Distribution by Scientific Domains

Kinds of Initiator

  • anionic initiator
  • bifunctional initiator
  • cationic initiator
  • efficient initiator
  • free radical initiator
  • free-radical initiator
  • multifunctional initiator
  • novel initiator
  • peroxide initiator
  • radical initiator
  • redox initiator
  • water-soluble initiator

  • Terms modified by Initiator

  • initiator caspase
  • initiator concentration
  • initiator decomposition
  • initiator efficiency
  • initiator molar ratio
  • initiator protein
  • initiator ratio
  • initiator system
  • initiator type

  • Selected Abstracts

    First Example of a Gold(I) N -Heterocyclic-Carbene-Based Initiator for the Bulk Ring-Opening Polymerization of L -Lactide

    Lipika Ray
    Abstract Synthesis, structure, and catalysis studies of two Au- and Ag-based initiators, namely, [3-(N - tert -butylacetamido)-1-(2-hydroxycyclohexyl)imidazol-2-ylidene]AuCl (1c) and [3-(N - tert -butylacetamido)-1-(2-hydroxycyclohexyl)imidazol-2-ylidene]AgCl (1b), for the bulk ring-opening polymerization of L -lactide are reported. Specifically, gold complex 1c was obtained from silver complex 1b by the transmetalation reaction with (SMe2)AuCl. Silver complex 1b was synthesized by the treatment of 3-(N - tert -butylacetamido)-1-(2-hydroxycyclohexyl)imidazolium chloride (1a) with Ag2O. Compound 1a was synthesized directly from the reaction of N - tert -butyl-2-chloroacetamide, cyclohexene oxide, and imidazole. The molecular structures of 1a, 1b, and 1c have been determined by X-ray diffraction studies. The formation of neutral monomeric complexes with linear geometries at the metal centers was observed for both 1b and 1c. The Au and Ag complexes 1c and 1b successfully catalyzed the bulk ring-opening polymerization of L -lactide at elevated temperatures under solvent-free melt conditions to produce moderate to low molecular weight polylactide polymers with narrow molecular weight distributions. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]

    Functional analysis of Drosophila melanogaster hexokinase Hex-A locus: multiple Initiator-like elements enhance DPE containing promoter activity

    P. C. Jayakumar
    Abstract Flight muscle Hexokinase-A (HEX-A) is the most conserved and essential hexokinase isoenzyme among Drosophila species. In this study, the Hex-A locus, encoding the HEX-A isoenzyme, has been analysed for the elements regulating its expression. By sequencing the 5, ends of Hex-A cDNA amplified by 5, RACE, we identified a transcription start site that overlapped the Initiator and downstream promoter elements. A 214 bp sequence, encompassing transcription start sites and promoter elements, was required for minimal promoter activity. DNA sequence to the 5, end of the minimal promoter element did not demonstrate any promoter activity; however, its inclusion with the basal promoter element enhanced the promoter activity. Oligonucleotide competition and site-directed mutagenesis identified the Initiator-like sequences, TCAWT, present in this region that were responsible for enhancing the promoter activity. The Hex-A locus is expressed as a single protein in Drosophila cell line, whereas in pupae, larvae and adult flies, it is expressed as two distinct types. [source]

    Preparation of polyacrylonitrile with improved isotacticity and low polydispersity

    Jianguo Jiang
    Abstract The preparation of a polymer with both low polydispersity and high tacticity is one current challenge we face and warrants thorough investigation from both the theoretical and experimental standpoints. In this study, we synthesized polyacrylonitrile (PAN) with simultaneously controlled molecular weight and tacticity on the basis of the strategy of the atom transfer radical polymerization (ATRP) of acrylonitrile (AN) in the presence of Lewis acids. A new combined initiation system of 3-bromopropionitrile (3-BPN)/Cu2O/N,N,N,,N,-tetramethylethylenediamine (TMEDA) was used for the ATRP of AN for the first time. When the polymerization was performed with the ratio [AN]0/[Initiator]0/[Cu2O]0/[TMEDA]0 = 190/1/0.5/1.5 (where the subscript 0 indicates the initial conditions) in ethylene carbonate at 60°C for 48 h, the polydispersity of the obtained PAN was 1.13, and the molecular weight was up to 13,710. The polymerization kinetics results show that the polymerizations proceeded with a living/controlled nature except that an induction period existed during the polymerization process because of the lower initiating activity of 3-BPN. Also, two kinds of Lewis acid, AlCl3 and yttrium trifluororomethanesulflnate, were used in the ATRP system of AN for the tacticity control. The addition of 0.01 equiv (relative to AN) of the Lewis acid AlCl3 in the polymerization afforded PAN with an improved isotacticity [meso/meso triad (mm) = 0.32] and a very narrow polydispersity (1.06). © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]

    Microphase-Separated Poly(vinylpyridine) Block Copolymer Prepared with a Novel Bifunctional Initiator

    Masami Shoji
    Abstract A vinylpyridine block copolymer was prepared by stepwise controlled/living radical polymerization with a novel bifunctional initiator, 4-(2-bromopropanoyloxy)- N -(p -methylbenzyloxy)-2,2,6,6-tetramethylpiperidine. The initiator was synthesized in a facile manner using commercially available p -xylene and 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (4-hydroxy TEMPO). Through stepwise atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) and nitroxide-mediated radical polymerization (NMRP) of 4-vinylpyridine (4VP), the PMMA- b- P4VP copolymer was prepared with a wide range of the copolymer compositions. Microphase-separation was demonstrated in cross sectional TEM images of self-standing block copolymer membranes. [source]

    Highly Defined ABC Triblock Cooligomers and Copolymers Prepared by ROMP Using an N -Heterocyclic-Carbene-Substituted Ruthenium Benzylidene Initiator

    Christian Slugovc
    Abstract The "3rd generation Grubbs" initiator (H2IMes)(3-bromopyridine)2(Cl)2RuCHPh (1) accomplishes the synthesis of ABC triblock copolymers via living ring-opening metathesis polymerisation (ROMP) of norbornene derivatives. Complete initiation and an outstanding tolerance of functional groups are provided, which is proven by a combined study by means of matrix-assisted laser desorption/ionisation mass spectrometry, gel permeation chromatography and NMR spectroscopy on an ABC triblock cooligomer. Gel permeation chromatograms of oligoA, oligoAB, and oligoABC. [source]

    Kinetics Approximation Considering Different Reactivities of the Structural Units Formed by the Anionic Copolymerization of 1,3-Butadiene and Styrene Using Al/Li/Ba as Initiator

    José. A. Tenorio López
    Abstract The copolymerization reaction of butadiene and styrene copolymers prepared by anionic living polymerization using an initiator composed of alkyl aluminum, n -butyl lithium, and barium alkoxide is studied using a kinetic model that considers the reactivity of active sites to be different; this assumption is justified by the varying geometric configurations. With the first-order Markov model, the expressions for the fraction of active sites and dyad distribution are obtained. The rate constants are determined by fitting to the conversion and Bernoulli dyad data using the nonlinear least squares method. The conversion and dyad sequence distribution are correctly predicted, and the experimental results indicate that the microstructure and sequence distribution do not change with the conversion and temperature. [source]

    Pathophysiology of the Pulmonary Vein as an Atrial Fibrillation Initiator:

    From Bench to Clinic
    The basic electrophysiologic studies have proved the arrhythmogenic mechanisms of the pulmonary vein as an atrial fibrillation initiator; the mechanisms include enhanced automaticity, triggered activity, and microreentry from myocardial sleeves inside pulmonary veins. Immunohistology study has proved the conduction characteristics of pulmonary vein myocardium, and further study of ionic currents are important for understanding atrial fibrillation initiation from the pulmonary vein. (PACE 2003; 26[Pt. II]:1576,1582) [source]

    Photosynthesis nuclear genes generally lack TATA-boxes: a tobacco photosystem I gene responds to light through an initiator

    THE PLANT JOURNAL, Issue 1 2002
    Masayuki Nakamura
    Summary The promoter architecture of the nuclear-encoded photosystem I genes was studied using a tobacco gene, psaDb, as a model case. Linker scanning mutations revealed that the psaDb promoter does not have a TATA box. Instead, pyrimidine-rich Initiator (Inr) elements that overlap the transcription start sites are essential for light-responsive transcription of this gene. When the psaDb promoter was mutated to have a TATA-box but no Inr, light-responsive transcription was impaired, indicating that the regulatory system of this gene prefers Inr to a TATA box. As very little is known about plant TATA-less promoters, we subsequently examined whether this promoter architecture is unique to psaDb. Computer analysis of 232 plant promoters revealed surprising features; the majority of photosynthesis nuclear genes lacked TATA boxes, although the frequency of the TATA-less promoters in non-photosynthesis genes was less than 10%. These results strongly suggest that TATA-independent transcription mechanisms play important roles in the regulated expression of photosynthesis nuclear genes. [source]

    Side Chain Bromination of Mono and Dimethyl Heteroaromatic and Aromatic Compounds by Solid Phase N-Bromosuccinimide Reaction Without Radical Initiator under Microwave.

    CHEMINFORM, Issue 49 2004
    Shyamaprosad Goswami
    Abstract For Abstract see ChemInform Abstract in Full Text. [source]

    ChemInform Abstract: Stereocontrol in Radical Processes Through the Exocyclic Effect: Dual Role of Triethylboron as Radical Initiator and in situ Derivatization Agent.

    CHEMINFORM, Issue 34 2001
    Jean-Pierre Bouvier
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

    Atom Transfer Radical Polymerization of Styrene Using a Bifunctional Initiator

    Jin-Ying Yuan
    Abstract A bifunctional alkyl halide, namely l, 2-bis(2,-bromobutyryl) ethane (BBrBE), was synthesized and used to initiate the bulk atom transfer radical polymerization (ATRP) of styrene (St) at 110°C in the presence of CuBr/2,2,-bipyridyl. The narrow polydispersity of polystyrene (PSt) with precisely two arms could be synthesized. The initiate ability of the two active bromide functional groups at both sides of BBrBE for St and the propagation ability of the two arms were confirmed to be similar by the characterization of the individual arms obtained upon hydrolysis of the ester link between the core and the branches. [source]

    Simple Ruthenium Precatalyst for the Synthesis of Stilbene Derivatives and Ring-Closing Metathesis in the Presence of Styrene Initiators

    Cheikh Lo
    Abstract The ruthenium complex RuCl2(p -cymene)(IMes) was found to be an efficient precatalyst, with styrene as an initiating species, for the alkene metathesis of various styrenes into symmetrical and unsymmetrical stilbene derivatives and for the ring-closing metathesis reaction of a sterically hindered olefin leading to a tetrasubstituted cycloolefin. [source]

    Alkyl Zinc Chlorides as New Initiators for the Polymerization and Copolymerization of Isobutene

    Antonio Guerrero
    Abstract Mixtures of RZnCl and tBuCl (R,=,Et) initiate the polymerization of isobutene in the temperature range of (,35),(+35),°C. The order of addition of the reagents is important for effective polymerization. Increasing the solubility of the zinc reagent (R,=,n -octyl) and use of cumyl chloride as co-initiator provides a system that is active from (,90),(+35),°C. The molecular weights show a remarkably small temperature dependence, EDP,=,,3.3 kJ,·,mol,1, compared to EDP,=,,23 kJ,·,mol,1 in classical systems (AlCl3, EtAlCl2). The molecular weights increase with decrease in zinc concentration and are consistently higher for n -octyl zinc chloride, as expected for a bulkier, less coordinating counteranion. The polymerizations are not retarded by isoprene addition; homopolymers and copolymers show essentially identical conversions and molecular weights. [source]

    Clay-PMMA Nanocomposites by Photoinitiated Radical Polymerization Using Intercalated Phenacyl Pyridinium Salt Initiators

    Alper Nese
    Abstract Summary: In situ synthesis of poly(methyl methacrylate) (PMMA) nanocomposites by photopolymerization using organophilic montmorillonite (MMT) as the layered clay is reported. MMT clay was ion exchanged with N -phenacyl, N,N -dimethylanilinium hexafluoro phosphate (PDA) which acts as both suitable intercalant- and photo-initiator. These modified clays were then dispersed in methyl methacrylate (MMA) monomer in different loading degrees to carry out the in situ photopolymerization. Intercalation ability of the photoinitiator and exfoliated nanocomposite structure were evidenced by both X-ray diffraction (XRD) spectroscopy and transmission electron microscopy (TEM). Thermal properties and morphologies of the resultant nanocomposites were also studied. Schematic representation of clay-PMMA nanocomposites by photoinitiated radical polymerization. [source]

    Cationic Polymerization of 2-Vinylthiophene by Chloroarylmethanes as Surface Initiators on Silica and Consecutive Hydride Abstraction by Acceptors

    Susanne Höhne
    Abstract Summary: 2-Vinylthiophene (2-VT) has been cationically polymerized using chloroarylmethane derivatives as the surface polymerization initiator on silica. By applying this procedure a soluble fraction of poly(vinylthiophene) (PVT) and PVT/silica composites can be simultaneously synthesized. The mass balance of the products (soluble fraction and hybrid particle fraction) depends significantly on temperature and 2-VT/silica ratio. The hydride abstraction reaction of PVT both in solution and immobilized on silica particle surface has been studied using 2,3-dichloro-5,6-dicyano-1,4-quinone (DDQ), tetrachloro-1,4-quinone (chloranile,=,ClA) and triphenylmethylium as reagents. The transformation process of PVT towards conjugated polymers has been studied with UV-vis spectroscopy and ESR spectroscopy. Cyclic voltammetry shows that chloranil is complexated with the formed polymer. Radical formation increases with increasing degree of conversion. The soluble fraction of the conjugated PVT sections formed is capable of reacting with each other as evidenced by GPC data. Structure of PVT/silica and resulting hybrid materials have been investigated by solid state 13C {1H} CP MAS NMR-spectroscopy showing a reaction of methine and methylene hydrogen atoms after treatment with DDQ or chloranil as hydride acceptors. For all poly-(2-vinylthiophene)/hydride acceptor systems studied, chloranil has been found to be the best reagent for the transformation of PVT towards conjugated polymers. Transformation of PVT in poly(2-ethinylthiophene) (PET) and PVT-PET copolymers. [source]

    Prediction of Chain Length Distribution of Polystyrene Made in Batch Reactors with Bifunctional Free-Radical Initiators Using Dynamic Monte Carlo Simulation

    Ibrahim M. Maafa
    Abstract The objective of this paper is to present a dynamic Monte Carlo model that is able to simulate the polymerization of styrene with bifunctional free-radical initiators in a batch reactor. The model can predict the dynamic evolution of the chain length distribution of polystyrene in the reactor. The model includes all relevant polymerization mechanistic steps, including chemical and thermal radical generation, and diffusion-controlled termination. The model was applied to styrene polymerization and the Monte Carlo estimates for chain length averages were compared to those obtained with the method of moments. Excellent agreement was obtained between the two methods. Although styrene polymerization was used as a case study, the proposed methodology can be easily extended to any other polymer type made by free-radical polymerization. [source]

    Fluorocarbon End-functionalized Polymers from Poly(arylether) Dendritic Initiators

    A. Pillay Narrainen
    Abstract Fréchet-type poly(arylether) first and second generation (G1 and G2 respectively) dendrons were prepared from 1-(bromomethyl)-3,5-bis(trifluoromethyl)benzene. The latter and the brominated versions of the two dendrons were successfully employed in the copper mediated living radical polymerization (LRP) of styrene-d8 giving polymers of predictable molecular weights and narrow polydispersities. Contact angle measurements and ion beam analysis were used to explore the adsorption of these materials to the air-polymer surface in blended films with unfunctionalized hydrogenous polystyrene. Although contact angle analysis indicated only modest changes in the hydrophobicity and lipophobicity of the surface, ion beam analysis clearly showed the formation of an excess layer of dendron functionalized polymer at the exposed surface that increased with increasing fluorine content. [source]

    Mathematical Modeling of Atom-Transfer Radical Polymerization Using Bifunctional Initiators

    Mamdouh Al-Harthi
    Abstract Summary: Bifunctional initiators can produce polymers with higher molecular weight at higher initiator concentrations than monofunctional initiators. In this study, we developed a mathematical model for ATRP with bifunctional initiators. The most important reactions in ATRP were included in the model. The method of moments was used to predict monomer conversion, average molecular weights and polydispersity index as a function of polymerization time in batch reactors. The model was used to understand the mechanism of ATRP and to quantify how polymerization conditions affect monomer conversion and polymer properties by examining the effect of several rate constants (activation, deactivation, propagation and chain termination) and of catalyst and initiator concentration on polymerization kinetics and polymer properties. When compared to monofunctional initiators, bifunctional initiators not only produce polymers with higher molecular weight averages at higher polymerization rates, but also control their molecular weight distributions more effectively. Effect of initial catalyst concentration on polydispersity index as a function of time. [source]

    Synthesis, Structures, and Optical Properties of Two Novel Two-Photon Initiators Derived from 2,2,:6,,2,,-Terpyridine.

    CHEMINFORM, Issue 37 2007
    Jia-Xiang Yang
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source]

    Simple Ruthenium Precatalyst for the Synthesis of Stilbene Derivatives and Ring-Closing Metathesis in the Presence of Styrene Initiators.

    CHEMINFORM, Issue 28 2007
    Cheikh Lo
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source]

    Photoreactivity and Photopolymerization of Silicon-Bridged [1]Ferrocenophanes in the Presence of Terpyridine Initiators: Unprecedented Cleavage of Both Iron,Cyclopentadienyl Bonds in the Presence of Chlorosilanes

    Yan Chan
    Abstract The photopolymerisation of sila[1]ferrocenophane [Fe(,-C5H4)2SiMe2] (3) with 4,4,,4,,-tri- tert -butyl-2,2,:6,,2,,-terpyridine (tBu3terpy) as initiator has been explored. High-molecular-weight polyferrocenylsilane (PFS) [{Fe(,-C5H4)2SiMe2}n] (5) was formed in high yield when a stoichiometric amount of tBu3terpy was used at 5,°C. Photopolymerisation of ferrocenophane 3 at higher temperatures gave PFS 5 in lower yield and with a reduced molecular weight as a result of a slower propagation rate. Remarkably, when Me3SiCl was added as a capping agent before photopolymerisation, subsequent photolysis of the reaction mixture resulted in the unprecedented cleavage of both iron,Cp bonds in ferrocenophane 3: iron(II) complex [Fe(tBu3terpy)2Cl2] (7Cl) was formed and the silane fragment (C5H4SiMe3)2SiMe2 (8) was released. The iron,Cp bond cleavage reaction also proceeded in ambient light, although longer reaction times were required. In addition, the unexpected cleavage chemistry in the presence of Me3SiCl was found to be applicable to other photoactive ferrocenes such as benzoylferrocene. For benzoylferrocene and ferrocenophane 3, the presence of metal-to-ligand charge transfer (MLCT) character in their low-energy transitions in the visible region probably facilitates photolytic iron,Cp bond cleavage, but this reactivity is suppressed when the strength of the iron,Cp bond is increased by the presence of electron-donating substituents on the cyclopentadienyl rings. [source]

    Lanthanide Thiolate Complexes: Novel Initiators for Ring-opening Polymerization of ,-Caprolactone

    Hong-Mei Sun
    Abstract The ring-opening polymerization (ROP) of , -caprolactone (, -CL) using lanthanide thiolate complexes [(CH3C5H4)2Sm(,-SPh)(THF)] 2 (1) and Sm(SPh)3(HMPA)3 (2) as initiators has been investigated for the first time. Both of 1 and 2 were found to be highly efficient initiators for the ROP of , -CL. The poly(, -caprolactone) (PCL) with molecular weight Mn up to 1.97×105 and relatively narrow molecular weight distributions (1.20< Mw/Mn<2.00) have been obtained in high yield in the temperature range of 35,65 °C. According to the polymer yield, 2 showed much higher activity than 1. However, the number-average molecular weight of PCL obtained with 2 was much lower than with 1. The possible polymerization mechanism of the , -CL polymerization has been proposed based on the results of the end group analysis of the , -CL oligomer. [source]

    High-efficiency peptide analysis on monolithic multimode capillary columns: Pressure-assisted capillary electrochromatography/capillary electrophoresis coupled to UV and electrospray ionization-mass spectrometry

    ELECTROPHORESIS, Issue 21 2003
    Alexander R. Ivanov
    Abstract High-efficiency peptide analysis using multimode pressure-assisted capillary electrochromatography/capillary electrophoresis (pCEC/pCE) monolithic polymeric columns and the separation of model peptide mixtures and protein digests by isocratic and gradient elution under an applied electric field with UV and electrospray ionization-mass spectrometry (ESI-MS) detection is demonstrated. Capillary multipurpose columns were prepared in silanized fused-silica capillaries of 50, 75, and 100 ,m inner diameters by thermally induced in situ copolymerization of methacrylic monomers in the presence of n -propanol and formamide as porogens and azobisisobutyronitrile as initiator. N -Ethylbutylamine was used to modify the chromatographic surface of the monolith from neutral to cationic. Monolithic columns were termed as multipurpose or multimode columns because they showed mixed modes of separation mechanisms under different conditions. Anion-exchange separation ability in the liquid chromatography (LC) mode can be determined by the cationic chromatographic surface of the monolith. At acidic pH and high voltage across the column, the monolithic stationary phase provided conditions for predominantly capillary electrophoretic migration of peptides. At basic pH and electric field across the column, enhanced chromatographic retention of peptides on monolithic capillary column made CEC mechanisms of migration responsible for separation. The role of pressure, ionic strength, pH, and organic content of the mobile phase on chromatographic performance was investigated. High efficiencies (exceeding 300,000 plates/m) of the monolithic columns for peptide separations are shown using volatile and nonvolatile, acidic and basic buffers. Good reproducibility and robustness of isocratic and gradient elution pressure-assisted CEC/CE separations were achieved for both UV and ESI-MS detection. Manipulation of the electric field and gradient conditions allowed high-throughput analysis of complex peptide mixtures. A simple design of sheathless electrospray emitter provided effective and robust low dead volume interfacing of monolithic multimode columns with ESI-MS. Gradient elution pressure-assisted mixed-mode separation CE/CEC-ESI-MS mass fingerprinting and data-dependent pCE/pCEC-ESI-MS/MS analysis of a bovine serum albumin (BSA) tryptic digest in less than 5 min yielding high sequence coverage (73%) demonstrated the potential of the method. [source]

    Macroporous monolithic chiral stationary phases for capillary electrochromatography: New chiral monomer derived from cinchona alkaloid with enhanced enantioselectivity

    ELECTROPHORESIS, Issue 17 2003
    Michael Lämmerhofer
    Abstract A new chiral monomer derived from cinchona alkaloid, namely O -9-(tert -butylcarbamoyl)-11-[2-(methacryloyloxy)ethylthio]-10,11-dihydroquinine 1, was employed for the preparation of enantioselective monolithic capillary columns by an in situ copolymerization with 2-hydroxyethyl methacrylate 2 (HEMA), ethylene dimethacrylate 3 (EDMA) in the presence of cyclohexanol and 1-dodecanol as porogens (UV or thermal initiation of azobisisobutyronitrile (AIBN) as radical initiator). The porous properties and the electrochromatographic behavior of the new chiral monoliths were comparatively evaluated with previously described analogs obtained from O -9-[2-(methacryloyloxy)ethylcarbamoyl]-10,11-dihydroquinidine 4 as chiral monomer. Despite close structural and physicochemical similarities of the both chiral monomers, the pore distribution profiles of the resulting monoliths were shifted typically towards larger pore diameters with the new monomer 1. Once more, it was confirmed that a low cross-linking (10 wt% related to total monomers) and a pore diameter of about 1 ,m in the dry state provides the best electrochromatographic efficiency as a result of lower resistance to mass transfer (smaller C-term contribution to peak broadening) and more homogeneous flow profile (smaller A-term). Most importantly, as expected the new poly(1 - co -HEMA- co -EDMA) monoliths showed enhanced enantioselectivities and in addition faster separations as compared to poly(4 - co -HEMA- co -EDMA) analogs, which represents a significant improvement. Further, the elution order was reversed owing to the pseudoenantiomeric behavior of quinine- and quinidine-derived monomers. Fluorescence-labeled 9-fluorenylmethoxycarbonyl (FMOC), dansyl (DNS), 7-dimethylaminosulfonyl-1,3,2-benzoxadiazol-4-yl (DBD), carbazole-9-carbonyl (CC) amino acids could be separated with resolution values between 2 and 4 (with efficiencies typically between 100,000 and 200,000 plates/m) and fluorescence detection (variable wavelength fluorescence detector in-line with UV) yielding routinely a gain in detection sensitivities up to two orders of magnitude without specific optimization of the conditions with regards to fluorescence efficiency. [source]

    Expression of caspase and apoptotic signal pathway induced by sulfur dioxide

    Juli Bai
    Abstract Sulfur dioxide (SO2) is a common air pollutant that is released in low concentrations into the atmosphere and in higher concentrations in some work places. In the present study, male Wistar rats were housed in exposure chambers and treated with 14.00 ± 1.01, 28.00 ± 1.77, and 56.00 ± 3.44 mg/m3 SO2 for 7 days (6 hr/day), while control rats were exposed to filtered air under the same conditions. The mRNA and protein levels of caspase-3, caspase-8, and caspase-9 were analyzed using a real-time reverse transcription-polymerase chain reaction (real-time RT-PCR) assay and an immunohistochemistry method. Activities of caspases were detected using colorimetric and fluorescent assays. Chromatin degradation and cell morphological changes were investigated by TUNEL assay and H&E staining in livers and lungs, respectively. The results showed that mRNA levels, protein levels and activities of caspase-3, caspase-8, and caspase-9 were increased in a dose-dependent manner in livers and lungs of rats after SO2 inhalation. In addition, livers were infiltrated with lymphocytes, congestion and inflammation occurred in lungs, and eosinophil cells and apoptotic cells increased in both livers and lungs after SO2 inhalation. These results suggest that SO2 exposure increases the expression and activity of both initiator and and effector caspases, and may induce apoptosis in liver and lung of rats through both death receptor and mitochondrial pathways. Environ. Mol. Mutagen. 2010. © 2009 Wiley-Liss, Inc. [source]

    Cellular microparticles: new players in the field of vascular disease?

    M. Diamant
    Abstract Microparticles are small membrane vesicles that are released from cells upon activation or during apoptosis. Cellular microparticles in body fluids constitute a heterogeneous population, differing in cellular origin, numbers, size, antigenic composition and functional properties. Microparticles support coagulation by exposure of negatively charged phospholipids and sometimes tissue factor, the initiator of coagulation in vivo. Microparticles may transfer bioactive molecules to other cells or microparticles, thereby stimulating cells to produce cytokines, cell-adhesion molecules, growth factors and tissue factor, and modulate endothelial functions. Microparticles derived from various cells, most notably platelets but also leucocytes, lymphocytes, erythrocytes and endothelial cells, are present in the circulation of healthy subjects. Rare hereditary syndromes with disturbances in membrane vesiculation leading to a decreased numbers of microparticles clinically present with a bleeding tendency. In contrast, elevated numbers of microparticles are encountered in patients with a great variety of diseases with vascular involvement and hypercoagulability, including disseminated intravascular coagulation, acute coronary syndromes, peripheral arterial disease, diabetes mellitus and systemic inflammatory disease. Finally, microparticles are a major component of human atherosclerotic plaques. In view of their functional properties, cell-derived microparticles may be an important intermediate in the cascade of cellular and plasmatic dysfunctions underlying the process of atherogenesis. [source]

    Synthesis and Characterization of MoOI2(PMe3)3 and Use of MoOX2(PMe3)3 (X = Cl, I) in Controlled Radical Polymerization

    José A. Mata
    Abstract Complex MoOCl2(PMe3)3 smoothly reacts with NaI in acetone to produce MoOI2(PMe3)3 in good yields. The geometry of the compound is mer - cis octahedral, that is, identical to that of the dichloride precursor, as shown by NMR spectroscopy and by an X-ray crystallographic study. Electrochemical investigations of MoOX2(PMe3)3 show irreversible oxidation waves at Ep,a = +0.18 and +0.39 V for X = Cl and I, respectively. A study of the halide exchange between MoOCl2(PMe3)3 and NaI, or between MoOI2(PMe3)3 and Bu4NCl, shows two equilibrated isomers for the mixed halide intermediate MoOICl(PMe3)3. The diiodide complex rapidly exchanges the iodo ligands with chloride upon dissolution in chloroform at room temperature, and with bromide from (1-bromoethyl)benzene (BEB) under more forcing conditions. The equilibrium favors the softer halide (I) on C and the harder one (Cl or Br) on MoIV. Both oxido compounds catalyze the atom transfer radical polymerization (ATRP) of styrene in combination with the BEB initiator, yielding polymers with quite narrow molecular weight distributions (down to 1.11). The apparent polymerization rate constant is approximately doubled in the presence of 1 equiv. of the Al(OiPr)3 cocatalyst. On the other hand, the system is not capable of efficiently controlling the radical chain growth for methyl acrylate polymerization. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]

    Polymers from renewable resources: Bulk ATRP of fatty alcohol-derived methacrylates

    Gökhan Çayli
    Abstract Copper-mediated atom transfer radical polymerization (ATRP) of lauryl methacrylate (LMA) and other long-chain methacrylates was investigated in bulk at 35,°C by using CuCl/N,N,N,,N,,N,, -pentamethyldiethylenetriamine (PMDETA)/tricaprylylmethylammonium chloride (Aliquat®336) as the catalyst system and ethyl 2-bromoisobutyrate (EBIB) as the initiator. The investigated monomers can be derived from fatty alcohols and are therefore an important renewable resource for a sustainable development of our future. The amounts of ligand, Aliquat®336 and CuCl were optimized and the effect of their concentrations on the control of the polymerization and the observed conversions were investigated. It was found that a molar ratio of EBIB/CuCl/Ligand/Aliquat®336 of 1,:,1,:,3,:,1 provided the highest conversions of LMA and the best controlled polymerizations. These optimized conditions allowed for the synthesis of poly(lauryl methcarylate)s with different targeted DP (25, 50, 75, 100, 120, 240, and 500), including high-molecular-weight polymers with narrow molecular weight distributions. In addition, methacrylate monomers were prepared from fatty alcohols (capric, myristic, palmitic, stearic) and polymerized using the developed procedure to obtain polymers with the same DP and different chain lengths (C10, C12, C14, C16, and C18) of pending alkyl groups. Finally, the thermal properties of these polymers were examined by differential scanning calorimetry and thermogravimetric analysis. [source]

    Radical Addition of Ethers to Terminal Alkynes with High E -Selectivity

    Zili Chen
    Abstract Direct radical additions of ethers to terminal alkynes were investigated by using Me2Zn/O2 as radical initiator to afford 2-vinyl ether derivatives with high E -selectivity, while reversed E/Z selectivity is obtained with Et3B/O2. Two competitive pathways are suggested for the formation of vinyl radical B: zinc-radical exchange (route a) followed by protonation provides E -configuration products exclusively through Zn(II) complexation. Hydrogen abstraction by vinyl radicals (route b) yields mainly Z isomers.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

    Non-governmental Organisation Participation in the EU Law-making Process: The Example of Social Non-governmental Organisations at the Commission, Parliament and Council

    EUROPEAN LAW JOURNAL, Issue 5 2008
    Israel De Jesús Butler
    The Commission's current transparency initiative has focused attention on the rules (or lack of) governing access to the Commission as the initiator of legislation. This article examines more broadly, on the basis of interviews, both the formal and informal means of accessing not only the Commission, but also the European Parliament (in particular through intergroups) as well as the Council. By using specific examples of legislation it illustrates the routes by which ,social' non-governmental organisations currently interact with these institutions, offering examples of how their work may impact on the output of the Commission, Council and Parliament. The article avoids an overly legalistic analysis with an original glimpse at the ,hidden' workings of the EU law-making process which has hitherto received little attention among legal academics and practitioners. [source]