Effective activation of metallocene catalysts with supported‐type Ph3CClO4 in ethylene polymerization

Supported type cocatalysts using triphenylcarbenium perchlorate (Ph₃CClO₄) were prepared by impregnation on inorganic carrier, magnesium chloride (MgCl₂) and applied to ethylene polymerizations with rac‐Et[Ind]₂ZrCl₂. Homogeneous polymerizations with Ph₃CClO₄ were also carried out for comparison. The activity of homogeneous polymerization was much lower than that obtained with methylaluminoxane (MAO). On the other hand, rac‐Et[Ind]₂ZrCl₂ activated by the supported type Ph₃CClO₄/MgCl₂ system displayed high activity comparable to that obtained with MAO. From the results of fractionation and polymerization of the rac‐Et[Ind]₂ZrCl₂‐Ph₃CClO₄/MgCl₂ catalyst system, it was found that the increased activity mainly came from the active species in the supernatant part. UV‐vis spectroscopic measurements combined with ICP analysis indicate that the active species in the supernatant fraction are composed of a stoichiometric amount of perchlorate and metallocene catalyst.     

Inducible Prmt1 ablation in adult vascular smooth muscle leads to contractile dysfunction and aortic dissection

Vascular smooth muscle cells (VSMCs) have remarkable plasticity in response to diverse environmental cues. Although these cells are versatile, chronic stress can trigger VSMC dysfunction, which ultimately leads to vascular diseases such as aortic aneurysm and atherosclerosis. Protein arginine methyltransferase 1 (Prmt1) is a major enzyme catalyzing asymmetric arginine dimethylation of proteins that are sources of asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide synthase. Although a potential role of Prmt1 in vascular pathogenesis has been proposed, its role in vascular function has yet to be clarified. Here, we investigated the role and underlying mechanism of Prmt1 in vascular smooth muscle contractility and function. The expression of PRMT1 and contractile-related genes was significantly decreased in the aortas of elderly humans and patients with aortic aneurysms. Mice with VSMC-specific Prmt1 ablation (smKO) exhibited partial lethality, low blood pressure and aortic dilation. The Prmt1-ablated aortas showed aortic dissection with elastic fiber degeneration and cell death. Ex vivo and in vitro analyses indicated that Prmt1 ablation significantly decreased the contractility of the aorta and traction forces of VSMCs. Prmt1 ablation downregulated the expression of contractile genes such as myocardin while upregulating the expression of synthetic genes, thus causing the contractile to synthetic phenotypic switch of VSMCs. In addition, mechanistic studies demonstrated that Prmt1 directly regulates myocardin gene activation by modulating epigenetic histone modifications in the myocardin promoter region. Thus, our study demonstrates that VSMC Prmt1 is essential for vascular homeostasis and that its ablation causes aortic dilation/dissection through impaired myocardin expression.Subject terms: Epigenetics, Cardiovascular diseases     

A novel bright blue electroluminescent polymer: poly[4,4′‐biphenylene‐α‐(9″,9″‐dihexyl‐3‐fluorenyl) vinylene]

Poly[4,4′‐biphenylene‐α‐(9”,9”‐dihexyl‐2‐fluorenyl)vinylene] (PBPHFV) was synthesized by nickel catalyzed coupling reaction of 1,2‐bis(bromophenyl)‐1‐(9”,9”‐dihexyl‐2‐fluorenyl)ethene and characterized by spectroscopic methods and elemental analysis. PBPHFV is soluble in common organic solvents. The weight average molecular weight (Mw) of PBPHFV is about 15000. PBPHFV showed good thermal stability as weight loss was less than 5 % on heating to 420 C under nitrogen atmosphere. The polymer film showed maximum absorption and emission at 370 nm and 485 nm, respectively. A bright blue electroluminescence (λ_max = 465nm, maximum intensity = 4116 cd/m²) was obtained when the device was fabricated with the structure of ITO/PEDOT/PBPHFV/LiF/Al. The turn on voltage of the device was 4.3 V and the maximum efficiency was 0.22 lm/W. When the blend with PVK (PBPHFV : PVK = 1:5) was used as an emitting layer, the maximum brightness and efficiency of the device were 9342 cd/m² and 1.66 lm/W, respectively.     

In Vitro and In Vivo Photoprotective Effects of (-)-Loliode Isolated from the Brown Seaweed,Sargassum horneri

Skin is the largest organ of humans. Overexposure to ultraviolet (UV) is the primary environmental factor that causes skin damage. The compound, (-)-loliode, isolated from the brown seaweed Sargassum horneri, showed strong antioxidant and anti-inflammatory activities in in vitro and in vivo models. To further explore the potential of (-)-loliode in cosmetics, in the present study, we investigated the photoprotective effect of (-)-loliode in vitro in skin cells and in vivo in zebrafish. The results indicated that (-)-loliode significantly reduced intracellular reactive oxygen species (ROS) level, improved cell viability, and suppressed apoptosis of UVB-irradiated human keratinocytes. In addition, (-)-loliode remarkably attenuated oxidative damage, improved collagen synthesis, and inhibited matrix metalloproteinases expression in UVB-irradiated human dermal fibroblasts. Furthermore, the in vivo test demonstrated that (-)-loliode effectively and dose-dependently suppressed UVB-induced zebrafish damage displayed in decreasing the levels of ROS, nitric oxide, lipid peroxidation, and cell death in UVB-irradiated zebrafish. These results indicate that (-)-loliode possesses strong photoprotective activities and suggest (-)-loliode may an ideal ingredient in the pharmaceutical and cosmeceutical industries.     

Coupling and memory in liquid crystal elastomers

The polymer backbone of a side-chain liquid crystal polymer exhibits an anisotropic shape due to the coupling of the liquid crystal orientational order of the mesogenic side-chains to the backbone. The magnitude and sign of this coupling may be controlled by chemical design. The introduction of chemical cross-links in to such a system provides both a memory of the anisotropic organisation and a mechanism by which the microscopic anisotropy can be realised at a macroscopic level. We show how this anisotropic network structure yields new phenomena when electric or mechanical fields are applied.     

Two-Step Synthesis of trans-2-Arylcyclopropane Carboxylates with 98–100 % ee by the Use of a Phosphazene Base

Only the axial diastereomer of sulfonium salts 2 are formed upon alkylation of 1 . Deprotonation of 2 results in ylides, which allow the highly enantioselective cyclopropanation of Michael systems. The chiral auxiliary 1 is recovered and can be reused.