Hypersonic surface waves in 2D titanium nanostructure on silicon

The non‐destructive method of Brillouin spectroscopy was applied to investigate the vibrations of 2D titanium nanoislands. Simulations realized by the Finite Element Method permitted determination of the dispersion relations of the surface waves propagating in the island structure and silicon substrate as well as the width of the frequency gap for the system studied. 3D maps of unit cell deformation for the structure with nanoislands for individual modes were obtained. The Brillouin experiment is shown as an excellent tool for direct experimental determination of the presence of eigenvibrations and the frequency gap in phononic structures in the GHz range.

     

Understanding the inhibitory effect of highly potent and selective archazolides binding to the vacuolar ATPase

Vacuolar ATPases are a potential therapeutic target because of their involvement in a variety of severe diseases such as osteoporosis or cancer. Archazolide A (1) and related analogs have been previously identified as selective inhibitors of V-ATPases with potency down to the subnanomolar range. Herein we report on the determination of the ligand binding mode by a combination of molecular docking, molecular dynamics simulations, and biochemical experiments, resulting in a sound model for the inhibitory mechanism of this class of putative anticancer agents. The binding site of archazolides was confirmed to be located in the equatorial region of the membrane-embedded V(O)-rotor, as recently proposed on the basis of site-directed mutagenesis. Quantification of the bioactivity of a series of archazolide derivatives, together with the docking-derived binding mode of archazolides to the V-ATPase, revealed favorable ligand profiles, which can guide the development of a simplified archazolide analog with potential therapeutic relevance.     

The Synthesis of Zinc(II) and Cadmium(II) 2,4-Dichlorophenoxyacetates in Water–Methanol Environment. Structure and Properties of Polymeric [Zn(2,4-D)2(MeOH)2]n and [Cd(2,4-D)2(H2O)2]n

Abstract  

The zinc(II) and cadmium(II) 2,4-dichlorophenoxyacetate salts were synthesized in mixed water–methanol environment and characterized by elemental analysis, IR spectrometry and thermal analysis coupled with mass spectrometry. The crystal structures were determined by X-ray crystallography (compound 1, [C₁₈H₁₈Cl₄O₈Zn] _n : monoclinic, P2₁/c, a = 19.094, b = 7.378, c = 8.008, α = 90.00, β = 101.134, γ = 90.00, V = 1106.95; compound 2, [C₁₆H₁₄Cl₄O₈Cd] _n : monoclinic, P2₁/c, a = 17.730, b = 7.293, c = 8.060, α = 90.00, β = 95.18, γ = 90.00, V = 1037.9). The structural and some thermal data about the presented cadmium salt were previously reported (Song et al. Acta Crystallogr E 62:m2397, 2006; Kobylecka et al. Thermochim Acta 482:49, 2009).     

Formation and stabilization of persistent free radicals

We demonstrate that stable and relatively unreactive “environmentally persistent free radicals (PFRs)” can be readily formed in the post-flame and cool-zone regions of combustion systems and other thermal processes. These resonance-stabilized radicals, including semiquinones, phenoxyls, and cyclopentadienyls, can be formed by the thermal decomposition of molecular precursors including catechols, hydroquinones and phenols. Association with the surfaces of fine particles imparts additional stabilization to these radicals such that they can persist almost indefinitely in the environment. A mechanism of chemisorption and electron transfer from the molecular adsorbate to a redox-active transition metal or other receptor is shown through experiment, and supported by molecular orbital calculations, to result in PFR formation. Both oxygen-centered and carbon-centered PFRs are possible that can significantly affect their environmental and biological reactivity.     

Continuous flow hydride generation for the preconcentration and determination of arsenic and antimony by GFAAS

A method has been developed for the determination of arsenic and antimony at sub-ppb level using hydride preconcentration inside the graphite furnace. The influence of the quality of the graphite surface, of its modification with palladium coating and of the ways of introducing hydride into the furnace on the analytical signal is discussed. After optimization of system parameters, detection limits of 25 and 36 pg were obtained for arsenic and antimony. Characteristic masses (for arsenic and antimony, respectively) were 31 and 33 pg/0.0044 A·s for direct injection GFAAS and 69 and 57 pg/0.0044 A·s for hydride in situ preconcentration and atomization in the palladium coated graphite tube. Therefore the overall efficiency of the hydride generation and trapping was estimated to be 45 and 58% for arsenic and antimony, respectively.     

A route to Prelog-Djerassi lactone from methyl α,D-glucopyranoside

The enone $\text{1}$ obtained from methyl α,D-glucopyranoside is converted into the corresponding diene $\text{5}$ which is hydrogenated to give predominantly the diequatorial dimethyl hexopyranoside $\text{3}$. C6 of the latter is converted stepwise to the methyl ketone from which Prelog-Djerassi Lactone $\text{8}$ and its 2-epimer $\text{9}$ are prepared in 3:2 ration.