NEWS OF THE W EEK
WEAK FORCES BIOPHYSICS: Method reveals changes induced by subtle means
A
FALLING FEATHER exerts negligible pressure
on the surface it lands upon. In the macro world, such impact is of no consequence. In the diminutive world of the cell, though, many events depend on exquisitely subtle effects. But because the forces involved are so weak—as little as 0.5 piconewtons—
SCIENCE ©2007
COMBO METHOD A DNA structure (cylinders) labeled with fluorescent dyes (red and green dots) and attached to a surface by a link (black) is tethered to a bead (blue sphere) trapped in a laser beam. When force is applied through the linker, the DNA can interconvert between two conformations, which can be detected via the fluorescence signal.
BASF DEDICATES TWO TEXAS PLANTS PRODUCTION: New world-scale plants
integrate polymer manufacturing
B
ASF EXECUTIVES enjoy showing off com-
BASF
BASF produces nylon 6 pellets at its new Freeport, Texas, plant.
plete manufacturing integration, a concept they call by the German word Verbund. They did this last week at the opening of two new worldscale plants in Freeport, Texas. The facilities establish the site as BASF’s integrated production base for nylon 6 and superabsorbent polymers (SAPs) in North America. Investing more than $200 million in the plants “demonstrates our longterm commitment to Freeport and to BASF in the U.S.,” said Kurt Bock, CEO of BASF’s North American arm, at the event. BASF’s strategy is to strengthen its U.S. base while seeking logistical and cost-saving benefits that improve its competitive position, he explained. The company WWW.C E N- ONLI NE .ORG
12
it has been difficult to detect and study such events. Now, a new technique allows researchers to measure changes on biological molecules caused by weak forces (Science 2007, 318, 279). With this tool, researchers could gain insights into processes or systems where weak forces play a regulatory function, such as DNA synthesis or ion channels proposed to be involved in hearing. At the cellular level, weak forces are far more biologically relevant than strong forces, says Taekjip Ha, a biophysicist at the University of Illinois, UrbanaChampaign, and leader of the team that did the study. Most single-molecule mechanical techniques, he notes, work well only with strong persistent forces. The new technique combines fluorescence spectroscopy with optical tweezers, in which a laser beam is used to trap and manipulate objects. The researchers use optical tweezers to apply a small force to a fluorescencelabeled object and detect the effect of the applied force on the object’s shape by way of fluorescence signals. Ha and coworkers used the technique to study the effects of small forces on the four-armed DNA structure known as a Holliday junction, which is involved in DNA recombination. They found significant changes in the structure even at forces as weak as 0.5 pN. The conformational changes caused by such forces can’t be measured by traditional force experiments, which generally require forces of 10 pN or higher.—CELIA ARNAUD
has been restructuring its North American operations along these lines for about two years. To combine production of polymers and their feedstocks, BASF built a 120,000-metric-ton-per-year nylon 6 plant near a facility producing caprolactam. The new nylon plant replaces one about half as big that BASF has closed in Enka, N.C. It also supplants material previously obtained through toll agreements and adds 30,000 metric tons of new capacity. The output will go largely to North American engineering plastics markets, said Harald Lauke, president of BASF’s performance polymers division. Likewise, the new SAP plant is fed by nearby acrylic acid production. The 180,000-metric-ton plant replaces smaller SAP units BASF has shut down in Aberdeen, Miss., and Portsmouth, Va., while adding 20,000 metric tons of capacity. BASF has been installing proprietary SAP production technology at its worldwide sites since 2002, said Markus Kramer, president of BASF’s functional polymers division. In 1958, Freeport was BASF’s first manufacturing site outside of Europe and remains a cornerstone of its operations, Bock said. The two latest plants started up in July and already are running at full capacity. High costs and labor shortages make it extremely tough to build a case for investing on the Gulf Coast, Bock noted. Nevertheless, in pursuit of Verbund, BASF will have spent $500 million along the Gulf between 2006 and 2007 that includes expanding plants in Freeport; Geismar, La.; and Pasadena, Texas.—ANN THAYER
OCTOBE R 1 5, 20 07
