bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation, properties, and anticorrosion application of poly(methyl methacrylate)/montmorillonite nanocomposites coating on brass via solution polymerization
Authors: Wang Tien‐Li , Hwang Weng‐Sing , Yeh Meng‐Heng
Published: March 2007

The aim of this study is to improve the anticorrosive property of 7Cu3Zn brass. The methyl‐methacrylate (MMA) monomer solution, modified with fluorine radical and silicone, was used as the polymer matrix to mix with the different percentages of modified montmorillonite (MMT) loading and to exfoliate the lamellar structure of MMT on a nanometer scale during the solution polymerization process, and then form a thin nanocomposites coating on brass as a protective layer. The structural characterization was examined using Fourier transform infrared spectroscopy, X‐ray diffraction (XRD), and transmission electron microscope (TEM). The anticorrosive property of nanocomposites was evaluated using potentiodynamics polarization and electrochemical impedance spectra. The results show that the d‐spacing of MMT was increased, and both exfoliation and intercalation microstructure were observed. Moreover, with the MMT loading increase, the appearance of the intercalation microstructure was more remarkable as a result of silicate layers aggregation. The 1.0 wt %‐coated brass coupons presented the optimistic property of anticorrosion, whose oxygen permeability, corrosion current (icorr), polarization resistance (Rp), and corrosion rate (Rcorr) were 3.5 g/(m2°h), 6.86 nA/cm2, 5.81 × 105 Ω°cm2, and 0.103 × 10−3 mm/year, respectively. These results indicate that nanocomposites have potential for anticorrosion application. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 4135–4143, 2007
Mechanical behaviors of ethylene/styrene interpolymer compatibilized polystyrene/polyethylene blends
Authors: Tang Jian , Tang Weihua , Yuan Huilin , Jin Riguang
Published: March 2007

In this study, ethylene/styrene interpolymer was used as a compatibilizer for the blends of polystyrene (PS) and high‐density polyethylene (HDPE). The mechanical properties including tensile and impact properties and morphology of the blends were investigated by means of uniaxial tension, instrumented falling‐weight impact measurements, and scanning electron microscopy. Tensile tests showed that the yield strength of the PS/HDPE/ESI blends decreases considerably with increasing HDPE content. However, the elongation at break of the blends tended to increase significantly with increasing HDPE content. The excellent tensile ductility of the HDPE‐rich blends resulted from shield yielding of the matrix. Izod and Charpy impact measurements indicated that the impact strength of the blends increases slowly with HDPE content up to 40 wt %; thereafter, it increases sharply with increasing HDPE content. The impact energy of the HDPE‐rich blends exceeded that of pure HDPE, implying that the HDPE polymer can be further toughened by the incorporation of brittle PS minor phase in the presence of ESI compatibilizer. The correlation between the impact property and morphology of the blends is discussed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 4001–4007, 2007
Preparation of nanoparticles composed of chitosan and its derivatives as delivery systems for macromolecules
Authors: Sun Yan , Wan Ajun
Published: March 2007

Three different kinds of nanoparticles for paracellular transport were prepared using a simple and mild ionic‐gelation method. Sodium tripolyphosphate (TPP) as crosslinking agent was added into three kinds of solutions, which were chitosan solution, physical blending solution of chitosan, and glycidyl trimethylammonium chloride (GTMAC), andO‐(2‐hydroxyl) propyl‐3‐trimethyl ammonium chitosan chloride (O‐HTCC) solution respectively. O‐HTCC was synthesized by coupling of GTMAC to chitosan whose functional groups of the NH2groups were protected. The nanoparticles were characterized by transmission electron microscopy, atomic force microscopy, photon correlation spectroscopy, and zeta potential measurement. The results showed that increasing TPP concentration promoted the size of chitosan nanoparticles, a decrease in the size of O‐HTCC nanoparticles incurred on the contrary. The size of O‐HTCC nanoparticles is slightly bigger than that of pure chitosan nanoparticles, and smaller than that of physical blending nanoparticles (PBN). Bovine serum albumin (BSA), as a model protein drug, was incorporated into the nanoparticles. Compared with chitosan nanoparticles and PBN, high BSA loading efficiency (87.5%) and loading capacity (99.5%) are achieved by quaternized chitosan (O‐HTCC) nanoparticles, and the release profile of BSA from nanoparticles has an obvious burst effect and a slowly continuous release phase followed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Mechanical properties and processibilty of glass‐fiber‐, wollastonite‐, and fluoro‐rubber‐reinforced silicone rubber composites
Authors: Park Eun‐Soo
Published: March 2007

The reinforcement of silicone rubber (SR) imparted by different types of fillers was investigated. Glass fiber (GF), wollastonite and fluoro rubber (FR) as nontraditional filler for rubber were compounded SR and mechanical properties of the prepared composites were evaluated. The addition of silane pretreated GF and wollastonite into SR, tensile strength, abrasion resistance and tear strength of the composites improved considerably. The improvement in the properties was assigned to an increased interaction between the filler and the polymer matrix. For the SR/FR composites system, the elongation at break was increase with increasing concentrations of FR due to sponge like structure resulting from poor compatibility between the two components. To investigate the production potential of extrusion processing method, prepared composites were extruded in a rod type sample. During the curing stage, GF, wollastonite and FR lead to the formation of void in the matrix resin. When GF and wollastonite were treated with silane, the void formations were reduced significantly. The silane treatment process improves not only mechanical strength but also processibility of SR composites in dry conditions. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Composite polymer electrolytes based on the low crosslinked copolymer of linear and hyperbranched polyurethanes
Authors: Hong Ling , Shi Liyi
Published: March 2007

Low crosslinked copolymer of linear and hyperbranched polyurethane (CHPU) was prepared, and the ionic conductivities and thermal properties of the composite polymer electrolytes composed of CHPU and LiClO4 were investigated. The FTIR and Raman spectra analysis indicated that the polyurethane copolymer could dissolve more lithium salt than the corresponding polymer electrolytes of the non crosslinked hyperbranched polyurethane, and showed higher conductivities. At salt concentration EO/Li = 4, the electrolyte CHPU30‐LiClO4 reached its maximum conductivity, 1.51 × 10−5 S cm−1 at 25°C. DSC measurement was also used for the analysis of the thermal properties of polymer electrolytes. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3607–3613, 2007
Doping effect of organic sulphonic acids on the solid‐state synthesized polyaniline
Authors: Abdiryim Tursun , Jamal Ruxangul , Nurulla Ismayil
Published: March 2007

Polyaniline (PANI) salts doped with organic sulfonic acids (methanesulfonicacid, p‐toluenesulphonic acid, and dodecylbenzenesulphonic acid) were first synthesized by using solid‐state polymerization method. The polymers were characterized by Fourier transform infrared (FTIR) spectra, ultraviolet‐visible spectrometry, X‐ray diffraction, cyclic voltammetry, scanning electron microscopy, transmission electron microscopy, and conductivity measurements. It was found that PANI doped with p‐toluenesulphonic acid is formed in conductive emeraldine oxidation state, and displayed higher doping level and cyrstallinity. On the contrary, PANI doped with dodecylbenzenesulphonic acid was lower at doping level and highly amorphous. In accordance with these results, the conductivity and electrochemical acitivity was also found to be higher in p‐toluenesulphonic acid‐doped PANI, and these properties were opposite in the case of dodecylbenzenesulphonic acid. The results also revealed that the morphology of dodecylbenzenesulphonic acid‐doped PANI was remarkably different from other PANI salts. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Preparation and characterization of silver containing chitosan fibers
Authors: Qin Yimin , Zhu Changjun , Chen Jie , Zhong Jinhuan
Published: March 2007

Silver containing chitosan fibers were prepared by blending fine particles of a silver sodium hydrogen zirconium phosphate compound into the spinning solution. It was possible to distribute the silver containing particles in the chitosan fiber because of the high viscosity of the spinning solution and the small diameter of the particles. Because the silver ions are imbedded inside the sodium hydrogen zirconium phosphate complex, the chitosan fibers remain white in color without being oxidized by the silver ions. The release of silver ions from the silver containing chitosan fibers were studied by placing the fibers in contact with distilled water, solution A, and aqueous protein solutions. Results showed that the release of silver ions was low in water, while in solution A and protein solutions, the silver ions are activated through ion exchange and chelation. The silver ions can significantly enhance the antimicrobial properties of the chitosan fibers. Experimental results showed that when placed in contact with the silver containing chitosan fibers, the reduction in bacteria count can be more than 98%. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3622–3627, 2007
Chitin sponge, extraction procedure from shrimp wastes using green chemistry
Authors: Flores Ronny , Barrera‐Rodríguez Susana , Shirai Keiko , Durán‐de‐Bazúa Carmen
Published: March 2007

Chitin sponges were obtained from shrimp residues using green chemistry procedures. Partial deproteinization was performed by grinding fresh residues with water during 30 s in a food blender obtaining 39.3% d.b. partial deproteinized cephalothorax (PDC). Protein reduction in this step was 80%, with 49% of mineral salts (measured as ashes), 97% fat, and 41% being chitin product. To separate chitin from PDC, a mixture of 8.75 mL MeOH, 16.25 mL water, and 25 g of CaCl2 was used (solvent MAC) per gram of PDC. Chitin dissolved in MAC under mechanical agitation to form a sponge, which had an overall composition of 42% chitin, 46% ashes, and 11% proteins. Chitin sponge weathering and biodegradation tests showed that during 30 days, the sponge is stable at ambient conditions in southern Mexico City environment, and when placed in compost‐soil mixtures is degraded in about two weeks. These results open new possibilities to the recycling of crustacean residues. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3909–3916, 2007
High performance elastomer composites containing ultra high cis polybutadiene with high abrasion and low rolling resistances
Authors: Kwag Gwanghoon , Kim Pillsung , Han Shin , Lee Seunghwon , Choi Hyungkyu , Kim Sunghyun
Published: March 2007

A series of rubber composites with ultra high cis polybutadiene (UBR), NUC1–3, SBC1–4, SUS1–4, was prepared, and their vulcanized properties were measured and analyzed. The ultra high cis polybutadiene was prepared with the monomeric neodymium catalyst, Nd(neodecanoate)3·(neodecanoic acid). NUC composites were composed of natural rubber, ultra high cis polybutadiene, and carbon black. In the composite of a low carbon black content (NUC1, 45 phr), a high abrasion‐resistance and a significantly low rolling resistance (tan δ60°C, 0.04) were obtained. According to the AFM study of NUC composites, abrasion resistance was closely related with surface morphology. In the SUS composites prepared with SSBR (solution styrene–butadiene copolymer), UBR, and silica, as the content of ultra high cis polybutadiene increased, Δcure torque (MH–ML) increased with fast cure kinetics. SUS4 showed high elongation and tensile strength with excellent abrasion resistance. Rolling resistance was improved as the content of ultra high cis polybutadiene increased. The SBC composites were prepared with SBR (emulsion styrene–butadiene copolymer), ultra high cis polybutadiene (or high cis polybutadiene), and carbon black. It is remarked that abrasion resistance and Δtan δ (tan δ 60°C − tan δ0°C) are increased with ultra high cis polybutadiene. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Subsequent melting behavior of poly(butylene succinate) in its miscible blend with poly(vinyl phenol) crystallized nonisothermally from the melt
Authors: Qiu Zhaobin
Published: March 2007

Biodegradable crystalline poly(butylene succinate) (PBSU) are miscible with amorphous poly(vinyl phenol) (PVPh). Neat PBSU and PBSU blended with PVPh show complex melting behavior after nonisothermal melt crystallization at constant cooling rates. Both neat and blended PBSU can show one, two, or three melting peaks depending on the blend composition, cooling rate, and heating rate. A model was proposed to explain the origin of the complex melting behavior of PBSU through conventional differential scanning calorimetry (DSC) and temperature‐modulated differential scanning calorimetry (TMDSC) studies. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3637–3641, 2007
Mechanism of the particle formation during the oxidative polymerization of 2,6‐dimethylphenol in an aqueous medium
Authors: Liu Qun , Shentu Baoqing , Zhu Jinhua , Weng Zhixue
Published: March 2007

The changes of the molecular weight and particle size with time during the oxidative polymerization of 2,6‐dimethylphenol in an aqueous medium were studied. At the beginning of the oxidative polymerization, the oligomers with the hydrophilic phenoxy anion at the end of oligomer chains are formed rapidly in the aqueous medium. When the molecular weight of the oligomer reaches up to a critical value, the oligomer precipitates out from the water, resulting in the formation of the original particle (or domain). With the increase of the molecular weight, the concentration of the phenoxy anion and the surface charge density of the original particles decrease; therefore, the repulsion force between original particles weaken and the stability of particles in water decreases, resulting in the coagulation of the original particle and the formation of the primary particle. With the further progression of the polymerization, the primary particles coagulate and final particles are formed. A three‐stage mechanism of the particle formation is proposed, that is, the particle nucleation, first coagulation, and second coagulation. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3649–3653, 2007
Modeling the solubility of ternary mixtures of ethylene, iso‐pentane, n‐hexane in semicrystalline polyethylene
Authors: Yao Wenjuan , Hu Xiaoping , Yang Yongrong
Published: March 2007

The coabsorptions of ethylene and iso‐pentane, and ethylene and n‐hexane were measured by the use of a pressure decay method. The solubility data of ethylene‐iso‐pentane and ethylene‐n‐hexane in semicrystalline polyethylene (PE) of crystallinity of 48.6% were obtained at temperatures 70, 80, and 90 °C, and the total pressure 2 MPa, iso‐pentane partial pressure 80–190 KPa, n‐hexane partial pressure 20–90 KPa. The presence of iso‐pentane or n‐hexane in the corresponding ternary system leads to increase the solubility of ethylene, while the solubility of iso‐pentane or n‐hexane remains unchanged with an increase of the ethylene partial pressure, even slightly decreases. Assumed that the presence of iso‐pentane or n‐hexane decreases the crystallinity of the polymer sample, a coabsorption model was built to model the solubility of each gas in the ternary systems. The relative root mean square errors of the coabsorption model for ethylene‐iso‐pentane‐PE system and ethylene‐n‐hexane‐PE system are 5.13% and 4.64%, respectively. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3654–3662, 2007
Dispersing mechanism of carboxymethyl starch as water‐reducing agent
Authors: Zhang Dong‐Fang , Ju Ben‐Zhi , Zhang Shu‐Fen , Yang Jin‐Zong
Published: March 2007

In this article, by using zeta (ζ) potential analyzer, X‐ray photo spectroscopy, and UV–visible adsorption spectrophotometer, the adsorption characteristics and surface electrochemical properties of carboxymethyl starch (CMS) as water‐reducing agent on cement particles and its effects on the fluidity of cement paste were studied in comparison with traditional naphthalene sulfonic acid–formaldehyde condensates, whose dispersion ability mainly depends on electrostatic repulsive force caused by ζ‐potential. The results indicate that the adsorption conformation of CMS is dendritic, generating strong steric hindrance by branched chains and polar side chains of adsorption layer, and the dispersion capacity of CMS mainly comes from steric hindrance effect rather than electrostatic repulsive force. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Synthesis, morphology, component distribution, and mechanical properties of nitrocellulose/gradient poly(ethylene glycol dimethacrylate) semi‐IPN material
Authors: Xiao Zhenggang , Ying Sanjiu , He Weidong , Xu Fuming , Sun Peng
Published: March 2007

Nitrocellulose (NC), a rigid natural polymer, was modified by gradient interpenetrating polymer networks containing poly(ethylene glycol dimethacrylate) (PEGDMA) to obtain both high strength and large toughness across the thickness from surface to the core of samples. PEGDMA content decreased with distance from the surface to core of nitrocellulose with a gradient of poly(ethylene glycol dimethacrylate) (NC/grad. PEGDMA) determined by elemental chemical analysis. The distribution of the guest component across the NC/grad. PEGDMA semi‐IPNs sample thickness was reciprocal function. SEM micrographs of NC/grad. PEGDMA semi‐IPNs revealed that, when the content of guest component was about 23%, the gradient system showed almost single phase morphology. At the same time, the tensile test results showed that NC/grad. PEGDMA featured both higher tensile strength and larger toughness. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Polymerization of styrene using bis(β‐ketoamino)nickel(II)/methylaluminoxane catalytic systems
Authors: Yu Shuxian , He Xiaohui , Chen Yiwang , Liu Yongming , Hong Sanguo , Wu Qing
Published: March 2007

Styrene (St) was polymerized in toluene solution by using bis(β‐ketoamino)nickel(II) complex as the catalyst precursor and methylaluminoxane (MAO) as the cocatalyst. The polymerization conditions, such as Al : Ni ratio, monomer concentration, reaction temperature, and polymerization time, were studied in detail. Both of the bis(β‐ketoamino)nickel(II)/MAO catalytic systems exhibited higher activity for polymerization of styrene, and polymerization gave moderate molecular weight of polystyrene with relatively narrow molecular weight distribution (Mw/Mn < 1.6). The obtained polymer was confirmed to be atactic polystyrene by analyzing the stereo‐triad distributions mm, mr, and rr of aromatic carbon C1 in NMR spectrum of the polymer. The mechanism of the polymerization was also discussed and a metal–carbon coordination mechanism was proposed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Competitive adsorption of uranyl ions in the presence of Pb(II) and Cd(II) ions by poly(glycidyl methacrylate) microbeads carrying amidoxime groups and polarographic determination
Authors: Çaykara Tuncer , Alaslan Şerife Şirin , İnam Recai
Published: March 2007

The adsorption capacity of UO in the presence of Pb(II) and Cd(II) ions was investigated with amidoximated poly(glycidyl methacrylate) (PGMA) microbeads with an average size of 135 μm packed in a glass column (0.5‐cm i.d. and 20‐cm length, flow rate = 3 mL/min) under competitive conditions. A differential pulse polarography technique was used for the determination of trace quantities of uptaken elements by the measurement of the reduction peak currents at −200/−950, −400, and −600 mV (vs a saturated calomel electrode) for UO, Pb(II), and Cd(II) ions, respectively. When only UO was found in the eluate, its adsorption was 85.3% from a 50 μM initial solution. However, when there was UO with binary systems of Pb(II) or Cd(II), it was 78.2 and 76.3%, respectively. On the other hand, in a ternary mixture of UO with Pb(II) and Cd(II), the adsorption was found to be 75.2% with the same initial concentration. According to the results, the competitive adsorption studies showed that these amidoximated PGMA microbeads had good adsorption selectivity for UO with the coexistence of Pb(II) and Cd(II) ions. The ionic strength of the solution also influenced the UO adsorption capacity of the amidoximated PGMA microbeads. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 4168–4172, 2007
Novel tin‐coupled star‐shaped medium vinyl butadiene rubber. II. Vinyl content, molecular weight, and their effects on properties
Authors: Lu Jianmin , Zhang Xingying , Zhao Suhe , Yang Wantai
Published: March 2007

On the basis of our earlier work, extensive experiments were conducted to further investigate the regulating means of vinyl content, molecular weight, molecular weight distribution, and their effects on overall performance of star‐shaped medium vinyl butadiene rubber (S‐MVBR), which was prepared by “core‐first” method with novel multifunctional organolithium as initiator, tetrahydrofuran (THF) as structure regulator, and raffinate oil as solvent. The results showed that vinyl content and molecular weight for one arm were easily regulated from 30 to 55%, 6–10 ten thousand, respectively. The tensile strength and elongation at break increased with increasing vinyl content and the dynamic heating was the lowest at vinyl content of 43%. S‐MVBR had a relatively wide and symmetrical monomodal distribution, which was in favorable of good processing properties. S‐MVBR containing Sn atom, with arm number of 3.8, molecular weight for one arm of eight 10,000, vinyl content of 50%, and distribution of molecular weight of 1.54, had optimal overall properties. When compared with cis‐BR and linear MVBR, S‐MVBR had low rolling energy loss, high wet grip, good mechanical and processing properties. It was an ideal rubber for high performance tire tread. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3924–3930, 2007
Copper‐based reverse ATRP process for the controlled radical polymerization of methyl methacrylate
Authors: Pan Kai , Jiang Long , Zhang Juan , Dan Yi
Published: March 2007

A series of copper‐based reverse atom transfer radical polymerizations (ATRP) were carried out for methyl methacrylate (MMA) at same conditions (in xylene, at 80°C) using N,N,N′,N′‐teramethylethylendiamine (TMEDA), N,N,N′,N′,N′‐pentamethyldiethylentriamine (PMDETA), 2‐2′‐bipyridine, and 4,4′‐Di(5‐nonyl)‐2,2′‐bipyridine as ligand, respectively. 2,2′‐azobis(isobutyronitrile) (AIBN) was used as initiator. In CuBr2/bpy system, the polymerization is uncontrolled, because of the poor solubility of CuBr2/bpy complex in organic phase. But in other three systems, the polymerizations represent controlled. Especially in CuBr2/dNbpy system, the number‐average molecular weight increases linearly with monomer conversion from 4280 up to 14,700. During the whole polymerization, the polydispersities are quite low (in the range 1.07–1.10). The different results obtained from the four systems are due to the differences of ligands. From the point of molecular structure of ligands, it is very important to analyze deeply the two relations between (1) ligand and complex and (2) complex and polymerization. The different results obtained were discussed based on the steric effect and valence bond theory. The results can help us deep to understand the mechanism of ATRP. The presence of the bromine atoms as end groups of the poly(methyl methacrylate) (PMMA) obtained was determined by 1H‐NMR spectroscopy. PMMA obtained could be used as macroinitiator to process chain‐extension reaction or block copolymerization reaction via a conventional ATRP process. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Absorption and release of zinc and copper ions by chitosan fibers
Authors: Qin Yimin , Zhu Changjun , Chen Jie , Liang Di , Wo Gaofeng
Published: March 2007

Chitosan fibers were treated with aqueous solutions of ZnCl2and CuSO4·5H2O to prepare zinc and copper containing fibers, respectively. Significant weight gains were obtained as the zinc and copper ions were absorbed onto the fibers through chelation with the primary amine groups. The fibers were then placed in contact with aqueous solutions containing NaCl and water soluble proteins, respectively, to assess the release of zinc and copper ions. Results showed that the release of zinc and copper ions were affected by the treatment temperature, time, and the composition of the contacting media. More metal ions were released when the fibers were in contact with aqueous protein solutions than in NaCl solution, indicating the binding abilities of the protein molecules for zinc and copper ions. The zinc and copper containing fibers were tested for their antimicrobial effects against several species of bacteria commonly found in wound and skin. Results showed that these metal containing chitosan fibers had much stronger antimicrobial properties than the original chitosan fiber. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Online medium‐throughput respirometry‐based OTR measurements in magnetically stirred cultures
Authors: Brethauer Simone , Held Martin , Panke Sven
Published: March 2007

Intensified bioprocess development requires parallelized medium‐ to high‐throughput experimentation with high on‐ and offline data density across all early scales of the development trajectory from microtiter plate via shake flask to lab‐scale reactor. We developed a widespread measurement principle for intermediate scales, respirometry, into a parallelized oxygen transfer rate measurement device that could accurately record common process development‐relevant effects such as acetate formation, diauxic growth, and nutrient limitations. The device was further equipped with dissolved oxygen measurement capability and sampling ports that allowed repetitive monoseptic sample withdrawal without disturbing the cultivation. Optimization of the operating parameters lead to kL a values of up to 160 h−1 and corresponding oxygen transfer rates of 1 g L−1 h−1 for cultivation volumes of 50 mL. Biotechnol. Bioeng. 2007;98: 356–367. © 2007 Wiley Periodicals, Inc.
Process development for the electroenzymatic synthesis of (R)‐methylphenylsulfoxide by use of a 3‐dimensional electrode
Authors: Lütz S. , Vuorilehto K. , Liese A.
Published: March 2007

The electrogeneration of hydrogen peroxide via reduction of dissolved oxygen was carried out in a three‐dimensional electrochemical cell using graphite grains as cathode material and combined with the enantioselective oxidation of thioanisole to (R)‐methylphenylsulfoxide catalyzed by Chloroperoxidase from Caldariomyces fumago. The relevant parameters for process development (e.g., conductivity of the biotransformation medium) were identified and optimized, leading to an efficient electroenzymatic process with a space‐time yield of 104 g · L−1 · d−1. The isolated product was produced on gram scale (1.2 g, purity >98%, ee > 98.5%). Biotechnol. Bioeng. 2007;98: 525–534. © 2007 Wiley Periodicals, Inc.
Control of hepatic differentiation via cellular aggregation in an alginate microenvironment
Authors: Maguire Tim , Davidovich Alexander E. , Wallenstein Eric J. , Novik Eric , Sharma Nripen , Pedersen Henrik , Androulakis Ioannis P. , Schloss Rene , Yarmush Martin
Published: March 2007

Integral to the development of embryonic stem cell therapeutic strategies for hepatic disorders is the identification and establishment of a controllable hepatic differentiation strategy. In order to address this issue we have established an alginate microencapsulation approach which provides a means to modulate the differentiation process through changes in key encapsulation parameters. We report that a wide array of hepatocyte specific markers is expressed by cells differentiated during a 23‐day period within an alginate bead microenvironment. These include urea and albumin secretion, glycogen storage, and cytochrome P450 transcription factor activity. In addition, we demonstrate that cellular aggregation is integral to the control of differentiation within the bead environment and this process is mediated by the E‐cadherin protein. The temporal expression of surface E‐cadherin and hepatocyte functional expression occur concomitantly and both cellular aggregation and albumin synthesis are blocked in the presence of anti E‐cadherin immunoglobulin. Furthermore, by establishing a compartmental model of differentiation, which incorporates this aggregation phenomenon, we can optimize key encapsulation parameters. Biotechnol. Bioeng. 2007;98: 631–644. © 2007 Wiley Periodicals, Inc.
Determination of catecholamines and serotonin by micellar electrokinetic chromatography with laser‐induced fluorescence detection
Authors: Cao Li‐Wei
Published: March 2007

6‐Oxy‐(N‐succinimidyl acetate)‐9‐(2′‐methoxycarbonyl) fluorescein, a new synthesized fluorescent reagent, was established for the first time as a label for the sensitive analysis of catecholamines (CAs) and serotonin (5‐HT) by micellar electrokinetic chromatography (MEKC) with laser‐induced fluorescence detection. After careful study on the derivatization conditions such as pH value, reagent concentration, temperature and reaction time, the labeling reaction was accomplished as quickly as 7 min with stable yield. The separation parameters for the CAs and 5‐HT were also optimized in detail. The derivatives were baseline separated in a running buffer containing 30 mm boric acid and 15 mm sodium dodeculsulfate at pH 9.0. The detection limits ranged from 5 × 10−10 to 2 × 10−9 m (signal‐to‐noise ratio = 3). The rapid and sensitive method was also applied to the determination of the CAs and 5‐HT of urine samples. Copyright © 2007 John Wiley & Sons, Ltd.
HPLC determination of andrographolide in rat whole blood: study on the pharmacokinetics of andrographolide incorporated in liposomes and tablets
Authors: Suo Xu‐Bin , Zhang Han , Wang Yu‐Qiang
Published: March 2007

A sensitive and simple high‐performance liquid chromatographic method with UV detection was developed and validated for the determination of andrographolide in rat whole blood. Carbamazepine was employed as internal standard and the blood sample was extracted with chloroform. Chromatographic separations were achieved on a Chromasil ODS column (250 × 4.6 mm, 5 µm). The mobile phase was consisted of methanol–water (52:48, v/v) and delivered at 0.8 mL/min. The detection wavelength was set at 225 nm. The calibration curve had a good linearity in the range 0.053–530 µg/mL in rat whole blood with its correlation coefficient being 0.996. The extraction recovery of andrographolide was ranged from 65.7 to 72.6%. The intra‐day and inter‐days repeatabilities were below 4.2% in terms of the percentage of relative standard deviation (RSD). The method was used to provide data on the pharmacokinetics of the drug in rats. The data obtained was processed using the 3P87 pharmacokinetic program. The results showed that the disposition of andrographolide after intravenous administration of liposomal andrographolide conformed to a two‐compartment open model with α = 4.75 × 10−2 ± 2.41 × 10−3 min−1, β = 3.16 × 10−3 ± 1.58 × 10−4 min−1, Vc = 174.67 ± 13.97 mL, k21 = 1.60 × 10−2 ± 8.12 × 10−4 min−1, k10 = 9.38 × 10−3 ± 5.62 × 10−4 min−1, k12 = 2.53 × 10−2 ± 1.27 × 10−3 min−1 and AUC0‐∞ = 1525.47 ± 92.35 µg min/mL. For the intragastric administration of andrographolide tablets, the disposition of andrographolide followed a one‐compartment open model with ke = 6.78 × 10−3 ± 3.53 × 10−4 min−1, ka = 3.69 × 10−2 ± 4.68 × 10−3 min−1, Tmax = 59.69 ± 3.61 min, Cmax = 1.62 ± 0.11 µg/mL, Vc = 1056.90 ± 83.42 mL, AUC0‐∞ = 348.75 ± 24.41 µg min/mL. Copyright © 2007 John Wiley & Sons, Ltd.
Determination of oleanolic acid, ursolic acid and amygdalin in the flower ofEriobotrya japonicaLindl. by HPLC
Authors: Zhou Chunhua , Chen Kunsong , Sun Chongde , Chen Qingjun , Zhang Wangshu , Li Xian
Published: March 2007

Simple and accurate HPLC methods were developed for the determination of oleanolic acid (OA), ursolic acid (UA) and amygdalin in loquat (Eriobotrya japonicaLindl.) flower, which is commonly used for the treatment of various diseases as a traditional Chinese medicine. HPLC assay was performed on a reversed‐phase C18column and all three compounds were detected at 210 nm with a flow rate of 1.0 mL/min. The mobile phase consisted of methanol (A) and 0.03 mol/L phosphate buffer (pH 2.8) (B) with a ratio of 88:12 (A:B, v/v) for simultaneous detection of OA and UA, and 25:75 (A:B, v/v) for detection of amygdalin. The established methods showed good precision and accuracy with overall intra‐day and inter‐day variation of 0.99–3.55 and 1.05–4.05%, respectively, and overall recoveries of 97.37–99.32% for the three compounds. Application of these methods to determine the OA, UA and amygdalin contents in loquat flower showed that cultivar had a minor effect on the contents of all three compounds, with average amounts of 0.38–0.51 mg OA/g dry weight (DW), 2.15–2.68 mg UA/g DW and 1.23–1.56 mg amygdalin/g DW among five loquat cultivars tested. However, developmental stages and flower tissues showed significant effect on the contents of all three bioactive components. Copyright © 2007 John Wiley & Sons, Ltd.
Surface Change of Ras Enabling Effector Binding Monitored in Real Time at Atomic Resolution
Authors: Kötting Carsten , Kallenbach Angela , Suveyzdis Yan , Eichholz Carolin , Gerwert Klaus
Published: March 2007

Ras, the prototype of the Ras superfamily, acts as a molecular switch for cell growth. External growth signals induce a GDP‐to‐GTP exchange. This modifies the Ras surface (RasonGTP) and enables effector binding, which then activates signal‐transduction pathways. GTP hydrolysis, catalysed by Ras and GAP, returns the signal to “off” (RasoffGDP). Oncogenic mutations in Ras prevent this hydrolysis, and thereby cause uncontrolled cell growth. In the Rasoff‐to‐Rason transition, the Ras surface is changed by a movement of the switch I loop that controls effector binding. We monitored this surface change at atomic resolution in real time by time‐resolved FTIR (trFTIR) spectroscopy. In the transition from Rasoff to Rason a GTP‐bound intermediate is now identified, in which effector binding is still prevented (RasoffGTP). The loop movement from RasoffGTP to RasonGTP was directly monitored by the CO vibration of Thr35. The structural change creates a binding site with a rate constant of 5 s−1 at 260 K. A small molecule that shifted the equilibrium from the RasonGTP state towards the RasoffGTP state would prevent effector binding, even if hydrolysis were blocked by oncogenic mutations. We present a spectroscopic fingerprint of both states that can be used as an assay in drug screening for such small molecules.
Differences in right and left ventricular remodeling after transcatheter closure of atrial septal defect among adults
Authors: Wu En‐Ting , Akagi Teiji , Taniguchi Manabu , Maruo Takeshi , Sakuragi Satoru , Otsuki Shinichi , Okamoto Yoshio , Sano Shunji
Published: March 2007

Objectives: To evaluate acute cardiac remodeling after transcatheter closure of atrial septal defect (ASD) in adult patients. Background: In adult patients with ASD, longer periods of cardiac adaptation should be expected after the procedure due to long‐standing RV volume overload and subsequent changes in the pulmonary vasculature. There are limited reports about this remodeling in adult patients. Methods: We prospectively enrolled 17 adults (mean age 58.4 ± 17.3 years) who underwent successful transcatheter closure of their ASDs from August 2005 to July 2006. We performed routine transthoracic echocardiographic studies, including LV and RV myocardial performance indices, or Tei indices, and plasma brain natriuretic peptide (BNP) sampling before closure of the ASD, and 1 day, 1 month, and 3 months after closure. Results: We found (1) LV end diastolic diameter increased, and RVEDD decreased markedly after the closure; (2) differences existed in LV and RV adaptation. While LV Tei index improved soon after the procedure, RV Tei index worsened until 1 month after the procedure, then recovered by the 3 month follow‐up visit; and (3) BNP elevated 1 day after closure of the ASD and declined by the 1‐month follow‐up visit. Conclusion: “Shrinkage” of the RV and “expansion” of the LV occurred soon after the procedure, even in elderly patients. Device closure of ASDs caused rapid improvement of LV function, but RV function underwent transient deterioration, probably due to delayed changes in RV ventricular mass in the face of acute volume reduction in this aged cohort. © 2007 Wiley‐Liss, Inc.
Medical device development: Managing conflicts of interest encountered by physicians
Authors: Baim Donald S. , Donovan Aine , J. Smith John , Briefs Nancy , Geoffrion Richard , Feigal David , Kaplan Aaron V.
Published: March 2007

New technologies introduced over the past three decades have transformed medical diagnosis and treatment, and significantly improved patient outcomes. These changes have been mediated by the introduction of new medical devices, particularly for the treatment of cardiovascular, orthopedic, and ophthalmic disorders. These devices, in turn, have created large markets and spawned a burgeoning medical device industry, including six Fortune 500 companies whose combined market capitalization now exceeds 400 billion dollars. This success story, which has unquestionably benefited patients and society alike, has been dependent upon an intense collaboration among industry, clinicians, and regulatory authorities. However, when physicians actively involve in patient care participate in such collaborations, they are increasingly vulnerable to creating potential conflicts between these two (clinical and device development) roles. Such conflicts, which may ultimately erode public trust, have important consequences not only for the individual physicians, but also for their parent institutions, their patients, sponsoring companies, and the entire clinical research enterprise that makes the development and introduction of new devices possible. The third Dartmouth Device Development Symposium held in October 2005 brought together thought leaders within the medical device community, including academicians, clinical investigators, regulators from the Food and Drug Administration and Centers for Medicare and Medicaid Services (CMS), large and small device manufacturers and the financial (venture capital and investment banks) community. The Symposium examined the conflicts of interest encountered during the early development and commercialization of a medical device. The goal of these discussions was to (1) identify and characterize the conflicts that arise and (2) provide strategies to address these conflicts. This manuscript was prepared by a writing committee to provide a summary report of those discussions. © 2007 Wiley‐Liss, Inc.
Automated alignment of chromatographic data
Authors: Skov Thomas , van den Berg Frans , Tomasi Giorgio , Bro Rasmus
Published: March 2007

This paper focuses on the practical aspects and implications of preprocessing chromatographic data to correct for undesirable time‐shifts. An approach to automate the alignment of chromatographic data based on peak alignment or warping is proposed. This approach deals with selection of the required parameters including selection of reference sample to warp towards, and chooses warping settings based on a new evaluation criterion for goodness of correction. The new criterion aims at quantifying goodness of alignment while at the same time penalising significant shape or area‐changes in the warped peaks. The entire selection procedure is automated using a discrete‐coordinates simplex‐like optimisation routine. Examples with simulated chromatographic data, GC‐FID and HPLC‐Fluorescence measurement series illustrate the potential of using this automated alignment tool. Copyright © 2007 John Wiley & Sons, Ltd.
Unique Ligand‐Based Oxidative DNA Cleavage by Zinc(II) Complexes of Hpyramol and Hpyrimol
Authors: Maheswari Palanisamy Uma , Barends Sharief , Özalp‐Yaman Seniz , de Hoog Paul , Casellas Hélène , Teat Simon J. , Massera Chiara , Lutz Martin , Spek Anthony L. , van Wezel Gilles P. , Gamez Patrick , Reedijk Jan
Published: March 2007

The zinc(II) complexes reported here have been synthesised from the ligand 4‐methyl‐2‐N‐(2‐pyridylmethyl)aminophenol (Hpyramol) with chloride or acetate counterions. All the five complexes have been structurally characterised, and the crystal structures reveal that the ligand Hpyramol gradually undergoes an oxidative dehydrogenation to form the ligand 4‐methyl‐2‐N‐(2‐pyridylmethylene)aminophenol (Hpyrimol), upon coordination to ZnII. All the five complexes cleave the ϕX174 phage DNA oxidatively and the complexes with fully dehydrogenated pyrimol ligands were found to be more efficient than the complexes with non‐dehydrogenated Hpyramol ligands. The DNA cleavage is suggested to be ligand‐based, whereas the pure ligands alone do not cleave DNA. The DNA cleavage is strongly suggested to be oxidative, possibly due to the involvement of a non‐diffusible phenoxyl radical mechanism. The enzymatic religation experiments and DNA cleavage in the presence of different radical scavengers further support the oxidative DNA cleavage by the zinc(II) complexes.
Simple and Efficient Recyclable Catalytic System for Performing Copper‐Catalysed S‐Arylation Reactions in the Presence of Water
Authors: Carril Mónica , SanMartin Raul , Domínguez Esther , Tellitu Imanol
Published: March 2007

A novel protocol for the copper‐catalysed S‐arylation of thiophenol derivatives with aryl halides leading to diaryl sulfides is reported. The reactions were catalysed by a combination of a copper salt and a 1,2‐diamine derivative (acting both as the ligand and as the base) using exclusively water as the solvent. The recovery and successful reutilisation of the aqueous medium containing the active catalyst is described. Furthermore, one example of a “one‐pot” process involving Br/I exchange of an aryl bromide and further S‐arylation is presented.
Intramolecular Spin Alignment in Photomagnetic Molecular Devices: A Theoretical Study
Authors: Ciofini Ilaria , Lainé Philippe P. , Zamboni Marta , Daul Claude A. , Marvaud Valérie , Adamo Carlo
Published: March 2007

Ground‐ and excited‐state magnetic properties of recently characterized π‐conjugated photomagnetic organic molecules are analyzed by the means of density functional theory (DFT). The systems under investigation are made up of an anthracene (An) unit primarily acting as a photosensitizer (P), one or two iminonitroxyl (IN) or oxoverdazyl (OV) stable organic radical(s) as the dangling spin carrier(s) (SC), and intervening phenylene connector(s) (B). The magnetic behavior of these multicomponent systems, represented here by the Heisenberg–Dirac magnetic exchange coupling (J), as well as the EPR observables (g tensors and isotropic A values), are accurately modeled and rationalized by using our DFT approach. As the capability to quantitatively assess intramolecular exchange coupling J in the excited state makes it possible to undertake rational optimization of photomagnetic systems, DFT was subsequently used to model new compounds exhibiting different connection schemes for their functional components (P, B, SC). We show in the present work that it is worthwhile considering the triplet state of anthracene, that is, P when promoted in its lowest photoexcited state, as a full magnetic site in the same capacity as the remote SCs. This framework allows us to accurately account for the interplay between transient (3An) and persistent (IN, OV) spin carriers, which magnetically couple according to a sole polarization mechanism essentially supported by phenyl connector(s). From our theoretical investigations of photoinduced spin alignment, some general rules are proposed and validated. Relying on the analysis of spin‐density maps, they allow us to predict the magnetic behavior of purely organic magnets in both the ground and the excited states. Finally, the notion of photomagnetic molecular devices (PMMDs) is derived and potential application towards molecular spintronics disclosed.
Photophysics and X‐ray Structure of Crystalline 2‐Aminopurine
Authors: Neely Robert K. , Magennis Steven W. , Parsons Simon , Jones Anita C.
Published: March 2007

To explore the effect of intermolecular interactions on the photophysics of 2‐aminopurine (2AP) in a well‐defined environment, we have investigated the fluorescence properties of single 2AP crystals, having determined their X‐ray structure. In the crystal, 2AP is subject to base‐stacking and hydrogen‐bonding interactions similar to those found in DNA. The crystal shows dual fluorescence: π‐stacked molecules in the bulk of the lattice have redshifted excitation and emission spectra, while molecules at defect sites have spectra similar to those of 2AP in solution or in DNA. Heterogeneous intermolecular interactions in the crystal give rise to multiexponential fluorescence decay characteristics similar to those observed for 2AP‐labelled DNA. The presence of about 13 % of the 7H tautomer in the crystal confirms that 9H–7H tautomerisation of 2AP occurs in the ground state. Long‐wavelength excitation of a 2AP‐labelled oligonucleotide duplex produced redshifted emission similar to that observed in the crystal, indicating that π‐stacking interaction of 2AP with nucleobases gives rise to a low energy excited state.
PI3K/Akt and CREB regulate adult neural hippocampal progenitor proliferation and differentiation
Authors: Peltier Joseph , O'Neill Analeah , Schaffer David V.
Published: March 2007

The phosphoinositide 3‐OH kinase (PI3K)/Akt pathway has been implicated in regulating several important cellular processes, including apoptosis, survival, proliferation, and metabolism. Using both pharmacological and genetic means, we demonstrate here that PI3K/Akt plays a crucial role in the proliferation of adult hippocampal neural progenitor cells. PI3K/Akt transduces intracellular signals from multiple mitogens, including basic fibroblast growth factor (FGF‐2), Sonic hedgehog (Shh), and insulin‐like growth factor 1 (IGF‐1). In addition, retroviral vector‐mediated over‐expression of wild type Akt increased cell proliferation, while a dominant negative Akt inhibited proliferation. Furthermore, wild type Akt over‐expression reduced glial (GFAP) and neuronal (β‐tubulin III) marker expression during differentiation, indicating that it inhibits cell differentiation. We also show that activation of the cAMP response element binding protein (CREB), which occurs in cells stimulated by FGF‐2, is limited when Akt signaling is inhibited, demonstrating a link between Akt and CREB. Over‐expression of wild type CREB increases progenitor proliferation, whereas dominant negative CREB only slightly decreases proliferation. These results indicate that PI3K/Akt signaling integrates extracellular signaling information to promote cellular proliferation and inhibit differentiation in adult neural progenitors. © 2007 Wiley Periodicals, Inc. Develop Neurobiol, 2007.