NANOTECHNOLOGY: Base sequences set shapes of gold-DNA nanoparticles
R
ESEARCHERS HAVE systematized how the
sequence of bases in a DNA molecule controls the shape and surface properties of gold-DNA nanoparticles. The findings could be used to create nanoparticles with shapes optimized for sensing, imaging, catalysis, and other applications. Researchers often use DNA strands to help control morphology in nanoparticle synthesis, but the process has been by trial and error. Chemical biologist Yi Lu of the University of Illinois, Urbana-Champaign, and coworkers, including Jinghong Li’s group at Tsinghua University, in Beijing, have discovered the method to this madness in preparing gold-DNA nanoparticles. By systematically varying DNA sequences added to solutions used to make gold-DNA nanoparticles, they found that like a genetic code, specific sequences lead to distinct particle shapes and surface characteristics (Angew. Chem. Int. Ed., DOI: 10.1002/anie.201203716). For example, adenine sequences induce the forma-
UN TARGETS SYRIA’S WEAPONS DIPLOMACY: Resolution raises alarm of regime’s threat to use chemical arsenal
T
HE UNITED NATIONS General Assembly has
overwhelmingly approved a resolution calling on Syria to maintain security around its chemical and biological weapons and condemning the regime for unleashing its military might against its civilian population. Sponsored by Saudi Arabia, the resolution expresses “concern at the threat by the Syrian authorities to use chemical or biological weapons” and calls for “an inclusive Syrian-led political transition to a democratic, pluralistic political system.” It demands that the Syrian regime refrain from using or transferring the weapons to “nonstate actors” and that it respect international obligations regarding those weapons. The U.S., Israel, and other nations are worried that if the weapons are not locked down and kept under strict control, militant groups might try to seize some of the munitions and use them in terrorist attacks. The General Assembly adopted the resolution on Aug. 3, with 133 member nations voting in favor, 12 voting against, and 31 abstaining. In addition to highlight-
tion of round but rough particles, guanine DNAs yield smooth-surface hexagons, and mixed-sequence DNAs lead to mixed or unexpected morphologies—such as the flowers that bloom when cytosine-thymine DNA is used. Lu says his group has begun extending the codes to a greater variety of sequence combinations and to other nanoparticles. Shana O. Kelley of the University of Toronto, an expert on biotemplated nanomaterials, says others have used DNA to control the morphology of nanomaterials, but predictive ability has been elusive. “Lu and coworkers have finally achieved this by studying in detail how each base affects the growth of gold nanopar- Scanning electron micrographs of gold-DNA nanoparticles show the ticles. The fine level of control atdistinct shapes and surfaces adopted tained is impressive,” she says. by particles containing different DNAs. Arizona State University’s Hao A = adenine, T = thymine, G = guanine, Yan, who also creates bioinspired C = cytosine. Nanoparticle diameters nanomaterials, says the study “is are about 150 nm each. the start of an exciting new direction” for applications such as nanophotonics, where shape-dependent plasmonic structures could enhance signals for biodetection.—STU BORMAN
ing the Syrian regime’s isolation, the legally nonbinding document could prod the more powerful UN Security Council into taking action to halt the bloodshed. The Security Council could pass sanctions, and it could also authorize the use of outside military force. Thus far, it has been prevented from demanding that Syrian President Bashar al-Assad step down because of opposition by China and Russia. The two nations are permanent members of the Security Council and have veto power. Syria is widely believed to possess a vast arsenal of operationallevel chemical and biological weapons,includingmustardagent, sarin, and possibly VX nerve agent. Syria is one of only eight nations in the world that have not joined the 1997 Chemical Weapons Convention, which prohibits the production, stockpiling, or use of chemical weapons. The Organisation for the Prohibition of Chemical Weapons, The Hague-based body that monitors treaty compliance, says it “currently has no legal mandate” to conduct inspections in Syria “to verify the possible existence of chemical weapons or related activities.” Syria, however, is a party to the 1925 Geneva Protocol, which bans the use of chemical and bacteriological methods of warfare.—GLENN HESS
WWW.CEN-ONLIN E .ORG
UN /JC MCILWAINE
DNA CONTROLS NANOSHAPES
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AUGUST 13, 20 1 2
The UN General Assembly votes on a resolution condemning Syria’s military campaign against antiregime rebels.
YI LU
NEWS OF THE W EEK
