Search

Actin linked regulatory mechanisms are known to contribute contraction/relaxation in smooth muscle. In order to clarify whether modulation of polymerization/depolymerization of actin filaments affects relaxation process, we examined the effects of cytochalasin D on relaxation process by Ca.sup.2+ removal after Ca.sup.2+-induced contraction of [beta]-escin skinned (cell membrane permeabilized) taenia cecum and carotid artery preparations from guinea pigs. Cytochalasin D, an inhibitor of actin polymerization, significantly suppressed the force during relaxation both in skinned taenia cecum and carotid artery. The data fitting analysis of the relaxation processes indicates that cytochalasin D accelerates slow (latch-like) bridge dissociation. Cytochalasin D seems to directly disrupts actin filament organization or its length, resulting in modulation of actin filament structure that prevents myosin binding. Keywords: Cytochalasin D, Actin, Smooth muscle, Skinned preparation, Relaxation, Author(s): Satoko Mihashi[sup.1] and Masaru Watanabe[sup.1] Background Regulatory mechanisms of contractility in vertebrate smooth muscle are thought to be different from that in striated muscle. In smooth muscle, the contractile [...]

Polymethylmethacrylate-co-methacrylic acid (PMMA-co-MAA) was utilized for surface improvement of silica to be used as reinforcement in self-healing natural rubber based on metal thiolate ionic network. The amount of PMMAco-MAA was varied at 1, 3, and 5 wt% of silica content and the optimized PMMA-co-MAA was utilized to investigate the self-healing NR/silica composites at different filler loading (5, 10, 20, and 30 phr). The graft polymerization of PMMA-co-MAA on silica was confirmed using FTIR spectroscopy and grafting percentage was determined by thermogravimetric analysis (TGA). Intermolecular diffusion occurred at the fractured area was detected using a scanning electron microscope (SEM) and the results revealed that the composite tensile and tear performance increased 22%-70% with healing efficiency percentage ranging between 70% and 97% depending on the silica loading. KEYWORDS Methacrylic acid, modified silica, natural rubber composites, reversible ionic network, self-healing, 1 | INTRODUCTION Natural rubber (NR) is an important raw material used in numerous industries, including the automotive, sporting goods, medical, and electrical fields. Their exceptional qualities, including strong chemical [...]

Polymer metal nano-composites (PMNC) were synthesized by integrating different weight percentage of chitosan (CS), N,N'-methylenebisacrylamide (MBA) crosslinked poly(aciylic acid-co-hydroxyethyl methacrylate) copolymer and Cu nanoparticles (CuNPs). CuNPs were generated in situ during polymerization by reducing CuS[O.sub.4].5[H.sub.2]O with ascorbic acid. The presence of the CuNPs in the polymer network, functionality, crystallinity, morphology, size distribution of the CuNPs, elemental composition, thermal characteristics, network parameters, pH sensitivity, and strength of the composites was evaluated. The CuNP-loaded PMNC4 composite prepared with 10:1 acrylic acid : hydroxyethyl methacrylate molar ratio, 1 wt% each of initiator and MBA crosslinker and 4 wt% CS showed a photodegradation efficiency of 64% in 5 h for 50 mg/L methyl violet dye in water. The same polymer showed a rejection of 91.45% and a mass transfer coefficient of 4.14 * [10.sup.-5] cm/s for continuous adsorption of 20 mg/L Pb(II) ion in water in a fixed bed of height 22 mm for an inflow rate of 30 ml/min. KEYWORDS chitosan, column adsorption of Pb(II) from water, composite adsorbent, copolymer, CuNP, photocatalytic reduction, 1 | INTRODUCTION Nanometals of Ag, Au, Pd, Pt, Co, Ni, and Cu were reported as very efficient catalyst for reduction of organic pollutants such as synthetic dyes [1,2] and [...]

In-mold coating (IMC) being 100% solids upon polymerization is an environmentally friendly alternative to traditional painting/coating. The standard commercial IMC formulation contains 2.8 wt% carbon black (CB) to achieve the electrical conductivity needed for maximum transfer efficiency during electrostatic painting. This formulation, however, makes the primed surface deep black and significantly increases the viscosity. To address this issue, our previous research evaluated the use of single-wall carbon nanotubes as an alternative to CB. It was found that IMC with 0.15 wt% SWCNT provides the same level of conductivity as the standard IMC, but a much clear coating. However, the processability of this new formulation was adversely affected. In this research, other carbon-based materials, that is, carbon nanofiber (CNF), multiwall carbon nanotube (MWCNT), and industrial graphene (grapheneblack [G]), were evaluated. Results indicate that the same level of conductivity can be reached by adding 1.6 wt% CNF, 1.8 wt% MWCNT, or 11.3 wt% G. Results also suggest that IMC with 1.8 wt% MWCNT has the best curing process, IMC with 11.3 wt% G has the highest flowability, and all three new formulations have a slightly better greyscale reading than the standard IMC. KEYWORDS carbon-based nanoparticles, in-mold coating, multi-criteria optimization, 1 | INTRODUCTION In recent years, sheet molding compound (SMC) has been broadly used in automotive and aerospace industries, due to its high strength to weight ratio and cosmetic appeal. [...]

In this article, we study the process of polymerization of a modified ED-20 epoxy binder under conditions of highly filled systems. It is found that modifying additives affect the process of polymerization of the binder, increasing the degree of conversion of epoxy groups of ED-20 resin, speeding up the process of polymerization, and increasing the exothermic effect of the reaction. Curing in the presence of a modifying silicon-containing additive takes place in a mode that promotes the formation of a more ordered structure, creating opportunities for relaxation of internal stresses and favorable conditions for the formation of an ordered microstructure. The equations sufficiently fitting the measured points of the concentration of epoxy groups are calculated. We obtain the kinetic curves of curing, which illustrate the process of heat release of the ED-20 binder and the same system modified with mineral fillers. It is found that the heat release occurs more intensively when modifiers are introduced into the epoxy binder. It is derived that the experimental data of kinetics of heat release at considered time range can be sufficiently described by a parabolic equation. KEYWORDS composite, degree of conversion, epoxy resin, fillers, polymerization, 1 | INTRODUCTION Epoxy resins are widely used in construction as adhesive, potting, insulating materials, and binders for filled compositions for repair. [1, 2] The properties of epoxy composites can [...]

A poly(vinylpyrrolidone) end-functionalized with a carboxylic acid group (PVP-[CO.sub.2]H) was synthesized by reversible addition-fragmentation chain transfer (RAFT)/macromolecular design via the interchange of xanthates (MADIX) polymerization mediated by 4-(O-ethylxanthyl)methyl benzoic acid. The molecular weight of the as-synthesized PVP-[CO.sub.2]H was estimated through UV-vis spectroscopy ([M.sub.n(UV-vis)] = 7322 g/mol), gel permeation chromatography (GPC) ([M.sub.n(GPC)] = 8670 g/mol), and [.sup.1]H NMR, ([M.sub.n(NMR)] = 8207 g/mol). The values obtained were close with the theoretical molecular weight ([M.sub.n(th)] = 7925 g/mol). Subsequently, the preformed PVP-[CO.sub.2]H was activated to produce N-succinimidyl poly(vinylpyrrolidone) (PVP-NHS). This precursor was covalently coupled to papain to produce bioconjugate PVP-papain. The functional group modifications in the PVP chain-end were observed by the variations in the chemical shift values by [.sup.1]H and [.sup.13]C NMR and FTIR analysis at each step of the synthesis. The molecular weight of the PVP-papain was obtained by SEC-HPLC and suggests that, on average, four or five chains of PVP-[CO.sub.2]H were attached to one papain molecule. Compared with papain, the PVP-papain exhibited significantly improved catalytic activity, pH, and thermal stability. Additionally, the storage studies showed that the catalytic activity of PVP-papain was about 79% versus the native enzyme (29%), and this activity was maintained even when it was stored for 25 days. Key words: RAFT/MADIX N-vinylpyrrolidone, papain bioconjugation, enzymatic activity, NMR characterization. Nous avons synthetise une poly(vinylpyrrolidone) dont le groupe terminal est une fonction acide carboxylique (PVP-[CO.sub.2]H) par la technique RAFT (polymerisation radicalaire controlee par transfert de chaine reversible par addition-fragmentation)/MADIX (design macromoleculaire par echange de xanthates) facilitee par l'acide 4-(O-ethylxanthyl)methylbenzoique. Le poids moleculaire de la PVP-[CO.sub.2]H synthetisee telle quelle a ete estime par spectroscopie UV-vis ([M.sub.n(UV-vis)] = 7322 g/mol), chromatographie sur gel permeable (GPC) ([M.sub.n(GPC)] = 8670 g/mol) et RMN [.sup.1]H ([M.sub.n(RMN)] = 8207 g/mol). Les valeurs obtenues etaient proches du poids moleculaire theorique ([M.sub.n(th)] = 7925 g/mol). Par la suite, la PVP-[CO.sub.2]H prealablement formee a ete activee pour produire la N-succinimidylpoly(vinylpyrrolidone) (PVP-NHS). Nous avons ensuite fixe ce precurseur a la papaine par couplage covalent pour produire le bioconjugue PVP-papaine. Les variations des valeurs de deplacement chimique en RMN [.sup.1]H et [.sup.13]C et l'analyse des spectres FTIR ont permis de constater les modifications du groupe fonctionnel a l'extremite de chaine de la PVP a chaque etape de la synthese. Nous avons pu estimer le poids moleculaire du bioconjugue PVP-papaine par chromatographie d'exclusion sterique en phase liquide a haute performance (SEC-HPLC), et les resultats semblent indiquer que quatre ou cinq chaines de PVP-[CO.sub.2]H, en moyenne, sont fixees a une molecule de papaine. Comparativement a la papaine, le bioconjugue PVP-papaine a montre une amelioration significative de l'activite catalytique, de la stabilite au pH et de la stabilite thermique. Les etudes de conservation ont egalement revele que l'activite catalytique du bioconjugue PVP-papaine etait d'environ 79%, par rapport a celle de l'enzyme native, qui etait de 29%, et que cette activite etait maintenue meme lorsque le bioconjugue etait entrepose pendant 25 jours. [Traduit par la Redaction] Mots-cles : polymerisation RAFT/MADIX de la N-vinylpyrrolidone, bioconjugaison de la papaine, activite enzymatique, caracterisation par RMN., Introduction The chemical modification of enzymes through bioconjugation with biological or synthetic polymers is an excellent strategy for enhancement of enzymatic activity and stability, and in some cases, it can [...]

The effect of graphene oxide (GO) loading (0.03, 0.06, 0.09, 0.12, and 0.30 wt%) in the aqueous phase on the performance of reverse osmosis (RO) polyimide (PI) thin film composite (TFC) membrane was investigated. TFC and thin film nanocomposite (TFN) membranes were produced through interfacial polymerization and the imide linkage was confirmed by attenuated total reflection Fourier transform infrared spectroscopy. The spongy-like structure with vertical fingers of RO PI-GO TFN membranes was explored by top-surface and cross-sectional field emission scanning electron microscope (FE-SEM). The roughness of the membranes was determined. All PI-GO TFN membranes exhibited enhanced desalination performance in comparison with PI membranes. Samples with 0.06 wt% GO performed the best with a water flux of 31.80 L/[m.sup.2]/h, salt rejection of 98.8%, and very good antibiofouling properties. This hydrophilic membrane displayed significantly enhanced chlorine-resistance with water flux of 36.3 L/[m.sup.2]/h and salt rejection of 98.5%. This work provides a promising start for designing rapid water permeation PI-GO TFN membranes in water desalination. KEYWORDS biofouling, chlorine-resistant, graphene oxide, polyimide membrane, thin film composite, thin film nanocomposite, water desalination, 1 | INTRODUCTION An industrially beneficial reverse osmosis (RO) membrane must have considerable features that enhance the desalination performance such as chlorine and fouling resistances, high water flux, high salt [...]

A kinetic model was proposed to describe hyperbranched polymers (HBPs) formed by the polymerization of monomers [A.sub.2] and [B.sub.3] with monofunctional compound (BR) added gradually in a semibatch reactor. The dependences of the degree of polymerization (DP) and the degree of branching on the reaction time and the monomer compositions were calculated. The DP of the HBPs could be increased by the slow addition of BR in the reactor. If the monomers [B.sub.3] and [A.sub.2] were mixed at a molar ratio of [B.sub.3]:[A.sub.2] = 1:3, and the BR was fed slowly into the reactor, the HBPs with weight average DP were approximately 3200 and 16 700 at conversion of 0.95 and 0.99, respectively, which were higher than those prepared by the batch system. This theory was further verified by an experimental demonstration. Hyperbranched polyurethane acrylate can be synthesized with a higher DP in a semibatch system than in a batch reactor. KEYWORDS hyperbranched polymer, kinetic model, polyurethane acrylate, semibatch system, 1 | INTRODUCTION Polymers with highly branched structures, such as dendrimers and hyperbranched polymers (HBPs), have many pending, peripheral, or side functional groups, thus they have many unique characteristics, which [...]

Styrene has been polymerized to syndiotactic polystyrene (sPS) over a layer of heterogeneous Cp*Ti[(OC[H.sub.3]).sub.3]/MAO catalyst immobilized onto the surfaces of silica nanotube reactor (SNTR) arrays of 60-200 nm in diameter. The polymer produced in the SNTR arrays has been found to have the molecular weights much larger than the polymers synthesized by a liquid slurry polymerization over silica-supported catalysts. A dynamic reactor model that consists of diffusion and reaction terms has been derived and solved to quantify the kinetics of styrene polymerization in a single nanotube reactor. The two-site kinetic model applied to the silica nanotube reactor model shows that the experimentally observed high polymer molecular weight can be fitted if the chain transfer rate constants for monomer and fl-hydride elimination are reduced significantly. The simulation results suggest that the presence of dense crystalline sPS nanofibrils filling the nanotubes constrain the molecular movements of polymer chain ends in the proximity of catalyst sites to limit the chain transfer reactions., INTRODUCTION Syndiotactic polystyrene (sPS) is an interesting high-performance engineering polymer derived from styrene. The structure and properties of sPS are totally different from those of general purpose polystyrene (gPS) derived [...]

A simple but comprehensive model considering homogeneous and micellar nucleation, coagulation, entry of radicals to particles and to micelles and radicals' exit from particles, is presented. The model is validated, in a starved semicontinuous heterophase polymerization of ethyl methacrylate, at three monomer addition rates. The model accurately describes the overall and instantaneous conversion, the average particle density and diameter, and the number and weight average molar masses evolutions over time. It is found that even though the average number of radicals is much smaller than 0.5, the system is not 0-1. An empirical function was used to describe the gel effect. The homogeneous nucleation was the prevailing mechanism for particle formation and large exit rates of radicals were observed., INTRODUCTION Polymeric nanoparticles have attracted increasing attention during the last decades. This is because of their unique properties and behavior, arising from their small size. Rigorously speaking, nanomaterials are structures [...]

Fulvic acid-thiourea amide derivates (FA-T) was synthesized via amidation with FA and thiourea, and its optimum reaction conditions were 7 h of reaction time, 1 wt% of sodium methylate, 130[degrees]C of reaction temperature, and 2 g of thiourea. Then, FA-T grafted polystyrene (FA-T-PS) was synthesized by activators generated by electron transfer for atom transfer radical polymerization. Fourier transform infrared spectroscopy, static contact angle analysis, and X-ray photoelectron spectroscopy confirmed that the synthesis of FA-T-PS. Then, poly(lactic acid)/FA-T-PS (PLA/FA-T-PS) composites were prepared by the melt blending with FA-T-PS as fillers. Mechanical test demonstrated that FA-T-PS increased the flexibility and ductility of PLA composites. Dynamic mechanical analysis revealed that FA-T-PS reduced friction and loss between PLA chain and filler, and further reformed had higher interfacial compatibility with PLA. Differential scanning calorimetric results and polarized optical microscopy analysis displayed that FA-T-PS had strong heterogeneous nucleation effect, which effectively enhanced the crystallization rate and the crystallinity of PLA. Friedman thermal decomposition kinetics presented that Ea of PLA/FA-T-PS (0.3 wt%) was increased by 52.94% compared with PLA, which demonstrated that FA-T-PS significantly enhanced the thermal stability of PLA. Therefore, FA-T-PS effectively improved the comprehensive performance of PLA., INTRODUCTION Poly(lactic acid) (PLA) is one of the representative biodegradable polymers in the world [1]. Unlike traditional petroleum-based polymers, the industrial production of PLA requires very little fossil energy, so [...]

This review aims to provide a concise insight into the rapidly growing anionic ring-opening copolymerization of nylon 6/12 and its related structures. This study analyzes the relationship between the structures of polymerization components and the relevant properties to achieve optimum copolymerization formulation. Specific emphasis is placed on how the catalyst type and temperature influence the final copolymer structure. The present work reviews available literature about nylon 6/12 synthesis published between 1960 and 2017 and investigates structures linked to polymerization mechanisms behind them. Moreover, experimental results derived from direct/indirect identification methods of structures are presented. The crystalline morphology of different structures was also evaluated. The thermal behaviors of synthesized copolymers are explored comprehensively. Finally, mechanical properties alteration and enhanced water absorption results are reported., INTRODUCTION Both ring-opening polymerization and copolymerization of cyclic amides (lactams) are of commercial interest for their use in a wide variety of applications [1-5]. Lactam polymerization can be initiated not [...]

Environmental and economic considerations have made the sorption of uranium from aqueous media a very time demanding area of research from last few decades. In this particular work, amidoximated polyacrylonitrile beads were synthesized by the reaction of hydroxyl amine hydrochloride (OH-N[H.sub.2].HCI) with macroporous crosslinked polyacrylonitrile beads, prepared through suspension polymerization techniques, using acrylonitrile (AN) as monomer and divinylbenzene and ethyleneglycoldimethacrylate as crosslinkers, in a variety of relative compositions, to modify suitably the hydrophilicity and physicochemical stability. These beads were also characterized by FT-IR, scanning electron microscope, and thermogravimetric analysis--differential scanning calorimetry techniques to explain the morphology and chemical functionality. The beads reached its saturation capacity towards uranyl ions well within 1 h of equilibration at ~25[degrees]C, under near neutral pH conditions and the observed maximum sorption capacity was found to be -18 mg [g.sup.-1]. The beads were also used for the sorption of uranium from various real water samples and showed good sorption from these samples. Reusability of the beads was also established up to the studied four cycles. These synthesized beads can potentially serve the dual purpose of the decontamination of uranium contaminated potable well water as well as to treat acidic radioactive waste generated in nuclear industry before final discharge to environment., INTRODUCTION Uranium is found in the natural environment as in rocks, soil and water in very low concentration. According to an estimate [1]. about 4.5 billion tons of uranium is [...]

Mutations in laminin [alpha]2-subunit (Lm[alpha]2, encoded by LAMA2) are linked to approximately 30% of congenital muscular dystrophy cases. Mice with a homozygous mutation in Lama2 (dy2J mice) express a nonpolymerizing form of laminin-211 (Lm211) and are a model for ambulatory-type Lm[alpha]2-deficient muscular dystrophy. Here, we developed transgenic dy2J mice with muscle-specific expression of [alpha]LNNd, a laminin/nidogen chimeric protein that provides a missing polymerization domain. Muscle-specific expression of [alpha]LNNd in dy2J mice resulted in strong amelioration of the dystrophic phenotype, manifested by the prevention of fibrosis and restoration of forelimb grip strength. aLNNd also restored myofiber shape, size, and numbers to control levels in dy2J mice. Laminin immunostaining and quantitation of tissue extractions revealed increased Lm211 expression in [alpha]LNNd-transgenic dy2J mice. In cultured myotubes, we determined that [alpha]LNNd expression increased myotube surface accumulation of polymerization-deficient recombinant laminins, with retention of collagen IV, reiterating the basement membrane (BM) changes observed in vivo. Laminin LN domain mutations linked to several of the Lm[alpha]2-deficient muscular dystrophies are predicted to compromise polymerization. The data herein support the hypothesis that engineered expression of [alpha]LNNd can overcome polymerization deficits to increase laminin, stabilize BM structure, and substantially ameliorate muscular dystrophy., Introduction Laminin-211 ([alpha]2[beta]i[gamma]1 subunits, abbreviated herein as Lm211) is the major laminin of the basement membrane (BM) of skeletal muscle and peripheral nerve Schwann cells. Mutations within the LAMA2 gene [...]