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Department of Microbiology & Immunology University of Illinois Chicago Cosy, Noesy, and HoHaHa! Respectively, these are abbreviations for two-dimensional scalar correlated spectroscopy, two-dimensional nuclear Overhauser enhancement spectroscopy, and Homonuclear Hartmann Hahn transfer experiment - three of the techniques used to study Megasphaera elsdenii. Apparently, we need to learn well the general rules for two-dimensional nuclear magnetic resonance (NMR) determination of atomic connectivities and three-dimensional polypeptide structures. Assignment of the 1H NMR resonances of the 137 amino acid residues of flavodoxin is a good lesson as well as a careful example of the power of two-dimensional NMR structural determinations for noncrystalline proteins. C.P.M. van Mierlo, J. Vervoort, F. Müller, A. Bacher, "A two-dimensional 1H NMR study on Megasphaera elsdenii flavodoxin in the reduced state," European Journal of Biochemistry, 187, 521-41, February 1990. (Agricultural University, Wageningen, The Netherlands; Technical University of Munich) Many scientists are modeling membrane protein folding either with little understanding or with the knowledge that the predictions have a very limited basis. An update of such analysis (based on less than a handful of known membrane protein structures) is useful - until a more reasonable database becomes available. G.D. Fasman, W.A. Gilbert, "The prediction of transmembrane protein sequences and their conformation: an evaluation," Trends in Biochemical Sciences, 15, 89-92, March 1990. (Brandeis University, Waltham, Mass.; Whitehead Institute, Cambridge, Mass.) F. Jühnig, "Structure predictions of membrane proteins are not that bad," Trends in Biochemical Sciences, 15, 93-5, March 1990. (Max-Planck-Institut für Biologie, Tübingen, W.Ger.) Autophosphorylation of kinase proteins that respond to environmental signals followed by transphosphorylation from the histidine residue of the initial protein to an aspartate residue on a second signal transducing protein is a popular theme in bacterial gene regulation. A thorough review by the people who determined the crystal structure of CheY (representative of the second class of proteins) keeps us up to date. J.B. Stock, A.M. Stock, J.M. Mottonen, "Signal transduction in bacteria," Nature, 344, 395-400, 29 March 1990. (Princeton University, N.J.) The statement, "Most scientists regard Gaia as little more than metaphor," appears in a 25th-anniversary review of J.E. Lovelock's concept of the biosphere as a homeostatic self-stabilizing entity - as big as life on the planet itself. Of course, others think Gaia is worse than a metaphor (". . . some even denounce it as antiscience") because of its attractiveness to those given to soft mysticism. Lovelock considers Gaia a testable hypothesis; but whether metaphor, mystery, or hypothesis, it has become a useful way of viewing life on earth. J.E. Lovelock, "Hands up for the Gaia hypothesis," Nature, 344, 100-2, 8 March 1990. (University of Reading, England) Department of Biology King's College London, U.K. Humpback whales breed in the winter in shallow tropical seas and then migrate to their summer feeding grounds in high-latitude waters. Each different group has its own preference for particular breeding and feeding sites. A study of their populations has been undertaken using small skin samples on which DNA analyses have been conducted. The results show that populations are very regular in their migratory destinations; little genetic mixing occurs between groups. C.S. Baker, S.R. Palumbi, R.H. Lambertsen, M.T. Weinrich, et al., "Influence of seasonal migration on geographic distribution of mitochondrial DNA halotypes in humpback whales," Nature, 344, 238-40, 15 March 1990. (National Cancer Institute, Frederick, Md.; Smithsonian Institution, Washington, D.C.; University of Hawaii, Honolulu; et al.) The retreat of the Wisconsin ice sheet from North America not only permitted the shifting of vegetation belts, but also encouraged migration of the human occupants of the continent. These early movements are recorded in the geographical patterns of the 13 languages currently surviving. It is possible, on the basis of linguistic analysis, to reconstruct the pattern of movements. The geographical divisions are found to bear close resemblance to biogeographic zones. R.A. Rogers, L.D. Martin, T.D. Nicklas, "Ice-age geography and the distribution of native North American languages," Journal of Biogeography, 17, 131-43, March 1990. (University of Kansas, Lawrence; private contributor, Lawton, Okla.) The use of antiparasitic drugs in domestic cattle could have unexpected ecological side effects when the drugs are discharged from the animal into the environment. One broad-spectrum drug, ivermectin, persists in cattle feces where it inhibits the invasion of fly (Diptera) larvae. This has the effect of slowing down the process of decomposition, which could lead to long-term fouling of pasture lands. M. Madsen, B.O. Ni, P. Holter, O.C. Pedersen, et al., "Treating cattle with ivermectin: effects on the fauna and decomposition of dung pats," Journal of Applied Ecology, 27, 1-15, April 1990. (Royal Veterinary and Agricultural University, Frederiksberg, Denmark; University of Aarhus, Denmark; Unviersity of Copenhagen; et al.) Detailed studies on the seasonal growth pattern of oyster shells in the Chesapeake Bay are providing an intriguing insight into the feeding habits of the inhabitants of early human settlements of the area. Examination of discarded oyster shells from archaeological sites permits identification of the precise season in which they were harvested. In an Early Woodland Period site, 70 percent was collected in spring and summer, 20 percent in fall, and 10 percent in winter. J.F. Custer, K.R. Doms, "Analysis of microgrowth patterns of the American oyster (Crassostrea virginica) in the Middle Atlantic region of eastern North America: archaeological applications," Journal of Archaeological Science, 17, 151-60, March 1990. (University of Delaware, Newark) Department of Chemistry University of Pittsburgh Pittsburgh An elegantly designed molecule based on Kemp's triacid exhibits autocatalysis in its own replication. As in living systems, base pairing is indeed an essential feature of the pathway, and one can visualize how information is transmitted step-by-step from the structure of a nucleic acid to the synthesis of an amide bond. T. Tjivikua, P. Ballester, J. Rebek, Jr., "A self-replicating system," Journal of the American Chemical Society, 112, 1249-50, 31 January 1990. (Massachusetts Institute of Technology, Cambridge) Recent developments in the formation of glycosidic bonds show promise to make complex oligosaccharides more readily available. Strategic and practical improvements to a rapidly emerging route based on pent-4-enyl glycosides (NPGs) provide efficient stereoselective access to highly functionalized disaccharides that are poised for formation of the next glycosidic bond. P. Konradsson, D.R. Mootoo, R.E. McDevitt, B. Fraser-Reid, "Iodonium ion generated in situ from N-iodosuccinimide and trifluoromethanesulphonic acid promotes direct linkage of `disarmed' pent-4-enyl glycosides," Journal of the Chemical Society, Chemical Communications, 3, 270-2, 1 February 1990. (Duke University, Durham, N.C.) There are surprisingly few good methods available to convert amines into other functional groups. Transformations based on N-nitrosation now promise to provide a wide range of functional groups from amines under very mild conditions. This two-step conversion of primary amines via phosphoramidates to phosphotriesters is representative of such transformations. N. Nikolaides, B. Ganem, "New chemistry of amines. 2. A convenient synthesis of phosphotriesters from phosphoramidates," Tetrahedron Letters, 31 (8), 1113-16, 1990. (Cornell University, Ithaca, N.Y.) Triply hydrogen-bonded base pairs are known to be important subunits in nature, and are key design elements in some synthetic receptors. Sophisticated Metropolis Monte Carlo simulations (using statistical perturbation theory) provide an intuitively satisfying model to explain why the binding energies of several apparently similar complexes can vary so widely. From the model, one can readily design multiply hydrogen-bonded complexes in which the resulting association will be much stronger (or weaker) than the sum of the individual hydrogen bonds. W.L. Jorgensen, J. Pranata, "Importance of secondary interactions in triply hydrogen bonded complexes: guanine-cytosine vs. uracil-2,6-diaminopyridine," Journal of the American Chemical Society, 112, 2008-10, 28 February 1990. (Purdue University, West Lafayette, Ind.) Although it is well known that Cu(I) catalyses the conjugate addition of Grignard reagents to unsaturated ketones, Cu(II) is not generally believed to be useful. However, in the presence of trimethylsilyl chloride, Cu(II) salts are not reduced, but instead catalyze the addition of Grignard reagents to unsaturated esters. The resulting data from methods used in the study reflect rapid addition of Grignard reagents, and with excellent yields. H. Sakata, Y. Aoki, I. Kuwajima, "A remarkable catalytic effect of Cu(II) species for conjugate addition of Grignard reagents to à á-unsaturated esters," Tetrahedron Letters, 31 (8), 1161-4, 1990. (Tokyo Institute of Technology) IBM Research Division Thomas J. Watson Research Center Yorktown Heights, N.Y. The fractional quantum Hall effect was described theoretically some time ago, but its relationship to the integer Hall effect has been rather elusive. A new theory by Jain, Kivelson, and Trivedi bridges the gap. The theory was motivated by unpublished experimental data, reported by Engel, Wei, Tsui, and Shayegan, at the Eighth International Conference on Electronic Properties of Two-Dimensional Systems, held in Grenoble, France, in 1989. J.K. Jain, S.A. Kivelson, N. Trivedi, "Scaling theory of the fractional quantum Hall effect," Physical Review Letters, 64, 1297-1300, 12 March 1990. (State University of New York, Stony Brook; University of California, Los Angeles) For many years, III-V semiconductors and alloys proved to yield a plethora of innovative transistors. Nowadays, mixing Ge in Si, by either molecular beam epitaxy (MBE) or chemical vapor deposition (CVD), is making possible comparable Si-based devices, featuring a controllable negative differential resistance in the collector current. A recent paper reports a SiGe resonant tunneling hot-carrier transistor. Don't ever count Si out! S.S. Rhee, G.K. Chang, T.K. Carns, K.L. Wang, "SiGe resonant tunnelling hot-carrier transistor," Applied Physics Letters, , 1061-3, 12 March 1990. (University of California, Los Angeles) The debate on Fermi-level pinning at semiconductor-metal interfaces has focused so much on interface and defect states that hydrogenation is an obvious desirable probe. It's happening - the experimental results are intriguing - but understanding is still elusive. Y.Q. Jia, G.G. Qin, "Effects of hydrogen on Al/p-Si Schottky barrier diodes," Applied Physics Letters, 56, 641-3, 12 February 1990. (Peking University, Beijing; Academia Sinica, Shenyang, China) Measured hyperfine parameters have often led to unambiguous identification of defects in semiconductors. A new report shows that first-principles calculations of hyperfine parameters is now possible and can unambiguously resolve ambiguities! C.G. Van de Walle, "Structural identification of hydrogen and muonium centers in silicon: first-principles calculations of hyperfine parameters," Physical Review Letters, 64, 669-72, 5 February 1990. (North American Phillips Corporation, Briarcliff Manor, N.Y.) There seems to be no end to new probes of individual atoms. A recent paper reports that femtosecond pulses can be used to "push" molecules in a molecular crystal along selected paths in the lattice, very much as one pushes a child on a swing. A.M. Weiner, D.E. Leaird, G.P. Wiederrecht, K.A. Nelson, "Femtosecond pulse sequences used for optical manipulation of molecular motion," Science, 247, 1317-19, 16 March 1990. (Bell Communications Research, Red Bank, N.J.; Massachusetts Institute of Technology, Cambridge)

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