NEWS OF THE WEEK MATERIALS
coworkers believe the host molecules move cooperatively within the crystal, handing off guest molecules to one another. "It's like a massive relay race," Atwood notes. "The first runner passes the baton to the second, the second to the third, and so on." The researchers have already observed the same phenomena with other guests. They are filing host is transformed into a single a patent application on their discrystal of the complex without covery, concentrating on its podissolving or fracturing [Science, tential use in separations. "This simple experiment with 298,1000(2002)}. "It's incredible that the crystal well-known materials has tremenmaintains its integrity while un- dous implications for solid-state dergoing such a phase transition," dynamics," comments Jonathan says chemistry professorJerry L. W. Steed of King's College LonAtwood, who led the Missouri don in the same issue. "If nonteam. "It shows our understand- porous solid-state diffusion can ing of the organic solid state is happen with calixarenes, the implication is that it can happen with still in the primitive stage." Atwood, research assistant many other materials."—PAMELA professor LeonardJ. Barbour, and ZURER
SCIENCE
CALIXARENE COOPERATIVITY
Hosts work together to convey guest molecules through nonporous crystal
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REORGANIZATION Purep-ferf-butylcalixUlarene (top) crystallizes in offset bilayers. After taking up vinyl bromide, the bilayers are aligned (bottom). Vinyl bromide molecules occupy each calixarene cavity but for clarity are not pictured.
HEN D I P P E D INTO L I Q -
uid vinyl bromide, single crystals of a wellknown calixarene rapidly take up the olefin to form a solid one-toone host-guest complex. That would be no surprise if the starting crystal contained channels through which the olefin could travel or if the crystal dissolved and then recrystallized. But in the case discovered at the University of Missouri, Columbia, a channel-free single crystal of the pure
had not been resolved," Tiedje says. TCA1 can't survive without TCApresent, he adds, and it's not active against chloroethenes. In anaerobic lab cultures, TCA1 reduced TCA to 1,1-dichoroethane and then to chloroethane over several weeks. In lab tests on soils taken from a contaminated site,TCAl converted TCA to chloroethane in two named TCA1, was isolated from months. Chloroethane can be BACTERIUM THAT D E pends on reducing 1,1,1- river sediments by postdoc Baolin degraded to C 0 2 and chloride trichloroethane (TCA) for Sun, microbiology professor ions by aerobic soil bacteria, the sustenance is the latest addition James M. Tiedje, and coworkers Michigan State researchers note, to a line of microbes that can de- at Michigan State University's so a combination treatment could grade chlorinated solvents. Iden- Center for Microbial Ecology be carried out to clean up a contifying these bacteria and under- [Science, 298,1023 (2002)}. De- taminated site. standing their halobacterb&ctzndL, first described Research on contaminant-demolecular bio- in 1994, couple their growth to grading bacteria should continue logy is rapidly the reduction of a chlorinated sol- "at a feverish pace," notes civil expanding the vent using H 2 as a reducing and environmental engineering options for in agent—a process called dehalo- professor James M. Gossett of Cornell University in a related situ remedia- respiration. tion of soil and This process has been ob- commentary. "Studying the groundwater at served to degrade chloroethenes, degradation enzymes of these Superfiind and chlorobenzenes, and 2-chloro- microbes and their regulation— other waste phenol. But until now, dehalo- as well as genetic relationships respiration hasn't been reported among all subsurface microorsites. CHLORINE DIET Tiedje (left) and The bacteri- for TCA. "TCA was one of the ganisms—will provide new insights into bioremediation," he Sun pose with a culture vial of TCA1 in um, a Dehalo- remaining groundwater polluwrites.-STEVE RITTER action against trichloroethane. tants for which biodégradation bacter strain
BIOREMEDIATION
MICROBE MUNCHES ON CHL0R0CARB0N Newly discovered bacterium is first known to degrade trichloroethane
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