bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Influence of Ligand Valency on Aggregation Mechanisms for Inhibiting Bacterial Toxins
Authors: Sisu Cristina , Baron Andrew J. , Branderhorst Hilbert M. , Connell Simon D. , Weijers Carel A. G. M. , de Vries Renko , Hayes Edward D. , Pukin Aliaksei V. , Gilbert Michel , Pieters Roland J. , Zuilhof Han , Visser Gerben M. , Turnbull W. Bruce 
Published: November 2008

AbstractDivalent and tetravalent analogues of ganglioside GM1 are potent inhibitors of cholera toxin and Escherichia coli heat‐labile toxin. However, they show little increase in inherent affinity when compared to the corresponding monovalent carbohydrate ligand. Analytical ultracentrifugation and dynamic light scattering have been used to demonstrate that the multivalent inhibitors induce protein aggregation and the formation of space‐filling networks. This aggregation process appears to arise when using ligands that do not match the valency of the protein receptor. While it is generally accepted that multivalency is an effective strategy for increasing the activity of inhibitors, here we show that the valency of the inhibitor also has a dramatic effect on the kinetics of aggregation and the stability of intermediate protein complexes. Structural studies employing atomic force microscopy have revealed that a divalent inhibitor induces head‐to‐head dimerization of the protein toxin en route to higher aggregates.
pH‐Controlled Molecular Switches and the Substrate‐Directed Self‐Assembly of Molecular Capsules with a Calix[4]pyrrole Derivative
Authors: Cafeo Grazia , Kohnke Franz H. , Valenti Luca , White Andrew J. P. 
Published: November 2008

Abstract10α,20α‐Bis(4‐nitrophenyl)calix[4]pyrrole (1) forms 1:1 complexes with anions of selected aromatic hydroxy acids in which the host orientation within the guest is controlled by a change in the pH value. Some bis‐anionic guests, including those obtained from 4‐hydroxybenzoic acid, 1,4‐ and 1,3‐benzenedicarboxylic acids, induce the self‐assembly of molecular capsules involving two molecules of the receptor. 1H NMR data and solid‐state structures of the 1:1 complex of 1 with p‐C6H4(COOH)(COO−)+NMe4 and the 2:1 capsule [(1)2m‐C6H4(COO−)2(+NMe4)2] provide structural details in solution and in the solid state.
Excitatory‐inhibitory relationship in the fascia dentata in the Ts65Dn mouse model of down syndrome
Authors: Belichenko Pavel V. , Kleschevnikov Alexander M. , Masliah Eliezer , Wu Chengbiao , Takimoto‐Kimura Ryoko , Salehi Ahmad , Mobley William C. 
Published: November 2008

AbstractDown syndrome (DS) is a neurological disorder causing impaired learning and memory. Partial trisomy 16 mice (Ts65Dn) are a genetic model for DS. Previously, we demonstrated widespread alterations of pre‐ and postsynaptic elements and physiological abnormalities in Ts65Dn mice. The average diameter of presynaptic boutons and spines in the neocortex and hippocampus was enlarged. Failed induction of long‐term potentiation (LTP) due to excessive inhibition was observed. In this paper we investigate the morphological substrate for excessive inhibition in Ts65Dn. We used electron microscopy (EM) to characterize synapses, confocal microscopy to analyze colocalization of the general marker for synaptic vesicle protein with specific protein markers for inhibitory and excitatory synapses, and densitometry to characterize the distribution of the receptor and several proteins essential for synaptic clustering of neurotransmitter receptors. EM analysis of synapses in the Ts65Dn vs. 2N showed that synaptic opposition lengths were significantly greater for symmetric synapses (∼18%), but not for asymmetric ones. Overall, a significant increase in colocalization coefficients of glutamic acid decarboxylase (GAD)65/p38 immunoreactivity (IR) (∼27%) and vesicular GABA transporter (VGAT)/p38 IR (∼41%) was found, but not in vesicular glutamate transporter 1 (VGLUT1)/p38 IR. A significant overall decrease of IR in the hippocampus of Ts65Dn mice compared with 2N mice for glutamate receptor 2 (GluR2; ∼13%) and anti‐γ‐aminobutyric acid (GABA)A receptor β2/3 subunit (∼20%) was also found. The study of proteins essential for synaptic clustering of receptors revealed a significant increase in puncta size for neuroligin 2 (∼13%) and GABAA receptor‐associated protein (GABARAP; ∼13%), but not for neuroligin 1 and gephyrin. The results demonstrate a significant alteration of inhibitory synapses in the fascia dentata of Ts65Dn mice. J. Comp. Neurol. 512:453–466, 2009. © 2008 Wiley‐Liss, Inc.
Structural Changes in 2‐Diarylthiophene‐Substituted Starburst Compounds upon Charging: A Theoretical and Spectroelectrochemical Study
Authors: Šolc Roland , Lukeš Vladimír , Rapta Peter , Hartmann Horst , Dunsch Lothar 
Published: November 2008

AbstractThe role of charging in structural changes of 2‐diarylaminothiophene‐substituted starburst compounds is clarified by combining theoretical and spectroelectrochemical studies. A systematic and comparative theoretical calculation based on density functional theory and semiempirical Austin Model 1 (AM1) calculations is performed on the neutral and charged states of four model tris(5‐diarylamino‐5‐thienyl)‐terminated starburst compounds with a central triphenylamine and 1,3,5‐triphenylbenzene moiety. Our results indicate that the charging of molecules leads to structural changes by quinoid‐type components mostly on the dendrimers terminated by phenothiazinyl fragments. Based on the optimal geometries, the spectroscopic properties were calculated using the semiempirical Zerner’s intermediate neglect overlap method. The presented theoretical results and the spin electron distributions of charged states and their spectra are supported by the spectroelectrochemical observations caused by the different electron localization within the studied molecules after charging. The satisfactory agreement between theoretical electronic transitions and experimental values indicates that a rational design of tunable molecular layers in organic devices based on the starburst compounds described is possible.
Elastic constant measurements of super ionic LiKSO4:Na single crystals
Authors: Varughese G. , Kumar A. Santhosh , Philip J. , Louis G. 
Published: November 2008

AbstractElastic properties of sodium doped Lithium potassium sulphate, Li K0.9 Na 0.1 SO4, crystal has been studied by ultrasonic Pulse Echo Overlap [PEO] technique and are reported for the first time. The controversy regarding the type of crystal found while growth is performed at 35 °C with equimolar fraction of Li2SO4H2O, K2SO4 and Na2SO4 has been resolved by studying the elastic properties. The importance of this crystal is that it exhibits pyroelectric, ferroelectric and electro optic properties. It is simultaneously ferroelastic and superionic. The elastic properties of LiK0.9Na0.1SO4 crystal are well studied by measuring ultrasonic velocity in the crystal in certain specified crystallographic directions and evaluating the elastic stiffness constants, compliance constants and Poisson's ratios. The anisotropy in the elastic properties of the crystal are well explained by the pictorial representation of the surface plots of phase velocity, slowness and linear compressibility in a‐b and a‐c planes. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Structural and optical investigations on Mn doped Li2B4O7 crystals
Authors: Kar S. , Verma S. , Bartwal K. S. 
Published: November 2008

AbstractLithium tetraborate crystals have great demand due to its non‐critical phase matching at 90°. Transparent and good optical quality single crystals of undoped and Mn doped Li2B4O7 were grown by Czochralski technique in air atmosphere. The crystalline phase was determined by X‐ray diffraction. Doping of Mn in the grown crystals was confirmed by energy dispersive analysis of X‐rays (EDAX) technique. Transmission spectra show that the crystal is transparent in the visible region. Birefringence interferograms were recorded to qualitatively analyse the optical homogeneity of the grown crystals and to quantify the birefringence of the samples in desired crystal direction. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Practical and Benign Synthesis of Primary Amines through Ruthenium‐Catalyzed Reduction of Nitriles
Authors: Enthaler Stephan , Junge Kathrin , Addis Daniele , Erre Giulia , Beller Matthias 
Published: November 2008

AbstractThe catalytic hydrogenation of nitriles represents an atom‐economic and valuable route to amines. In the present study, the ruthenium‐catalyzed hydrogenation of various organic nitriles to give primary amines has been examined in detail. Straightforward ruthenium complexes modified by cheap and widely available triphenylphosphine allow for the efficient and general reduction of various aryl, alkyl, and heterocyclic nitriles. By using a practical in situ catalyst composed of [Ru(cod)(methylallyl2)] and PPh3, excellent yields and chemoselectivity were achieved. Moreover, the catalyst system displays broad functional group tolerance.
Acceleration of Suzuki–Miyaura‐ and Stille‐type Coupling Reactions by Irradiation with Near‐UV‐A Light
Authors: Imperato Giovanni , König Burkhard 
Published: November 2008

AbstractIrradiation of a palladium catalyst bearing UV‐A‐absorbing phosphine ligands with low‐intensity UV‐A light leads to higher conversions of reactants at lower temperatures and an increased selectivity towards the cross‐coupling product in Suzuki–Miyaura‐ and Stille‐type reactions. The examples studied illustrate that a selective energy input into the catalyst by irradiation leads to more selective conversions under milder reaction conditions. With the availability of affordable and energy‐efficient UV‐A LED light sources, selective heating of the catalyst by light can be envisaged as a general strategy to increase the performance of a catalyst.
Gaussian pulse approximation using standard CMOS and its application for sub‐GHz UWB impulse radio
Authors: Zhang Xiaodong , Elgamel Mohamed , Bayoumi Magdy A. 
Published: November 2008

AbstractGaussian pulse is widely used in communication systems. The true Gaussian function is not physically realizable, but it can be approximated through linear functions. This paper presents a Gaussian pulse approximation approach to generate a quasi‐Gaussian pulse by using the transient response of a CMOS inverter. The basic structure of the proposed design includes a digital variable square pulse generator, a Gaussian pulse generator and a small antenna model. The digital variable square pulse generator makes the amplitude and width of the generated quasi‐Gaussian pulse tunable. The proposed pulse generator works well for three different electrical small antenna models. The simulation results show that the generated pulse approximates the Gaussian shape very well and the radiated signal at the antennas is compliant with the Federal Communication Commission's spectral mask for the 0–960 MHz band. The simple structure of this Gaussian pulse generator lends itself to a low‐power, single‐chip UWB transceiver solution. Copyright © 2008 John Wiley & Sons, Ltd.
A new affordable flow cytometry based method to measure HIV‐1 viral load
Authors: Greve Burkhard , Weidner Jürgen , Cassens Uwe , Odaibo Georgina , Olaleye David , Sibrowski Walter , Reichelt Doris , Nasdala Ines , Göhde Wolfgang 
Published: November 2008

AbstractMost commercially available assays for diagnosis of HIV infection have shown shortcomings in the detection and quantification of rare genotypes of the virus. Most of the assays do not detect subtype O (outlier) and/or N (nonmajor, nonoutlier) or new circulating recombinant forms (CRFs), which are becoming more important in sub‐Saharan Africa. Furthermore, the commonly available tests require costly measuring devices and expensive test kits, which are not easily affordable for developing countries. This study was designed to explore solutions to the problem of viral load assays in developing countries. Two forward primers, digoxygenin (DIG) and dinitrophenol (DNP) labeled, and one biotin (BIO) labeled reverse primer were used to amplify both, the HIV‐1‐5′LTR (long terminal repeat) region and an internal standard sequence. The two polymerase chain reaction (PCR)‐products were captured by anti‐DIG and anti‐DNP antibody coated microparticles. Flow cytometric analyses were carried out after labeling with streptavidin‐R‐phycoerythrine. The primer system used recognized all HIV‐1 subtypes. A coamplified internal standard warranted the functionality of the PCR and allows reproducible viral load measurements. Two drawbacks of current viral load measurements are overcome by the flow cytometry based test described hereof. First, all known worldwide relevant HIV‐1 subtypes including subtypes O, N, and new CRFs are quantifiable with high sensitivity (50 to >1 × 106 copies per PCR). Second, the cost per test can be reduced to less than 12 US$ instead of the current 50–100 US$. Additionally, the test described in this report offers the possibility to perform complete monitoring program (CD4 T‐cell count, CD4% and viral load) for the first time, with the same device for HIV‐infected persons. © 2008 International Society for Advancement of Cytometry
Quantitative measurement of multifunctional quantum dot binding to cellular targets using flow cytometry
Authors: Smith R. A. , Giorgio T. D. 
Published: November 2008

AbstractSemiconductor nanocrystals such as quantum dots (QDs) are a potentially powerful resource in the fields of flow cytometry and fluorescence microscopy. QD size and fluorescence characteristics offer attractive features for use in targeted delivery systems and detection by flow cytometry. While quantitative measurements of a variety of fluorescent molecules are routinely performed, fluorophores for which no calibration standards exist, such as QDs, pose a problem for quantitation in flow cytometry. Our goal was to develop a targeted nanoparticle delivery platform as well as a corresponding method to accurately and quantitatively assess the performance of this system. We synthesized surface‐modified QD probes targeted to cellular surface receptors and measured the MFI of the resulting cell‐probe conjugates by flow cytometry. MFI was converted to mean equivalent R‐PE intensity (MEPE) using standard calibration microspheres. Known concentrations of both R‐PE and QD probes were measured by fluorometry to relate R‐PE and QD fluorescence. Fluorometry results were then used to translate MEPE measurements to the number of bound QD probes. The targeted probes exhibited superior binding characteristics over unmodified and untargeted particles. This binding interaction was shown to be specific and mediated by the NGR targeting peptide tethered to the QD surface. The calibration method developed to assess this system proved successful at converting raw fluorescence data to quantitative probe binding values. We demonstrate the synthesis and performance of a highly modular nanoparticle system capable of targeted binding and fluorescent imaging. The calibration method implemented to quantify the performance of this system represents a potentially powerful tool to utilize truly quantitative flow cytometry measurements with an array of fluorescent molecules, including QDs. © 2008 International Society for Advancement of Cytometry
The development and evolution of left‐right asymmetry in invertebrates: Lessons from Drosophila and snails
Authors: Okumura Takashi , Utsuno Hiroki , Kuroda Junpei , Gittenberger Edmund , Asami Takahiro , Matsuno Kenji 
Published: November 2008

AbstractThe unique nature of body handedness, which is distinct from the anteroposterior and dorsoventral polarities, has been attracting growing interest in diverse biological disciplines. Recent research progress on the left‐right asymmetry of animal development has focused new attention on the mechanisms underlying the development and evolution of invertebrate handedness. This exploratory review of currently available information illuminates the prospective value of Drosophila and pulmonate snails for innovative new research aimed at elucidating these mechanisms. For example, findings in Drosophila and snails suggest that an actin filament–dependent mechanism may be evolutionarily conserved in protostomes. The polarity conservation of primary asymmetry across most metazoan phyla, which visceral handedness represents, indicates developmental constraint and purifying selection as possible but unexplored mechanisms. Comparative studies using Drosophila and snails, which have the great advantages of using genetic and evolutionary approaches, will accelerate our understanding of the mechanisms governing the conservation and diversity of animal handedness. Developmental Dynamics 237:3497–3515, 2008. © 2008 Wiley‐Liss, Inc.
pMesogenin1 and 2 function directly downstream of Xtbx6 in Xenopus somitogenesis and myogenesis
Authors: Tazumi Shunsuke , Yabe Shigeharu , Yokoyama Jun , Aihara Yuko , Uchiyama Hideho 
Published: November 2008

AbstractT‐box transcription factor tbx6 and basic‐helix‐loop‐helix transcription factor pMesogenin1 are reported to be involved in paraxial mesodermal differentiation. To clarify the relationship between these genes in Xenopus laevis, we isolated pMesogenin2, which showed high homology with pMesogenin1. Both pMesogenin1 and 2 appeared to be transcriptional activators and were induced by a hormone‐inducible version of Xtbx6 without secondary protein synthesis in animal cap assays. The pMesogenin2 promoter contained three potential T‐box binding sites with which Xtbx6 protein was shown to interact, and a reporter gene construct containing these sites was activated by Xtbx6. Xtbx6 knockdown reduced pMesogenin1 and 2 expressions, but not vice versa. Xtbx6 and pMesogenin1 and 2 knockdowns caused similar phenotypic abnormalities including somite malformation and ventral body wall muscle hypoplasia, suggesting that Xtbx6 is a direct regulator of pMesogenin1 and 2, which are both involved in somitogenesis and myogenesis including that of body wall muscle in Xenopus laevis. Developmental Dynamics 237:3749–3761, 2008. © 2008 Wiley‐Liss, Inc.
Retinoid regulation of the zebrafish cyp26a1 promoter
Authors: Hu Ping , Tian Miao , Bao Jie , Xing Guangdong , Gu Xingxing , Gao Xiang , Linney Elwood , Zhao Qingshun 
Published: November 2008

AbstractCyp26A1 is a major enzyme that controls retinoic acid (RA) homeostasis by metabolizing RA into bio‐inactive metabolites. Previous research revealed that the mouse Cyp26A1 promoter has two canonical RA response elements (RAREs) that underlie the regulation of the gene by RA. Analyzing the 2,533‐base pairs (2.5 k) genomic sequence upstream of zebrafish cyp26a1 start codon, we report that the two RAREs are conserved in zebrafish cyp26a1 promoter. Mutagenesis demonstrated that the two RAREs work synergistically in RA inducibility of cyp26a1. Fusing the 2.5 k (kilobase pairs) fragment to the enhanced yellow fluorescent protein (eYFP) reporter gene, we have generated two transgenic lines of zebrafish [Tg(cyp26a1:eYFP)]. The transgenic zebrafish display expression patterns similar to that of cyp26a1 gene in vivo. Consistent with the in vitro results, the reporter activity is RA inducible in embryos. Taken together, our results demonstrate that the 2.5 k fragment underlies the regulation of the zebrafish cyp26a1 gene by RA. Developmental Dynamics 237:3798–3808, 2008. © 2008 Wiley‐Liss, Inc.
Integrin alpha chains exhibit distinct temporal and spatial localization patterns in epithelial cells of the Drosophila ovary
Authors: Dinkins Michael B. , Fratto Victoria M. , LeMosy Ellen K. 
Published: November 2008

AbstractIntegrins are heterodimeric transmembrane receptors that modulate cell adhesion, migration, and signaling. Multiple integrin chains contribute to development and morphogenesis of a given tissue. Here, we analyze the expression of Drosophila integrin alpha chains in the ovarian follicular epithelium, a model for tissue morphogenesis and cell migration. We find expression throughout development of the beta chain, βPS. Alpha chains, however, exhibit both spatial and temporal expression differences. αPS1 and αPS2 integrins are detected during early and mid‐oogenesis on apical, lateral, and basal membranes with the βPS chain, whereas αPS3‐family integrins (αPS3, αPS4, αPS5) are expressed in anterior cells late in oogenesis. Surprisingly, we find that αPS3‐family integrins are dispensable for dorsal appendage morphogenesis but play a role in the final length of the egg, suggesting redundant functions of integrins in a simple tissue. We also demonstrate roles for αPS3βPS integrin in border cell migration and in stretch cells. Developmental Dynamics 237:3927–3939, 2008. © 2008 Wiley‐Liss, Inc.
Identification of nucleus pulposus precursor cells and notochordal remnants in the mouse: Implications for disk degeneration and chordoma formation
Authors: Choi Kyung‐Suk , Cohn Martin J. , Harfe Brian D. 
Published: November 2008

AbstractA classically identified “notochordal” cell population in the nucleus pulposus is thought to regulate disk homeostasis. However, the embryonic origin of these cells has been under dispute for >60 years. Here we provide the first direct evidence that all cell types in the adult mouse nucleus pulposus are derived from the embryonic notochord. Additionally, rare isolated embryonic notochord cells remained in the vertebral column and resembled “notochordal remnants,” which in humans have been proposed to give rise to a rare type of late‐onset cancer called chordoma. Previously, this cell type had not been identified in the mouse model system. The development and characterization of a mouse model that can be used to fate map nucleus pulposus precursor cells in any mutant background will be useful for uncovering the cellular and molecular mechanisms of disk degeneration. In addition, the identification of notochordal remnants in mice is the first step towards generating an in vivo model of chordoma. Developmental Dynamics 237:3953–3958, 2008. © 2008 Wiley‐Liss, Inc.
Isolation and expression analysis of Alzheimer's disease–related gene xb51 in zebrafish
Authors: Kim Hyun‐Taek , Kim Eun‐Hye , Yoo Kyeong‐Won , Lee Mi‐Sun , Choi Jung‐Hwa , Park Hae‐Chul , Yeo Sang‐Yeob , Lee Dong‐Seok , Kim Cheol‐Hee 
Published: November 2008

AbstractXB51 protein is known to interact with the amino‐terminal of the X11L protein and to be involved in Aβ40 generation, a hallmark of Alzheimer's disease. In this study, we isolated a zebrafish xb51 homologue and analyzed its spatio‐temporal expression pattern during early brain development. The xb51 transcript was first detected in the forebrain at 22 hr post‐fertilization. Expression of xb51 in the brain persisted by 36 hpf and became more complex in the brain after 48 hpf. The detailed expression domain of xb51 in the dorsal telencephalon was defined by several molecular markers: emx1, dlx2, lim1, islet1, neurod4/zath3, ngn1, her4, and elavl3/huC. The location of xb51‐expressing cells was restricted in a subset of cells positive for elavl3/huC and acetylated alpha‐tubulin, markers of differentiating and/or differentiated neurons. Together, these results suggest that xb51 may be required for maturation and maintenance of xb51‐expressing neurons in the forebrain. Developmental Dynamics 237:3921–3926, 2008. © 2008 Wiley‐Liss, Inc.