Articles Alert

The Scientist has asked a group of experts to comment periodically upon recent articles that they have found noteworthy. Their selections, presented herein every issue, are neither endorsements of content nor the result of systematic searching. Rather, the list represents personal choices of articles the columnists believe the scientific community as a whole may also find interesting. Reprints of any articles cited here may be ordered through The Genuine Article, 3501 Market St., Philadelphia, Pa. 19104, or by telephoning (215) 386-4399. Department of Microbiology & Immunology University of Illinois Chicago History shows that scientific misconduct is no more widespread now than over the past 150 years. Yet, charges and punishment are greater today, when every problem demands a solution - and accusation becomes reality. A distinguished group has produced a sensible, readable statement on the nature of scientific investigation and the social mechanisms (and their abuses) involved. Committee on the Conduct of Science, National Academy of Sciences, "On being a scientist," PNAS, 86, 9053-74, December 1989. (National Academy of Sciences, Washington, D.C.) Monoclonal antibodies revolutionized basic and applied immunology. A proposal to make animals obsolete in the production of monoclonals is made. Researchers would select directly from a bacteriophage library of mouse partial genes cloned with a bacterial promoter (and export signal sequences), for functional Fab combinations of both light and heavy chain variable regions. W.D. Huse, L. Sastry, S.A. Iverson, A.S. Kang, et al., "Generation of a large combinatorial library of the immunoglobulin repertoire in phage lambda," Science, 246, 1275-81, 8 December 1989. (Scripps Clinic, La Jolla, Calif.; The University, Sheffield, England; et al.) The complex folded cloverleaf-shaped transfer RNA must recognize its cognate amino acid-specific activating enzyme by a lock-and-key fit between the two molecules. From the co-crystal structure (by X-ray diffraction analysis), it can be seen that contact occurs along the entire length of the tRNA, with the anticodon buried deeply in the protein and the other end (the aminoacyl activating site and ATP) fitting into a different domain of the protein. Three mutant glutamyl-tRNA synthetases (with changes near the aminoacylation site) mis-acylate a tryosine suppressor tRNA with glutamine. M.A. Rould, J.J. Perona, D. Süll, T.A. Steitz, "Structure of E. coli glutaminyl-tRNA synthetase complexed with tRNAGln and ATP at 2.8 Angstrom resolution," Science, 246, 1135-42, 1 December 1989. (Yale University, New Haven, Conn.) J.J. Perona, R.N. Swanson, M.A. Rould, T.A. Steitz, D. Süll, "Structural basis for misaminoacylation by mutant E. coli glutaminyl-tRNA synthetase enzymes," Science, 246, 1152-4, 1 December 1989. (Yale University, New Haven, Conn.) Pneumocystis carinii pneumonia often kills AIDS victims. Patients treated with standard anti-P. carinii agents suffer from toxic and allergic side effects, and it is obvious that new compounds are desperately needed. Now, the cloning and sequencing of a key gene from P. carinii opens the possibility of improved chemotherapy with trimethoprim-related antibiotics. J.C. Edman, U. Edman, M. Cao, B. Lundgren, et al., "Isolation and expression of the Pneumocystis carinii dihydrofolate reductase gene," PNAS, 86, 8625-9, November 1989. (University of California, San Francisco; National Institutes of Health, Bethesda, Md.) Meiosis, the central genetic process for sexually reproducing organisms, is being picked apart by genetic analysis, followed by molecular biology and biochemistry. A new mutational block has been identified that prevents meiosis but has no effect on mitotic division. T.M. Menees, G.S. Roeder, "MEI4, a yeast gene required for meiotic recombination," Genetics, 123, 675-82, December 1989. (Yale University, New Haven, Conn.) Cell-targeted toxins, constructed by fusion of a specific cell-surface receptor with a bacterial toxin, are some of the more promising creations of recombinant DNA shuffling. Here, the cell recognition domain of mammalian transforming growth factor alpha was fused in front of the membrane translocating and elongation factor-inactivating domains of a bacterial toxin, to form a protein that is highly toxic for tumor cells. C.B. Siegall, Y.-H. Xu, V.K. Chaudhary, S. Adhya, et al., "Cytotoxic activities of a fusion protein comprised of TGFà and Pseudomonas exotoxin," The FASEB Journal, 3, 2647-52, December 1989. (National Institutes of Health, Bethesda, Md.) Department of Earth Sciences Open University Milton Keynes, U.K. The popular theory that both the moon and the high angular momentum of the earth-moon system are the result of the impact of a single Mars-sized planetesimal on the growing earth is implausible. The process has a low dynamic probability, the collision would have produced terrestrial geochemical signatures different from those observed, and the moon would have been derived from the impactor (whereas it appears to have been derived from the earth's mantle). It is much more likely that the high angular momentum was produced by a large impact late in the earth's accretion, and that the moon accreted separately from material ejected from the earth by lesser impacts. A.E. Ringwood, "Flaws in the giant impact hypothesis of lunar origin," Earth and Planetary Science Letters, 95, 208-14, November 1989. (Australian National University, Canberra) Sedimentary basins in stable continental regions (sag basins) can be explained simply by downward convection in the underlying asthenosphere followed by cessation of the descending plume. This new model is the only one that explains both the origin and all the development characteristics of sag basins. M.F. Middleton, "A model for the formation of intracratonic sag basins," Geophysical Journal International, 99, 665-76, December 1989. (Geological Survey of Western Australia, Perth) The oblateness of planets can be estimated using a simple formula involving only spin rate, polar radius, and planetary mass. The oblatenesses thus predicted agree with observation. Moreover, the formula indicates that, assuming the mass and volume of the earth have remained constant, the earth's equatorial radius has decreased by 2 km, and its polar radius has increased by 4.1 km over the past 500 million years. L. Fraiture, "Planetary oblateness and evolution of earth flattening," Geophyiscal Journal International, 99, 561-5, December 1989. (European Space Agency, Darmstadt, W.Ger.) Heat flow variations in the vicinity of oceanic ridges are usually attributed to hydrothermal circulation in the crust and have been used to deduce the scale and pattern of the circulation. However, at the Juan de Fuca Ridge, where hydrothermal circulation is undoubtedly taking place, the heat flow variations result only from sediment thickness variation. In short, where sediment thickness varies it is dangerous to infer circulation patterns from variations in observed heat flow. E.E. Davis, D.S. Chapman, C.B. Forster, H. Villinger, "Heat-flow variations correlated with buried basement topography on the Juan de Fuca Ridge flank," Nature, 342, 533-7, 30 November 1989. (Department of Energy, Mines and Resources, Sidney, British Columbia; University of Utah, Salt Lake City; Alfred Wegener Institute, Bremerhaven, W.Ger.) The brief, massive release of high-temperature hydrothermal fluid ("megaplume") at the Juan de Fuca Ridge recently reported by Baker, Massoth, and Feely (Nature, 329, 149-51, 10 September 1987) is not unique. A similar, large, transient plume has been observed (and confirmed by a second visit almost a year after the first trip) at the North Piji Basin spreading axis. The discovery of megaplumes in two different tectonic environments suggests that such plumes may be common and thus make an important contribution to global thermal and chemical fluxes from the mid-ocean ridges. Y. Nojiri, J-i. Ishibashi, T. Kawai, A. Otsuki, H. Sakai, "Hydrothermal plumes along the North Fiji Basin spreading axis," Nature, 342, 667-70, 7 December 1989. (National Institute for Environmental Studies, Ibaraki, Japan; University of Tokyo) Analysis of data from 1987 shows that from mid-August to late September there was an ozone deficiency beyond the area of the Antarctic ozone hole. The geographic extent of ozone depletion is thus greater than previously supposed, and the loss started earlier in the year than suspected. The extent and intensity of these decreases are of well-known global concern. M.H. Proffitt, D.W. Fahey, K.K. Kelly, A.F. Tuck, "High-latitude ozone loss outside the Antarctic ozone hole," Nature, 342, 233-7, 16 November 1989. (NOAA Aeronomy Laboratory, Boulder, Colo.; University of Colorado, Boulder) Department of Chemistry University of Texas Austin The Commission on Physical Organic Chemistry of the International Union of Pure and Applied Chemistry has proposed a set of recommendations for naming reaction mechanisms. This computer-retrievable set is suggested as an alternative to the Ingold classification, which describes the observed properties of an organic reaction, for example, as an SN2 reaction. This approach describes the number and sequence of bond-making and bond-breaking steps as primary delineators of reaction mechanism. R.D. Guthrie, W.P. Jencks, "IUPAC recommendations for the representation of reaction mechanisms," Accounts of Chemical Research, 22, 343-9, October 1989. (University of Kentucky, Lexington; Brandeis University, Waltham, Mass.) Highly vibrationally excited ground state molecules can be formed via internal conversion from the excited singlet state. A chemistry of hot molecules (denoted as S0**) based on reactivity, collisional relaxation, absorption line shape, and radiationless transitions is reviewed, and a new role for such species as intermediates in UV multiphoton dissociation is discussed. This mechanism is being held in new regard as a major pathway for UV-vacuum UV photochemistry of unsaturated hydrocarbons. N. Nakashima, K. Yoshihara, "Role of hot molecules formed by internal conversion in UV single-photon and multiphoton chemistry," The Journal of Physical Chemistry, 93, 7763-71, 16 November 1989. (Osaka University, Japan; Insitute for Molecular Science, Okazaki, Japan) The chemistry of dications is governed by the interplay of molecular bonding and inherent electron repulsion. Detailed descriptions of these intermediates are now available both from gas phase mass spectrometric measurements and from ab initio theory. K. Lammertsma, P. von Ragu‚ Schleyer, H. Schwarz, "Organic dications: gas phase experiments and theory in concert," Angewandte Chemie, International Edition in English, 28, 1321-41, October 1989. (University of Alabama, Birmingham; Universität Erlangen-Nürnberg, W.Ger.; Technischen Universität, Berlin) Site-directed mutagenesis makes possible the preparation of complex proteins with specific substitution patterns. Here a yeast cytochrome c variant with a surface histidine at residue 62 is used as a framework to study long-range donor-acceptor coupling involving covalent-bond, hydrogen-bond, and through-space interactions. Although this approach allows the pathway of strongest coupling to be determined, the mere presence of aromatic residues or polarizable sulfur atoms does not necessarily enhance electronic coupling. B.E. Bowler, T.J. Meade, S.L. Mayo, J.H. Richards, H.B. Gray, "Long-range electron transfer in structurally engineered pentaammineruthenium (Histidine-62)cytochrome c," Journal of the American Chemical Society, 111, 8757-9, 8 November 1989. (California Institute of Technology, Pasadena) Attempts to quantitatively account for ozone depletion in Antarctica via known photochemical processes have met with only limited success, and further new mechanisms are needed. The spectroscopy and photoproducts derived from OCIO photorearrangement show that atomic chlorine and O2 may form via a photodissociative pathway. V. Vaida, S. Solomon, E.C. Richard, E. Rühl, A. Jefferson, "Photoisomeriazation of OCIO: a possible mechanism for polar ozone depletion," Nature, 342, 405-8, 23 November 1989. (University of Colorado, Boulder; National Oceanographic and Atmospheric Administration, Boulder; Freie Universität Berlin, W.Ger.) The extensive use of plasma-assisted chemical etching and chemical vapor deposition in the fabrication of microelectronic devices has made it important to understand chemical details of the reactions of free radicals (as reactive intermediates and as constituents of plasmas) on surfaces. Experimental methods to investigate such reactions are described, and the results are used to construct a bond energy model for silicon surface reactions. J.I. Steinfeld, "Reactions of photogenerated free radicals at surfaces of electronic materials," Chemical Reviews, 89, 1291-302, September-October 1989. (Massachusetts Institute of Technology, Cambridge)

Articles Alert

Interested in reading more?

Become a Member of