SCIENCE/TECHNOLOGY CONCEIVTRATES •1 Mercury-containing superconductor has high Tc A mercury-barium-copper oxide that is superconducting at temperatures as high as 94 K has been discovered jointly by researchers in Russia, France, and the U.S. [Nature, 362, 226 (1993)1. Although many cuprate superconductors have been discovered in the past six years and some of them work at even higher temperatures, the new compound, HgBa2Cu04+5, is especially promising for several reasons. It is structurally simple and apparently easy to synthesize, unlike many recently discovered copper oxide superconductors. And the smaller separation between its Cu0 2 layers may lead to advantageous superconducting properties, according to its discoverers, S. N. Putilin of Moscow State University and colleagues. Moreover, the compound's transition temperature (Tc) of 94 K is 'Very high, especially for a superconductor based, as it is, on a single copper layer," says Robert J. Cava, a prominent superconductivity researcher at AT&T Bell Laboratories in Murray Hill, N.J. If other members of this family can be synthesized with double or triple Cu0 2 layers, Cava says, they should work at even higher temperatures, holding out the hope of breaking the 127 K record currently held by a superconductor with two thallium and three copper oxide layers. Development of the thallium compounds has slowed because of several problems. Perhaps HgBa2Cu04+6, or another member of this new cuprate family, will have a lofty Tc without those problems, Cava suggests in a Nature commentary. "Only further research will tell," he adds.
• Recombinant bacterium makes indigo from glucose A recombinant microorganism that can directly synthesize indigo from glucose has been developed by Burt D. Ensley at Amgen, Thousand Oaks, Calif., and coworkers [Bio/Technology, 11, 381 (1993)1. Although a biosynthetic route to the textile dye indigo was found in Escherichia coli in 1983, several roadblocks stood in the way of a microbial process for making indigo. Chief among them were the low activity and half-life of naphthalene dioxygenase, a key enzyme in the pathway, and the need to use expensive tryptophan or indole as starting materials. Ensley and coworkers extensively modified £. coli by genetic means to improve the activity and half-life of naphthalene dioxygenase and to make possible the use of inexpensive glucose as a starting material. A five- to 10-fold improvement in bacterial indigo output is still needed for the biosynthetic route to be competitive with current commercial processes. However, some current processes use hazardous reagents and generate toxic byproducts, giving bacterial fermentation the edge as an environmentally benign alternative.
• Gene therapy for cystic fibrosis succeeds in mice The first use of gene therapy to correct a form of cystic fibrosis in mice represents a key step toward being able to treat the disease in human patients. The study was conducted by Christopher F. Higgins of John Radcliffe Hospital at the University of Oxford, U.K., and coworkers [Nature, 362, 250 (1993)]. Cystic fibrosis is a lethal inherited disorder that af18
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fects about one in 2000 Caucasians. The disease causes mucous and bacteria to accumulate in the lungs, owing to abnormalities in chloride ion transport across membranes of airway epithelial cells. The abnormalities are caused by mutations in a gene that encodes cystic fibrosis transmembrane regulator protein (CFTR). Mice whose CFTR gene is artificially disrupted show symptoms similar to those of the human disease. Higgins and coworkers find that introducing an aerosol of liposomes containing the human CFTR gene to the airways of such mice corrects the ion-conductance defects. They point out that liposomes may be safer than viruses, which are also being tested as delivery agents for corrective cystic fibrosis genes. Viruses can replicate, be transmitted to others, and evoke an immune response, whereas liposomes are nontoxic and nonimmunogenic, they say.
• Advanced materials R&D lab launched in U.K. RUSTI—the Research Unit for Surfaces, Transforms & Interfaces—opens its doors next month at Daresbury, near Liverpool, England. Organized by the U.K/s Science & Engineering Research Council, with professional and material support from chemical producer ICI, its aim is to allow academic and industrial scientists to carry out research on advanced materials and find practical uses for them, notes Hywel G. Price, who heads the facility. Price has been in charge of the nuclear structure facility at Daresbury, which is closing. Workers at RUSTI will have access to the advanced research computing operation and to the synchrotron radiation source at Daresbury and will be able to draw on in-house expertise in the use of ion beams for surface studies. ICI is moving a Scienta high-resolution x-ray photoelectron spectrometer, the only one of its kind in the U.K., from its materials research center to RUSTI to be used for studying surfaces and interfaces of materials at the molecular level during their formation. David Clark, who helped develop the spectrometer and until recently was head of the ICI materials center, now is RUSTTs scientific director.
• Tests begin on nuclear waste processing facility A program to test the design of a waste processing system at the Savannah River nuclear site in South Carolina has begun. With authorization from the Department of Energy, Westinghouse Savannah River Co. is now carrying out the first phase of a four-part testing program, making cold chemical runs at the defense waste processing facility (DWPF) on the site. DWPF is designed to immobilize highlevel radioactive waste into a stable and durable borosilicate glass through vitrification. Molten waste and frit will be poured into stainless steel canisters to harden, and the canisters, after cooling, will be welded closed for temporary storage at Savannah River and eventual shipment to a federal repository. The cold chemical runs will last six to eight weeks, and additional tests will take place over the next 18 months, before radioactive operations start. Nonradioactive chemicals simulating the chemical and physical properties of radioactive liquid waste are being used to verify the ability of DWPF to receive and process liquid waste and ensure proper operation of facility equipment.
