Life Science

Department of Microbiology & Immunology University of Illinois Chicago - Through cloning and sequence analysis, researchers have identified the primary gene of the hereditary disease muscular dystrophy, thus leading to the characterizing of the primary protein product. Deletions contributing to an absence of the polypeptide dystrophin (0.002% of total muscle protein and 3,685 amino acids long) on the inner surface of the plasma membrane appear to be the primary cause for two types of muscular dystrophy. The polypeptide may play cytoskeletal roles, since it is sequence-related to spectrin and à-actinin. A.P. Monaco, "Dystrophin, the protein product of the Duchenne/Becker muscular dystrophy gene," Trends in Biochemical Sciences, 14, 412-5, October 1989. (Imperial Cancer Research Fund, London) Biological light emission (cold light, bioluminescence) has had a "gee-whiz" attraction for humans since the days of the ancient Greeks. New recombinant DNA technology for "gene fusions" and the use of the bioluminescence (lux) operon as a "reporter gene" have come forward with fusions of the two luciferase structural genes (luxA and luxB) into a single gene hooked up to emit light in bacteria, yeast, and higher plants. O. Olsson, A. Escher, G. Sandberg, J. Schell, et al., "Engineering of monomeric bacterial luciferases by fusion of luxA and luxB genes in Vibrio harveyi," Gene, 81 (2), 335-47, October 1989. (University of Ume , Sweden; University of Alberta, Edmonton, et al.) Recombinant DNA technology is also being applied to basic questions of population genetics and evolution. The question of "neutral alleles" versus selection becomes more realistic when one considers the interplay between related gene products - especially those with variations of the classic lac operon functioning in an isogenic cellular background. A.M. Dean, "Selection and neutrality in lactose operons of Escherichia coli," Genetics, 123, 441-54, November 1989. (York University, Toronto) The methionine biosynthetic pathway genes, which are scattered around the chromosome, are regulated by the MetJ repressor with co-repressor S-adenosylmethionine. The X-ray diffraction solution of the MetJ structure, with and without S-adenosylmethionine, has shown an absence of a typical "helix-turn-helix" structure. A pair of á-strands actually fit into the DNA helix. Several dimeric MetJ proteins, configured in a superhelix, fold themselves around the met operator in tandem. J.B. Rafferty, W.S. Somers, I. Saint-Girons, S.E.V. Phillips, "Three-dimensional crystal structures of Escherichia coli met repressor with and without corepressor," Nature, 341, 705-10, 26 October 1989. (University of Leeds, England; Institut Pasteur, Paris) Immunology has blossomed from complex phenomenology into simple models and on to complex molecular reality - all in a generation. A new article helps explain how the major histocompatibility locus and small digested peptides from protein antigens interact together to provide helper and cytotoxic T cells with needed information for recognition. H.M. Grey, A. Sette, S. Buus, "How T cells see antigen," Scientific American, 261, 56-64, November 1989. (Cytel Corp., La Jolla, Calif.; Scripps Clinic, La Jolla, Calif.; University of Copenhagen, Denmark) Department of Earth Sciences Open University Milton Keynes, U.K. The Mg/Si ratio of the earth's mantle (1.27) differs from that of carbonaceous chondritic meteorites (1.05). It has been assumed hitherto that the latter is the more representative of the primordial solar nebula and that the earth's mantle for some reason is significantly depleted in silicon. However, it is more likely that, because of the transfer of a very small amount of the earth's silicon outward to the asteroid belt (where, condensing on small particles, it would have a disproportionate effect), the chrondritic Mg/Si ratio is the anomalous one. A.E. Ringwood, "Significance of the terrestrial Mg/Si ratio," Earth and Planetary Science Letters, 95, 1-7, October 1989. (Australian National University, Canberra) It is well known that the injection of fluids into the ground can induce seismicity by increasing pore pressures. However, withdrawal of fluid (oil, for example) can also induce earthquakes, even though the pore pressures are reduced. A new stress/poroelasticity model resolves this paradox theoretically, but remains experimentally untested. P. Segall, "Earthquakes triggered by fluid extraction," Geology, 17, 942-6, October 1989. (U.S. Geological Survey, Menlo Park, Calif.; Stanford University, Calif.) If arrival times are supplemented by back-azimuth data, low-magnitude (3.0 to 5.0) seismic events can be located reasonably accurately using a small network of three-component seismographs with station separations of a few hundred kilometers (sparse network). Such a simple network near nuclear test sites should, therefore, be sufficient to monitor event locations for a test ban on low-yield explosions. S. Ballard, M.C. Walck, E.P. Chael, "Location performance of a sparse regional network," Geophysical Research Letters, 16, 1101-4, October 1989. (Sandia National Laboratories, Albuquerque) The greater the concentration of CO2 in the atmosphere, the greater is the maximum intensity of storms; and the greater the intensity of a storm, the greater is the thickness of the tempestites (storm beds) it produces. Other things being equal, tempestite thickness should therefore reflect atmospheric CO2 throughout geological time. Early analysis suggests that this is indeed the case and that, at a time when variations of atmospheric CO2 are of vital concern to all of us because of the greenhouse effect, tempestites offer a potential alternative method of determining past CO2 concentrations. D.S. Brandt, R.J. Elias, "Temporal variations in tempestite thickness may be a geologic record of atmospheric CO2," Geology, 17, 951-2, October 1989. (Eastern Michigan University, Ypsilanti; University of Manitoba, Winnipeg) Below depths of a few tens of kilometers in the earth's crust, conventional faulting is unlikely; and the causes of deeper earthquakes have long been a puzzle. However, experiments on metastable Mg2GeO4 olivine now suggest that some deep earthquakes could be the result of a particular form of faulting coinciding with the olivine-spinel transformation that occurs in the deep earth. H.W. Green II, P.C. Burnley, "A new self-organizing mechanism for deep-focus earthquakes," Nature, 341, 733-7, 26 October 1989. (University of California, Davis) Department of Chemistry University of Texas Austin The first of three back-to-back articles presenting a new molecular mechanics force field describes the technique for calculating structures and energies, including heats of formation, conformational energies, and rotational barriers more accurately than earlier programs. The new force field specifically incorporates terms to better handle bond stretching, angle bending, torsion, torsion-stretch interactions, torsion-bend interactions, bend-bend interactions, van der Waals interactions, electrostatics, and rotational barriers. N.L. Allinger, Y.H. Yuh, J.-H. Lii, "Molecular mechanics. The MM3 force field for hydrocarbons. 1.," Journal of the American Chemical Society, 111, 8551-66, 8 November 1989. (University of Georgia, Athens) A concise summary of a workshop on future directions for solar energy research defines desirable device characteristics for conventional solar cells and biocompatible ultrathin cells. Also considered are the relative merits of organic and inorganic semiconductors, monolayer and multilayer active assemblies, and the design of static concentrators. J.R. Bolton, G. Calzaferri, A. Goetzberger, T.J. Schaafsma, G.T. Wrixon, "Long-range photovoltaic R&D concepts," Chimia, 43, 215-7, July-August 1989. (University of Western Ontario, London; Institut fur Anorganische, Analytische und Physikalische Chemie der Universit„t, Bern, Switzerland; Fraunhofer-Institut fur Solare Energiesysteme, Freiburg, W.Ger.; Landbouw Universiteit Wageningen, The Netherlands; University College, Cork, Ireland) Included in a series of articles on alkane activation and functionalization is a comparison of thermal and photochemical routes for specific activation in highly functionalized organic molecules. C.L. Hill, R.F. Renneke, L.A. Combs, "Catalytic functionalization of unactivated saturated C - H bonds in the presence of alcohol, ester, and ketone functional groups," New Journal of Chemistry, 13, 701-6, October-November 1989. (Emory University, Atlanta) The title compounds can distinguish between enantiomeric ammonium ions in a process whereby stereoselectivity parallels free energy differences encountered in partitioning between water and dichloroethane. X-ray structures of such complexes allow for the construction of diamond-lattice sectors, from which useful prediction of stereoselectivity and enantioselectivity in such salts can be made. V. Prelog, M. Kovacevic, M. Egli, "Lipophilic tartaric acid esters as enantioselective ionophores," Angewandte Chemie, International Edition in English, 28, 1147-52, 1 September 1989. (Eidgen”ssichen Technischen Hochschule, Zurich, Switzerland) School of Natural Sciences Institute for Advanced Study Princeton, N.J. Einstein's depiction of general relativity is a remarkable and beautiful theory, but the central dynamical object in it - the space-time metric - looks disturbingly different from the other fields, particularly gauge fields, that are woven into the fundamental theories of physics. The metric has also proved very difficult to interpret or use in quantum theory. For these reasons, there has long been interest in constructing general relativity, or something that reduces to it in an appropriate limit, using radically different variables. Recently, there has been considerable progress with one approach, using the so-called Ashtekhar variables. R. Capovilla, T. Jacobson, J. Dell, "General relativity without the metric," Physical Review Letters, 63, 2325-8, 20 November 1989. (University of Maryland, College Park; Thomas Jefferson High School for Science and Technology, Alexandria, Va.) The classic technique for determining the three-dimensional structure of crystals and macromolecules, X-ray crystallography, is plagued by a fundamental mathematical ambiguity - the notorious "phase problem." It arises because it is only practical to measure the intensity of the scattered X-rays, whereas the standard mathematical technique of Fourier inversion requires information on the phase as well. Nevertheless, it has proved possible, by using a number of tricks and constraints from the physical nature of molecules, to determine rather elaborate structures. An accessible and informative introduction, by one of the great modern practitioners, is presented. H.A. Hauptmann, "The phase problem of X-ray crystallography," Physics Today, 42, 24-9, November 1989. (Medical Foundation of Buffalo, N.Y.) A rich scientific payoff - including dramatic improvements in X-ray astronomy, precision nuclear spectroscopy and áá decay experiments, low-energy experiments, and low-energy neutrino and dark matter detection - awaits the development of a new generation of detectors, capable of measuring the energy deposited not only by the classic ionization processes, but also acoustically (in phonons) by particles moving through matter. With this in mind, several groups around the world have been working toward developing ultralow temperature devices with the required sensitivity. Important progress in this area is reported. H. Kraus, F. von Feilitzsch, J. Jochum, R.L. M”ssbauer, et al., "Quasiparticle trapping in a superconductive detector system exhibiting high energy and position resolution," Physics Letters B, 231, 195-202, 2 November 1989. (Technische Universit„t Munchen, W.Ger.) Finally, I would like to mention a paper developing the theory of anyon superconductivity. B.I. Halperin, J. March-Russell, F. Wilczek, "Consequences of time-reversal-symmetry violation in models of high-Tc superconductors," Physical Review B, 40, 8726-44, 1 November 1989. (Harvard University, Cambridge, Mass.; Institute for Advanced Study, Princeton, N.J)

Life Science

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