bluuebunny/crossref_metadata_2025_split huggingface dataset:
Melamine‐formaldehyde resins: I. An examination of some model compound systems
Authors: Anderson I. H. , Cawley M. , Steedman W. 
Published: March 2007

AbstractThe possible course of methylotation and subsequent crosslinking steps in melamine‐formaldehyde resins has been investigated by using two model compound systems, viz., 2‐amino‐4, 6‐diphenoxy‐s‐triazine and 2‐amino‐4, 6‐diphenyl‐s‐triazine. The reactions of these models with formaldehyde and the secondary thermally induced condensation reactions have been examined, in particular, by the use of thin‐layer chromatography and by nuclear magnetic resonance and infra‐red spectroscopy. Methylolated products crosslink by forming ether and methylene bridges at ∼120°, the former being readily converted to the latter when the temperature is varied to ∼135°. Ether bridge degradation releases formaldehyde which further reacts in part at available N—H sites. The conversion of ether bridges to methylene bridges is enhanced by the attachment of phenyl groups to the triazine ring.
Wax crosslinking with dicumyl peroxide
Authors: Brink A. , Dressler F. 
Published: March 2007

AbstractA Fischer—Tropsch paraffin wax of high molecular weight, congealing point 205°F (96·1°C), was crosslinked with dicumyl peroxide as initiator. At peroxide/wax molar ratios of less than 1·15 : 1, crosslinked waxes with molecular weights up to approximately double that of the starting material are obtained. These products are characterised by an increase in elasticity. At peroxide/wax ratios greater than 1·15 : 1 insoluble and infusible gels are formed. The efficiency and fate of the initiator and possible side reactions are discussed.
Liquid‐induced crystallisation of polymers
Authors: Kashmiri M. I. , Sheldon R. P. 
Published: March 2007

AbstractIn addition to the more conventional methods for promoting the crystallisation of polymers, treatment with certain organic liquids has been found to be effective. In previous work it has been shown that the mechanism of this process is a diffusion‐controlled one and that for thin films of polyethylene terephthalate, the crystallisation is completed by the development of opacity after a well‐defined induction time.After a survey of possible methods it has been shown that an infra‐red technique is the most suitable for measuring the change in crystallinity, although doubt exists as to the reliability of the calculated magnitude of degrees of crystallinity. A comparison has been made between diffusion data and induction times and fair correlation is found to exist between log (diffusion coefficient) and induction time.
Structural information from the light scattered by solutions subjected to electric fields
Authors: Jennings B. R. 
Published: March 2007

AbstractMeasurements of the intensity of the light scattered from polymer solutions lead to information about geometric parameters such as the molecular weight and radius of gyration of the solute. The intensity changes when an electric field is applied to the solutions, owing to the resulting orientation, deformation and alignment of the polymer molecules. Measurements of these intensity changes lead to the evaluation of such physical parameters as the permanent and induced dipole moments and the relaxation time of the particles.The theory of the effect is outlined briefly for rigid rod‐like and for flexible randomly coiled molecules. Two attractive aspects of the theory are that, in favourable circumstances, some measures of both the solute flexibility and polydispersity are obtainable in addition to the determination of the electrical properties of the polymer. Details of the inexpensive and straightforward modification and operation of an existing photoelectric photometer are mentioned.Representative results are given for three systems. Aqueous dispersions of the needle‐like clay mineral attapulgite illustrate the abundance of molecular information obtainable by the method. Results for polybenzyl glutamate in the helix‐promoting solvent dichlorethane, demonstrate how an appraisal of the α‐helical configuration can be made in terms of the molecular length and dipole moment. Finally, results for polyproline show that, even with poorly characterised samples, useful qualitative information is still readily available. In this case, the molecular flexibility and dipolar nature were clearly shown.
Correlation of dielectric and visco‐elastic relaxation in polymer solutions
Authors: North A. M. , Phillips P. J. 
Published: March 2007

AbstractThe interpretation of studies of dielectric relaxation in polymers is often restricted by ignorance of the mode of motion responsible for dipole orientation in an applied field. Relevant information can be drawn from studies of visco‐elastic relaxation, since the visco‐elastic relaxation time is comparable with the dielectric relaxation time when the latter requires some ‘whole molecule’ mode of motion involving simultaneous movement of many chain segments. The dielectric and visco‐elastic relaxation times are expected to differ when the former involves a localised segmental motion.The dielectric relaxation process is shown to involve a localised segmental motion in acrylic polymers, but involves a ‘whole molecule’ rotation in low molecular weight poly(N‐vinylcarbazole). Poly(p‐substituted phenyl acetylenes) exhibit two dielectric relaxation processes. A low frequency relaxation comparable with the visco‐elastic relaxation is ascribed to the backbone double bonds being polarised unidirectionally along the chain, and a high frequency process is ascribed to a localised segmental motion of the substituted phenyl moiety.
Azodiisobutyronitrile as initiator in emulsion polymerisation
Authors: Gulbekian E. V. 
Published: March 2007

AbstractThe solubility of azodiisobutyronitrile (AZDN), which is used as an initiator in emulsion polymerisation was measured in an aqueous phase containing a dissolved monomer and a surfactant. The results show that AZDN solubility is enhanced in the presence of dissolved monomer but that the surfactant alone has no appreciable effect.
Influence of chemical structure on the morphology and physical properties of crosslinked macromolecules synthesised by polyaddition reaction
Authors: Lohse F. , Schmid R. , Batzer H. , Fisch W. 
Published: March 2007

AbstractBy reacting acid polyesters with di‐epoxides and crosslinking them with anhydrides it was possible to increase the energy of deformation in the transition range by a factor of 10, compared with the conventional highly crosslinked epoxy resins.A further increase in toughness could be realised by introducing hydrogen bonds, e.g. urethane groups along the chains of the polymers. The syntheses of epoxy resins containing urethane groups are described. The physical properties of the crosslinked systems caused by different densities of the crosslinks are demonstrated and discussed.
Synthesis of polymer particles possessing radical initiating sites on the surface by emulsion copolymerization and construction of core–shell structures by a photoinduced atom transfer radical polymerization approach
Authors: Ishizu Koji , Kobayakawa Naoyuki , Takano Satoshi , Tokuno Yoko , Ozawa Masaaki 
Published: March 2007

AbstractThe crosslinked polystyrene particles possessing photofunctional N,N‐diethyldithiocarbamate groups on their surface were prepared by free‐radical emulsion copolymerization of a mixture of styrene, divinylbenzene and 4‐vinylbenzyl N,N‐diethyldithiocarbamate with redox system as an initiator under UV irradiation. In this copolymerization, the inimer 4‐vinylbenzyl N,N‐diethyldithiocarbamate acted the formation of hyperbranched structures by living radical photopolymerization. The particle sizes (number‐average particle diameter = 214–523 nm) were controlled by varying the feed amount of surfactant and size distributions were relatively narrow. Subsequently, core–shell particles were synthesized by photoinduced atom transfer radical polymerization approach of methyl methacrylate initiated by photofunctional polystyrene particles as a macroinitiator. Such core–shell particles were stabilized sterically by grafted chains in organic solvents. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1771–1777, 2007
Aqueous solution and solid state interactions of lanthanide ions with a methacrylic ester polymer bearing pendant 15‐crown‐5 moieties
Authors: Rubio F. , García F. , Burrows H. D. , Pais A. A. C. C. , Valente A. J. M. , Tapia M. J. , García J. M. 
Published: March 2007

AbstractThe interaction between trivalent lanthanide ions and poly(1,4,7,10,13‐pentaoxacyclopentadecan‐2‐yl‐methyl methacrylate), PCR5, in aqueous solution and in the solid state have been studied. In aqueous solution, evidence of a weak interaction between the lanthanides and PCR5 comes from the small red shift of the Ce(III) emission spectra and the slight broadening of the Gd(III) EPR spectra. From the Tb(III) lifetimes in the presence of H2O and D2O the loss of one or two water coordinated molecules is confirmed when Tb(III) is bound to PCR5. An association constant of the order of 200 M−1 was obtained for a 1:1 (lanthanide:15‐crown‐5) complex from the shift of the polymer NMR signals induced by Tb(III). A similar association constant is obtained from the differences of the molar conductivity of Ce(III) solution at various concentrations in presence and absence of PCR5. When Tb(III) is adsorbed on PCR5 membranes, lifetime experiments in H2O and D2O confirm the loss of 5 or 6 water coordinated molecules indicating that in solid state the lanthanide(III)‐PCR5 interaction is stronger than in solution. The adsorption of Ce(III) in PCR5 membranes shows a Langmuir type isotherm, from which an equilibrium constant of 39 M−1 has been calculated. SEM shows that the membrane morphology is not much affected by lanthanide adsorption. Support for lanthanide ion–crown interactions comes from ab initio calculations on 15‐crown‐5/La(III) complex. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1788–1799, 2007
Overexpression of protease‐activated receptors‐1,‐2, and‐4 (PAR‐1, ‐2, and ‐4) in prostate cancer
Authors: Black Peter C. , Mize Gregory J. , Karlin Peter , Greenberg Daniel L. , Hawley Sarah J. , True Lawrence D. , Vessella Robert L. , Takayama Thomas K. 
Published: March 2007

AbstractBACKGROUNDAlthough protease‐activated receptors (PARs) have been described to play a role in different malignancies, their expression and biological activity in prostate cancer are mostly unknown.METHODSPAR expression in radical prostatectomy specimens was investigated by immunohistochemistry (IHC, 40 patients) and RT‐PCR. Their role in LNCaP prostate cancer cell migration and Rac1/Cdc42 signaling was assessed with Boyden chamber analysis and Western blot, respectively.RESULTSPAR mRNA expression was higher in cancer, and protein expression was increased in PAR‐1 (45%), PAR‐2 (42%), and PAR‐4 (68%), compared to normal glands. Increased PAR‐1 (periglandular stroma) was associated with higher rates of biochemical recurrence (median follow‐up, 5 years;P = 0.006). LNCaP migration was enhanced twofold and Rac1/Cdc42 signaling was activated by stimulation of PAR‐1 and PAR‐2.CONCLUSIONSPARs are overexpressed in prostate cancer and may serve as potential predictors of recurrence. The data suggest potential role of PARs in autocrine and paracrine mechanisms of prostate cancer. Prostate 67: 743–756, 2007. © 2007 Wiley‐Liss, Inc.
Effects of steroidal and non‐steroidal antiandrogens on wild‐type and mutant androgen receptors
Authors: Urushibara Masayasu , Ishioka Junichiro , Hyochi Nobuhiko , Kihara Kazunori , Hara Shuntaro , Singh Pratap , Isaacs John T. , Kageyama Yukio 
Published: March 2007

AbstractBACKGROUNDMolecular basis for secondary antiandrogen therapy in prostate cancer with mutant androgen receptors (ARs) is not fully elucidated.MATERIALS AND METHODSEffects of steroidal and non‐steroidal antiandrogens on transcriptional activities of wild‐type and mutant (W741C, T877A, and W741C+T877A) ARs were measured. Crystal structure analysis and docking studies were performed using Molecular Operating Environment (MOE) package.RESULTSDHT‐induced transcriptional activity of the T877A mutant and the W741C mutant was suppressed by bicalutamide and hydroxyflutamide, respectively. Nilutamide suppressed the W741C mutant and the double mutant. Cyproterone acetate modestly inhibited the W741C mutant and the double mutant. The structural studies suggested that nilutamide and cyproterone acetate retain their antiandrogenic properties against both the W741C mutant and the double mutant due to fact that mutation W741C does not permit formation of key hydrophobic interaction between ligand and AR ligand binding domain, which is necessary for their conversion into agonists.CONCLUSIONSSwitching antiandrogens may be reasonable in prostate cancer with mutant ARs. Prostate 67: 799–807, 2007. © 2007 Wiley‐Liss, Inc.
Prospective diagnostic efficiency of biopsy washing DNA GSTP1 island hypermethylation for detection of adenocarcinoma of the prostate
Authors: Eilers Tyark , Machtens Stefan , Tezval Hossein , Blaue Christoph , Lichtinghagen Ralf , Hagemann Jörn , Jonas Udo , Serth Jürgen 
Published: March 2007

AbstractBACKGROUNDThe prospective diagnostic efficiency of quantitative glutathione S transferase (GSTP1) promoter hypermethylation analysis in biopsy washing samples has not been determined so far.METHODSBiopsies were obtained prospectively from 86 patients suspicious for prostate cancer (CaP). After isolation of DNA from biopsy washings and bisulfite conversion methylated and unmethylated GSTP1 sequences were specifically quantitated by real‐time fluorescence PCR. Relative degrees of methylation were compared to results of histopathological examination.RESULTSIncreased relative methylation was found for the CaP group (mean 28.1%) compared to biopsies without histological evidence for malignancy (5.2%; P < 0.001). A sensitivity and specificity of 92% and 86% and positive and negative predictive values of 82% and 94% were obtained. Receiver operating characteristic (ROC) analysis demonstrated a value of 0.90 (95% CI 0.82–0.98) for the area under curve (AUC).CONCLUSIONSBiopsy washing DNA GSTP1 hypermethylation analysis demonstrates a high diagnostic efficacy which is comparable to the retrospective analysis of biopsy tissue specimens. Moreover it is compatible with routine biopsy examination thus permitting further prospective evaluation in CaP diagnosis. Prostate 67: 757–763, 2007. © 2007 Wiley‐Liss, Inc.
Interleukin‐6 undergoes transition from growth inhibitor associated with neuroendocrine differentiation to stimulator accompanied by androgen receptor activation during LNCaP prostate cancer cell progression
Authors: Lee Soo Ok , Chun Jae Yeon , Nadiminty Nagalakshmi , Lou Wei , Gao Allen C. 
Published: March 2007

AbstractBACKGROUNDInterleukin‐6 (IL‐6) has been implicated in the modulation of growth and differentiation in many cancers, and is associated with poor prognosis in renal cell carcinoma, ovarian cancer, lymphoma, melanoma, and prostate cancer. The effects of IL‐6 on the growth of LNCaP human prostate cancer cells are puzzling with some groups showing growth stimulation, while others showing growth inhibition. In this study, we investigated the discrepancy of the effects of IL‐6 on prostate cancer cells.METHODSSeries of lower and higher passages of LNCaP cell sublines were generated by a long‐term exposure of LNCaP cells in IL‐6‐containing culture media. The characteristics of these cell sublines were analyzed and the potential roles of neuroendocrine (NE) differentiation and androgen receptor (AR) activation were examined.RESULTSWe demonstrated that while short‐term treatment of IL‐6 inhibits LNCaP cell growth by a paracrine mechanism associated with NE differentiation, long‐term treatment of IL‐6 promotes LNCaP cell growth by an autocrine mechanism accompanied by an activation of AR signaling. In the lower passages (less than 28 passages) of LNCaP cells treated with IL‐6, the cell growth was severely retarded which is associated with NE‐like morphology and increased expression of NE markers such as neuronspecific enolase (NSE) and chromgranin A (ChgA), and loss of AR expression. However, in the higher passages (higher than 42 passages) of LNCaP cells treated with IL‐6, cells started to express endogenous IL‐6. At the same time, NE characteristics were disappeared, AR signaling was activated and cells growth was accelerated. Knocking down the AR activation of the higher passages of LNCaP cells abolished autocrine IL‐6‐induced growth stimulation.CONCLUSIONSThese studies suggest that acquisition of endogenous IL‐6 production after prolong exposure of prostate cancer cells to IL‐6 may contribute to an autocrine cell growth stimulation. Furthermore, the transition of IL‐6 from a paracrine growth inhibitor to an autocrine growth stimulator suggests that IL‐6 plays an important role during prostate cancer progression, possibly androgen‐independent progression. Prostate 67: 764–773, 2007. © 2007 Wiley‐Liss, Inc.
Toll like receptor‐9 agonists stimulate prostate cancer invasion in vitro
Authors: Ilvesaro Joanna M. , Merrell Melinda A. , Swain Telisha Millender , Davidson Jennifer , Zayzafoon Majd , Harris Kevin W. , Selander Katri S. 
Published: March 2007

AbstractBACKGROUNDToll‐like receptor 9 (TLR9) recognizes microbial DNA. In addition to immune cells, TLR9 expression has been detected in various cancer cells. We showed recently that TLR9 agonistic CpG‐oligonucleotides (CpG‐ODNs) induce matrix metalloproteinase‐13 (MMP‐13)‐mediated invasion in TLR9‐expressing (TLR9+) breast cancer cells. We investigated here TLR9 expression and function in human prostate cancer (CaP) cells.METHODSTLR9 expression was detected with Western blotting and immunohistochemistry. Invasion was studied with Matrigel‐assays. MMP‐13 was assayed with ELISA.RESULTSHuman CaP cell lines and clinical samples exhibit various levels of TLR9 expression. Treatment of TLR9+, but not TLR9− CaP cells with CpG‐ODNs or bacterial DNA increased their invasion, which was inhibited with chloroquine. CpG‐ODN‐treatment also increased MMP‐13 activity and neutralizing anti‐MMP‐13 antibody prevented CpG‐ODN‐induced invasion in TLR9+ CaP cells. Estradiol up‐regulated TLR9 expression in LnCaP cells.CONCLUSIONSTLR9‐mediated invasion may represent a novel mechanism through which infections promote prostate cancer. Prostate 67: 774–781, 2007. © 2007 Wiley‐Liss, Inc.
Preferential chemosensitization of PTEN‐mutated prostate cells by silencing the Akt kinase
Authors: Priulla Marcella , Calastretti Angela , Bruno Paola , Amalia Azzariti , Paradiso Angelo , Canti Gianfranco , Nicolin Angelo 
Published: March 2007

AbstractBACKGROUNDIn prostate cancer, mutations of the phosphatase PTEN can activate the kinase cascade PI3K/Akt/mTOR which induces drug resistance.METHODSChemosensitization by siRNA targeting Akt was studied in HEK293 cells forced to express CA‐Akt or kinase‐dead DN‐Akt. To decrease drug resistance, Akt was silenced with siRNA in human prostate DU‐145 cell line expressing the normal PTEN or in LNCaP and PC3 cell lines expressing mutated‐PTEN. Taxol was used for the chemosensitization studies.RESULTSSilencing Akt in the drug‐resistant CA‐Akt cells efficiently sensitized cells to antitubule agents, whereas silencing drug‐responsive DN‐Akt cells did not. Only minor effects were obtained in wild‐type HEK293 cells. Potentiation by siRNA of taxol cytotoxicity was significantly greater in mutated‐PTEN cells than in prostate cells expressing wild‐type PTEN. The apoptotic program induced by taxol was preferentially potentiated by Akt siRNA in PTEN‐mutated cell lines as regards the DU‐145 cell line.CONCLUSIONSSilencing Akt in PTEN‐mutated prostate cancer cells enhances the antitumor effects of taxol. No siRNA chemosensitization was obtained in prostate cells with wild type PTEN. Prostate 67: 782–789, 2007. © 2007 Wiley‐Liss, Inc.
High resolution structure of streptavidin in complex with a novel high affinity peptide tag mimicking the biotin binding motif
Authors: Perbandt M. , Bruns O. , Vallazza M. , Lamla T. , Betzel Ch. , Erdmann V.A. 
Published: March 2007

AbstractA novel peptide was designed which possesses nanomolar affinity of less than 20 nM for streptavidin. Therefore it was termed Nano‐tag and has been used as an affinity tag for recombinant proteins. The minimized version of the wild type Nano‐tag is a seven‐amino acid peptide with the sequence fMDVEAWL. The three‐dimensional structure of wild type streptavidin in complex with the minimized Nano‐tag was analyzed at atomic resolution of 1.15 Å and the details of the binding motif were investigated. The peptide recognizes the same pocket of streptavidin where the natural ligand biotin is bound, but the peptide requires significantly more space than biotin. Therefore the binding loop adopts an “open” conformation in order to release additional space for the peptide. The conformation of the bound Nano‐tag corresponds to a 310 helix. However, the analysis of the intermolecular interactions of the Nano‐tag with residues of the binding pocket of streptavidin reveals astonishing similarities to the biotin binding motif. In principle the three‐dimensional conformation of the Nano‐tag mimics the binding mode of biotin. Our results explain why the use of the Nano‐tag in fusion with recombinant proteins is restricted to their N‐terminus and we describe the special significance of the fMet residue for the high affinity binding mode. Proteins 2007. © 2007 Wiley‐Liss, Inc.
Attempt to simplify the amino‐acid sequence of photoactive yellow protein with a set of simple rules
Authors: Shirai Kumiko , Yamazaki Yoichi , Kamikubo Hironari , Imamoto Yasushi , Kataoka Mikio 
Published: March 2007

AbstractTo understand the information encoded in an amino‐acid sequence, the authors have attempted to simplify the amino‐acid sequence of photoactive yellow protein (PYP) with a set of simple rules. The rules are designed to reduce overlapping structural information. The simplified PYP protein, which was composed of only nine species of amino acids (Ser, Val, Asp, Lys, Phe, Met, Gly, Pro, and Cys), took a completely different structure than the native conformation. Even after the evolutionarily conserved residues were restored in the simplified protein, the PYP variant did not properly fold, indicating that the information encoded in the conserved residues is insufficient for the structure formation. Additional restorations of the substituted hydrophilic or hydrophobic residues did not lead to a variant that formed the native structure. The structural properties of these variants and the wild‐type protein in aqueous solution differed. Partial simplification was successfully performed by creating chimeric proteins composed of combinations of wild‐type PYP and sPYPIII. The structural characterization of each chimeric protein indicates that the important information on the structure formation is encoded in the β‐scaffold region. Proteins 2007. © 2007 Wiley‐Liss, Inc.