bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of branched polyethylene by ethylene homopolymerization using titanium catalysts that contain a bridged bis(phenolate) ligand
Authors: Capacchione Carmine , Proto Antonio , Okuda Jun 
Published: April 2004

AbstractThe synthesis of branched polyethylene from single ethylene feed has been achieved by using a methylaluminoxane‐activated titanium complex bearing a tetradentate bis(phenolate) ligand with a 1,4‐dithiabutanediyl bridge 1. This catalyst produces polyethylene with activities up to 6200 kg polymer/mol h bar. As evidenced by 13C NMR analyses, the polyethylenes contain ethyl, n‐butyl, and long‐chain (n‐hexyl or longer) branches in a range variable from 0.2 to 2.0%, depending on the experimental parameters. NMR and gas chromatography/mass spectrometry analyses suggest that such polymer microstructure arises from the in situ production of oligomers and their subsequent incorporation into the growing polyethylene chain. The broad molecular weight distribution of these polyethylenes indicates the presence of different catalytic species. The related catalyst system 2 bearing a longer 1,5‐dithiapentanediyl bridge produces linear polyethylene with moderate activity. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2815–2822, 2004
The cis‐pro touch‐turn: A rare motif preferred at functional sites
Authors: Videau Lizbeth L. , Arendall W. Bryan , Richardson Jane S. 
Published: April 2004

AbstractA new motif of three‐dimensional (3D) protein structure is described, called the cis‐Pro touch‐turn. In this four‐residue, three‐peptide motif, the central peptide is cis. Residue 2, which precedes the proline, has ϕ, ψ values either in the “prePro region” of the Ramachandran plot near −130°, 75° or in the Lα region near +60°, +60°. The Cα(1)–Cα(4) distance is 4–5 Å and the two flanking peptides lie parallel to one another, making van der Waals contact rather than a hydrogen bond. Apparently, this arrangement is locally unfavorable and therefore rare, usually occurring only if needed for biological function. Of the 12 examples in a 500‐protein database, cis‐Pro touch‐turns are found at the catalytic sites of pectate lyase, Ni‐Fe hydrogenase, glucoamylase, xylanase, and opine dehydrogenase and at the primary binding sites of ribonuclease H, type I DNA polymerase, ribotoxin, and phage gene 3 protein. In each of these protein families, the touch‐turns serve different roles; their functional importance is supported by conservation and mutagenesis data. In analyzing the conservation patterns of these 3D motifs, new methods for in‐depth quality evaluation of the structural bioinformatic data are employed to distinguish between significant exceptions and errors. Proteins 2004. © 2004 Wiley‐Liss, Inc.
Predicted role for the archease protein family based on structural and sequence analysis of TM1083 and MTH1598, two proteins structurally characterized through structural genomics efforts
Authors: Canaves Jaume M. 
Published: April 2004

AbstractRecently, the structures of two proteins belonging to the archease family, TM1083 from Thermotoga maritima and MTH1598 from Methanobacterium thermoautotrophicum, have been solved independently by two Protein Structure Initiative structural genomics pilot centers using X‐ray crystallography and NMR, respectively. The archease protein family is a good example of one of the paradoxes of structural genomics: Approximately one third of protein structures produced by structural genomics centers have no known function and are still annotated as “hypothetical proteins” in the Protein Data Bank. In the case of archeases, despite the existence of two protein structures and abundant sequence information, there is still no function assigned to this protein family. Here, our group predicts, based on structural similarity, sequence conservation, and gene context analyses, that members of this protein family might function as chaperones or modulators of proteins involved in DNA/RNA processing. The conservation of genomic context for this protein family is constant from Archaea and Bacteria to humans, and suggests that unannotated open reading frames contiguous to them could be novel RNA/DNA binding proteins. Proteins 2004. © 2004 Wiley‐Liss, Inc.
Ab initio study of the CH3O2 self‐reaction in gas phase: Elucidation of the CH3O2 CH3O2 → 2CH3O O2 pathway
Authors: Feria L. , Gonzalez C. , Castro M. 
Published: April 2004

AbstractAb initio electronic structure calculations have been performed to determine the mechanism governing the 2CH3O2 → 2CH3O + O2 chemical reaction in gas phase. Geometry optimizations for reactants, intermediates, transition states, and products were performed at the MP2 level of theory with the 6‐311G(2d,2p) basis sets. Further, PMP4(SDTQ)/6‐311G(3df,2p) single‐point calculations were performed on the previous MP2/6‐311G(2d,2p)‐optimized geometries. For the past 50 years, it has been proposed that the production of CH3O and O2 in the self‐reaction of methylperoxyl radicals is the result of the direct dissociation of a noncyclic tetraoxide intermediate via a concerted mechanism involving a single step. Our theoretical results indicate that the reaction path is more complex than expected. We found that the reaction proceeds through a nonconcerted mechanism involving two tetraoxide intermediates that have different geometries and relative energies. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Wiener polynomials of some chemically interesting graphs
Authors: Yang Bo‐Yin , Yeh Yeong‐Nan 
Published: April 2004

AbstractThe chemist Harold Wiener found 𝒲(G), the sum of distances between all pairs of vertices in a connected graph G, to be useful as a predictor of certain physical and chemical properties. The q‐analogue of 𝒲, called the Wiener polynomial 𝒲(G; q), is also useful, but it has few existing useful formulas. We will evaluate 𝒲(G; q) for certain graphs G of chemical interest. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Airway Abnormalities in Patients with Arnold‐Chiari Malformation
Authors: Choi Sukgi S. , Tran Lenhanh P. , Zalzal George H. 
Published: April 2004

OBJECTIVESThe goal was to determine the incidence and types of airway abnormalities in patients with Arnold‐Chiari malformation (ACM).METHODSThe study was a retrospective chart review of 24 patients with ACM who were evaluated and treated between November 1991 and August 1997.RESULTSEighteen (75%) and 6 (25%) of the 24 patients had types I and II ACM, respectively. Three (12.5% of 24 patients) of the type II ACM patients had vocal cord impairment: 1 bilateral paralysis, 1 bilateral paresis, and 1 unilateral paralysis. None of the type I ACM patients had vocal cord impairment. Tracheotomy was necessary in 3 of the 24 patients and all in patients with type II ACM. Central sleep apnea was found in 5 of 6 type II ACM patients, but not in any of the type I ACM patients.CONCLUSIONSVocal cord impairment and sleep apnea were found in 12.5% and 21%, respectively, of this ACM Population. When type II ACM patients were considered separately, the incidences of vocal cord impairment and sleep apnea were 50% and 83%, respectively. Type II ACM patients tend to have a higher incidence of airway abnormalities and other neurologic dysfunctions. Flexible fiberoptic laryngoscopy is recommended in the airway evaluation of ACM patients. Early recognition, diagnosis, and management of these abnormalities may be lifesaving.
Wind‐mediated spread of Rice yellow mottle virus (RYMV) in irrigated rice crops
Authors: Sarra S. , Oevering P. , Guindo S. , Peters D. 
Published: April 2004

A study was carried out to demonstrate that Rice yellow mottle virus (RYMV), a virus known to be transmitted by beetles, can spread between rice plants by direct leaf contact caused by wind. Almost all healthy plants surrounding an infected plant became infected when exposed to a fan blowing for 15 min at a distance of 50 cm. Spread of RYMV by plant contact, mediated by wind, was also demonstrated in field experiments, the extent of spread depending on plant density. Infection was almost 10 times higher in plots with a density of 33 plants m−2 than in plots with 16 plants m−2. Less spread was observed in plots protected by 1·5 m high windscreens. It is suggested that wind‐mediated spread of RYMV may result from abrasive contact between leaves of plants.
Characterization of Armillaria heimii from Africa
Authors: Pérez‐Sierra A. , Guillaumin J.‐J. , Spooner B. M. , Bridge P. D. 
Published: April 2004

Armillaria heimii is one of the most widespread Armillaria species recorded in Africa. The species was originally described as Clitocybe (Armillariella) elegans Heim, and was renamed as Armillaria heimii Pegler; this name was subsequently made synonymous with A. fuscipes Petch to represent as a single morphological species. Recent molecular work has suggested that isolates previously identified as A. heimii were distinct and may represent A. fuscipes or another Armillaria species. A collection of isolates that had been identified as A. heimii from different African countries were included in an integrated study that included amplified restriction‐length polymorphism (AFLP) fingerprinting, polymerase chain reaction‐restriction fragment‐length polymorphism (PCR‐RFLP), sequencing, induction of basidiomata in vitro and somatic compatibility, in order to determine their identity. Although the isolates could be assigned to one of two molecular groups, the morphology and somatic compatibility characters suggested that the two groups represent different forms of a single species that closely matches the original description of A. heimii.
A controlled environment test for resistance to Soil‐borne cereal mosaic virus (SBCMV) and its use to determine the mode of inheritance of resistance in wheat cv. Cadenza and for screening Triticum monococcum genotypes for sources of SBCMV resistance
Authors: Kanyuka K. , Lovell D. J. , Mitrofanova O. P. , Hammond‐Kosack K. , Adams M. J. 
Published: April 2004

Several wheat genotypes, including eight with known field responses, were evaluated for their reaction to Soil‐borne cereal mosaic virus (SBCMV, genus Furovirus) by growing in naturally infested soil under controlled environment conditions. Virus antigen titres in the foliage 8–9 weeks after sowing mostly reflected the field responses, showing that growth chamber‐based tests can be used to improve the speed and reliability of germplasm screening. Such tests were used to determine the mode of inheritance of the SBCMV resistance in cv. Cadenza, commonly used in UK wheat‐breeding programmes. One hundred and eleven doubled haploid (DH) lines derived from an F1 of a cross between cvs Cadenza (resistant) and Avalon (susceptible) were evaluated. This DH population segregated for the reaction to SBCMV in a ratio of 1 : 1 (resistant : susceptible). This suggests that the SBCMV resistance is controlled by a single gene locus. As a first step towards identification of new sources of improved SBCMV resistance (e.g. immunity) as well as sources of the resistance to the virus vector, Polymyxa graminis, a set of 26 Triticum monococcum lines of diverse geographical origin was also screened. Most lines were susceptible to SBCMV, but one line of Bulgarian origin was resistant to the virus and possibly partially resistant to the virus vector.
The Plant Virus
Tomato Spotted Wilt Tospovirus
Activates the Immune System of Its Main Insect Vector,
Frankliniella occidentalis
Authors: Medeiros Ricardo B. , Resende Renato de O. , de Ávila Antonio Carlos 
Published: April 2004

ABSTRACT

Tospoviruses have the ability to infect plants and their insect vectors.
Tomato spotted wilt virus
(TSWV), the type species in the
Tospovirus
genus, infects its most important insect vector,
Frankliniella occidentalis
, the western flower thrips (WFT). However, no detrimental effects on the life cycle or cytopathological changes have been reported in the WFT after TSWV infection, and relatively few viral particles can be observed even several days after infection. We hypothesized that TSWV infection triggers an immune response in the WFT. Using subtractive cDNA libraries to probe WFT DNA macroarrays, we found that the WFT's immune system is activated by TSWV infection. The activated genes included (i) those encoding antimicrobial peptides, such as defensin and cecropin; (ii) genes involved in pathogen recognition, such as those encoding lectins; (iii) those encoding receptors that activate the innate immune response, such as Toll-3; and (iv) those encoding members of signal transduction pathways activated by Toll-like receptors, such as JNK kinase. Transcriptional upregulation of these genes after TSWV infection was confirmed by Northern analysis, and the kinetics of the immune response was measured over time. Several of the detected genes were activated at the same time that viral replication was first detected by reverse transcription-PCR. To our knowledge, this is the first report of the activation of an insect vector immune response by a plant virus. The results may lead to a better understanding of insects' immune responses against viruses and may help in the future development of novel control strategies against plant viruses, as well as human and animal viruses transmitted by insect vectors.
An Early Stage of Mason-Pfizer Monkey Virus Budding Is Regulated by the Hydrophobicity of the Gag Matrix Domain Core
Authors: Stansell Elizabeth , Tytler Ewan , Walter Mark R. , Hunter Eric 
Published: April 2004

ABSTRACT
Intracellular capsid transport and release of Mason-Pfizer monkey virus are dependent on myristylation of the Gag matrix domain (MA). A myristylated MA mutant, in which Thr41 and Thr78 are replaced with isoleucines, assembles capsids that are transported to the plasma membrane but are blocked in an early budding step. Since the nuclear magnetic resonance structure of MA showed that these Thr residues point into the hydrophobic core of the protein, it was hypothesized that the T41I/T78I mutant was defective in release of myristic acid from the more hydrophobic core. In order to further investigate whether an increase in the hydrophobicity of the MA core modulates capsid-membrane interactions and viral budding, three tyrosine residues (11, 28, and 67), oriented toward the MA core, were replaced individually or in a pair-wise combination with the more hydrophobic phenylalanine residue(s). As a control, Tyr82, oriented toward the outer surface of MA, was also replaced with phenylalanine. These Tyr-to-Phe substitutions did not alter capsid assembly compared to wild type in a capsid assembly assay. Pulse-chase, immunofluorescence, and electron microscopy studies demonstrated that single substitutions of Tyr11, Tyr28, and Tyr67 recapitulated the T41I/T78I mutant phenotype of decreased budding kinetics and accumulation of capsids at the plasma membrane. MA double mutants with a combination of these Tyr substitutions exhibited a phenotype that was even more defective in budding. In contrast, MA mutants with Tyr82 replaced by Phe resulted in a transport-defective phenotype. These results strongly support the hypothesis that myristic acid is sequestered inside MA prior to capsid-membrane interactions.
θ Defensins Protect Cells from Infection by Herpes Simplex Virus by Inhibiting Viral Adhesion and Entry
Authors: Yasin Bushra , Wang Wei , Pang Mabel , Cheshenko Natalia , Hong Teresa , Waring Alan J. , Herold Betsy C. , Wagar Elizabeth A. , Lehrer Robert I. 
Published: April 2004

ABSTRACTWe tested the ability of 20 synthetic θ defensins to protect cells from infection by type 1 and type 2 herpes simplex viruses (HSV-1 and -2, respectively). The peptides included rhesus θ defensins (RTDs) 1 to 3, originally isolated from rhesus macaque leukocytes, and three peptides (retrocyclins 1 to 3) whose sequences were inferred from human θ-defensin (DEFT) pseudogenes. We also tested 14 retrocyclin analogues, including the retro, enantio, and retroenantio forms of retrocyclin 1. Retrocyclins 1 and 2 and RTD 3 protected cervical epithelial cells from infection by both HSV serotypes, but only retrocyclin 2 did so without causing cytotoxicity or requiring preincubation with the virus. Surface plasmon resonance studies revealed that retrocyclin 2 bound to immobilized HSV-2 glycoprotein B (gB2) with high affinity (Kd, 13.3 nM) and that it did not bind to enzymatically deglycosylated gB2. Temperature shift experiments indicated that retrocyclin 2 and human α defensins human neutrophil peptide 1 (HNP 1) to HNP 3 protected human cells from HSV-2 by different mechanisms. Retrocyclin 2 blocked viral attachment, and its addition during the binding or penetration phases of HSV-2 infection markedly diminished nuclear translocation of VP16 and expression of ICP4. In contrast, HNPs 1 to 3 had little effect on binding but reduced both VP16 transport and ICP4 expression if added during the postbinding (penetration) period. We recently reported that θ defensins are miniature lectins that bind gp120 of human immunodeficiency virus type 1 (HIV-1) with high affinity and inhibit the entry of R5 and X4 isolates of HIV-1. Given its small size (18 residues), minimal cytotoxicity, lack of activity against vaginal lactobacilli, and effectiveness against both HSV-2 and HIV-1, retrocyclin 2 provides an intriguing prototype for future topical microbicide development.
Human Immunodeficiency Virus Type 1 Activates Plasmacytoid Dendritic Cells and Concomitantly Induces the Bystander Maturation of Myeloid Dendritic Cells
Authors: Fonteneau Jean-François , Larsson Marie , Beignon Anne-Sophie , McKenna Kelli , Dasilva Ida , Amara Ali , Liu Yong-Jun , Lifson Jeffrey D. , Littman Dan R. , Bhardwaj Nina 
Published: April 2004

ABSTRACTIn this study, we analyzed the phenotypic and physiological consequences of the interaction of plasmacytoid dendritic cells (pDCs) with human immunodeficiency virus type 1 (HIV-1). pDCs are one cellular target of HIV-1 and respond to the virus by producing alpha/beta interferon (IFN-α/β) and chemokines. The outcome of this interaction, notably on the function of bystander myeloid DC (CD11c+DCs), remains unclear. We therefore evaluated the effects of HIV-1 exposure on these two DC subsets under various conditions. Blood-purified pDCs and CD11c+DCs were exposed in vitro to HIV-1, after which maturation markers, cytokine production, migratory capacity, and CD4 T-cell stimulatory capacity were analyzed. pDCs exposed to different strains of infectious or even chemically inactivated, nonreplicating HIV-1 strongly upregulated the expression of maturation markers, such as CD83 and functional CCR7, analogous to exposure to R-848, a synthetic agonist of toll-like receptor-7 and -8. In addition, HIV-1-activated pDCs produced cytokines (IFN-α and tumor necrosis factor alpha), migrated in response to CCL19 and, in coculture, matured CD11c+DCs, which are not directly activated by HIV. pDCs also acquired the ability to stimulate naïve CD4+T cells, albeit less efficiently than CD11c+DCs. This HIV-1-induced maturation of both DC subsets may explain their disappearance from the blood of patients with high viral loads and may have important consequences on HIV-1 cellular transmission and HIV-1-specific T-cell responses.
Analysis of N-Linked Glycosylation of Hantaan Virus Glycoproteins and the Role of Oligosaccharide Side Chains in Protein Folding and Intracellular Trafficking
Authors: Shi Xiaohong , Elliott Richard M. 
Published: April 2004

ABSTRACT

The membrane glycoproteins Gn and Gc of Hantaan virus (HTNV) (family
Bunyaviridae
) are modified by N-linked glycosylation. The glycoproteins contain six potential sites for the attachment of N-linked oligosaccharides, five sites on Gn and one on Gc. The properties of the N-linked oligosaccharide chains were analyzed by treatment with endoglycosidase H, peptide:
N
-glycosidase F, tunicamycin, and deoxynojirimycin and were confirmed to be completely of the high-mannose type. Ten glycoprotein gene mutants were constructed by site-directed mutagenesis, including six single N glycosylation site mutants and four double-site mutants. We determined that four sites (N134, -235, -347, and -399) on Gn and the only site (N928) on Gc in their ectodomains are utilized, whereas the fifth site on Gn (N609), which faces the cytoplasm, is not glycosylated. The importance of individual N-oligosaccharide chains varied with respect to folding and intracellular transport. The oligosaccharide chain on residue N134 was found to be crucial for protein folding, whereas single mutations at the other glycosylation sites were better tolerated. Mutation at glycosylation sites N235 and N399 together resulted in Gn misfolding. The endoplasmic reticulum chaperones calnexin and calreticulin were found to be involved in HTNV glycoprotein folding. Our data demonstrate that N-linked glycosylation of HTNV glycoproteins plays important and differential roles in protein folding and intracellular trafficking.
CD4-Induced T-20 Binding to Human Immunodeficiency Virus Type 1 gp120 Blocks Interaction with the CXCR4 Coreceptor
Authors: Yuan Wen , Craig Stewart , Si Zhihai , Farzan Michael , Sodroski Joseph 
Published: April 2004

ABSTRACT
The synthetic peptide T-20, which corresponds to a sequence within the C-terminal heptad repeat region (HR2) of the human immunodeficiency virus type 1 (HIV-1) gp41 envelope glycoprotein, potently inhibits viral membrane fusion and entry. Although T-20 is thought to bind the N-terminal heptad repeat region (HR1) of gp41 and interfere with gp41 conformational changes required for membrane fusion, coreceptor specificity determined by the V3 loop of gp120 strongly influences the sensitivity of HIV-1 variants to T-20. Here, we show that T-20 binds to the gp120 glycoproteins of HIV-1 isolates that utilize CXCR4 as a coreceptor in a manner determined by the sequences of the gp120 V3 loop. T-20 binding to gp120 was enhanced in the presence of soluble CD4. Analysis of T-20 binding to gp120 mutants with variable loop deletions and the reciprocal competition of T-20 and particular anti-gp120 antibodies suggested that T-20 interacts with a gp120 region near the base of the V3 loop. Consistent with the involvement of this region in coreceptor binding, T-20 was able to block the interaction of gp120-CD4 complexes with the CXCR4 coreceptor. These results help to explain the increased sensitivity of CXCR4-specific HIV-1 isolates to the T-20 peptide. Interactions between the gp41 HR2 region and coreceptor-binding regions of gp120 may also play a role in the function of the HIV-1 envelope glycoproteins.
Comparison of the Rta/Orf50 Transactivator Proteins of Gamma-2-Herpesviruses
Authors: Damania Blossom , Jeong Joseph H. , Bowser Brian S. , DeWire Scott M. , Staudt Michelle R. , Dittmer Dirk P. 
Published: April 2004

ABSTRACT
The viral immediate-early transactivator Rta/Orf50 is necessary and sufficient to initiate Kaposi's sarcoma-associated herpesvirus/human herpesvirus 8 (KSHV/HHV-8) reactivation from latently infected cells. Since Rta/Orf50 is conserved among all known gamma-2-herpesviruses, we investigated whether the murine gamma-68-herpesvirus (MHV-68) and rhesus monkey rhadinovirus (RRV) homologs can functionally substitute for KSHV Rta/Orf50. (i) Our comparison of 12 KSHV promoters showed that most responded to all three Rta/Orf50proteins, but three promoters (vGPCR, K8, and gB) responded only to the KSHV Rta/Orf50 transactivator. Overall, the activation of KSHV promoters was higher with KSHV Rta than with the RRV and MHV-68 Rta. (ii) Only the primate Rta/Orf50 homologs were able to interfere with human p53-depedent transcriptional activation. (iii) Transcriptional profiling showed that the KSHV Rta/Orf50 was more efficient than it's homologs in inducing KSHV lytic transcription from the latent state. These results suggest that the core functionality of Rta/Orf50 is conserved and independent of its host, but the human protein has evolved additional, human-specific capabilities.