Science Roundup

This week in Science Roundup:

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Energy and Sustainability
Special Online Collection: Sustainability and Energy

Against the backdrop of a global economy dependent on nonrenewable fossil fuels that continue to be a major cause of pollution and climate change, finding sustainable alternatives is becoming increasingly urgent. In a special section of the 9 Feb 2007 issue, Science looked at the challenges of harnessing renewable energy more effectively and some of the people who are tackling these problems. An Editorial and a series of Perspectives discussed technological and policy issues relating to solar energy conversion, biofuel production, and carbon sequestration from sources of fossil fuel combustion. Meanwhile, News articles profiled national lab directors, computer modelers, captains of industry, and bench scientists working on projects ranging from using microbes to generate better biofuels to creating digital tools to test nuclear reactor designs. ScienceCareers.org profiled three young private-sector scientists who are on their first steps to careers in energy R&D. And a special podcast provided interviews on the state of science, funding, and policy in the sustainable-energy arena.


Medieval Quasicrystalline Tiling

Elaborate geometric mosaics are a distinctive feature of medieval Islamic architecture throughout the Middle East and Central Asia . Complex patterns called girih -- consisting of polygon and star shapes interlaced with zigzagging lines -- were thought to have been created with simple tools such as straightedges and compasses. Now, a Report by Lu and Steinhardt in the 23 Feb 2007 Science suggests that by the beginning of the 13th century, artisans began to create girih designs using a handful of decorated tile shapes including a decagon, pentagon, diamond, and bowtie. By laying the tiles edge-to-edge, the decorating lines connected to form a continuous network across the entire tiling. The team reports that the tilings became increasing complex and by the 15th century had evolved into complicated quasi-crystalline patterns, which are made up of finite units but never repeat. Interestingly, the mathematical underpinnings of these patterns -- which show five-fold and 10-fold rotational symmetry -- were not understood in the West until some 500 years later. An accompanying News story by J. Bohannon highlighted the study.


Logical Microfluidics

Microfluidics -- which deals with the behavior and control of micro- and nanoliter volumes of fluids -- has become a powerful technique for a wide variety of applications in biotechnology, engineering, physics, and chemistry. Now, two Reports in the 9 Feb 2007 Science describe the use of microfluidic technology to construct streams of droplets and bubbles that can encode and decode information or perform logical operations. Fuerstman et al. created a microfluidic device in which droplets of water-based ink in an organic solvent move through a channel that splits into two branches that reconnect downstream. The droplets must choose one branch or the other and the droplets in each branch influence the choice of subsequent droplets by modifying the rate of fluid flow through the channels. After the two streams recombine, the droplets take on a particular repeat pattern or encoding that can be decoded through a reversal of the fluid flow, without the need for valves or switches. Meanwhile, Prakash and Gershenfeld demonstrated bubble logic -- a new technology in which bubbles moving through microchannels represent bits of information similar to the ones and zeros used in digital computation ( see the related Science NOW story by P. Berardelli ). The team was able to create simple devices including AND, OR, and NOT gates, as well more complex arrangements capable of acting as counters, oscillators, or memory arrays. An accompanying Perspective by I. R. Epstein highlighted the studies.


Atoms in Motion

X-ray crystallography has long been used to gain detailed information on the atomic-scale structure of materials and molecules. But the structure of matter is not static, and developing our understanding of the fundamental behavior of matter requires structural measurements on the time scales on which matter moves -- on the order of picoseconds and femtoseconds. The recent advent of high-energy x-ray free-electron lasers (XFELs) has now opened up the possibility of watching matter move on both atomic length and time scales. Furthermore, ultrafast laser excitation can produce transient states of matter that would otherwise be inaccessible by laboratory investigation. In a study in the 2 Feb 2007 Science , Fritz et al. reported the use of ultrashort, ultrafast x-ray pulses from an XFEL to measure the dynamics of atomic vibrations in bismuth, a crystalline metal solid, when excited by photons. The team found that as the proportion of excited electrons increased, the bismuth atoms oscillated at decreasing frequency, corresponding to a softening of the material’s internal lattice structure. As noted in an accompanying Perspective by J. D. Brock the new measurements "provide researchers direct tests of calculations of highly excited electronic states and provide basic insights into our fundamental understanding of condensed matter."


Granite Origins

Granites -- coarsely crystalline, feldspar- and quartz-rich rocks formed from silicate melts -- make up a large part of the continental crust, and geologists have been arguing over their precise origins for centuries. One reason for the debate is the complexity of the rocks; many are composed of minerals that represent only a component of the melts from which they formed, whereas some are mixtures of minerals that grew from different melts and still others contain unmelted remnants of their sources. In a Report in the 16 Feb 2007 Science , Kemp et al. investigated the evolutionary history of granites by examining the chemistry of successive layers of zircon crystals -- a trace mineral common to most granites. The team measured oxygen and hafnium isotope compositions, which track melt history, from the classic granites of the Lachlan Fold Belt in eastern Australia . Their data indicate that these granites formed by the recycling of deep crustal rocks as mantle magma rose through them, rather than by the remelting of ancient, shallower crust, as was widely believed. An accompanying Perspective by J.M. Eiler notes that these results may force revisions of the geological histories of the many places where similar granites are found.


Explaining Supernova Rings

Stellar explosions known as supernovae can leave behind a variety of different objects including rapidly rotating pulsars, black holes, and curiously shaped nebulae (clouds of ejected dust and gas). On 23 February 1987 , the explosion of SN1987A -- a star about 20 times as massive as the sun -- could be seen with the naked eye, and it illuminated an unusual triple-ring nebula surrounding the supernova that has fascinated astronomers ever since. Its characteristics have suggested that the star’s explosion resulted tens of thousands of years after the merger of two massive stars, but detailed models of this scenario have been lacking. In a Report in the 23 Feb 2007 Science , Morris and Podsiadlowski presented three-dimensional computer simulations of two stars merging that can explain many of the features of the triple-ring nebula. According to the team’s model, a fast-rotating progenitor of SN1987A swallowed a stellar companion about 20,000 years before the explosion. Detailed modeling of the angular momentum and accretion of gas from the two stars predicts two explosions: one that causes an hourglass-shaped ejection of material (eventually giving rise to the nebula’s two large outer rings), and a second that produces a smaller puff of gas (which could have formed the nebula’s smaller inner ring). An accompanying Perspective by N. Soaker highlighted the Report.


A Spicy History

Chili peppers arose in the Americas and were later introduced by European explorers to places such as India and Thailand , where the fiery spice has become an integral part of cuisine and culture. In a Report in the 16 Feb 2007 Science , Perry et al. shed light on when and where chili peppers were first cultivated. The researchers identified microfossils of starch grains on ancient pottery and stone tools that are diagnostic of groups of chili species. The microfossils were found at seven archaeological sites from the Bahamas to southern Peru , with the oldest sample --from Ecuador -- dating to about 6100 years ago. The starch data indicate that three of the five species of domesticated chili pepper were cultivated together in Peru in both the coast and the highlands as long as 4000 years ago -- even before the use of pottery. Furthermore, the starch grains were typically found in association with maize, and in some sites with yams and manioc (also known as cassava), which suggests that chili peppers were used not just as food but to add spice to cuisine. As noted in an accompanying Perspective by S. Knapp, the work opens up new avenues of research into how the peoples of the Americas transported and traded plants of cultural importance.


Flight Control

Even the slightest breeze can throw off the balance of a tiny flying insect. So how do these creatures stay steady during flight? Researchers have known that two-winged insects like houseflies and their relatives use their vestigial hindwings -- club-shaped appendages called halteres -- to detect rotational forces and thereby mediate flight stability. Now, a study by Sane et al. in the 9 Feb 2007 Science reports that hawk moths, which have four wings and thus lack halteres, possess a similar kind of flight control mechanism that relies on their antennae. High-speed films of hovering moths revealed that their antennae vibrate at the same frequency of their wingbeat and that the insects’ movements are tracked by small antennal deflections. Separate electrophysiological experiments showed that these deflections are detected by mechanosensors at the bases of the antenna and are transduced to neural centers that support motor control. Moths with amputated antennae proved far more likely to crash to the ground or collide with the walls of a flight chamber than intact moths, thus confirming the importance of the antennae for stable flight. An accompanying Perspective by R. M. Alexander highlighted the Report.


Sniffing Out Shorter Life

Restricting dietary caloric intake has been shown to prolong life span in a variety of organisms including yeast, worms, flies, and mice. Now, a Report in the 23 Feb 2007 Science (published online 1 Feb) explains that in fruit flies, just the smell of food can partially reverse the life-extending effects of caloric restriction. Libert et al. placed two strains of fruit flies on a restricted diet and then exposed some of them to the smell of live yeast -- a major component of their food. The team found that the exposed flies lived longer than normal, but died sooner that other dieting flies not exposed to the scent of yeast. The aroma had no effect on the survival of well-fed flies. The team then asked whether loss of olfactory function is sufficient to increase lifespan. They measured the lifespan of flies harboring a mutant form of the protein Or83b -- a key odorant receptor -- and found that fully-fed mutant flies lived up to 56% longer that wild-type controls. Like many long-lived organisms, the mutant flies also showed increased resistance to stresses like starvation. The authors propose that olfaction may regulate lifespan by signaling potential nutrient availability. As noted in a News story by M. Leslie in the 2 Feb issue, the new finding "adds to a growing body of evidence that an organism’s perceptions of its environment can have a big impact on its longevity."


New Route to Arthritis Treatment?

Rheumatoid arthritis (RA) is a chronic and painful autoimmune condition that leads to joint inflammation. But despite new treatments that focus on controlling overactive immunity, joint destruction and disability progress in many patients. In a Report in the 16 Feb 2007 Science (published online 25 Jan), Lee et al. proposed an alternative therapeutic approach that targets a nonimmune cell that is unique to joints -- the synoviocyte. These cells comprise an inner membrane of the synovium, or joint lining -- a layer that provides lubrication and nutrients for the cartilage. In RA, the synovium is infiltrated by immune cells that damage cartilage, while the synoviocytes produce proteases, cytokines, and other molecules that perpetuate inflammation. In the new study, researchers identified a cell adhesion molecule called cadherin-11 as essential for the development of the synovium and showed that mice lacking this molecule showed significantly reduced growth of the synovium and were resistant to the development of experimentally induced inflammatory arthritis. Furthermore, mice injected with therapeutics that blocked cadherin-11 function (like cadherin-11–specific antibodies) showed reduced cartilage damage. An accompanying Perspective by G. S. Firestein cautioned that animals models are different from human rheumatoid arthritis, so the applicability of cadherin-11–targeted therapy to RA still needs to be evaluated.


Spanish Flu Clues

The Spanish influenza pandemic of 1918-1919 killed an estimated 20 to 50 million people worldwide. Of particular interest to researchers has been the question of how a virus that is genetically similar to avian influenza viruses became transmissible between mammals. According to a Report in the 2 Feb 2007 Science , the answer lies in a viral surface protein. The binding of influenza viruses to their target cells is mediated by a viral surface protein called hemagglutinin (HA), which recognizes a type of sugar molecule called sialic acid on the surface of host cells. Whereas the HA in human flu viruses binds to a specific sialic acid configuration common in human airway cells, the HA in avian influenza viruses preferentially binds to a different configuration prevalent in bird gut cells. Now, Tumpey et al. report that two amino acid substitutions that cause a switch in the binding specificity of HA from mammalian to avian rendered the virus unable to transmit between ferrets (the best animal model for human flu), even though it still made the animals sick. As noted in an accompanying News story by M. Enserink, "[t]hose same changes in reverse may be what enabled the 1918 catastrophe -- and what could lead to the next one as well."


Complex Pneumonia Threat

The bacterial pathogen Staphylococcus aureus can cause a wide variety of conditions ranging from mild skin infections to life-threatening septic shock. Alarmingly, drug-resistant strains (so called methicillin-resistant S. aureas or MRSA) that were previously found exclusively in hospitals are now escaping and causing severe disease in otherwise healthy people in the community. Of particular concern are MRSA strains that produce a toxin called Panton-Valentine leukocidin (PVL) and cause necrotizing pneumonia -- an often deadly disease characterized by extensive lung tissue damage and low numbers of circulating leukocytes (white blood cells). In a Report in the 23 Feb 2007 Science (published online 18 Jan), Labandeira-Rey et al. offered important new insights into the molecular pathology of these strains. Studies in a mouse model revealed that PVL alone is sufficient to cause pneumonia and that expression of this toxin induces global changes in transcriptional levels of genes encoding secreted and cell wall-anchored staphylococcal proteins, including a lung inflammatory factor. The combination of these effects exacerbates the risk of fatal necrotic pneumonia. As noted in an accompanying Perspective by B.C. Kahl and G. Peters, these insights may help guide the development of drugs and vaccines that combat dangerous respiratory pathogens.


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In Science ’s STKE


Targeting the Kinome

In a Perspective published 20 Feb 2007 in Science ’s Signal Transduction Knowledge Environment (STKE) , Bozulic et al. offered a report of the "Targeting the Kinome" meeting which took place in Basel , Switzerland in early December 2006. The meeting brought together a diverse group of scientists including pharmaceutical researchers, chemists, and clinicians to discuss the past, present, and future of protein kinase research with a special emphasis on cancer therapy development. Topics of talks and posters ranged from the kinases themselves to the physiological and pathological they regulate, and highlighted candidate kinase genes that have served as successful drug targets as well as efforts and recent accomplishments in the development of small-molecule inhibitors of those kinases. The meeting also touched up on underexplored areas of kinase research and drug development including the identification of kinases involved in infectious diseases such as malaria and tuberculosis. Overall, the gathering not only provided a look at the history of kinase research but also provided attendees with new insight into and direction for the future of kinase-targeted drug development.


Also in STKE this month:

-- J.-G. Chen highlighted recent research showing that hexokinase1, a conserved glucose sensor in plants, forms a nuclear complex to regulate the transcription of target genes ( 13 Feb 2007 )
-- Nakata and Hirokawa looked at how kinesin superfamily proteins contribute to the formation of axons and dendrites ( 6 Feb 2007 )

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Apple and AAAS have teamed to offer you Apple products at preferred pricing. Shop the special online store for your discount, and receive free standard shipping on orders of $50 or more.