Chemical constituents from the leaves of Manglietia phuthoensis and their effects on osteoblastic MC3T3-E1 cells

Two new phenyl glycosides, mangliesides A and B (1, 2), a new ionol glycoside, manglieside C (3), two new lignan glycosides, mangliesides D and E (4, 5), were isolated from the leaves of Manglietia phuthoensis, along with two known lignans, 3-methoxymagnolol (6) and obovatol (7). Their structures were established by means of 1D and 2D NMR, electrospray ionization (ESI)-MS and HR-ESI-MS experiments. Among them, compounds 2 and 5 significantly (p<0.05) increased the growth and differentiation of osteoblastic MC3T3-E1 cells in vitro.     

Benzofurans and sterol from the seeds of <Emphasis Type="Italic">styrax obassia</Emphasis>

Two benzofurans (1, 2) along with five known compounds (3.7) were isolated from the seeds of S. obassia. Their structures were elucidated as methyl 3-[7-methoxy-2-(3′,4′-methylenedioxyphenyl)-5-benzofuranyl]-propionate (1), methyl 3-[2-(3′,4′-methylenedioxyphenyl)-5-benzofuranyl]-propionate (2), egonol (3), egonolacetate (4), egonol-2-methylbutanoate (5), 7-demethoxyegonol-2-methylbutanoate (6), and stigmasterol (7) on the basis of their comprehensive spectroscopic analysis including 2D NMR data. Compounds 1, 2 are obtained for the first time from nature, while this is the first record of compound 7 from the Styrax species. Published in Khimiya Prirodnykh Soedinenii, No. 4, pp. 350-353, July-August, 2008. Original article submitted May 4, 2007.     

Coordination asymmetry in divanadium(V) compounds containing a V2O3 core: synthesis, characterization, and redox properties

A general protocol for the synthesis of micro-oxo divanadium(V) compounds [LOV(micro-O)VO(Salen)] (1-5) incorporating coordination asymmetry has been developed for the first time. One of the vanadium centers in these compounds has an octahedral environment, completed by tetradentate Salen ligand, while the remaining center has square pyramidal geometry, made up of tridentate biprotic Schiff-base ligands (L2-) with ONO (1-3) and ONS (4, 5) type donor combinations. Single crystal X-ray diffraction analysis, ESI-MS, and NMR (both 1H and 51V) spectroscopy have been used extensively to establish their identities. The V(1)-O(6)-V(2) bridge angle in these compounds, save 3, lie in a narrow range (166.20(9)-157.79(16) degrees) with the V2O3 core having a rare type of twist-angular structure, somewhat intermediate between the regular anti-linear and the syn-angular modes. For 3, however, the bridge angle is sufficiently smaller 117.92(8) degrees that it forces the V2O3 core to adopt an anti-angular geometry. The V(1)...V(2) separations in these molecules (3.7921(7)-3.3084(6) A) are by far the largest compared to their peers containing a V2O3 core. The molecules retain the binuclear structures also in solution as confirmed by NMR spectroscopy. Their redox behaviors appear quite interesting, each undergoing a one-electron reduction in the positive potential range (E1/2, 0.42-0.45 V vs Ag/AgCl) to generate a trapped-valence mixed-oxidation products [LVVO-(micro-O)-OVIV(salen)]1-, confirmed by combined coulometry-EPR experiments. The bent V-O-V bridge in these molecules probably prevents the symmetry-constrained vanadium d xy orbitals, containing the unpaired electron, to overlap effectively via the ppi orbitals of the bridging oxygen atom, thus accounting for the trapped-valence situation in this case.     

Effect of electrode spacing on image flicker in fringe-field-switching liquid crystal display

Low-frequency driving of a liquid crystal display (LCD) panel to minimise power consumption has drawn much attention recently. In case an LCD panel is driven by a low-frequency fringe field, image flickering phenomenon is detected by the naked human eye when the sign of the applied electric field is reversed. We investigated the effect of electrode spacing on the image flickering phenomenon induced by the flexoelectric effect in a fringe-field-switching (FFS) liquid crystal cell. We found that the image flicker in an FFS cell under low-frequency driving can be eliminated in a simple manner by changing the electrode spacing.     

Ultrathin Free‐Standing Ternary‐Alloy Nanosheets

A synthesis strategy for the preparation of ultrathin free‐standing ternary‐alloy nanosheets is reported. Ultrathin Pd‐Pt‐Ag nanosheets with a thickness of approximately 3 nm were successfully prepared by co‐reduction of the metal precursors in an appropriate molar ratio in the presence of CO. Both the presence of CO and the interplay between the constituent metals provide fine control over the anisotropic two‐dimensional growth of the ternary‐alloy nanostructure. The prepared Pd‐Pt‐Ag nanosheets were superior catalysts of ethanol electrooxidation owing to their specific structural and compositional characteristics. This approach will pave the way for the design of multicomponent 2D nanomaterials with unprecedented functions.     

Cytocompatible Polymer Grafting from Individual Living Cells by Atom‐Transfer Radical Polymerization

A cytocompatible method of surface‐initiated, activator regenerated by electron transfer, atom transfer radical polymerization (SI‐ARGET ATRP) is developed for engineering cell surfaces with synthetic polymers. Dopamine‐based ATRP initiators are used for both introducing the ATRP initiator onto chemically complex cell surfaces uniformly (by the material‐independent coating property of polydopamine) and protecting the cells from radical attack during polymerization (by the radical‐scavenging property of polydopamine). Synthetic polymers are grafted onto the surface of individual yeast cells without significant loss of cell viability, and the uniform and dense grafting is confirmed by various characterization methods including agglutination assay and cell‐division studies. This work will provide a strategic approach to the generation of living cell–polymer hybrid structures and open the door to their application in multitude of areas, such as sensor technology, catalysis, theranostics, and cell therapy.     

Toughening poly(lactic acid) (PLA) through in situ reactive blending with liquid polybutadiene rubber (LPB)

Abstract

Liquid polybutadiene rubber (LPB) was blended with poly(lactic acid) (PLA) through reactive and non-reactive routes to enhance the toughness of the PLA. The reactively blended PLA (PBR10) was prepared by melt blending the PLA with the LPB in the presence of dicumyl peroxide (DCP), a radical initiator, while the PB10 was just melt blended without the DCP. Fourier transform infrared (FTIR) spectra and wide-angle X-ray diffraction (WAXD) patterns were used to study the molecular structure of the blends. Properties were investigated through universal testing machine (UTM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), scanning electron microscope (SEM) analysis, and rheological measurements. The results indicated that the radical crosslinking by the DCP could increase the compatibility between the PLA and LPB and disperse the rubber particles at the nanoscale in the PLA matrix. As a result, the toughness and melt viscosity of the PLA was significantly enhanced through the reactive blending, which is promising for the practical application of the modified PLA in the area of packaging.     

Syngas conversion beyond chemical equilibrium by in situ bimolecular reaction

An in situ bimolecular reaction, in which syngas is fed with toluene as a secondary reactant (hereafter Tol in situ methylation), was studied over bifunctional catalysts comprised of methanol synthesis catalyst and H-ZSM-5 in a fixed-bed down-flow reactor at 460 psig. When physically mixed with H-ZSM-5 to form bifunctional catalysts, CrZ_HZ (Cr₂O₃/ZnO + HZSM-5) catalyst showed much higher activity than CZA_HZ (CuO/ZnO/Al₂O₃ + H-ZSM-5) in the Tol in situ methylation, while CrZ catalyst exhibited substantially lower activity than CZA in methanol synthesis. CO conversion to methanol in the Tol in situ methylation was estimated by Bz in situ methylation. The CO conversion to methanol was calculated to be in the range of 11–27 %, while that in methanol synthesis over CrZ was about 5 % at most due to chemical equilibrium limitation. By employing a silicalite-coated H-ZSM-5 (Sil/HZ) in bifunctional catalyst, xylene selectivity and para-xylene yield were much improved in the Tol in situ methylation.