bluuebunny/crossref_metadata_2025 huggingface dataset:
Structural Basis of Light Harvesting by Carotenoids: Peridinin-Chlorophyll-Protein from

Amphidinium carterae
Authors: Hofmann Eckhard , Wrench Pamela M. , Sharples Frank P. , Hiller Roger G. , Welte Wolfram , Diederichs Kay
Published: October 2006

Peridinin-chlorophyll-protein, a water-soluble light-harvesting complex that has a blue-green absorbing carotenoid as its main pigment, is present in most photosynthetic dinoflagellates. Its high-resolution (2.0 angstrom) x-ray structure reveals a noncrystallographic trimer in which each polypeptide contains an unusual jellyroll fold of the α-helical amino- and carboxyl-terminal domains. These domains constitute a scaffold with pseudo-twofold symmetry surrounding a hydrophobic cavity filled by two lipid, eight peridinin, and two chlorophyll
a
molecules. The structural basis for efficient excitonic energy transfer from peridinin to chlorophyll is found in the clustering of peridinins around the chlorophylls at van der Waals distances.
Binding of Zinc Finger Protein ZPR1 to the Epidermal Growth Factor Receptor
Authors: Galcheva-Gargova Zoya , Konstantinov Konstantin N. , Wu I-Huan , Klier F. George , Barrett Tamera , Davis Roger J.
Published: October 2006

ZPR1 is a zinc finger protein that binds to the cytoplasmic tyrosine kinase domain of the epidermal growth factor receptor (EGFR). Deletion analysis demonstrated that this binding interaction is mediated by the zinc fingers of ZPR1 and subdomains X and XI of the EGFR tyrosine kinase. Treatment of mammalian cells with EGF caused decreased binding of ZPR1 to the EGFR and the accumulation of ZPR1 in the nucleus. The effect of EGF to regulate ZPR1 binding is dependent on tyrosine phosphorylation of the EGFR. ZPR1 therefore represents a prototype for a class of molecule that binds to the EGFR and is released from the receptor after activation.
Markers on Distal Chromosome 2q Linked to Insulin-Dependent Diabetes Mellitus
Authors: Morahan Grant , Huang Dexing , Tait Brian D. , Colman Peter G. , Harrison Leonard C.
Published: October 2006

Insulin-dependent diabetes mellitus (IDDM) is a multigenic autoimmune disease. An IDDM susceptibility gene was mapped to chromosome 2q34. This gene may act early in diabetogenesis, because “preclinical” individuals also showed linkage. Human leukocyte antigen (HLA)-disparate, but not HLA-identical, sibs showed linkage, which was even stronger in families with affected females. The genes encoding insulin-like growth factor-binding proteins 2 and 5 were mapped to a 4-megabase pair interval near this locus. These results indicate the existence of a gene that acts at an early stage in IDDM development, screening for which may identify a specific subset of at-risk individuals.
Imanishi-Kari Ruling Slams ORI
Authors: Kaiser Jocelyn , Marshall Eliot
Published: October 2006

Tufts University immunologist Thereza Imanishi-Kari ended “a decade in limbo” when a government board cleared her of 19 charges that she committed scientific misconduct in connection with a 1986 paper in
Cell
. In ruling that the “preponderance of the evidence” did not support the government's case against her, an appeals panel of the Department of Health and Human Services was sharply critical of the actions of HHS's Office of Research Integrity (ORI), which it said presented evidence that was often “irrelevant, of limited probative value, internally inconsistent … or based on unwarranted assumptions.”
Scientists Ponder New Cluster Mission and Uncertain Future
Authors: Gavaghan Helen
Published: October 2006

At two emotional meetings last week, Europe's space scientists debated how best to salvage the Cluster mission to study the Earth's magnetosphere, which was destroyed when Europe's first Ariane 5 launcher veered off course earlier this month. Delegates faced the prospect of compromising other prized missions if they are to salvage Cluster's scientific objectives. To compound their troubles, scientists fear that a proposed internal reorganization at the European Space Agency may see the popular science directorate disbanded all together.
Italian Space Agency Head Ends Term With a Bang
Authors: Biggin Susan
Published: October 2006

Venice—With only days to go before his term as special administrator in charge of Italy's space agency, ASI, comes to an end, engineer Silvano Casini has stirred up a hornets' nest by presenting a 10-year plan for ASI to a parliamentary technology committee in Rome last week. In calling for more international collaboration, Casini's plan flies in the face of recommendations made in February by a government-appointed panel. He drew censure from the research ministry for announcing unapproved proposals without their consent.
Phage Transfer: A New Player Turns Up in Cholera Infection
Authors: Williams Nigel
Published: October 2006

Many cholera bacteria are perfectly benign, but some strains have become deadly pathogens by acquiring packages of genes from elsewhere in their environment. New research on
page 1910
. reveals an agent that may be responsible for this Jekyll-to-Hyde transformation: a bacteriophage, a virus that infects the cholera bacterium itself. This phage carries the genes that encode the toxin that causes the disease's life-threatening diarrhea. The new discovery raises questions about the development of live cholera vaccines and suggests a transfer mechanism for other bacterial virulence genes.
Watching the Earth Move
Authors: Kerr Richard A.
Published: October 2006

Most methods for observing the motions of Earth's crust are planted firmly on the ground or even below it, but researchers have now perfected a space-based technique, an orbiting radar that can reveal even a few centimeters of crustal deformation. The forces behind such minute changes are the same as those that drive massive earthquakes, so the precise measurements made by synthetic aperture radar interferometry will help geophysicists study the workings of deep faults.
Divide and Confer: How Worm Embryo Cells Specialize
Authors: Roush Wade
Published: October 2006

Nashville, Tennessee—The animal embryo faces a daunting task as it implements the architectural plans, inscribed in its DNA, for building a complex, multicelled body from the original single-celled zygote. Only for the fruit fly do researchers have a good idea of how early embryonic cells get the marching orders that tell them what cells and tissues they will eventually produce. But at the national meeting of the Society for Developmental Biology here 3 weeks ago, researchers presented a recent flurry of new results on the tiny worm
Caenorhabditis elegans
. The new insights they provide into how early developmental fate decisions are made in this organism led one researcher to comment that “
C. elegans
is entering the heyday that
Drosophila
entered years ago.”
OAR Gets by With a Little Help From New Guard Friends
Authors: Cohen Jon
Published: October 2006

A new generation of AIDS researchers are not only establishing themselves as leaders in the field, but they are also having an impact on the way the AIDS program is managed. Young researchers, allied with AIDS activists, helped persuade the U.S. Congress to give budgetary power to the National Institutes of Health's Office of AIDS Research (OAR), and they helped shape a recent massive review of NIH's $1.4 billion AIDS portfolio. Its main recommendation: Extramural researchers should have more control over the direction and management of the program.
The Marketplace of HIV/AID$
Authors: Cohen Jon
Published: October 2006

The U.S. Patent and Trademark Office has awarded more than 1500 patents related to HIV and AIDS, and the Food and Drug Administration has approved eight anti-HIV drugs, with a ninth in the wings. Companies are making millions of dollars on tests that screen blood for evidence of HIV and immune system damage.
Science
provides an analysis of the growing AIDS marketplace.
Protease Inhibitors: A Tale of Two Companies
Authors: Cohen Jon
Published: October 2006

A new class of anti-HIV drugs called protease inhibitors offers the most promising therapy so far. In combination with other antiviral drugs, they can reduce virus loads to undetectable levels. The manufacturers of the two leading protease inhibitors, Merck and Abbott, took different routes but arrived at the finishing post at almost exactly the same time.
There Is Plenty of Room Between Two Atom Contacts
Authors: Muller C. J. , Reed M. A.
Published: October 2006

The ability to manipulate matter atom by atom offers possibilities for new electronic devices and for studying new physical phenomena. In their Perspective, Muller and Reed discuss recent experiments in which current flows between contacts made from individual atoms. Such structures may be applicable in new sensor technologies.
Image Representations for Visual Learning
Authors: Beymer David , Poggio Tomaso
Published: October 2006

Computer vision researchers are developing new approaches to object recognition and detection that are based almost directly on images and avoid the use of intermediate three-dimensional models. Many of these techniques depend on a representation of images that induces a linear vector space structure and in principle requires dense feature correspondence. This image representation allows the use of learning techniques for the analysis of images (for computer vision) as well as for the synthesis of images (for computer graphics).
Atmospheric, Evolutionary, and Spectral Models of the Brown Dwarf Gliese 229 B
Authors: Marley M. S. , Saumon D. , Guillot T. , Freedman R. S. , Hubbard W. B. , Burrows A. , Lunine J. I.
Published: October 2006

Theoretical spectra and evolutionary models that span the giant planet-brown dwarf continuum have been computed based on the recent discovery of the brown dwarf Gliese 229 B. A flux enhancement in the 4- to 5-micrometer wavelength window is a universal feature from jovian planets to brown dwarfs. Model results confirm the existence of methane and water in the spectrum of Gliese 229 B and indicate that its mass is 30 to 55 jovian masses. Although these calculations focus on Gliese 229 B, they are also meant to guide future searches for extrasolar giant planets and brown dwarfs.
Experimental Constraints on Recycling of Potassium from Subducted Oceanic Crust
Authors: Schmidt Max W.
Published: October 2006

Petrological experiments on oceanic crust samples characterize the recycling of potassium from mid-ocean ridge basalts and sediments. Metasomatism could develop directly and continuously from subducted potassium-bearing crust from shallow levels to a maximum depth of 300 kilometers. Phengite (a potassium-rich mica) is the principal potassium host at subsolidus conditions. It transports potassium and water to depths of up to 300 kilometers and could yield over the entire depth range potassium-rich fluids or melts (depending on the specific geotherm), which are likely to constitute one of the primary metasomatic agents for generation of calc-alkaline magmas.
Pore Fluid Constraints on the Temperature and Oxygen Isotopic Composition of the Glacial Ocean
Authors: Schrag Daniel P. , Hampt Gretchen , Murray David W.
Published: October 2006

Pore fluids from the upper 60 meters of sediment 3000 meters below the surface of the tropical Atlantic indicate that the oxygen isotopic composition (δ
18
O) of seawater at this site during the last glacial maximum was 0.8 ± 0.1 per mil higher than it is today. Combined with the δ
18
O change in benthic foraminifera from this region, the elevated ratio indicates that the temperature of deep water in the tropical Atlantic Ocean was 4°C colder during the last glacial maximum. Extrapolation from this site to a global average suggests that the ice volume contribution to the change in δ
18
O of foraminifera is 1.0 per mil, which partially reconciles the foraminiferal oxygen isotope record of tropical sea surface temperatures with estimates from Barbados corals and terrestrial climate proxies.
A Chemoautotrophically Based Cave Ecosystem
Authors: Sarbu Serban M. , Kane Thomas C. , Kinkle Brian K.
Published: October 2006

Microbial mats discovered in a ground-water ecosystem in southern Romania contain chemoautotrophic bacteria that fix inorganic carbon, using hydrogen sulfide as an energy source. Analysis of stable carbon and nitrogen isotopes showed that this chemoautotrophic production is the food base for 48 species of cave-adapted terrestrial and aquatic invertebrates, 33 of which are endemic to this ecosystem. This is the only cave ecosystem known to be supported by in situ autotrophic production, and it contains the only terrestrial community known to be chemoautotrophically based.
Late Proterozoic and Paleozoic Tides, Retreat of the Moon, and Rotation of the Earth
Authors: Sonett C. P. , Kvale E. P. , Zakharian A. , Chan Marjorie A. , Demko T. M.
Published: October 2006

The tidal rhythmites in the Proterozoic Big Cottonwood Formation (Utah, United States), the Neoproterozoic Elatina Formation of the Flinders Range (southern Australia), and the Lower Pennsylvanian Pottsville Formation (Alabama, United States) and Mansfield Formation (Indiana, United States) indicate that the rate of retreat of the lunar orbit is
d
ξ/
dt
∼
k
2
sin(2δ) (where ξ is the Earth-moon radius vector,
k
2
is the tidal Love number, and δ is the tidal lag angle) and that this rate has been approximately constant since the late Precambrian. When the contribution to tidal friction from the sun is taken into account, these data imply that the length of the terrestrial day 900 million years ago was ∼18 hours.
T Cell Activation Determined by T Cell Receptor Number and Tunable Thresholds
Authors: Viola Antonella , Lanzavecchia Antonio
Published: October 2006

The requirements for T cell activation have been reported to vary widely depending on the state of the T cell, the type of antigen-presenting cell, and the nature of the T cell receptor (TCR) ligand. A unitary requirement for T cell responses was revealed by measurement of the number of triggered TCRs. Irrespective of the nature of the triggering ligand, T cells "counted" the number of triggered TCRs and responded when a threshold of ∼8000 TCRs was reached. The capacity to reach the activation threshold was severely compromised by a reduction in the number of TCRs. Costimulatory signals lowered the activation threshold to ∼1500 TCRs, thus making T cells more sensitive to antigenic stimulation.
Mapping of Catalytic Residues in the RNA Polymerase Active Center
Authors: Zaychikov Evgeny , Martin Emil , Denissova Ludmila , Kozlov Maxim , Markovtsov Vadim , Kashlev Mikhail , Heumann Hermann , Nikiforov Vadim , Goldfarb Alex , Mustaev Arkady
Published: October 2006

When the Mg
2+
ion in the catalytic center of
Escherichia coli
RNA polymerase (RNAP) is replaced with Fe
2+
, hydroxyl radicals are generated. In the promoter complex, such radicals cleave template DNA near the transcription start site, whereas the β′ subunit is cleaved at a conserved motif NADFDGD (Asn-Ala-Asp-Phe-Asp-Gly-Asp). Substitution of the three aspartate residues with alanine creates a dominant lethal mutation. The mutant RNAP is catalytically inactive but can bind promoters and form an open complex. The mutant fails to support Fe
2+
-induced cleavage of DNA or protein. Thus, the NADFDGD motif is involved in chelation of the active center Mg
2+
.
Centric Heterochromatin and the Efficiency of Achiasmate Disjunction in

Drosophila

Female Meiosis
Authors: Karpen Gary H. , Le Mong-Huong , Le Hiep
Published: October 2006

The chromosomal requirements for achiasmate (nonexchange) homolog disjunction in
Drosophila
female meiosis I have been identified with the use of a series of molecularly defined minichromosome deletion derivatives. Efficient disjunction requires 1000 kilobases of overlap in the centric heterochromatin and is not affected by homologous euchromatin or overall size differences. Disjunction efficiency decreases linearly as heterochromatic overlap is reduced from 1000 to 430 kilobases of overlap. Further observations, including rescue experiments with
nod
kinesin-like protein transgenes, demonstrate that heterochromatin does not act solely to promote chromosome movement or spindle attachment. Thus, it is proposed that centric heterochromatin contains multiple pairing elements that act additively to initiate or maintain the proper alignment of achiasmate chromosomes in meiosis I. How heterochromatin could act to promote chromosome pairing is discussed here.
Longevity, Genes, and Aging
Authors: Jazwinski S. Michal
Published: October 2006

Until recently, biogerontology was a backwater of biology, but progress in the qualitative and quantitative genetic analysis of longevity has led to a revolution in aging research. This research has revealed that extended longevity is frequently associated with enhanced metabolic capacity and response to stress. Moreover, it suggests that there are multiple mechanisms of aging. Because of its complexity, the aging process takes us into the realm of integrative biology, and thus, biogerontology should prove instrumental in deciphering the functional and regulatory circuitry of the sequenced genome.
Oxidative Stress, Caloric Restriction, and Aging
Authors: Sohal Rajindar S. , Weindruch Richard
Published: October 2006

Under normal physiological conditions, the use of oxygen by cells of aerobic organisms generates potentially deleterious reactive oxygen metabolites. A chronic state of oxidative stress exists in cells because of an imbalance between prooxidants and antioxidants. The amount of oxidative damage increases as an organism ages and is postulated to be a major causal factor of senescence. Support for this hypothesis includes the following observations: (i) Overexpression of antioxidative enzymes retards the age-related accrual of oxidative damage and extends the maximum life-span of transgenic
Drosophila melanogaster
. (ii) Variations in longevity among different species inversely correlate with the rates of mitochondrial generation of the superoxide anion radical (O
·−
2
) and hydrogen peroxide. (iii) Restriction of caloric intake lowers steady-state levels of oxidative stress and damage, retards age-associated changes, and extends the maximum life-span in mammals.
Menopause: The Aging of Multiple Pacemakers
Authors: Wise Phyllis M. , Krajnak Kristine M. , Kashon Michael L.
Published: October 2006

Menopause signals the permanent end of menstrual cyclicity in a woman's life. Its impact reaches far beyond just the reproductive system. An understanding of the factors that interact and govern the process of aging in the reproductive system will help us to develop strategies for alleviating the negative aspects of menopause and may help us to better comprehend the process of biological aging.
Mechanisms and Evolution of Aging
Authors: Lithgow Gordon J. , Kirkwood Thomas B.L.
Published: October 2006

In their Perspective, Lithgow and Kirkwood postulate that evolutionary theory predicts that the process of aging is not subject to selection in the same way as other physiological processes such as development. They then describe the genetics of aging in the worm
Caenorhabditis elegans
and how what we know about the functions of the genes that have been identified as controlling life-span support this notion.
Direct, Nondestructive Observation of a Bose Condensate
Authors: Andrews M. R. , Mewes M.-O. , van Druten N. J. , Durfee D. S. , Kurn D. M. , Ketterle W.
Published: October 2006

The spatial observation of a Bose condensate is reported. Dispersive light scattering was used to observe the separation between the condensed and normal components of the Bose gas inside a magnetic trap. This technique is nondestructive, and about a hundred images of the same condensate can be taken. The width of the angular distribution of scattered light increased suddenly at the phase transition.
Detrital Zircon Link Between Headwaters and Terminus of the Upper Triassic Chinle-Dockum Paleoriver System
Authors: Riggs N. R. , Lehman T. M. , Gehrels G. E. , Dickinson W. R.
Published: October 2006

New detrital-zircon geochronologic data reveal that a through-going paleoriver connected Texas with Nevada in Late Triassic time. Sandstone from the Upper Triassic Santa Rosa Sandstone (Dockum Group) from northwestern Texas contains a detrital zircon suite nearly identical to that found in western Nevada in the Upper Triassic Osobb Formation (Auld Lang Syne Group, correlative with the Chinle Formation). The Santa Rosa Sandstone was derived in large part from the eroded Cambrian core of the Amarillo-Wichita uplift, as evidenced by abundant zircons with ages of 515 to 525 million years. Other zircon grains in the sandstone are Permian, Devonian, Proterozoic, and Archean in age and, with the exception of the Archean grain, are also matched by the population in the Nevada strata.
Maya Blue Paint: An Ancient Nanostructured Material
Authors: José-Yacamán M. , Rendón Luis , Arenas J. , Puche Mari Carmen Serra
Published: October 2006

Maya blue paint was often used in Mesoamerica. The origin of its color and its resistance to acids and biocorrosion have not been fully understood. High-resolution transmission electron microscopy, electron energy loss spectroscopy, and x-ray microanalysis studies of authentic samples show that palygorskite crystals in the paint form a superlattice that probably occurs as a result of mixing with indigo molecules. An amorphous silicate substrate contains inclusions of metal nanoparticles encapsulated in the substrate and oxide nanoparticles on the surface. The beautiful tone of the color is obtained only when both the particles and the superlattice are present.
Bipartite Ca
2+
-Binding Motif in C
2
Domains of Synaptotagmin and Protein Kinase C
Authors: Shao Xuguang , Davletov Bazbek A. , Sutton R. Bryan , Südhof Thomas C. , Rizo Josep
Published: October 2006

C
2
domains are found in many proteins involved in membrane traffic or signal transduction. Although C
2
domains are thought to bind calcium ions, the structural basis for calcium binding is unclear. Analysis of calcium binding to C
2
domains of synaptotagmin I and protein kinase C-β by nuclear magnetic resonance spectroscopy revealed a bipartite calcium-binding motif that involves the coordination of two calcium ions by five aspartate residues located on two separate loops. Sequence comparisons indicated that this may be a widely used calcium-binding motif, designated here as the C
2
motif.
Giant Atoms Cast Long Shadow
Authors: Amato Ivan
Published: October 2006

A whole community of physicists is under the spell of the oversized atoms called Rydberg atoms. Created when one or sometimes two of their electrons is excited to very high energy levels, far from the nuclear core, Rydberg atoms can detect subtle electric fields and probe chemical reactions that ordinarily proceed too fast for study. And because their outermost electrons sometimes orbit the nucleus like planets orbiting the sun—a behavior reminiscent of classical physics, not the quantum physics of the atom—physicists are using Rydberg atoms to study the border between the quantum and classical worlds.
Throwing—or Molding—a Curve Into Nanofabrication
Authors: Service Robert F.
Published: October 2006

Today's nanotechnology experts are finally beginning to imitate their Iron Age predecessors, casting forms in molds rather than carving these same shapes over and over. That lesson hasn't been easy to apply to the modern lilliputian worlds of micromachines and optics, where engineers and others use light beams, chemicals, and related tools to carve out tiny features in device after device. Now, however, a team of researchers reports on page
347
the development of a new micromolding technique to produce complex patterns known as gratings, just hundreds of nanometers in width, on the surface of both flat and curved optical material. Flat gratings are crucial to laser steering devices, and curved gratings can be used on lens surfaces and optical fibers to focus and filter light for telecommunications and optical computing applications.
Psychiatric Drug Development in Japan
Authors: Berger Douglas , Fukunishi Isao
Published: October 2006

A wide variety of drugs prescribed by psychiatrists in Western countries are not yet available in Japan. The manufacturers of these drugs are often reluctant to conduct the expensive clinical trials required by the Japanese government for their approval; they have already incurred such expenses in other countries, and the market for psychiatric drugs in Japan can be uncertain. Moreover, the Japanese clinical trial system has many methodological problems, which the government has only now started to address. An international agreement to make the results of drug trials reciprocal among participating countries would reduce costs for governments as well as drug manufacturers.
Mechanosensation and the DEG/ENaC Ion Channels
Authors: Corey David P. , García-Añoveros Jaime
Published: October 2006

Cloning of a new protein that participates in mechanosensation in
Caenorhabditis elegans
(see J. Liu
et al
.,
p. 361
) prompts this Perspective's discussion of the superfamily of ion channels that underlie this receptive process and the parallels between mechanosensation in worms and vertebrates.
Excitation Gap in the Normal State of Underdoped Bi
2
Sr
2
CaCu
2
O
8+
δ
Authors: Loeser A. G. , Shen Z.-X. , Dessau D. S. , Marshall D. S. , Park C. H. , Fournier P. , Kapitulnik A.
Published: October 2006

Angle-resolved photoemission experiments reveal evidence of an energy gap in the normal state excitation spectrum of the cuprate superconductor Bi
2
Sr
2
CaCu
2
O
8+
δ
. This gap exists only in underdoped samples and closes around the doping level at which the superconducting transition temperature
T
c
is a maximum. The momentum dependence and magnitude of the gap closely resemble those of the
d

x

2

−

y

2

gap observed in the superconducting state. This observation is consistent with results from several other experimental techniques, which also indicate the presence of a gap in the normal state. Some possible theoretical explanations for this effect are reviewed.
A Magnetic Signature at Io: Initial Report from the Galileo Magnetometer
Authors: Kivelson M. G. , Khurana K. K. , Walker R. J. , Russell C. T. , Linker J. A. , Southwood D. J. , Polanskey C.
Published: October 2006

During the inbound pass of the Galileo spacecraft, the magnetometer acquired 1 minute averaged measurements of the magnetic field along the trajectory as the spacecraft flew by Io. A field decrease, of nearly 40 percent of the background jovian field at closest approach to Io, was recorded. Plasma sources alone appear incapable of generating perturbations as large as those observed and an induced source for the observed moment implies an amount of free iron in the mantle much greater than expected. On the other hand, an intrinsic magnetic field of amplitude consistent with dynamo action at Io would explain the observations. It seems plausible that Io, like Earth and Mercury, is a magnetized solid planet.
Immunostimulatory DNA Sequences Necessary for Effective Intradermal Gene Immunization
Authors: Sato Yukio , Roman Mark , Tighe Helen , Lee Delphine , Corr Maripat , Nguyen Minh-Duc , Silverman Gregg J. , Lotz Martin , Carson Dennis A. , Raz Eyal
Published: October 2006

Vaccination with naked DNA elicits cellular and humoral immune responses that have a T helper cell type 1 bias. However, plasmid vectors expressing large amounts of gene product do not necessarily induce immune responses to the encoded antigens. Instead, the immunogenicity of plasmid DNA (pDNA) requires short immunostimulatory DNA sequences (ISS) that contain a CpG dinucleotide in a particular base context. Human monocytes transfected with pDNA or double-stranded oligonucleotides containing the ISS, but not those transfected with ISS-deficient pDNA or oligonucleotides, transcribed large amounts of interferon-α, interferon-β, and interleukin-12. Although ISS are necessary for gene vaccination, they down-regulate gene expression and thus may interfere with gene replacement therapy by inducing proinflammatory cytokines.
Spinal Cord Regeneration
Authors: Young Wise
Published: October 2006

A paper in this week's issue of
Science
(Cheng and Olson,
p. 510
) reports the first hint that truly functional regeneration of the adult spinal cord may be possible, at least in the rat. In his Perspective, Young describes why this demonstration of regeneration is so important but cautions that we have much more work to do before the procedure could be applied to humans.
Rates of DNA-Mediated Electron Transfer Between Metallointercalators
Authors: Arkin M. R. , Stemp E. D. A. , Holmlin R. E. , Barton J. K. , Hörmann A. , Olson E. J. C. , Barbara P. F.
Published: October 2006

Ultrafast emission and absorption spectroscopies were used to measure the kinetics of DNA-mediated electron transfer reactions between metal complexes intercalated into DNA. In the presence of rhodium(III) acceptor, a substantial fraction of photoexcited donor exhibits fast oxidative quenching (>3 × 1010per second). Transient-absorption experiments indicate that, for a series of donors, the majority of back electron transfer is also very fast (∼1010per second). This rate is independent of the loading of acceptors on the helix, but is sensitive to sequence and π stacking. The cooperative binding of donor and acceptor is considered unlikely on the basis of structural models and DNA photocleavage studies of binding. These data show that the DNA double helix differs significantly from proteins as a bridge for electron transfer.
Volatiles from the 1994 Eruptions of Rabaul: Understanding Large Caldera Systems
Authors: Roggensack Kurt , Williams Stanley N. , Schaefer Stephen J. , Parnell Roderic A.
Published: October 2006

The 1994 eruption of Rabaul, in Papua New Guinea, involved a small plinian eruption at Vulcan and a vulcanian eruption on the opposite side of the caldera at Tavurvur. Vulcan's ash leachates indicate seawater interaction that is consistent with earlier observations of low sulfur dioxide emissions and the presence of ice crystals in the initial plinian eruption cloud. In contrast, Tavurvur ash leachates indicate no seawater interaction, and later sulfur dioxide emissions remained high despite low-level eruptive activity. Silicic melt inclusions indicate that the andesitic melt contained about 2 weight percent water and negligible carbon dioxide. Mafic melt inclusions in Tavurvur ash have water and carbon dioxide contents that vary systematically over the course of the eruption. The mafic melt inclusions suggest that a mafic dike intruded from below the silicic chamber and provide further evidence that mafic intrusions drive caldera unrest.
Multicolor Spectral Karyotyping of Human Chromosomes
Authors: Schröck E. , du Manoir S. , Veldman T. , Schoell B. , Wienberg J. , Ferguson-Smith M. A. , Ning Y. , Ledbetter D. H. , Bar-Am I. , Soenksen D. , Garini Y. , Ried T.
Published: October 2006

The simultaneous and unequivocal discernment of all human chromosomes in different colors would be of significant clinical and biologic importance. Whole-genome scanning by spectral karyotyping allowed instantaneous visualization of defined emission spectra for each human chromosome after fluorescence in situ hybridization. By means of computer separation (classification) of spectra, spectrally overlapping chromosome-specific DNA probes could be resolved, and all human chromosomes were simultaneously identified.
A Receptor for the Selective Uptake and Degradation of Proteins by Lysosomes
Authors: Cuervo Ana Maria , Dice J. Fred
Published: October 2006

Multiple pathways of protein degradation operate within cells. A selective protein import pathway exists for the uptake and degradation of particular cytosolic proteins by lysosomes. Here, the lysosomal membrane glycoprotein LGP96 was identified as a receptor for the selective import and degradation of proteins within lysosomes. Specific substrates of this proteolytic pathway bound to the cytosolic tail of a 96-kilodalton lysosomal membrane protein in two different binding assays. Overexpression of human LGP96 in Chinese hamster ovary cells increased the activity of the selective lysosomal proteolytic pathway in vivo and in vitro.
The POU Factor Oct-6 and Schwann Cell Differentiation
Authors: Jaegle Martine , Mandemakers Wim , Broos Ludo , Zwart Ronald , Karis Alar , Visser Pim , Grosveld Frank , Meijer Dies
Published: October 2006

The POU transcription factor Oct-6, also known as SCIP or Tst-1, has been implicated as a major transcriptional regulator in Schwann cell differentiation. Microscopic and immunochemical analysis of sciatic nerves of Oct-6
−/−
mice at different stages of postnatal development reveals a delay in Schwann cell differentiation, with a transient arrest at the promyelination stage. Thus, Oct-6 appears to be required for the transition of promyelin cells to myelinating cells. Once these cells progress past this point, Oct-6 is no longer required, and myelination occurs normally.
Will Pricing Be the Price of a Faster Internet?
Authors: Germain Ellen
Published: October 2006

Clever technology may succeed in opening some fast lanes on the Internet for scientific users who need high capacity. But many Internet researchers say that keeping those fast lanes from clogging like the rest of the Internet will also require a pricing structure, so that when the network is congested, bandwidth will go to the users who pay extra for it. Congestion pricing may conflict with the egalitarian culture of the Internet, but the technology for implementing it is within reach. Computers/Math
Working the Web With a Virtual Lab and Some Java
Authors: Fischman Joshua
Published: October 2006

Computational biology has had a language problem. Its computational tools couldn't talk to each other, complicating life for biologists wanting to do multiple analyses on a single genome or protein sequence. Now the World Wide Web and the Web-based language Java are bringing some relief. At the National Center for Supercomputing Applications at the University of Illinois, a virtual Biology Workbench is bringing data and tools together where Web users can reach them. Meanwhile, Java-based projects are allowing biologists at their own workstations to create sophisticated displays from data retrieved from distant sources. Computers/Math
High-Speed Network Will Link Russia's Far-Flung Universities
Authors: Allakhverdov Andrey
Published: October 2006

Moscow—On 10 June, Russia's far-flung scientific enterprise suddenly seemed a little less dispersed. At a new university computer center in Yaroslavl, northeast of Moscow, science education officials and journalists celebrated the opening of a new Internet center, complete with high-speed links and dozens of workstations. It is one of 30 to be set up all across Russia over the next 5 years in a $130 million initiative jointly financed by George Soros, the American businessman and philanthropist, and the Russian government. Computers/Math
Photoinduced Chemical Dynamics of High-Spin Alkali Trimers
Authors: Higgins John , Callegari Carlo , Reho James , Stienkemeier Frank , Ernst Wolfgang E. , Lehmann Kevin K. , Gutowski Maciej , Scoles Giacinto
Published: October 2006

Nanometer-sized helium droplets, each containing about 10
4
helium atoms, were used as an inert substrate on which to form previously unobserved, spin-3/2 (quartet state) alkali trimers. Dispersed fluorescence measurements reveal that, upon electronic excitation, the quartet trimers undergo intersystem crossing to the doublet manifold, followed by dissociation of the doublet trimer into an atom and a covalently bound singlet dimer. As shown by this work, aggregates of spin-polarized alkali metals represent ideal species for the optical study of fundamental chemical dynamics processes including nonadiabatic spin conversion, change of bonding nature, and unimolecular dissociation.
The Interdependence of Deformational and Thermal Processes in Mountain Belts
Authors: Huerta Audrey D. , Royden Leigh H. , Hodges Kip V.
Published: October 2006

Crustal temperatures within collisional orogens are anomalously high compared with temperatures at comparable depths in stable continents, which is evidence of thermal processes that are fundamental to orogenesis. These temperatures can be explained by the redistribution of crust enriched in heat-producing elements through the accretion of crust from the down-going plate to the upper plate and surface erosion. With the use of geologically reasonable rates, the model results predict high temperatures (over 600°C) and inverted upper-plate geotherms (about 100°C over 20 kilometers) at shallow depths (20 to 40 kilometers) by 25 to 35 million years after collision. This study emphasizes the interdependence of deformational, surficial, and thermal processes.
Mechanism of Phreatic Eruptions at Aso Volcano Inferred from Near-Field Broadband Seismic Observations
Authors: Kaneshima Satoshi , Kawakatsu Hitoshi , Matsubayashi Hirotoshi , Sudo Yasuaki , Tsutsui Tomoki , Ohminato Takao , Ito Hisao , Uhira Koichi , Yamasato Hitoshi , Oikawa Jun , Takeo Minoru , Iidaka Takashi
Published: October 2006

Broadband seismometers deployed at Aso volcano in Japan have detected a hydrothermal reservoir 1 to 1.5 kilometers beneath the crater that is continually resonating with periods as long as 15 seconds. When phreatic eruptions are observed, broadband seismograms elucidate a dynamic interplay between the reservoir and discharging flow along the conduit: gradual pressurization and long-period (∼20 seconds) pulsations of the reservoir during the 100 to 200 seconds before the initiation of the discharge, followed by gradual deflation of the reservoir concurrent with the discharging flow. The hydrothermal reservoir, where water and heat from the deeper magma chamber probably interact, appears to help control the surface activity at Aso volcano.
Function of Myosin-V in Filopodial Extension of Neuronal Growth Cones
Authors: Wang Feng-Song , Wolenski Joseph S. , Cheney Richard E. , Mooseker Mark S. , Jay Daniel G.
Published: October 2006

The molecular mechanisms underlying directed motility of growth cones have not been determined. The role of myosin-V, an unconventional myosin, in growth cone dynamics was examined by chromophore-assisted laser inactivation (CALI). CALI of purified chick brain myosin-V absorbed onto nitrocellulose-coated cover slips inhibited the ability of myosin-V to translocate actin filaments. CALI of myosin-V in growth cones of chick dorsal root ganglion neurons resulted in rapid filopodial retraction. The rate of filopodial extension was significantly decreased, whereas the rate of filopodial retraction was not affected, which suggests a specific role for myosin-V in filopodial extension.
Emergence of Preferred Structures in a Simple Model of Protein Folding
Authors: Li Hao , Helling Robert , Tang Chao , Wingreen Ned
Published: October 2006

Protein structures in nature often exhibit a high degree of regularity (for example, secondary structure and tertiary symmetries) that is absent from random compact conformations. With the use of a simple lattice model of protein folding, it was demonstrated that structural regularities are related to high “designability” and evolutionary stability. The designability of each compact structure is measured by the number of sequences that can design the structure—that is, sequences that possess the structure as their nondegenerate ground state. Compact structures differ markedly in terms of their designability; highly designable structures emerge with a number of associated sequences much larger than the average. These highly designable structures possess “proteinlike” secondary structure and even tertiary symmetries. In addition, they are thermodynamically more stable than other structures. These results suggest that protein structures are selected in nature because they are readily designed and stable against mutations, and that such a selection simultaneously leads to thermodynamic stability.
Forging a Path to Cell Death
Authors: Barinaga Marcia
Published: October 2006

In the body, cell suicide, through a process called apoptosis or programmed cell death, is needed for normal embryonic development and proper immune system function, among other things. But until recently, very little was known about how the command to commit suicide is transmitted from the cell surface, where it's received, to the cell interior, where the apoptosis program is carried out. Now, in a recent burst of activity, a handful of labs have uncovered a complex maze of internal signaling pathways triggered by the death signal receptors. Researchers hope that unraveling these pathways will not only help them better understand the many processes in which apoptosis plays a role, but will also lead to new therapies for diseases, such as cancer and neurodegenerative disorders, in which apoptosis may go awry.
The Argentine Precordillera: A Traveler from the Ouachita Embayment of North American Laurentia
Authors: Thomas William A. , Astini Ricardo A.
Published: October 2006

The Argentine Precordillera is a continental fragment rifted from the Ouachita embayment of the southern margin of Laurentia (North America) during Cambrian time [about 515 million years ago (Ma)] and accreted to the western margin of Gondwana (South America) during Ordovician time (about 455 Ma). Similarities of Cambrian stratigraphic successions and faunas, Grenville basement rocks, and dimensions link the Argentine Precordillera to the Ouachita embayment. Evidence of rifting during Cambrian time and of a wide ocean basin during Ordovician time indicates that the Precordillera traveled as an independent microcontinent to collide with Gondwana.
Tubules-Within-a-Tubule Hierarchical Order of Mesoporous Molecular Sieves in MCM-41
Authors: Lin Hong-Ping , Mou Chung-Yuan
Published: October 2006

The recently discovered mesoporous aluminosilicate MCM-41 consists of hexagonal arrays of nanometer-sized cylindrical pores. It is shown that this material can be synthesized by cooperative condensation of silicate and cylindrical cationic micelles. Careful control of the surfactant-water content and the rate of condensation of silica at high alkalinity resulted in hollow tubules 0.3 to 3 micrometers in diameter. The wall of the tubules consisted of coaxial cylindrical pores, nanometers in size, that are characteristic of those of MCM-41. The formation of this higher order structure may take place through a liquid crystal phase transformation mechanism involving an anisotropic membrane-to-tubule phase change. The hierarchical organization of this “tubules-within-a-tubule” particle texture is similar to that of the frustules of marine diatoms.
Mongolian Tree Rings and 20th-Century Warming
Authors: Jacoby Gordon C. , D'Arrigo Rosanne D. , Davaajamts Tsevegyn
Published: October 2006

A 450-year tree-ring width chronology of Siberian pine (
Pinus sibirica
Du Tour) growing at timberline (2450 meters) in the Tarvagatay Mountains in west central Mongolia shows wide annual growth rings for the recent century. Ecological site observations and comparisons with instrumental temperature records indicate that the ring widths of these trees are sensitive to annual temperature variations. Low-frequency variations in the Tarvagatay tree-ring record are similar to those in a reconstruction of Arctic annual temperatures, which is based on 20 tree-ring width series from northern North America, Scandinavia, and western Russia. The results indicate that recent warming is unusual relative to temperatures of the past 450 years.
A Statistical Model of the Fluctuations in the Geomagnetic Field from Paleosecular Variation to Reversal
Authors: Camps Pierre , Prévot Michel
Published: October 2006

The statistical characteristics of the local magnetic field of Earth during paleosecular variation, excursions, and reversals are described on the basis of a database that gathers the cleaned mean direction and average remanent intensity of 2741 lava flows that have erupted over the last 20 million years. A model consisting of a normally distributed axial dipole component plus an independent isotropic set of vectors with a Maxwellian distribution that simulates secular variation fits the range of geomagnetic fluctuations, in terms of both direction and intensity. This result suggests that the magnitude of secular variation vectors is independent of the magnitude of Earth's axial dipole moment and that the amplitude of secular variation is unchanged during reversals.
Visualization of Slow Axonal Transport in Vivo
Authors: Terada Sumio , Nakata Takao , Peterson Alan C. , Hirokawa Nobutaka
Published: October 2006

In axons, cytoskeletal constituents move by slow transport. However, it remains controversial whether axonal neurofilaments are dynamic structures in which only subunits are transported or whether filaments assemble in the proximal axon and are transported intact as polymers to the axon terminus. To investigate the form neurofilament proteins take during transport, neurons of transgenic mice lacking axonal neurofilaments were infected with a recombinant adenoviral vector encoding epitope-tagged neurofilament M. Confocal and electron microscopy revealed that the virally encoded neurofilament M was transported in unpolymerized form along axonal microtubules. Thus, neurofilament proteins are probably transported as subunits or small oligomers along microtubules, which are major routes for slow axonal transport.
Central Hypotensive Effects of the α
2a
-Adrenergic Receptor Subtype
Authors: MacMillan Leigh B. , Hein Lutz , Smith Marta S. , Piascik Michael T. , Limbird Lee E.
Published: October 2006

α
2
-Adrenergic receptors (α
2
ARs) present in the brainstem decrease blood pressure and are targets for clinically effective antihypertensive drugs. The existence of three α
2
AR subtypes, the lack of subtype-specific ligands, and the cross-reactivity of α
2
AR agonists with imidazoline receptors has precluded an understanding of the role of individual α
2
AR subtypes in the hypotensive response. Gene targeting was used to introduce a point mutation into the α
2a
AR subtype in the mouse genome. The hypotensive response to α
2
AR agonists was lost in the mutant mice, demonstrating that the α
2a
AR subtype plays a principal role in this response.
Functional Uncoupling of Linked Neurotransmitter Effects by Combinatorial Convergence
Authors: Brezina Vladimir , Orekhova Irina V. , Weiss Klaudiusz R.
Published: October 2006

Physiological signaling pathways both diverge and converge—a single neurotransmitter can have multiple effects and multiple transmitters can have the same effects—in the same target cell. Divergence couples the effects of a transmitter together in a relatively fixed ratio. Different physiological circumstances may require a different ratio, however; the coupling must be made modifiable. This can be achieved through convergence. If two transmitters couple the effects in different ratios, then combinations of the transmitters can yield all intermediate ratios of the effects, thus functionally uncoupling them. This mechanism is analyzed in a well-understood, simple invertebrate neuromuscular circuit.
Organic Electroluminescent Devices
Authors: Sheats James R. , Antoniadis Homer , Hueschen Mark , Leonard William , Miller Jeff , Moon Ron , Roitman Daniel , Stocking Andrew
Published: October 2006

Electroluminescence from organic materials has the potential to enable low-cost, full-color flat-panel displays, as well as other emissive products. Some materials have now demonstrated adequate efficiencies (1 to 15 lumens/watt) and lifetimes (>5000 hours) for practical use; however, the factors that govern lifetime remain poorly understood. This article provides a brief review of device principles and applications requirements and focuses on the understanding of reliability issues.