Three New Abietane‐type Diterpenes from the Bark of Cryptomeria japonica

Three new abietane‐type diterpenoids, 7β‐acetoxy‐12‐methoxyabieta‐8,11,13‐triene‐6α,11‐diol ( 1 ), 7α‐acetoxy‐12‐methoxyabieta‐8,11,13‐triene‐6α,11‐diol ( 2 ), and 6α‐acetoxy‐12‐methoxyabieta‐8,11,13‐triene‐7α,11‐diol ( 3 ), as well as two known abietane‐type diterpenoids, 12‐methoxyabieta‐8,11,13‐triene‐6α,7β,11‐triol ( 4 ) and 6α‐acetoxy‐12‐methoxyabieta‐8,11,13‐triene‐7β,11‐diol ( 5 ), were isolated from the MeOH extract of the bark of Cryptomeria japonica. Their structures were determined by analysis of spectroscopic data and comparison of NMR data with those of related metabolites.     

Structure-Activity Relationship of NF023 Derivatives Binding to XIAP-BIR1

Inhibitors of Apoptosis Proteins (IAPs) are conserved E3-ligases that ubiquitylate substrates to prevent apoptosis and activate the NF-kB survival pathway, often deregulated in cancer. IAPs-mediated regulation of NF-kB signaling is based on the formation of protein complexes by their type-I BIR domains. The XIAP-BIR1 domain dimerizes to bind two TAB1 monomers, leading to downstream NF-kB activation. Thus, impairment of XIAP-BIR1 dimerization could represent a novel strategy to hamper cell survival in cancer. To this aim, we previously reported NF023 as a potential inhibitor of XIAP-BIR1 dimerization. Here we present a thorough analysis of NF023 binding to XIAP-BIR1 through biochemical, biophysical and structural data. The results obtained indicate that XIAP-BIR1 dimerization interface is involved in NF023 binding, and that NF023 overall symmetry and the chemical features of its central moiety are essential for an efficient interaction with the protein. Such strategy provides original hints for the development of novel BIR1-specific compounds as pro-apoptotic agents.     

Ag/ZrO2 and Ag/Fe–ZrO2 catalysts for the low temperature total oxidation of toluene in the presence of water vapor

Transition Metal Chemistry - New mesoporous and well-structured Ag-based catalysts (xAg/ZrO2 and xAg/Fe–ZrO2 with x = 2 wt%) have been investigated in the total...     

Water-dissolvable sodium sulfate nanowires as a versatile template for the fabrication of polyelectrolyte- and metal-based nanotubes

This study presents the synthesis of water-dissolvable sodium sulfate nanowires, where Na(2)SO(4) nanowires were produced by an easy reflux process in an organic solvent, N,N-dimethylformamide (DMF) and formed from the coexistence of AgNO(3), SnCl(2), dodecylsodium sulfate (SDS), and cetyltrimethylammonium bromide (CTAB). Na(2)SO(4) nanowires were derived from SDS, and the morphology control of the Na(2)SO(4) nanowires was established by the cooperative effects of Sn and NO(3)(-), while CTAB served as the template and led to homogeneous nanowires with a smooth surface. Since the as-synthesized sodium sulfate nanowires are readily dissolved in water, these nanowires can be treated as soft templates for the fabrication of nanotubes by removing the Na(2)SO(4) core. This process is therefore significantly better than other reported methodologies to remove the templates under harsh condition. We have demonstrated the preparation of biocompatible polyelectrolyte (PE) nanotubes using a layer-by-layer (LbL) method on the Na(2)SO(4) nanowires and the formation of Au nanotubes by the self-assembly of Au nanoparticles. In both nanotube synthesis processes, PEI (polyethylenimine), PAA (poly(acrylic acid)), and Au nanoparticles served as the building blocks on the Na(2)SO(4) templates, which were then rinsed with water to remove the core templates. This unique water-dissolvable template is anticipated to bring about versatile and flexible downstream applications.     

The Kinetics of Analcime Synthesis in Alkaline Solution

In this study glass has been used as a starting material in order to increase the resolution of the experiment and establish the kinetics of analcimes during hydrothermal synthesis. The experimental results show that the crystal growth curves represent two‐stage linear growth. The first stage is marked by rapid crystal growth whilst the second stage indicates much slower growth. The nuclei appear before the crystals start growing. The crystal growth rate is dependent on the experimental conditions. The nucleation rate increases as the glass dissolves and reaches a maximum when the glass is completely dissolved. Thereafter, the concentration decreases with the consumption of nutrients, and both nucleation and crystal growth stops when supersaturation occurs.     

Enhancing Electron Collection Efficiency and Effective Diffusion Length in Dye‐Sensitized Solar Cells

Intensity‐modulated photocurrent spectroscopy and intensity‐modulated photovoltage spectroscopy are employed to measure the dynamics of electron transport and recombination in the ZnO nanowire (NW) array‐ZnO/layered basic zinc acetate (LBZA) nanoparticle (NP) composite dye‐sensitized solar cells (DSSCs). The roles of the vertical ZnO NWs and insulating LBZA in the electron collection and transport in DSSCs are investigated by comparing the results to those in the TiO₂–NP, horizontal TiO₂–NW and vertical ZnO–NW‐array DSSCs. The electron transport rate and electron lifetime in the ZnO NW/NP composite DSSC are superior to those in the conventional TiO₂–NP cell due to the existence of the vertical ZnO NWs and insulating LBZA. It indicates that the ZnO NW/NP composite anode is able to sustain efficient electron collection over much greater thickness than the TiO₂–NP cell does. Consequently, a larger effective electron diffusion length is available in the ZnO composite DSSC.     

Surfactant-assisted hollowing of Cu nanoparticles involving halide-induced corrosion-oxidation processes

We have demonstrated a simple fabrication of hollow nanoparticles by halide-induced corrosion oxidation with the aid of surfactants. Cuprous oxide Cu2O nanoshells can be generated by simply mixing Cu nanoparticles with alkyltrimethylammonium halides at 55 degrees C for 16 min. The hollowing mechanism proposed is that absorption of surfactants onto the Cu surface facilitates the formation of the void interior through an oxidative etching process. Upon extending the reaction up to 4 h, fragmentation, oxidation, and self-assembly were observed and the CuO ellipsoidal structures were formed. The headgroup lengths of the surfactants influenced the degree of CuO ellipsoidal formation, whereby longer surfactants favored the generation of ellipsoids. Optical absorption measured by UV-visible spectroscopy was used to monitor both oxidation courses of Cu-->Cu2O and Cu2O-->CuO and to determine the band-gap energies as 2.4 eV for Cu2O nanoshells and 1.89 eV for CuO ellipsoids. For the contact-angle measurements, the wettability changed from hydrophilicity (18 degrees) to hydrophobicity (140 degrees) as the Cu2O nanoshells shifted to CuO ellipsoids.     

ESR spectra and structure of the n-butane and n-hexane radical cations

Well-resolved ESR spectra of the n-butane and n-hexane radical cations have been generated, each spectrum showing a 1:2:1 triplet and a detailed substructure. The results are interpreted in terms of an a_g singly occupied MO (^σC—C, δC–H_ax) which is delocalized over the extended carbon chain (C_2h symmetry) and two axial hydrogens.