bluuebunny/crossref_metadata_2025_split huggingface dataset:
Asymmetric hydrogenation of diketones catalyzed by magnesium oxide‐supported chitosan–Rh complex
Authors: Zhou Da‐Qing , He Man , Zhang Yan‐Hong , Huang Mei‐Yu , Jiang Ying‐Yan 
Published: April 2003

AbstractMgO‐supported chitosan–Rh complex (MgO‐CS‐Rh) has been prepared and found to be a highly stereoselective catalyst for the asymmetric hydrogenation of some diketones to corresponding chiral alcohols, such as 2,3‐butanedione to (2S,3S)‐(+)‐2,3‐butanediol and 2,4‐pentanedione to (2S,4S)‐(+)‐2,4‐pentanediol at room temperature and under 1 atm H2. The optical yield was greatly affected by the Rh content in the complex, the solvent and the reaction temperature. The optical yields of (2S,3S)‐(+)‐2,3‐butanediol and (3S,4S)‐(+)‐2,4‐pentanediol obtained were 87% and 81.2%, respectively. The chiral chitosan–Rh complex catalyst was very easy to prepare, and could be reused without noticeable change in its optical catalytic activity. Copyright © 2003 John Wiley & Sons, Ltd.
Enzymatic polymerization of aniline and phenol derivatives catalyzed by horseradish peroxidase in dioxane(II)
Authors: Shan Jinyu , Han Liyou , Bai Fenglian , Cao Shaokui 
Published: April 2003

AbstractAminophenols, methoxyanilines and 1‐naphthylamine were polymerized via the catalysis of horseradish peroxidase in dioxane at ambient conditions by using hydrogen peroxide as the oxidant. Polymers formed in good yields when using double the amount of the oxidant. The molecular weight of the polymers was determined by gel permeation chromatography, and the polymer structures were characterized by using nuclear magnetic resonance and infrared techniques. The polymerization of aminophenols and 1‐naphthylamine gave relatively high yields, while the polymer yields of methoxyanilines were very low. Except for 4‐methoxyaniline giving 23.5% yield, 2‐ and 3‐methoxyaniline gave < 20% and < 10% yield respectively. The polymer of 2‐aminophenol was characterized as a linear, phenoxazine‐like structure, while poly(4‐aminophenol) has a linear, meta‐oriented structure with the preservation of a hydroxyl group. Both of these are very different to those formed by chemical or electrochemical methods. Poly(3‐aminophenol) and poly(1‐naphthylamine) formed by enzymatic polymerization have very complicated structures. UV‐vis spectra and the cyclic voltammograms of the polymers produced were also examined. It has been proved that poly(2‐aminophenol) and poly(4‐aminophenol) have electroactivity with respect to a saturated HgCl2 electrode in 1 M HCl. Copyright © 2003 John Wiley & Sons, Ltd.
The synthesis and characterization of polyurethane/clay nanocomposites
Authors: Zhang Xinmin , Xu Rongjing , Wu Zenggang , Zhou Chixing 
Published: April 2003

AbstractThe water absorption of montmorillonite was studied using TGA and FTIR, and a removal method through boiling with toluene was investigated. PU/MMT was synthesized and its morphology, thermal dynamic mechanical properties and tensile behaviour were investigated by WAXD, FTIR, DMTA and Instron techniques. We find that, compared with the PU matrix, the intercalated PU/MMT nanocomposite was reinforced and toughened by the addition of nanometer‐size MMT layers. Copyright © 2003 Society of Chemical Industry
γ‐Crystalline form of nylon‐10,10 in nylon‐10,10–montmorillonite nanocomposite
Authors: Zhang Guosheng , Li Yongjin , Yan Deyue 
Published: April 2003

AbstractWide‐angle X‐ray diffraction (WAXD) and variable temperature WAXD spectroscopy and Fourier‐transform infrared (FTIR) spectrometry were used to identify the γ‐crystalline form of nylon‐10,10 in the nanocomposite of nylon‐10,10 and montmorillonite. A new diffraction peak at 2θ = 22° was observed in the WAXD pattern of the nanocomposite as compared with nylon‐10,10, and the data of variable temperature WAXD indicated that it was the characteristic peak of γ‐crystalline form of nylon‐10,10. The amide VI band at 624 cm−1 was also observed in the FTIR spectrum of the nanocomposite, which is characteristic of γ‐crystalline nylon. In addition, the shoulder peak at 1553 cm−1 can be assigned to the amide II band of γ‐crystalline form of nylon‐10,10. Copyright © 2003 Society of Chemical Industry
Catalytic synthesis and characterization of an alternating copolymer from carbon dioxide and propylene oxide using zinc pimelate
Authors: Zhu Q , Meng YZ , Tjong SC , Zhang YM , Wan W 
Published: April 2003

AbstractNew zinc pimelate catalysts used for copolymerization of carbon dioxide and propylene oxide have been synthesized in high yield by a magnetic stirring method. The regular molecular structure of the zinc pimelate was confirmed by Fourier‐transform infrared spectroscopy and wide‐angle X‐ray diffraction techniques. Accordingly, poly(propylene carbonate) (PPC) can be synthesized from carbon dioxide and propylene oxide using these zinc pimelate catalysts. High catalytic efficiency (95.2 gram polymer per gram catalyst or 21 300 g of polymer per mole of zinc) was achieved by optimizing the PO/catalyst ratio. NMR measurement revealed that the PPC synthesized had an alternating copolymer structure. The thermal properties of PPC were determined by modulated differential scanning calorimetry and thermogravimetric analysis. The results demonstrated that the PPC copolymer exhibited an extremely high glass transition temperature of 44.27 °C and decomposition temperature of 257 °C, comparable with values reported in literature. Copyright © 2003 Society of Chemical Industry
Synthesis of polymer–inorganic hybrid nanoparticles via radical polymerization initiated by surface‐immobilized photoiniferter
Authors: Bai Jie , Qiu Kun‐Yuan , Wei Yen 
Published: April 2003

AbstractPolymer–inorganic hybrid nanoparticles were prepared through radical photo‐polymerization of methyl methacrylate initiated by N,N‐diethyldithiocarbamyl surface functionalized silica nanoparticles under UV irradiation at ambient temperature. IR analysis and UV spectroscopy confirmed the occurrence of Et2NCS2—end groups on the resulting poly(methyl methacrylate), and the morphology of these hybrid nanoparticles was observed directly by means of tapping mode atomic force microscopy (AFM). Copyright © 2003 Society of Chemical Industry
Filler effect on polymerization kinetics and phase separation in polymer blends formed in situ
Authors: Lipatov Yu S , Kosyanchuk L V , Nesterov A E , Antonenko O I 
Published: April 2003

AbstractThe kinetics of formation of a mixture of two polymers [poly(methyl methacrylate) and polyurethane] in situ in the course of two simultaneously proceeding reactions was studied in the presence of various amount of a filler (fumed silica). It was shown that the filler affects the rates of both reactions. In addition, the filler exerts an influence on the phase separation induced by the chemical reaction increasing the amount of a filler increases the time for the onset of phase separation. The effects observed may be explained both by the increase in the viscosity of the reaction system due to introduction of a filler and by selective adsorption of reaction system components at the interface with filler particles. In all cases, phase separation in the early stages of reaction proceeds in a four‐component system (two polymers formed and two initial compounds) and obeys the spinodal mechanism. It is also shown that the final morphology is determined far from the end of the reaction and before establishing the equilibrium state.© 2003 Society of Chemical Industry
Fractional occupation numbers and spin density functional calculations of degenerate systems
Authors: Takeda R. , Yamanaka S. , Yamaguchi K. 
Published: April 2003

AbstractWe implemented ab initio self‐consistent field (SCF) fractional occupation numbers (FON) calculation with Dunlap's interpolation scheme for the twisted ethylene, which is a prototype molecule of a σ–π biradical system. The calculational results are compared with those of complete‐active‐space (CAS) SCF and spin‐unrestricted Kohn–Sham (UKS) calculations on potential surfaces, occupation numbers of natural orbitals, and correlation entropies. It was found that the UKS methods gave similar results to CASSCF, while the FON solutions appeared in only the nearly complete degenerate region. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem 93: 317–323, 2003
Density functional study of the conformers of Co4‐based single‐molecule magnet
Authors: Baruah Tunna , Pederson Mark R. 
Published: April 2003

AbstractWe present a detailed density functional theory‐based investigation on the geometry and electronic structure of the [Co4(hmp)4(MeOH)4Cl4] molecule. It is experimentally found to behave as a molecular magnet. The all‐electron electronic structure calculations and geometry optimization of the 88‐atom molecule were carried out within the generalized gradient approximation to the exchange correlation energy. We also study the electronic structures and geometries of a few low‐lying conformers of this molecule. It is found that the magnetic anisotropy energy is highly sensitive to the geometric structure of the molecule. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem 93: 324–331, 2003
Metal–insulator transition in the Hubbard model on a triangular lattice with disorders: Renormalization group approach
Authors: Wang J. X. , Kais Sabre 
Published: April 2003

AbstractA multistages block renormalization group approach to study the metal–insulator transition in the Hubbard model on a triangular lattice with hexagonal blocks is presented and implemented. A second‐order phase transition with a critical point at U/t = 12.5 is obtained (the coupling parameters U and t correspond to the repulsive charging energy and to the nearest‐neighbor exchange coupling terms, respectively). In the presence of disorder the phase diagram for the system exhibits a metallic phase, an insulating phase, and a domain‐localized phase that separates them in the Mott regime. The subtle influence of electron–electron interactions upon inverse participation rate in the Anderson regime is also investigated. The results are discussed in light of experimental evidence for arrays of metalic quantum dots and exact numerical diagonalization of the Hubbard Hamiltonian. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem 93: 360–374, 2003
African Swine Fever Virus Proteinase Is Essential for Core Maturation and Infectivity
Authors: Alejo Alí , Andrés Germán , Salas María L. 
Published: April 2003

ABSTRACT
African swine fever virus (ASFV) encodes two polyprotein precursors named pp220 and pp62 that are sequentially processed during viral infection, giving rise to six major structural proteins. These reside at the core shell, a matrix domain located between the endoplasmic reticulum-derived inner envelope and the DNA-containing nucleoid. Proteolytic processing of the polyprotein precursors is catalyzed by the viral proteinase pS273R, a cysteine proteinase that shares sequence similarity with the SUMO1-processing peptidases. We describe here the construction and characterization of an ASFV recombinant, vS273Ri, that inducibly expresses the ASFV proteinase. Using vS273Ri, we show that repression of proteinase expression inhibits polyprotein processing and strongly impairs infective virus production. Electron microscopic examination of vS273Ri-infected cells showed that inhibition of proteolytic processing leads to the assembly of defective icosahedral particles containing a noncentered electron-dense nucleoid surrounded by an abnormal core shell of irregular thickness. The analysis of purified extracellular defective particles revealed that they contain the unprocessed pp220 and pp62 precursors, as well as the major DNA-binding nucleoid proteins p10 and pA104R. Altogether, these results indicate that the proteolytic processing of the polyproteins is not required for their incorporation into the assembling particles nor for the incorporation of the DNA-containing nucleoid. Instead, the ASFV proteinase is involved in a late maturational step that is essential for proper core assembly and infectivity.
Kaposi's Sarcoma-Associated Herpesvirus Lytic Origin (
ori-Lyt
)-Dependent DNA Replication: Identification of the
ori-Lyt
and Association of K8 bZip Protein with the Origin
Authors: Lin Cui Li , Li Hong , Wang Yan , Zhu Fan Xiu , Kudchodkar Sagar , Yuan Yan 
Published: April 2003

ABSTRACT

Herpesviruses utilize different origins of replication during lytic versus latent infection. Latent DNA replication depends on host cellular DNA replication machinery, whereas lytic cycle DNA replication requires virally encoded replication proteins. In lytic DNA replication, the lytic origin (
ori-Lyt
) is bound by a virus-specified origin binding protein (OBP) that recruits the core replication machinery. In this report, we demonstrated that DNA sequences in two noncoding regions of the Kaposi's sarcoma-associated herpesvirus (KSHV) genome, between open reading frames (ORFs) K4.2 and K5 and between K12 and ORF71, are able to serve as origins for lytic cycle-specific DNA replication. The two
ori-Lyt
domains share an almost identical 1,153-bp sequence and a 600-bp downstream GC-rich repeat sequence, and the 1.7-kb DNA sequences are sufficient to act as a
cis
signal for replication. We also showed that an AT-palindromic sequence in the
ori-Lyt
domain is essential for the DNA replication. In addition, a virally encoded bZip protein, namely K8, was found to bind to a DNA sequence within the
ori-Lyt
by using a DNA binding site selection assay. The binding of K8 to this region was confirmed in cells by using a chromatin immunoprecipitation method. Further analysis revealed that K8 binds to an extended region, and the entire region is 100% conserved between two KSHV
ori-Lyt
's. K8 protein displays significant similarity to the Zta protein of Epstein-Barr virus (EBV), which is a known OBP of EBV. This notion, together with the ability of K8 to bind to the KSHV
ori-Lyt
, suggests that K8 may function as an OBP in KSHV.
Tmevpg1, a Candidate Gene for the Control of Theiler's Virus Persistence, Could Be Implicated in the Regulation of Gamma Interferon
Authors: Vigneau Soline , Rohrlich Pierre-Simon , Brahic Michel , Bureau Jean-François 
Published: April 2003

ABSTRACTTheTmevp3locus controls the load of Theiler's virus RNA during persistent infection of the mouse central nervous system (CNS). We identified a candidate gene at this locus,Tmevpg1, by using a positional cloning approach.Tmevpg1and its human ortholog,TMEVPG1, are expressed in the immune system and encode what appears to be a noncoding RNA. They are located in a cluster of cytokine genes that includes the genes for gamma interferon and one or two homolog of interleukin-10. We now report thatTmevpg1is expressed in CNS-infiltrating immune cells of resistant B10.S mice, but not in those of susceptible SJL/J mice, following inoculation with Theiler's virus. The pattern of expression ofTmevpg1is the same in B10.S mice and in SJL/J mice congenic for the resistant B10.S haplotype ofTmevp3. Nineteen polymorphisms were identified when theTmevpg1genes of B10.S and SJL/J mice were compared. Interestingly,Tmevpg1is down regulated after in vitro stimulation of murine CD4+or CD8+splenocytes, whereasIfngis up regulated. Similar patterns of expression ofTMEVPG1andIFNGwere observed in human NK cells and CD4+and CD8+T lymphocytes. Therefore,Tmevpg1is a strong candidate gene for theTmevp3locus and may be involved in the control ofIfnggene expression.
Transcriptional Regulatory Properties of Epstein-Barr Virus Nuclear Antigen 3C Are Conserved in Simian Lymphocryptoviruses
Authors: Zhao Bo , Dalbiès-Tran Rozenn , Jiang Hua , Ruf Ingrid K. , Sample Jeffery T. , Wang Fred , Sample Clare E. 
Published: April 2003

ABSTRACT
Epstein-Barr virus (EBV) nuclear antigen 3C (EBNA-3C) is a large transcriptional regulator essential for EBV-mediated immortalization of B lymphocytes. We previously identified interactions between EBNA-3C and two cellular transcription factors, Jκ and Spi proteins, through which EBNA-3C regulates transcription. To better understand the contribution of these interactions to EBNA-3C function and EBV latency, we examined whether they are conserved in the homologous proteins of nonhuman primate lymphocryptoviruses (LCVs), which bear a strong genetic and biological similarity to EBV. The homologue of EBNA-3C encoded by the LCV that infects baboons (BaLCV) was found to be only 35% identical in sequence to its EBV counterpart. Of particular significance, this homology localized predominantly to the N-terminal half of the molecule, which encompasses the domains in EBNA-3C that interact with Jκ and Spi proteins. Like EBNA-3C, both BaLCV and rhesus macaque LCV (RhLCV) 3C proteins bound to Jκ and repressed transcription mediated by EBNA-2 through its interaction with Jκ. Both nonhuman primate 3C proteins were also able to activate transcription mediated by the Spi proteins in the presence of EBNA-2. Like EBNA-3C, a domain encompassing the putative basic leucine zipper motif of the BaLCV-3C protein directly interacted with both Spi-1 and Spi-B. Surprisingly, a recently identified motif in EBNA-3C that mediates repression was not identifiable in the BaLCV-3C protein. Finally, although the C terminus of BaLCV-3C bears minimal homology to EBNA-3C, it nonetheless contains a C-terminal domain rich in glutamine and proline that was able to function as a potent transcriptional activation domain, as does the C terminus of EBNA-3C. The conservation of these functional motifs despite poor overall homology among the LCV 3C proteins strongly suggests that the interactions of EBNA-3C with Jκ and Spi do indeed play significant roles in the life cycle of EBV.
Direct Relationship between Suppression of Virus-Specific Immunity and Emergence of Cytomegalovirus Disease in Simian AIDS
Authors: Kaur Amitinder , Kassis Nadine , Hale Corrina L. , Simon Meredith , Elliott Michelle , Gomez-Yafal Alicia , Lifson Jeffrey D. , Desrosiers Ronald C. , Wang Fred , Barry Peter , Mach Michael , Johnson R. Paul 
Published: April 2003

ABSTRACTAlthough opportunistic infections like cytomegalovirus (CMV) are common sequelae of end-stage AIDS, the immune events leading to CMV reactivation in human immunodeficiency virus (HIV)-infected individuals are not well defined. The role of cellular and humoral CMV-specific immune responses in immune control of latent CMV infection was evaluated prospectively in a cohort of 11 simian immunodeficiency virus (SIV)-infected CMV-seropositive rhesus macaques, 6 of whom had histologic evidence of CMV disease at death. Macaques with CMV disease differed from macaques without CMV disease in having significantly higher levels of plasma SIV RNA and CMV DNA and significantly lower titers of anti-CMV binding antibodies (Abs) at the time of death. A significant decline in anti-CMV Abs and CMV-specific CD4+and CD8+T lymphocytes over time was observed in the macaques with CMV disease, but not in the macaques without CMV disease. Reduction in CMV-specific CD8+T lymphocytes and anti-CMV neutralizing Abs was significantly correlated with a decline in CMV-specific CD4+T lymphocytes. Although declines in CMV-specific T lymphocytes alone were sufficient for reactivation of low-level CMV viremia, high-level viremia (>1,000 copies of CMV DNA per ml of plasma) was observed when anti-CMV neutralizing and binding Abs had also declined. Thus, the occurrence of CMV reactivation-associated disease in AIDS is associated with suppression of both cellular and humoral CMV-specific immune responses. The underlying mechanism may be a dysfunction of memory B and CD8+T lymphocytes associated with SIV-induced impairment of CMV-specific CD4+T-cell help.
Positive Regulation of CXCR4 Expression and Signaling by Interleukin-7 in CD4+Mature Thymocytes Correlates with Their Capacity To Favor Human Immunodeficiency X4 Virus Replication
Authors: Schmitt Nathalie , Chêne Laurent , Boutolleau David , Nugeyre Marie-Thérèse , Guillemard Eric , Versmisse Pierre , Jacquemot Catherine , Barré-Sinoussi Françoise , Israël Nicole 
Published: April 2003

ABSTRACTThe emergence of X4 human immunodeficiency virus type 1 (HIV-1) variants in infected individuals is associated with poor prognosis. One of the possible causes of this emergence might be the selection of X4 variants in some specific tissue compartment. We demonstrate that the thymic microenvironment favors the replication of X4 variants by positively modulating the expression and signaling of CXCR4 in mature CD4+CD8−CD3+thymocytes. Here, we show that the interaction of thymic epithelial cells (TEC) with these thymocytes in culture induces an upregulation of CXCR4 expression. The cytokine secreted by TEC, interleukin-7 (IL-7), increases cell surface expression of CXCR4 and efficiently overcomes the downregulation induced by SDF-1α, also produced by TEC. IL-7 also potentiates CXCR4 signaling, leading to actin polymerization, a process necessary for virus entry. In contrast, in intermediate CD4+CD8−CD3−thymocytes, the other subpopulation known to allow virus replication, TEC or IL-7 has little or no effect on CXCR4 expression and signaling. CCR5 is expressed at similarly low levels in the two thymocyte subpopulations, and neither its expression nor its signaling was modified by the cytokines tested. This positive regulation of CXCR4 by IL-7 in mature CD4+thymocytes correlates with their high capacity to favor X4 virus replication compared with intermediate thymocytes or peripheral blood mononuclear cells. Indeed, we observed an enrichment of X4 viruses after replication in thymocytes initially infected with a mixture of X4 (NL4-3) and R5 (NLAD8) HIV strains and after the emergence of X4 variants from an R5 primary isolate during culture in mature thymocytes.
Lentivirus Vectors Pseudotyped with Filoviral Envelope Glycoproteins Transduce Airway Epithelia from the Apical Surface Independently of Folate Receptor Alpha
Authors: Sinn Patrick L. , Hickey Melissa A. , Staber Patrick D. , Dylla Douglas E. , Jeffers Scott A. , Davidson Beverly L. , Sanders David A. , McCray Paul B. 
Published: April 2003

ABSTRACT
The practical application of gene therapy as a treatment for cystic fibrosis is limited by poor gene transfer efficiency with vectors applied to the apical surface of airway epithelia. Recently, folate receptor alpha (FRα), a glycosylphosphatidylinositol-linked surface protein, was reported to be a cellular receptor for the filoviruses. We found that polarized human airway epithelia expressed abundant FRα on their apical surface. In an attempt to target these apical receptors, we pseudotyped feline immunodeficiency virus (FIV)-based vectors by using envelope glycoproteins (GPs) from the filoviruses Marburg virus and Ebola virus. Importantly, primary cultures of well-differentiated human airway epithelia were transduced when filovirus GP-pseudotyped FIV was applied to the apical surface. Furthermore, by deleting a heavily O-glycosylated extracellular domain of the Ebola GP, we improved the titer of concentrated vector severalfold. To investigate the folate receptor dependence of gene transfer with the filovirus pseudotypes, we compared gene transfer efficiency in immortalized airway epithelium cell lines and primary cultures. By utilizing phosphatidylinositol-specific phospholipase C (PI-PLC) treatment and FRα-blocking antibodies, we demonstrated FRα-dependent and -independent entry by filovirus glycoprotein-pseudotyped FIV-based vectors in airway epithelia. Of particular interest, entry independent of FRα was observed in primary cultures of human airway epithelia. Understanding viral vector binding and entry pathways is fundamental for developing cystic fibrosis gene therapy applications.