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Department of Microbiology & Immunology University of Illinois Chicago A surface glycoprotein that is anchored via a lipid to the trypanosome cell membrane is transferred in vitro to red blood cell membranes, sensitizing the latter to attack by anti-trypanosome antibodies. M.R. Rifkin, F.R. Landsberger, "Trypanosome variant surface glycoprotein transfer to target membranes: a model for the pathogenesis of trypanosomiasis," PNAS, 87, 801-5, January 1990. (Rockefeller University, New York) Gene fusions encoding reporter enzymes such as alkaline phosphatase and á-galactosidase are a means for following the twisting of membrane proteins back and forth across the bacterial cell membrane. A review and new transposons developed for this technique should extend its utility. C. Manoil, J.J. Mekalanos, J. Beckwith, "Alkaline phosphatase fusions: sensors of subcellular location," Journal of Bacteriology, 172, 515-18, February 1990. (University of Washington, Seattle; Harvard Medical School, Boston) C. Manoil, "Analysis of protein localization by use of gene fusions with complementary properties," Journal of Bacteriology, 172, 1035-42, February 1990. (University of Washington, Seattle) Solutions to some problems of molecular biology have progressed slowly but with an elegance that equals or exceeds "hot" breakthroughs. The structure for initiation and progression of DNA replication is one such complex and elegant process. The DnaA protein, complexed with ATP, associates with the chromosomal origin of replication oriC. This opens up the complex to allow the next protein, DnaB, to enter. B.Y.M. Yung, E. Crooke, A. Kornberg, "Fate of the DnaA initiator protein in replication at the origin of the Escherichia coli chromosome in vitro," Journal of Biological Chemistry, 265, 1282-5, 25 January 1990. (Stanford University, Calif.) Unusual amino acids might (in principle) be incorporated into polypeptides by special tRNAs or at any subsequent step, including post-translational enzymatic modification. To incorporate selenocysteine, serine - which is already attached to the unique tRNA - is enzymatically converted to selenocysteine and then incorporated into the growing polypeptide chain. W. Leinfelder, K. Forchhammer, B. Veprek, E. Zehelein, A. B”ck, "In vitro synthesis of selenocysteinyl-tRNAUCA from seryl-tRNAUCA: involvement and characterization of the selD gene product," PNAS, 87 (2), 543-7, January 1990. (Universit„t München, W.Ger.) Sickle cell anemia remains basically untreatable nearly two generations after its molecular basis was established. A newly engineered system of anemic mice with human sickle cell hemoglobin in their erythrocytes provides an animal model for use in developing effective drugs. T.M. Ryan, T.M. Townes, M.P. Reilly, T. Asakura, et al., "Human sickle hemoglobin in transgenic mice," Science, 247, 566-8, 2 February 1990. (University of Alabama, Birmingham; University of Washington, Seattle; University of Pennsylvania, Philadelphia) Department of Earth Sciences Open University Milton Keynes, U.K. In recent years, hydrothermal activity at oceanic ridges has come to be seen as an important source of seawater minerals. However, the process can also go the other way. The locations of positive and negative phosphorus anomalies near the Juan de Fuca Ridge suggest that hydrothermal processes are removing phosphorus from seawater by the sorption of phosphate onto newly formed hydrous iron oxides. About 12 percent of the total annual phosphorus input to the oceans could be scavenged in this way. R.A. Feely, G.J. Massoth, E.T. Baker, J.P. Cowen, et al., "The effect of hydrothermal processes on midwater phosphorus distributions in the northeast Pacific," Earth and Planetary Science Letters, 96, 305-18, January 1990. (National Oceanic and Atmospheric Administration, Seattle; University of Hawaii, Honolulu; University of Washington, Seattle) Calculations show that the thermal radiation generated by the ballistic re-entry of ejecta condensed from the vapor plume of a bolide impact at the Cretaceous-Tertiary (K/T) boundary would have increased the global radiation flux by a factor of 50 to 150 for up to several hours. This would have been sufficient to ignite global wildfires and, hence, would account for the layer of soot recently found at the boundary. H.J. Melosh, N.M. Schneider, K.J. Zahnle, D. Latham, "Ignition of global wildfires at the Cretaceous/Tertiary boundary," Nature, 343, 251-4, 18 January 1990. (University of Arizona, Tucson; NASA Ames Research Center, Moffett Field, Calif.; U.S. Forest Service, Missoula, Mont.) Sublimates from hot-spot volcano Piton de la Fournaise (Reunion Island) contain detectable amounts of iridium, evidently released as a volatile fluoride compound. This strengthens the view that the earth's interior, rather than a bolide impact, could be the source of iridium at the K/T boundary. J.-P. Toutain, G. Meyer, "Iridium-bearing sublimates at a hot-spot volcano (Piton de la Fournaise, Indian Ocean)," Geophysical Research Letters, 16, 1391-4, December 1989. (Observatorio Vesuviano, Naples, Italy; Centre Etudes Nucleaires/Saclay and Institut de Physique du Globe de Paris) Since December 1977, the 3He/4He ratio in the atmosphere has been decreasing at an average annual rate of about 10-9. The most likely cause is the addition of 4He to the atmosphere by human activity - chiefly natural gas production, but also including oil and coal production, mineral exploitation, and groundwater withdrawal. Y. Sano, H. Wakita, Y. Makide, T. Tominaga, "A ten-year decrease in the atmospheric helium isotope ratio possibly caused by human activity," Geophysical Research Letters, 16, 1371-4, December 1989. (University of Tokyo) Log-log plots of the ratio H/L (height of drop/length of run-out) against volume for dry landslides on earth and landslides on Valles Marineris on Mars are linear and have the same gradient, but they are not coincident. The offset between the two indicates that a Martian avalanche must be almost 100 times more voluminous than a dry terrestrial one in order to achieve the same mobility. This result, combined with estimates of yield strengths (104 to 105 Pa), suggests that the Martian landslides are not water-saturated and thus do not, as some workers have suggested, indicate the presence of water on Mars at the time. A.S. McEwen, "Mobility of large rock avalanches: evidence from Valles Marineris, Mars," Geology, 17, 1111-14, December 1989. (U.S. Geological Survey, Flagstaff, Ariz.) Department of Chemistry University of Texas Austin Bomb calorimetry has provided much of the useful thermodynamic data on bond strengths in organic molecules. An alternative method is presented for measuring heats of heterolysis from the heats of recombination of organic cations and anions in solution. These data lead to accurate bond homolysis energies when combined with electron transfer energies. E.M. Arnett, K. Amarnath, N.G. Harvey, J.P. Cheng, "Chemical bond-making, bond-breaking, and electron transfer in solution," Science, 247, 423-30, 26 January 1990. (Duke University, Durham, N.C.) Diamonds 3 to 5 nanometers in size are found naturally in meteorites, in carbonaceous residues of detonations, in gas phase nucleations, and as films grown under low pressures of hydrogen. Structures smaller than about 3 nanometers are energetically favored over polycyclic aromatics (precursors to graphite). This implies that surface energies are important in stabilizing these microcrystalline clusters. P. Badziag, W.S. Verwoerd, W.P. Ellis, N.R. Greiner, "Nanometre-sized diamonds are more stable than graphite," Nature, 343, 244-5, 18 January 1990. (University of South Africa, Pretoria; Los Alamos National Laboratory, N.M.) Defining interactions between distal sites in small rings continues to offer intriguing insights into bonding in organic molecules. Three approaches to 1,4 interactions in a fixed geometry are offered. D.A. Hrovat, W.T. Borden, "Ab initio calculations of the relative energies of 1,2-, 1,3-, and 1,4-dehydrocubane: prediction of dominant through-bond interaction in 1,4-dehydrocubane," Journal of the American Chemical Society, 112, 875-6, 17 January 1990. (University of Washington, Seattle) P.E. Eaton, J. Tsanaktsidis, "The reactions of 1,4-dihalocubanes with organolithiums. The case for 1,4-cubadiyl," JACS, 112, 876-8, 17 January 1990. (University of Chicago) K. Hassenrück, J.G. Radziszewski, V. Balaji, G.S. Murthy, et al., "A body-diagonal bond in cubane: Can it be introduced?" JACS, 112, 873-4, 17 January 1990. (University of Texas, Austin) As a complement to picosecond transient spectroscopy and theory, studies of photosynthetic reaction centers - as perturbed by external electrical and magnetic fields - provide sensitive probes for energetics and dynamics. Recent results are summarized, and methods are considered to evaluate the occurrence of superexchange by a complete simulation of the electrostatic environment around putative intermediates. S.G. Boxer, R.A. Goldstein, D.J. Lockhart, T.R. Middendorf, L. Takiff, "Excited states, electron-transfer reactions, and intermediates in bacterial photosynthetic reaction centers," Journal of Physical Chemistry, 93, 8280-93, 28 December 1990. (Stanford University, Calif.) School of Natural Sciences Institute for Advanced Study Princeton, N.J. Measurements of the Z boson's lifetime give decisive information as to the possible existence of new species of light neutrinos, in addition to the three known ones (electron, muon, t lepton). Even though the neutrinos themselves are essentially undetectable, by comparing the actual Z decay rate to the decay rate from "known causes," one might see an indirect signal of their existence. Recent results strongly indicate that the three known neutrinos exhaust the list. This result is important to cosmology because the number of neutrino species affects the rate of expansion of the early universe, which is an ingredient in the calculation of element abundance in big-bang nucleosynthesis. (In addition to the text, there are more than three pages of authors' names, which must be some sort of record.) D. Decamp, B. Deschizeaux, J.-P. Lees, M.-N. Minard, et al., "A precise determination of the number of families with light neutrinos and of the Z boson partial widths," Physics Letters B, 235, 399-411, 1 February 1990. (Laboratoire de Physique des Particules, Annecy-le-Vieux, France; et al.) Quantum numbers used to be quantized. Lately, it is increasingly common to find numbers, once thought of as sacrosanct quantum numbers, indeed breaking into fractions. This is particularly common in two-dimensional condensed matter systems, in which fractional electric charge, and even fractional quantum statistics, have become central to the Hall effect theory. These are widely speculated to play a role in spin orderings (chiral spin states) and in high temperature (anyon) superconductivity. S.P. Benz, M.S. Rzchowski, M. Tinkham, C.J. Lobb, "Fractional giant Shapiro steps and spatially correlated phase motion in 2D Josephson arrays," Physical Review Letters, 64, 693-6, 5 February 1990. (Harvard University, Cambridge, Mass.) The burgeoning state of the art in scanning microscopy is well-summarized. R. Pool, "The children of the STM," Science, 247, 634-6, 9 February 1990. (AAAS, Washington, D.C.) How can a paper that opens, "A functioning human brain is a lump of warm wet matter of inordinate complexity," be resisted? It tackles, head-on, some of the classic "problems" of philosophy and psychology, by taking the point of view - the only defensible one, in my opinion - that until proved otherwise we should assume the laws of physics are adequate to describe all aspects of reality. It also isolates some of the key facts that really do need explaining. The paper makes a genuine contribution in a domain where the air is often both "thin and hot." M.J. Donald, "Quantum theory and the brain," Proceedings of the Royal Society of London, A427, 43-93, 8 January 1990. (University of Cambridge, England)

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