bluuebunny/crossref_metadata_2025_split huggingface dataset:
Torsional Angular Dependence of 1J(Se,Se) and Fermi Contact Control of 4J(Se,Se): Analysis of nJ(Se,Se) (n=1–4) Based on Molecular Orbital Theory
Authors: Nakanishi Waro , Hayashi Satoko 
Published: April 2008

AbstractnJ(Se,Se) (n=1–4) nuclear couplings between Se atoms were analyzed by using molecular orbital (MO) theory as the first step to investigating the nature of bonded and nonbonded nJ(Se,Se) interactions between Se atoms. The values were calculated by employing Slater‐type triple ξ basis sets at the DFT level, which were applied to structures optimized with the Gaussian 03 program. The contribution from each occupied MO (ψi) and ψi→ψa (ψa=unoccupied MO) transition was evaluated separately. 1J(Se,Se) was calculated for the MeSeSeMe model compound, which showed a typical dependence on the torsion angle (ϕ(CMeSeSeCMe)). This dependence explains the small values (≤64 Hz) of 1Jobsd(Se,Se) observed for RSeSeR′ and large values (330–380 Hz) of 1Jobsd(Se,Se) observed for 4‐substituted naphtho[1,8‐c,d]‐1,2‐diselenoles, which correspond to synperiplanar diselenides. The HOMO→LUMO and HOMO−1→LUMO transitions contribute the most to 1J(Se,Se) at ϕ=0 and 180° to give large values of 1J(Se,Se), whereas various transitions contribute and cancel each other out at ϕ=90° to give small values of 1J(Se,Se). Large 4Jobsd(Se,Se) values were also observed in the nonbonded Se⋅⋅⋅Se, Se⋅⋅⋅SeO, and OSe⋅⋅⋅SeO interactions at naphthalene 1,8‐positions. The Fermi contact (FC) term contributes significantly to 4J(Se,Se), whereas the paramagnetic spin‐orbit (PSO) term contributes significantly to 1J(Se,Se). 2J(Se,Se) and 3J(Se,Se) were analyzed in a similar manner and a torsional angular dependence was confirmed for 3J(Se,Se). Depending on the structure, the main contribution to nJ(Se,Se) (n=2, 3) is from the FC term, with a lesser contribution from the PSO term. Analysis of each transition enabled us to identify and clearly visualize the origin and mechanism of the couplings.
Supramolecular Polymerization and Polymorphs of Oligo(p‐phenylene vinylene)‐Functionalized Bis‐ and Monoureas
Authors: Yagai Shiki , Kubota Shun , Iwashima Tomoyuki , Kishikawa Keiki , Nakanishi Takashi , Karatsu Takashi , Kitamura Akihide 
Published: April 2008

AbstractBis‐ and monoureas hybridized with the oligo(p‐phenylene vinylene) (OPV) π‐electronic segment and 3,4,5‐tridodecyloxyphenyl wedge were synthesized and their supramolecular polymerization in diluted solution, gel formation in concentrated solution, and liquid crystallinity in bulk state were investigated. Bisurea 1 a featuring a hexamethylene linker showed the highest supramolecular polymerization ability and formed tapelike nanofibers that can gelate various organic solvents. On the other hand, bisurea 1 b featuring a dodecamethylene linker and monourea 2 showed a lower degree of supramolecular polymerization, resulting in gel formations in a smaller variety of solvents. These results clearly reflect a high level of cooperativity between the two urea sites and the two OPV segments of 1 a upon hydrogen‐bonding and π–π stacking interactions, respectively. When the gels of 1 a, 1 b, and 2 were dried, all the compounds self‐organized into multilamellar superstructures. Thermal treatment of these lamellae at high temperatures induces columnar liquid‐crystalline mesophases as a result of microsegregation between the rigid OPV parts and the molten aliphatic wedges. These results demonstrate that the present molecular constituent is very useful for fabricating dye‐based functional assemblies providing nanoscale π‐electronic fibers, and solvent‐incorporated and bulk soft materials.
Experimental and Theoretical Approaches Toward Anion‐Responsive Tripod–Lanthanide Complexes: Mixed‐Donor Ligand Effects on Lanthanide Complexation and Luminescence Sensing Profiles
Authors: Kataoka Yumiko , Paul Dharam , Miyake Hiroyuki , Yaita Tsuyoshi , Miyoshi Eisaku , Mori Hirotoshi , Tsukamoto Shinya , Tatewaki Hiroshi , Shinoda Satoshi , Tsukube Hiroshi 
Published: April 2008

AbstractA new series of tripods were designed to form anion‐responsive, luminescent lanthanide complexes. These tripods contain pyridine, thiazole, pyrazine, or quinoline chromophores combined with amide carbonyl oxygen and tertiary nitrogen atoms. Crystallographic and EXAFS studies of the 10‐coordinated tripod–La(NO3)3 complexes revealed that each La3+ cation was cooperatively coordinated by one tetradentate tripod and three bidentate NO3− anions in the crystal and in CH3CN. Quantum chemical calculations indicated that the aromatic nitrogen plays a significant role in lanthanide complexation. The experimentally determined stability constants of complexes of the tripod with La(NO3)3, Eu(NO3)3, and Tb(NO3)3 were in good agreement with the theoretically calculated interaction energies. Complexation of each tripod with lanthanide triflate gave a mixture of several lanthanide complex species. Interestingly, the addition of a coordinative NO3− or Cl− anion to the mixture significantly influenced the lanthanide complexation profiles. The particular combination of tripod and a luminescent Eu3+ center gave anion‐selective luminescence enhancements. Pyridine‐containing tripods exhibited the highest NO3− anion‐selective luminescence and thus permit naked‐eye detection of the NO3− anion.
The Bound Conformation of Microtubule‐Stabilizing Agents: NMR Insights into the Bioactive 3D Structure of Discodermolide and Dictyostatin
Authors: Canales Angeles , Matesanz Ruth , Gardner Nicola M. , Andreu José Manuel , Paterson Ian , Díaz J. Fernando , Jiménez‐Barbero Jesús 
Published: April 2008

AbstractA protocol based on a combination of NMR experimental data with molecular mechanics calculations and docking procedures has been employed to determine the microtubule‐bound conformation of two microtubule‐stabilizing agents, discodermolide (DDM) and dictyostatin (DCT). The data indicate that tubulin in assembled microtubules recognizes DDM through a conformational selection process, with minor changes in the molecular skeleton between the major conformer in water solution and that bound to assembled microtubules. For DCT, the deduced bound geometry presents some key conformation differences around certain torsion angles, with respect to the major conformer in solution, and still displays mobility even when bound. The bound conformer of DCT resembles that of DDM and provides very similar contacts with the receptor. Competition experiments indicate that both molecules compete with the taxane‐binding site. A model of the binding mode of DDM and DCT to tubulin is proposed.
Supramolecular Bidentate Ligands by Metal‐Directed in situ Formation of Antiparallel β‐Sheet Structures and Application in Asymmetric Catalysis
Authors: Laungani Andy C. , Slattery John M. , Krossing Ingo , Breit Bernhard 
Published: April 2008

AbstractThe principles of protein structure design, molecular recognition, and supramolecular and combinatorial chemistry have been applied to develop a convergent metal‐ion‐assisted self‐assembly approach that is a very simple and effective method for the de novo design and the construction of topologically predetermined antiparallel β‐sheet structures and self‐assembled catalysts. A new concept of in situ generation of bidentate P‐ligands for transition‐metal catalysis, in which two complementary, monodentate, peptide‐based ligands are brought together by employing peptide secondary structure motif as constructing tool to direct the self‐assembly process, is achieved through formation of stable β‐sheet motifs and subsequent control of selectivity. The supramolecular structures were studied by 1H, 31P, and 13C NMR spectroscopy, ESI mass spectrometry, X‐ray structure ana1ysis, and theoretical calculations. Our initial catalysis results confirm the close relationship between the self‐assembled sheet conformations and the catalytic activity of these metallopeptides in the asymmetric rhodium‐catalyzed hydroformylation. Good catalyst activity and moderate enantioselectivity were observed for the selected combination of catalyst and substrate, but most importantly the concept of this new methodology was successfully proven. This work presents a perspective interface between protein design and supramolecular catalysis for the design of β‐sheet mimetics and screening of libraries of self‐organizing supramolecular catalysts.
Polyacrylamide gel plugs enabling 2‐D microfluidic protein separations via isoelectric focusing and multiplexed sodium dodecyl sulfate gel electrophoresis
Authors: Liu Jikun , Yang Shuang , Lee Cheng S. , DeVoe Don L. 
Published: April 2008

AbstractIn situ photopolymerized polyacrylamide (PAAm) gel plugs are used as hydrodynamic flow control elements in a multidimensional microfluidic system combining IEF and parallel SDS gel electrophoresis for protein separations. The PAAm gel plugs offer a simple method to reduce undesirable bulk flow and limit reagent/sample crosstalk without placing unwanted constraints on the selection of separation media, and without hindering electrokinetic ion migration in the complex microchannel network. In addition to improving separation reproducibility, the discrete gel plugs integrated into critical regions of the chip enable the use of a simple pressure‐driven sample injection method which avoids electrokinetic injection bias. The gel plugs also serve to greatly simplify operation of the spatially multiplexed system by eliminating the need for complex external fluidic interfaces. Using an FITC‐labeled Escherichia coli cell lysate as a model system, the use of gel plugs is shown to significantly enhance separation reproducibility in a chip containing five parallel CGE channels, with an average variance in peak elution time of only 4.1%.
Detection of PEGylated proteins in polyacrylamide gels by reverse staining with zinc and imidazole salts
Authors: Hardy Eugenio , Ramón José , Saez Vivian , Báez Reynier , Tejeda Yosbel , Ruiz Amalia 
Published: April 2008

AbstractThe reverse staining, with imidazole–SDS–zinc, of PEG‐linked proteins separated by SDS‐PAGE was studied. Using model conjugates (interferon‐α 2b (IFN‐α2b) reacted with either a branched‐chain (40 000) PEG (PEG2,40) or a linear monomethoxy PEG polymer (Mr of 12 000) and chromatographically purified monoPEG2,40‐IFN‐α2b), conventional small‐format analytical gels (<1 mm thick) showed typical detection patterns (i.e., transparent, colorless bands clearly discernible against a zinc imidazolate‐generated white gel background), in less than 20 min. Nonreacted (free) PEG was almost undetected, as expected. The reverse‐stained PEGylated IFN‐α2b patterns were qualitatively indistinguishable from those of parallel gels stained with iodine (I2). The LOD was estimated in the low nanogram range (e.g., at about 7 ng for mono‐ or bi‐PEG2,40 IFN‐α2b per lane on gradient (4–17%) gels). Also, this stain allowed the visualization of Coomassie blue‐undetected PEG‐IFN bands, and could be restained with I2. PEGylated species of lysozyme, a low‐molecular‐weight peptide, ovalbumin, and chymotrypsin were used to demonstrate the generality of this stain. We also show (i) how to counteract the adverse effect of some parameters (e.g., gel thickness above 1 mm, long gel length, low (e.g., 4–6%) acrylamide concentration) on the reverse staining process and (ii) that the properties of the reverse‐stained PEGylated proteins remain unchanged, as judged by analyzing both the ion exchange chromatography‐based positional isomer separation profile and enzyme‐linked immunosorbent response of PEG‐IFN recovered from gels. Consequently, this technique may be useful for the rapid analysis or the small‐scale preparation of PEGylated proteins.
Characterization of the genotoxicity of nitrilotriacetic acid
Authors: Nesslany Fabrice , Simar‐Meintières Sophie , Watzinger Malene , Talahari Ismail , Marzin Daniel 
Published: April 2008

AbstractThe chelating agent nitrilotriacetic acid (NTA), classified as an epigenetic rodent carcinogen, was assessed in the in vivo rodent Comet assay on isolated kidney cells. Unexpected potent increases in DNA damage were obtained in both the short (3–6 hr) and long‐term (22–26 hr) expression times after a single oral treatment at 1,000–2,000 mg/kg bw. NTA was assayed in the Ames test using TA1537, TA98, TA100, and TA102 tester strains, and in the in vitro micronucleus assay on L5178Y mouse lymphoma cells and on CTLL2 and CTLL2/Bcl2 cells coupled to the apoptosis measurement, both with and without metabolic activation by aroclor 1254‐induced liver or kidney rat S9‐mix. Whatever the S9 origin, neither genotoxicity nor apoptosis was detected, while a strong increase in the micronuclei formation was observed without S9 without any apoptosis induction. The direct genotoxicity of NTA was confirmed in the mouse lymphoma tk+/− gene mutation assay and in the chromosomal aberrations test on human lymphocytes. When tested in combination with an excess of Ca2+, NTA gave negative results on L5178Y mouse lymphoma cells in the in vitro Comet and micronucleus assays but still induced DNA damage on rat primary kidney cells. The higher sensitivity of renal cells to Ca2+ variations could explained the positive response observed in vivo. The carcinogenicity of NTA could be a consequence of the survival of kidney cells to intracellular variations of Ca2+, leading to a local and indirect genotoxicity. This suggests that threshold dose exists beyond which tumor‐generating events will be displayed. Environ. Mol. Mutagen., 2008. © 2008 Wiley‐Liss, Inc.
Testing for trends in the violation frequency of an environmental threshold in rivers
Authors: Clement Lieven , Thas Olivier 
Published: April 2008

AbstractNutrient pollution in rivers is a common problem. It can provoke algae blooms which are related to increased fish mortality. To restore the water status, the regulator recently has promulgated more restrictive regulations. In Flanders for instance, the government has introduced several manure decrees (MDs) to restrict nutrient pollution. Environmental regulations are commonly expressed in terms of threshold levels. This provides a binary response to the decision maker. To handle such data, we propose the use of marginalised generalised linear mixed models. They provide valid inference on trends in the exceedance frequency. The spatio‐temporal dependence of the river monitoring network is incorporated by the use of a latent variable. The temporal dependence is assumed to be AR(1) and the spatial dependence is derived from the river topology. The mean model contains a term for the trend and corrects for seasonal variation. The model formulation allows an assessment on the level of individual sampling locations and on a more regional scale. The methodology is applied to a case study on the river Yzer (Flanders). It assesses the impact of the MDs on the violation probability of the nitrate standard. A trend change is detected after the introduction of the second MD. Copyright © 2008 John Wiley & Sons, Ltd.
A linear benchmark for forecasting GDP growth and inflation?
Authors: Marcellino Massimiliano 
Published: April 2008

AbstractPredicting the future evolution of GDP growth and inflation is a central concern in economics. Forecasts are typically produced either from economic theory‐based models or from simple linear time series models. While a time series model can provide a reasonable benchmark to evaluate the value added of economic theory relative to the pure explanatory power of the past behavior of the variable, recent developments in time series analysis suggest that more sophisticated time series models could provide more serious benchmarks for economic models. In this paper we evaluate whether these complicated time series models can outperform standard linear models for forecasting GDP growth and inflation. We consider a large variety of models and evaluation criteria, using a bootstrap algorithm to evaluate the statistical significance of our results. Our main conclusion is that in general linear time series models can hardly be beaten if they are carefully specified. However, we also identify some important cases where the adoption of a more complicated benchmark can alter the conclusions of economic analyses about the driving forces of GDP growth and inflation. Copyright © 2008 John Wiley & Sons, Ltd.
The neuroglial population in the primary visual cortex of the aging rhesus monkey
Authors: Peters Alan , Verderosa Ameigh , Sethares Claire 
Published: April 2008

AbstractThe effects of age on neuroglial cells have been examined in the primary visual cortices of rhesus monkeys that had been behaviorally tested. The assessment of changes in the neuroglial populations was made on the basis of the frequency of occurrence of profiles of neuroglial cells in semithick sections of osmicated tissue stained with toluidine blue. No changes were found in the numbers of astrocytes and microglial cells with age, but the numbers of oligodendrocytes increased by about 50%. The myelinated nerve bundles at the level of layer 4 were also examined by electron microscopy to assess the effects of age on the nerve fibers. The numbers of nerve fiber profiles showing age‐related alterations in their myelin sheaths increase with age. There was also an age‐related increase in the frequency of profiles of nerve fibers sectioned through paranodes, indicating that shorter lengths of myelin are being produced by remyelination. These changes in sheaths both correlate significantly with the frequency of oligodendrocyte profiles, suggesting that with age additional oligodendrocytes are required to remyelinate nerve fibers whose sheaths have broken down, probably by death of the original parent oligodendroglial cell. Also the most cognitively impaired monkeys had the greatest numbers of oligodendrocytes, but this is probably a secondary correlation, reflecting the fact that altered myelin slows down the rate of conduction along nerve fibers, which leads to cognitive decline. © 2008 Wiley‐Liss, Inc.
Microglial phagocytosis is enhanced by monomeric α‐synuclein, not aggregated α‐synuclein: Implications for Parkinson's disease
Authors: Park Ji‐Young , Paik Seung R. , Jou Ilo , Park Sang Myun 
Published: April 2008

AbstractGathering evidence has associated activation of microglia with the pathogenesis of numerous neurodegenerative diseases of the central nervous system (CNS) such as Alzheimer's disease and Parkinson's disease. Microglia are the resident macrophages of the CNS whose functions include chemotaxis, phagocytosis, and secretion of a variety of cytokines and proteases. In this study, we examined the possibility that α‐synuclein (α‐syn), which is associated with the pathogenesis of Parkinson's disease, may affect the phagocytic function of microglia. We found that extracellular monomeric α‐syn enhanced microglial phagocytosis in both a dose‐ and time‐dependent manner, but β‐ and γ‐ syn did not. We also found that the N‐terminal and NAC region of α‐syn, especially the NAC region, might be responsible for the effect of α‐syn on microglial phagocytosis. In contrast to monomeric α‐syn, aggregated α‐syn actually inhibited microglial phagocytosis. The different effects of monomeric and aggregated α‐syn on phagocytosis might be related to their localization in cells. This study indicates that α‐syn can modulate the function of microglia and influence inflammatory changes such as those seen in neurodegenerative disorders. © 2008 Wiley‐Liss, Inc.
Expression of Notch‐1 receptor and its ligands Jagged‐1 and Delta‐1 in amoeboid microglia in postnatal rat brain and murine BV‐2 cells
Authors: Cao Qiong , Lu Jia , Kaur Charanjit , Sivakumar Viswanathan , Li Fan , Cheah Pike See , Dheen S. Thameem , Ling Eng‐Ang 
Published: April 2008

AbstractNotch‐1 receptor signaling pathway is involved in neuronal and glial differentiation. Its involvement in microglial functions, however, has remained elusive. This study reports the localization of Notch‐1 receptor immunoreactivity in the amoeboid microglial cells (AMC) in the postnatal rat brain. By immunofluorescence, Notch‐1 receptor was colocalized with its ligands, Jagged‐1 and Delta‐1, in the AMC in the corpus callosum and subventricular zone. Notch‐1 immunopositive cells were confirmed to be microglia labeled by OX42 and lectin. Immunoexpression of Notch‐1 receptor was progressively reduced with age. Western blot analysis showed that Notch‐1 protein level in the corpus callosum in which the AMC were heavily populated was concomitantly decreased. In postnatal rats challenged with lipopolysaccharide (LPS), Notch‐1 receptor immunofluorescence in AMC was noticeably enhanced. Furthermore, Notch‐1 protein level in the corpus callosum was increased as revealed by Western blotting analysis. In primary microglial culture treated with LPS, mRNA expression of Notch‐1 and its ligand Jagged‐1 was upregulated but that of Delta‐1 was reduced. The expression pattern of Notch‐1 and its ligands was confirmed in murine BV‐2 cells. Furthermore, Notch‐1 neutralization with its antibody reduced its protein expression. More importantly, neutralization of Notch‐1 concomitantly suppressed the mRNA expression of IL‐6, IL‐1, M‐CSF, and iNOS; TNF‐α, mRNA expression, however, was enhanced. Western blot confirmed the changes of protein level of the above except for IL‐6, which remained relatively unaltered. It is concluded that Notch‐1 signaling in the AMC and LPS‐activated microglia/BV‐2 cells modulates the expression of proinflammatory cytokines and nitric oxide. © 2008 Wiley‐Liss, Inc.
Variation in the prevalence of gastric cancer in Perú
Authors: Mendoza Daniel , Herrera Phabiola , Gilman Robert H. , Lanfranco Julio , Tapia Martín , Bussalleu Alejandro , Tenorio Jorge Huerta‐Mercado , Guillén‐Rodríguez Carlos Enrique , Arróspide Martín Tagle , Piscoya Alejandro , Rosas‐Aguirre Angel , Watanabe‐Yamamoto José , Ferrufino Juan Carlos , Scavino Yolanda , Ramírez‐Ramos Alberto 
Published: April 2008

AbstractMost cases of gastric cancers occur in non‐industrialized countries but there is scarce information about the epidemiology of this illness in these countries. Our study examined whether there was a variation in the prevalence of gastric cancer in Lima, Perú over the last 2 decades. Subjects older than 29 years of age were included. They underwent an esophagogastroduedonoscopy at 3 socioeconomically different health facilities in Lima: a county hospital (7,168 subjects), a Peruvian‐Japanese Clinic (14,794 individuals) and a private hospital (4,893 individuals). Birth cohort prevalence of gastric cancer was used. Regression models were calculated to predict the future prevalence of gastric cancer. It was found that the birth cohort prevalence of gastric cancer decreased in Perú from 22.7 to 2% (p < 0.001), from 12 to 0.5% (p < 0.001), and from 6.5 to 0.1% (p < 0.001) in the low, middle and high socioeconomic group, respectively. The prevalence of intestinal metaplasia decreased from 44.3 to 12.5% (p < 0.001), from 28.4 to 5% (p < 0.001), and from 19.4 to 2.2% (p < 0.001) in the low, middle and high socioeconomic status, respectively. These trends will likely persist over the future decades. Nevertheless, the prevalence of gastric cancer remains high in subjects older than 59 years of age in the low socioeconomic status. It is concluded that the prevalence of gastric cancer is decreasing in Perú, similar to the current trend undergoing in industrialized nations. However, there are still specific groups with high prevalence that might benefit from screening for early detection and treatment. © 2008 Wiley‐Liss, Inc.