bluuebunny/crossref_metadata_2025 huggingface dataset:
The Role of Chinese Science and Technology in Economic Development
Authors: Zhu Lilan
Published: October 2006

The author discusses how science in China needs to meet two major challenges in economic development: strategic problems posed by the large population, and improving the country's scientific and technological infrastructure.
ATP-Sensitive K
+
Channels: Paradigm Lost, Paradigm Regained
Authors: Philipson Louis H.
Published: October 2006

In an update of a previous Perspective [L. H. Philipson and D. F. Steiner,
Science
268
, 372 (1995)], Philipson discusses the molecular basis for Ksubscript ATP, a potassium current that mediates glucose regulation of insulin secretion. A prediction in the previous Perspective is borne out by a paper in this issue of
Science
(Inagaki
et al.
,
p. 1166
), which reports the cloning of a new inward rectifier potassium channel and shows that Ksubscript ATP is formed when this channel combines with the sulfonylurea receptor.
A Carbon Nanotube Field-Emission Electron Source
Authors: de Heer Walt A. , Châtelain A. , Ugarte D.
Published: October 2006

A high-intensity electron gun based on field emission from a film of aligned carbon nanotubes has been made. The gun consists of a nanotube film with a 1-millimeter-diameter grid about 20 micrometers above it. Field-emission current densities of about 0.1 milliampere per square centimeter were observed for applied voltages as low as 200 volts, and current densities greater than 100 milliamperes per square centimeter have been realized at 700 volts. The gun is air-stable, easy and inexpensive to fabricate, and functions stably and reliably for long times (short-term fluctuations are on the order of 10 percent). The entire gun is only about 0.2 millimeter thick and can be produced with virtually no restrictions on its area, from less than 1 square millimeter to hundreds of square centimeters, making it suitable for flat panel display applications.
Prevention of SIV Infection in Macaques by (
R
)-9-(2-Phosphonylmethoxypropyl)adenine
Authors: Tsai Che-Chung , Follis Kathryn E. , Sabo Alexander , Beck Thomas W. , Grant Richard F. , Bischofberger Norbert , Benveniste Raoul E. , Black Roberta
Published: October 2006

The efficacy of pre- and postexposure treatment with the antiviral compound (
R
)-9-(2-phosphonylmethoxypropyl)adenine (PMPA) was tested against simian immunodeficiency virus (SIV) in macaques as a model for human immunodeficiency virus (HIV). PMPA was administered subcutaneously once daily beginning either 48 hours before, 4 hours after, or 24 hours after virus inoculation. Treatment continued for 4 weeks and the virologic, immunologic, and clinical status of the macaques was monitored for up to 56 weeks. PMPA prevented SIV infection in all macaques without toxicity, whereas all control macaques became infected. These results suggest a potential role for PMPA prophylaxis against early HIV infection in cases of known exposure.
The Chemistry of Size and Order on a Nanometer Scale
Authors: Heath James R.
Published: October 2006

Materials with desirable properties may be created through control of crystal size and shape and assembly of such crystals into more complex arrangements. In his Perspective, Heath discusses recent work reported in this issue by Murray
et al
. (
p. 1335
) in which nanocrystals of cadmium selenide were formed into ordered assemblies of quantum dots. Such results represent a first step toward self-assembly of device structures.
Creation of Theta-Auroras: The Isolation of Plasma Sheet Fragments in the Polar Cap
Authors: Newell Patrick T. , Meng Ching-I.
Published: October 2006

The auroral oval is a ring of luminosity enclosing geomagnetic field lines connected to the solar wind. Occasionally the ring has a bar across it, which seems to imply a bifurcation of the open region. Here results confirm that this "θ-aurora" actually does represent this odd bifurcated configuration, and they demonstrate how it happens. It has hitherto been assumed that θ-auroras occur when the interplanetary magnetic field is directed northward, because that is true of most very-high-latitude arcs. In fact, θ-auroras occur exclusively during the dynamic reconfiguration that follows when the interplanetary magnetic field turns southward after a prolonged northward interval.
Report Strips R&D Down to the Basics
Authors: Mervis Jeffrey
Published: October 2006

A new definition of research that excludes a big chunk of military spending would give policy-makers a much better grasp of what's essential to the health of the U.S. research enterprise, says a new report from the National Academy of Sciences. And that's crucial at a time of declining budgets. The full report is available on-line at see
http://www.nas.edu/nap/online/fedfunds/.
An Exploding Star in Motion
Authors: Chevalier Roger A.
Published: October 2006

A recently discovered supernova, designated SN 1993J, has been imaged with exceptional resolution with a sensitive array of radiotelescopes. As Chevalier discusses in his Perspective, the imaging results reported by Marcaide
et al.
in this issue (
p. 1475
) directly show the expansion of a highly symmetrical spherical shock wave. Variations in radio emission around the expanding shell may enable astronomers to learn more about these very energetic explosions.
Expansion of SN 1993J
Authors: Marcaide J. M. , Alberdi A. , Ros E. , Diamond P. , Shapiro I. I. , Guirado J. C. , Jones D. L. , Krichbaum T. P. , Mantovani F. , Preston R. A. , Rius A. , Schilizzi R. T. , Trigilio C. , Whitney A. R. , Witzel A.
Published: October 2006

A sequence of images from very long baseline interferometry shows that the young radio supernova SN 1993J is expanding with circular symmetry. However, the circularly symmetric images show emission asymmetries. A scenario in which freely expanding supernova ejecta shock mostly isotropic circumstellar material is strongly favored. The sequence of images constitutes the first “movie” of a radio supernova.
Protein Sculptors That Help Turn on Genes
Authors: Wickelgren Ingrid
Published: October 2006

Over the past decade or so, molecular biologists have learned that cells use various combinations of the proteins called transcription factors to turn genes on and off. But recent research has shown that the precise three-dimensional shapes of those transcription factor complexes are just as critical for correct gene control as the identities of the proteins that make them up. What's more, these shapes are often sculpted with the aid of “architectural proteins,” which are themselves part of the complexes and which help assemble them by forcing large bends into the DNA to which the complexes bind.
Correlated Variations in the Solar Neutrino Flux and the Solar Wind and the Relation to the Solar Neutrino Problem
Authors: McNutt R. L.
Published: October 2006

Solar wind parameters from the Massachusetts Institute of Technology (MIT) plasma experiment on the IMP 8 spacecraft overlap ∼19 years of published neutrino flux observations from the Homestake experiment. A strong correlation is found between neutrino flux and solar wind properties, in particular, the solar wind mass flux. The correlation is significantly better than any anticorrelation with sunspot number and is comparable to those previously found with photospheric magnetic flux and shifts in
p
-mode frequencies. If current notions of solar structure are correct, these observations require new fundamental physics of neutrinos. For a proper choice of neutrino parameters, the level of variations is consistent with resonant conversion of electron neutrinos to a nondetected flavor eigenstate mediated by the magnetic field in the sun's convective zone. The solar wind mass flux may act as a proxy for this field, producing the solar wind-neutrino flux connection.
Laser-Driven Movement of Three-Dimensional Microstructures Generated by Laser Rapid Prototyping
Authors: Lehmann Olaf , Stuke Michael
Published: October 2006

Three-dimensional microstructures consisting of aluminum oxide and aluminum were fabricated by laser-induced direct-write deposition from the gas phase. Trimethylamine alane and oxygen were used as precursors. Thermal expansion forces resulting from suitable laser irradiation were used to drive the movement of microstructure parts. Applications include micromechanical actuators, such as microtweezers and micromotors. The one-step nature of the laser direct-write process allows rapid prototyping of such devices.
A
Drosophila
Homolog of the Yeast Origin Recognition Complex
Authors: Gossen Manfred , Pak Daniel T. S. , Hansen Stig K. , Acharya Jairaj K. , Botchan Michael R.
Published: October 2006

Genes from
Drosophila melanogaster
have been identified that encode proteins homologous to Orc2p and Orc5p of the
Saccharomyces cerevisiae
origin recognition complex (ORC). The abundance of the
Drosophila
Orc2p homolog DmORC2 is developmentally regulated and is greatest during the earliest stages of embryogenesis, concomitant with the highest rate of DNA replication. Fractionation of embryo nuclear extracts revealed that DmORC2 is found in a tightly associated complex with five additional polypeptides, much like the yeast ORC. These studies will enable direct testing of the initiator-based model of replication in a metazoan.
Post-Cold War Science Thrives in the Heart of Siberia
Authors: Stone Richard
Published: October 2006

Novosibirsk, Russia—A collection of scientific institutes established in the southern Siberian city of Novosibirsk in the late 1950s is faring relatively well—at least in comparison with research centers elsewhere in Russia. The successful formula: foreign funding, a unique scientific culture, and fewer social problems of the type that are afflicting cities like Moscow.
Weapons Researchers Come In From the Cold
Authors: Stone Richard
Published: October 2006

Novosibirsk, Russia—A once-secret biological weapons facility is struggling to stay afloat in the post-Cold War world. Its main lifeline is the manufacture of pharmaceutical products.
Efficient Aldolase Catalytic Antibodies That Use the Enamine Mechanism of Natural Enzymes
Authors: Wagner Jürgen , Lerner Richard A. , Barbas Carlos F.
Published: October 2006

Antibodies that catalyze the aldol reaction, a basic carbon-carbon bond-forming reaction, have been generated. The mechanism for antibody catalysis of this reaction mimics that used by natural class I aldolase enzymes. Immunization with a reactive compound covalently trapped a Lys residue in the binding pocket of the antibody by formation of a stable vinylogous amide. The reaction mechanism for the formation of the covalent antibody-hapten complex was recruited to catalyze the aldol reaction. The antibodies use the ε-amino group of Lys to form an enamine with ketone substrates and use this enamine as a nascent carbon nucleophile to attack the second substrate, an aldehyde, to form a new carbon-carbon bond. The antibodies control the diastereofacial selectivity of the reaction in both Cram-Felkin and anti-Cram-Felkin directions.
Diffusion Across the Nuclear Envelope Inhibited by Depletion of the Nuclear Ca
2+
Store
Authors: Stehno-Bittel Lisa , Perez-Terzic Carmen , Clapham David E.
Published: October 2006

Intact, isolated nuclei and a nuclear membrane (ghost) preparation were used to study regulation of the movement of small molecules across the
Xenopus laevis
oocyte nuclear membrane. In contrast to models of the nuclear pore complex, which assume passive bidirectional diffusion of molecules less than 70 kilodaltons, diffusion of intermediate-sized molecules was regulated by the nuclear envelope calcium stores. After depletion of nuclear store calcium by inositol 1,4,5-trisphosphate or calcium chelators, fluorescent molecules conjugated to 10-kilodalton dextran were unable to enter the nucleus. Dye exclusion after calcium store depletion was not dependent on the nuclear matrix because it occurred in nuclear ghosts lacking nucleoplasm. Smaller molecules and ions (500-dalton Lucifer yellow and manganese) diffused freely into the core of the nuclear ghosts and intact nuclei even after calcium store depletion. Thus, depletion of the nuclear calcium store blocks diffusion of intermediate-sized molecules.
Making a New Ruler for the Nanoworld
Authors: Kaiser Jocelyn
Published: October 2006

Gaithersburg, Maryland—Computer chips and other devices are rapidly shrinking to the nanometer (a billionth of a meter) scale, and features on them must fall within exacting tolerances. The microscopes used to determine these tolerances will have to make precise measurements on both the atomic scale and relatively vaster distances. Current scopes cannot. But this week saw the debut of the “molecular measuring machine,” which combines a scanning tunneling microscope with a laser interferometer to measure the distance between points 1 millimeter apart to within 20 to 40 nanometers.
Direct Perception of Three-Dimensional Motion from Patterns of Visual Motion
Authors: Fermüller Cornelia , Aloimonos Yiannis
Published: October 2006

Measurements of retinal motion along a set of predetermined orientations on the retina of a moving system give rise to global patterns. Because the form and location of these patterns depend purely on three-dimensional (3D) motion, the effects of 3D motion and scene structure on image motion can be globally separated. The patterns are founded on easily derivable image measurements that depend only on the sign of image motion and do not require information about optical flow. The computational theory presented here explains how the self-motion of a system can be estimated by locating these patterns.
Clinical Trials: AIDS Trials Take On Peer Review
Authors: Cohen Jon
Published: October 2006

Members of the world's pre-eminent AIDS drug testing network, the AIDS Clinical Trials Network, say the group reviewing their grants doesn't know what it's doing. They have protested to the funding agency, the National Institute of Allergy and Infectious Diseases, and those protests have opened a window onto the normally secretive grant review process. The review group, in response, says that some leading institutions simply wrote poor grants.
Regulation of PHO4 Nuclear Localization by the PHO80-PHO85 Cyclin-CDK Complex
Authors: O'Neill Elizabeth M. , Kaffman Arie , Jolly Emmitt R. , O'Shea Erin K.
Published: October 2006

PHO4, a transcription factor required for induction of the
PHO5
gene in response to phosphate starvation, is phosphorylated by the PHO80-PHO85 cyclin-CDK (cyclin-dependent kinase) complex when yeast are grown in phosphate-rich medium. PHO4 was shown to be concentrated in the nucleus when yeast were starved for phosphate and was predominantly cytoplasmic when yeast were grown in phosphate-rich medium. The sites of phosphorylation on PHO4 were identified, and phosphorylation was shown to be required for full repression of
PHO5
transcription when yeast were grown in high phosphate. Thus, phosphorylation of PHO4 by PHO80-PHO85 turns off
PHO5
transcription by regulating the nuclear localization of PHO4.
U.S. Power Outage Won't Dim ITER
Authors: Lawler Andrew
Published: October 2006

The $8 billion International Thermonuclear Experimental Reactor program is moving ahead—with or without support from the United States—as participating countries prepare to decide where to build the facility and how much each country should pay.
Advisory Panel Seeks Cost-Saving Solutions
Authors: Lawler Andrew
Published: October 2006

The U.S. fusion program is trying to find a way to honor its international commitments and retain its domestic program—but with less money to spend.
Does Rochester Without Math Add Up?
Authors: Holden Constance
Published: October 2006

The math community has been up in arms over a plan by the University of Rochester to do away with its graduate program in mathematics as an economy move. With only lower level math courses to teach, the number of tenured faculty will drop from 21 to 10. The American Mathematical Society has adopted a resolution protesting the plan (available on-line at
www.ams.org/committee/profession/roch-ap1.html
), and other mathematicians argue that Rochester's strengths in quantitative fields such as science and economics make the move particularly unwise.
Life at the Top: Animals Pay the High Price of Dominance
Authors: Morell Virginia
Published: October 2006

In the wild, dominant animals stress out their subordinates, according to textbook studies. But recent studies show the top dogs—as well as top dwarf mongooses, baboons, and other animals—have the highest levels of cortisol, a stress hormone. And habitually high cortisol levels may cost them years off their lives.
Checkpoints Take the Next Step
Authors: Carr Antony M.
Published: October 2006

Checkpoints are times during the cell cycle when the cell can choose to pause if something is amiss—if its DNA is damaged or if there is a mistake in the synthesis of the new DNA—so that the damage can be repaired. The proteins of these pathways have been defined genetically. Now Carr discusses new biochemical evidence from yeast, presented in two papers in this week's issue of
Science
(p
p. 353
and
p. 357
), that start to elucidate the functions of two of these proteins—Chk1 and Rad3.
Tax Law Casts Pall Over Research Aid
Authors: Pokrovsky Vladimir
Published: October 2006

Moscow—A new tax law revokes the tax exemptions that had been enjoyed by the foreign foundations that support much of the research in Russia. As a result, many of the foundations, including the International Science Foundation, funded by the American financier George Soros, may find that operating in Russia is no longer worthwhile.
Digging Deeply Into Galaxies' Pasts
Authors: Goldsmith Donald
Published: October 2006

San Antonio—By staring for 10 days straight at the same point in the sky, the Hubble Space Telescope has unveiled the faintest galaxies ever seen. They appear to lie at such great distances that astronomers believe they were shining when the universe was a sixth of its present age. Their abundance—the image reveals nearly 2000 of them—implies that large-scale galaxy formation must have taken place at a very early stage of cosmic history.
A Docking Receptor for HDL Cholesterol Esters
Authors: Steinberg Daniel
Published: October 2006

Cholesterol is carried through the blood by low-density lipoprotein (LDL) (“bad” cholesterol) and then into cells by the LDL receptor. In this issue of
Science
(
p. 518
), the first receptor for high-density lipoprotein (HDL) (“good” cholesterol) is reported to be the cell-surface protein SR-B1. In his Perspective, D. Steinberg discusses this discovery and describes how the selective uptake of cholesterol mediated by SR-BI delivers cholesterol for steroid hormone synthesis to the liver, the adrenal gland, and the ovary.
The Structure and Stability of Atomic Liquids: From Clusters to Bulk
Authors: Doye Jonathan P. K. , Wales David J.
Published: October 2006

Insights into the structure of simple liquids are presented from analysis of the effect of the range of interatomic forces on the multidimensional potential energy surfaces of bulk material and clusters. An understanding at the microscopic level is provided of how the liquid phase is destabilized in systems with very short-range interparticle forces. For small clusters bound by long-range interatomic forces, the lowest energy minimum has an amorphous structure typical of the liquidlike state. This suggests an explanation for the transition from electronic to geometric magic numbers (structures of special stability) observed in the mass spectra of sodium clusters.
Design of a Random Quantum Spin Chain Paramagnet: Sr
3
CuPt
0.5
Ir
0.5
O
6
Authors: Nguyen Tu N. , Lee Patrick A. , zur Loye Hans-Conrad
Published: October 2006

A new class of magnetic behavior, random quantum spin chain paramagnetism, has been observed in the one-dimensional compound Sr
3
CuPt

1-
x

Ir

x

O
6
. A random quantum spin chain system has
S
= ½ spins coupled by Heisenberg exchange interactions that are randomly ferromagnetic or antiferromagnetic between neighbors along the chain. This condition was fulfilled by members of the solid solution Sr
3
CuPt

1-
x

Ir
x
O
6
(
x
= 0, 0.25, 0.50, 0.75, and 1), whose end-members, Sr
3
CuPtO
6
and Sr
3
CuIrO
6
, are antiferromagnetic and ferromagnetic, respectively. Magnetic susceptibility data for the solid solution Sr
3
CuPt

1-
x

Ir
x
O
6
(
x
= 0, 0.25, 0.50, 0.75, and 1) were collected and were found to be in excellent agreement with a theoretical model.
Microprocessors Deliver Teraflops
Authors: Glanz James
Published: October 2006

San Diego—The world's fastest computer is being put together with truckloads of the same microprocessors that power high-end PCs. By linking more than 9000 Pentium Pro processors, Intel is building a parallel computer that will top out at 1.8 trillion operations per second, 10 times the speed of any existing machine. To be installed by the end of the year at Sandia National Laboratory, the behemoth will serve the nuclear weapons program by simulating how weapons age and malfunction, but it will also act as a test bed for new techniques in parallel computation. Computers/Math
“Negative Viscosity” in a Magnetic Fluid
Authors: Rosensweig Ronald E.
Published: October 2006

Fluids containing colloidal dispersions of magnetic particles exhibit new phenomena, including a reduction in viscosity under some conditions. In his Perspective, Rosensweig reviews the theoretical and experimental state of magnetic fluid studies.
Pa
3̅ Modified Fluorite-Type Structures in Metal Dioxides at High Pressure
Authors: Haines J. , Léger J. M. , Schulte O.
Published: October 2006

Rutile-structured SnO
2
, PbO
2
, and RuO
2
have long been known to transform to cubic high-pressure phases, for which a fluorite structure has been assumed. Rietveld refinement results from x-ray diffraction studies indicated that these phases have a modified fluorite structure (space group
Pa
3̅). Thus, for metal dioxides, all known cubic, postrutile phases have the
Pa
3̅ structure, thereby providing experimental examples of the high-pressure structure predicted from theoretical calculations for stishovite (rutile-structured silica). High-pressure transitions in stishovite may have profound implications for the geochemistry of the core-mantle boundary.
ARC Affair Troubles French Scientists
Authors: Balter Michael
Published: October 2006

Paris—Allegations of financial mismanagement in the Association for Cancer Research (ARC), one of France's biggest medical charities, are raising concerns that an important source of research funding may dry up. Biomedical researchers are also asking whether scientists themselves should have kept a closer eye on ARC.
Probing Catalysts with Water
Authors: Sauer Joachim
Published: October 2006

Solid catalysts are widely used for chemical processes in industry, but much is still unknown about how they work on a microscopic level. In his Perspective, Sauer comments on work reported by

Smith
et al.

in the same issue, in which water molecules were used as probes of the catalytic active sites.
An Ice Shelf Breakup
Authors: Fahnestock Mark
Published: October 2006

Large ice masses such as ice sheets and ice shelves change as the Earth's climate changes, and can serve as indicators of past climate variation. In his Perspective, Fahnestock discusses observations reported by

Rott
et al.

in the same issue, which show the dramatic collapse and breakup of the Larsen Ice Shelf, off the western coast of Antarctica.
Stimulation of Membrane Ruffling and MAP Kinase Activation by Distinct Effectors of RAS
Authors: Joneson Tom , White Michael A. , Wigler Michael H. , Bar-Sagi Dafna
Published: October 2006

The RAS guanine nucleotide binding proteins activate multiple signaling events that regulate cell growth and differentiation. In quiescent fibroblasts, ectopic expression of activated H-RAS (H-RAS
V12
, where V12 indicates valine-12) induces membrane ruffling, mitogen-activated protein (MAP) kinase activation, and stimulation of DNA synthesis. A mutant of activated H-RAS, H-RAS
V12C40
(where C40 indicates cysteine-40), was identified that was defective for MAP kinase activation and stimulation of DNA synthesis, but retained the ability to induce membrane ruffling. Another mutant of activated H-RAS, H-RAS
V12S35
(where S35 indicates serine-35), which activates MAP kinase, was defective for stimulation of membrane ruffling and induction of DNA synthesis. Expression of both mutants resulted in a stimulation of DNA synthesis that was comparable to that induced by H-RAS
V12
. These results indicate that membrane ruffling and activation of MAP kinase represent distinct RAS effector pathways and that input from both pathways is required for the mitogenic activity of RAS.
Heavy Hitters Anchor the AAAS Lineup at Annual Meeting
Authors: Lawler Andrew , Mervis Jeffrey , Marshall Eliot
Published: October 2006

Baltimore—This week, within a few short blocks of Baltimore's baseball stadium, U.S. Vice President Al Gore came out swinging in his speech at the Annual Meeting and Science Innovation Exposition of the American Association for the Advancement of Science. Some meeting highlights: Gore had choice words about political opponents and their support of science; Congressman Robert Walker, chair of the House Science Committee, had choice words for scientists about their unwillingness to state scientific priorities; and primate researchers spoke on the origin of moral choice. Later meeting sessions will be covered next week. (Full text of Gore's speech is available at
http://www.aaas.org/spp/dspp/rd/rdwwwpg.htm
)
Structure, Dynamics, and Thermodynamics of Clusters: Tales from Topographic Potential Surfaces
Authors: Wales David J.
Published: October 2006

Theoretical studies of atomic and molecular clusters often seek to explain structure, dynamics, and thermodynamics in terms of the underlying potential energy surface and the form of the interparticle interaction. One specific example from each of these categories is considered here; the overall approach can be summarized as global analysis of potential surfaces. Changes in the most favorable cluster morphology can be qualitatively understood as a function of the range of the interparticle forces. Thermodynamic properties can be calculated from a representative sample of local minima on the potential energy surface. However, prediction of dynamics requires not only knowledge of minima but also transition states and reaction pathways.
Water Clusters
Authors: Liu K. , Cruzan J. D. , Saykally R. J.
Published: October 2006

A surge of progress in both laser spectroscopy experiments and theoretical dynamics methods has facilitated new, highly detailed studies of water clusters. The geometrical structures and hydrogen-bond tunneling pathways of the water trimer, tetramer, pentamer, and hexamer systems have recently been characterized with global analysis of potential surfaces, diffusion Monte Carlo calculations, and far-infrared laser vibration-rotation tunneling spectroscopy. Results from these and other studies are yielding important insights into the cooperativity effects in hydrogen bonding, aqueous solvation, and hydrogen-bond network rearrangement dynamics, which promise to enhance our understanding of solid and liquid water behavior.
Bio-Molecular Dynamics Comes of Age
Authors: Berendsen Herman J. C.
Published: October 2006

Atomic force microscopy has recently been used to measure the binding force between two biomolecules; complementing the experiments are computational molecular dynamics studies that seek to reveal the details of the binding and unbinding mechanisms. In his Perspective, Berendsen discusses the results reported in the same issue by Grubmüller
et al.
(
p. 997
) on numerical simulations of the binding and separation of biotin from streptavidin, which show excellent agreement with measurements of the rupture force.

[Data]
(0.9 Mbytes) A global view of the rupture process. (European Readers can visit the

Grubmüller
et al.
Home Page

)

[Data]
(1.5 Mbytes) A detailed view of the binding pocket. (European Readers can visit the

Grubmüller
et al.
Home Page

)
Regulating G Protein Signaling
Authors: Roush Wade
Published: October 2006

Cell biologists have long known that cells can damp down their responses to hormones, neurotransmitters, and other regulators, but exactly how this “desensitization” occurs has been unclear. Now a flurry of work from several labs is revealing how one major group of intracellular communication lines—those using G proteins to transmit signals to the cell interior—achieves this volume control. Researchers have identified a new family of proteins, known as the RGS proteins (for regulators of G protein signaling), that attenuate signaling through those pathways, apparently by binding to one of the three protein subunits that make up a complete G protein. The new findings could lead to a much better understanding of how G protein-signal pathways work—information that could have practical implications as up to 60% of all drugs exert their effects through these pathways.
Molecular Trees: A New Branch of Chemistry
Authors: Bell Thomas W.
Published: October 2006

Two hot areas in chemistry are dendrimers—highly branched polymers that are synthesized in stages from a core, in a manner resembling a snowflake—and self-assembly, the synthesis of molecules through molecular recognition. These ideas have been combined by Zimmerman
et al.
(p. 1095) in a report in this week's issue of
Science
. Bell discusses how these authors have produced dendrimers from smaller subunits in one step to create nanometer-scale particles.
Drilling and Dating New Jersey Oligocene-Miocene Sequences: Ice Volume, Global Sea Level, and Exxon Records
Authors: Miller Kenneth G. , Mountain Gregory S.
Published: October 2006

Oligocene to middle Miocene sequence boundaries on the New Jersey coastal plain (Ocean Drilling Project Leg 150X) and continental slope (Ocean Drilling Project Leg 150) were dated by integrating strontium isotopic stratigraphy, magnetostratigraphy, and biostratigraphy (planktonic foraminifera, nannofossils, dinocysts, and diatoms). The ages of coastal plain unconformities and slope seismic reflectors (unconformities or stratal breaks with no discernible hiatuses) match the ages of global δ
18
O increases (inferred glacioeustatic lowerings) measured in deep-sea sites. These correlations confirm a causal link between coastal plain and slope sequence boundaries: both formed during global sea-level lowerings. The ages of New Jersey sequence boundaries and global δ
18
O increases also correlate well with the Exxon Production Research sea-level records of Haq
et al
. and Vail
et al
., validating and refining their compilations.
The Exchange of Impact Ejecta Between Terrestrial Planets
Authors: Gladman Brett J. , Burns Joseph A. , Duncan Martin , Lee Pascal , Levison Harold F.
Published: October 2006

Orbital histories of ejecta from the terrestrial planets were numerically integrated to study their transfer to Earth. The properties of the lunar and martian meteorites are consistent with a recurrent ejection of small meteoroids as a result of impacts on their parent bodies. Long-range gravitational effects, especially secular resonances, strongly influence the orbits of many meteoroids, increasing their collision rates with other planets and the sun. These effects and collisional destruction in the asteroid belt result in shortened time scales and higher fluxes than previously believed, especially for martian meteorites. A small flux of mercurian ejecta appears possible; recovery of meteorites from the Earth and Venus is less likely.
Does the Sun Trigger Outbursts From Earth's Magnetosphere?
Authors: Kerr Richard A.
Published: October 2006

Whenever the sun pumps unusual amounts of energy into Earth's magnetic field, the field is liable to discharge the energy in a short, disruptive burst called a substorm. Substorms, which cause the aurora to flare, send damaging currents through power grids, and disrupt satellites, are now impossible to predict, but a new proposal offers hope. A solar physicist has found that substorms often take place when the interplanetary magnetic field changes direction, suggesting that spacecraft data might be used to predict them.
Nucleocytoplasmic Transport
Authors: Görlich Dirk , Mattaj Iain W.
Published: October 2006

Active transport of proteins and RNAs between the nucleus and cytoplasm is a major process in eukaryotic cells. Recently, factors that recognize transport substrates and mediate nuclear import or export have been characterized, revealing interactions that target substrates to the nuclear pore complexes, through which translocation occurs. Translocation requires energy, and for the import process this energy is at least partly consumed by the action of the small guanosine triphosphatase Ran. In the first half of the review, some of the well-established general background information on nucleocytoplasmic transport is discussed. The second half describes recent information on the mechanistic details of nuclear import and export as well as major unresolved issues such as how directionality is conferred on either import or export. The whole review is slanted toward discussion of metazoan cells.
Battle Lines Drawn for 1997 R&D Budget
Authors: Lawler Andrew , Mervis Jeffrey
Published: October 2006

President Clinton has asked for selected growth in science as part of his budget request for the 1997 fiscal year that begins on 1 October, including 4% increases for the National Institutes of Health and the National Science Foundation. But many of his proposals are expected to face serious opposition in Congress, which has yet to pass a 1996 budget for several agencies.
Hemoglobin Reveals New Role as Blood Pressure Regulator
Authors: Glanz James
Published: October 2006

Hemoglobin, the familiar oxygen-carrying molecule in red blood cells, may have been leading a double life. A group at the Duke University Medical Center reported in the 21 March issue of
Nature
that, alongside the familiar respiratory cycle, hemoglobin carries out a second cycle in which it sops up a form of nitric oxide in the lungs and releases it in blood vessels—a shuttle service that helps stabilize blood pressure. Besides giving hemoglobin a surprising new role, the finding could be a boon for efforts to turn cell-free hemoglobin solutions, which now tend to produce dangerous rises in blood pressure, into workable blood substitutes.
Light-Induced Degradation of TIMELESS and Entrainment of the
Drosophila
Circadian Clock
Authors: Myers Michael P. , Wager-Smith Karen , Rothenfluh-Hilfiker Adrian , Young Michael W.
Published: October 2006

Two genes,
period
(
per
) and
timeless
(
tim
), are required for production of circadian rhythms in
Drosophila
. The proteins encoded by these genes (PER and TIM) physically interact, and the timing of their association and nuclear localization is believed to promote cycles of
per
and
tim
transcription through an autoregulatory feedback loop. Here it is shown that TIM protein may also couple this molecular pacemaker to the environment, because TIM is rapidly degraded after exposure to light. TIM accumulated rhythmically in nuclei of eyes and in pacemaker cells of the brain. The phase of these rhythms was differentially advanced or delayed by light pulses delivered at different times of day, corresponding with phase shifts induced in the behavioral rhythms.
Chair Quits Japan Panel in Protest
Authors: Normile Dennis
Published: October 2006

Tokyo—Kiyoo Mogi, the head of a committee of Japanese seismologists responsible for telling the government when unusual seismic phenomena mean a large-scale earthquake is about to strike a region near Tokyo, has resigned after failing to win the right to say “maybe.” Mogi has tried unsuccessfully to convince the Meteorological Agency that its current yes/no policy is too restrictive and that a third option—to issue a warning with a probability attached—would better serve public safety.
Superconductivity Turns 10
Authors: Service Robert F.
Published: October 2006

Houston—A decade after their discovery, compounds that superconduct electricity at high temperatures are making it into the real world—although no one can prove how they work. And 2 weeks ago in Houston, at the 10th Anniversary High-Temperature Superconductivity (HTS) Workshop on Physics, Materials, and Applications, both practical accomplishments and theoretical frustrations took center stage. Thin HTS films are now being tested for use in filtering signals from noise in cellular phone base stations, a huge market, and the first HTS underground power transmission cable was just made with a standard industrial process. Yet while a cluster of recent experiments has supported the idea that HTS is borne on magnetically paired electrons, concurrent theoretical developments have thrown some very cold water on that idea.
New Neurons Use "Lookouts" to Navigate Nervous System
Authors: Roush Wade
Published: October 2006

Like a ship journeying toward a strange harbor, a growing motor neuron heading into the peripheral nervous system faces a major navigational challenge. In a series of recent studies of fruit fly embryos, researchers have identified a handful of lookouts on deck—proteins that straddle the cell membrane—that help guide the neuron, signaling it to swerve away from the main nerve channel and toward a target muscle. Once there, according to a report in this issue (
p. 1867
), a newly discovered protein called Late Bloomer helps to signal “all stop.” And studies of the rat have identified several proteins that then serve as dockworkers, tugging molecular gangplanks and cranes into place to off-load the neurochemical cargo and form a synapse. Eventually, researchers say, the lookouts may help neuroscientists chart a far more intricate journey: one leading to an understanding of how connections form in the brain itself.
Late Cretaceous Oceans and the Cool Tropic Paradox
Authors: D'Hondt Steven , Arthur Michael A.
Published: October 2006

Oxygen isotopic proxies of paleo-sea surface temperatures (SSTs) suggest that Maastrichtian (about 66 million years ago) tropical SSTs were lower than those of today. They also demonstrate that Maastrichtian latitudinal SST gradients were much lower than those of the present. The low Maastrichtian SST gradients indicate that meridional heat transport was much greater or latitudinal differences in the balance of radiation to and from the sea surface were much less extreme during the latest Cretaceous than they are today, or that both conditions were true. These findings challenge traditional interpretations of “greenhouse” Late Cretaceous climates.
Enhancement of Solution NMR and MRI with Laser-Polarized Xenon
Authors: Navon G. , Song Y.-Q. , Rõõm T. , Appelt S. , Taylor R. E. , Pines A.
Published: October 2006

Optical pumping with laser light can be used to polarize the nuclear spins of gaseous xenon-129. When hyperpolarized xenon-129 is dissolved in liquids, a time-dependent departure of the proton spin polarization from its thermal equilibrium is observed. The variation of the magnetization is an unexpected manifestation of the nuclear Overhauser effect, a consequence of cross-relaxation between the spins of solution protons and dissolved xenon-129. Time-resolved magnetic resonance images of both nuclei in solution show that the proton magnetization is selectively perturbed in regions containing spin-polarized xenon-129. This effect could find use in nuclear magnetic resonance spectroscopy of surfaces and proteins and in magnetic resonance imaging.
Asymmetries Generated by Transcription-Coupled Repair in Enterobacterial Genes
Authors: Francino M. Pilar , Chao Lin , Riley Margaret A. , Ochman Howard
Published: October 2006

Although certain replication errors occur at different frequencies on each of the complementary strands of DNA, it remains unclear whether this bias is prevalent enough during chromosome replication to affect sequence evolution. Here, nucleotide substitutions in enteric bacteria were examined, and no difference in mutation rates was detected between the leading and lagging strands, but in comparing the coding and noncoding strands, an excess of C→T changes was observed on the coding strand. This asymmetry is best explained by transcription-coupled repair on the noncoding strand. Although the vast majority of mutations are thought to arise from spontaneous errors during replication, this result implicates DNA damage as a substantial source of mutations in the wild.
Impact Craters All in a Row?
Authors: Kerr Richard A.
Published: October 2006

Space Shuttle radar has yielded hints that Earth may have been pelted by the bits of a shattered asteroid or comet, an event that made headlines when it happened to Jupiter two summers ago. Many geologists are skeptical of the claim, however. The radar images seem to show a string of three 12-kilometer impact craters in the Sahara of northern Chad, but an impact origin has been confirmed only for the first crater, which was formed roughly 365 million years ago; the others could be volcanic features.
Physicists Trap Photons and Count Them One by One
Authors: Watson Andrew
Published: October 2006

Physicists know that light is made of packets called photons, but they have longed to actually see light's discrete nature. Now they can, in an ingenious experiment at the Ecole Normale Supérieure in Paris that captures a few photons in a tiny chamber and counts them like marbles. Along with painstaking engineering, the experiment required a supersensitive scheme for detecting photons: individual atoms, crossing the chamber one by one in an excited state that is sensitive to the presence of the photons.
Generation of GTP-Ran for Nuclear Protein Import
Authors: Moore Mary Shannon
Published: October 2006

Certain cytoplasmic proteins are actively transported into the nucleus through nuclear pores. In a paper in this week's issue the function of a participating soluble protein, p10, is elucidated (Nehrbass and Blobel,
p. 120
). Moore explains, in her Perspective, how these findings solve the riddle of the source of one of the molecules required for transport, GTP-Ran.
Striction-Coupled Magnetoresistance in Perovskite-Type Manganese Oxides
Authors: Kuwahara H. , Tomioka Y. , Moritomo Y. , Asamitsu A. , Kasai M. , Kumai R. , Tokura Y.
Published: October 2006

Magnetoresistance resulting in a drop in resistivity of more than three orders of magnitude that is strongly coupled to lattice striction has been observed under a relatively low magnetic field (0.4 tesla at 115 kelvin) for a single crystal of perovskite-type manganese oxide with finely controlled ionic radii of the A sites, (Nd,Sm)
1/2
Sr
1/2
MnO
3
. The colossal magnetoresistance phenomena are viewed as a first-order insulator-to-metal phase transition induced by a magnetic field, which accompanies a metamagnetic (antiferromagnetic-to-ferromagnetic) transition and a structural change in the lattice. Clear hystereses and abrupt changes in magnetization, striction, and resistivity were observed in increasing and decreasing magnetic fields at temperatures (113 to 150 kelvin) just above the Curie temperature.
NIH Launches the Final Push to Sequence the Genome
Authors: Marshall Eliot , Pennisi Elizabeth
Published: October 2006

This week, the National Center for Human Genome Research at the National Institutes of Health is expected to announce six grants, totaling up to $60 million over 3 years, to begin large-scale sequencing of the human genome. Part of the money will also go to the development of new sequencing technologies. The grants will come with a strong message that all sequence data should be published quickly and that no patents be filed on raw sequences.
Cell Shape Determination: A Pivotal Role for Rho
Authors: Bussey Howard
Published: October 2006

During the formation of a daughter yeast cell, a small Ras-like GTPase acts as a morphogenetic coordinator and, as reported in two papers in this week's issue of
Science
[Drgonová (
p. 277
) and Qadota
et al.
(
p. 279
)], regulates beta(1arrow pointing right3)glucan synthase, the enzyme that makes the glycans of the cell walls. In his Perspective, Bussey discusses this function of Rho and the parallels to its functions in mammalian cells.
Extraterrestrial Helium Trapped in Fullerenes in the Sudbury Impact Structure
Authors: Becker Luann , Poreda Robert J. , Bada Jeffrey L.
Published: October 2006

Fullerenes (C
60
and C
70
) in the Sudbury impact structure contain trapped helium with a
3
He/
4
He ratio of 5.5 × 10
−4
to 5.9 × 10
−4
. The
3
He/
4
He ratio exceeds the accepted solar wind value by 20 to 30 percent and is higher by an order of magnitude than the maximum reported mantle value. Terrestrial nuclear reactions or cosmic-ray bombardment are not sufficient to generate such a high ratio. The
3
He/
4
He ratios in the Sudbury fullerenes are similar to those found in meteorites and in some interplanetary dust particles. The implication is that the helium within the C
60
molecules at Sudbury is of extraterrestrial origin.
Report Urges NSF to Promote Teaching
Authors: Mervis Jeffrey
Published: October 2006

An advisory panel that will deliver its recommendations next month to the National Science Foundation (NSF) hopes to start a revolution in undergraduate education by restoring the balance between research and teaching on college campuses. The report recommends that universities revise their approach to teaching to address the needs of all students, not just science majors, and that departments set goals for what their students should learn and hold faculty members accountable for students' performance. The price tag? A doubling of NSF's current $180 million budget for undergraduate education.
Trapped Coronal Magnetogravity Modes
Authors: Lou Yu-Qing
Published: October 2006

Theoretical analyses suggest a physical scenario for the trapping of coronal magnetogravity wave modes above the solar transition region. The shortest oscillation period of coronal magnetogravity modes should be longer than about 1.5 hours. These long-period modes may be responsible for the unexpected low-frequency (1 to 140 microhertz) discrete modes recently discovered in interplanetary charged particle fluxes and magnetic field fluctuations. If the detected modes are caused by these magnetogravity modes rather than by gravity-mode oscillations in the solar interior, then the solar corona and the transition region may be probed from an entirely new perspective by helioseismological techniques. These coronal magnetogravity modes could reveal clues to the heating and dynamics of the solar corona.
New Faculty Grants Program Expands Role of STA Agency
Authors: Normile Dennis
Published: October 2006

Tokyo—A new program, dubbed Core Research for Evolutional Science and Technology, is intended to give Japanese scientists a free hand to pursue large, ambitious, and somewhat risky projects with a huge potential payoff. Some 54 scientists have received the 5-year grants, worth up to $10 million, in the first wave of what Japan hopes will grow to 250 projects with an annual budget of half a billion dollars. The program is modeled after the Exploratory Research for Advanced Technology program, created 15 years ago by Genya Chiba as a way to break the mold in support for Japanese researchers
Physicists Advance Into Biology
Authors: Glanz James
Published: October 2006

St. Louis—Does biology need a “physicist” approach? Some physicists think so, and they're bringing their mechanistic philosophy to bear on questions ranging from how sharks electrically sense their prey to how cells of the immune system stick together. Biologists counter that finding universal laws of life is easier said than done. But many agree that a focus on mechanism may yield new insights into biological processes—while turning up some interesting new physics to boot.