bluuebunny/crossref_metadata_2025_split huggingface dataset:
Implications of galactocerebrosidase and galactosylcerebroside metabolism in cancer cells
Authors: Beier Ulf Henning , Görögh Tibor 
Published: January 2005

AbstractGalactosylcerebroside is known to be overexpressed upon the cellular surface of a variety of cancers. In squamous cell carcinomas of the head and neck, one explanation for galactosylcerebroside accumulation has been identified as a transcriptional repression of the galactocerebrosidase gene. Galactocerebrosidase is the enzyme responsible for degrading galactosylcerebroside to ceramide. Ceramide is an important apoptosis activator, whereas galactosylcerebroside functions as an inhibitor. A shift of the ceramide metabolism balance in favor of glycosylated forms has been identified as a mechanism of drug resistance for several antineoplastic agents. Our review elaborates on possible explanations for galactocerebrosidase suppression and on other explanations for increased glycosphingolipid concentration within cancer cell membranes. Furthermore, conjecturable influences of a repressed galactocerebrosidase expression on tumor biology are to be explained. The inhibiting transcription factors YY1 and AP2 have been identified as potential galactocerebrosidase gene suppressors. The resulting accumulation of galactosylcerebroside promotes a reduction of cellular adhesion and inhibits apoptosis, leading to increased cellular growth, migration and prolonged cell survival contributing to carcinogenesis. © 2005 Wiley‐Liss, Inc.
Procoagulant phenotype of endothelial cells after coculture with biomaterial‐treated blood cells
Authors: Rose Stacey L. , Babensee Julia E. 
Published: January 2005

AbstractUnderstanding endothelial cell (EC)/blood/biomaterial interactions is crucial for the advancement of cardiovascular devices that often fail because of the lack of nonthrombogenic biomaterials. To begin to assess these interactions, a static EC/blood cell/biomaterial model was used. Isolated blood cells were pretreated with model biomaterial beads with different surface chemistries: polystyrene (PS), and PS beads grafted with 3‐kDa polyethylene glycol (PEG) with either a hydroxyl (PS‐PEG‐OH) or amine (PS‐PEG‐NH2) terminal group at 5.4 or 54 × 104 beads/mL. Biomaterial‐treated monocytes, neutrophils, or platelets were applied to human umbilical vein ECs (HUVECs) for 5 or 24 h of static coculture, and the resultant procoagulant HUVEC phenotype was characterized using several methods. Flow cytometry was used to assess surface expression of tissue factor (TF), adenosine triphosphate diphosphohydrolase, phosphatidylserine, and thrombomodulin, a functional TF assay was used to assess TF activity, and a plasma recalcification assay examined clotting times on HUVECs. Static coculture of HUVEC with biomaterial‐treated neutrophils induced a procoagulant phenotype as exemplified by upregulation of TF expression and total functional activity, and downregulation of adenosine triphosphate diphosphohydrolase and thrombomodulin expression. The plasma recalcification assay demonstrated that HUVECs cocultured with biomaterial‐treated monocytes significantly shortened clotting times, with some effect of similarly treated neutrophils. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res 72A: 269–278, 2005
Flow perfusion culture induces the osteoblastic differentiation of marrow stromal cell‐scaffold constructs in the absence of dexamethasone
Authors: Holtorf Heidi L. , Jansen John A. , Mikos Antonios G. 
Published: January 2005

AbstractFlow perfusion culture of scaffold/cell constructs has been shown to enhance the osteoblastic differentiation of rat bone marrow stromal cells (MSCs) over static culture in the presence of osteogenic supplements including dexamethasone. Although dexamethasone is known to be a powerful induction agent of osteoblast differentiation in MSCs, we hypothesized that the mechanical shear force caused by fluid flow in a flow perfusion bioreactor would be sufficient to induce osteoblast differentiation in the absence of dexamethasone. In this study, we examined the ability of MSCs seeded on titanium fiber mesh scaffolds to differentiate into osteoblasts in a flow perfusion bioreactor in both the presence and absence of dexamethasone. Scaffold/cell constructs were cultured for 8 or 16 days and osteoblastic differentiation was determined by analyzing the constructs for cellularity, alkaline phosphatase activity, and calcium content as well as media samples for osteopontin. For scaffold/cell constructs cultured under flow perfusion, there was greater scaffold cellularity, alkaline phosphatase activity, osteopontin secretion, and calcium deposition compared with static controls, even in the absence of dexamethasone. When dexamethasone was present in the cell culture medium under flow perfusion conditions, there was further enhancement of osteogenic differentiation as evidenced by lower scaffold cellularity, greater osteopontin secretion, and greater calcium deposition. These results suggest that flow perfusion culture alone induces osteogenic differentiation of rat MSCs and that there is a synergistic effect of enhanced osteogenic differentiation when both dexamethasone and flow perfusion culture are used. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res 72A: 326–334, 2005
CLN3, the protein associated with batten disease: Structure, function and localization
Authors: Phillips Seasson N. , Benedict Jared W. , Weimer Jill M. , Pearce David A. 
Published: January 2005

AbstractBatten disease, an inherited neurodegenerative storage disease affecting children, results from the autosomal recessive inheritance of mutations in Cln3. The function of the CLN3 protein remains unknown. A key to understanding the pathology of this devastating disease will be to elucidate the function of CLN3 at the cellular level. CLN3 has proven difficult to study as it is predicted to be a membrane protein expressed at relatively low levels. This article is a critical review of various approaches used in examining the structure, trafficking, and localization of CLN3. We conclude that CLN3 is likely resident in the lysosomal/endosomal membrane. Different groups have postulated conflicting orientations for CLN3 within this membrane. In addition, CLN3 undergoes several posttranslational modifications and is trafficked through the endoplasmic reticulum and Golgi. Recent evidence also suggests that CLN3 traffics via the plasma membrane. Although the function of this protein remains elusive, it is apparent that genetic alterations in Cln3 may have a direct affect on lysosomal function. © 2005 Wiley‐Liss, Inc.
Chain‐End and Chain‐Internal Crosslinking in “Latent Reactive” Silicon Elastomers
Authors: Matloka Piotr P. , Sworen John C. , Zuluaga Fabio , Wagener Kenneth B. 
Published: January 2005

AbstractSummary: Latent reactivity has been employed to create processable elastomers constructed of carbosilane and either carbosiloxane or polyether segments. Two types of latent modes have been introduced: “chain‐internal” and “chain‐end” sites through the use of labile silicon methoxy and trifunctional olefinic functionalities. These latent reactive sites remain inert during formation of the linear copolymer; subsequent exposure to moisture triggers hydrolysis of the methoxy group and formation of a chemically crosslinked thermoset. These “chain‐end” sites limit the formation of dangling chains improving the overall mechanical properties of the material. The thermoset's mechanical response can be potentially varied from plastic to elastic behavior, depending on the ratio of hard and soft monomers employed. The concentration of “chain‐internal” and “chain‐end” crosslink sites enhances strength; modification to the run length and structure of the soft phase enhances elasticity, generating samples having moduli of 6 MPa, tensile strengths of 0.6 MPa and elongations of 400%.“Latent reactive” silicon elastomer.magnified image“Latent reactive” silicon elastomer.
Morphology and Phase Characteristics of High‐Density Polyethylene Probed by NMR Spin Diffusion and Second Moment Analysis
Authors: Lili Zhang , Chen Qun , Hansen Eddy W. 
Published: January 2005

AbstractSummary: A dipolar filter pulse sequence combined with cross‐polarization‐MAS is applied to characterize the phase distribution, morphology, and spin diffusion within a high‐density polyethylene sample. A new method to obtain quantitative 13C NMR by combining cross‐polarization‐MAS and spin diffusion NMR is presented. The derived crystallinity is consistent with the corresponding crystallinity obtained by 1H NMR.Illustration of the pulse sequence(s) applied in the present work.magnified imageIllustration of the pulse sequence(s) applied in the present work.
Poly(vinyl acetate)/Silver Nanocomposite Microspheres Prepared by Suspension Polymerization at Low Temperature
Authors: Yeum Jeong Hyun , Sun Qunhui , Deng Yulin 
Published: January 2005

AbstractSummary: High molecular weight (HMW) poly(vinyl acetate)/silver nanocomposite microspheres (PVAc/Ag), which are promising precursors of embolic materials with radiopacity, were prepared via a suspension polymerization approach in the presence of silver nanoparticles. It was found that a high yield and high molecular weight PVAc/Ag could be concurrently obtained even using a low‐temperature initiator 2,2′‐azobis(2,4‐dimethylvaleronitrile) (≈30 °C). In the case of presence of silver nanoparticles, the rate of polymerization was slightly slower than that without Ag. The suspension polymerization approach introduced could produce PVAc/Ag composite with conversion and viscosity‐average molecular weight ($\overline M _{\rm v}$) up to 95% and 1 300 000, respectively, in spite of the low polymerization temperature (≈30 °C), in sharp contrast with an only ≈30% conversion of VAc under bulk polymerization. Morphology studies revealed that except normal suspension microspheres with a smooth surface, a golf ball‐like appearance of the microspheres was observed, due to the migration and aggregating of the hydrophilic Ag nanoparticles at the sublayer beneath the microsphere's surface.
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The impact of water on photopolymerization kinetics of methacrylate/vinyl ether hybrid systems
Authors: Lin Yan , Stansbury Jeffrey W. 
Published: January 2005

AbstractReal‐time FT‐near infrared (NIR) spectroscopy was used to monitor individual monomer photopolymerization kinetics within the hybrid methacrylate/vinyl ether system composed of 2‐hydroxyethyl methacrylate and tri(ethylene glycol) methyl vinyl ether. Photoinitiation conditions have been manipulated to provide staged polymer formation of the selected hybrid systems. Significant differences were observed in the effect of water on hybrid systems with different polymerization sequence. The radical/cationic dual initiator system drastically decreased the effect of water on the vinyl ether polymerization. Even with significant water present, both the methacrylate and vinyl ether monomers can be effectively polymerized under certain initiation conditions. Copyright © 2005 John Wiley & Sons, Ltd.
Synthesis and characterization of bismaleimide‐polyetherimide‐silica hybrid by sol‐gel process
Authors: Li Shanjun , Tian Junxiang , Gan Wenjun , Zhao Lin , Li Liang , Wang Jinchen 
Published: January 2005

AbstractA ternary hybrid of bismaleimide‐polyetherimide‐silica (BMI‐PEI‐SiO2) was synthesized by sol‐gel reaction and characterized by scanning electron microscopy (SEM), energy dispersive X‐ray analysis (EDX), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC).The results indicated that silica could be introduced into the blend of thermoplastic‐thermosetting system by sol‐gel reaction and dispersed uniformly as nanoparticles. The phase separation of BMI‐PEI was not affected apparently by the presence of silica. The coupling agent 3‐aminopropyl (triethoxy)silane was chosen to enhance the interaction between the polymer‐matrix and silica. Thermal properties and mechanical properties of the hybrids both were improved with increasing silica content. Copyright © 2005 John Wiley & Sons, Ltd.
Effect of filler and void content on mechanical properties of pultruded composite materials under shear loading
Authors: Park Jin Y. , Zureick Abdul‐Hamid 
Published: January 2005

AbstractThis paper presents the results of an analytical investigation aimed at examining the mechanical behavior of fiber‐reinforced polymer matrix materials containing nonhomogeneous constituents such as fine clay fillers under shear loading. Analytical formulae that account for the presence of inhomogeneities in the matrix materials were developed for estimating the extensional and in‐plane shear moduli and Poisson's ratio. The analytical results were compared with the properties obtained from experiments. For the experiments, the pultruded composites containing clay fillers and voids as well as glass fiber and vinylester resin were selected, analyzed, and tested under shear loading. The effects of presence of constituents on the mechanical properties of matrix materials were also investigated based on the obtained volume fraction of their constituents. POLYM. COMPOS., 26:181–192, 2005. © 2005 Society of Plastics Engineers
Determination of dynamic delamination toughness of a graphite‐fiber/epoxy composite using Hopkinson pressure bar
Authors: Wu Xiang‐Fa , Dzenis Yuris A. 
Published: January 2005

AbstractModified dynamic three‐point‐bending and compact shearing test configurations based on Hopkinson pressure bar (HPB) and crack detection gage (CDG) (Vishay Intertechnology, Inc) were used for the determination of the dynamic mode I and mode II delamination‐initiation toughness of a unidirectional graphite‐fiber/epoxy composite made of P7051S‐20Q‐1000 prepregs (Toray Composites America). The transient loading history was recorded precisely by the HPB installed with a high‐resolution digital oscilloscope, and the crack initiation and delay time were captured using the CDG. By means of dynamic finite‐element analysis (FEA) of the impact processes with the loading history and crack initiation time as input, the critical dynamic stress intensity factors (DSIFs) (KIDC/KIIDC) were extracted from numerical results of the crack opening displacements (CODs). Results show that under the present transient loadings, the KIDCvalue is about 80–90% of the static one, while the KIIDCvalue is nearly unchanged. Dynamic failure mechanisms of the composite specimens were evaluated by fractography using a scanning electron microscope (SEM). POLYM. COMPOS., 26:165–180, 2005. © 2005 Society of Plastics Engineers
Evaluation of starch‐PE multilayers: Processing and properties
Authors: Dole Patrice , Avérous Luc , Joly Catherine , Valle Guy Della , Bliard Christophe 
Published: January 2005

AbstractAdhesion tests performed on various plasticized starch‐polyethylene multi‐layer systems led to the selection of a suitable combination of polymers compatible with the starch‐based layer. The compatibility of starch and polyethylene was better achieved through maleic anhydride functionalized polyethylene (PEg) than chemically modifying starch. The PEg method proved efficient provided that the water content, and the plasticizer nature and contents of the starch layer were carefully chosen. Computed shear viscosity allowed us to select a suitable botanical origin of starch such that the interfacial instabilities of the coextrusion process were minimized. The use of a multilayer structure (PE/PEg/starch/PEg/PE) improved gas barrier properties at high relative humidity. The higher quantity of water sorbed by thermoplastic starch (as compared to EVOH) coupled with starch's specific water sorption isotherm lengthened the water equilibration time in the hydrophilic inner layer significantly. As a result the gas barrier properties of the starch based multiplayer systems were enhanced as compared to existing commercial multiplayer systems (PE/PEg/EVOH/PEg/PE). This specific “water‐buffering property” of the starch inner layer should prove useful in packaging applications of perishables with extended shelf life in environments of varying relative humidity. Polym. Eng. Sci. 45:217–224, 2005. © 2005 Society of Plastics Engineers.
Synthesis and characterization of polyamides containing octadecanedioic acid: Nylon‐2,18, nylon‐3,18, nylon‐4,18, nylon‐6,18, nylon‐8,18, nylon‐9,18, and nylon‐12,18
Authors: Bennett Carl , Mathias Lon J. 
Published: January 2005

AbstractHigh‐aliphatic‐content linear nylons were produced with an 18‐carbon diacid with diamines containing both odd and even methylene segments. The resulting polymers were characterized with viscosimetric, thermal, and spectroscopic techniques. Solid‐state 15N NMR was used to determine the nylon crystalline form present. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 936–945, 2005
Synthesis and copolymerization of fluorinated monomers bearing a reactive lateral group. XX. Copolymerization of vinylidene fluoride with 4‐bromo‐1,1,2‐trifluorobut‐1‐ene
Authors: Guiot J. , Néouze M.‐A. , Sauguet L. , Améduri B. , Boutevin B. 
Published: January 2005

AbstractThe radical copolymerization of vinylidene fluoride (VDF) with 4‐bromo‐1,1,2‐trifluorobut‐1‐ene (C4Br) was examined. This bromofluorinated alkene was synthesized in three steps, which started with the addition of bromine to chlorotrifluoroethylene. In contrast to the ethylenation of 1,1‐difluoro‐1,2‐dibromochlorethane, which failed, that of 2‐chloro‐1,1,2‐trifluoro‐1,2‐dibromoethane was optimized and led to 2‐chloro‐1,1,2‐trifluoro‐1,4‐dibromobutane. The kinetics of the copolymerization of VDF with this brominated monomer initiated by t‐butyl peroxypivalate led to an assessment of the reactivity ratios, rVDF = 0.96 ± 0.67 and rC4Br = 0.09 ± 0.63, at 50 °C. The suspension copolymerization was also carried out, and the chemical modifications of the resulting bromo‐containing poly(vinylidene fluoride)s were attempted and consisted mainly of elimination or nucleophilic substitution of the bromine. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 917–935, 2005
Ybiv from Escherichia coli K12 is a HAD phosphatase
Authors: Roberts Anne , Lee Seok‐Yong , McCullagh Emma , Silversmith Ruth E. , Wemmer David E. 
Published: January 2005

AbstractThe protein YbiV from Escherichia coli K12 MG1655 is a hypothetical protein with sequence homology to the haloacid dehalogenase (HAD) superfamily of proteins. Although numerous members of this family have been identified, the functions of few are known. Using the crystal structure, sequence analysis, and biochemical assays, we have characterized YbiV as a HAD phosphatase. The crystal structure of YbiV reveals a two‐domain protein, one with the characteristic HAD hydrolase fold, the other an inserted α/β fold. In an effort to understand the mechanism, we also solved and report the structures of YbiV in complex with beryllofluoride (BeF3−) and aluminum trifluoride (AlF3), which have been shown to mimic the phosphorylated intermediate and transition state for hydrolysis, respectively, in analogy to other HAD phosphatases. Analysis of the structures reveals the substrate‐binding cavity, which is hydrophilic in nature. Both structure and sequence homology indicate YbiV may be a sugar phosphatase, which is supported by biochemical assays that measured the release of free phosphate on a number of sugar‐like substrates. We also investigated available genomic and functional data in an effort to determine the physiological substrate. Proteins 2005. © 2005 Wiley‐Liss, Inc.
Properties of polyproline II, a secondary structure element implicated in protein–protein interactions
Authors: Cubellis M. V. , Caillez F. , Blundell T. L. , Lovell S. C. 
Published: January 2005

AbstractThe polyproline II (PPII) conformation of protein backbone is an important secondary structure type. It is unusual in that, due to steric constraints, its main‐chain hydrogen‐bond donors and acceptors cannot easily be satisfied. It is unable to make local hydrogen bonds, in a manner similar to that of α‐helices, and it cannot easily satisfy the hydrogen‐bonding potential of neighboring residues in polyproline conformation in a manner analogous to β‐strands. Here we describe an analysis of polyproline conformations using the HOMSTRAD database of structurally aligned proteins. This allows us not only to determine amino acid propensities from a much larger database than previously but also to investigate conservation of amino acids in polyproline conformations, and the conservation of the conformation itself. Although proline is common in polyproline helices, helices without proline represent 46% of the total. No other amino acid appears to be greatly preferred; glycine and aromatic amino acids have low propensities for PPII. Accordingly, the hydrogen‐bonding potential of PPII main‐chain is mainly satisfied by water molecules and by other parts of the main‐chain. Side‐chain to main‐chain interactions are mostly nonlocal. Interestingly, the increased number of nonsatisfied H‐bond donors and acceptors (as compared with α‐helices and β‐strands) makes PPII conformers well suited to take part in protein–protein interactions. Proteins 2005. © 2005 Wiley‐Liss, Inc.
Understanding the energetics of helical peptide orientation in membranes
Authors: Sengupta Durba , Meinhold Lars , Langosch Dieter , Ullmann G. Matthias , Smith Jeremy C. 
Published: January 2005

AbstractUnderstanding the energetic factors determining the positioning and orientation of single‐helical peptides in membranes is of fundamental interest in structural biology. Here, a simple 5‐slab continuum dielectric model for the membrane is examined that distinguishes between the solvent, headgroup, and core regions. An analytical solution for the electrostatic solvation of a single dipole and an all‐atom model of N‐methylacetamide are used to demonstrate the effect of the dielectric boundaries in the system on peptide dipole orientation. The dipole orientation energy is shown to dominate the electrostatic solvation energy of a polyalanine helix in the membrane. With an additional surface‐area‐dependent term to account for the cavity formation in the aqueous region, the continuum electrostatics description is used to examine several helical peptides, the atoms of which are explicitly represented with a molecular mechanics force field. The experimentally determined tilt angles of a number of peptides of alternating alanine and leucine residues, and of glycophorin and melittin, are accurately reproduced by the model. The factors determining the tilt angles and their fluctuations are analyzed. The tilt angles of the simpler peptides are found to increase approximately linearly with peptide length; this effect is also rationalized. The analysis and model presented here provide a step toward the prediction of helical membrane protein structure. Proteins 2005. © 2005 Wiley‐Liss, Inc.
The Protein Coil Library: A structural database of nonhelix, nonstrand fragments derived from the PDB
Authors: Fitzkee Nicholas C. , Fleming Patrick J. , Rose George D. 
Published: January 2005

AbstractApproximately half the structure of folded proteins is either α‐helix or β‐strand. We have developed a convenient repository of all remaining structure after these two regular secondary structure elements are removed. The Protein Coil Library (http://roselab.jhu.edu/coil/) allows rapid and comprehensive access to non‐α‐helix and non‐β‐strand fragments contained in the Protein Data Bank (PDB). The library contains both sequence and structure information together with calculated torsion angles for both the backbone and side chains. Several search options are implemented, including a query function that uses output from popular PDB‐culling servers directly. Additionally, several popular searches are stored and updated for immediate access. The library is a useful tool for exploring conformational propensities, turn motifs, and a recent model of the unfolded state. Proteins 2005. © 2005 Wiley‐Liss, Inc.