bluuebunny/crossref_metadata_2025 huggingface dataset:
Role of Lipid Polymorphism in Pulmonary Surfactant
Authors: Perkins Walter R. , Dause Richard B. , Parente Roberta A. , Minchey Sharma R. , Neuman Keir C. , Gruner Sol M. , Taraschi Theodore F. , Janoff Andrew S.
Published: October 2006

The development of artificial surfactants for the treatment of respiratory distress syndrome (RDS) requires lipid systems that can spread rapidly from solution to the air-water interface. Because hydration-repulsion forces stabilize liposomal bilayers and oppose spreading, liposome systems that undergo geometric rearrangement from the bilayer (lamellar) phase to the hexagonal II (H
II
) phase could hasten lipid transfer to the air-water interface through unstable transition intermediates. A liposome system containing dipalmitoylphosphatidylcholine was designed; the system is stable at 23°C but undergoes transformation to the H
II
phase as the temperature increases to 37°C. The spreading of lipid from this system to the air-water interface was rapid at 37°C but slow at 23°C. When tested in vivo in a neonatal rabbit model, such systems elicited an onset of action equal to that of native human surfactant. These findings suggest that lipid polymorphic phase behavior may have a crucial role in the effective functioning of pulmonary surfactant.
Hydrogen-Bond Breaking and Proton Exchange in Collisions of Gaseous Formic Acid with Liquid Sulfuric Acid
Authors: Klassen Jane K. , Nathanson Gilbert M.
Published: October 2006

Gas-liquid scattering experiments provide direct observations of the fate of hydrogen-bonding molecules striking the surfaces of acidic liquids. Collisions of gaseous formic acid with concentrated sulfuric acid show that impinging monomers (HCOOH and DCOOD) scatter inelastically from the interface or become trapped by surface H
2
SO
4
. Most trapped DCOOD molecules undergo proton exchange before desorbing from the acid, indicating that gas-surface accommodation almost always leads to reaction with H
2
SO
4
molecules. This proton transfer is not inhibited by dimerization of the formic acid: The dimers readily undergo intramolecular hydrogen bond cleavage and D-H exchange before desorbing from the acid.
The Morphogenesis of Bands and Zonal Winds in the Atmospheres on the Giant Outer Planets
Authors: Cho James Y-K. , Polvani Lorenzo M.
Published: October 2006

The atmospheres of Jupiter, Saturn, Uranus, and Neptune were modeled as shallow layers of turbulent fluid overlying a smooth, spherical interior. With only the observed values of radius, rotation rate, average wind velocity, and mean layer thickness as model parameters, bands and jets spontaneously emerged from random initial conditions. The number, width, and amplitude of the jets, as well as the dominance of anticyclonic vortices, are in good agreement with observations for all four planets.
Detection of Ozone on Ganymede
Authors: Noll Keith S. , Johnson Robert E. , Lane Arthur L. , Domingue Deborah L. , Weaver Harold A.
Published: October 2006

An absorption band at 260 nanometers on the trailing hemisphere of Ganymede, identified as the Hartley band of ozone (O
3
), was measured with the Hubble Space Telescope. The column abundance of ozone, 4.5 × 10
16
per square centimeter, can be produced by ion impacts or by photochemical equilibrium with previously detected molecular oxygen (O
2
). An estimated number density ratio of [O
3
]/[O
2
] ≈ 10
−4
to 10
−3
requires an atmospheric density orders of magnitude higher than upper limits from spacecraft occultation experiments. Apparently, this O
2
-O
3
"atmosphere" is trapped in Ganymede's surface ice, an inference consistent with the shift and broadening of the band compared with the gas-phase O
3
band.
Self-Assembled Smectic Phases in Rod-Coil Block Copolymers
Authors: Chen J. T. , Thomas E. L. , Ober C. K. , Mao G.-p.
Published: October 2006

Rod-coil block copolymers are self-assembling polymers that combine the physics of orientational ordering of rodlike polymers and the microphase separation of coil-coil block copolymers. Several new solid-state morphologies were observed in a series of anionically synthesized model poly(hexyl isocyanate-b-styrene) rod-coil diblock copolymers examined by transmission electron microscopy and selected-area electron diffraction. The rod-coils formed smectic C-like and O-like morphologies with domain sizes ranging from tens of nanometers to almost 1 micrometer. Both structural and orientational changes were found for increasing rod volume fractions. In addition, some morphologies exhibited spontaneous long-range orientational order over many tens of micrometers.
Cytoplasmic Tail-Dependent Localization of CD1b Antigen-Presenting Molecules to MIICs
Authors: Sugita Masahiko , Jackman Robin M. , van Donselaar Elly , Behar Samuel M. , Rogers Rick A. , Peters Peter J. , Brenner Michael B. , Porcelli Steven A.
Published: October 2006

CD1 proteins have been implicated as antigen-presenting molecules for T cell-mediated immune responses, but their intracellular localization and trafficking remain uncharacterized. CD1b, a member of this family that presents microbial lipid antigens of exogenous origin, was found to localize to endocytic compartments that included the same specialized subset of endosomes in which major histocompatibility complex (MHC) class II molecules are proposed to bind endocytosed antigens. Unlike MHC class II molecules, which traffic to antigen-loading endosomal compartments [MHC class II compartments (MIICs)] primarily as a consequence of their association with the invariant chain, localization of CD1b to these compartments was dependent on a tyrosine-based motif in its own cytoplasmic tail.
The Secreted Product of

Xenopus

Gene

lunatic Fringe

, a Vertebrate Signaling Molecule
Authors: Wu Jane Y. , Wen Leng , Zhang Wan-Jiang , Rao Yi
Published: October 2006

Signaling molecules are essential for vertebrate embryonic development. Here, two
Xenopus
homologs of the
Drosophila
gene
fringe
,
lunatic Fringe
(
lFng
) and
radical Fringe
(
rFng
), were identified and the protein product of
lFng
further characterized. The messenger RNA of
lFng
is supplied as a maternal message. Its product is a precursor protein consisting of pre-, pro-, and mature regions. The mature lunatic Fringe protein is secreted extracellularly, and it induced mesodermal tissue formation in animal cap assays. These results indicate that secreted lunatic Fringe can induce mesoderm and reveal that the Fringe proteins are a family of vertebrate signaling molecules.
Resistance to Apoptosis Conferred by Cdk Inhibitors During Myocyte Differentiation
Authors: Wang Jian , Walsh Kenneth
Published: October 2006

Proliferating murine C2C12 myoblasts can undergo either terminal differentiation or programmed cell death under conditions of mitogen deprivation. Unlike myoblasts, differentiated myotubes were resistant to apoptosis. During myogenesis the appearance of the apoptosis-resistant phenotype was correlated with the induction of the cyclin-dependent kinase (Cdk) inhibitor p21
CIP1
but not with the appearance of myogenin, a marker expressed earlier in differentiation. Forced expression of the Cdk inhibitors p21
CIP1
or p16
INK4A
blocked apoptosis during myocyte differentiation. These data indicate that induction of Cdk inhibitors may serve to protect differentiating myocytes from programmed cell death as well as play a role in establishing the postmitotic state.
Interaction Between a Putative Mechanosensory Membrane Channel and a Collagen
Authors: Liu Jingdong , Schrank Bertold , Waterston Robert H.
Published: October 2006

The degenerin family of proteins in
Caenorhabditis elegans
is homologous to subunits of the mammalian amiloride-sensitive epithelial sodium channels. Mutations in nematode degenerins cause cell death, probably because of defects in channel function. Genetic evidence was obtained that the
unc-105
gene product represents a degenerin homolog affecting
C. elegans
muscles and that this putative channel interacts with type IV collagen in the extracellular matrix underlying the muscle cell. This interaction may serve as a mechanism of stretch-activated muscle contraction, and this system could provide a molecular model for the activation of mechanosensitive ion channels.
Role of the

Yersinia pestis

Hemin Storage (

hms

) Locus in the Transmission of Plague by Fleas
Authors: Hinnebusch B. Joseph , Perry Robert D. , Schwan Tom G.
Published: October 2006

Yersinia pestis
, the cause of bubonic plague, is transmitted by the bites of infected fleas. Biological transmission of plague depends on blockage of the foregut of the flea by a mass of plague bacilli. Blockage was found to be dependent on the hemin storage (
hms
) locus.
Yersinia pestis hms
mutants established long-term infection of the flea's midgut but failed to colonize the proventriculus, the site in the foregut where blockage normally develops. Thus, the
hms
locus markedly alters the course of
Y. pestis
infection in its insect vector, leading to a change in blood-feeding behavior and to efficient transmission of plague.
Functional Mimicry of a Protein Hormone by a Peptide Agonist: The EPO Receptor Complex at 2.8 Å
Authors: Livnah Oded , Stura Enrico A. , Johnson Dana L. , Middleton Steven A. , Mulcahy Linda S. , Wrighton Nicholas C. , Dower William J. , Jolliffe Linda K. , Wilson Ian A.
Published: October 2006

The functional mimicry of a protein by an unrelated small molecule has been a formidable challenge. Now, however, the biological activity of a 166-residue hematopoietic growth hormone, erythropoietin (EPO), with its class 1 cytokine receptor has been mimicked by a 20-residue cyclic peptide unrelated in sequence to the natural ligand. The crystal structure at 2.8 Å resolution of a complex of this agonist peptide with the extracellular domain of EPO receptor reveals that a peptide dimer induces an almost perfect twofold dimerization of the receptor. The dimer assembly differs from that of the human growth hormone (hGH) receptor complex and suggests that more than one mode of dimerization may be able to induce signal transduction and cell proliferation. The EPO receptor binding site, defined by peptide interaction, corresponds to the smaller functional epitope identified for hGH receptor. Similarly, the EPO mimetic peptide ligand can be considered as a minimal hormone, and suggests the design of nonpeptidic small molecule mimetics for EPO and other cytokines may indeed be achievable.
Nonlinear Optics in Relativistic Plasmas and Laser Wake Field Acceleration of Electrons
Authors: Umstadter D. , Chen S.-Y. , Maksimchuk A. , Mourou G. , Wagner R.
Published: October 2006

When a terawatt-peak-power laser beam is focused into a gas jet, an electron plasma wave, driven by forward Raman scattering, is observed to accelerate a naturally collimated beam of electrons to relativistic energies (up to 10
9
total electrons, with an energy distribution maximizing at 2 megaelectron volts, a transverse emittance as low as 1 millimeter-milliradian, and a field gradient of up to 2 gigaelectron volts per centimeter). Electron acceleration and the appearance of high-frequency modulations in the transmitted light spectrum were both found to have sharp thresholds in laser power and plasma density. A hole in the center of the electron beam may indicate that plasma electrons were expelled radially.
Crystalline Ropes of Metallic Carbon Nanotubes
Authors: Thess Andreas , Lee Roland , Nikolaev Pavel , Dai Hongjie , Petit Pierre , Robert Jerome , Xu Chunhui , Lee Young Hee , Kim Seong Gon , Rinzler Andrew G. , Colbert Daniel T. , Scuseria Gustavo E. , Tománek David , Fischer John E. , Smalley Richard E.
Published: October 2006

Fullerene single-wall nanotubes (SWNTs) were produced in yields of more than 70 percent by condensation of a laser-vaporized carbon-nickel-cobalt mixture at 1200°C. X-ray diffraction and electron microscopy showed that these SWNTs are nearly uniform in diameter and that they self-organize into "ropes," which consist of 100 to 500 SWNTs in a two-dimensional triangular lattice with a lattice constant of 17 angstroms. The x-ray form factor is consistent with that of uniformly charged cylinders 13.8 ± 0.2 angstroms in diameter. The ropes were metallic, with a single-rope resistivity of <10
−4
ohm-centimeters at 300 kelvin. The uniformity of SWNT diameter is attributed to the efficient annealing of an initial fullerene tubelet kept open by a few metal atoms; the optimum diameter is determined by competition between the strain energy of curvature of the graphene sheet and the dangling-bond energy of the open edge, where growth occurs. These factors strongly favor the metallic (10,10) tube with
C
5

v

symmetry and an open edge stabilized by triple bonds.
Lymphocyte Apoptosis: Mediation by Increased Type 3 Inositol 1,4,5-Trisphosphate Receptor
Authors: Khan Adil A. , Soloski Mark J. , Sharp Alan H. , Schilling Gabriele , Sabatini David M. , Li Shi-Hua , Ross Christopher A. , Snyder Solomon H.
Published: October 2006

B and T lymphocytes undergoing apoptosis in response to anti-immunoglobulin M antibodies and dexamethasone, respectively, were found to have increased amounts of messenger RNA for the inositol 1,4,5-trisphosphate receptor (IP
3
R) and increased amounts of IP
3
R protein. Immunohistochemical analysis revealed that the augmented receptor population was localized to the plasma membrane. Type 3 IP
3
R (IP
3
R3) was selectively increased during apoptosis, with no enhancement of type 1 IP
3
R (IP
3
R1). Expression of IP
3
R3 antisense constructs in S49 T cells blocked dexamethasone-induced apoptosis, whereas IP
3
R3 sense, IP
3
R1 sense, or IP
3
R1 antisense control constructs did not block cell death. Thus, the increases in IP
3
R3 may be causally related to apoptosis.
Mapping the Protein Universe
Authors: Holm Liisa , Sander Chris
Published: October 2006

The comparison of the three-dimensional shapes of protein molecules poses a complex algorithmic problem. Its solution provides biologists with computational tools to organize the rapidly growing set of thousands of known protein shapes, to identify new types of protein architecture, and to discover unexpected evolutionary relations, reaching back billions of years, between protein molecules. Protein shape comparison also improves tools for identifying gene functions in genome databases by defining the essential sequence-structure features of a protein family. Finally, an exhaustive all-on-all shape comparison provides a map of physical attractor regions in the abstract shape space of proteins, with implications for the processes of protein folding and evolution.
X-Ray Photoconductive Nanocomposites
Authors: Wang Ying , Herron Norman
Published: October 2006

The successful development of digital radiography depends, to a large extent, on the availability of suitable x-ray photoconductors. The x-ray photoconductive nanocomposites reported here combine the advantages of both inorganic and organic compounds. An inorganic compound was finely dispersed in an organic polymer. The inorganic compound, with its large x-ray absorption efficiency, functioned as the x-ray absorber, and the polymer provided good dielectric properties and ease of thin-film preparation. The preparation procedures and the x-ray photoconductive properties of a specific example, a 50 percent by weight nanocomposite of bismuth triiodide and nylon-11, are discussed in detail.
A Fluted Point from the Uptar Site, Northeastern Siberia
Authors: King Maureen L. , Slobodin Sergei B.
Published: October 2006

Lanceolate bifacial points, including one fluted specimen, have been collected from beneath an early Holocene tephra at the Uptar site, northeastern Siberia. Thus, the technology associated with the well-known Paleoindian tradition was not confined to the Americas. The Uptar collection does not compare readily with other Beringian complexes and demonstrates that there is greater diversity in the archaeological record of northeastern Siberia than traditional colonization models imply.
Demethylation-Induced Developmental Pleiotropy in

Arabidopsis
Authors: Ronemus Michael J. , Galbiati Massimo , Ticknor Christine , Chen Jychian , Dellaporta Stephen L.
Published: October 2006

The function of DNA methylation in higher plants was investigated by expression of a complementary DNA encoding a cytosine methyltransferase (MET1) from
Arabidopsis thaliana
as an antisense RNA in transgenic plants. This expression resulted in a 34 to 71 percent reduction in total genomic cytosine methylation. Loss of methylation was observed in both repetitive DNA and single-copy gene sequences. Developmental effects included altered heterochrony, changes in meristem identity and organ number, and female sterility. Cytosine demethylation prolonged both vegetative and reproductive phases of development. These findings implicate DNA methylation in establishing or maintaining epigenetic developmental states in the meristem.
Why Stress Is Bad for Your Brain
Authors: Sapolsky Robert M.
Published: October 2006

Several recent studies of humans correlate stress with atrophy of the hippocampus, an area of the brain required for memory and cognition. In his Perspective, Sapolsky argues that the underlying causal agent may be glucocorticoids secreted in abnormally high amounts under stressful conditions.
STATs Find That Hanging Together Can Be Stimulating
Authors: Leung Stewart , Li Xiaoxia , Stark George R.
Published: October 2006

A report in this week's issue of
Science
by Xu
et al
. (
p. 794
) shows that homodimers of various kinds of STATs (signal transducers and activators of transcription) bind to regulatory regions of the gene for the interferon-γ gene, each with a slightly different binding site. In their Perspective, Leung, Li, and Stark explain how these cooperating STAT dimers, which interact via their NH
2
terminals, can determine the specificity of the cytokine response.
Evidence for Widespread
26
Al in the Solar Nebula and Constraints for Nebula Time Scales
Authors: Russell S. S. , Srinivasan G. , Huss G. R. , Wasserburg G. J. , MacPherson G. J.
Published: October 2006

A search was made for
26
Mg (
26
Mg*) from the decay of
26
Al (half-life = 0.73 million years) in Al-rich objects from unequilibrated ordinary chondrites. Two Ca-Al-rich inclusions (CAIs) and two Al-rich chondrules (not CAIs) were found that contained
26
Al when they formed. Internal isochrons for the CAIs yielded an initial
26
Al/
27
Al ratio [(
26
Al/
27
Al)
0
] of 5 × 10
−5
, indistinguishable from most CAIs in carbonaceous chondrites. This result shows that CAIs with this level of
26
Al are present throughout the classes of chondrites and strengthens the notion that
26
Al was widespread in the early solar system. The two Al-rich chondrules have lower
26
Mg*, corresponding to a (
26
Al/
27
Al)
0
ratio of ∼9 × 10
−6
. Five other Al-rich chondrules contain no resolvable
26
Mg*. If chondrules and CAIs formed from an isotopically homogeneous reservoir, then the chondrules with
26
Al must have formed or been last altered ∼2 million years after CAIs formed; the
26
Mg*-free chondrules formed >1 to 3 million years later still. Because
26
Mg*-containing and
26
Mg*-free chondrules are both found in Chainpur, which was not heated to more than ∼400°C, it follows that parent body metamorphism cannot explain the absence of
26
Mg* in some of these chondrules. Rather, its absence indicates that the lifetime of the solar nebula over which CAIs and chondrules formed extended over ∼5 million years.
Single-Electron Parametron: Reversible Computation in a Discrete-State System
Authors: Likharev Konstantin K. , Korotkov Alexander N.
Published: October 2006

The energy dissipation in a proposed digital device in which discrete degrees of freedom are used to represent digital information (a "single-electron parametron") was analyzed. If the switching speed is not too high, the device may operate reversibly (adiabatically), and the energy dissipation E per bit may be much less than the thermal energy scale
k
B
T
(where
k
B
is Boltzmann's constant and
T
is temperature). The energy-time product E
T
" is, however, much greater than Planck's constant
ħ
, at least in the standard "orthodox" model of single-electron tunneling that was used in these calculations.
Subnanometer-Diameter Wires Isolated in a Polymer Matrix by Fast Polymerization
Authors: Golden Josh H. , DiSalvo Francis J. , Fréchet Jean M. J. , Silcox John , Thomas Malcolm , Elman Jim
Published: October 2006

The preparation and analysis of inorganic-organic polymer nanocomposites consisting of inorganic nanowires and multiwire “cables” in a random-coil organic polymer host is reported. Dissolution of inorganic (LiMo
3
Se
3
)
n
wires in a strongly coordinating monomer, vinylene carbonate, and the use of a rapid polymerization in the presence of a cross-linking agent produce nanocomposites without phase separation. Polymerization of dilute solutions yields a material containing mostly (Mo
3
Se
3
−
)

n

mono- and biwires, 6 to 20 angstroms in diameter and 50 to 100 nanometers long. Polymerization of more concentrated liquid crystalline solutions yields a nanocomposite containing oriented multiwire cables, 20 to 40 angstroms in diameter and up to 1500 nanometers long, that display optical anisotropy and electrical conductivity.
Immunodeficiency in Protein Kinase Cβ-Deficient Mice
Authors: Leitges Michael , Schmedt Christian , Guinamard Rodolphe , Davoust Jean , Schaal Stefan , Stabel Silvia , Tarakhovsky Alexander
Published: October 2006

Cross-linking of the antigen receptor on lymphocytes by antigens or antibodies to the receptor results in activation of enzymes of the protein kinase C (PKC) family. Mice homozygous for a targeted disruption of the gene encoding the PKC-βI and PKC-βII isoforms develop an immunodeficiency characterized by impaired humoral immune responses and reduced cellular responses of B cells, which is similar to X-linked immunodeficiency in mice. Thus PKC-βI and PKC-βII play an important role in B cell activation and may be functionally linked to Bruton's tyrosine kinase in antigen receptor-mediated signal transduction.
Diffusional Mobility of Golgi Proteins in Membranes of Living Cells
Authors: Cole Nelson B. , Smith Carolyn L. , Sciaky Noah , Terasaki Mark , Edidin Michael , Lippincott-Schwartz Jennifer
Published: October 2006

The mechanism by which Golgi membrane proteins are retained within the Golgi complex in the midst of a continuous flow of protein and lipid is not yet understood. The diffusional mobilities of mammalian Golgi membrane proteins fused with green fluorescent protein from
Aequorea victoria
were measured in living HeLa cells with the fluorescence photobleaching recovery technique. The diffusion coefficients ranged from 3 × 10
−9
square centimeters per second to 5 × 10
−9
square centimeters per second, with greater than 90 percent of the chimeric proteins mobile. Extensive lateral diffusion of the chimeric proteins occurred between Golgi stacks. Thus, the chimeras diffuse rapidly and freely in Golgi membranes, which suggests that Golgi targeting and retention of these molecules does not depend on protein immobilization.
Organization of Diphtheria Toxin T Domain in Bilayers: A Site-Directed Spin Labeling Study
Authors: Oh Kyoung Joon , Zhan Hangjun , Cui Can , Hideg Kálmán , Collier R. John , Hubbell Wayne L.
Published: October 2006

The diphtheria toxin transmembrane (T) domain was spin-labeled at consecutive residues in a helical segment, TH9. After binding of the T domain to membranes at low pH, the nitroxide side chains generated by spin labeling were measured with respect to their frequency of collision with polar and nonpolar reagents. The data showed that the helical structure of TH9 in solution is conserved, with one face exposed to water and the other to the hydrophobic interior of the bilayer. Measurement of the depth of the nitroxide side chains from the membrane surfaces revealed an incremental change of about 5 angstroms per turn, which is consistent with a transmembrane orientation of an α helix. These results indicate that the helix forms the lining of a transmembrane water-filled channel.
Genome Sequence of a Human Tumorigenic Poxvirus: Prediction of Specific Host Response-Evasion Genes
Authors: Senkevich Tatiana G. , Bugert Joachim J. , Sisler Jerry R. , Koonin Eugene V. , Darai Gholamreza , Moss Bernard
Published: October 2006

Molluscum contagiosum virus (MCV) commonly causes asymptomatic cutaneous neoplasms in children and sexually active adults as well as persistent opportunistic acquired immunodeficiency syndrome (AIDS)-associated disease. Sequencing the 190-kilobase pair genome of MCV has now revealed that the virus potentially encodes 163 proteins, of which 103 have homologs in the smallpox virus. MCV lacks counterparts to 83 genes of the smallpox virus, including those important in suppression of host responses to infection, nucleotide biosynthesis, and cell proliferation. MCV possesses 59 genes that are predicted to encode previously uncharacterized proteins, including major histocompatibility complex class I, chemokine, and glutathione peroxidase homologs, which suggests that there are MCV-specific strategies for coexistence with the human host.
Synthesis of Novel Thin-Film Materials by Pulsed Laser Deposition
Authors: Lowndes Douglas H. , Geohegan D. B. , Puretzky A. A. , Norton D. P. , Rouleau C. M.
Published: October 2006

Pulsed laser deposition (PLD) is a conceptually and experimentally simple yet highly versatile tool for thin-film and multilayer research. Its advantages for the film growth of oxides and other chemically complex materials include stoichiometric transfer, growth from an energetic beam, reactive deposition, and inherent simplicity for the growth of multilayered structures. With the use of PLD, artificially layered materials and metastable phases have been created and their properties varied by control of the layer thicknesses. In situ monitoring techniques have provided information about the role of energetic species in the formation of ultrahard phases and in the doping of semiconductors. Cluster-assembled nanocrystalline and composite films offer opportunities to control and produce new combinations of properties with PLD.
Chemical Solution Routes to Single-Crystal Thin Films
Authors: Lange F. F.
Published: October 2006

Epitaxial thin films of inorganic single crystals can be grown on single-crystal substrates with a variety of different solution chemistries. This review emphasizes chemical solution deposition, in which a solution is used to deposit a layer of precursor molecules that decompose to low-density, polycrystalline films during heating. Ways to control film cracking during deposition and heat treatment and why many precursors synthesize metastable crystalline structures are discussed, and the different mechanisms that convert the polycrystalline film into a single crystal are reviewed. Hydrothermal epitaxy, in which single crystal thin films are directly synthesized on templating substrates in an aqueous solution at temperatures <150°C, is also discussed.
Exclusion of Int-6 from PML Nuclear Bodies by Binding to the HTLV-I Tax Oncoprotein
Authors: Desbois Christelle , Rousset Raphaël , Bantignies Frédéric , Jalinot Pierre
Published: October 2006

The Tax transactivator of the human T cell leukemia virus type I (HTLV-I) exhibits oncogenic properties. A screen for proteins interacting with Tax yielded a complementary DNA (cDNA) encoding the human Int-6 protein. In mice, the
Int-6
gene can be converted into a putative dominant negative oncogene after retroviral insertion. Here, Int-6 was localized in the cell nucleus to give a speckled staining pattern superposed to that of the promyelocytic leukemia (PML) protein. The binding of Tax to Int-6 caused its redistribution from the nuclear domains to the cytoplasm. Thus, Int-6 is a component of the PML nuclear bodies and Tax disrupts its normal cellular localization by binding to it.
Protection Against Atherogenesis in Mice Mediated by Human Apolipoprotein A-IV
Authors: Duverger Nicolas , Tremp Günter , Caillaud Jean-Michel , Emmanuel Florence , Castro Graciela , Fruchart Jean-Charles , Steinmetz Armin , Denèfle Patrice
Published: October 2006

Apolipoproteins are protein constituents of plasma lipid transport particles. Human apolipoprotein A-IV (apoA-IV) was expressed in the liver of C57BL/6 mice and mice deficient in apoE, both of which are prone to atherosclerosis, to investigate whether apoA-IV protects against this disease. In transgenic C57BL/6 mice on an atherogenic diet, the serum concentration of high density lipoprotein (HDL) cholesterol increased by 35 percent, whereas the concentration of endogenous apoA-I decreased by 29 percent, relative to those in transgenic mice on a normal diet. Expression of human apoA-IV in apoE-deficient mice on a normal diet resulted in an even more severe atherogenic lipoprotein profile, without affecting the concentration of HDL cholesterol, than that in nontransgenic apoE-deficient mice. However, transgenic mice of both backgrounds showed a substantial reduction in the size of atherosclerotic lesions. Thus, apoA-IV appears to protect against atherosclerosis by a mechanism that does not involve an increase in HDL cholesterol concentration.
Small Nucleolar RNAs Guide Ribosomal RNA Methylation
Authors: Tollervey David
Published: October 2006

Two recent reports, one in
Cell
and one in the
Journal of Molecular Biology
, show that the newly described small nucleolar RNAs control the site of methylation of the ribosomal RNA (rRNA). Tollervey explains how these small RNAs accomplish this targeting and discusses the possible role of this rRNA modification.
The Representation of Brightness in Primary Visual Cortex
Authors: Rossi Andrew F. , Rittenhouse Cynthia D. , Paradiso Michael A.
Published: October 2006

Although neurons in primary visual cortex are sensitive to the spatial distribution and intensity of light, their responses have not been thought to correlate with the perception of brightness. Indeed, primary visual cortex is often described as an initial processing stage that sends information to higher cortical areas where perception of brightness, color, and form occurs. However, a significant percentage of neurons in primary visual cortex were shown to respond in a manner correlated with perceived brightness, rather than responding strictly to the light level in the receptive fields of the cells. This finding suggests that even at the first stage of visual cortical processing, spatial integration of information yields perceptual qualities that are only indirectly related to the pattern of illumination of the retina.
RNA Editing: A Mechanism for gRNA-Specified Uridylate Insertion into Precursor mRNA
Authors: Kable Moffett L. , Seiwert Scott D. , Heidmann Stefan , Stuart Kenneth
Published: October 2006

In the mitochondria of trypanosomatid protozoa the precursors of messenger RNAs (pre-mRNAs) have their coding information remodeled by the site-specific insertion and deletion of uridylate (U) residues. Small trans-acting guide RNAs (gRNAs) supply the genetic information for this RNA editing. An in vitro system was developed to study the mechanism of U insertion into pre-mRNA. U-insertion editing occurs through a series of enzymatic steps that begin with gRNA-directed pre-mRNA cleavage. Inserted U's are derived from free uridine triphosphate and are added to the 3′ terminus of a 5′ pre-mRNA cleavage product. gRNA specifies edited RNA sequence at the subsequent ligation step by base pairing-mediated juxtaposition of the 3′ cleavage product and the processed 5′ cleavage product. gRNA/pre-mRNA chimeras, purported intermediates, seem to be abortive end products of the same reaction.
Attomole Protein Characterization by Capillary Electrophoresis-Mass Spectrometry
Authors: Valaskovic Gary A. , Kelleher Neil L. , McLafferty Fred W.
Published: October 2006

Electrospray ionization with an ultralow flow rate (≤4 nanoliters per minute) was used to directly couple capillary electrophoresis with tandem mass spectrometry for the analysis and identification of biomolecules in mixtures. A Fourier transform mass spectrometer provided full spectra (>30 kilodaltons) at a resolving power of ≈60,000 for injections of 0.7 × 10
−18
to 3 × 10
−18
mole of 8- to 29-kilodalton proteins with errors of <1 dalton in molecular mass. Using a crude isolate from human blood, a value of 28,780.6 daltons (calculated, 28,780.4 daltons) was measured for carbonic anhydrase, representing 1 percent by weight of the protein in a single red blood cell. Dissociation of molecular ions from 9 × 10
−18
mole of carbonic anhydrase gave nine sequence-specific fragment ions, more data than required for unique retrieval of this enzyme from the protein database.
The Metabolic Status of Some Late Cretaceous Dinosaurs
Authors: Ruben John A. , Hillenius Willem J. , Geist Nicholas R. , Leitch Andrew , Jones Terry D. , Currie Philip J. , Horner John R. , Espe George
Published: October 2006

Analysis of the nasal region in fossils of three theropod dinosaurs (
Nanotyrannus, Ornithomimus,
and
Dromaeosaurus
) and one ornithischian dinosaur (
Hypacrosaurus
) showed that their metabolic rates were significantly lower than metabolic rates in modern birds and mammals. In extant endotherms and ectotherms, the cross-sectional area of the nasal passage scales approximately with increasing body mass
M
at
M
0.72
. However, the cross-sectional area of nasal passages in endotherms is approximately four times that of ectotherms. The dinosaurs studied here have narrow nasal passages that are consistent with low lung ventilation rates and the absence of respiratory turbinates.
Enforcing Coherent Evolution in Dissipative Quantum Dynamics
Authors: Cirac J. I. , Pellizzari T. , Zoller P.
Published: October 2006

The major obstacle to the preparation and manipulation of many-particle entangled states is decoherence due to the coupling of the system to the environment. A scheme to correct for the effects of decoherence and enforce coherent evolution in the system dynamics is described and illustrated for the particular case of the ion-trap quantum computer.
Identification of an Estrogen Response Element Activated by Metabolites of 17β-Estradiol and Raloxifene
Authors: Yang Na N. , Venugopalan Murali , Hardikar Sushant , Glasebrook Andrew
Published: October 2006

17β-Estradiol modulates gene transcription through the estrogen receptor and the estrogen response element in DNA. The human transforming growth factor-β3 gene was shown to be activated by the estrogen receptor in the presence of estrogen metabolites or estrogen antagonists. Activation was mediated by a polypurine sequence, termed the raloxifene response element, and did not require the DNA binding domain of the estrogen receptor. Interaction of the estrogen receptor with the raloxifene response element appears to require a cellular adapter protein. The observation that individual estrogens modulate multiple DNA response elements may explain the tissue-selective estrogen agonist or antagonist activity of compounds such as raloxifene.
Tourette Syndrome: Prediction of Phenotypic Variation in Monozygotic Twins by Caudate Nucleus D2 Receptor Binding
Authors: Wolf Steven S. , Jones Douglas W. , Knable Michael B. , Gorey Julia G. , Lee Kan Sam , Hyde Thomas M. , Coppola Richard , Weinberger Daniel R.
Published: October 2006

Tourette syndrome, a chronic tic disorder with autosomal dominant inheritance, exhibits considerable phenotypic variability even within monozygotic twin pairs. The origins of this variability remain unclear. Recent findings have implicated the caudate nucleus as a locus of pathology, and pharmacological evidence supports dopaminergic involvement. Within monozygotic twins discordant for Tourette syndrome severity, differences in D2 dopamine receptor binding in the head of the caudate nucleus predicted differences in phenotypic severity (
r
= 0.99); this relation was not observed in putamen. These data may link Tourette syndrome with a spectrum of neuropsychiatric disorders that involve associative striatal circuitry.
Modulation of Virulence Factor Expression by Pathogen Target Cell Contact
Authors: Pettersson Jonas , Nordfelth Roland , Dubinina Elena , Bergman Tomas , Gustafsson Mikael , Magnusson Karl Eric , Wolf-Watz Hans
Published: October 2006

Upon contact with the eukaryotic cell,
Yersinia pseudotuberculosis
increased the rate of transcription of virulence genes (
yop
), as determined by in situ monitoring of light emission from individual bacteria expressing luciferase under the control of the
yopE
promoter. The microbe-host interaction triggered export of LcrQ, a negative regulator of Yop expression, via the Yop-type III secretion system. The intracellular concentration of LcrQ was thereby lowered, resulting in increased expression of Yops. These results suggest a key role for the type III secretion system of pathogenic bacteria to coordinate secretion with expression of virulence factors after physical contact with the target cell.
Pycnodysostosis, a Lysosomal Disease Caused by Cathepsin K Deficiency
Authors: Gelb Bruce D. , Shi Guo-Ping , Chapman Harold A. , Desnick Robert J.
Published: October 2006

Pycnodysostosis, an autosomal recessive osteochondrodysplasia characterized by osteosclerosis and short stature, maps to chromosome 1q21. Cathepsin K, a cysteine protease gene that is highly expressed in osteoclasts, localized to the pycnodysostosis region. Nonsense, missense, and stop codon mutations in the gene encoding cathepsin K were identified in patients. Transient expression of complementary DNA containing the stop codon mutation resulted in messenger RNA but no immunologically detectable protein. Thus, pycnodysostosis results from gene defects in a lysosomal protease with highest expression in osteoclasts. These findings suggest that cathepsin K is a major protease in bone resorption, providing a possible rationale for the treatment of disorders such as osteoporosis and certain forms of arthritis.
Antagonistic Interactions Between Wingless and Decapentaplegic Responsible for Dorsal-Ventral Pattern in the
Drosophila
Leg
Authors: Brook William J. , Cohen Stephen M.
Published: October 2006

Subdivision of the limb primordia of
Drosophila
into anterior and posterior compartments triggers cell interactions that pattern the legs and wings. A comparable compartment-based mechanism is used to pattern the dorsal-ventral axis of the wing. Evidence is presented here for a mechanism based on cell interaction, rather than on compartment formation, that distinguishes dorsal from ventral in the leg. Mutual repression by Wingless and Decapentaplegic signaling systems generates a stable regulatory circuit by which each gene maintains its own expression in a spatially restricted domain. Compartment-independent patterning mechanisms may be used by other organisms during development.
A Neostriatal Habit Learning System in Humans
Authors: Knowlton Barbara J. , Mangels Jennifer A. , Squire Larry R.
Published: October 2006

Amnesic patients and nondemented patients with Parkinson's disease were given a probabilistic classification task in which they learned which of two outcomes would occur on each trial, given the particular combination of cues that appeared. Amnesic patients exhibited normal learning of the task but had severely impaired declarative memory for the training episode. In contrast, patients with Parkinson's disease failed to learn the probabilistic classification task, despite having intact memory for the training episode. This double dissociation shows that the limbic-diencephalic regions damaged in amnesia and the neostriatum damaged in Parkinson's disease support separate and parallel learning systems. In humans, the neostriatum (caudate nucleus and putamen) is essential for the gradual, incremental learning of associations that is characteristic of habit learning. The neostriatum is important not just for motor behavior and motor learning but also for acquiring nonmotor dispositions and tendencies that depend on new associations.
A Requirement for Local Protein Synthesis in Neurotrophin-Induced Hippocampal Synaptic Plasticity
Authors: Kang Hyejin , Schuman Erin M.
Published: October 2006

Two neurotrophic factors, brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3), are able to produce a long-lasting enhancement of synaptic transmission in the hippocampus. Unlike other forms of plasticity, neurotrophin-induced plasticity exhibited an immediate requirement for protein synthesis. Plasticity in rat hippocampal slices in which the synaptic neuropil was isolated from the principal cell bodies also required early protein synthesis. Thus, the neurotrophins may stimulate the synthesis of proteins in either axonal or dendritic compartments, allowing synapses to exert local control over the complement of proteins expressed at individual synaptic sites.
Similarity of a Chromatic Adaptation Sensor to Phytochrome and Ethylene Receptors
Authors: Kehoe David M. , Grossman Arthur R.
Published: October 2006

Complementary chromatic adaptation in cyanobacteria acts through photoreceptors to control the biosynthesis of light-harvesting complexes. The mutant FdBk, which appears black, cannot chromatically adapt and may contain a lesion in the apparatus that senses light quality. The complementing gene identified here,
rcaE
, encodes a deduced protein in which the amino-terminal region resembles the chromophore attachment domain of phytochrome photoreceptors and regions of plant ethylene receptors; the carboxyl-terminal half is similar to the histidine kinase domain of two-component sensor kinases.
Ecologists Look at the Big Picture
Authors: Moffat Anne Simon
Published: October 2006

Scientists have been trying to estimate Earth's carrying capacity—how many humans the planet can support—since Malthus's time. But in recent years, estimates have ranged from as low as 1.5 billion to as high as 1 trillion people. At the recent ecology meetings, speakers suggested that the way to resolve these disparate numbers is to incorporate highly quantitative analyses of social and economic factors, because humans can boost carrying capacity by choosing to consume less.
Superconductivity in Spin Ladders
Authors: Maekawa S.
Published: October 2006

Materials called spin ladder compounds have been synthesized as a way to test models of superconductivity.
Dynamics of the Simplest Chlorine Atom Reaction: An Experimental and Theoretical Study
Authors: Alagia M. , Balucani N. , Cartechini L. , Casavecchia P. , van Kleef E. H. , Volpi G. G. , Aoiz F. J. , Bañares L. , Schwenke D. W. , Allison T. C. , Mielke S. L. , Truhlar D. G.
Published: October 2006

Angular distributions and time-of-flight spectra for the reaction Cl + H
2
→ HCl + H obtained from a high-resolution, crossed-molecular beam experiment were compared to differential cross sections calculated by both converged quantum mechanical scattering and quasi-classical trajectory methods. Good agreement was found between the experimental results and each theoretical prediction. The results demonstrate that excellent agreement can be obtained between state-of-the-art simulations and experiments for the detailed dynamical properties of this prototype chlorine atom reaction.
Iridium in Natural Waters
Authors: Anbar A. D. , Wasserburg G. J. , Papanastassiou D. A. , Andersson P. S.
Published: October 2006

Iridium, commonly used as a tracer of extraterrestrial material, was measured in rivers, oceans, and an estuarine environment. The concentration of iridium in the oceans ranges from 3.0 (±1.3) × 10
8
to 5.7 (±0.8) × 10
8
atoms per kilogram. Rivers contain from 17.4 (±0.9) × 10
8
to 92.9 (±2.2) × 10
8
atoms per kilogram and supply more dissolved iridium to the oceans than do extraterrestrial sources. In the Baltic Sea, ∼75% of riverine iridium is removed from solution. Iron-manganese oxyhydroxides scavenge iridium under oxidizing conditions, but anoxic environments are not a major sink for iridium. The ocean residence time of iridium is between 2 × 10
3
and 2 × 10
4
years.
A Protein Phosphorylation Switch at the Conserved Allosteric Site in GP
Authors: Lin Kai , Rath Virginia L. , Dai Shirleko C. , Fletterick Robert J. , Hwang Peter K.
Published: October 2006

A phosphorylation-initiated mechanism of local protein refolding activates yeast glycogen phosphorylase (GP). Refolding of the phosphorylated amino-terminus was shown to create a hydrophobic cluster that wedges into the subunit interface of the enzyme to trigger activation. The phosphorylated threonine is buried in the allosteric site. The mechanism implicates glucose 6-phosphate, the allosteric inhibitor, in facilitating dephosphorylation by dislodging the buried covalent phosphate through binding competition. Thus, protein phosphorylation-dephosphorylation may also be controlled through regulation of the accessibility of the phosphorylation site to kinases and phosphatases. In mammalian glycogen phosphorylase, phosphorylation occurs at a distinct locus. The corresponding allosteric site binds a ligand activator, adenosine monophosphate, which triggers activation by a mechanism analogous to that of phosphorylation in the yeast enzyme.
Regulation of Integrin Function by the Urokinase Receptor
Authors: Wei Ying , Lukashev Matvey , Simon Daniel I. , Bodary Sarah C. , Rosenberg Steven , Doyle Michael V. , Chapman Harold A.
Published: October 2006

Integrin function is central to inflammation, immunity, and tumor progression. The urokinase-type plasminogen activator receptor (uPAR) and integrins formed stable complexes that both inhibited native integrin adhesive function and promoted adhesion to vitronectin via a ligand binding site on uPAR. Interaction of soluble uPAR with the active conformer of integrins mimicked the inhibitory effects of membrane uPAR. Both uPAR-mediated adhesion and altered integrin function were blocked by a peptide that bound to uPAR and disrupted complexes. These data provide a paradigm for regulation of integrins in which a nonintegrin membrane receptor interacts with and modifies the function of activated integrins.
Regulation of a Neuronal Form of Focal Adhesion Kinase by Anandamide
Authors: Derkinderen Pascal , Toutant Madeleine , Burgaya Ferran , Le Bert Marc , Siciliano Julio C. , de Franciscis Vittorio , Gelman Michèle , Girault Jean-Antoine
Published: October 2006

Anandamide is an endogenous ligand for central cannabinoid receptors and is released after neuronal depolarization. Anandamide increased protein tyrosine phosphorylation in rat hippocampal slices and neurons in culture. The action of anandamide resulted from the inhibition of adenylyl cyclase and cyclic adenosine 3′,5′-monophosphate-dependent protein kinase. One of the proteins phosphorylated in response to anandamide was an isoform of pp125-focal adhesion kinase (FAK+) expressed preferentially in neurons. Focal adhesion kinase is a tyrosine kinase involved in the interactions between the integrins and actin-based cytoskeleton. Thus, anandamide may exert neurotrophic effects and play a role in synaptic plasticity.
Biofilms Invade Microbiology
Authors: Potera Carol
Published: October 2006

After focusing on free-floating bacteria for decades, microbiologists are now realizing that in nature, bacteria often aggregate in biofilms—clumps of microbes surrounded by slime and stuck to a surface. Biofilms foul pipes, contaminate medical implants, and sometimes even kill humans, for these tough microbial communities can resist antibiotics and the immune system.
Highly Diverged U4 and U6 Small Nuclear RNAs Required for Splicing Rare AT-AC Introns
Authors: Tarn Woan-Yuh , Steitz Joan A.
Published: October 2006

Removal of a rare class of metazoan precursor messenger RNA introns with AU-AC at their termini is catalyzed by a spliceosome that contains U11, U12, and U5 small nuclear ribonucleoproteins. Two previously unidentified, low-abundance human small nuclear RNAs (snRNAs), U4atac and U6atac, were characterized as associated with the AT-AC spliceosome and necessary for AT-AC intron splicing. The excision of AT-AC introns therefore requires four snRNAs not found in the major spliceosome. With the use of psoralen crosslinking, a U6atac interaction with U12 was identified that is similar to a U6-U2 helix believed to contribute to the spliceosomal active center. The conservation of only limited U6atac sequences in the neighborhood of this interaction and the potential of U6atac to base pair with the 5′ splice site consensus for AT-AC introns provide support for current models of the core of the spliceosome.