Structure–Activity of Valencenoid Derivatives and Their Repellence to the Formosan Subterranean Termite

Eight valencenoid derivatives were evaluated for their repelling activity against Formosan subterranean termites, Coptotermes formosanus Shiraki. Among them, 1,10-dihydronootkatone was the strongest repellent, and valencene was the weakest. Results of the structure-repellency relationships indicated (1) reduction of the ketone group to the alcohol on position 2 of nootkatone curtailed the activity; (2) because of the low activity of valencene relative to nootkatone that the ketone group was essential for repellent activity; (3) reduction of the 1,10 double bond (1,10-dihydronootkatone and tetrahydronootkatone) produced compounds more repellent than nootkatone; (4) the isopropenyl group probably does not participate in binding as evidenced by no significant difference in the repellent activity among nootkatone (double bond between position 11 and 12), isonootkatone (double bond between position 7 and 11), and 11,12-dihydronootkatone.     

A New Approach to the Synthesis of Mg–Al Layered Hydroxides

Theoretical Foundations of Chemical Engineering - Mg–Al layered hydroxides with the composition Mg4Al2(OH)12CO3?3H2O are synthesized by mixing crystalline magnesium and aluminum...     

New Inorganic–Organic Hybrid Materials and Their Oxides for Removal of Heavy Metal Ions: Response Surface Methodology Approach

In this paper, Cu(II), Fe(III), Pb(II), and Zn(II) heavy metal ions were removed from their aqueous solutions by using novel inorganic–organic hybrid materials, Al-GPTS-H and Al-GPTS-NaOSiMe₃-H (hybrid material-1 and 2, respectively), and their oxides (calcined-1 and 2) as adsorbents. These ions removal by adsorption was optimized by using response surface methodology (RSM). Central composite design (CCD) method was used in order to investigate the effects of initial pH, initial metal concentration of solutions and adsorbent quantity on the adsorption efficiency (R, %). As a result of the experiments under optimum conditions, the maximum % R values were obtained by hybrid material-1 for Fe(III) (99.89%) and by calcined material-1 for Pb(II) (97.14%), respectively. These quite high adsorption efficiency values have shown that these hybrid materials and their oxides are suitable to use for heavy metal ions removal from aqueous solutions.     

Morphologies of Sol–Gel Derived Thin Films of ZnO Using Different Precursor Materials and their Nanostructures

We have shown that the morphological features of the sol–gel derived thin films of ZnO depend strongly on the choice of the precursor materials. In particular, we have used zinc nitrate and zinc acetate as the precursor materials. While the films using zinc acetate showed a smoother topography, those prepared by using zinc nitrate exhibited dendritic character. Both types of films were found to be crystalline in nature. The crystallite dimensions were confined to the nanoscale. The crystallite size of the nanograins in the zinc nitrate derived films has been found to be smaller than the films grown by using zinc acetate as the precursor material. Selected area electron diffraction patterns in the case of both the precursor material has shown the presence of different rings corresponding to different planes of hexagonal ZnO crystal structure. The results have been discussed in terms of the fundamental considerations and basic chemistry governing the growth kinetics of these sol–gel derived ZnO films with both the precursor materials.

Polymer-Salt Synthesis of Photoactive Bactericide ZnO–Ag and ZnO–SnO2–Ag Nanopowders and a Study of Their Structure and Properties

Glass Physics and Chemistry - This paper describes the low-temperature polymer-salt synthesis of ZnO–Ag nanopowders and presents the results of studying their structure, morphology, and...     

New Insights into Alterations in PL Proteins Affecting Their Binding to DNA after Exposure of Mytilus galloprovincialis to Mercury—A Possible Risk to Sperm Chromatin Structure?

Mercury (Hg) is a highly toxic and widespread pollutant. We previously reported that the exposure of Mytilus galloprovincialis for 24 h to doses of HgCl₂ similar to those found in seawater (range 1–100 pM) produced alterations in the properties of protamine-like (PL) proteins that rendered them unable to bind and protect DNA from oxidative damage. In the present work, to deepen our studies, we analyzed PL proteins by turbidimetry and fluorescence spectroscopy and performed salt-induced release analyses of these proteins from sperm nuclei after the exposure of mussels to HgCl2 at the same doses. Turbidity assays indicated that mercury, at these doses, induced PL protein aggregates, whereas fluorescence spectroscopy measurements showed mercury-induced conformational changes. Indeed, the mobility of the PLII band changed in sodium dodecyl sulphate-polyacrylamide gel electrophoresis, particularly after exposure to 10-pM HgCl₂, confirming the mercury-induced structural rearrangement. Finally, exposure to HgCl₂ at all doses produced alterations in PL-DNA binding, detectable by DNA absorption spectra after the PL protein addition and by a decreased release of PLII and PLIII from the sperm nuclei. In conclusion, in this paper, we reported Hg-induced PL protein alterations that could adversely affect mussel reproductive activity, providing an insight into the molecular mechanism of Hg-related infertility.     

Simultaneous Interpenetrating Polymer Networks of Polyurethane from Pentaerythritol–Modified Castor Oil and Polystyrene: Structure–Property Relationships

Castor oil was transesterified with pentaerythritol thereby introducing reactive hydroxyl groups. The method of matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy was used to determine the components of the castor oil pentaerythritol alcoholysis products. Simultaneous interpenetrating polymer networks of pentaerythritol modified castor oil and diphenyl-methane 4-4′ diisocyanate polyurethane (P1-CO-PU) and polystyrene (PS) were synthesized using benzoyl peroxide as the initiator and divinyl benzene as the crosslinker. The effect of PU/PS composition on the morphology, miscibility and physical properties of the resulting IPNs was investigated by scanning electron microscopy, dynamic mechanical thermal analysis, measurements of mechanical properties and resistance to chemical reagents. The patterns of the extent of the phase separation and the characteristics of the interpenetration reached as a function of the components were deduced.     

Synthesis of New Composite Anti—Oxidants and Their Appliction to Carbon—Containing Refractories

The present paper describes the synthesis of new com-postie anti-oxidants consisting of Al4SiC4 and aluminum-oxycarbides by heating a mixture of silica ,aluminum and carbonaceous substance at relatively low temperatures of 1500℃ in a flowing argon atmosphere.The phase compo-sition of the composite powder could be controlled through adjusting the fraction of raw materials in starting materi-als ,and also through controlling the sythesizing tempera-ture.In addition, the residual amount of Al4C3,Which was an intermediate phase in rection process,could be eliminated as much a5 possible.Therefore ,the hydration of the composite owders can be avoided.The addition of the synthesized composite anti-oxidants into carbon-bearing refractories can improve oxidation resistance greatly just like aluminum does but with non-hydration and breakage after oxidation.     

Ribosome: The Structure–Function Relation and a New Paradigm to the Protein Folding Problem

The rate of protein synthesis is about seven and fifteen amino acids per second, in the eukaryotic and the bacterial ribosome, respectively. Hence, a few minutes is required to synthesize a polypeptide of an average length. This is much longer than the time needed for the hydrophobic collapse (folding) to take place. So a polypeptide gets enough time to form its local secondary to tertiary structures cotranslationally and put such segments in proper order while in association with the ribosome, unless something prevents its entire length from folding. As reported earlier, ribosomes from prokaryotes, eukaryotes, and mitochondria act as molds for protein folding, and each mold has a set of recognition sites for all proteins. More specifically, the mold is the peptidyl transferase center (PTC), a part of the large RNA of the large ribosomal subunit. Specific amino acids from different random coil regions in a protein interact with specific nucleotides in the PTC, which brings the entire length of the protein into the small space of the PTC mold. The mold thus helps to stabilize the entropy-driven collapsed state of the polypeptide. The process also divides the protein into small segments; each segment is connected at two ends with two nucleotides and can fold in the ribosomal environment. The segments dissociate in such a sequence that the organization proceeds hierarchically from the core of the globular protein radially towards the outer surface. Then the protein dissociates from the ribosome in a “folding competent state” which does the final fine tuning in folding outside the ribosome. While the ribosomal contact and release are over in 1–2 minutes in vitro, the fine tuning takes about 5–10 minutes. Release from the ribosome needs no added energy factor from outside, like ATP.     

Crystal Structure and Physical Properties of PVDF Films Filled with CuCl2–MnCl2 Mixed Fillers

ABSTRACT

Poly(vinylidene fluoride) (PVDF) films filled with mixed fillers of CuCl₂–MnCl₂ were prepared. The differential thermal analysis (DTA) indicates the existence of two main endothermic peaks and the crystallization exothermic temperature. X-ray diffraction (XRD) evidenced the presence of a semicrystalline structure containing α, β, and γ crystalline phases. The optical absorption spectra depicted two shoulder-like bands as well as a strong valley. The IR spectra confirmed the XRD implications about the presence of α, β, and γ phases. The dc electrical resistivity results are discussed on the basis of Kuivalainen modified interpolaron hopping model. The temperature and filling level dependence of the hopping distance R₀ were studied. The dc magnetic susceptibility data follow the Curie-Weiss law. The electron spin resonance (ESR) investigation suggested the existence of aggregated Mn²⁺ for higher values of x where the spectra were characterized by Lorentzian signal. On the other hand, at lower values of x, the spectra were characterized by two unresolved sharp peaks.     

Correction to: Strengthening Oxide–Oxide-Free Materials by Incorporation of TiC–ZrC Solid Solutions into Their Structure during Spark Plasma Sintering of Initial Powder Mixtures under High Compression Loads

Refractories and Industrial Ceramics - To the article “Strengthening Oxide–Oxide-Free Materials by Incorporation of TiC–ZrC Solid Solutions into Their Structure during Spark...     

Investigation of the Structure and Piezoelectricity of Poly(vinylidene fluoride–trifluroethylene) Copolymer Doped with Different Dyes

The structure and piezoelectricity of poly(vinylidene fluoride–trifluroethylene) copolymer doped with crystal violet (CV), Coumarin 2 (C2), and N,N-Dimethyl-4-nitro-4-stilbenamine (DANS) were investigated by several techniques. H- and J-aggregates are formed in the CV and C2 doped copolymer, respectively, while DANS doped copolymer showed lamella structure. Moreover, the application of pressure-induced crystalline phase in the CV doped copolymer and TSDC measurements revealed that the ferroelectric to paraelectric transition peak has taken place in the C2 and DANS doped copolymer. Kohlrausch-Williams-Watts stretched function was applied to estimate the relaxation time of the piezoelectric current. The pyroelectricity is found to be dipole-moment-dependent.     

Non-Covalent Synthesis of Metal Oxide Nanoparticle–Heparin Hybrid Systems: A New Approach to Bioactive Nanoparticles

Heparin has been conjugated to Fe₃O₄, Co₃O₄, and NiO nanoparticles (NPs) through electrostatic interactions, producing colloidal suspensions of hybrid metal oxide heparin NPs that are stable in water. Negative zeta potentials and retention of heparin’s ability to capture toluidine blue indicate that heparin’s negative charges are exposed on the surface of the coated NPs. IR results confirmed the formation of nanohybrids as did NMR experiments, which were also interpreted on the basis of toluidine blue tests. Transmission electron microscopy results revealed that the heparin coating does not modify the shape or dimension of the NPs. Dynamic light scattering and negative zeta potential measurements confirmed that heparin surface functionalisation is an effective strategy to prevent NP aggregation.     

Hydrothermal Synthesis,Crystal Structure and Electrochemical Property of Two Inorganic–Organic Hybrid Frameworks via Hydrogen Bonding

Two inorganic–organic hybrid frameworks, namely [Cu₂(pdca)₂(bibp)(H₂O)₂]·H₂O (1) and [Fe(pdca)(pyco)(H₂O)]·H₂O (2) (H₂pdca = pyridine-2,6-dicarboxylic acid, bibp = 4,4′-bisimidazolylbiphenyl, pyco = picolinate N-oxide) were synthesized via hydrothermal reactions. Both compounds have been characterized by elemental analysis, spectroscopic analysis, thermogravimetric analysis (TGA) and the single crystal diffraction. Complex 1 is dinuclear and five-coordinated copper(II) complex, while complex 2 displays mono-nuclear and six-coordinated iron(III) complex. In the crystal structures of both complexes, the coordinated and crystalline water molecules and H₂pdca ligands contribute to the formation of O–H···O and C–H···O hydrogen bonds, which link the molecules into layers parallel. Cyclic voltammetry (CV) analysis shows one reversible reduction potential at 0.14 V (E_pc) in complex 1, whereas in complex 2 shows a reduction potential at 0.15 V (E_pc) in the cathodic region.     

Erratum to: Preparation of Mullite–TiC–ZrC-Ceramic Materials by a Plasma-ARC Method and Their Properties

Refractories and Industrial Ceramics -     

Erratum to: Preparation of Mullite–TiC–ZrC-Ceramic Materials by a Plasma-ARC Method and Their Properties

Refractories and Industrial Ceramics -     

Structure and Energetics of Ligand–Fluorine Interactions with Galectin-3 Backbone and Side-Chain Amides: Insight into Solvation Effects and Multipolar Interactions

Multipolar fluorine–amide interactions with backbone and side-chain amides have been described as important for protein–ligand interactions and have been used to improve the potency of synthetic inhibitors. In this study, fluorine interactions within a well-defined binding pocket on galectin-3 were investigated systematically using phenyltriazolyl-thiogalactosides fluorinated singly or multiply at various positions on the phenyl ring. X-ray structures of the C-terminal domain of galectin-3 in complex with eight of these ligands revealed potential orthogonal fluorine–amide interactions with backbone amides and one with a side-chain amide. The two interactions involving main-chain amides seem to have a strong influence on affinity as determined by fluorescence anisotropy. In contrast, the interaction with the side-chain amide did not influence affinity. Quantum mechanics calculations were used to analyze the relative contributions of these interactions to the binding energies. No clear correlation could be found between the relative energies of the fluorine–main-chain amide interactions and the overall binding energy. Instead, dispersion and desolvation effects play a larger role. The results confirm that the contribution of fluorine–amide interactions to protein–ligand interactions cannot simply be predicted, on geometrical considerations alone, but require careful consideration of the energetic components.