bluuebunny/crossref_metadata_2025 huggingface dataset:
Interferon-γ Induced Medulloblastoma in the Developing Cerebellum
Authors: Lin Wensheng , Kemper April , McCarthy Ken D. , Pytel Peter , Wang Jian-Ping , Campbell Iain L. , Utset Manuel F. , Popko Brian
Published: November 2004

We have generated a mouse model system with a high incidence of medulloblastoma, a malignant neoplasm believed to arise from immature precursors of cerebellar granule neurons. These animals ectopically express interferon-γ (IFN-γ) in astrocytes in the CNS in a controlled manner, exploiting the tetracycline-controllable system. More than 80% of these mice display severe ataxia and develop cerebellar tumors that express synaptophysin, the mouse atonal homolog MATH1, sonic hedgehog (SHH), and Gli1. IFN-γ-induced tumorigenesis in these mice is associated with increased expression of SHH, and SHH induction and tumorigenesis are dependent on signal transducer and activator of transcription 1 (STAT1). When IFN-γ expression is shut down with doxycycline at postnatal day 12 (P12), the clinical symptoms dissipate and the mice do not develop tumors, whereas if transgene expression is shut down at P16, the clinical symptoms and tumors progress to lethality, indicating that IFN-γ is required for tumor induction but not progression. The tumors that occur in the continued presence of IFN-γ display extensive necrosis and apoptosis as well as macrophage and lymphocytic infiltration, whereas the tumors that develop in mice in which IFN-γ expression is shut down at P16 do not. Thus, IFN-γ expression in the perinatal period can induce SHH expression and medulloblastoma in the cerebellum by a STAT1-dependent mechanism, and its continued presence appears to promote a host response to the tumor.
The Brain-Derived Neurotrophic Factor val66met Polymorphism and Variation in Human Cortical Morphology
Authors: Pezawas Lukas , Verchinski Beth A. , Mattay Venkata S. , Callicott Joseph H. , Kolachana Bhaskar S. , Straub Richard E. , Egan Michael F. , Meyer-Lindenberg Andreas , Weinberger Daniel R.
Published: November 2004

A variation in theBDNFgene (val66met) affects the function of BDNF in neurons, predicts variation in human memory, and is associated with several neurological and psychiatric disorders. Here, we show that, in magnetic resonance imaging scans of a large sample of normal individuals, this polymorphism affects the anatomy of the hippocampus and prefrontal cortex, identifying a genetic mechanism of variation in brain morphology related to learning and memory.
Organ of Corti Potentials and the Motion of the Basilar Membrane
Authors: Fridberger Anders , de Monvel Jacques Boutet , Zheng Jiefu , Hu Ning , Zou Yuan , Ren Tianying , Nuttall Alfred
Published: November 2004

During sound stimulation, receptor potentials are generated within the sensory hair cells of the cochlea. Prevailing theory states that outer hair cells use the potential-sensitive motor protein prestin to convert receptor potentials into fast alterations of cellular length or stiffness that boost hearing sensitivity almost 1000-fold. However, receptor potentials are attenuated by the filter formed by the capacitance and resistance of the membrane of the cell. This attenuation would limit cellular motility at high stimulus frequencies, rendering the above scheme ineffective. Therefore, Dallos and Evans (1995a) proposed that extracellular potential changes within the organ of Corti could drive cellular motor proteins. These extracellular potentials are not filtered by the membrane. To test this theory, both electric potentials inside the organ of Corti and basilar membrane vibration were measured in response to acoustic stimulation. Vibrations were measured at sites very close to those interrogated by the recording electrode using laser interferometry. Close comparison of the measured electrical and mechanical tuning curves and time waveforms and their phase relationships revealed that those extracellular potentials indeed could drive outer hair cell motors. However, to achieve the sharp frequency tuning that characterizes the basilar membrane, additional mechanical processing must occur inside the organ of Corti.
Axonal Regeneration and Lack of Astrocytic Gliosis in EphA4-Deficient Mice
Authors: Goldshmit Yona , Galea Mary P. , Wise Graham , Bartlett Perry F. , Turnley Ann M.
Published: November 2004

Spinal cord injury usually results in permanent paralysis because of lack of regrowth of damaged neurons. Here we demonstrate that adult mice lacking EphA4 (-/-), a molecule essential for correct guidance of spinal cord axons during development, exhibit axonal regeneration and functional recovery after spinal cord hemisection. Anterograde and retrograde tracing showed that axons from multiple pathways, including corticospinal and rubrospinal tracts, crossed the lesion site. EphA4-/- mice recovered stride length, the ability to walk on and climb a grid, and the ability to grasp with the affected hindpaw within 1-3 months of injury. EphA4 expression was upregulated on astrocytes at the lesion site in wild-type mice, whereas astrocytic gliosis and the glial scar were greatly reduced in lesioned EphA4-/- spinal cords. EphA4-/- astrocytes failed to respond to the inflammatory cytokines, interferon-γ or leukemia inhibitory factor,in vitro. Neurons grown on wild-type astrocytes extended shorter neurites than on EphA4-/- astrocytes, but longer neurites when the astrocyte EphA4 was blocked by monomeric EphrinA5-Fc. Thus, EphA4 regulates two important features of spinal cord injury, axonal inhibition, and astrocytic gliosis.
Assessing the Role of GLUK5and GLUK6at Hippocampal Mossy Fiber Synapses
Authors: Breustedt Jörg , Schmitz Dietmar
Published: November 2004

It has been suggested recently that presynaptic kainate receptors (KARs) are involved in short-term and long-term synaptic plasticity at hippocampal mossy fiber synapses. Using genetic deletion and pharmacology, we here assess the role of GLUK5and GLUK6in synaptic plasticity at hippocampal mossy fiber synapses. We found that the kainate-induced facilitation was completely abolished in theGLUK6-/-mice, whereas it was unaffected in theGLUK5-/-. Consistent with this finding, synaptic facilitation was reduced in theGLUK6-/-and was normal in theGLUK5-/-. In agreement with these results and ruling out any compensatory effects in the genetic deletion models, application of the GLUK5-specific antagonistLY382884[(3S,4aR,6S,8aR)-6-(4-carboxyphenyl)methyl-1,2,3,4,4a,5,6,7,8,8a-decahydroisoquinoline-3-carboxylic acid] did not affect short-term and long-term synaptic plasticity at the hippocampal mossy fiber synapses. We therefore conclude that the facilitatory effects of kainate on mossy fiber synaptic transmission are mediated by GLUK6-containing KARs.
Postsynaptic Density Protein-95 Regulates NMDA Channel Gating and Surface Expression
Authors: Lin Ying , Skeberdis V. Arvydas , Francesconi Anna , Bennett Michael V. L. , Zukin R. Suzanne
Published: November 2004

NMDA receptors (NMDARs) colocalize with postsynaptic density protein-95 (PSD-95), a multivalent synaptic scaffolding protein and core component of the postsynaptic density, at excitatory synapses. Although much is known about the identity and properties of scaffolding proteins, little is known about their actions on NMDAR function. Here we show that association of PSD-95 with NMDARs modulates channel gating and surface expression. PSD-95 increases the number of functional channels at the cell surface and channel opening rate of NMDARs, with little or no change in conductance, reversal potential, or mean open time. We show further that PSD-95 increases NMDAR surface expression by increasing the rate of channel insertion and decreasing the rate of channel internalization. The PDZ (PSD-95, discs large, zona occludens-1) binding motif at the distal end of the NR2 C-terminal tail is critical to the actions of PSD-95 on NMDAR function and surface expression. Given that activity bi-directionally modifies synaptic levels of PSD-95, our findings suggest a novel mechanism for activity-dependent regulation of NMDARs at central synapses.
Acid-Sensing Ion Channel 2 Contributes a Major Component to Acid-Evoked Excitatory Responses in Spiral Ganglion Neurons and Plays a Role in Noise Susceptibility of Mice
Authors: Peng Ben-Gang , Ahmad Shoab , Chen Shanping , Chen Ping , Price Margaret P. , Lin Xi
Published: November 2004

Ion channels in the degenerin-epithelial sodium channel (DEG-ENaC) family perform diverse functions, including mechanosensation. Here we explored the role of the vertebrate DEG-ENaC protein, acid-sensing ion channel 2 (ASIC2), in auditory transduction. Contributions of ASIC2 to hearing were examined by comparing hearing threshold and noise sensitivity of wild-type and ASIC2 null mice. ASIC2 null mice showed no significant hearing loss, indicating that the ASIC2 was not directly involved in the mechanotransduction of the mammalian cochlea. However, we found that (1) ASIC2 was present in the spiral ganglion (SG) neurons in the adult cochlea and that externally applied protons induced amiloride-sensitive sodium currents and action potentials in SG neuronsin vitro, (2) proton-induced responses were greatly reduced in SG neurons obtained from ASIC2 null mice, indicating that activations of ASIC2 contributed a major portion of the proton-induced excitatory response in SG neurons, and (3) ASIC2 null mice were considerably more resistant to noise-induced temporary, but not permanent, threshold shifts. Together, these data suggest that ASIC2 contributes to suprathreshold functions of the cochlea. The presence of ASIC2 in SG neurons could provide sensors to directly convert local acidosis to excitatory responses, therefore offering a cellular mechanism linking hearing losses caused by many enigmatic causes (e.g., ischemia or inflammation of the inner ear) to excitotoxicity.
Cortical Areas Involved in Object, Background, and Object-Background Processing Revealed with Functional Magnetic Resonance Adaptation
Authors: Goh Joshua O. S. , Siong Soon Chun , Park Denise , Gutchess Angela , Hebrank Andy , Chee Michael W. L.
Published: November 2004

Previous work has suggested that object and place processing are neuroanatomically dissociated in ventral visual areas under conditions of passive viewing. It has also been shown that the hippocampus and parahippocampal gyrus mediate the integration of objects with background scenes in functional imaging studies, but only when encoding or retrieval processes have been directed toward the relevant stimuli. Using functional magnetic resonance adaptation, we demonstrated that object, background scene, and contextual integration of selectively repeated objects and background scenes could be dissociated during the passive viewing of naturalistic pictures involving object-scene pairings. Specifically, bilateral fusiform areas showed adaptation to object repetition, regardless of whether the associated scene was novel or repeated, suggesting sensitivity to object processing. Bilateral parahippocampal regions showed adaptation to background scene repetition, regardless of whether the focal object was novel or repeated, suggesting selectivity for background scene processing. Finally, bilateral parahippocampal regions distinct from those involved in scene processing and the right hippocampus showed adaptation only when the unique pairing of object with background scene was repeated, suggesting that these regions perform binding operations.
Plasticity of the Avian Song Control System in Response to Localized Environmental Cues in an Equatorial Songbird
Authors: Moore Ignacio T. , Wingfield John C. , Brenowitz Eliot A.
Published: November 2004

A striking feature of the vertebrate brain is its plasticity. In high-latitude vertebrates, seasonal plasticity of the brain is driven by ubiquitous photoperiod cues and therefore is highly predictable and synchronous across extensive geographic ranges. A pronounced example of seasonal brain plasticity occurs in the nuclei that regulate song behavior in songbirds. These nuclei are larger in breeding than in nonbreeding birds. In the tropics, photoperiod varies little annually, and other environmental cues important for breeding can show considerable local geographic variability. We investigated whether localized patterns of seasonal breeding in tropical birds are associated with brain plasticity. We studied two populations of rufous-collared sparrows (Zonotrichia capensis) that breed, only 25 km apart, on the equator but out of phase with each other. We measured gonadal activity and the size of song nuclei (high vocal center, robust nucleus of the arcopallium, and area X) during each population's breeding and nonbreeding periods. Breeding males had larger song nuclei and greater gonadal activity than did nonbreeding birds. This plasticity was associated with local environmental cues, such that the two populations exhibit asynchronous changes in brain structure. These results demonstrate the sensitivity of the brain and its ability to use a variety of environmental cues to coordinate seasonal plasticity and reproduction.
"Creating Dissonance for the Visitor": The Heart of the Liberty Bell Controversy
Authors: Ogline Jill
Published: November 2004

This paper examines the controversy surrounding the location and proposed interpretive plan for Independence National Historical Park's new pavilion for the Liberty Bell. Written from the perspective of a graduate student and former Independence NHP employee, it attempts to help historians and Park Service employees to better understand each other's positions, and to penetrate to the heart of the issue at stake—the park's own sense of self-understanding and mission. It then moves on to show the relevance of this specific controversy to questions of broader significance, such as the fundamental character of American history, the post–September 11th responsibility of historic sites, the strength of national mythology, and the vital importance of critical public history.
Pictures vs. Words? Public History, Tolerance, and the Challenge of Jacob Riis
Authors: O'Donnell Edward T.
Published: November 2004

Through his pioneering use of photography and muckraking prose (most especially in How the Other Half Lives, 1890), Jacob Riis earned fame as a humanitarian in the classic Progressive Era mold. Yet in recent years some revisionist scholars have denounced Riis as an unreconstructed racist who merely posed as a benevolent reformer. Does this rethinking of Riis and the character of his work mean that public historians who have come to revere his photographs should shun them when producing public history related to themes of ethnicity, immigration, multiculturalism, and tolerance? The author argues against this conclusion for two reasons. First, a careful analysis of Riis's entire career and body of written work reveals a man who, despite his lapses into the language of racist stereotypes, was fundamentally tolerant to a degree that far surpassed his contemporaries. Second, the bold use of Riis's words and photos provides the public historian with an extraordinary opportunity to delve into the complex questions of assimilation and Americanization, labor exploitation, cultural diversity, social control, and middle-class fear that lie at the heart of the American immigration narrative.
Coupled diffusion and adsorption effects for multiple proteins in agarose gel
Authors: Gutenwik Jan , Nilsson Bernt , Axelsson Anders
Published: November 2004

A mathematical model for the hindered diffusion and competitive adsorption of two proteins in an agarose gel has been developed. In a simulation program the model has been used to study the competing and displacement effects on a single bead for lysozyme and bovine serum albumin (BSA) bound to the ligand Cibacron Blue in agarose gel. The model takes into account hindered diffusion described by the Renkin model, competitive Langmuir adsorption kinetics, pore size distribution of the gel, and a shrinking effective pore radius attributed to molecule‐to‐ligand binding. The simulation model can easily explain displacement of BSA or lysozyme dependent on the binding capacity, kinetics, and diffusion. The influence of a bimodal pore size distribution is demonstrated. It also provides insight into the phenomenon of static vs. dynamic binding capacity observed in experimental determinations of the isotherm. © 2004 American Institute of Chemical Engineers AIChE J, 50: 3006–3018, 2004
Characterization of a gas‐liquid OBC: Bubble size and gas holdup
Authors: Oliveira Mónica S. N. , Ni Xiong‐Wei
Published: November 2004

A fundamental experimental study of gas‐liquid contacting in an oscillatory baffled column is presented focusing on the effect of fluid oscillation on gas holdup and bubble size. The results show that beyond a critical level of fluid oscillation the Sauter mean diameter of the dispersion is substantially reduced, while the gas holdup (and, thus, the residence time of the gas phase) increases significantly. The reduction of bubble size was described in terms of bubble breakage, caused by the interaction of the bubbles with eddies. The experimental results were modeled by applying Kolmogoroff's theory of isotropic turbulence. The steep increase in the gas holdup with oscillation was mainly due to bubble entrainment by large vortices, formed by the oscillatory flow in the presence of baffles. A semi‐theoretical expression, based on the forces acting on a bubble, was proposed, and was able to accurately match the experimental trends. The results also show that the gas‐liquid hydrodynamics are mainly governed by the oscillatory operating conditions, and independent of the type of gas sparger. © 2004 American Institute of Chemical Engineers AIChE J, 50: 3019–3033, 2004
Fast and reliable sexing of prosimian and human DNA
Authors: Fredsted T. , Villessen P.
Published: November 2004

Molecular sexing of mammals is normally done by PCR amplification of Y chromosomal fragments, or coamplification of homologous fragments from both sex chromosomes. Existing primers are often unreliable for distantly related species due to mutations in primer regions. Currently there are no published primers for the sexing of prosimian DNA. We show that an existing method (using the zinc finger protein) based on a size difference between the X and Y homologs does not work in prosimians. Multiple alignments of distantly related mammalian species from Genbank and genome databases enabled us to identify conserved regions in the amelogenin gene. Using these conserved regions, we can target species that have no sequence information. We designed a single, conserved primer pair that is useful for fast and reliable molecular sexing of prosimian primates. A single PCR yields two fragments in males and only one in females, which are easily separated with the use of agarose gels. Amplification of separable fragments was successful in seven species of lemurs, as well as humans. Am. J. Primatol. 64:345–350, 2004. © 2004 Wiley‐Liss, Inc.
Agonistic behavior and dominance relationships in female phayre's leaf monkeys – preliminary results
Authors: Koenig Andreas , Larney Eileen , Lu Amy , Borries Carola
Published: November 2004

Socioecological theory suggests a link between the strength of competition for food/safety, rates of agonism, structure of dominance hierarchies, and dispersal among group‐living females. This study presents preliminary data on agonistic behavior and dominance relationships for female Phayre's leaf monkeys (Trachypithecus phayrei), a species in which females routinely disperse. Behavioral observations were conducted on two groups (four adult females, and five adult females plus two juvenile females, respectively) at Phu Khieo Wildlife Sanctuary, northeast Thailand. Rates of agonistic behavior were analyzed from focal continuous recordings, while dominance hierarchies were constructed from all agonistic behaviors (focal and ad libitum sampling). Overall, female–female agonistic behaviors (aggression, submission, and displacements) occurred at a rate of <0.25 interactions per hour. Agonistic interactions involving food occurred more frequently than expected based on feeding time. Females in both groups exhibited linear dominance hierarchies with some reversals, and possibly an age‐inversed hierarchical structure in the larger group. The results fit well with previous results for colobine monkeys regarding frequency of interactions, displacements predominating agonistic behavior, and the possibility of an age‐inversed hierarchy. The results contradict the suggested link between linearity of hierarchies and female philopatry. Future studies should consider the notion that female dispersal may coexist with linear dominance hierarchies. Am. J. Primatol. 64:351–357, 2004. © 2004 Wiley‐Liss, Inc.
DNA‐Codes für die Nanowissenschaften
Authors: Samorì Bruno , Zuccheri Giampaolo
Published: November 2004

Der Nanometerbereich ist ein ganz spezieller Ort – treffen sich hier doch alle naturwissenschaftlichen Disziplinen. Die Nanowissenschaften ziehen ihre Ideen aus der Biologie, und Aufgabe der Chemie ist es, diese Ideen in nanotechnologische Anwendungen umzusetzen. Das biologische Molekül, das Nanowissenschaften und Nanotechnik gegenwärtig am meisten fasziniert, ist die DNA. Die Natur nutzt die DNA nicht nur als “Ablage” für die genetische Information, sondern auch als Steuerungseinheit für die Expression der darin enthaltenen Gene. So enthält die DNA‐Sequenz bestimmte Codes, die atomare Erkennungsprozesse wie etwa die Basenpaarung steuern, und andere, die Prozesse im Nanometerbereich kontrollieren. Aus chemischer Sicht ist die DNA die supramolekulare Baueinheit mit dem größten bekannten Informationsgehalt. Für die Nanowissenschaften ergibt sich daraus die Möglichkeit, mit DNA‐Molekülen das Komplexitätsniveau und die Effizienz bei Selbstorganisations‐ und Selbstausrichtungsprozessen zu steigern.
Integrated Nanoparticle–Biomolecule Hybrid Systems: Synthesis, Properties, and Applications
Authors: Katz Eugenii , Willner Itamar
Published: November 2004

Nanomaterials, such as metal or semiconductor nanoparticles and nanorods, exhibit similar dimensions to those of biomolecules, such as proteins (enzymes, antigens, antibodies) or DNA. The integration of nanoparticles, which exhibit unique electronic, photonic, and catalytic properties, with biomaterials, which display unique recognition, catalytic, and inhibition properties, yields novel hybrid nanobiomaterials of synergetic properties and functions. This review describes recent advances in the synthesis of biomolecule–nanoparticle/nanorod hybrid systems and the application of such assemblies in the generation of 2D and 3D ordered structures in solutions and on surfaces. Particular emphasis is directed to the use of biomolecule–nanoparticle (metallic or semiconductive) assemblies for bioanalytical applications and for the fabrication of bioelectronic devices.
New and highly efficient method for silkworm transgenesis using Autographa californica nucleopolyhedrovirus and piggyBac transposable elements
Authors: Yamamoto Masafumi , Yamao Masafumi , Nishiyama Hiroshi , Sugihara Shinya , Nagaoka Sumiharu , Tomita Masahiro , Yoshizato Katsutoshi , Tamura Toshiki , Mori Hajime
Published: November 2004

We have developed a new method for the transgenesis of the silkworm, Bombyx mori. This method couples the use of recombinant baculoviruses with the use of the piggyBac transposable element. One recombinant AcNPV, designated the helper virus, is designed to express the piggyBac transposase under the control of the Drosophila hsp70 promoter. Another recombinant AcNPV encoded the gene to be incorporated into the silkworm genome, in this case a green fluorescent protein (GFP) gene, under the control of B. mori actin A3 promoter and franked by the piggyBac inverted terminal repeats. Preblastoderm eggs were inoculated with a fine needle coated with a mixture of these two recombinant baculoviruses. Most of the inoculated larvae hatched and a high proportion of the newly hatched G0 larvae expressed the GFP marker. Transgenesis was confirmed by Southern blot analysis of G1 insects, sequencing the insertion site junctions isolated by inverse PCR, and the marker segregated in Mendelian fashion, as evidenced by the appearance of green fluorescence in G2 insects. Thus, transgenic silkworms were easily and efficiently obtained using this new method. © 2004 Wiley Periodicals, Inc.
Synthesis and Characterization of Nanocast Silica NCS‐1 with CMK‐3 as a Template
Authors: Lu An‐Hui , Schmidt Wolfgang , Spliethoff Bernd , Schüth Ferdi
Published: November 2004

Nanocast silica (NCS‐1) was synthesized by a casting process by employing the mesoporous carbon CMK‐3 (the replica of SBA‐15) as a template, tetraethoxysilane (TEOS) as the silica source, and hydrochloric acid (HCl) as the catalyst. The ordered carbon template was removed by employing different methods, such as calcination, thermal treatment followed by calcination, and controlled combustion. According to XRD and TEM characterization, NCS‐1 exhibits an ordered structure with hexagonal symmetry and retains the morphology of the original SBA‐15 used for the synthesis of CMK‐3 over two replication steps on the nanometer scale. This demonstrates the well‐connected porosity in CMK‐3 type carbon, which can be used as a mold to synthesize mesostructured materials. The nitrogen adsorption isotherms generally show type IV shape, indicating mesoporous characteristics. The structure of NCS‐1 is strongly influenced by variables of the nanocasting process, such as the loading amount of silica, hydrolysis temperature, and carbon removal methods. The surface area, pore size, and pore volume of NCS‐1 can be tuned to a certain range by varying these parameters.
Synthesis, Spectroscopy, and Electrochemistry of Tetra‐tert‐butylated Tetraazaporphyrins, Phthalocyanines, Naphthalocyanines, and Anthracocyanines, together with Molecular Orbital Calculations
Authors: Kobayashi Nagao , Nakajima Shin‐ichiro , Ogata Hiroshi , Fukuda Takamitsu
Published: November 2004

Tetraazaporphyrins (TAPs), phthalocyanines (Pcs), naphthalocyanines (Ncs), and anthracocyanines (Acs) with four tert‐butyl groups attached at similar positions have been synthesized, and their electronic absorption, magnetic circular dichroism (MCD), IR, and voltammetric properties were studied and interpreted with the help of quantum‐mechanical calculations. Through the preparation of a series of compounds with the same number of the same substituent, the effects of the increase in the size of the ring system were clearly derived. The main results may be summarized as follows. 1) The Q band shifts to longer wavelength and its intensity increases, but with decreasing degree of change with increasing molecular size. If the size of the effect of benzene directly fused to the TAP skeleton is set at unity, the effects of the second and third benzene units are roughly 0.8 and 0.5, respectively. 2) The splitting of the Q bands in metal‐free compounds decreases with increasing molecular size, so that the Q bands of H2Nc and H2Ac appear as single bands. 3) The magnitude of the orbital angular momentum of the excited state of the ligand decreases with increasing molecular size. 4) Interestingly, the ring current, as judged from the positions of pyrrole proton signals in the 1H NMR spectrum, appears to decrease with increasing molecular size. 5) The first reduction potential becomes less negative, but only slightly, whereas the first oxidation potential shows a marked shift to less positive values with increasing molecular size, indicating that the HOMO destabilizes significantly as the molecule becomes larger. 6) In 5), the extent of the HOMO destabilization with molecular size differs depending on the central metal, so metals producing smaller destabilization effects can allow larger macrocycles. Of the metals studied, the most effective is cobalt, and the practical size limit is represented by the Acs. 7) The IR spectra become simpler the larger the molecule, and the main bands were assigned by DFT calculations. 8) The trend in experimentally determined redox potentials and electronic absorption and MCD spectra were reasonably reproduced by MO calculations using the ZINDO/S Hamiltonian. 9) EPR data for several metallocomplexes are also reported.
cis/trans Photoisomerization of Secondary Thiopeptide Bonds
Authors: Zhao Jianzhang , Micheau Jean‐Claude , Vargas Carolyn , Schiene‐Fischer Cordelia
Published: November 2004

The reversible cis/trans photoisomerization of secondary thiopeptide bonds has been systematically studied with UV‐visible absorption, capillary electrophoresis, 1H NMR spectroscopy, and circular dichroism methods. It was found that the concentration of the cis conformers could be increased from less than 1 % in the thermal equilibrated solution to up to 20 % in the photostationary state. The rotational barriers of the thiopeptide bond and the pH dependence of the isomerization rates were also studied. The quantum yields of the trans→cis and the cis→trans processes were determined from photokinetic analysis.
Mass Spectrometric Investigation of Noncovalent Complexation between a Tetratosylated Resorcarene and Alkyl Ammonium Ions
Authors: Ventola Elina , Rissanen Kari , Vainiotalo Pirjo
Published: November 2004

Noncovalent complexation between tetratosylated tetraethyl resorcarene (1) and primary, secondary, and tertiary alkyl ammonium ions (mMe, dMe, tMe, mEt, dEt, tEt, dBu, and dHex) was studied by electrospray ionization Fourier transform ion cyclotron resonance (ESI‐FTICR) mass spectrometry. Interactions of the noncovalent complexes were investigated by means of competition experiments, collision‐induced dissociation (CID) experiments, ion–molecule reactions with tripropylamine and gas phase H/D‐exchange reactions with deuteroammonia. Gas phase ion–molecule reactions gave especially valuable information about the structure and properties of the complexes. Resorcarene 1 formed relatively stable 1:1 complexes with all aliphatic alkyl ammonium ions. Steric properties of the alkyl ammonium ions and proton affinities of the conjugate amines noticeably affected the complexation properties, indicating the importance of hydrogen bonding in these complexes. According to the competition experiments, the thermodynamically most stable host–guest complexes were formed with alkyl ammonium ions that were most substituted and had the longest alkyl chains. In CID experiments, release of an intact free guest ion or dissociation of the host was observed to depend on the proton affinity of the amine and the strength of the hydrogen bond that was formed. In ion–molecule reactions with tripropylamine, a guest exchange reaction occurred with all alkyl ammonium ion complexes with reaction rates mostly dependent on the steric properties of the original guest ion. In H/D‐exchange reactions the N‐H hydrogen atoms of the guest ion were exchanged with deuterium, whereas the resorcinol hydrogen atoms remained unchanged.
Solvent‐Ligated Manganese(II) Complexes for the Homopolymerization of Isobutene and the Copolymerization of Isobutene and Isoprene
Authors: Vierle Mario , Zhang Yanmei , Santos Ana M. , Köhler Klaus , Haeßner Carmen , Herdtweck Eberhardt , Bohnenpoll Martin , Nuyken Oskar , Kühn Fritz E.
Published: November 2004

Polyisobutenes with a high content of terminal olefinic groups can be synthesized by using manganese(II) initiators in homogeneous solution. These easily accessible complexes initiate the polymerization at room temperature and above, and afford highly reactive, gel‐free polyisobutenes with high viscosities. Furthermore, the initiators were successfully used for the copolymerization of isobutene with isoprene. The high activities of the MnIIinitiators seem to be related to their weakly coordinating nitrile ligands, which are easily displaced by substrate molecules. Replacing the nitrile ligands by other more strongly coordinating ligands such as water reduces the initiator activity significantly. The MnIIinitiators are surprisingly resistant to temperature.
Atmospheric Pressure Chemical Vapor Deposition: An Alternative Route to Large‐Scale MoS2 and WS2 Inorganic Fullerene‐like Nanostructures and Nanoflowers
Authors: Li Xiao‐Lin , Ge Jian‐Ping , Li Ya‐Dong
Published: November 2004

Large‐scale MoS2 and WS2 inorganic fullerene‐like (IF) nanostructures (onionlike nanoparticles, nanotubes) and elegant three‐dimensional nanoflowers (NF) have been selectively prepared through an atmospheric pressure chemical vapor deposition (APCVD) process with the reaction of chlorides and sulfur. The morphologies were controlled by adjusting the deposition position, the deposition temperature, and the flux of the carrier gas. All of the nanostructures have been characterized by X‐ray powder diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). A reaction mechanism is proposed based on the experimental results. The surface area of MoS2 IF nanoparticles and the field‐emission effect of as‐prepared WS2 nanoflowers is reported.
Palladium‐Catalyzed Intramolecular Oxidative Alkylation of 4‐Pentenyl β‐Dicarbonyl Compounds
Authors: Liu Cong , Wang Xiang , Pei Tao , Widenhoefer Ross A.
Published: November 2004

Reaction of 8‐nonene‐2,4‐dione with a catalytic amount of [PdCl2(CH3CN)2] (2; 5 mol %) and a stoichiometric amount of CuCl2 (2.5 equiv) at room temperature for 3 h led to oxidative alkylation and formation of 2‐acetyl‐3‐methyl‐2‐cyclohexenone in 80 % isolated yield. The oxidative alkylation of 4‐pentenyl β‐diketones tolerated a number of terminal acyl groups and substitution at the C1 and C3 carbon atoms of the 4‐pentenyl chain. Likewise, 4‐pentenyl β‐keto esters that possessed geminal disubstitution at the C1, C2, or C3 carbon atom of the 4‐pentenyl chain cyclized to form 2‐carboalkoxy‐2‐cyclohexenones in moderate to good yield as the exclusive cyclized product. Deuterium‐labeling experiments provided information regarding the mechanism of the palladium‐catalyzed oxidative alkylation of 4‐pentenyl β‐dicarbonyl compounds.
Synthesis of Benzannulated N‐Heterocyclic Carbene Ligands by a Template Synthesis from 2‐Nitrophenyl Isocyanide
Authors: Hahn F. Ekkehardt , García Plumed César , Münder Marco , Lügger Thomas
Published: November 2004

The reaction of 2‐nitrophenyl isocyanide 2 with [M(CO)5(thf)] (M=Cr, Mo, W) yields the isocyanide complexes [M(CO)5(2)] (3: M=Cr; 4: M=Mo; 5: M=W). Complexes 3–5 react with elemental tin under reduction of the nitro function of the isocyanide ligand to give the complexes with the unstable 2‐aminophenyl isocyanide ligand. The coordinated 2‐aminophenyl isocyanide ligand in all three complexes reacts spontaneously under intramolecular nucleophilic attack of the primary amine at the isocyanide carbon atom to yield the complexes with the NH,NH‐benzimidazol‐2‐ylidene ligand (6: M=Cr; 7: M=Mo; 8: M=W). An incomplete reduction of the nitro group in 3–5 is observed when hydrazine hydrate is used instead of tin. Here the formation of complexes with a coordinated 2‐hydroxylamine‐functionalized phenyl isocyanide [(CO)5M‐CN‐C6H4‐‐2‐N(H)‐OH] is postulated and this unstable ligand again undergoes intramolecular cyclization to give the NH,NOH‐stabilized benzimidazol‐2‐ylidene complexes 9–11. The tungsten derivative 11 can be allylated stepwise by a deprotonation/alkylation sequence first at the OH and then at the NH position to yield the monoallylated and diallylated species 12 and 13. The molecular structures of 3–5 and 12–13 were established by X‐ray crystallography.
A Remarkable Ligand Orientational Effect in Osmium‐Atom‐Induced Blue Phosphorescence
Authors: Yu Jen‐Kan , Hu Ya‐Hui , Cheng Yi‐Ming , Chou Pi‐Tai , Peng Shie‐Ming , Lee Gene‐Hsiang , Carty Arthur J. , Tung Yung‐Liang , Lee Shin‐Wun , Chi Yun , Liu Chao‐Shiuan
Published: November 2004

A new series of OsII‐based carbonyl complexes cis(CO),trans(Npy,Npy),cis(Ntz,Ntz)‐[Os(CO)2(bptz)2] (1), cis(CO),cis(Npy,Npy),trans(Ntz,Ntz)‐[Os(bptz)2(CO)2] (2), and cis(CO),trans(Npy,Npy),cis(Ntz,Ntz)‐[Os(CO)2(fptz)2] (3), where bptz and fptz denote 3‐tert‐butyl‐5‐(2‐pyridyl)‐ and 3‐trifluoromethyl‐5‐(2‐pyridyl)‐1,2,4‐triazolate, respectively, have been designed and synthesized in an effort to achieve high efficiency, room‐temperature blue phosphorescence. Although 1 and 2 are geometric isomers, remarkably different excited‐state relaxation pathways were observed. Complex 1 exhibits strong phosphorescence in CH3CN (Φp∼0.47) and as a single crystal at room temperature, whereas complex 2 is nearly nonemissive under similar conditions. The associated relaxation dynamics have been comprehensively investigated by spectroscopic and relaxation dynamics as well as by theoretical approaches. Our results lead us to the conclusion that for complex 2, the “loose bolt” effect of metal–ligand bonding interactions plays a crucial role in the fast radiationless deactivation of this type of geometrical isomer. Fine adjustment can also be achieved by functionalizing the ligands so that the electron‐withdrawing nature of the CF3 group in 3 stabilizes the HOMO of the triazolate moiety, thus moving the emission further into the pure “blue” region; this results in highly efficient phosphorescence and renders 3 particularly attractive for application in blue OLED devices.
Complete Charge Pooling is Prevented in Viologen‐Based Dendrimers by Self‐Protection
Authors: Marchioni Filippo , Venturi Margherita , Ceroni Paola , Balzani Vincenzo , Belohradsky Martin , Elizarov Arkadij M. , Tseng Hsian‐Rong , Stoddart J. Fraser
Published: November 2004

We have investigated the electrochemical behavior, and chemical and photosensitized reduction of two dendrimers based on a 1,3,5‐trisubstituted benzenoid core, which contain 9 and 21 4,4′‐bipyridinium (usually called viologen) units, respectively, in their branches and are terminated with tetraarylmethane groups. For comparison purposes, the behavior of reference compounds that contain a single viologen unit have also been investigated. We have found that only part of the viologen units can be reduced in the dendrimer species. For the larger dendrimer, the number of reducible viologens (out of the 21 present) is 14 in electrochemical experiments (in MeCN), 9 on reduction with bis(benzene)chromium (in MeCN), and 13 by photoinduced electron transfer with 9‐methylanthracene as a photosensitizer and triethanolamine as a sacrificial reductant in CH2Cl2. The reduced viologen units undergo partial dimerization. The photochemical experiments have shown that only monomeric, one‐electron‐reduced viologen units are formed at the beginning of the irradiation, followed by dimer formation, until a photostationary state is reached that contains 40 % nonreduced, 33 % monomeric reduced, and 27 % reduced units associated in the dimeric form. The results suggest that, upon reduction of a fraction of the viologen units, the dendrimer structure shrinks, with the result that the bulky terminal groups protect other viologen units from being reduced.
Synthesis of Branched Oxime‐Linked Peptide Mimetics of the MUC1 Containing a Universal T‐Helper Epitope
Authors: Cremer Gaëlle‐Anne , Bureaud Nicole , Lelièvre Dominique , Piller Véronique , Piller Friedrich , Delmas Agnès
Published: November 2004

Our goal was to develop mimics of MUC1, highly immunogenic to induce an efficient immune response against the tumor‐associated form of MUC1, and sufficiently different from the natural antigen to bypass the tolerance barrier in humans. With the aim of obtaining a well‐defined peptide construct as a means of evoking the precise immune responses required in immunotherapy, we synthesized artificial mimics of the MUC1 protein composed of two MUC1 repeat units of inverse orientation and a universal T‐helper epitope. To synthesize these heteromeric peptide constructs, we followed a convergent approach using chemoselective ligation based on oxime chemistry. A stem peptide was first synthesized bearing two orthogonally masked aldehydes. After successive deprotection, two oxime bonds can be specifically generated. The proposed strategy proved to be concise and robust, and allowed the synthesis of the tri‐branched protein in a very satisfactory yield. The different constructs were tested for their ability to generate antibodies able to recognize the MUC1 protein.
Sugar–Poly(para‐phenylene ethynylene) Conjugates as Sensory Materials: Efficient Quenching by Hg2+ and Pb2+ Ions
Authors: Kim Ik‐Bum , Erdogan Belma , Wilson James N. , Bunz Uwe H. F.
Published: November 2004

Three polar poly(para‐phenylene ethynylene)s (PPE) were synthesized by utilizing the Heck–Sonogashira protocol. Two of the PPEs carry β‐glucopyranose substituents. Depending upon the linker used between the glycol units and the backbone, the fluorescence of these PPEs can be quenched by Hg2+ and Pb2+ to a varying degree. Monomeric model compounds that are substituted with only one glucose unit are not efficiently quenched. The presence of many glucose substituents in one PPE assembly led to a large increase in the binding constant to Hg2+ and quenching of the fluorescence was amplified.
Distant echoes of the accordion: Reduced dimensionality, GFT‐NMR, and projection‐reconstruction of multidimensional spectra
Authors: Freeman Ray , Kupče Eriks
Published: November 2004

Multidimensional NMR spectroscopy can be speeded up appreciably by techniques that reduce the number of evolution periods examined independently. This review charts the evolution of the “reduced dimensionality” concept starting with the accordion experiment, and showing how it gradually developed into GFT‐NMR and projection‐reconstruction (PR‐NMR), which collects plane projections at different orientations and uses them to reconstruct the full multidimensional spectrum. While the data‐gathering stages of GFT‐NMR and PR‐NMR are similar, the processing stages are radically different. The methods described here are generally applicable to the standard multidimensional NMR sequences, and they offer comparable sensitivity and resolution, and a similar advantage in speed. By adopting a method related to the inverse Radon transform, PR‐NMR can also be applied to situations of only marginal sensitivity. © 2004 Wiley Periodicals, Inc. Concepts Magn Reson 23A: 63–75, 2004.
NMR studies of surfactants
Authors: Söderman Olle , Stilbs Peter , Price William S.
Published: November 2004

Surfactant molecules are amphipathic and posses complicated solution chemistry and self‐assembly properties. In addition to being of enormous practical significance, the physical characterization of surfactant systems presents a rich area of condensed matter physics. This article focuses on the application and interpretation of the commonly used NMR approaches for probing these systems. In particular, the use of NMR relaxation, diffusometry and, more briefly, electrophoretic NMR to determine characteristics such as micellar size and structure, ion‐binding and solubilization are considered. The application of these NMR techniques is illustrated by a number of pertinent examples. © 2004 Wiley Periodicals, Inc. Concepts Magn Reson 23A:, 121–135, 2004.
NMR methods for studying membrane‐active antimicrobial peptides
Authors: Strandberg Erik , Ulrich Anne S.
Published: November 2004

NMR is a versatile tool for studying interactions between antimicrobial peptides and lipid membranes. Different approaches using both liquid state and solid state NMR are outlined here, with an emphasis on solid state NMR methods, to study the structures of antimicrobial peptides in lipid bilayers as well as the effect of these peptides on model membranes. Different NMR techniques for observing both peptides and lipids are explained, including 2H, 13C, 15N, and 19F labels, or natural abundance 1H, 13C, or 31P. Previous studies in the field are extensively reviewed in easily accessible tables. © 2004 Wiley Periodicals, Inc. Concepts Magn Reson 23A: 89–120, 2004.
Human ovarian carcinoma cells: Histone deacetylase inhibitors exhibit antiproliferative activity and potently induce apoptosis
Authors: Takai Noriyuki , Kawamata Norihiko , Gui Dorina , Said Jonathan W. , Miyakawa Isao , Koeffler H. Phillip
Published: November 2004

BACKGROUND

Histone deacetylase inhibitors (HDACIs) can inhibit proliferation, stimulate apoptosis, and induce cell cycle arrest in malignant cells.

METHODS

The authors investigated the effects of four HDACIs on nine ovarian carcinoma cell lines in vitro and in vivo. Ovarian carcinoma cells were treated with a variety of HDACIs, and their effects on cell growth, the cell cycle, apoptosis, and related events were investigated. The ability of valproic acid (VPA) to inhibit the growth of ovarian tumors in immunodeficient mice was also assessed.

RESULTS

Clonogenic assays showed that all ovarian carcinoma cell lines were sensitive to the growth‐inhibitory effects of the HDACIs. Cell cycle analysis indicated that their exposure to HDACIs decreased the proportion of cells in S phase and increased the proportion of cells in the G0/G1 and/or G2/M phases of the cell cycle. Terminal deoxynucleotidyltransferase‐mediated uridine triphosphate end‐labeling assays demonstrated that HDACIs induced apoptosis, which occurred in concert with alterations in the expression of genes related to apoptosis, cell growth, and malignant phenotype, including the activation of caspase‐9 and caspase‐3. Chromatin immunoprecipitation analysis revealed a notable increase in levels of acetylated histones associated with the p21 promoter after treatment with suberoylanilide bishydroxamine. In addition, in experiments involving nude mice, VPA significantly inhibited human ovarian tumor growth without toxic side effects.

CONCLUSIONS

The results of the current study suggest that HDACIs may be particularly effective in the treatment of ovarian tumors. Cancer 2004. © 2004 American Cancer Society.
Rhabdomyosarcoma: Value of myogenin expression analysis and molecular testing in diagnosing the alveolar subtype
Authors: Hostein Isabelle , Andraud‐Fregeville Marie , Guillou Louis , Terrier‐Lacombe Marie‐José , Deminière Colette , Ranchère Dominique , Lussan Catherine , Longavenne Elisabeth , Bui Nguyen Binh , Delattre Olivier , Coindre Jean‐Michel
Published: November 2004

BACKGROUND

Identification of the alveolar subtype of rhabdomyosarcoma (ARMS) is important, because the poor prognosis associated with this subtype necessitates a modified therapeutic regimen. At present, ARMS diagnoses are made on the basis of histologic findings and the extent of myogenin immunopositivity. Nonetheless, the absence of an alveolar pattern in the solid variant, the low degree of differentiation in certain embryonal rhabdomyosarcomas (ERMS), and the increasing use of microbiopsy samples make the diagnosis of ARMS somewhat difficult. Two specific translocations have been found in ARMS, and fusion transcripts can be detected by reverse transcriptase–polymerase chain reaction (RT‐PCR) analysis of paraffin‐embedded tissue (PET).

METHODS

To assess the value of myogenin staining and molecular testing in the diagnosis of rhabdomyosarcoma, the authors examined 109 rhabdomyosarcoma samples (45 ARMS samples and 64 ERMS samples). Real‐time RT‐PCR analysis of PET was performed in all 109 rhabdomyosarcomas, and RT‐PCR analysis of frozen material was performed in 24 cases.

RESULTS

PAX fusion transcripts were present in 44 cases (39 ARMS and 5 ERMS) and absent in 52 cases (2 ARMS and 50 ERMS). In 13 cases (4 ARMS and 9 ERMS), the results were not interpretable. Results were concordant between paired frozen and fixed tumor samples. All 35 interpretable ERMS samples that contained < 50% myogenin‐positive cells failed to yield detectable PAX fusion transcripts. Of the 61 interpretable tumor samples (41 ARMS and 20 ERMS) that contained > 50% myogenin‐positive cells, 44 (39 ARMS and 5 ERMS) yielded detectable PAX fusion transcripts.

CONCLUSIONS

The current study demonstrates that molecular detection of PAX fusion transcripts via real‐time RT‐PCR analysis of PET is a sensitive and specific method for the diagnosis of ARMS and that immunohistochemical analysis of myogenin expression can be used to select cases for such molecular testing. Although RT‐PCR analysis appears not to possess diagnostic value in tumors with < 50% tumor cell immunopositivity, it is strongly recommended for the diagnosis of tumors containing > 50% myogenin‐positive cells. Cancer 2004. © 2004 American Cancer Society.