SCIENCE/TECHNOLOGY CONCENTRATES Science Acid rain may promote mosses that kill trees Lethal effects on forests may result from the promotion of mosses by acid rain, according to Lee Klinger, a geographer with the advanced study program at the National Center for Atmospheric Research in Boulder, Colo. Klinger has identified such mosses in the Rocky Mountain area and speculates that increased growth of mosses due to higher pollution levels has caused reduced growth and death of forests in the region during the past 20 years or so. His findings show that moss produces organic acids, which combine with naturally inactive aluminum in the soil and air. Organic acids activate the aluminum, transporting it down into the rooting zone of the trees. The aluminum displaces essential calcium ions, causing a calcium deficiency in the fine roots near the surface. As a result, the nutrient-deficient roots die. Affected trees die from the top down because there are not enough fine roots left to create the pressure needed to force water and nutrients to the treetops.
Directory of molecular biology databases The recent thrust to decode the human genome has provided a strong impetus for creation and maintenance of a computerized directory of molecular biology databases. Such a "database of databases" has now been compiled at Los Alamos National Laboratory and is available to researchers without cost on electronic mail, floppy disk, or in printed form. Called the Listing of Molecular Biology Databases, or LiMB, it contains information on about 60 databases, and the number is continuing to increase. LiMB is expected to evolve into a system directly supporting communicative software. Current information in LiMB includes the names of the databases, the type and amount of data they hold, descriptions of the hardware and software, and details about access to the data. According to LiMB project leader Christian Burks, the human genome project will involve efforts to generate new data sets in a systematic way. There will be a strong need, he says, to keep track of the databases spinning off the genome project.
Hybrid protein destroys HIV-infected cells NIH scientists have fashioned a hybrid protein that works like a self-guided missile, searching out and destroying only cells that are infected with human immunodeficiency virus (HIV) [Nature, 335, 369 (1988)]. The hybrid protein was genetically engineered to contain key portions of the human CD4 protein and a potent toxin made by Pseudomonas bacteria. The CD4 portion homes in on HIV-infected cells and binds to gpl20, an HIV glycoprotein found on the surface of infected cells that are manufacturing new HIV particles. The toxin portion of the hybrid protein then kills the cell and the fledgling viruses 22
September 26, 1988 C&EN
within it. In in-vitro experiments, the CD4-toxin hybrid has killed infected human white blood cells while leaving uninfected ones unharmed, according to NIH's Ira Pastan, Bernard Moss, and five coworkers. Pastan says it will be at least a year before tests in humans can begin. A soluble version of the CD4 protein itself is currently in clinical trials as a possible means of inhibiting the infectivity of HIV (C&EN, Aug. 15, page 6).
Double helix wraps aroundfivecopper ions Two molecules, each consisting of a linear chain of five bipyridine units, spontaneously wrap themselves around five copper(I) ions in solution to form a double-stranded helical complex reminiscent of DNA. That's the latest finding of recent Nobel Prize winner Jean-Marie Lehn and coworker Annie Rigault of Louis Pasteur University in Strasbourg, France [Angezv. Chem. int. Ed. Engl., 27, 1095 (1988)]. Lehn's group previously had made similar complexes using shorter chains of bipyridine units. Whereas DNA's double helix is held together by hydrogen bonds and stacking interactions, the structure of the new copper complex is determined largely by the coordination between Cu + and the nitrogens of the bipyridine units. The complex, Lehn says, is a chiral, self-organized nanostructure containing a string of metal ions. Hence, it may have potential in the field of functional nanoscale species and molecular devices. Angewandte Chemie saw fit to adorn its latest cover with the complex and proclaims, "The field is wide open for organic, inorganic, physical, and biochemical studies/'
Technology New metallic glasses are very strong, flexible Single-phase glassy alloys rich in aluminum have been melt spun into continuous ribbons by researchers at the University of Virginia, Charlottesville [Science, 241, 1640 (1988)]. The ribbons, about 15 Mm thick and 1 to 2 mm wide, are 'Very flexible and [can] easily be bent in half without fracturing/' say Yi He and Joe Poon of the physics department and Gary J. Shiflet of the materials science department. By contrast, amorphous alloys containing somewhat lower levels of aluminum that were made at other labs using different techniques were reported to be brittle. The Charlottesville alloys have compositions of Al9o(M,L)io or Al87(M,L)i3/ where M is a metal such as iron, cobalt, nickel, or rhodium, and L is a lanthanide such as cerium. The tensile strength of some of these alloy ribbons greatly exceeds that of the strongest commercial aluminum alloys, the researchers note. The strongest alloy they tested, Al9oFe5Ce5, has a tensile strength of 940 megaPascals. The Young's modulus of these metallic glasses, though, is lower than that of crystalline aluminum alloys. Similar results were reported recently by a team at Tohoku University in Sendai, Japan.
