Articles Alert

The Scientist has asked a group of expert. to periodically comment upon recent articles that they have found noteworthy. Their selectIons, presented here in every issue, are neither endorsements of content nor the result of systematic searching. Rather they are personal choices of articles they believe the scientific community as a whole may also find i.nteresting. Reprints of any articles cited here may be ordered through The Genuine Article, 8501 Market St., Philadelphia, Pa. 19004. BY SOKRATES T. PANTELIDES IBM Research Division Thomas J. Watson Research Center Yorktown Heights, N.Y. "The search for the mechanism that drives high-temperature superconductivity is moving on. A recent article discusses novel ideas about spin ordering leading to holes trapped in “bags” and hole pairing by sharing a bag. J.R. Schrieffer, X.-G. Wen, S.-C. Zhang, “Spin-bag mechanism of high-temperature superconductivity,” Physical Review Letters, 60,944-7,1988. "By probing the electrical and magnetic properties of grain boundaries and the adjoining grains, progress has been attained in understanding how to control the critical current density which is a key property for potential applications of superconductors. P. Chaudhari, J. Mannhart, D. Dimos, C.C. Tsuei, J. Chi, M.M. Oprysko, M. Scheuermann, “Direct measurement of the superconducting properties of single grain boundaries in YlBa2Cu3O7delta,” Physical Review Letters, 60, 1653-6, 1988. " Scanning tunneling microscopy does it again! It is possible to look at the reactivity of individual atoms on a surface, charge transfers from site to site, and their effect on reactivity. R. Wolkow, P. Avouris, “Atom-resolved surface chemistry using scanning tunneling microscopy,” Physical Review Letters, 60, 1049-52, 1988. "Examination of impurities at moving solid-solid phase boundaries has turned up interesting non-equilibrium phenomena in a previously unexplored regime. J.M. Poate, J. Linnros,.F. Priolo, D.C. Jacobson, J.L. Batstone, M.O. Thompson, “Non-equilbrium segregation and trapping phenomena during ion-induced crystallization of amorphous Si,” Physical Review Letters, 60, 1322-5, 1988. "Gas-source molecular beam epitaxy (MBE) has been a hot new number for III-v compound semiconductors, especially phosphides, but not silicon. Use of disilane makes gas-source MBE competitive with conventional solid-source silicon MBE, but probably not with ultra high vacuum chemical vapor deposition (see e.g. Meyerson et al., Applied Physics Letters, 50, 113, 1987), which also uses a gas source but not in beam form. H. Hirayama, T. Tataumi, N. Aizaki, “Gas-source silicon molecular beam epitaxy using disilane,” Applied Physics Letters, 52, 1484-6,1988. BY FRANCISCO J. AYALA Departmentof Ecology and Evolutionary Biology The University of California, Irvine Irvine, Calif. " An evolutionary tree derived from the nucleotide sequence in two DNA regions suggests that human immunodeficiency viruses types 1 (HIVI) and type 2 (HIV2, recently isolated from a West African AIDS patient) diverged more than 200 years ago. HIV1 strains isolated in the U.S. and France diverged over the last 20 years, having originated from Central African strains no more than 50 years ago. S.Yokoyama, L. Chung, T. Gojobori, “Molecular evolution of the human immunodeficiency and related viruses,” Molecular Biology and Evolution, 5, 237-51, 1988. "Oxygen is the principal agent responsible for the deterioration of organic materials exposed to air. Higher plants have their own coping mechanism enzymes and other components that act as antioxidants by inhibiting or quenching reactive oxygen. R.A. Larson, “The antioxidants of higher plants,” Phytochemistry, 27,969-78, 1988. "The social organization of many primates includes persistent dominance relationships among individuals. Typically, the higher the rank the greater the number of progeny. A recent study shows that the rank and reproductive success of sons are strongly correlated with their mother’s—but not their father’s—rank. D.G. Smith, S. Smith, “Parental rank and reproductive success of natal rhesus males,” Animal Behavior, 36,554-62,1988. "The platypus is better than many placental mammals at regulating its body temperature. It also has surprising specializations such as a bill that serves as a food-finding antenna: it bears receptors for the weak electric fields that are generated by the aquatic invertebrates on which the platypus feeds. M. Griffiths, “The platypus,” Scientific American, 258(5), 84-91, 1988. " Psr (paternal sex ratio) is the most extreme among the genetic elements labeled “selfish”: it ensures its own transmission from generation to generation by causing the elimination of all other chromosomes with which it becomes associated. U. Nur, J.H. Werren, D.G. Eickbush, WD. Burke, T.H. Eickbush, “A “selfish” B chromosome that enhances its transmission by eliminating the paternal genome,” Science, 240, 512-4, 1988. " Polymorphisms in DNA sequences allow identifying unambigously the individual from whom the DNA sequence was derived. A single human hair is sufficient for typing a polymerase chain reaction amplifies the DNA in vitro from as little as a single molecule. R. Higuchi, C.H. von Beroldingen, G.F. Sensabaugh, HA. Erlich, “DNA typing from single hairs,” Nature, 332, 543-6, 1988. BY PETER J. SMITH Department of Earth Sciences The Open University Milton Keynes, U.K. " Natural glass is unstable in wet, low temperature conditions, and yet 1.1-billion-year-old glass has now been found in Canada. Does this Precambrian material owe survival to composition or to an unlikely long-term dry environment? H.C. Palmer, K. Tazaki, WS. Fyfe, Z. Zhou, “Precambrian glass,” Geology, 16, 221-4, 1988. "New, more precise paleomagnetic results for the Ordovician, Silurian, and Devonian periods offer better agreement with paleoclimatologic and biogeographic data and provide more accurate Paleozoic reconstructions for North America, Gondwana and terranes between. R. Van der Voo, “Paleozoic paleogeography of North America, Gondwana, and intervening displaced terranes: Comparisons of paleomagnetism with paleoclimatology and biogeographical patterns,” Geological Society of America Bulletin, 100, 311-24, 1988. "The tantalizing possibility that the comparatively small gravitational forces exerted on the Earth by the Moon and Sun might trigger large earthquakes has been around for decades. A detailed statistical analysis now shows there may be some truth in it. J.H. Shirley, “Lunar and solar periodicities of large earthquakes: Southern California and the Alaska-Aleutian Islands seismic region,” Geophysical Journal, 92, 403-20, 1988. "Model studies suggest that tectonic plate motion is episodic. An insulating supercontinent causes mantle overheating below, which fragments the supercontinent. The fragments (continents) then drift and ultimately reaggregate over cold downwelling mantle where the overheating begins all over again. M. Gurnis, “Large-scale mantle convection and the aggregation and dispersal of supercontinents,” Nature, 332, 695-99, 1988. "The C-14/C ratio in Mono Lake, California, has increased by 60% since 1957. No natural process (including the absorption of bomb-produced 0-14 from the atmosphere) can explain it. Someone must have dumped radioactive carbon into the lake. But who? WS. Broecker, R Wanninkhof, G. Mathieu, T-H. Peng, S. Stine, S. Robinson, A. Herczeg, M. Stuiver, “The radiocarbon budget for Mono Lake: an unsolved mystery” Earth and Planetary Science Letters, 88,16-26,1988. "Geomorphic evidence shows that drought and high rainfall have alternated in the African Sahel for thousands of years. The current desertification is thus probably not permanent, although the potential of the area for economic recovery is by no means clear. P.A . Jacobberger, “Drought-related changes to geomorphologic processes in central Mali,” Geological Society of America Bulletin, 100,351-61,1988. BY BERNARD DIXON European Editorial Office The Scientist Uxbridge, U.K. "The beginning of the end of classical molecular biology may be marked by new insight into the “second genetic code” which governs the coupling between amino acids and their respective transfer RNA molecules. Y.M. Hou, P. Schimmel, “A simple structural feature is a major determinant of the identity of a transfer RNA,” Nature, 333, 140-5, 1988. "Danish virologists at the University of Arhus have developed a tagged replication-competent murine leukemia virus, easily detectable when integrated in the mouse cell genome. It facilitates study of the interactions between proviral and host DNA and distinguishes endogenous retroviral sequences and newly integrated provirus. P. Jorgensen, T. Mikk, F.S. Pederesen, N.O. Kjeldgaard, “A MuLV transmission vector system designed to permit recovery in E. coli of proviral and cellular flanking sequences,” Virus Genes, 1,221-33,1988. "Contrary to textbook assurances, 5% alcohol (often used as a co-solvent in pharmaceutical and other preparations) increases the inhibitory activity of several widely used antimicrobial agents against three common bacteria. T.J. McCarthy, A. van Eeden, N. Stephenson, C. Newman, “Interaction between ethanol and selected antimicrobial preservatives,” south African Journal of Science, 84, 128-30, 1988. Microencapsulation of cells, protein crystallization, and the design of fermenters and bioreactors to operate in conditions of microgravity are just three of the developments covered in a recent review of prospective biotechnology beyond the confines of planet Earth. R. Boudreault, D.W Armstrong, “Space biotechnology Current and future perspectives," Trends in Biotechnology, 6,91-5, 1988 "It is now becoming clear that AIDS may possibly be inducible in individuals carrying HIV if they are exposed to high levels of sunlight. This extends past observations that ultraviolet light can activate latent proviruses. K. Valerie, A. Delers, C. Bruck, C. Thiriart, H. Rosenberg, C. Debouck, M. Rosenberg, “Activation of human iminunodeficiency virus type 1 by DNA damage in human cells,” Nature, 333,18-81,1988. " Wholly negative findings can be as significant as the reverse, as in the elimination of one previously suspected group of endogenously produced substances as promoters of human bladder cancer. A.G. Renwick, A. Thakrar, CA. Lawrie, C.F. George, “Microbial amino acid metabolites and bladder cancer No evidence of promoting activity in Man,” Human Toxicology, 7, 267-72, 1988. MARYE ANNE FOX Department of Chemistry The University of Texas, Austin Austin, Tex. "Advances in photosynthesis research have stimulated extensive investigation, both experimental and theoretical, of electron transfer. A recent review discusses the effect of distance, thermicity, and orientation on the rates of intramolecular electron transfer. G.L Closs, J.R. Miller, “Intramolecular long-distance electron transfer in organic molecules,” Science, 240,440-7,1988. "Asymmetric routes to chiral organic molecules via nonenzymatic means has long been an important goal in organic synthesis. There has been considerable progress lately in the development of catalysts and transition state models for enantioselective reactions in carbonyl compounds. D.A. Evans, “Stereoselective organic reactions: Catalysts for n-carbonyl addition processes,” Science, 240, 420-6, 1988. " Redox enzymes often do not directly transfer electrons at poised electrodes because of the separation between the redox center and the electrode surface exceeds, even at closest approach, the distance required for fast electron transfer. Y. Degani, A. Heiler, “Direct electrochemical communication between chemically modified enzymes and metal electrodes. Method for bonding electron transfer relays to glucose oxidase and D-amino acid oxidase,” Journal of the American Chemical Society, 110,2615-20, 1988. " Ultramicroelectrodes solve many problems inherent with conventional electrochemical techniques. A recent article reviews their construction and operation, especially regarding problems with diffusion, ohmic drop, and voltammetry. R.M. Wightman, “Voltammetry with microscopic electrodes in new domains,” Science 240,415-20, 1988. " Both chemists and biologists are concentrating on the development of tailor-made catalysts, which permit efficient synthesis and modification of complex molecules and offer a better understanding of molecular ipteractions in ligand binding and catalysis. P.G. Schultz, ‘The interplay between chemistry and biology in the design of enzymatic catalysts,” Science, 240, 426-33,1988. " The concept of “function through organization”to simulate cellular processes or to attain useful material properties in polymeric liquid crystals was recently examined, with particular attention to the structure of several model membrane systems. H. Ringsdorf, B. Schlarb, J. Venzmer, “Molecular architecture and function of polymeric oriented systems: Models for the study of organization, surface recognition, and dynamics of biomembranes,” Angewandte Chemie, International Edition, 27, 113-58, 1988.

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