bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hierarchically organized micellization of thermoresponsive rod‐coil copolymers based on poly[oligo(ethylene glycol) methacrylate] and poly(ε‐caprolactone)
Authors: Luzón Mario , Corrales Teresa , Catalina Fernando , San Miguel Verónica , Ballesteros Carmen , Peinado Carmen 
Published: September 2010

AbstractA series of amphiphilic triblock copolymers, poly[oligo(ethylene glycol) methacrylate]x‐block‐poly(ε‐caprolactone)‐block‐poly[oligo(ethylene glycol) methacrylate]x, POEGMACo(x), were synthesized. Formation of hydrophobic domains as cores of the micelles was studied by fluorescence spectroscopy. The critical micelle concentrations in aqueous solution were found to be in the range of circa 10−6 M. A novel methodology by modulated temperature differential scanning calorimetry was developed to determine critical micelle temperature. A significant concentration dependence of cmt was found. Dynamic light scattering measurements showed a bidispersed size distribution. The micelles showed reversible dispersion/aggregation in response to temperature cycles with lower critical solution temperature between 75 and 85 °C. The interplay of the two hydrophobic and one thermoresponsive macromolecular chains offers the chance to more complex morphologies. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010
Multiarm star polymers with POSS at the periphery
Authors: Gungor Eda , Bilir Cigdem , Hizal Gurkan , Tunca Umit 
Published: September 2010

AbstractAzide end‐functionalized polyhedral oligomeric silsesquioxane (POSS‐N3) was incorporated into the periphery of well‐defined alkyne‐polystyrene50‐poly(divinyl benzene) (alkyne‐PS50‐polyDVB) and alkyne‐poly(tert‐butyl acrylate)43‐poly(divinyl benzene) (alkyne‐PtBA43‐polyDVB) multiarm star polymers via highly efficient azide‐alkyne click reaction, resulting in POSS‐PS50‐polyDVB and POSS‐PtBA43‐polyDVB multiarm star block copolymers respectively, in the solution of tetrahydrofuran/N,N‐dimethyl formamide, CuBr/N,N,N′,N″,N″‐pentamethyldiethylenetriamine (PMDETA) at room temperature for 24 h. Linear precursors and star polymers obtained in this study were characterized 1H NMR, gel permeation chromatography (GPC), and triple detection GPC (TD‐GPC). Absolute molecular weight, hydrodynamic radius, and intrinsic viscosity ([η]) values for all star polymers were determined by TD‐GPC. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010
Synthesis and properties of copolymers of methyl methacrylate with 2,3,4,5,6‐pentafluoro and 4‐trifluoromethyl 2,3,5,6‐tetrafluoro styrenes: An intrachain interaction between methyl ester and fluoro aromatic moieties
Authors: Lou Liping , Koike Yasuhiro , Okamoto Yoshiyuki 
Published: September 2010

Abstract2,3,4,5,6‐Pentafluoro and 4‐trifluoromethyl 2,3,5,6‐tetrafluoro styrenes were readily copolymerized with methyl methacrylate (MMA) by a free radical initiator. The copolymers were soluble in tetrahydrofuran and acetone. The films obtained were transparent and flexible. The glass transition temperatures (Tgs) of the copolymers were found positively deviated from the Gordon–Taylor equation. The positive deviation could be accounted for by dipole–dipole intrachain interaction between the methyl ester group of MMA and the highly fluorinated aromatic moiety, which resulted in a decrease in the segmental mobility of the polymer chains and the enhanced Tg values of the copolymers. The water absorption of PMMA was greatly decreased by copolymerization of MMA with the highly fluorinated styrenes. With as little as 10 mol % of pentafluoro styrene content in the copolymer, the water absorption was decreased to one‐third of that for pure PMMA. The fluorinated styrenes‐MMA copolymers were thermally stable up to 420 °C under air and nitrogen atmospheres. With 50 mol % of MMA in the copolymer, the copolymer was still stable up to 350 °C. Since these copolymers contain a large number of fluorine atoms, the light absorption in the region of the visible to near infrared is decreased in comparison with nonfluorinated polymers. Thus, these copolymers may be suitable for application in optical devices, such as optical fibers and waveguides. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010
Polymerization of epoxidized vegetable oil derivatives: Ionic‐coordinative polymerization of methylepoxyoleate
Authors: Del Rio E. , Galià M. , Cádiz V. , Lligadas G. , Ronda J. C. 
Published: September 2010

AbstractRing‐opening polymerization of epoxidized methyloleate (EMO) with various ionic‐coordinative initiators have been studied and compared with other internal epoxy monomers: benzyl 9,10‐epoxyoleoylether and cis‐4,5‐epoxyoctane. The structure and molecular weight of the resulting polymers have been studied by 1H‐ and 13C‐NMR, MALDI‐TOF‐MS, and size exclusion chromatography analysis. Polymers with higher molecular weight than those obtained with conventional cationic catalyst are obtained. These materials have been found to consist of a complex mixture of cyclic and linear polymer chains with different chain ends that can be related to the catalyst nature and the occurrence of two main polymerization mechanisms, the cationic and the ionic‐coordinative. In the polymerization of EMO, transesterification by‐side reactions leading to ester linkages in the main chain have been identified. These undesired reactions have been suppressed by copolymerization with small amounts of tetrahydrofuran with no substantial decrease in the polymer yield and molecular weight. Finally, the polymerization of EMO has been tested in a larger scale to prepare a renewable resource‐based polyether as starting material to produce polyether polyols for polyurethane applications. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010
Dynamic crystallization behavior, morphology, and physical properties of highly concentrated poly(vinylidene fluoride)/silver nanocomposites
Authors: Chae Dong Wook , Hong Soon Man 
Published: September 2010

AbstractThe effects of the inclusion of silver (Ag) nanoparticles on the physical properties, the crystallization behavior under shear, and the consequential crystalline morphology of poly(vinylidene fluoride) (PVDF) were investigated. Ag nanoparticles were melt compounded with PVDF in weight fractions of 20, 50, and 90 wt % (15.3 vol %). In the melt rheology, the presence of 20 wt % Ag nanoparticles had little effect on the dynamic viscosity of PVDF, but further addition increased it with the loading level. In Cole–Cole plot, all the melts gave a single master curve independent of the presence of Ag nanoparticles. As Ag loading level was increased, the overall crystallization process under shear was accelerated by reducing both induction time and crystallization time. The degree of acceleration was more notable at higher crystallization temperatures. The induction time and the crystallization time of 90 wt % loaded nanocomposites were promoted by 53.5 and 3.7%, respectively, at 145 °C and by 62 and 26.3%, respectively, at 160 °C, compared with those of pure PVDF. For the isothermal crystallization measured by differential scanning calorimeter, the critical Ag concentration, where overall crystallization was not promoted by further addition, occurred between 50 and 90 wt %. Both wide angle X‐ray diffraction profiles and Fourier transform infrared spectra of the samples crystallized under shear displayed the peaks for only α‐form crystals without new peak or peak shift regardless of the Ag loading and crystallization temperature. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010
Main Species and Physicochemical Processes in Cold Atmospheric‐pressure He + O2 Plasmas
Authors: Liu Ding‐Xin , Rong Ming‐Zhe , Wang Xiao‐Hua , Iza Felipe , Kong Michael G. , Bruggeman Peter 
Published: September 2010

AbstractThe main species and chemical processes in low‐temperature atmospheric‐pressure He + O2 plasmas are identified using a comprehensive global model. The simulation results highlight the significance of Penning processes at low oxygen concentration, and the increasingly important role of electron attachment as the oxygen concentration increases. With increasing the oxygen concentration, the electron energy dissipation shifts from elastic collisions with He to dissociative excitation and attachment of O2 molecules, and large ions (${\rm O}_{3}^{ + } $, ${\rm O}_{4}^{ + } $) become the dominant charged species. Generation and loss of ROS (O, O(1D), O(1S), O2(a1Δg), O2(b1∑), O3) relevant for biomedical applications are discussed.
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Human pyruvate kinase M2: A multifunctional protein
Authors: Gupta Vibhor , Bamezai Rameshwar N.K. 
Published: September 2010

AbstractGlycolysis, a central metabolic pathway, harbors evolutionary conserved enzymes that modulate and potentially shift the cellular metabolism on requirement. Pyruvate kinase, which catalyzes the last but rate‐limiting step of glycolysis, is expressed in four isozymic forms, depending on the tissue requirement. M2 isoform (PKM2) is exclusively expressed in embryonic and adult dividing/tumor cells. This tetrameric allosterically regulated isoform is intrinsically designed to downregulate its activity by subunit dissociation (into dimer), which results in partial inhibition of glycolysis at the last step. This accumulates all upstream glycolytic intermediates as an anabolic feed for synthesis of lipids and nucleic acids, whereas reassociation of PKM2 into active tetramer replenishes the normal catabolism as a feedback after cell division. In addition, involvement of this enzyme in a variety of pathways, protein–protein interactions, and nuclear transport suggests its potential to perform multiple nonglycolytic functions with diverse implications, although multidimensional role of this protein is as yet not fully explored. This review aims to provide an overview of the involvement of PKM2 in various physiological pathways with possible functional implications.
Effects of flammability characteristics of methane with three inert gases
Authors: Wu Siou‐Yuan , Lin Nung‐Kai , Shu Chi‐Min 
Published: September 2010

AbstractIn the chemical industries the three most common accidents are due to toxic releases, fires, and explosions, with most occurring in the form of fires and explosions. The reasons for these accidents predominantly arise out of a lack of awareness of flammability properties of flammable substances. To evaluate the fire/explosion hazards involved and ensure the safety and optimal operation of reactors, vessels or storage tanks, it is necessary to recognize the flammability characteristics of flammable materials. By means of a 20‐L‐Apparatus, we investigated the flammability and explosion characteristics of methane with three different inert gases (CO2, N2, and Ar) at 1 atm. 30 and 100°C, and many air concentrations. Our test results determined that the inert influence on methane by CO2 is better than N2 and Ar. The results of this article include graphs that show the lower and upper flammability regions and the explosion characteristics for these inerted systems. The flammability ranges include results for 30 and 100°C. © 2010 American Institute of Chemical Engineers Process Saf Prog, 2010
Synthesis and conformational analysis of salivary proline‐rich peptide P‐B
Authors: Kamysz Elżbieta , Sikorska Emilia 
Published: September 2010

AbstractThe 57‐amino acid human salivary polypeptide P‐B has been synthesized by the solid‐phase method using 9‐fluorenylmethoxycarbonyl (Fmoc) strategy. The circular dichroism (CD) spectroscopy, Fourier‐transform infrared spectroscopy (FTIR) and molecular modeling methods have been used for conformational studies of P‐B. Examination of the CD spectra of P‐B showed the content of the secondary structure to be independent of temperature over the range 0–60 °C at pH = 7 as well as over the pH range of 2–12 at 37 °C. P‐B adopts predominantly unordered structure with locally appearing β‐turns. The cumulative results obtained using the CD and FTIR spectroscopic techniques indicate the percentage of the polyproline type‐II (PPII) helix being as low as about 10%. Similarly, the molecular dynamics (MD) simulations reveal only a short PPII helix in theC‐terminal fragment of the peptide (Pro51–Pro54), which constitutes 7%. Copyright © 2010 European Peptide Society and John Wiley & Sons, Ltd.
Identification of spathulenol in Salvia mirzayanii and the immunomodulatory effects
Authors: Ziaei Akram , Ramezani Mohammad , Wright Louwrance , Paetz Christian , Schneider Bernd , Amirghofran Zahra 
Published: September 2010

AbstractThe methanol extract of Salvia mirzayanii has shown an immunomodulatory effect on peripheral blood lymphocytes. Bioassay‐guided fractionation using a lymphocyte proliferation assay on Salvia mirzayanii was performed in order to purify and identify the active compounds. Fractionation of the methanol extract and purification of the components using normal column chromatography and preparative thin layer chromatography resulted in identification of the bioactive compound, spathulenol, with an immunoinhibitory effect. Identification of this compound was performed by 1D and 2D NMR methods and HRMS. Treatment of activated lymphocytes with a concentrated fraction containing 62% of spathulenol (SP) showed a decrease in the proliferation of lymphocytes with an IC50 of 85.4 ± 11.08 µg/mL. Flow cytometry analysis using annexin V and propidium iodide staining of the stimulated peripheral blood lymphocytes in the presence of SP demonstrated a dose dependent increase in the percentage of apoptotic cells (IC50; 77.2 ± 5.31 µg/mL). No significant increase in caspase 3 activity in a 20 h treatment of stimulated lymphocytes compared with the control was observed. In conclusion, this study identified the possible activity of spathulenol as one of the immunomodulatory compounds present in Salvia mirzayanii. SP showed the capacity to inhibit proliferation in the lymphocytes and to induce apoptosis in these cells possibly through a caspase‐3 independent pathway. Copyright © 2010 John Wiley & Sons, Ltd.
Role of alpha class glutathione transferases (GSTs) in chemoprevention: GSTA1 and A4 overexpressing human leukemia (HL60) cells resist sulforaphane and curcumin induced toxicity
Authors: Sharma Rajendra , Ellis Bryan , Sharma Abha 
Published: September 2010

AbstractAlpha‐class glutathione transferases (α‐GSTs) have been shown to protect cells from the harmful effects of reactive oxygen species (ROS) induced lipid peroxidation (LPO) during oxidative stress caused by various physico‐chemical agents. While GSTA1‐1/A2‐2 isozymes exhibit high activity towards lipid and fatty acid hydroperoxides through their selenium independent glutathione peroxidase (GPx) activity, the GSTA4‐4 isozyme efficiently metabolizes the LPO product 4‐hydroxynonenal (4‐HNE) by conjugating it with glutathione (GSH). Because of the fact that ROS generated by the chemopreventive agents, sulforaphane (SFN) and curcumin (Cur), are implicated in the mechanisms of cancer cell killing, the present studies were designed to investigate the contribution of ROS induced LPO in the cytotoxic effects of these agents and the role of α‐class GSTs in modulating their toxicity. Human erythroleukemic (HL60) cells were stably transfected with the cDNA encoding the hGSTA1‐1 and mGsta4‐4 isozymes. After analysing the expression and activities of the respective GST isozymes, the effects of SFN and Cur on the extent of LPO, cytotoxicity and apoptosis were compared in empty vector (VT), hGSTA1‐1 and mGsta4‐4 expressing HL60 cells. These studies demonstrate that when compared with SFN, Cur was relatively more cytotoxic to HL60 cells. The ectopic expression of hGSTA1‐1 and mGsta4‐4 isozymes provided resistance to SFN and Cur induced cytotoxicity and apoptosis through a significant suppression of LPO in these cells. Overall, the results suggest that the expression of α‐class GSTs in cancer cells can modulate the therapeutic efficacy of chemopreventive agents. Copyright © 2010 John Wiley & Sons, Ltd.
Hydrolysates of citrus plants stimulate melanogenesis protecting against UV‐induced dermal damage
Authors: Chiang Hsiu‐Mei , Lin Jen‐Wen , Hsiao Pei‐Ling , Tsai Shang‐Yuan , Wen Kuo‐Ching 
Published: September 2010

AbstractThe sun‐tanning process occurs as a spontaneous response to ultraviolet (UV) irradiation. UV will induce tanning and DNA damage, processes that can lead to photoaging and skin disorders such as hyperpigmentation and cancer. The pigment melanin protects skin from UV damage; therefore, an efficient melanin‐promoting suntan lotion could be highly beneficial. In this study, a process was developed to increase the content of naringenin in citrus extracts and to determine whether a higher naringenin content of citrus would induce melanogenesis. Melanin content and tyrosinase expression in mouse B16 melanoma cells were assayed after treatment with citrus plant extracts and their hydrolysates. The results indicate that hydrolysis increased the naringenin content in citrus extracts and that citrus preparations stimulated cellular melanogenesis and tyrosinase expression. It is suggested that this method is applicable to the industrial production of melanin‐promoting suntan lotions with antiphotocarcinogenic properties derived from citrus rind and citrus products. Copyright © 2010 John Wiley & Sons, Ltd.
Long-Term Survival of Photoreceptors Transplanted into the Adult Murine Neural Retina Requires Immune Modulation
Authors: West Emma L. , Pearson Rachael A. , Barker Susie E. , Luhmann Ulrich F.O. , Maclaren Robert E. , Barber Amanda C. , Duran Yanai , Smith Alexander J. , Sowden Jane C. , Ali Robin R. 
Published: September 2010

AbstractStem cell therapy presents an opportunity to replace photoreceptors that are lost as a result of inherited and age-related degenerative disease. We have previously shown that murine postmitotic rod photoreceptor precursor cells, identified by expression of the rod-specific transcription factor Nrl, are able to migrate into and integrate within the adult murine neural retina. However, their long-term survival has yet to be determined. Here, we found that integrated Nrl.gfp+ve photoreceptors were present up to 12 months post-transplantation, albeit in significantly reduced numbers. Surviving cells had rod-like morphology, including inner/outer segments and spherule synapses. In a minority of eyes, we observed an early, marked reduction in integrated photoreceptors within 1 month post-transplantation, which correlated with increased numbers of amoeboid macrophages, indicating acute loss of transplanted cells due to an inflammatory response. In the majority of transplants, similar numbers of integrated cells were observed between 1 and 2 months post-transplantation. By 4 months, however, we observed a significant decrease in integrated cell survival. Macrophages and T cells were present around the transplantation site, indicating a chronic immune response. Immune suppression of recipients significantly increased transplanted photoreceptor survival, indicating that the loss observed in unsuppressed recipients resulted from T cell-mediated host immune responses. Thus, if immune responses are modulated, correctly integrated transplanted photoreceptors can survive for extended periods of time in hosts with partially mismatched H-2 haplotypes. These findings suggest that autologous donor cells are optimal for therapeutic approaches to repair the neural retina, though with immune suppression nonautologous donors may be effective.
Crosstalk Between the PI3K/mTOR and MEK/ERK Pathways Involved in the Maintenance of Self-Renewal and Tumorigenicity of Glioblastoma Stem-Like Cells
Authors: Sunayama Jun , Matsuda Ken-Ichiro , Sato Atsushi , Tachibana Ken , Suzuki Kaori , Narita Yoshitaka , Shibui Soichiro , Sakurada Kaori , Kayama Takamasa , Tomiyama Arata , Kitanaka Chifumi 
Published: September 2010

Abstract
The molecular signaling pathways orchestrating the biology of cancer stem-like cells (CSLCs), including glioblastoma, remain to be elucidated. We investigated in this study the role of the MEK/extracellular signal-regulated kinase (ERK) pathway in the control of self-renewal and tumorigenicity of glioblastoma CSLCs, particularly in relation to the PI3K/mTOR (mammalian target of rapamycin) pathway. Targeted inactivation of MEK alone using pharmacological inhibitors or siRNAs resulted in reduced sphere formation of both cell line- and patient-derived glioblastoma CSLCs, accompanied by their differentiation into neuronal and glial lineages. Interestingly, this effect of MEK inactivation was apparently augmented in the presence of NVP-BEZ235, a dual inhibitor of PI3K and mTOR. As a potential explanation for this observed synergy, we found that inactivation of either the MEK/ERK or PI3K/mTOR pathway triggered activation of the other, suggesting that there may be mutually inhibitory crosstalk between these two pathways. Significantly, inactivation of either pathway led to the reduced activation of p70S6K, and siRNA-mediated knockdown of p70S6K resulted in the activation of both pathways, which no longer maintained the cross-inhibitory relationship. Finally, combinational blockade of both pathways in glioblastoma CSLCs suppressed their tumorigenicity, whether transplanted subcutaneously or intracranially, more efficiently than blockade of either alone. Our findings suggest that there is p70S6K-mediated, cross-inhibitory regulation between the MEK/ERK and PI3K/mTOR pathways, in which each contribute to the maintenance of the self-renewal and tumorigenic capacity of glioblastoma CSLCs. Thus, combinational disruption of these pathways would be a rational and effective strategy in the treatment of glioblastoma.
Alternative mRNA polyadenylation in eukaryotes: an effective regulator of gene expression
Authors: Lutz Carol S. , Moreira Alexandra 
Published: September 2010

AbstractAlternative RNA processing mechanisms, including alternative splicing and alternative polyadenylation, are increasingly recognized as important regulators of gene expression. This article will focus on what has recently been described about alternative polyadenylation in development, differentiation, and disease in higher eukaryotes. We will also describe how the evolving global methodologies for examining the cellular transcriptome, both experimental and bioinformatic, are revealing new details about the complex nature of alternative 3′ end formation as well as interactions with other RNA‐mediated and RNA processing mechanisms. WIREs RNA 2011 2 22–31 DOI: 10.1002/wrna.47This article is categorized under:

RNA Interactions with Proteins and Other Molecules > Protein–RNA Recognition
RNA Processing > 3' End Processing
DEAD‐box proteins as RNA helicases and chaperones
Authors: Jarmoskaite Inga , Russell Rick 
Published: September 2010

AbstractDEAD‐box proteins are ubiquitous in RNA‐mediated processes and function by coupling cycles of ATP binding and hydrolysis to changes in affinity for single‐stranded RNA. Many DEAD‐box proteins use this basic mechanism as the foundation for a version of RNA helicase activity, efficiently separating the strands of short RNA duplexes in a process that involves little or no translocation. This activity, coupled with mechanisms to direct different DEAD‐box proteins to their physiological substrates, allows them to promote RNA folding steps and rearrangements and to accelerate remodeling of RNA–protein complexes. This review will describe the properties of DEAD‐box proteins as RNA helicases and the current understanding of how the energy from ATPase activity is used to drive the separation of RNA duplex strands. It will then describe how the basic biochemical properties allow some DEAD‐box proteins to function as chaperones by promoting RNA folding reactions, with a focus on the self‐splicing group I and group II intron RNAs. WIREs RNA 2011 2 135–152 DOI: 10.1002/wrna.50This article is categorized under:

RNA Structure and Dynamics > RNA Structure, Dynamics, and Chemistry
RNA-Based Catalysis > Miscellaneous RNA‐Catalyzed Reactions
RNA Interactions with Proteins and Other Molecules > Protein–RNA Recognition