bluuebunny/crossref_metadata_2025 huggingface dataset:
Zoologists Flock to U.S. Capital for Annual Assembly
Authors: Fischman Joshua , Pennisi Elizabeth
Published: October 2006

The American Society of Zoologists underwent a metamorphosis at its recent meeting in Washington, D.C. Arriving on 26 December as a zoology group, they left 4 days later as the Society for Integrative and Comparative Biology. Metamorphosis was also under scientific consideration, as researchers examined the genetic changes allowing some frogs to leap the tadpole stage. Other topics included bat-evading beetles and a real hero shrew.
Genetic Clues to Alzheimer's Disease
Authors: Dewji Nazneen N. , Singer S. Jonathan
Published: October 2006

All cases of familial Alzheimer's disease are caused by mutations in either the gene for beta-amyloid precursor protein or the protein S182/STM. The normal functions of these transmembrane proteins are unknown, and it is unclear how they relate to one another. N. N. Dewji and S. J. Singer propose that these two proteins interact in a way analogous to the Sevenless and Bride of Sevenless proteins in the developing
Drosophila
eye and the lin-12 and sel-12 proteins in the developing vulva of
Caenorhabditis elegans
. He suggests that excess deposition of amyloid, a hallmark and likely cause of Alzheimer's disease, would be a result of the abnormal processing of the protein-protein complex.

This proposal is likely to provoke responses from the community. If you have a question or would like to comment on the ideas presented by Drs. Dewji and Singer in this Perspective or if you would like to read the comments posted by others, please go to our interactive Forum (click on the Forum button below). You can also read the full text of this Perspective by clicking on the Full Text button below.
Cation-π Interactions in Chemistry and Biology: A New View of Benzene, Phe, Tyr, and Trp
Authors: Dougherty Dennis A.
Published: October 2006

Cations bind to the π face of an aromatic structure through a surprisingly strong, noncovalent force termed the cation-π interaction. The magnitude and generality of the effect have been established by gas-phase measurements and by studies of model receptors in aqueous media. To first order, the interaction can be considered an electrostatic attraction between a positive charge and the quadrupole moment of the aromatic. A great deal of direct and circumstantial evidence indicates that cation-π interactions are important in a variety of proteins that bind cationic ligands or substrates. In this context, the amino acids phenylalanine (Phe), tyrosine (Tyr), and tryptophan (Trp) can be viewed as polar, yet hydrophobic, residues.
Quantum Engineering of Optical Nonlinearities
Authors: Rosencher E. , Fiore A. , Vinter B. , Berger V. , Bois Ph. , Nagle J.
Published: October 2006

Second-order optical nonlinearities in materials are of paramount importance for optical wavelength conversion techniques, which are the basis of new high-resolution spectroscopic tools. Semiconductor technology now makes it possible to design and fabricate artificially asymmetric quantum structures in which optical nonlinearities can be calculated and optimized from first principles. Extremely large second-order susceptibilities can be obtained in these asymmetric quantum wells. Moreover, properties such as double resonance enhancement or electric field control will open the way to new devices, such as fully solid-state optical parametric oscillators.
Immunology Taught by Viruses
Authors: Zinkernagel Rolf M.
Published: October 2006

The survival of viruses depends on the survival of susceptible hosts. The vertebrate immune system and viruses have therefore coevolved complementary facets. Evidence from various balanced virus-host relationships illustrates that immunological specificity and memory may best be defined biologically and that the mature immune system does not discriminate between “self” and “nonself.” Rather, B cells distinguish antigen patterns, whereas T cell responses depend on localization, transport, and kinetics of antigen within lymphatic organs.
Controlled Room-Temperature Positioning of Individual Molecules: Molecular Flexure and Motion
Authors: Jung T. A. , Schlittler R. R. , Gimzewski J. K. , Tang H. , Joachim C.
Published: October 2006

Two-dimensional positioning of intact individual molecules was achieved at room temperature by a controlled lateral “pushing” action of the tip of a scanning tunneling microscope. To facilitate this process, four bulky hydrocarbon groups were attached to a rigid molecule. These groups maintained sufficiently strong interactions with the surface to prevent thermally activated diffusional motion, but nevertheless allowed controllable translation. Simulations demonstrated the crucial role of flexure during the positioning process. These results outline the key role of molecular mechanics in the engineering of predefined properties on a molecular scale.
Effect of Polymorphism in the
Drosophila
Regulatory Gene
Ultrabithorax
on Homeotic Stability
Authors: Gibson Greg , Hogness David S.
Published: October 2006

Development is buffered against unpredictable environmental and genetic effects. Here, a molecular genetic analysis of one type of developmental homeostasis, the establishment of thoracic segmental identity under the control of the
Ultrabithorax
(
Ubx
) gene in
Drosophila melanogaster
, is presented. Flies were artificially selected for differential sensitivity to the induction of bithorax phenocopies by ether vapor. The experiments demonstrated that increased sensitivity to ether correlated with a loss of expression of UBX in the third thoracic imaginal discs and that a significant proportion of the genetic variation for transcriptional stability can be attributed to polymorphism in the
Ubx
gene.
Protection Against Osmotic Stress by cGMP-Mediated Myosin Phosphorylation
Authors: Kuwayama Hidekazu , Ecke Maria , Gerisch Günther , Van Haastert Peter J. M.
Published: October 2006

Conventional myosin functions universally as a generator of motive force in eukaryotic cells. Analysis of mutants of the microorganism
Dictyostelium discoideum
revealed that myosin also provides resistance against high external osmolarities. An osmo-induced increase of intracellular guanosine 3′,5′-monophosphate was shown to mediate phosphorylation of three threonine residues on the myosin tail, which caused a relocalization of myosin required to resist osmotic stress. This redistribution of myosin allowed cells to adopt a spherical shape and may provide physical strength to withstand extensive cell shrinkage in high osmolarities.
Activation of Ventrolateral Preoptic Neurons During Sleep
Authors: Sherin J. E. , Shiromani P. J. , McCarley R. W. , Saper C. B.
Published: October 2006

The rostral hypothalamus and adjacent basal forebrain participate in the generation of sleep, but the neuronal circuitry involved in this process remains poorly characterized. Immunocytochemistry was used to identify the FOS protein, an immediate-early gene product, in a group of ventrolateral preoptic neurons that is specifically activated during sleep. The retrograde tracer cholera toxin B, in combination with FOS immunocytochemistry, was used to show that sleep-activated ventrolateral preoptic neurons innervate the tuberomammillary nucleus, a posterior hypothalamic cell group thought to participate in the modulation of arousal. This monosynaptic pathway in the hypothalamus may play a key role in determining sleep-wake states.
Research Gets Big Boost One Year After Kobe Earthquake
Authors: Normile Dennis
Published: October 2006

Tokyo—Japan has increased spending on earthquake-related research in the wake of the devastation from Kobe, moving away from a focus on prediction and promising scientists greater access to the data that are collected.
Microscopic Tunneling Spectroscopy on High-Temperature Superconductors
Authors: Kitazawa Koichi
Published: October 2006

The rate at which electrons quantum mechanically tunnel from a metal probe tip into the surface of a superconductor reveals crucial information about fundamental mechanism of superconductivity. High transition temperature superconductors have been difficult to study with this technique, but as Kitazawa discusses in his Perspective, recent improvements in tunneling microscopy are overcoming the obstacles.
Cellular Microbiology Emerging
Authors: Cossart P. , Boquet P. , Normark S. , Rappuoli R.
Published: October 2006

Microbial pathogens have evolved to interfere with essential processes in eukaryotic cells. P. Cossart illustrates how a new field, cellular microbiology, is emerging in which the targets of these microbes are being identified and many aspects of normal cell biology are being revealed.
Toward an Understanding of the Correlates of Protective Immunity to HIV Infection
Authors: Haynes Barton F. , Pantaleo Giuseppe , Fauci Anthony S.
Published: October 2006

Considerable progress has been made recently in understanding the genetic, immunologic, and virologic factors in human immunodeficiency virus (HIV)-infected individuals who either rapidly progress or do not progress to acquired immunodeficiency syndrome (AIDS). In addition, detection of HIV-specific immune responses in HIV-negative individuals who have been exposed to the virus multiple times suggests that natural immune responses to HIV may be protective in rare individuals. Understanding the correlates of protective immunity to HIV infection is critical to efforts to develop preventive HIV vaccines as well as to determine the feasibility of treating HIV infection by boosting immunity to HIV.
Assembly of a Ribonucleoprotein Catalyst by Tertiary Structure Capture
Authors: Weeks Kevin M. , Cech Thomas R.
Published: October 2006

CBP2 is an RNA tertiary structure binding protein required for efficient splicing of a yeast mitochondrial group I intron. CBP2 must wait for folding of the two RNA domains that make up the catalytic core before it can bind. In a subsequent step, association of the 5′ domain of the RNA is stabilized by additional interactions with the protein. Thus, CBP2 functions primarily to capture otherwise transient RNA tertiary structures. This simple one-RNA, one-protein system has revealed how the kinetic pathway of RNA folding can direct the assembly of a specific ribonucleoprotein complex. There are parallels to steps in the formation of a much more complex ribonucleoprotein, the 30
S
ribosomal subunit.
rad
-Dependent Response of the
chk1
-Encoded Protein Kinase at the DNA Damage Checkpoint
Authors: Walworth Nancy C. , Bernards Rene
Published: October 2006

Exposure of eukaryotic cells to agents that generate DNA damage results in transient arrest of progression through the cell cycle. In fission yeast, the DNA damage checkpoint associated with cell cycle arrest before mitosis requires the protein kinase p56

chk1

. DNA damage induced by ultraviolet light, gamma radiation, or a DNA-alkylating agent has now been shown to result in phosphorylation of p56

chk1

. This phosphorylation decreased the mobility of p56

chk1

on SDS-polyacrylamide gel electrophoresis and was abolished by a mutation in the p56

chk1

catalytic domain, suggesting that it might represent autophosphorylation. Phosphorylation of p56

chk1

did not occur when other checkpoint genes were inactive. Thus, p56

chk1

appears to function downstream of several of the known
Schizosaccharomyces pombe
checkpoint gene products, including that encoded by
rad3
+
, a gene with sequence similarity to the
ATM
gene mutated in patients with ataxia telangiectasia. The phosphorylation of p56

chk1

provides an assayable biochemical response to activation of the DNA damage checkpoint in the G
2
phase of the cell cycle.
Regulation of
RAD53
by the
ATM
-Like Kinases
MEC1
and
TEL1
in Yeast Cell Cycle Checkpoint Pathways
Authors: Sanchez Yolanda , Desany Brian A. , Jones William J. , Liu Qinghua , Wang Bin , Elledge Stephen J.
Published: October 2006

Mutants of the
Saccharomyces cerevisiae
ataxia telangiectasia mutated (
ATM
) homolog
MEC1/SAD3/ESR1
were identified that could live only if the
RAD53/SAD1
checkpoint kinase was overproduced.
MEC1
and a structurally related gene,
TEL1
, have overlapping functions in response to DNA damage and replication blocks that in mutants can be provided by overproduction of
RAD53
. Both
MEC1
and
TEL1
were found to control phosphorylation of Rad53p in response to DNA damage. These results indicate that
RAD53
is a signal transducer in the DNA damage and replication checkpoint pathways and functions downstream of two members of the
ATM
lipid kinase family. Because several members of this pathway are conserved among eukaryotes, it is likely that a
RAD53
-related kinase will function downstream of the human
ATM
gene product and play an important role in the mammalian response to DNA damage.
Bone Morphogenetic Protein-1: The Type I Procollagen C-Proteinase
Authors: Kessler Efrat , Takahara Kazuhiko , Biniaminov Luba , Brusel Marina , Greenspan Daniel S.
Published: October 2006

Bone morphogenetic proteins (BMPs) are bone-derived factors capable of inducing ectopic bone formation. Unlike other BMPs, BMP-1 is not like transforming growth factor-β (TGF-β), but it is the prototype of a family of putative proteases implicated in pattern formation during development in diverse organisms. Although some members of this group, such as
Drosophila
tolloid (TLD), are postulated to activate TGF-β-like proteins, actual substrates are unknown. Procollagen C-proteinase (PCP) cleaves the COOH-propeptides of procollagens I, II, and III to yield the major fibrous components of vertebrate extracellular matrix. Here it is shown that BMP-1 and PCP are identical. This demonstration of enzymatic activity for a BMP-1/TLD-like protein links an enzyme involved in matrix deposition to genes involved in pattern formation.
Role of β-Arrestin in Mediating Agonist-Promoted G Protein-Coupled Receptor Internalization
Authors: Ferguson Stephen S. G. , Downey William E. , Colapietro Anne-Marie , Barak Larry S. , Ménard Luc , Caron Marc G.
Published: October 2006

β-Arrestins are proteins that bind phosphorylated heterotrimeric GTP-binding protein (G protein)-coupled receptors (GPCRs) and contribute to the desensitization of GPCRs by uncoupling the signal transduction process. Resensitization of GPCR responsiveness involves agonist-mediated receptor sequestration. Overexpression of β-arrestins in human embryonic kidney cells rescued the sequestration of β
2
-adrenergic receptor (β
2
AR) mutants defective in their ability to sequester, an effect enhanced by simultaneous overexpression of β-adrenergic receptor kinase 1. Wild-type β
2
AR sequestration was inhibited by the overexpression of two β-arrestin mutants. These findings suggest that β-arrestins play an integral role in GPCR internalization and thus serve a dual role in the regulation of GPCR function.
Industrial R&D Gets Boost Despite Lack of Patent Reform
Authors: Bagla Pallava
Published: October 2006

New Delhi—The political reforms that have opened up India's economy in the past 4 years to a flood of outside investment are beginning to produce a shift in attitudes toward R&D as well, as local companies recognize the importance of R&D in competing globally.
Proteins 'Clock' the Origins of All Creatures—Great and Small
Authors: Morell Virginia
Published: October 2006

Using a “protein clock,” researchers have dated a basic split in the tree of life, between prokaryotes—cells without nuclei—and eukaryotes, to 2 billion years ago. The results, reported on page
470
of this issue, are at odds with some other studies, which have placed this division anywhere from 3.5 billion to 1.6 billion years ago. The scientists have also used this clock, based on differences among 57 different enzymes found in 15 groups of organisms from bacteria to baboons, to date the origins of all major groups of organisms on the planet.
The Magnetic Nature of Coronal Holes
Authors: Wang Yi-Ming , Hawley Scott H. , Sheeley Neil R.
Published: October 2006

Solar wind streams originate from low-density, magnetically open regions of the sun's corona, known as coronal holes. The locations, areal sizes, rotation, and solar-cycle evolution of these regions can be reproduced and understood by applying simple extrapolation models to measurements of the photospheric magnetic field. The surprisingly rigid rotation displayed by many coronal holes suggests that field-line reconnection occurs continually in the corona, despite the high electrical conductivity of the coronal plasma. The magnetic field strengths and field-line divergence rates in coronal holes can be related empirically to the bulk speed and the mass and energy flux densities of the solar wind plasma. Such relations may help to illuminate the physical processes responsible for heating the corona and driving the solar wind.
Determining Divergence Times of the Major Kingdoms of Living Organisms with a Protein Clock
Authors: Doolittle Russell F. , Feng Da-Fei , Tsang Simon , Cho Glen , Little Elizabeth
Published: October 2006

Amino acid sequence data from 57 different enzymes were used to determine the divergence times of the major biological groupings. Deuterostomes and protostomes split about 670 million years ago and plants, animals, and fungi last shared a common ancestor about a billion years ago. With regard to these protein sequences, plants are slightly more similar to animals than are the fungi. In contrast, phylogenetic analysis of the same sequences indicates that fungi and animals shared a common ancestor more recently than either did with plants, the greater difference resulting from the fungal lineage changing faster than the animal and plant lines over the last 965 million years. The major protist lineages have been changing at a somewhat faster rate than other eukaryotes and split off about 1230 million years ago. If the rate of change has been approximately constant, then prokaryotes and eukaryotes last shared a common ancestor about 2 billion years ago, archaebacterial sequences being measurably more similar to eukaryotic ones than are eubacterial ones.
Reversible Encapsulation of Disc-Shaped Guests by a Synthetic, Self-Assembled Host
Authors: Grotzfeld Robert M. , Branda Neil , Rebek Julius
Published: October 2006

Here, the synthesis of a bowl-shaped molecule is described and evidence of its reversible dimerization by means of hydrogen bonds is presented. The dimer features a flattened spherical cavity of peculiar symmetry and acts as a host for the encapsulation of guest molecules of complementary shape. Encapsulation of aromatic guests in chloroform solution and of cyclohexane in
p
-xylene solution was demonstrated by nuclear magnetic resonance experiments. The passage of guests into and out of the cavity is slow and occurs on a time scale of hours. The system was used to explore the effects of size, shape, and solvation on molecular recognition coupled with assembly.
Redox Stabilization of the Atmosphere and Oceans by Phosphorus-Limited Marine Productivity
Authors: Van Cappellen Philippe , Ingall Ellery D.
Published: October 2006

Data from modern and ancient marine sediments demonstrate that burial of the limiting nutrient phosphorus is less efficient when bottom waters are low in oxygen. Mass-balance calculations using a coupled model of the biogeochemical cycles of carbon, phosphorus, oxygen, and iron indicate that the redox dependence of phosphorus burial in the oceans provides a powerful forcing mechanism for balancing production and consumption of atmospheric oxygen over geologic time. The oxygen-phosphorus coupling further guards against runaway ocean anoxia. Phosphorus-mediated redox stabilization of the atmosphere and oceans may have been crucial to the radiation of higher life forms during the Phanerozoic.
Dependence of Cyclin E-CDK2 Kinase Activity on Cell Anchorage
Authors: Fang Fang , Orend Gertraud , Watanabe Nobumoto , Hunter Tony , Ruoslahti Erkki
Published: October 2006

Most nonmalignant cells are anchorage-dependent; they require substrate attachment for growth and, in some instances, survival. This requirement is lost on oncogenic transformation. The cyclin E-CDK2 complex, which is required for the G
1
-S transition of the cell cycle, was activated in late G
1
phase in attached human fibroblasts, but not in fibroblasts maintained in suspension. In transformed fibroblasts the complex was active regardless of attachment. The lack of cyclin E-CDK2 activity in suspended cells appeared to result from increased expression of CDK2 inhibitors and a concomitant decrease in phosphorylation of CDK2 on threonine-160. Suppression of cyclin E-CDK2 activity may thus underlie the anchorage dependence of cell growth.
Identification of Scavenger Receptor SR-BI as a High Density Lipoprotein Receptor
Authors: Acton Susan , Rigotti Attilio , Landschulz Katherine T. , Xu Shangzhe , Hobbs Helen H. , Krieger Monty
Published: October 2006

High density lipoprotein (HDL) and low density lipoprotein (LDL) are cholesterol transport particles whose plasma concentrations are directly (LDL) and inversely (HDL) correlated with risk for atherosclerosis. LDL catabolism involves cellular uptake and degradation of the entire particle by a well-characterized receptor. HDL, in contrast, selectively delivers its cholesterol, but not protein, to cells by unknown receptors. Here it is shown that the class B scavenger receptor SR-BI is an HDL receptor. SR-BI binds HDL with high affinity, is expressed primarily in liver and nonplacental steroidogenic tissues, and mediates selective cholesterol uptake by a mechanism distinct from the classic LDL receptor pathway.
Interfering with Apoptosis: Ca
2+
-Binding Protein ALG-2 and Alzheimer's Disease Gene
ALG-3
Authors: Vito Pasquale , Lacaná Emanuela , D'Adamio Luciano
Published: October 2006

Two apoptosis-linked genes, named
ALG-2
and
ALG-3
, were identified by means of a functional selection strategy.
ALG-2
codes for a Ca
2+
-binding protein required for T cell receptor-, Fas-, and glucocorticoid-induced cell death.
ALG-3
, a partial complementary DNA that is homologous to the familial Alzheimer's disease gene
STM2
, rescues a T cell hybridoma from T cell receptor- and Fas-induced apoptosis. These findings suggest that
ALG-2
may mediate Ca
2+
-regulated signals along the death pathway and that cell death may play a role in Alzheimer's disease.
Clinical Promise, Ethical Quandary
Authors: Marshall Eliot
Published: October 2006

Blood from the umbilical cord seems to offer a promising — and perhaps safer—alternative to bone marrow for transplants to treat a variety of life-threatening diseases. But the growth of cord blood banking raises some tough practical and ethical questions: Should donors’ families give consent for genetic tests on the cells? Should the donor be told the results of these tests, and how can his or her privacy be protected? How can quality standards be enforced for centers assembling banks of cord blood?
Private Cord Blood Banks Raise Concern
Authors: Marshall Eliot
Published: October 2006

The promise of umbilical cord blood for treating a variety of life-threatening diseases has resulted in the establishment of private cord blood banks, offering parents the chance to bank their baby's cord blood for possible later use by the donor or his or her family. Transplant physicians argue, however, that the chances that the blood will be needed within the family are remote, and they worry that the private banks will diminish the supply of cord blood for transplants to unrelated recipients.
Research Knows No Season As Budget Cycle Goes Awry
Authors: Lawler Andrew
Published: October 2006

The ongoing budget battle between President Clinton and the Republican Congress has postponed release of the president's 1997 budget, left many agencies with temporary budgets for the current year, and disrupted the normal pattern of business in Washington. Research advocates are growing fearful that science may get lost in the shuffle
Fertile Results: Bringing Up Baby (Eggs)
Authors: Roush Wade
Published: October 2006

Biologists are proud to announce two births: a healthy mouse pup and a new era of reproductive biology. The mouse is the first product of an egg grown in vitro all the way from its primordial precursor, or oocyte, to maturity, when it was fertilized. Scientists are excited by the promise of such “oocyte farming”: This means more opportunities for in vitro fertilization—because mammals produce many more oocytes than mature eggs—and a new window on oocyte development.
Carbon Dioxide Extraction of Biomolecules
Authors: Beckman Eric J.
Published: October 2006

Carbon dioxide has become an important environmentally safe solvent for chemical processing, but many biomolecules are insoluble in it. In his Perspective, Beckman describes work reported in this issue of
Science
by Johnston
et al.
(p. 624) in which a fluoroether surfactant was used to create micelles—little pockets of water that contain the biomolecules—that are soluble in CO
2
.
Group Velocity in Strongly Scattering Media
Authors: Page J. H. , Sheng Ping , Schriemer H. P. , Jones I. , Jing Xiaodun , Weitz D. A.
Published: October 2006

Investigation of the ballistic propagation of acoustic waves through a resonantly scattering, inhomogeneous medium indicates that although the ballistic signal remains coherent with the incident pulse, it is nevertheless strongly affected by scattering resonances. These resonances cause considerable frequency dispersion and substantially reduce the phase and group velocities. The experimental data are quantitatively described by a theoretical model that correctly accounts for the coupling between the resonant scatterers, leading to an effective renormalization of the scattering within the medium. This approach resolves a long-standing problem in the definition of the group velocity in strongly scattering materials.
Calcification in Hermatypic and Ahermatypic Corals
Authors: Marshall A. T.
Published: October 2006

The evolutionary development of tropical coral reefs is presently ascribed to the association of corals with symbiotic algae (zooxanthellae) and to the enhancement of calcification by light. Contrary to this idea, the calcification rate in a non-reef-building tropical coral (
Tubastrea faulkneri
) without symbiotic algae was the same as the light-enhanced rate in a zooxanthellate reef-building coral (
Galaxea fascicularis
). The mechanisms of calcification, however, differed between the two species. Instead of being “light-enhanced,” calcification in corals with algae was “dark-repressed.” The evolutionary development of coral reefs may therefore not be related to light-enhanced calcification resulting from the association of corals with symbiotic algae.
Evolution of Scleractinian Corals Inferred from Molecular Systematics
Authors: Romano Sandra L. , Palumbi Stephen R.
Published: October 2006

Scleractinian corals have a continuous fossil record from the mid-Triassic, but taxonomic difficulties have impeded an understanding of their evolution. A molecular phylogenetic analysis of mitochondrial 16
S
ribosomal RNA showed departures from previous hypotheses of coral evolution. Families clustered into two major groups that do not correspond to morphologically based suborders. These clades differed in their 16
S
ribosomal DNA sequence by 29.4 percent, which suggests evolutionary divergence before the appearance of scleractinian skeletons 240 million years ago. Together, these fossil and molecular data suggest multiple origins of the scleractinian skeleton, and the great morphological diversity of present-day scleractinians may be a reflection of these multiple origins.
Enhanced Perception of Illusory Contours in the Lower Versus Upper Visual Hemifields
Authors: Rubin Nava , Nakayama Ken , Shapley Robert
Published: October 2006

The visual world consciously perceived is very different from the spatial array of photoreceptor activation present on our retinae; it is composed of segregated surfaces, organized into distinct objects. An important component of this organizational process, the segmentation of an image into figures and background, is shown to be performed much better in the lower visual field. This finding is demonstrated by the performance in two tasks that involve the perception of illusory contours. This asymmetry indicates a neural specialization that may be related to the anatomical discontinuity along the representation of the horizontal meridian in extrastriate visual cortex.
IRS-1-Mediated Inhibition of Insulin Receptor Tyrosine Kinase Activity in TNF-α- and Obesity-Induced Insulin Resistance
Authors: Hotamisligil Gökhan S. , Peraldi Pascal , Budavari Adriane , Ellis Ramsey , White Morris F. , Spiegelman Bruce M.
Published: October 2006

Tumor necrosis factor-α (TNF-α) is an important mediator of insulin resistance in obesity and diabetes through its ability to decrease the tyrosine kinase activity of the insulin receptor (IR). Treatment of cultured murine adipocytes with TNF-α was shown to induce serine phosphorylation of insulin receptor substrate 1 (IRS-1) and convert IRS-1 into an inhibitor of the IR tyrosine kinase activity in vitro. Myeloid 32D cells, which lack endogenous IRS-1, were resistant to TNF-α-mediated inhibition of IR signaling, whereas transfected 32D cells that express IRS-1 were very sensitive to this effect of TNF-α. An inhibitory form of IRS-1 was observed in muscle and fat tissues from obese rats. These results indicate that TNF-α induces insulin resistance through an unexpected action of IRS-1 to attenuate insulin receptor signaling.
A Familiar Face for a Distant Galaxy?
Authors: Appenzeller Tim
Published: October 2006

A team of astronomers from the California Institute of Technology has discovered what appears to be a full-fledged spiral galaxy that existed when the universe was only about 10% of its current age. If so, the finding would contradict accepted theories of galaxy formation. Researchers are therefore looking for alternative explanations for the observation.
Results on New AIDS Drugs Bring Cautious Optimism
Authors: Cohen Jon
Published: October 2006

Early clinical trials have indicated that a potential new class of AIDS drugs, known as the protease inhibitors, may both decrease the amount of HIV in patients' blood and possibly decrease disease and death by as much as 50%. Those findings, combined with others showing that people with lower viral loads fare better than people who have a lot of virus in their blood, have encouraged AIDS researchers, although given the previous ups and downs of the first AIDS drug, AZT, they remain cautious about the future prospects of the protease inhibitors.
Where Do Meteorites Come From? A NEAR Miss May Tell
Authors: Kerr Richard A.
Published: October 2006

Meteorites have pelted Earth from space for billions of years, but the identity of their source has long stumped planetary scientists. To pin it down, scientists intend to throw something back: the Near-Earth Asteroid Rendezvous (NEAR) spacecraft. Later this month, NEAR will begin a 3-year journey to the asteroid Eros, using remote sensing to match the asteroid's composition against Earth's meteorites. But critics say NEAR's orbit—just 30 kilometers above the asteroid—is still too far, and the only way to get a solid answer is to collect a surface sample—a much more expensive proposition.
Do Galaxies Fly Through the Universe in Formation?
Authors: Matthews Robert
Published: October 2006

Oxford, U.K.—A pair of British astronomers say they have found the best evidence yet for a controversial claim that the speeds at which distant galaxies are receding from Earth are “quantized“—all are multiples of one fundamental velocity. In standard cosmology, there's no reason why these speeds, the result of the expansion of the universe, should be quantized. But a study of more than 200 galaxies revealed that their velocities clustered strongly around multiples of 37.5 kilometers per second. Other astronomers are intrigued but cautious.
Moving Forest Trees Into the Modern Genetics Era
Authors: Moffat Anne Simon
Published: October 2006

Because of their large sizes, slow growth, and huge genomes, trees, especially forest species, have received little benefit from the gene transfer methods that have proved so useful for improving small crop plants. But new methods in gene mapping have opened the way to rapid identification of tree genes that confer desirable traits, a development that may aid both conventional tree breeding and the ultimate genetic engineering of a wide variety of improved tree strains.
Science Journals Go Wired
Authors: Taubes Gary
Published: October 2006

The on-line journals that publishers are launching by the hundreds are transforming science communication by turning journals into perpetual electronic seminars and weaving them into a single interconnected database. This two-part report also examines a trend that may threaten established publishers: the rise of free, on-line preprint archives and efforts to transform them into low-cost, fully refereed journals. The full text also provides hot-links to relevant sites.
Intercalation, DNA Kinking, and the Control of Transcription
Authors: Werner Milton H. , Gronenborn Angela M. , Clore G. Marius
Published: October 2006

Biological processes involved in the control and regulation of transcription are dependent on protein-induced distortions in DNA structure that enhance the recruitment of proteins to their specific DNA targets. This function is often accomplished by accessory factors that bind sequence specifically and locally bend or kink the DNA. The recent determination of the three-dimensional structures of several protein-DNA complexes, involving proteins that perform such architectural tasks, brings to light a common theme of side chain intercalation as a mechanism capable of driving the deformation of the DNA helix. The protein scaffolds orienting the intercalating side chain (or side chains) are structurally diverse, presently comprising four distinct topologies that can accomplish the same task. The intercalating side chain (or side chains), however, is exclusively hydrophobic. Intercalation can either kink or bend the DNA, unstacking one or more adjacent base pairs and locally unwinding the DNA over as much as a full turn of helix. Despite these distortions, the return to B-DNA helical parameters generally occurs within the adjacent half-turns of DNA.
Rapid Collapse of Northern Larsen Ice Shelf, Antarctica
Authors: Rott Helmut , Skvarca Pedro , Nagler Thomas
Published: October 2006

In January 1995, 4200 square kilometers of the northern Larsen Ice Shelf, Antarctic Peninsula, broke away. Radar images from the ERS-1 satellite, complemented by field observations, showed that the two northernmost sections of the ice shelf fractured and disintegrated almost completely within a few days. This breakup followed a period of steady retreat that coincided with a regional trend of atmospheric warming. The observations imply that after an ice shelf retreats beyond a critical limit, it may collapse rapidly as a result of perturbated mass balance.
Overstretching B-DNA: The Elastic Response of Individual Double-Stranded and Single-Stranded DNA Molecules
Authors: Smith Steven B. , Cui Yujia , Bustamante Carlos
Published: October 2006

Single molecules of double-stranded DNA (dsDNA) were stretched with force-measuring laser tweezers. Under a longitudinal stress of ∼65 piconewtons (pN), dsDNA molecules in aqueous buffer undergo a highly cooperative transition into a stable form with 5.8 angstroms rise per base pair, that is, 70% longer than B-form dsDNA. When the stress was relaxed below 65 pN, the molecules rapidly and reversibly contracted to their normal contour lengths. This transition was affected by changes in the ionic strength of the medium and the water activity or by cross-linking of the two strands of dsDNA. Individual molecules of single-stranded DNA were also stretched giving a persistence length of 7.5 angstroms and a stretch modulus of 800 pN. The overstretched form may play a significant role in the energetics of DNA recombination.
Requirement of an ICE-Like Protease for Induction of Apoptosis and Ceramide Generation by REAPER
Authors: Pronk Gijsbertus J. , Ramer Kevin , Amiri Payman , Williams Lewis T.
Published: October 2006

Genetic studies indicated that the
Drosophila melanogaster
protein REAPER (RPR) controls apoptosis during embryo development. Induction of RPR expression in
Drosophila
Schneider cells rapidly stimulated apoptosis. RPR-mediated apoptosis was blocked by
N
-benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone (Z-VAD-fmk), which suggests that an interleukin-1β converting enzyme (ICE)-like protease is required for RPR function. RPR-induced apoptosis was associated with increased ceramide production that was also blocked by Z-VAD-fmk, which suggests that ceramide generation requires an ICE-like protease as well. Thus, the intracellular RPR protein uses cell death signaling pathways similar to those used by the vertebrate transmembrane receptors Fas (CD95) and tumor necrosis factor receptor type 1.
PKC-Dependent Stimulation of Exocytosis by Sulfonylureas in Pancreatic β Cells
Authors: Eliasson Lena , Renström Erik , Ämmälä Carina , Berggren Per-Olof , Bertorello Alejandro M. , Bokvist Krister , Chibalin Alexander , Deeney Jude T. , Flatt Peter R. , Gäbel Jakob , Gromada Jesper , Larsson Olof , Lindström Per , Rhodes Christopher J. , Rorsman Patrik
Published: October 2006

Hypoglycemic sulfonylureas represent a group of clinically useful antidiabetic compounds that stimulate insulin secretion from pancreatic β cells. The molecular mechanisms involved are not fully understood but are believed to involve inhibition of potassium channels sensitive to adenosine triphosphate (K
ATP
channels) in the β cell membrane, causing membrane depolarization, calcium influx, and activation of the secretory machinery. In addition to these effects, sulfonylureas also promoted exocytosis by direct interaction with the secretory machinery not involving closure of the plasma membrane K
ATP
channels. This effect was dependent on protein kinase C (PKC) and was observed at therapeutic concentrations of sulfonylureas, which suggests that it contributes to their hypoglycemic action in diabetics.
Walker Sets Off Alarm Bells With Efforts to Rein In EOS
Authors: Lawler Andrew
Published: October 2006

Representative Robert Walker (R-PA) is no fan of the Earth Observing System (EOS) program. And his latest attacks have not only angered supporters of the multibillion-dollar effort to monitor the planet's oceans, atmosphere, and land masses from space; they've also raised the specter of politicians influencing scientific judgments about proposed research.
Linacs Offer Straight Line to Future
Authors: Hellemans Alexander
Published: October 2006

Grenoble, France—An international community of x-ray scientists has agreed to stop going around in circles with the next generation of light sources. The new facilities should use linear accelerators (linacs) to accelerate the electrons, then feed them into free-electron lasers (FELs) to produce shorter, more intense pulses than anything now available or in the works.
Star-Watchers Team Up Telescopes for a Sharper View
Authors: Watson Andrew
Published: October 2006

Cambridge, U.K.—A set of four modest telescopes at the University of Cambridge has achieved an astronomical first by merging their light into single images. The technique, known as imaging interferometry, should yield views as sharp as those from a single telescope with a mirror tens or even hundreds of meters across. The first images bear out that promise, showing the binary star Capella at five times the resolution available from the Hubble Space Telescope.
Seismologists Learn the Language of Quakes
Authors: Kerr Richard A.
Published: October 2006

Earthquake researchers have long been eavesdroppers, but until recently they listened mainly to the rumblings and groanings of individual faults. Now they are realizing that to understand what faults are saying, they need to monitor dialogues between a fault and its neighbors. This new way of thinking holds that each individual quake is part of a larger conversation in which a major rupture on one fault can transfer stress to a neighboring one and spark a response from it, or temporarily render it speechless by relieving its stress and imposing decades of quiescence on the region.
Quark Studies Put Theorists in a Spin
Authors: Hellemans Alexander
Published: October 2006

Amsterdam, the Netherlands—Eight years ago, a group of European particle physicists studying the internal structure of protons and neutrons—the building blocks of atomic nuclei collectively known as nucleons—made a startling discovery: The three valence quarks within each nucleon, which define its physical properties, make only a small contribution to its spin. Theorists had long assumed that they defined the spin entirely. Other groups quickly came up with broadly similar conclusions, although their results were sufficiently divergent that many physicists believed there was something wrong with the experiments. Now there's no doubt: Three groups are all reporting that the valence quarks contribute only about 25% of the nucleons' spin. Theorists now consider gluons the prime candidates for the major spin-carriers.
Semiconductor Clusters, Nanocrystals, and Quantum Dots
Authors: Alivisatos A. P.
Published: October 2006

Current research into semiconductor clusters is focused on the properties of quantum dots—fragments of semiconductor consisting of hundreds to many thousands of atoms—with the bulk bonding geometry and with surface states eliminated by enclosure in a material that has a larger band gap. Quantum dots exhibit strongly size-dependent optical and electrical properties. The ability to join the dots into complex assemblies creates many opportunities for scientific discovery.
Magnetic Clusters in Molecular Beams, Metals, and Semiconductors
Authors: Shi Jing , Gider S. , Babcock K. , Awschalom D. D.
Published: October 2006

The evolution of magnetic order from the microscopic to the macroscopic regime may be studied with the use of nanometer-scale clusters. A variety of new techniques can be employed to control the size of the magnetic clusters from the atomic level. Molecular beams are used to construct and measure the magnetic properties of isolated metallic clusters. Superparamagnetic metallic particles embedded in a metal exhibit dramatic field-dependent changes in electrical conduction, providing a measure of spin-dependent scattering. Related efforts in semiconductor hosts with the use of ion implantation have generated room-temperature ferromagnetic clusters that can be directly imaged by magnetic force microscopy.
Ab Initio Calculations of Fullerenes
Authors: Scuseria Gustavo E.
Published: October 2006

Recent advances in ab initio electronic structure methods have brought about a substantial improvement in the capabilities of quantum chemists to predict and study the properties of clusters. The carbon cages known as fullerenes have been the focus of much attention because of their remarkable properties. This article discusses the application of state-of-the-art methods to representative fullerene problems and summarizes some of the recent advances and current challenges in the use of ab initio algorithms.
When Proteins Receive Deadly Messages at Birth
Authors: Jentsch Stefan
Published: October 2006

Eukaryotic proteins are tagged for degradation by addition of ubiquitin or single amino acids. Now Jentsch discusses a new prokaryotic protein tagging system reported by Keiler
et al.
(
p. 990
) in this issue of
Science
. In this novel tagging pathway, nascent polypeptides, translated from truncated mRNAs lacking stop codons, receive short COOH-terminal peptide tags encoded by a separate RNA, 10Sa RNA.
From Topographies to Dynamics on Multidimensional Potential Energy Surfaces of Atomic Clusters
Authors: Ball Keith D. , Berry R. Stephen , Kunz Ralph E. , Li Feng-Yin , Proykova Ana , Wales David J.
Published: October 2006

Multidimensional potential energy surfaces for systems larger than about 15 atoms are so complex that interpreting their topographies and the consequent dynamics requires statistical analyses of their minima and saddles. Sequences of minimum-saddle-minimum points provide a characterization of such surfaces. Two examples, Ar
19
and (KCI)
32
, illustrate how topographies govern tendencies to form glasses or “focused” structures, for example, crystals or folded proteins. Master equations relate topographies to dynamics. The balance between glass-forming and structure-seeking characters of a potential energy surface seems governed by sawtooth versus staircase topography and the associated collectivity of the growth process after nucleation.
Lamellar Biogels: Fluid-Membrane-Based Hydrogels Containing Polymer Lipids
Authors: Warriner Heidi E. , Idziak Stefan H. J. , Slack Nelle L. , Davidson Patrick , Safinya Cyrus R.
Published: October 2006

A class of lamellar biological hydrogels comprised of fluid membranes of lipids and surfactants with small amounts of low molecular weight poly(ethylene glycol)-derived polymer lipids (PEG-lipids) were studied by x-ray diffraction, polarized light microscopy, and rheometry. In contrast to isotropic hydrogels of polymer networks, these membrane-based birefringent liquid crystalline biogels, labeled L
α
,g
, form the gel phase when water is added to the liquid-like lamellar L
α
phase, which reenters a liquid-like mixed phase upon further dilution. Furthermore, gels with larger water content require less PEG-lipid to remain stable. Although concentrated (∼50 weight percent) mixtures of free PEG (molecular weight, 5000) and water do not gel, gelation does occur in mixtures containing as little as 0.5 weight percent PEG-lipid. A defining signature of the L
α
,g
regime as it sets in from the fluid lamellar Lα phase is the proliferation of layer-dislocation-type defects, which are stabilized by the segregation of PEG-lipids to the defect regions of high membrane curvature that connect the membranes.
Were Thick Galactic Disks Made by Levitation?
Authors: Sridhar S. , Touma J.
Published: October 2006

The thick disk of our galaxy displays kinematic and chemical properties that are intermediate between those of the halo and the (thin) disk stellar populations. Not all disk galaxies have a thick disk. A theory of the origins of a thick disk can potentially provide insights into the physical state of our galaxy in its infancy. Levitation, a process that relies on adiabatic capture into resonance of stellar orbits in a growing disk, is presented as a plausible formation mechanism; a 2:2 resonance between vertical and epicyclic oscillations drifts to large vertical energies as the disk grows adiabatically. Resonant stars levitate several kiloparsecs above the plane, forming a thick disk whose spatial distributions, kinematics, and ages leave unique observational signatures on the sky. The same process can also produce the disk globular cluster system.
Complex Phase Behavior in Solvent-Free Nonionic Surfactants
Authors: Hillmyer Marc A. , Bates Frank S. , Almdal Kristoffer , Mortensen Kell , Ryan Anthony J. , Fairclough J. Patrick A.
Published: October 2006

Unsolvated block copolymers and surfactant solutions are “soft materials” that share a common set of ordered microstructures. A set of polyethyleneoxide-polyethylethylene (PEO-PEE) block copolymers that are chemically similar to the well-known alkane-oxyethylene (C

n

EO

m

) nonionic surfactants was synthesized here. The general phase behavior in these materials resembles that of both higher molecular weight block copolymers and lower molecular weight nonionic surfactant solutions. Two of the block copolymers exhibited thermally induced order-order transitions and were studied in detail by small-angle scattering. The fundamental microstructural spacing was determined to be a crucial parameter in these transitions. Transitions from one ordered state to another occur only when the lattice spacing is nearly matched. These materials highlight the importance of epitaxy and molecular conformation in the phase transformations of soft material.