I and type II. The most ancient and primitive photosynthetic bacteria have one or the other. Both are found in plants and cyanobacteria, where, in sequence, they convert solar into chemical energy. Photosystems use the excitation energy of sunlight, absorbed by chlorophyll, to extract electrons from a substrate and push them through the membrane in which the photosystems sit, creating an electrochemical gradient across the membrane. The gradient powers the production of the energy-storing molecule ATP.
“The structure reveals photosystem I to be a bewilderingly complex assembly”, says Werner Kühlbrandt of the Max Planck Institute of Biophysics, Frankfurt am Main, Germany, in an accompanying News and Views article. Kühlbrandt explains what this and other recent structures tell us about “the biosynthesis of nearly all organic matter on our planet”.
CONTACT:
Petra Fromme tel +49 30 314 264 03, e-mail fromme@phosis1.chem.tu-berlin.de
Werner Kühlbrandt tel +49 69 9676 9399, e-mail werner.kuehlbrandt@mpibp-frankfurt.mpg.de

[411927] EARTH: FLOW SLOW FROM THE NORTH (pp927-930)
The flow of water from the depths of the Nordic seas into the Atlantic Ocean may have decreased by at least 20% since 1950, report Bogi Hansen of the Faroese Fisheries Laboratory, T'³rshavn, Faroe Islands, and colleagues in this week’s Nature. The implications of the observed decrease depend on the behaviour of other overflow sources. But if not counteracted by an increased flow from elsewhere, the fall could lead to a reduced inflow into the deep Atlantic Ocean of a similar magnitude.
        Given that the heat transported by the Atlantic Ocean circulation gives rise to the exceptionally mild climate of northwestern Europe, the trend could have profound implications for European climate if it continues.
CONTACT:
Bogi Hansen tel +298 315092, e-mail bogihan@frs.fo

[411937] EVOLUTION: LICHEN IT OR NOT (pp937-940)
A lichen is a symbiosis between a fungus and a green alga or a bacterium or both. Lichens may have been around for longer than we thought, and consequently may have played a bigger role in the evolution of the fungi around us today.
So say Fran'§ois Lutzoni of The Field Museum of Natural History, Chicago, Illinois, and colleagues in this week’s Nature. Their analysis of a phylum that includes more than 98% of all known lichens shows that many major fungal lineages — including several of medical and industrial importance — were once lichens but have since gone it alone.
CONTACT:
Francois Lutzoni (until 18 June) tel +1 312 665 7857, e-mail flutzoni@fmnh.org
Mark Pagel (co-author) tel +44 118 931 8900, e-mail m.pagel@rdg.ac.uk

[411969] LIFELINES: CHECKPOINT CHECK (pp969-974)
Cells proceed with caution. If they detect damage to themselves, they pull over for repairs before going on to the next stage in their division cycle. Researchers have now discovered a link between two of the key players in this fail-safe mechanism.
Ultraviolet light, ionizing radiation and a variety of chemicals damage DNA, breaking either or both of its strands. When a cell senses this damage, either of two related molecules known as ATR and ATM, which perform many tasks in the cell’s damage-repair network, springs into action.
Working with human cell cultures, Xiao-Fan Wang and colleagues of the Duke University Medical Center, Durham, North Carolina, have found that one of the functions of ATM and ATR is to activate another protein called human Rad17. hRad17 then seems to load yet another set of proteins onto the damaged DNA strand to begin the repair process.
Malfunctions in DNA repair are involved in many cancers, and there is a rare and fatal genetic disorder involving mutations to the ATM gene — sufferers have immune deficiencies and a high rate of cancer. A better understanding of the checkpoints that prevent damaged cells from dividing could lead to better models, and eventually new therapies, for cancer.
CONTACT:
Xiao-Fan Wang tel +1 919 681 4861, e-mail wang0011@mc.duke.edu

[411934] EARTH: SIMULATIONS TAKE ON MANTLE (pp934-937)
The temperature contrast between the coldest and hottest regions of the Earth’s mantle at a given depth turn out to be surprisingly large — about 800 K at 1,000 km deep, 1,500 K at 200 km deep and possibly over 2,000 K at the core–mantle boundary. So conclude Artem R. Oganov and colleagues of University College London, from comparing computer simulations of the elastic properties of the major mineral of the lower mantle, MgSiO3 (perovskite), to seismic images of the Earth’s mantle.
Reported in this week’s Nature, the state of the art ‘finite temperature ab initio molecular dynamics’ simulations suggest that the lower mantle is either non-elastic or compositionally heterogeneous on large scales. This study also highlights the potential of simulation technology for solving geologically important problems.
CONTACT:
Artem R Oganov tel +44 20 7679 3344, mobile 07950 872637 e-mail a.oganov@ucl.ac.uk

[411940] LIFELINES: HUMAN GENOME DEBUGGED (pp940-944)
A dispute over whether bacterial genes have been transferred directly to humans is laid to rest in this week’s Nature.
Numerous genes in the recently published human genome were found to be highly similar to bacterial genes, leading to the claim that they got there by ‘horizontal transfer’.
This interpretation is now firmly refuted by Michael Stanhope, James R Brown, and colleagues of GlaxoSmithKline in Pennsylvania, who, by drawing up evolutionary trees, have shown that the presence of such genes can actually be explained by descent through common ancestors.
Their findings should settle the score for evolutionary biologists disgruntled at the initial report, and reassure those concerned about horizontal gene transfers from genetically modified organisms, for which the team’s research finds no evidence. “It’s a very important scientific and public information record to set straight,” says Stanhope.
CONTACT
Michael Stanhope tel +1 610 917 6577, e-mail Michael_J_Stanhope@sbphrd.com
James R Brown tel +1 610 917 6374 , e-mail James_R_Brown@sbphrd.com

[411944] EVOLUTION: COLOUR HAS DEEP IMPACT ON SEX (pp944-948; N&V)
This week, Janette Wenrick Boughman of the University of British Columbia, Vancouver, Canada, shows how sexual selection can drive speciation. Speciation occurs when organisms diverge such that cross-breeding cannot produce viable offspring, thus they constitute different species. Sexual selection occurs when female preference for certain male mate attributes promotes the evolution of specific male traits in appearance and courtship behaviour.
Boughman’s study of sticklebacks in the Canadian lakes charts the complex interplay between ambient light levels at different depths of the lakes, male coloration and female sensitivity to light in different regions of the spectrum. Although cause and effect are not yet clear, she finds that male sticklebacks appear redder in habitats with less red light, that females in areas with less red light are more sensitive to it, and that male colouring matches female sensitivity.
“All in all, sticklebacks may be outstanding subjects for investigating the general biology of speciation,” says Michael J. Ryan of the University of Texas, Austin, in an accompanying News and Views article that outlines the background and implications of this work.
CONTACT:
Janette Wenrick Boughman tel +1 604 822 5966, e-mail boughman@zoology.ubc.ca
Michael J. Ryan tel +1 512 471 5078, e-mail mryan@mail.utexas.edu

[411948] LIFELINES: ON THE nod (pp948-950)
The symbiosis between legumes and nitrogen-fixing rhizobium bacteria is of immense agronomic and ecological importance, and is a major contributor to the global nitrogen cycle. Until now only members of the alpha subclass of Proteobacteria have been shown to enter into this symbiotic relationship.
        Now Catherine Boivin-Masson and colleagues of the Laboratoire des Symbioses Tropicales et Méditerranéennes, Montpellier, France, have isolateed a member of the beta subclass that nodulates tropical legumes. The Burkholderia sp. organism harbours the nod genes that are essential to rhizobial symbiosis. The possibility that this form of nitrogen fixation may be more widely distributed in bacteria than previously thought suggests that beneficial symbioses could be engineered for agriculturally important plant–microbe pairings.
CONTACT:
Catherine Boivin-Masson tel +33 4 67 59 38 24, e-mail catherine.boivin@mpl.ird.fr

[411950] BRAIN: NEW SITE FOR SPACE CENTRE (pp950-953; N&V)
The seat of spatial awareness may not be where we thought, Hans-Otto Karnath and colleagues of the University of Tübingen, Germany, report in this week’s Nature. Contrary to the widely held, century-old view that the posterior parietal lobe mediates our interaction with the space around our bodies, Karnath’s team has collected evidence that in humans, as in monkeys, the superior temporal cortex is where notions of space reside.
        The researchers studied stroke patients with ‘pure’ spatial neglect — as damaged spatial awareness is known. Patients in previous studies often showed visual, cognitive and spatial defects rather than neglect alone. Karnath’s patients behaved as though part of the space surrounding them had ceased to exist — often shaving or drawing only one side of their faces, for example. The common site of injury turned out to be the superior temporal cortex.
“The classical finding that parietal damage causes hemispatial neglect in humans was ripe for re-examination,” says Michael S. A. Graziano of Princeton University, New Jersey, in an accompanying News and Views article. Although he points out that “the assignment of particular functions to specific brain regions can only be taken so far”.
CONTACT:
Hans-Otto Karnath tel +49 7071 29 80465, e-mail karnath@uni-tuebingen.de
Michael S. A. Graziano tel +1 609 258 4890, e-mail graziano@princeton.edu

[411907] …AND FINALLY: SIX DEGREES OF COPULATION (pp907-908)
The web of human sexual contacts is a small-world network — at least in Sweden. On account of the few people who have had an unusually large number of sex partners, most people are no more than a few degrees of, ahem, separation from each other.
It is these well-connected individuals who should be targeted in health-education campaigns, say Frederik Liljeros, of Stockholm University, Sweden, and colleagues in a Brief Communication, as they are the ‘vulnerable nodes’ in the network — the consequences will probably be more widespread should they contract a sexually transmitted disease. The researchers built their model on the basis of questionnaires from 2,810 individuals describing their sexual behaviour.
CONTACT:
Luis Amaral (co-author) tel +1 617 353 3891 / 8000 , e-mail amaral@buphy.bu.edu


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