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of the radiation balance in these distantgiant planets,” Hammel says. —R. COWEN

Detecting LeadSensor changes color fortoxic metal

Lead poisoning has serious health conse-quences in adults, including brain andkidney damage, and causes various devel-

opmental problems in children. That’swhy lead testing has become an impor-tant public health measure.

Commercially available tests for detect-ing lead in household paint sometimesgive incorrect results, says Yi Lu of theUniversity of Illinois at Urbana-Cham-paign. More sophisticated tests for thetoxic metal can be more reliable, but theyrequire expensive equipment and exper-tise.

In the June 4 Journal of the AmericanChemical Society, Lu and Juewen Liu, alsoof the University of Illinois, describe areliable sensor that uses a simple colorchange to indicate the amount of lead inpaint. The scientists devised the sensorsfrom gold nanoparticles and tailor-madeDNA strands.

To conduct a test, chips of either water-or oil-based paints are dissolved in dilute

vinegar and a drop of the liquid is addedto a test tube containing the sensors. Adrop of this solution is then placed on analumina test plate. If the solution con-tains lead, it produces a purplish or redspot. Lead-free drops produce blue spots.

To make their sensors, the researchersuse three ingredients: 13-nanometer-widegold particles adorned with short strandsof DNA; strands of so-called catalyticDNA, which can snip apart other DNA,strands; and longer DNA strands to whichthe first two ingredients attach.

In the absence of lead, the catalyticDNA doesn’t break up the longer DNA,and the bound nanoparticles aggregateinto a structure that appears blue. How-ever, in the presence of lead, the catalyticDNA snips the longer DNA, separatingthe nanoparticles. Then, the particlesdon’t aggregate, and they appear red.

Acentury after two brothersfrom Ohio launched thefirst powered aircraft, more

than 1,200 high school stu-dents from 31 countries lastweek descended on Clevelandin a celebration of science andengineering—and competitionfor more than $3 million inscholarships and prizes.

The youthful competitors inthe Intel International Scienceand Engineering Fair filledCleveland’s convention centerwith row upon row of custom-made gizmos and colorfulposters detailing their research.They described their projects toabout 1,000 judges and agreater number of curious visi-tors, and by week’s end, morethan 500 claimed awards.

Many of the students alsotook in speeches and panel dis-cussions by astronauts andNobel laureates.

For the first time in the com-petition’s history, three youngwomen took the top prizes—a$50,000 scholarship plus a high-performance computer. Onewinner, Elena Leah Glassman,16, of Central Bucks High SchoolWest in Doylestown, Pa., devel-oped a method for reading elec-trical impulses in the brain thatcould help people with musculardisabilities operate computers.

Lisa Doreen Glukhovsky, 17,of New Milford High School inConnecticut won her top prizefor using telescope images todetermine the distance fromEarth to more than a dozenasteroids that might somedaycross the planet’s path. NASAhas used Glukhovsky’s data torefine its orbital calculations forthose potential celestial threats.

Anila Madiraju, 17, of Maria-nopolis College in Montrealearned her $50,000 scholarshipby showing that it’s possible tokill cancer cells by silencing pro-teins that inhibit cells from dyingat appropriate times.

Madiraju was also one ofthree students to be awarded afully paid trip to this Decem-ber’s Nobel prize ceremonies inStockholm. The other Nobel-bound competitors are AnantRamesh Patel, 18, of AstronautHigh School in Titusville, Fla.,and Ethan James Street, 18, ofWinston Churchill High Schoolin Livonia, Mich.

Andrew Gerard Ascione, 18,Aaron David Schulman, 17, andDavid Edwyn Bennett, 17, all ofBroadneck Senior High Schoolin Annapolis, Md., earned a tripto this September’s EuropeanUnion Contest for Young Scien-tists in Budapest. There they

will again present the softwarethey’ve developed for identify-ing certain patterns in DNA.

A team effort to exploremicrobes as fuel producers willsend Wesley Ryan Fuller, 18,Blair Elisabeth Kowalinski, 16,and Kyle Anthony Marsland, 18,all from Hamilton High Schoolin Chandler, Ariz., to the Inter-national Youth Science Exhibi-tion in Moscow, Russia, in July.

Seventeen students eachgarnered scholarship awards of$5,000 and a high-performancecomputer—plus $1,000 fortheir schools and $1,000 fortheir regional science fair—forprojects judged to be best intheir field. Winners includedGlassman in computer science,Glukhovsky in earth and spacesciences, Madiraju in medicineand health, Patel in gerontol-ogy, Street in mathematics, andAscione, Schulman, and Ben-nett in the team category.

The other best-in-categoryawards went to Sita ChandrikaPalepu, 17, of James MadisonHigh School in Vienna, Va., in thebehavioral and social sciences;Samuel James Amberson How-ell, 16, of Saginaw Arts and Sci-ences Academy in Michigan inbiochemistry; Brian Lee Fisher,17, of Mandan High School in

North Dakota in botany; DenisAlexandrovich Malyshev, 16, ofMoscow Chemical Lyceum inRussia in chemistry; Ryan Karnik,16, of Oregon Episcopal Schoolin Portland in engineering;Katherine Douglas Van Schaik,16, of Spring Valley High Schoolin Columbia, S.C., in the environ-mental sciences; Jarryd BrandonLevine, 17, of Paul D. SchreiberHigh School in Port Washington,N.Y., in microbiology; MaireadMary McCloskey, 17, of LoretoCollege in Coleraine, Ireland, inphysics; and Simeon McMillan,17, of Uniondale High School inNew York in zoology.

Intel of Santa Clara, Calif., hasbeen the main sponsor of the fairsince 1997. Science Service ofWashington, D.C., which pub-lishes Science News, has admin-istered the fair since its inceptionin 1950. —B. HARDER

Test FlightYoung scientists earn—and spread—their wings

WINNING WOMEN AnilaMadiraju (left), Elena Glassman(center), and Lisa Glukhovsky(right) took the top prizes.

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With low concentrations of lead, somegold particles aggregate and others don’t,resulting in intermediate purple colors.

High concentrations of lead in paintcan overwhelm sensitive detectors. Forthat reason, Lu makes sensors for a rangeof lead concentrations by replacing someof the catalytic DNA with similar strandsthat don’t snip DNA. These sensorsrequire more lead ions to trigger a redresponse.

“It’s really innovative and excitingresearch,” says James Storhoff of theNorthbrook, Ill., company called Nano-sphere, which was founded by North-western University researchers RobertLetsinger and Chad Mirkin. Several yearsago, Storhoff, Letsinger, Mirkin, and theircolleagues invented a similar system fordetecting DNA. According to Storhoff,Lu’s new sensor is remarkably selectivefor lead ions.

Homeowners might use the aluminaplates or paper strips and a solution of

the nanoparticle-based sensors to testtheir walls for lead, says Lu. Eventually, byusing other catalytic DNA strands, these

household kits may test for a variety ofmetal ions, including mercury, arsenic,and chromium, he says. —J. GORMAN

GOLDEN HUES In leadfree environments, gold nanoparticles (red) adorned with short DNAstrands assemble onto longer strands of DNA (purple) and aggregate into a structure thatappears blue. In the presence of lead (Pb) ions, catalytic DNA (green) snips the longer DNAstrands. This prevents aggregation, and the gold particles appear red.

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