Volume 68, Issue 10

Silver dendrites have received immense attention because of their fascinating hierarchical structures and unique properties. Depending on the methods of synthesis, Ag dendrites can be implemented in numerous fields. This review summarizes a variety of Ag dendrites preparation techniques. The involved growth mechanisms are investigated in order to control the formation progress more effectively. With regard to the applications, this article mainly focuses on surface enhanced Raman spectroscopy, catalysis, superhydrophobic surface and surface enhanced fluorescence by using Ag dendrites. The remaining issues of the preparation methods, which impede the practical applications of Ag dendrites, are pointed out to enlighten their future research.

Antioxidant capacity of N-(1-naphthyl)valerohydroxamic acid (NVHA) and N-(1-naphthyl)phenylacetohydroxamic acid (NPAHA) has been evaluated by a novel approach employing the fluorescence microscopic single molecule observation method. This method allows direct observation of the changes in single DNA molecules. The DNA cleavage protection activity of the compounds was also assessed by the gel electrophoresis method. The applied methods confirmed that both compounds are capable of inhibiting the free radical mediated DNA damage. Free radical scavenging activity was assessed via the 2,2′-diphenyl-1-picrylhydrazyl free radical (DPPH) and lipid peroxidation inhibition methods. The effective concentration causing a 50 % inhibition of the DPPH concentration, EC50, was found to be 371.54 mM for NVHA and 365.95 mM for NPAHA. Its lipid peroxidation inhibition ability was calculated to be 40.91 % at 371.54 mM for NVHA and 41.14 % at 365.95 mM for NPAHA. These results show the antioxidant potential of the naphthyl hydroxamic acids.

An opioid receptor like (ORL1) receptor is one of a family of G-protein-coupled receptors (GPCR); it represents a new pharmaceutical target with extensive therapeutic potential for the regulation of important biological functions such as nociception, mood disorders, drug abuse, learning or cardiovascular control. Although the crystal structure of the inactive form of the ORL1 receptor has been determined, little is known about its activation. By using X-ray structures of the β2-adrenegic receptor in its inactive (2RH1) and active (3P0G) states as templates, inactive and active homology models of the ORL1 receptor were constructed. Structurally diverse sets of strongly binding antagonists and agonists were docked with both ORL1 receptor forms. The major receptor-ligand interactions responsible for antagonist and agonist binding were identified. Although both sets of ligands, agonists and antagonists, bind to the same region of the receptor, they occupy partially different binding pockets. Agonists bind to the inactive receptor in a slightly different manner than antagonists. This difference is more pronounced in binding to the active ORL1 receptor model and points to the amino acids at the extracellular end of TM6, suggesting that this region is important for receptor-activation.

Kinetic study of reactive extraction of phenylglycine (PhgH) racemate with S-BINAP ((S)-(−)-2,2′-bis(diphenylphosphino)-1,1′-binaphthalene)-copper complex (BINAP-Cu) as the chiral selector was performed in a modified Lewis cell. The theory of extraction accompanied by a chemical reaction was applied to achieve insightful understanding of the extraction process. The effects of agitation speed, interface area, pH value of the aqueous phase, initial concentration of PhgH racemate, and initial concentration of BINAP-Cu on the specific rate of extraction were investigated. An extraction course was simulated based on the rate equations. The forward rate constants of 3.14 × 10−5 m3.4 mol−0.7 s−1 for R-PhgH and 4.03 × 10−5 m3.4 mol−0.7 s−1 for S-PhgH, respectively, were found. The modeled extraction course was in good agreement with the experimental one.

A novel ion imprinted polymeric membrane (IIPM) for copper (Cu) ions transport was prepared by a ion imprinting technique via cross-linking of blended chitosan (CS)/polyvinyl alcohol (PVA) using glutaraldehyde (GA) as the cross-linker and Cu ions as the template. The obtained IIPM was characterised and evaluated by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and permeation studies. Cavities of IIPM containing recognition sites for Cu ions were formed in the compact structure of the CS/PVA membrane which was prepared via the solution casting method. Under the optimum conditions, transport factor of the IIPM reached 2 when the permeation time was 18 h. Selective permeation of Cu ions versus nickel ions through the imprinted membrane was confirmed and a selectivity factor of 1.71 was obtained.

Ethylcellulose (EC) or linear polyimide (LPI) and magnetic neodymium powder particles MQP-14-12 were used for the preparation of inorganic-organic hybrid membranes. For all the membranes, N2, O2 and air permeability were examined. Mass transport coefficients were determined using the Time Lag System based on dynamic experiments in a constant pressure system. The results showed that the membrane permeation properties were improved by the addition of magnetic neodymium particles to the polymer matrix. The magnetic ethylcellulose and polyimide membranes exhibited higher gas permeability and diffusivity, while their permeability selectivity and solubility were either unchanged or slightly increased. Polyimide mixed matrix membranes were characterised by a higher thermal and mechanical stability, larger filler loading, better magnetic properties and reasonable selectivity in the air separation.

In this study, biodiesel was produced from marula (Sclerocarya birrea) oil using impregnated perlite with potassium hydroxide (KOH) as a heterogeneous catalyst. The effect of experimental variables such as temperature (°C), reaction time (h), methanol to oil ratio (mass %), and catalyst to oil ratio (mass %) on the transesterification process were investigated. Using a central composite design (CCD), a mathematical model was developed to correlate the experimental variables with the percentage yield of biodiesel. The model showed that optimum conditions for biodiesel production were as follows: catalyst to oil ratio of 4.7 mass %, temperature of 70.4°C, methanol to oil ratio of 29.9 mass %, and reaction time of 3.6 h. The yield of 91.4 mass % of biodiesel was obtained. It was also possible to recycle and reuse the modified perlite up to three times without any significant change in its catalytic activity. The X-ray diffraction (XRD) and the Brunauer-Emmett-Teller (BET) surface area showed no modifications in the perlite structure. The results show that the important fuel properties of marula biodiesel meet the American Society for Testing and Materials (ASTM) biodiesel standard properties.

The effect of pH, temperature, zero-valent iron (ZVI) dosage and reaction duration on nitrobenzene (NB) degradation by micro-sized ZVI was investigated in batch experiments and the electron efficiency (EE) was evaluated at constant pH. The experimental results showed that the reaction rate constant attained 0.616 min−1, which was far higher than reported in previous studies. The decrease in pH and increase in temperature of the reaction bath promoted the reaction kinetics. ZVI dosage and reaction duration were two key factors affecting NB reduction and EE. A lower ZVI dosage and a slightly longer reaction duration could afford an optimised EE and optimum NB removal. A prolonged reaction or too high a ZVI dosage resulted in increased ZVI waste.

Previous work revealed that the defatted methanol (MeOH) extract of fruits of Conocarpus erectus L. (Combretaceae family) exhibited antioxidant, antibacterial and anti-cancer activities. In further studies of this valuable plant, the defatted MeOH extract of C. erectus fruits was subjected to chromatographic fractionation in a silica gel glass column followed by reversed-phase high-performance liquid chromatography-ultraviolet-electrospray ionisation spectrometry analysis (RP-HPLC-UV-ESI-MS). The major and sharp peaks in each sample were identified or tentatively identified based on matching with some standard compounds and a review of the literature. Ellagic acid, vescalagin/castalagin isomer and di-(hexahydroxy diphenoyl) galloyl hexose isomer were tentatively identified as major components with many hydrolysable types of tannins on the basis of a comparison of its mass patterns with relevant items in the literature. Gallic acid, kaempferol 3-O-β-d-glucopyranoside and quercetin 3-O-β-d-glucopyranoside were identified on the basis of matching retention time (t R) and mass spectra with the standards. Polymethoxylated flavonoid isomers were also tentatively identified. The antioxidant properties of all samples were found to be associated with the total content of phenolic compounds. This may be considered as the first detailed phytochemical report in identifying the phytochemicals in C. erectus fruits. Due to the high antioxidant activity exhibited by both the crude MeOH extract and its fractions, it could be used as an effective natural antioxidant after further in vitro and in vivo studies.

A convenient method was developed for the determination and validation of fosthiazate in cucumber and soil. The procedure is based on liquid partitioning with acetonitrile followed by dispersive solid phase extraction as the clean-up step, after which samples were analysed by gas chromatography-mass spectrometry (GC-MS). The average recoveries ranged from 91.2 % to 99.0 % with relative standard deviations (RSDs) of less than 6.05 %, at three fortification levels (0.02 mg kg−1, 0.1 mg kg−1, 0.5 mg kg−1) in cucumber and soil, and the limits of quantification (LOQs) for fosthiazate were all established at 0.02 mg kg−1. The proposed method was applied successfully to analyses of the dissipation and residue of fosthiazate in field trials. The dissipation rate of fosthiazate was described using pseudo-first-order kinetics with a half-life of 4.33 days and 4.08 days in soil in Beijing and Shandong, respectively. In the terminal residue experiment, fosthiazate residues in cucumber and soil were clearly below the maximum residue level (MRL, 0.2 mg kg−1) set in China.

Imidazolium acetate ionic liquids show high efficiency in the degradation of polylactides (PLA): degradation degree of PLA can reach almost 100 % in imidazolium acetate ionic liquids at 170°C and 1 h under atmospheric pressure, while the degradation degree of PLA remains close to 0 % using neutral 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim]BF4) and acidic ionic liquids at the same reaction conditions. With the increase of both the amount of acetate ionic liquid and the reaction temperature, the degradation degree of PLA increases. The structure of ionic liquids affects the degradation behavior of PLA: for cations, the proton from the C-2 position on the imidazolium ring is involved in the degradation of PLA; the degradation of PLA increases with the increase of the alkyl side-chain length of imidazolium cations; for anions, moderate basicity of the acetate ion contributes to the high activity of the imidazolium acetate ionic liquids in the degradation of PLA.

Two new Brønsted acids [2,2′-ethylidene-bis (4,6-di-tert-butylphenol)] phosphoric acid (EDBPPOOH) and (3,3′,5,5′-tetra-tert-butylbiphenyl-2,2′-diol) phosphoric acid (TBPO-POOH) were synthesised and fully characterised by 1H NMR and 13C NMR spectra and mass spectra. The ringopening polymerisation (ROP) of ɛ-caprolactone (ɛ-CL) catalysed by the two Brønsted acids proceeded at 110°C without a solvent or at ambient temperature in toluene. Experimental results indicated that the two Brønsted acids were efficient catalysts for the ROP of ɛ-CL with moderate number-average molar mass (Mn) and narrow polydispersity indices (PDI). The catalytic activity of TBPO-POOH is higher than EDBP-POOH in the ROP of ɛ-CL. After benzyl alcohol was added, it was able to accelerate the polymerisation process. The polymerisation can also occur with the addition of water with a monomer/catalyst/initiator mole ratio of 100: 1: 1. The living polymerisation was ascertained by the linear relationships of the Mn vs. monomer conversion, then it was further confirmed by a second-feed experiment of a double monomer producing double Mn. A kinetic study of the relationships between monomer concentration and time revealed a first-order dependence on monomer concentration in the polymerisation. End-group analysis of 1H NMR spectra and electrospray-ionisation mass spectra suggests that the two Brønsted acids are capable of catalysing and initiating the ROP of ɛ-CL.

The Diels-Alder reaction was used to fabricate hydroxypropyl methylcellulose-based hydrogels. First, hydroxypropylmethylcellulose (HPMC) was modified by a carboxyl-containing diene molecule (SFA) which was synthesised from furfurylamine and succinic anhydride. Second, dienophile groups were introduced into HPMC by the coupling reaction with N-maleoyl alanine (AMI) using N,N′-dicyclohexylcarbodiimide (DCC) and 4-dimethylaminopyridine (DMAP). Subsequently, the asprepared furan- and maleimide-modified HPMC were dissolved in water and gelation was observed at a pre-determined temperature after a period of time. The samples thus obtained were characterised by FTIR, NMR, SEM, etc. The gelation time changing with temperature, concentration of the solution, and solvent was measured. It was found that gelation time decreased with increasing temperature and concentration of the solution, and that water had a rate-accelerating effect on Diels-Alder reaction. The swelling behaviour indicates that the hydrogels have a high swelling ratio in water and the swelling ratio increases with the increasing temperature. Taking into consideration that the HPMC-based hydrogels are prepared under mild reaction conditions with an adjustable gelation time and thermal stability, the method described here has a potential application in biomaterials, especially in the areas of tissue-engineering and drug-controlled release carriers.

To improve the performance of calcium sulphate whiskers (CSWs) in the papermaking industry, a series of chitosan-coated (CS) calcium sulphate whiskers (CS-CSWs) was prepared, with the aim of effectively reducing their solubility in aqueous solutions. The CS-CSWs were prepared by immersing CSWs in a chitosan acid solution and then cross-linking with alkaline gel via hydrogen-bonding interaction. The CS-CSWs were characterised in terms of water solubility, zeta potential, contact angle, scanning electron microscopy, thermo gravimetric analysis and X-ray photoelectron spectroscopy (XPS). The results indicated that chitosan had a good effect on the surface modification of CSWs. Under optimal conditions, the water solubility of CS-CSWs decreased by 50 %, and the contact angle increased by 63 %. The XPS measurement indicated that the relative thickness of the chitosan coating was 9.8 nm.

In the current study a facile synthetic route for preparing antineoplastic drug GDC-0449 is investigated. Starting with pyridine-1-oxide and 1-iodo-3-nitrobenzene, the intermediate product 2-(2-chloro-5-nitrophenyl) pyridine was prepared by cross-coupling, deoxidation and halogenation. The final compound was then synthesised by reduction of the nitro group followed by amidation. This synthetic route avoids the use of unstable organometallic or organic boride compounds; it employs relatively inexpensive and bench-stable reagents, involves readily controllable reaction conditions, and achieves a relatively high yield.

Two complexes, {Zn(bptc)0.5(bib)}n (I) and {Mn2(bptc)(pip)(H2O)}n (II) (H4bptc = biphenyl-3,3′,5,5′-tetracarboxylic acid; bib = 1,4-bis(2-methylimidazol-1-yl)butane; pip = 2-phenyl-1H-imidazo[4,5-f][1,10]phenanthroline) were synthesized and characterized by single-crystal X-ray diffraction, elemental analysis, IR, TGA and solid fluorescence spectra. The results show that I and II both have 3D network architectures. I has porous architecture with a 162 topology structure. Effective porosity calculated by Platon is 5.5 %. Moreover, it has a two-fold interpenetrating structure allowed by a 70.73° torsion between the benzene rings of the bptc4− ligand and the flexibility of bib. II has a tetranuclear structure composed of binuclear architecture units with the torsion of 43.44° between the benzene rings of the bptc4− ligand. TGA shows that the skeletons of I and II are stable up to 372°C and 553°C, respectively. I exhibits fluorescence.

This study was conducted to clarify the effect of ultra-pressure treatment on the extraction of bioactive compounds from indigo plant leaves (Polygonum tinctorium Lour.) and on their properties. Leaves were harvested the in mid-August, 2013, from Naju City (Korea), and treated using two methods: ultra-pressure (550 MPa, 3 min) and hot-air (70°C, 24 h). Then, the leaves were ultrasonically extracted with methanol. The content of indirubin in leaves treated with ultra pressure and hot air was (535.55 ± 26.14) mg kg−1 and (52.63 ± 6.45) mg kg−1, respectively, and that of tryptanthrin was (165.55 ± 8.74) mg kg−1 and (153.00 ± 7.62) mg kg−1, respectively. Polyphenolic content in the leaves extract was (127.24 ± 13.67) mg kg−1 after the ultrapressure and (88.22 ± 5.33) mg kg−1 after the hot-air treatment. The content of flavonoids was (2298.67 ± 83.27) mg kg−1 after the ultra-pressure and (3224.00 ± 21.45) mg kg−1 after the hotair treatment. Di(phenyl)-(2,4,6-trinitrophenyl)iminoazanium (DPPH) radical scavenging activities of the indigo extract obtained by ultra-pressure and hot-air treatment methods at the concentration of 1 mg mL−1 were (80.25 ± 0.73) % and (66.54 ± 2.35) %, respectively, and 2,2′-azinobis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) radical scavenging activities were estimated as (90.14 ± 0.79) % and (64.45 ± 8.97) %, respectively. The methanol leaf extract after ultra-pressure treatment exhibited higher binding properties to human serum albumin in comparison with catechin and conventional treatments. Consequently, it was assumed that the ultra-pressure treatment is an effective method for the extraction of bioactive compounds from indigo leaves.

Oxidative stress and the resulting damage to cellular and extracellular components has been observed in a variety of degenerative processes, including degenerative joint disorders, where high-molar-mass hyaluronan (HA) is often found to be massively degraded. The present study sought to test the hypothesis that dithiols are more effective in protecting biomacromolecules from free-radicalmediated damage than monothiols. The materials/thiols tested included bucillamine (BUC), dithioerythritol (DTE), dithiothreitol (DTT) and glutathione (GSH), as a reference, for their effectiveness in protecting HA from oxidative degradation induced in vitro. Since HA degradation results in a decrease in its dynamic viscosity, rotational viscometry was applied to follow HA oxidative degradation. The free-radical-scavenging activities of the thiols tested were determined by 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) and di(phenyl)-(2,4,6-trinitrophenyl)iminoazanium (DPPH) assays. It was found that all the dithiols in the concentration range tested protected HA from the oxidative degradation. On the other hand, monothiol GSH exerted protection only at high concentrations (10 μmol L−1 and 100 μmol L−1) and 1 μmol L−1 of GSH even exhibited a prodegradative effect. The ABTS assay revealed free-radical scavenging activities in the following order: BUC, DTT, DTE, GSH, and that of the DPPH assay: BUC, DTE, DTT, GSH. In conclusion, it was demonstrated that dithiols may be more effective than monothiols in affording biomacromolecule protection from oxidative degradation.