NEWS OF THE W EEK
COUPLING NANOPARTICLES
ACS NANO
Azide-alkyne cycloaddition chemistry forms nanoparticle junctions that support lightinduced (blue arrow) charge transfer and separation.
MATERIALS: Cycloaddition chemistry
yields hybrid metal oxide materials
M
ULTIPLE TYPES of metal oxide nanoparticles
can be coupled via azide-alkyne cycloaddition reactions, thereby forming well-defined and customizable junctions between the particles, according to a study published in ACS Nano (DOI: 10.1021/ nn203585r). The work may lead to strategies for synthesizing novel materials with properties tailored for applications in catalysis and photovoltaics. TiO2, WO3, and oxides of other metals are active photocatalysts as a result of their electronic structures, which mediate conversion of light into chemical energy. The oxides are also central to dye-sensitized solar cells as a result of their knack for facilitating light-induced charge separation and transfer. Blending more than one type of metal oxide can lead to hybrid products with enhanced
FIGHTING NEUROPATHIC PAIN METABOLOMICS: Researchers discover a metabolite associated with chronic pain from tissue injury
T
HE OVERPRODUCTION of a previously
unknown endogenous metabolite called N,Ndimethylsphingosine (DMS) in injured tissues may be a key cause of a condition called neuropathic pain, according to a Nature Chemical Biology report (DOI: 10.1038/nchembio.767). The findings, which identify DMS production as a potential novel target to which inhibitors might be directed, could lead to more effective drugs to treat the condition. Neuropathic pain is a chronic disorder associated with tissue injury. The condition is characterized by periodic or constant “pin-and-needle” sensations; stabbing, burning, or electric-shock-like pains; or feelings
VIDEO ONLINE
See how Gary Patti’s team discovered the new target for neuropathic pain medications at cenm.ag/pain. WWW.CEN-ONLIN E .ORG
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properties relative to the individual starting materials, if the components can be mixed intimately enough. For that reason, several researchers have studied methods for combining oxides by forming various types of physical mixtures. Chemical ways of combining oxides could offer greater control and customization options, yet few studies have focused on developing such methods. Now, Allison C. Cardiel, Robert J. Hamers, and coworkers at the University of Wisconsin, Madison, have shown that classic cycloaddition reactions can be used to form nanoscale metal oxide junctions. They prepared TiO2 and WO3 nanoparticles functionalized, respectively, with alkyne and azide groups. Then they coupled the particles through a copper-catalyzed cycloaddition reaction. That reaction forms a triazole linkage that supports electron transfer. Indeed, the team found from laser-driven photo response measurements that films of the hybrid material support rapid charge transfer. And in a test of the material’s photocatalytic properties, they found that it decomposed methylene blue faster and more actively than the individual components did. “This hybrid nanostructure is an important advance for understanding the basics of charge transfer, and could help develop and optimize devices such as solar cells and photocatalysts,” comments Jillian M. Buriak, a professor and nanomaterials chemist at the University of Alberta.—MITCH JACOBY
of tingling or numbness. Current medications have adverse side effects such as addiction and fatigue and only rarely alleviate pain completely. Biochemist Gary J. Patti of Washington University in St. Louis; therapeutics expert Marianne Manchester of the University of California, San Diego; metabolomics specialist Gary Siuzdak of Scripps Research Institute; and coworkers detected the DMS surge via systematic metabolite analysis, known as metabolomics. They used liquid chromatography/mass spectrometry to survey metabolites in tissues from rats experiencing pain from a cut nerve. They found that DMS is produced at abnormally high levels in the rats’ spinal cords and causes pain when injected. The results suggest that inhibition of endogenous DMS production, with a methyltransferase or ceramidase inhibitor, for example, may be an attractive therapy, the researchers write. “In this groundbreaking study, the authors have used metabolomics not only to provide new insights into the pathogenesis of chronic pain, but also to uncover a potential new therapeutic target for a condition that is extremely difficult to treat,” comments cellular stress response specialist Albert Fornace Jr. of Georgetown University. “This is an exciting discovery,” says metabolite profiling expert Alan Saghatelian of Harvard University. If future studies confirm that DMS is involved in a new and unique pain pathway, “it will be a very important finding,” he says.—STU BORMAN
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