Inhibitory Kinetics of p-Substituted Benzaldehydes on Polyphenol Oxidase from the Fifth Instar of Pieris Rapae L.

Polyphenol oxidase (PPO) is the enzyme responsible for enzymatic browning during the growth of insects. It is also involved in defense reactions and is related with immunities in insects. PPO, a metalloenzyme oxidase, catalyzes the oxidation of ο-diphenol to ο-quinone. The present paper de- scribes the effects of benzaldehyde and its p-substituted derivatives on the activity of PPO from the fifth instar of Pieris rapae L. PPO from the fifth instar of Pieris rapae L. was purified using ammonium sulfate fractionation and chromatography on Sephadex G-100. The enzyme kinetics was characterized using L-3,4-dihydroxyphenylalanine (L-DOPA) as substrate. The results show that benzaldehyde, p- hydroxybenzaldehyde, p-chlorobenzaldehyde, and p-cyanobenzaldehyde can inhibit the PPO activity for the oxidation of L-DOPA. The inhibitor concentration leading to 50% activity lost, IC50, was esti- mated to be 5.90, 5.62, 2.83, and 2.91 mmol/L for the four tested inhibitors, respectively. Kinetic analy- ses show that the inhibitory effects of these compounds are reversible. Benzaldehyde, p- hydroxybenzaldehyde, and p-chlorobenzaldehyde are noncompetitive inhibitors while p-cyano- benzaldehyde is a mixed-type inhibitor. The inhibition constants were determined for all four inhibitors. p-chlorobenzaldehyde and p-cyanobenzaldehyde were more potent inhibitors than the other com- pounds. These results provide a basis for developing PPO inhibition-based pesticides.     

In vitro antibacterial and osteogenic properties of plasma sprayed silver-containing hydroxyapatite coating

The objective of the present investigation was to characterize the antibacterial and osteogenic properties of plasma sprayed silver-containing hydroxyapatite （HA/Ag） coating in vitro. HA/Ag coating was deposited via vacuum plasma spraying. The concentration of silver ions released from HA/Ag coating, the efficacy of the HA/Ag coating against bacterial biofilm development, the effect of the HA/Ag coating on early adhesion and ossification of osteoblast cells in vitro was measured. The silver ion concentration released from the HA/Ag coating was between the minimum inhibitory concentration to bacteria and the cytotoxic concentration. Bacterial biofilm inhibition studies indicated an antibacterial activity on the HA/Ag coating surface when compared with hydroxyapatite （HA） coating alone. Moreover, it was demonstrated that osteoblast cell adhesion and mineralization occurred on the HA/Ag coating surface during the testing period. We conclude that the vacuum plasma sprayed HA/Ag coating possesses good antibacterial capability and osteogenic properties in vitro and represents a promising candidate for coating orthopedic implants.     

Kinetics of Inhibition of Polyphenol Oxidase Obtained from Tobacco Nicotiana Tobacum

In this study, the kinetics of inhibition of polyphenol oxidase by L-cysteine has been investigated. The inhibition of tobacco polyphenol oxidase was studied using the progress-of-substrate-reaction method proposed by Tsou, following the substrate reaction during irreversible inhibition of the enzyme activity. Analysis of the inhibition kinetics shows that inhibition occurs by an irreversible and non-complexation reaction. The microscopic rate constants were determined for reaction of the inhibitor both with the free enzyme and with the enzyme-substrate complex. The results show that the presence of the substrate has a significant protective effect of the enzyme against inactivation by L-cysteine.     

Antibacterial properties and corrosion resistance of AISI 420 stainless steels implanted by silver and copper ions

Silver or copper ions are often chosen as antibacterial agents. But a few reports are concerned with these two antibacterial agents for preparation of antibacterial stainless steel (SS). The antibacterial properties and corrosion resistance of AISI 420 stainless steel implanted by silver and copper ions were investigated. Due to the cooperative antibacterial effect of silver and copper ions, the Ag/Cu implanted SS showed excellent antibacterial activities against both Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus) at a total implantation dose of 2×1017 ions/cm2. Electrochemical polarization curves revealed that the corrosion resistance of Ag/Cu implanted SS was slightly enhanced as compared with that of un-implanted SS. The implanted layer was characterized by X-ray photoelectron spectroscopy (XPS). Core level XPS spectra indicate that the implanted silver and copper ions exist in metallic state in the implanted layer.     

Au, Ag and Au:Ag colloidal nanoparticles synthesized by pulsed laser ablation as SERS substrates

Chemically pure colloidal suspensions of gold and silver nanoparticles were synthesized using pulsed laser ablation.The dependence of laser fl uence on the surface plasmon characteristics of the nanoparticles was investigated.Au:Ag colloidal suspensions were prepared by mixing highly monodisperse Au and Ag nanocolloids.The plasmon band of these mixtures was found to be highly sensitive to Au:Ag concentration ratio and wavelength of the laser beam used in the ablation process.The Au:Ag mixture consists of almost spherical shaped nanostructures with a tendency to join with adjacent ones.The surface enhanced Raman scattering activity of the Au,Ag and Au:Ag colloidal suspensions was tested using crystal violet as probe molecules.Enhancement in Raman signal obtained with Au:Ag substrates was found to be promising and strongly depends on its plasmon characteristics.     

Enhanced strength in novel nanocomposites prepared by reinforcing graphene in red soil and fly ash bricks

Low-dimensional nanomaterials such as graphene can be used as a reinforcing agent in building materials to enhance the strength and durability. Common building materials burnt red soil bricks and fly ash bricks were reinforced with various amounts of graphene, and the effect of graphene on the strength of these newly developed nanocomposites was studied. The fly ash brick nanocomposite samples were cured as per their standard curing time, and the burnt red soil brick nanocomposite samples were merely dried in the sun instead of being subjected to the traditional heat treatment for days to achieve sufficient strength. The water absorption ability of the fly ash bricks was also discussed. The compressive strength of all of the graphene-reinforced nanocomposite samples was tested, along with that of some standard (without graphene) composite samples with the same dimensions, to evaluate the effects of the addition of various amounts of graphene on the compressive strength of the bricks.     

Mechanical,electrical, and thermal expansion properties of carbon nanotube-based silver and silver-palladium alloy composites

The mechanical, electrical, and thermal expansion properties of carbon nanotube (CNT)-based silver and silver-palladium (10:1, w/w) alloy nanocomposites are reported. To tailor the properties of silver, CNTs were incorporated into a silver matrix by a modified molecular level-mixing process. CNTs interact weakly with silver because of their non-reactive nature and lack of mutual solubility. Therefore, palladium was utilized as an alloying element to improve interfacial adhesion. Comparative microstructural characterizations and property evaluations of the nanocomposites were performed. The structural characterizations revealed that decorated type-CNTs were dispersed, embedded, and anchored into the silver matrix. The experimental results indicated that the modification of the silver and silver-palladium nanocomposite with CNT resulted in increases in the hardness and Young’s modulus along with concomitant decreases in the electrical conductivity and the coefficient of thermal expansion (CTE). The hardness and Young’s modulus of the nanocomposites were increased by 30%–40% whereas the CTE was decreased to 50%–60% of the CTE of silver. The significantly improved CTE and the mechanical properties of the CNT-reinforced silver and silver-palladium nanocomposites are correlated with the intriguing properties of CNTs and with good interfacial adhesion between the CNTs and silver as a result of the fabrication process and the contact action of palladium as an alloying element.     

Thermodynamical properties of protein kinase with adenine inhibitors

The protein-based molecular recognition of the adenine ring is essential to understand protein function and drug design as well.In this paper,a variety of the adenine-based inhibitors with modified groups of amino groups,nitrogen and oxygen atoms in the aromatic ring are designed,and the binding capability of these adenosine analogues with an aminoglycoside antibiotic kinase [APH(3’)-IIIa] are investigated with activity assays and isothermal titration calorimetry(ITC) experiments.1-aminoisoquinoline is one of the weakest substrates bound to APH(3’)-IIIa with the lowest affinity(high ki and high kd) and the smallest negative value of free energy change(G) among the inhibitors tested.The binding process of adenine and 5-nitroisoquinoline to APH(3’)-IIIa is an enthalpy-driven event with unfavorable entropy,which is consistent with the energy change induced by the binding of ATP to the enzyme.However,the reverse is true for 1-aminoisoquinoline,3-amino-5-nitrobenzisothiazole,5-aminoisoquinoline binding to the enzyme because the entropy is more favorable and the enthalpy makes a lower contribution to the binding process.These results suggest that small changes of the adenine ring can lead to significant influence on the ability of these analogues to occupy the adenine-binding region of the enzyme,which can be the potential inhibitors as drug candidates against the bacterial resistance.     

pH值对β-MnO2颗粒光催化去除银离子的影响

The presence of silver ions (Ag(I)) in wastewater has a detrimental effect on living organisms. Removal of soluble silver, especially at low concentrations, is challenging. This paper presents the use of β-MnO₂ particles as a photocatalyst to remove Ag(I) ions selectively from aqueous solution at various pH levels. Inductively coupled plasma mass spectrometry (ICP-MS), X-ray diffraction (XRD), field emission electron microscope (FESEM), transmission electron microscopy (TEM), and X-ray photoelectron microscopy (XPS) were employed to determine the removal efficiency and to characterize the deposition of silver onto the surface of β-MnO₂ particles. The optimum pH for the removal of Ag(I) ions was at pH 4 with 99% removal efficiency under 1 h of visible light irradiation. This phenomenon can be attributed to the electrostatic attraction between β-MnO₂ particles and Ag(I) ions as well as the suppression of electron–hole recombination in the presence of H+ ions.     

New insights into mTOR structure and regulation

The mammalian target of rapamycin, mTOR, forms various protein-protein complexes to regulate cell growth in response to the nutrient and energy status of the cell. Recently, the first crystal structure of large HEAT repeat protein mTOR revealed that the FAT domain interacts with the kinase domain through electrostatic effects and hydrophobic interactions. Based on the structure, the previous researches on how FAT domain regulates mTOR activity are reviewed. DEPTOR is currently known as an endogenous mTOR inhibitor, which may interact with roTOR FAT domain to suppress mTOR activity in vivo. The possible interactions of DEPTOR with the mTOR FAT domain are analyzed, too. In addition, the inhibition mechanism of DEPTOR may be similar to members of HEAT-involved RanGTP complex family, providing new mechanistic insights into mTOR kinase regulation.     

Promising psyllium-based composite containing TiO2 nanoparticles as aspirin-carrier matrix

Composite nanomaterials represent a new trend in the biomedical field. Coupling inorganic/organic constituents with non-toxicity/biocompatibility properties leads to develop the new systems having special characteristics that can be used in various bio-applications. This paper describes the preparation and characterization of psyllium-based composites containing TiO2 nanoparticles in order to develop new therapeutic strategies for aspirin drug delivery. The structural characteristics of obtained materials were investigated by FTIR spectroscopy. The UV–vis spectrophotometric analysis was performed to evaluate the aspirin release behavior under different pH conditions at 37 1C. Combining psyllium(as an excellent source of fiber) with TiO2 inorganic unit(as vehicle of aspirin) it was found that polymeric-TiO2networks have promising potential for controlled aspirin release as therapeutic agent.     

Cyanidation of gold clay ore containing arsenic and manganese

The extraction process of gold and silver from the gold clay ore containing arsenic and manganese was investigated. With the conventional technique, the leaching rates of gold and silver are 78.23% and 49.02%, respectively. To eliminate the negative effects of arsenic and manganese on cyanidation and increase the gold and silver leaching rates, a novel catalyst was added. The content of the catalyst used in the process was 8 g per 500 g org sample, the sample size was 60 μm and the pH value was kept between 10 and 11. Leaching with the catalyst for 3–5 h under certain conditions, the gold leaching rate increased to over 90% and the silver leaching rate increased to 80%–90%. The catalyst can effectively liberate gold and silver from the enclosure of arsenic and manganese and the industrial experiment has great significance to the development and utilization of the gold clay ore containing arsenic and manganese.     

Synthesis, characterization and antibacterial activity of copper, nickel and bimetallic Cu– Ni nanoparticles for potential use in dental materials

The antibacterial effect is a desirable property in dental materials.Development of simple methods for the preparation of nanosized metal particles has attracted significant attention because of their future applications due to unusual size-dependent antibacterial properties.Copper(Cu),Nickel(Ni) and bimetallic Cu–Ni nanoparticles were prepared by a simple chemical method and their antibacterial activity was tested against the widely used standard human pathogens Staphylococcus aureus(gram-negative) and Escherichia coli(gram-positive).Additionally,these nanoparticles were tested against the dental pathogen Streptococcus mutans.Our results are promising for potential use in dental materials science.     

Synergistic Effect of Tungstate and Benzotriazole on Corrosion Inhibition of Carbon Steel in Solutions Containing Cl^-

The corrosion inhibition of tungstate, benzotriazole (BTA) and their combination in solutions containing Cl^- was studied by electrochemical techniques. The results indicated that the inhibition efficiency of tungstate was higher than that of BTA. The efficiency increased with increasing concentration of tungstate or BTA. In the studies of synergistic effect of tungstate and BTA, it had been found that in pH 9.0 solution, the largest Rt could be obtained with the concentration ratio of tungstate / BTA being 1 : 1. Lowering the pH value of solution would reduce the efficiency of inhibitors, especially in binary inhibitors. Increasing the concentration of Cl^- accelerated the corrosion of carbon steel in the solutions with various inhibitors, but the influence of Cl^- on corroding rate in binary inhibitors was not so strong as in single component. The results ofsurface analysis showed that W, C, N, O and Fe elements existed in the protecting film formed with binary inhibitors. The thickness of the film was about 12-15 nm.     

The Composite Cathode of Ag and LSCF for SOFC Working under Intermediate Temperature

1 Introduction The composite electrode of La0.6Sr0.4Co0.2Fe0.8O3(LSCF) and Ag was studied as a new air electrode system for reduced-temperature SOFCs.The LSCF/Ag composite electrodes were prepared by baking the LSCF electrode with various Ag solution infiltrated in the pores of the electrode.In all cases,the cathode polarization resistance was reduced,which may be brought from the catalytic activity of Ag metal.For example,the power density of LSCF electrode on anode supported cell was increased from 0.28 W/cm2 to 0.34 W/cm2 at 600 ℃ by baking the infiltrated Ag solution into the electrode.     

Colorimetric detection of glucose and an assay for acetylcholinesterase with amine-terminated polydiacetylene vesicles

The colorimetric response of amine-terminated polydiacetylene (PDA) vesicles was initially demonstrated by varying the pH of the solution. Convenient colorimetric methods to detect glucose and acetylcholinesterase (AChE) activity were successfully established using amine-terminated PDA vesicles by taking advantage of the following features: (1) the amine-terminated PDA vesicles undergo a colorimetric transition as the pH of the solution changes; (2) glucose can be oxidized to gluconic acid in the presence of glucose oxidase; and (3) AChE catalyzes the hydrolysis of acetylcholine to acetic acid. The visual detection of glucose levels and AChE activity showed good selectivity and acceptable sensitivity. The detection limit of glucose was ~2.5 μmol/L and the level of AChE activity was assayed as low as 10.0 mU/mL. Moreover, the amine-terminated PDA vesicles can be used for screening the activity of inhibitors against AChE.     

Chemical constituents of Solanum coagulans and their antimicrobial activities

The present study aimed at determining the chemical constituents of Solanum coagulans and their antimicrobial activities. The compounds were isolated by various chromatographic techniques and their structures were elucidated on the basis of extensive spectroscopic analysis, chemical methods, and comparison with reported spectroscopic data. One new phenolic glycoside, methyl salicylate 2-O-β-D-glucopyranosyl-（1→2）-β-D-glucopyranoside（1）, together with 12 known compounds（2–13）, were isolated from the aerial parts of Solanum coagulans. Compound 1 was a new phenolic glycoside, and 2–6 were isolated from Solanum genus for the first time. The antimicrobial activities of the isolated compounds were also evaluated. Compound 7 showed remarkable antifungal activity against T. mentagrophytes, M. gypseum and E. floccosum with MIC values being 3.13, 1.56 and 3.13 μg·m L^-1, respectively.     

Effects of Enzymatic Treatments with a Protease and a Total Crude Cellulase on the Handle and Prickle of a Viscose/Wool Blend Furnishing Fabric

Carefully controlled treatments with a protease and acellulase were used to improve the softness and reducethe subjectively perceived prickle of a coarse wool andviscose blend fabric. The activity towards wool of a non-specific endoprotease (Novolan L) was shown to bemuch greater in buffer containing a reducing agent (so-dium sulphite). The balance between protease and sodi-um sulphite concentrations was studied in order to reducethe amount of enzyme required.     

Influence of Ag content on the microstructure,mechanical, and tribological properties of TaVN–Ag films

A series of TaVN–Ag nanocomposite films were deposited using a radio-frequency magnetron sputtering system. The microstructure, mechanical properties, and tribological performance of the films were investigated. The results showed that TaVN–Ag films were composed of face-centered cubic(fcc) TaVN and fcc-Ag. With increasing Ag content, the hardness of TaVN–Ag composite films first increased and then decreased rapidly. The maximum hardness value was 31.4 GPa. At room temperature, the coefficient of friction(COF) of TaVN–Ag films decreased from 0.76 to 0.60 with increasing Ag content from 0 to 7.93 at%. For the TaVN–Ag films with 7.93 at% Ag, COF first increased and then decreased rapidly from 0.60 at 25℃ to 0.35 at 600℃, whereas the wear rate of the film increased continuously from 3.91 × 10-7 to 19.1 × 10-7 mm~3/(N·mm). The COF of the TaVN–Ag film with 7.93 at% Ag was lower than that of the TaVN film, and their wear rates showed opposite trends with increasing temperature.