Lawrence Livermore National Laboratory



Biomechanical Regulation of a Key Gene in Bone

Researchers from Lawrence Livermore, in collaboration with those at the University of California at Davis and Indiana University School of Medicine, investigated a regulatory element for the gene controlling bone mechanoadaptation—how bone formation responds to pressure loading and unloading. The research appeared in the September 4, 2016, online edition of the science journal, Bone.

Over time, pressure loaded on the skeleton builds bone mass, while bone mass is lost from disuse. The gene that expresses sclerostin (Sost), a protein that regulates bone turnover, is a negative regulator of bone mechanoadaptation. The study hypothesized that the noncoding enhancer ECR5 was the primary regulatory element, signaling to the Sost gene whether it should turn on or off during loading and unloading. Researchers found removing ECR5 did not prevent the effects of unloading on mice with Sost. “This finding suggests that ECR5 is not the only regulatory element at play with load-induced regulation of Sost. Bone expression is driven by multiple regulatory elements, and the promoter of the gene may be more important than the regulatory element in this situation,” says Gaby Loots, a Livermore biomedical scientist and co-author of the paper.

The scientists plan to apply this study’s findings toward new research for NASA to help negate the effects of unloading and radiation-induced bone loss in astronauts who spend significant time in space. Astronauts aboard the International Space Station can experience 1–2 percent bone loss per month because of radiation exposure and lack of gravity. Exploring treatment with temporary lack of Sost could help overcome these side effects of space travel.
Contact: Gaby Loots (925) 423-0923 (loots1@llnl.gov).

Elemental Compositions Defy Old Theory

Ten years ago, researchers discovered that rocks on the surface of Earth had a higher abundance of neodymium-142 (142Nd) than did primitive meteorites (also called chondrites). This finding was contrary to the long-standing theory suggesting their chemical and isotopic compositions were the same. The discovery lead to a hypothesis that Earth either had a hidden reservoir of neodymium in its mantle or inherited more of the parent isotope samarium-146 (146Sm), which subsequently decayed to 142Nd.

In research appearing in the September 14, 2016, online edition of Nature, Lawrence Livermore scientists, in collaboration with researchers from the University of Chicago and Westfälische Wilhelms-Universität Münster in Germany, showed the abundance of several Nd isotopes in Earth differ compared to chondrites. Using high-precision isotope measurements, the scientists determined that differences in 142Nd between Earth and chondrites reflected nucleosynthetic processes and not the presence of a hidden reservoir or excess 146Sm. They used large sample sizes (about 2 grams) to obtain improved isotope data for a comprehensive set of meteorites.

According to the team’s results, Earth contains Nd that is slightly more enriched by the slow neutron-capture process that occured during the production of Nd in asymmetric giant branch stars. “The research calls into question a fundamental tenet of geochemistry,” says Livermore chemist Lars Borg, who co-authored the paper. “It has tremendous implications for our principal understanding of Earth, not only for determining its bulk composition, heat content, and structure, but also for constraining the modes and timescales of its geodynamical evolution.”
Contact: Lars Borg (925) 424-5722 (borg5@llnl.gov).

Unprecedented Purification of Copper Nanowires

A team of Lawrence Livermore scientists has developed a new purification method for producing long, uniform, high-purity copper nanowires with unprecedented yields. The research appears in the October 7, 2016, edition of Chemical Communications and was subsequently featured on the cover of the print issue.

The most common approaches to create nanowires also produce byproducts in the form of other low-aspect-ratio shapes, including nanoparticles and nanorods. This difficulty has limited adoption of nanomaterials in many manufacturing technologies. “We have discovered a new approach to efficiently separate copper nanowires from nanoparticles based on their respective surface chemistries. This purification route is a facile, rapid, and inexpensive way to purify different nanomaterials, and it should be broadly applicable,” says Lawrence Livermore’s Fang Qian, the lead author of the paper. The team demonstrated that copper nanowires, synthesized at liter scale, were purified to near 100 percent yield from their nanoparticle side-products with a few simple steps.

The nanowires and nanoparticles are coated with hydrophobic surfactants and then suspended in an actively agitated mixture of water and organic solvent. Eventually, the immiscible mixture phase separates, allowing the nanowires to spontaneously cross the interface and separate from the nanoparticles. The team’s high-purity copper nanowires meet many of the demanding requirements for potential electronics applications, and the general separation approach provides a possible route to purify industrial-scale quantities of nanomaterials, which remains a key hurdle to the wider commercialization of nanowires. Qian says, “This purification method will open up new possibilities in producing large quantities of high-quality nanomaterials at low cost.”
Contact: Fang Qian (925) 424-5634 (qian3@llnl.gov).