In the presence of dicumyl peroxide (DCP), biobased thermoplastic vulcanizates (TPVs) composed of poly(lactic acid) (PLA) and epoxidized natural rubber (ENR) were prepared through dynamic vulcanization. Interfacial in situ compatibilization between PLA and ENR phases was confirmed by Fourier transform infrared spectroscopy (FT-IR). A novel "sea-sea" co-continuous phase in the PLA/ENR TPVs was observed through scanning electron microscopy (SEM) and differed from the typical "sea-island" morphology that cross-linked rubber particles dispersed in plastic matrix. A sharp, brittle-ductile transition occurred with 40 wt % of ENR, showing a significantly improved impact strength of 47 kJ/m(2), nearly 15 times that of the neat PLA and 2.6 times that of the simple blend with the same PLA/ENR ratio. Gel permeation chromatography (GPC) and dynamic mechanical analysis (DMA) results suggested that a certain amount of DCP was consumed in the PLA phase, causing a slight cross-linking or branching of PLA molecules. the effects of various DCP contents on the impact property were investigated. The toughening mechanism under impact testing was researched, and the influence factors for toughening were discussed.

.-In live cells, autoactivation of matriptase, a membrane-bound serine protease, can be induced by lysophospholipids, androgens, and the polyanionic compound suramin. These structurally distinct chemicals induce different signaling pathways and cellular events that somehow, in a cell type-specific manner, lead to activation of matriptase immediately followed by inhibition of matriptase by hepatocyte growth factor activator inhibitor 1 (HAI-1).In the current study, we established an analogous matriptase autoactivation system in an in vitro cell-free setting and showed that a burst of matriptase activation and HAI-1-mediated inhibition spontaneously occurred in the insoluble fractions of cell homogenates and that this in vitro activation could be attenuated by a soluble suppressive factor(s) in cytosolic fractions. Immunofluorescence staining and subcellular fractionation studies revealed that matriptase activation occurred in the perinuclear regions. Solubilization of matriptase from cell homogenates by Triton X-100 or sonication of cell homogenates completely inhibited the effect, suggesting that matriptase activation requires proper lipid bilayer microenvironments, potentially allowing appropriate interactions of matriptase zymogens with HAI-1 and other components. Matriptase activation occurred in a narrow pH range (from pH 5.2 to 7.2), with a sharp increase in activation at the transition from pH 5.2 to 5.4, and could be completely suppressed by moderately increased ionic strength. Protease inhibitors only modestly affected activation, whereas 30 nM (5 g/ml) of anti-matriptase LDL receptor domain 3 monoclonal antibodies completely blocked activation. These atypical biochemical features are consistent with a mechanism for autoactivation of matriptase that requires protein-protein interactions but not active proteases.hepatocyte growth factor activator inhibitor 1; protease activation; low-density lipoprotein MATRIPTASE AND HEPATOCYTE growth factor activator inhibitor 1 (HAI-1) are a pair of epithelium-derived, membrane-associated proteins: a proteolytic enzyme and its cognate inhibitor, respectively (22, 49). Matriptase, a member of the type II transmembrane serine protease (8,35,50), contains a transmembrane domain at the amino terminus, followed by a sperm protein, enterokinase, and agrin (SEA) domain, two tandem C1r/s, Uegf, and bone morphogenic protein-1 (CUB) domains, four tandem LDL receptor class A domains, and a trypsin-like serine protease domain (15,22,23,52,54). HAI-1, a type 1 transmembrane protein, contains two Kunitz-type serine protease inhibitor domains and an LDL receptor class A domain (46). Matriptase and HAI-1 are broadly expressed and may have diverging functions in the epithelial cells of most epithelium-containing tissues (15,22,26,36,39,52,54). For example, matriptase was shown to be required for postnatal survival, epidermal barrier function, hair follicle development, and thymic homeostasis in matriptase knockout mice (25). The roles of matriptase in epidermal differentiation apparent...

The detailed mechanism by which ethylene polymerization is initiated by the inorganic Phillips catalyst (Cr/SiO 2 ) without recourse to an alkylating co-catalyst remains one of the great unsolved mysteries of heterogeneous catalysis. Generation of the active catalyst starts with reduction of Cr VI ions dispersed on silica. A lower oxidation state, generally accepted to be Cr II , is required to activate ethylene to form an organoCr active site. In this work, a mesoporous, optically transparent monolith of Cr VI /SiO 2 was prepared using sol-gel chemistry in order to monitor the reduction process spectroscopically. Using in situ UV-vis spectroscopy, we observed a very clean, step-wise reduction by CO of Cr VI first to Cr IV , then to Cr II . Both the intermediate and final states show XANES consistent with these oxidation state assignments, and aspects of their coordination environments were deduced from Raman and UV-vis spectroscopies. The intermediate Cr IV sites are inactive towards ethylene at 80 °C. The Cr II sites, which have long been postulated as the endpoint of CO reduction, were observed directly by high-frequency/high-field EPR spectroscopy. They react quantitatively with ethylene to generate the organoCr III active sites, characterized by X-ray absorption and UV-vis spectroscopy, which initiate polymerization.

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A novel signaling pathway consisting of Gai, PLC, PKCβ, PKD, SSH2, and cofilin is crucial for GPCR-mediated chemotaxis in neutrophils. This pathway regulates depolymerization of the actin network that drives the directional migration of neutrophils.

Background Frequent premature ventricular contractions (PVCs) are associated with increased risk for sudden cardiac death (SCD) and can cause secondary cardiomyopathy (CM). Objective We sought to determine the mechanism(s) responsible for prolonged refractory period and LV dysfunction demonstrated in our canine model of PVC-induced CM. Methods Single myocytes were isolated from LV free wall of PVC and control canines, and used for patch clamp recording, [Ca]i measurements and immunocytochemistry/confocal microscopy. LV tissues adjacent to area of myocyte isolation were used for immunoblot quantification of protein expression. Results In PVC group, LVEF declined from 57.6±1.5% to 30.4±3.1% after ≥ 4 months of ventricular bigeminy. Compared to control myocytes, PVC myocytes had reduced densities of both outward (Ito and IK1) and inward (ICaL) currents, but no consistent changes in IKr or IKs. The reduction in Ito, IK1 and ICaL was accompanied by decreased protein levels of their channel subunits. The degrees of reduction in Ito, IK1 and ICaL varied among PVC myocytes, creating marked heterogeneity in action potential (AP) configurations and durations. PVC myocytes showed impaired Ca-induced Ca release from SR, without increase in SR Ca leak or decrease in SR Ca store. This was accompanied by a decrease in dyad scaffolding protein, junctophilin-2, and loss of Cav1.2 registry with Ca-releasing channels (RyR2). Conclusion PVCs increase dispersion of AP configuration/duration, a risk factor for SCD, due to heterogeneous reduction in Ito, IK1 and ICaL. The E-C coupling is impaired due to decrease in ICaL and Cav1.2 misalignment with respect to RyR2.

The structure and mechanism of the formation of sites which initiate ethylene polymerization in the atomically dispersed Phillips catalyst (Cr/ SiO 2 ) are two of the great unsolved mysteries of heterogeneous catalysis. After CO or C 2 H 4 reduction of silica-supported Cr VI ions to Cr II ions in the precatalyst, exposure to ethylene results in the formation of organoCr III sites that are capable of initiating polymerization without recourse to an external alkylating cocatalyst. In this work, a Phillips catalyst prepared, via sol−gel chemistry, as a mesoporous, optically transparent monolith was reduced with CO to the spectroscopically determined Cr II end point. Ethylene causes rapid reoxidation of these Cr II sites to Cr III , even at low temperatures. Solid-state 13 C CP-MAS NMR, IR, and Raman spectroscopies reveal that the resulting sites contain a vinyl ligand, described as (≡SiO) 2 Cr III −CHCH 2 although likely with a higher coordination number, which are capable of initiating polymerization. The formation of these vinyl sites is an incommensurate redox reaction involving one-electron oxidation of Cr II via ethylene disproportionation. The accompanying formation of organic radical intermediates and their characteristic reaction products suggest that the key step is homolysis of a Cr−ethyl bond. Plausible pathways for the initiation mechanism are suggested.

A biobased heat-triggered shape memory polymer (HSMP) consisting of polylactide (PLA) and epoxidized natural rubber (ENR) was fabricated by peroxide-induced dynamic vulcanization. The crosslinked ENR phase exhibits a continuous net-like structure embedded in the PLA phase, which is different from conventional plastic/rubber system having typically "sea-island" morphology in which vulcanized rubber particles dispersed in plastic matrix. In-situ interfacial compatibilization was confirmed by FTIR analysis. The shape recovery ratios of the PLA/ENR HSMPs were significantly improved over 90%, compared to that (60~70%) of PLA. The shape fixing and memorizing capability of PLA/ENR HSMPs was realized by the glass transition of PLA phase: crosslinked ENR continuous phase at rubbery state offered strong recovery driving force, improved interface provided effective stress-transferring during shape recovery and PLA continuous phase served as a "control-switch" for recovery. The biobased PLA/ENR HSMP could serve as a promising alternative to the traditional materials for intelligent biomedical devices.