Search

Maltogenic amylase CoMA from Corallococcus sp. strain EGB catalyzes the hydrolysis and transglycosylation of maltooligosaccharides and soluble starch into maltose, the sole hydrolysate. This process yields pure maltose with potentially wide applications. Here, we identified and evaluated the role of Phenylalanine 314 (F314), a key amino acid located near the active center, in the catalytic activities of the CoMA. Site-directed mutagenesis analysis showed that the activity of a F314L mutant on potato starch substrate decreased to 26% of that of wild-type protein. Compared with the wild-type, F314L exhibited similar substrate specificity, hydrolysis pattern, pH, and temperature requirements. Circular dichroism spectrum data showed that the F314L mutation did not affect the structure of the folded protein. In addition, kinetic analysis demonstrated that F314L exhibited an increased Km value with lower substrate affinity. Homology modeling showed that the benzene ring structure of F314L was involved in π-π-conjugation, which might potentially affect the affinity of CoMA towards starch. Taken together, these data demonstrated that F314 is essential for the hydrolytic activity of the CoMA from Corallococcus sp. strain EGB. This article is protected by copyright. All rights reserved.

Pterocarya stenoptera bark extract (PSBE) was assessed for its chemical constituents, antioxidant activity, and antibacterial activity. The total phenolic content (TPC) in the PSBE was 272.92 ± 3.22 mg gallic acid equivalent (GAE)/g. Three phenolic compounds (quercetin-3-O-(2″-O-galloyl)-rhamnoside, quercetin, and juglone) were identified in the PSBE via ultraperformance liquid chromatography/mass spectroscopy (UPLC/MS) analysis. The PSBE possessed remarkable antioxidant activity in the DPPH and ABTS+ radicals scavenging system, with IC50 values of 96.25 ± 3.82 μg/mL and 158.26 ± 6.08 μg/mL, respectively. Moreover, the PSBE had high antibacterial activity, which was especially sensitive to Staphylococcus aureus. The antibacterial mechanism of the PSBE on the S. aureus was related to the deformation of the cell morphology and the destruction of the cell membrane structure, which was confirmed using a BacLight Viability Kit and scanning electron microscope (SEM) observations. These findings suggest that the strong antioxidant and antibacterial properties of the bark extract from P. stenoptera make the tree species suitable as a natural additive in the pharmaceutical, food, and cosmetic industries.

In this paper, large-scale, self-standing polypyrrole/graphene oxide (PPy/GO) nanocomposite films were prepared by an environmentally friendly and easy-to-operate confined polymerization method, and were also assembled as electrode materials for symmetric all-solid-state supercapacitors. In this paper, large-scale, self-standing polypyrrole/graphene oxide (PPy/GO) nanocomposite films were prepared by an environmentally friendly and easy-to-operate confined polymerization method, and were also assembled as electrode materials for symmetric all-solid-state supercapacitors. The morphology, chemical structure and electrochemical property were characterized by field emission scanning electron microscope (FESEM), Fourier transform infrared spectroscopy (FTIR), cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and electrochemical impedance spectroscopy (EIS), respectively. The lamellar structure of GO and both strong interaction with ice and pyrrole could promote polymerization of pyrrole and improve the compactness of the film. With the aid of GO, the conjugation length of PPy increased, the resistance of the material decreased, and the electrochemical energy storage of the composite film was significantly enhanced. In the case of 2.5 wt% GO, the prepared PPy/GO nanocomposite supercapacitor exhibited a high area specific capacitance of 97.3 mF cm−2 at 1 mA cm−2. Furthermore, the PPy/GO film supercapacitor also showed excellent cycling stability and good flexibility.

The extensive use of nonrenewable peat does not meet the strategic goals of sustainable development. This study explores the advantages and disadvantages of using lignocellulose-based agricultural and forestry wastes as peat substitute in substrates for soilless cultivation; further, it also investigates the key factors influencing the physical and chemical properties of the substrates. Accordingly, the physical and chemical properties of four gramineous crop straws and two woody forestry wastes were determined and compared with those of peat and coconut bran. In addition, cellulose, hemicellulose, and lignin were extracted from wheat straw and pine sawdust, and their basic characteristics and structures were compared and analyzed. The results showed that the influence of particle size on the physical properties of substrates was significantly higher (P < 0.01) than the influence of the substrate type, especially with respect to the water-holding and aeration porosities, which had effect sizes (Eta2) of 73.8% and 68.2%, respectively. The electrical conductivity values of the four straws (1.87-3.42 mS/cm) were higher than those of peat and coconut bran (0.50-0.96 mS/cm), which was mainly due to the high hemicellulose contents (28.52%-30.10%) and total nutrient contents (28.46-47.81 g/kg) of the straws. In contrast, the electrical conductivity values of the woody waste substrates were lower (0.28-0.33 mS/cm) than those of peat and coconut bran. Peat and coconut bran contained the lowest cellulose (17.84%-20.95%) and hemicellulose contents (5.14%-7.19%) of all substrates, resulting in a low degradability and good stability. The crystallinity of coconut bran (23.06%) was significantly lower than that of all other substrates (30.36%-43.03%), which mainly contributed to the superior compressibility of coconut bran. The best pretreatment method for biomass waste used as a substrate should be selected according to the target properties of the corresponding components.

Metal organic frameworks (MOFs) with small particle sizes and incorporated redox sites have attracted tremendous attention as promising electrode materials in supercapacitors (SCs). However, their wide adoption is seriously limited by their poor conductivity and complicated preparation route. Herein, we report a low-cost, single-step method to assemble free-standing laminated hybrid films via the synchronous reduction of graphene oxide (GO) and formation of copper-based MOFs. During this process, small Cu-MOF nanoparticles (NPs) with a mean diameter of 50 nm are in situ embedded in reduced graphene oxide (rGO) to overcome the insulating problem of MOFs and the restacking of the rGO nanosheets. Due to the positive synergistic effects between Cu-MOF crystals and rGO nanosheets, the hybrid Cu-MOF/rGO film electrode delivers a high specific capacitance of 1871 F g−1 at 0.5 A g−1 and a good electrochemical stability with 89% retention after 5000 charge–discharge cycles.

Amorphous pseudocapacitive nanomaterials are highly desired in energy storage applications for their disordered crystal structures, fast electrochemical dynamics, and outstanding cyclic stability, yet hardly achievable using the state-of-the-art synthetic strategies. Herein, for the first time, high capacitive fiber electrodes embedded with nanosized amorphous molybdenum trioxide (A-MoO 3-x ) featuring an average particle diameter of ~20 nm and rich oxygen vacancies are obtained via a top-down method using α -MoO 3 bulk belts as the precursors. The Jahn-Teller distortion in MoO 6 octahedra due to the doubly degenerate ground state of Mo 5+ , which can be continuously strengthened by oxygen vacancies, triggers the phase transformation of α -MoO 3 bulk belts (up to 30 μ m long and 500 nm wide). The optimized fibrous electrode exhibits among the highest volumetric performance with a specific capacitance ( C V ) of 921.5 F cm -3 under 0.3 A cm -3 , endowing the fiber-based weaveable supercapacitor superior C V and E V (energy density) of 107.0 F cm -3 and 9.5 mWh cm -3 , respectively, together with excellent cyclic stability, mechanical robustness, and rate capability. This work demonstrates a promising strategy for synthesizing nanosized amorphous materials in a scalable, cost-effective, and controllable manner.

This study aimed to isolate, prepare and identify the main flavonoids from a standardized Smilax glabra flavonoids extract (SGF) using preparative HPLC, MS, 1H NMR and 13C NMR, determine the contents of these flavonoids using UPLC, then compare their pharmacological activities in vitro. We obtained six flavonoids from SGF: astilbin (18.10%), neoastilbin (11.04%), isoastilbin (5.03%), neoisoastilbin (4.09%), engeletin (2.58%) and (&minus, )-epicatechin (1.77%). The antioxidant activity of six flavonoids were evaluated by determining the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical and 2,2&prime, Azinobis (3-ethylbenzothiazoline-6-sulphonic acid) diammonium salt (ABTS+) radical scavenging activity and ferric reducing antioxidant power (FRAP). In addition, the anti-inflammatory activity of six flavonoids were evaluated by determining the production of cytokines (IL-1&beta, IL-6), nitric oxide (NO) using enzyme linked immunosorbent assay and the NF-&kappa, B p65 expression using Western blotting in lipopolysaccharide (LPS)-stimulated RAW264.7 cells. The results showed that (&minus, )-epicatechin, astilbin, neoastilbin, isoastilbin and neoisoastilbin had strong antioxidant activities, not only in DPPH and ABTS+ radicals scavenging capacities, but in FRAP system. Furthermore, all the six flavonoids could significantly inhibit the secretion of IL-1&beta, IL-6, NO (p &lt, 0.01) and the protein expression of NF-&kappa, B p-p65 (p &lt, 0.01) in LPS-stimulated RAW264.7 cells. This study preliminarily verified the antioxidant and anti-inflammatory activities of six flavonoids in S. glabra.

A facile fabrication strategy of transparent and upconversion photoluminescent nylon 6 (PA6) nanofiber mats was developed based on PA6 nanofiber mats, carboxylic acid-functionalized upconversion nanoparticles (UCNP-COOH), and poly(methyl methacrylate) (PMMA) solution. UCNP-COOH were prepared by a solvothermal method, followed by the ligand exchange process. The electrospinning method and the spin-coating process were employed to combine PA6 nanofiber mats with UCNP-COOH and PMMA to introduce upconversion photoluminescent properties and transparency into the nanocomposite mats, respectively. The prepared UCNP-COOH/PA6/PMMA nanofiber mats are transparent and exhibit green emission, which are similar to UCNP-COOH when they were excited under 980 nm laser. The upconversion luminescent intensity of the functional nanofiber mats can be tailored by adjusting the weight fraction of UCNP-COOH as fillers. This facile strategy can be readily used to other types of intriguing nanocomposites for diverse applications.

Transition metal oxides (TMOs) with desired morphologies and atomic structures have promising applications in energy storage, catalysis, and biosensing because of their large specific surface area, high theoretical capacitance, abundant active sites, etc. In this study, hierarchical Co3O4 with enriched oxygen vacancies and finely tuned nanostructures, e.g. high porosity, thin wall thickness, hollow or yolk–shell structure, is prepared by dynamically balancing the decomposition and oxidation of the zeolitic imidazolate framework-67 (ZIF-67) precursor directly calcined in air at 300 °C. The optimized Co3O4 hollow frame inherits the original shape of the parent ZIF-67 with a high volume retention of 83% and features an ultrathin wall thickness of 10 nm, a large accessible surface area of 63.7 m2 g−1 and a high content of surface oxygen vacancies. It thus delivers an excellent specific capacitance of 770 F g−1 at 1 A g−1, a rate capability of 570.9 F g−1 at 20 A g−1 and excellent cycling stability for energy storage, and a high sensitivity of 0.7 mA mM−1 cm−2, a low detection limit of 0.2 μM (S/N = 3), and a wide linear detectable range of 0.005–1.175 mM for electrochemical non-enzymatic detection of glucose.

Battery-type electrode materials have recently been considered as a new class of high-capacity cathode materials for construction of hybrid supercapacitors, however, their low electrochemical kinetics prevent the practical application. Here, the NiCo2S4/nitrogen and sulfur dual-doped three-dimensional (3D) holey-reduced graphene oxide (NiCo2S4/N, S-HRGO) composite architectures were synthesized via a two-step hydrothermal approach. Thanks to the introduction of 3D interconnected and highly conductive holey-reduced graphene oxide with mesopore-rich structure providing fast electron/ion transport, the as-resulted NiCo2S4/N, S-HRGO composite achieves enhanced supercapacitive performances, especially exceptional rate capability compared to the pure NiCo2S4 and NiCo2S4/nitrogen and sulfur dual-doped reduced graphene oxide (NiCo2S4/N, S-RGO). The NiCo2S4/N, S-HRGO composite shows a specific capacity of 184.2 mAh g−1 at 1 A g−1, and still maintains a high specific capacity of 119.5 mAh g−1 even at 50 A g−1. The excellent rate capability of the composite can be illustrated by in-depth kinetic analysis based on the calculated diffusion coefficient and charge contribution ratio. Furthermore, a hybrid supercapacitor utilizing NiCo2S4/N, S-HRGO and N, S, P tri-doped holey-reduced graphene oxide (N, S, P-HHGO) respectively as the cathode and anode is further constructed, showing a satisfactory energy density (35.4 Wh kg−1), high power density (15.0 kW kg−1) and good cycle durability.

A simple one-pot double in-situ synthetic method was proposed to fabricate transparent semi-aromatic polyamides (SAPA) nanocomposites with upconversion nanoparticles (UCNP) as nanophase contents by combining hydrothermal method with melt polycondensation method. The key to this method is that the nanoparticles and polyamides were prepared in one-pot by simply mixing polyamides monomers and UCNP precursors as the raw materials without preparing polyamides or nanoparticles in advance. This approach enables the simple fabrication of transparent upconversion luminescent semi-aromatic polyamides nanocomposites with UCNP uniformly dispersed and can be extend to other kinds of polyamides and functional nanoparticles to prepare various polyamide nanocomposites.

Upconversion nanoparticles (UCNP) have great potential for applications in biological fields due to their unique anti-stokes luminescent properties. However, the successful preparation of water-soluble upconversion nanoparticles with well-controlled morphology still remains a great challenge. Herein, a facile fabrication method for the preparation of water-soluble polyacrylic acid (PAA) encapsulated core@shell upconversion nanoparticles through metal-free light induced surface initiated atom transfer radical polymerization (LI-SI-ATRP) was presented. This method involves the modification of oleate acid capped upconversion nanoparticles by bi-functional ligands with ATRP initiating sites. Then the water-soluble polyacrylic acid modified core@shell upconversion nanoparticles were synthesized by metal-free light induced atom transfer radical polymerization. The nanoparticles prepared can be well dispersed in water and emit strong green light when excited by 980 nm near-infrared laser which suggesting that these PAA modified UCNP are promising candidates for luminescent bioimaging.

Organophosphates (OPs) are extremely toxic compounds that are used as insecticides or even as chemical warfare agents. Phosphotriesterases (PHPs) are responsible for the detoxification of OPs by catalysing their degradation. Almost 100 PHP structures have been solved to date, yet the crystal structure of the phosphotriesterase from Mycobacterium tuberculosis (mPHP) remains unavailable. This study reports the first crystallization of mPHP. The crystal belonged to space group C222(1), with unit-cell parameters a = 68.03, b = 149.60, c = 74.23 Å, α = β = γ = 90°. An analytical ultracentrifugation experiment suggested that mPHP exists as a dimer in solution, even though one molecule is calculated to be present in the asymmetric unit according to the structural data.

Oligomeric poly(styrene-co-acrylonitrile) quaternary ammonium salts were prepared through reactions of trimethylamine with corresponding poly(styrene–acrylonitrile–vinyl benzyl chloride)s, which were synthesized by the free-radical polymerization of a mixture of styrene, acrylonitrile, and vinyl benzyl chloride. Then, oligomeric poly(styrene-co-acrylonitrile)-modified clays were prepared through the cation exchange of the sodium ions in the clay with the corresponding poly(styrene-co-acrylonitrile) quaternary ammonium salts. The poly(styrene–acrylonitrile–vinyl benzyl chloride)s, poly(styrene-co-acrylonitrile) quaternary ammonium salts, and their clay complexes were characterized with infrared spectroscopy, gel permeation chromatography, thermogravimetric analysis, proton nuclear magnetic resonance, X-ray diffraction, and transmission electron microscopy. X-ray diffraction and transmission electron microscopy studies showed that these novel clay complexes were well intercalated. Furthermore, thermogravimetric analysis data indicated that this series of polymerically modified clays had high enough thermal stability for nanocomposites by melt blending. The thermal treatment of one of these novel clays at 250°C under nitrogen was also conducted. Solubility and infrared studies of this thermally treated clay complex revealed that a novel polyimine/enamine structure clay complex had been formed in the gallery of the clay. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Three polystyryl quaternary ammonium salts have been synthesized from the reactions of trimethylamine with chloromethyl polystyrenes which were prepared by three different methods: free-radical co-polymerization, chloromethylation of polystyrene and anionic polymerization. Then the polystyryl-modified montmorillonites have been obtained from the ion exchange of sodium ions in the montmorillonites with polystyryl quaternary ammonium salts. The polystyryl quaternary ammonium salts have been characterized using proton nuclear magnetic resonance spectrometer ( 1 H NMR), Fourier-transformed infrared spectrometer (FT-IR), and gel permeation chromatography (GPC). The thermal stability of the quaternary ammonium salts and their corresponding modified montmorillonites have been studied by thermo gravimetric analysis (TGA). TGA data have shown that the polystyryl ammonium salt and its modified montmorillonites obtained from the reactions of chloromethyl polystyrene which was prepared by anionic polymerization are the most stable ones respectively. X-ray diffraction (XRD) and transmission electronic microspectroscopy (TEM) analysis of these polystyryl-modified clays have shown that they are of intercalated structures or partial exfoliation with stacked clay layers.

The oligomeric poly(styrene-acrylamide-vinylbenzylchloride) (P(St-AM-VBC)) quaternary ammonium salts have been prepared from the reactions of trimethylamine with the corresponding P(St-AM-VBC)s, which were synthesized by free-radical polymerization of a mixture of styrene, acrylamide, and vinylbenzylchloride. Then the swelling tunable oligomeric poly(styrene-co-acrylamide) modified clays have been prepared through cation exchange of the sodium ions in the clay with the corresponding P(St-AM-VBC) quaternary ammonium salts. The P(St-AM-VBC) and its modified clays have been characterized by infrared spectra (IR), gel permeation chromatography (GPC), thermogravimetric analysis (TGA), proton nuclear magnetic resonance (1H NMR), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The solvent-swelling capacity of poly(styrene-co-acrylamide) modified clays have also been tested, and the experimental results have indicated that these clays are novel swelling tunable organic clays. XRD and TEM studies have shown that these novel swelling tunable clays are well-intercalated or exfoliated. Furthermore, TGA analysis shows that these polymerically modified clays have high thermal stability for nanocomposites by melt blending. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

A determination of the phase constituents of ceramic coatings produced on Al–Cu–Mg alloy by microarc discharge in alkaline solution was performed using x-ray diffraction. The profiles of the hardness, H, and elastic modulus, E, across the ceramic coating were determined by means of nanoindentation. In addition, a study of the influence of microarc oxidation coatings on the tensile properties of the aluminium alloy was also carried out. The results show that the H-and E-profiles are similar, and both of them exhibit a maximum value at the same depth of coating. The distribution of the α-Al2O3 phase content determines the H- and E-profiles of the coatings. The tensile properties of 2024 aluminium alloy show less change after the alloy has undergone microarc discharge surface treatment.

Microstructure and phase composition of the ceramic coatings formed on Ti–6Al–4V alloy by alternating-current microarc oxidation in aluminate solution were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Distributions of nanohardness, H, and elastic modulus, E, along the coating thickness were determined using a nanoindentation method. After microarc oxidation treatment, the microstructure in the Ti–6Al–4V substrate near the coating/metal interface has not been changed; meanwhile, the titanium substrate has hardly absorbed oxygen atoms. The oxide coating is mainly composed of TiO2 rutile and TiAl2O5 compounds. The rutile fraction in the inner layer coating is much higher than in the outer layer. On the contrary, the TiAl2O5 phase has a higher fraction in the outer layer. On the other hand, the nanoindentation test shows from the coating surface to the interior of the coating that the H and E gradually increase. The maximum H and E in the coating can reach 13 and 230 GPa, respectively. The changes of TiO2 and TiAl2O5 contents along the coating thickness determine the H and E profiles in the coating.

A dense ceramic oxide coating, about 50 µm thick, was prepared on a Ti–6Al–4V alloy by alternating current microarc oxidation in an aluminate solution. Its microstructure and phase composition were investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS). The oxide coating contains two layers: an outer layer and a dense internal layer. The coating is mainly composed of TiO2 rutile and TiAl2O5 spinel phases. In the outer layer coating, the TiAl2O5 fraction is much higher than the rutile fraction. However, in the internal layer, rutile becomes the main phase while the TiAl2O5 fraction decreases significantly. During microarc oxidation, local melt–solidification processes take place in the coating, however, the microstructure of the Ti–6Al–4V substrate near the coating/metal interface is not changed. Aluminium from the solution is enriched in the outer layer coating, although it has also diffused into the interior of the coating.

Growth regularity of ceramic coatings formed on Al–Cu–Mg alloy by microarc oxidation was investigated, and the formation mechanism of coatings was discussed. After oxidation of several hours with linear growth, the growth rate of coatings decreases gradually. During the early stage, the sample geometrical dimension increases with oxidation. However, when the ceramic oxide coating reaches a certain thickness, the sample geometrical dimension will no longer increase although the total coating thickness keeps increasing. The oxide coatings contain a loose layer and a compact layer. The loose layer is formed first. After several hours, the compact layer begins to grow towards the Al substrate while the thickness of the loose layer changes little. The thickness of the compact layer can finally reach over 75% of the total coating thickness. After the surface loose layer is ground off, the sample dimension is approximately the same size as the sample before the treatment.

Allicin, a primary ingredient of garlic, has been proposed to possess cardioprotective properties, which are commonly mediated by improved endothelial function. To investigate the effect and mechanism of allicin on the apoptosis of human umbilical vein endothelial cells (HUVECs), we used Propidium iodide (PI) staining and Annexin V/ PI staining assays to establish a model of oxidative stress apoptosis induced by H2O2. MTT, RT-PCR and western-blot assays were used to detect the effects and mechanism of allicin on the model. PI staining, Annexin V/ PI staining assays and morphological assessment suggest that the cell death induced by 0.5 mM H2O2 is primarily apoptotic. Conversely, allicin reverses the effect of H2O2 on cell death, suggesting a role in protecting HUVECs from apoptosis. We demonstrated that H2O2 activates PARP cleavage, reduces pro-Caspase-3 levels and activates Bax expression; however, allicin inhibits each of these apoptotic signaling indicators. Allicin also reduces the levels of malondialdehyde and increases the levels of superoxide dismutase, nitric oxide release and endothelial nitric oxide synthase mRNA, but has no significant effect on inducible nitric oxide synthase mRNA levels. These results demonstrate that allicin has powerful effects in protecting HUVECs from apoptosis and suggest that protection occurs via a mechanism involving the protection from H2O2-mediated oxidative stress.