(–)-β-Homoarginine anhydride,a new antioxidant and tyrosinase inhibitor,and further active components from Trichosanthes truncata

Abstract

One new amino acid derivative, (–)-β-homoarginine anhydride 1, as well as nine known compounds were isolated from Trichosanthes truncata. The structures of the isolates were elucidated by spectroscopic methods. Among them, compounds 5 and 11 could notably dose-dependently inhibit ROS productions in HaCaT keratinocyte cells without cytotoxicity in the concentration range of 0.2–20?μM. In cell-free mushroom tyrosinase assay, compounds 1–5, 10 and 11 had more potential anti-tyrosinase activities with IC₅₀ values of 106.9–255.6?μM than arbutin that were similar to predicted values of binding affinity calculated by molecule docking. The most active 2 had hydrogen bonds (Ser77, Glu309, Phe454) and electrostatic charges (Glu309, Glu248) interactions with mushroom tyrosinase, respectively. Our data manifested that T. truncata and its components are potentially to be developed as anti-aging and whitening agents for skin disorders.     

Carbon materials for high-performance lithium-ion capacitor

As new-generation electrochemical energy-storage systems, lithium-ion capacitors (LICs) have combined the advantages of both lithium-ion batteries and supercapacitors, manifesting the merits of high-energy density under power density. Triggered by outstanding physicochemical characteristics and two different charge-storage mechanisms (including the Li⁺ insertion and electric double-layer capacitor characteristics), carbon materials have been intensively studied for fabricating high-performance LICs. However, the construction of high-performance LICs have been greatly limited by the unbalanced capacity and kinetic imbalance between the sluggish ion diffusion process of anode and fast electrostatic accumulation behavior of cathode. Thus, aimed at improving two different electrochemical storage performances, rational design of carbon materials has been summarized in this short review, which provide the directional guidance for engineering optimized carbon electrodes and become a breakthrough for improving energy/power densities of LICs. Furthermore, the prospects and unresolved scientific issues of LICs are also proposed.     

Chiral metal phosphonates: assembly,structures and functions

As an important class of inorganic-organic hybrid materials, metal phosphonates can exhibit versatile structures, interesting functions and high water and thermal stabilities. Despite a large number of metal phosphonates reported in the past two decades,the development of chiral metal phosphonates is still in its infancy. This review summarizes the current status in this topical field including the synthetic strategies, the crystal structures of chiral metal phosphonates reported thus far, and their physical and chemical properties. Future challenges in this promising field are also discussed.     

Diketopyrrolopyrrole-Au(I) as singlet oxygen generator for enhanced tumor photodynamic and photothermal therapy

Diketopyrrolopyrrole(DPP) derivatived photosensitizers(PSs) with near infrared(NIR) absorption and good photophysical properties have drawn tremendous attention in cancer phototherapy. However, current DPP derivatives present unsatisfactory quantum yield of singlet oxygen(~1O_2) due to the large energy gap between the excited singlet and triplet states. To tackle this challenge, herein the DPP core is functionalized with triphenylphosphine-Au(I) group(Th DPP-Au), leading to a high~1O_2 quantum yield of 0.65. Theoretical calculation attributes the enhancement to spin-orbit coupling and population of the triplet excition upon photoexcitation. The hydrophilic Th DPP-Au nanoparticals(NPs) are prepared via nano-reprecipitation, which displays homogeneous size and excellent light absorption ability(ε=4.382×10~4 M~(-1)cm~(-1)). And the Th DPP-Au NPs exhibit low dark toxicity and high phototoxicity, which can effectively kill tumor cells via ~1O_2 induced mitochondrial apoptotic pathway upon irradiation. Furthermore, in vivo experiments demonstrate that Th DPP-Au NPs can selective accumulation in tumor and present excellent synergistic photodynamic/photothermal therapy guided by fluorescence and photothermal dual imaging.     

Intramolecular Electrophilic Aromatic Substitution in Gas-phase Fragmentation of Protonated N-Benzylbenzaldimines

In this study, the gas-phase fragmentations of protonated N-benzylbenzaldimines were investigated by electrospray ionization tandem mass spectrometry (ESI-MSⁿ). Upon collisional activation, several characteristic fragment ions are produced and their fragmentation mechanisms are rationalized by electrophilic aromatic substitution accompanied by benzyl cation transfer. (1) For N-(p-methoxybenzylidene)-1-phenylmethanimine, concomitant with a loss of HCN, a product ion at m/z 121 was observed. It is proposed to be generated from electrophilic substitution at the ipso-position by transferring benzyl cation rather than cleavage of the C-N double bond. (2) For N-(m-methoxybenzylidene)-1-phenylmethanimine, a product ion at m/z 209 was obtained, corresponding to the elimination of NH₃ carrying two hydrogens from the two aromatic rings respectively. This process can be rationalized by two sequential electrophilic substitutions and cyclodeamination reaction based on the benzyl cation transfer. Deuterium-labeled experiments, density functional theory (DFT) calculation and substituent effect results also corroborate the proposed mechanism. Figure a

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Effects of kaolin on the thermal stability and flame retardancy of polypropylene composite

Kaolin clay was introduced into an intumescent flame retardant (IFR) system containing ammonium polyphosphate as an acid source and pentaerythritol as a carbonization agent in order to improve the thermal stability and flame retardancy of polypropylene (PP) composite. The flame retardancy and smoke suppression was evaluated by the limiting oxygen index, vertical burning UL‐94, and cone calorimeter (CONE) tests. The limiting oxygen index value was increased from 30 to 33 at the presence of 2 phr kaolin. The peak heat release rate value decreased from 1002 kW/m² of neat PP to 318 kW/m² of PP/40 phr IFR and then to 222 kW/m² of PP/38 phr IFR/2 phr kaolin. The time of the peak heat release rate was significantly prolonged after the introduction of kaolin. The morphology of char after combustion was characterized by a scanning electron microscope, and it revealed more compact char structure that was obtained at the presence of kaolin. The mechanism of kaolin on improving the retardancy and smoke suppression of PP/IFR composite was proposed on the basis of X‐ray photoelectron spectroscopy analysis. Copyright © 2014 John Wiley & Sons, Ltd.     

Reduced operating voltage in nanotube‐shaped Ge2Sb2Te5 unites by nanosphere lithography

Ge₂Sb₂Te₅ Units for Phase Change Memory are fabricated on 2‐dimesional polystyrene (PS) template in a magnetron sputtering system. SEM and TEM observations show the Ge₂Sb₂Te₅ nanotubes form on the 200 nm PS beads which are etched for 30 s. And the lengths of the nanotubes are tuned by the film deposition. HRTEM and the electron diffraction measurements confirm the phase transition between the amorphous and the crystallized state. Resistance–voltage measurements show the operating voltage of the Ge₂Sb₂Te₅ nanotube‐shaped unit is reduced due to the small contact area with the bottom electrode, which indicates its potential applications for phase change memory.     

Silica‐particle‐supported zwitterionic polymer monolith for microcolumn liquid chromatography

A silica‐particle‐supported zwitterionic polymeric monolithic column, shortened as supported column (S‐column), was prepared by the in situ polymerization of methacrylic acid, ethylene dimethacrylate, and 2‐(dimethylamino)ethyl methacrylate in the presence of a ternary porogenic solvent containing water, methanol, and cyclohexanol in a 250 μm id fused‐silica capillary prepacked with 5 μm bare silica particles. In the S‐column, a thin layer of the polymers was formed around the silica particles in the form of nanoglobules, leaving the interstitial spaces between the particles free for liquid flow. The effects of the preparation conditions on the morphology of the monolith were investigated by scanning electron microscopy and backpressure measurements. The selected volumetric ratio of porogens, monomer concentration, polymerization time, and temperature are 1:1:8 (water/methanol/cyclohexanol), 25% v/v, 5 h, and 60°C, respectively. The S‐column was evaluated by comparison with its conventional organic counterpart in terms of morphology, mechanical stability, permeability, swelling–shrinking behavior, capacity, and efficiency. The results demonstrate that the S‐column is superior to its counterpart in all the terms with the exception of permeability. The above merits and zwitterionic property of the S‐column were further confirmed by separate separations of four inorganic anions and three organic cations.     

Self-assembly of core-satellite gold nanoparticles for colorimetric detection of copper ions

Molecule-coated nanoparticles are hybrid materials which can be engineered with novel properties. The molecular coating of metal nanoparticles can provide chemical functionality, enabling assembly of the nanoparticles that are important for applications, such as biosensing devices. Herein, we report a new self-assembly of core-satellite gold nanoparticles linked by a simple amino acid l-Cysteine for biosensing of Cu²⁺. The plasmonic properties of core-satellite nano-assemblies were investigated, a new red shifted absorbance peak from about 600 to 800 nm was found, with specific wavelength depending on ratios with assembly of large and small gold nanoparticles. The spectral features obtained using surface-enhanced Raman spectroscopy (SERS) provided strong evidence for the assembly of the Cu²⁺ ions to the L-Cysteine molecules leading to the successful formation of the core-satellite Cu(l-Cysteine) complex on the gold surfaces. In addition, a linear relationship between the concentration of mediating Cu²⁺ and absorbance of self-assembled gold nanoparticles (GNPs) at 680 nm was obtained. These results strongly address the potential strategy for applying the functionalized GNPs as novel biosensing tools in trace detections of certain metal ions.