Synthesis, structures and magnetic properties of n=3 Ruddlesden-Popper compounds Ca4Mn3−xTaxO10 (0≤x≤0.3)

The structural and magnetic properties of Ta-doped Ca₄Mn_3−xTa_xO₁₀ (0≤x≤0.3) compounds have been investigated. Structural refinement indicates that the Ta doping maintains the orthorhombic layered perovskite structure with space group Pbca as Ca₄Mn₃O₁₀ but induces an increase in both unit cell volume and octahedral distortion. The magnetization measurements reveal that the magnetization first increases and reaches to maximum for the x=0.1 sample and then gradually decreases with the increase of Ta content. There appear short-range ferromagnetic (FM) clusters in all the doped samples, which are caused by the double-exchange interaction between Mn⁴⁺ and Mn³⁺ that is induced by the charge compensation effect. As x is higher than 0.1, the overall results show evidence for the gradual appearance of a cluster glass behavior. When x increases to 0.3, the long-range antiferromagnetic (AFM) ground state is melted into the short-range magnetically ordered regions due to the increase of Ta⁵⁺ and Mn³⁺ at the expense of Mn⁴⁺. The competition between AFM regions and FM clusters makes the short-range magnetic components frustrate when the temperature falls to a frustrating point, and thus cluster glass transition occurs.     

A novel immunosensor for carcinoembryonic antigen based on poly(diallyldimethylammonium chloride) protected prussian blue nanoparticles and double-layer nanometer-sized gold particles

A highly sensitive amperometric immunosensor has been developed for the detection of carcinoembryonic antigen (CEA). It is based on (a) Prussian Blue nanoparticles coated with poly(diallyldimethylammonium chloride) (P-PB) and (b) double-layer gold nanocrystals. The sensor was obtained by first electrodepositing porous gold nanocrystals on the glassy carbon electrode (GCE), and then by modifying the electrode with the coated P-PB. Subsequently, colloidal gold nanoparticles (nano-Au) were adsorbed onto the GCE by electrostatic interactions between the negatively charged nano-Au and the positively charged P-PB to immobilize CEA antibodies. Finally, bovine serum albumin was employed to block possible remaining active sites and to prevent the non-specific adsorption on the nano-Au. This immunosensor was characterized by cyclic voltammetry and scanning electron microscopy. The working range was adjusted to two concentration ranges, viz. from 0.5 to 10 ng.mL^?1, and from 10 to 120 ng.mL^?1 of CEA, with a detection limit of 0.2 ng.mL^?1 at three times the background noise.     

One‐Pot,Three‐Component Condensation of Aldehydes, 2‐Naphthol and 1,3‐Dicarbonyl Compounds

A practical and efficient procedure for the one‐pot multicomponent couping of aryl aldehydes, 2‐naphthol and cyclic 1,3‐dicarbonyl compounds using perchloric acid adsorbed on silica gel (HClO₄‐SiO₂) as a highly efficient, inexpensive, convenient, reusable heterogeneous catalyst under solvent‐free conditions has been developed. Various biologically important 12‐aryl‐8,9,10,12‐tetrahydrobenzo[a]xanthen‐11‐one derivatives have been efficiently synthesized in high to excellent yields. The present approach offers several advantages such as shorter reaction times, simple work‐up, excellent yields, low cost, and mild reaction conditions. Furthermore, the catalyst can be recovered simply and reused without appreciable loss of its catalytic activity.     

Cloning and Identification of a Novel P-II Class Snake Venom Metalloproteinase from <Emphasis Type="Italic">Gloydius halys</Emphasis>

Ahpfibrase was a new snake venom metalloproteinase (SVMP) which was cloned from Gloydius halys. The cDNA sequence with 1,891 base pairs encodes an open reading frame of 477 amino acids which includes a 17 amino acid signal peptide, plus a 171 amino acid segment of zymogen-like propeptide, a metalloproteinase domain of 200 amino acids, a spacer of 16 amino acids, and a disintegrin-like peptide of 73 amino acids. The metalloproteinase domain contained a conserved signature zinc-binding motif HEXXHXXGXXH in the catalytic region and a methionine-turn CIM. To determine the activity of ahpfibrase, the coding region including both the metalloproteinase domain and disintegrin region was amplified by PCR, inserted into the pET25b(+) vector, and expressed in Escherichia coli. The recombinant protein was recovered from inclusion bodies with 8 M urea and refolding was performed by fed-batch dilution method, and purified recombinant ahpfibrase showed the fibrinolytic activity and platelet aggregation–inhibition ability.     

Antibacterial Functionalization of Wool via mTGase-Catalyzed Grafting of ε-Poly-l-lysine

ε-Poly-l-lysine (ε-PL), a natural biomacromolecule having a broad spectrum of antibacterial activity, was grafted on the wool fiber via the acyl transfer reaction catalyzed by microbial transglutaminase (mTGase) to develop a new strategy for antibacterial functionalization of proteinous materials. The effects of the concentrations of ε-PLs and mTGases on the graft yields were investigated. A coating of ε-PL that almost completely covered the scale profile on the wool surface was visualized by scanning electron microscopy (SEM) and further demonstrated in terms of Allw?rden’s reaction characteristic of wool. Identifiable differences in lysine content and color depth among the stained wool samples reveal the changes in the surface composition and polarity caused by the incorporation of ε-PL onto the wool substrate, respectively. The ratio of bacteriostasis to Escherichia coli of the wool fabric grafting ε-PL reached 96.6 %, indicating an excellent antibacterial effect. The application of ε-PL and corresponding mTGase-catalyzed grafting reaction would provide a worthwhile reference for antibacterial functionalization of proteinous materials in various forms.     

Tuning the electrocatalytic activity of Pt nanoparticles on carbon nanotubes via surface functionalization

Polyelectrolytes with various characteristic functional groups as interlinkers to anchor Pt nanoparticles were used to functionalize carbon nanotubes (CNTs) as Pt electrocatalyst support. It was found that polyanions (poly(styrenesulfonic acid) (PSS), and poly(acrylic acid sodium) (PAA)) have a beneficial effect on methanol electrooxidation on Pt nanoparticles supported on carbon nanotubes via modifying their electronic structure through charge transfer from polyanions to Pt sites and supply of oxygen-containing species. The increased electron density around Pt sites by the charge transfer from polyanions would cause partial filling of Pt 5d-bands, resulting in the downshift of d-band center and weaker chemisorption with oxygen-containing species (e.g. CO_ad). The weakened chemisorption of CO on Pt nanoparticles would promote the methanol electrooxidation. On the contrary, polycations would have an opposite effect on the electronic structure and chemisorption properties of Pt nanoparticles.     

Acute oral toxicity and brine shrimp lethality of Elaeis guineensis Jacq., (oil palm leaf) methanol extract

Elaeis guineensis (Arecaceae) is widely used in West African traditional medicine for treating various ailments. An evaluation on the toxicity of extracts of this plant is crucial to support the therapeutic claims. The acute oral toxicity and brine shrimp lethality of a methanolic extract of this plant was tested. Oral administration of crude extract at the highest dose of 5,000 mg/kg resulted in no mortalities or evidence of adverse effects, implying that E. guineensis is nontoxic. Normal behavioral pattern, clinical signs and histology of vital organs confirm this evidence. The E. guineensis extracts screened for toxicity against brine shrimp had 50% lethal concentration (LC??) values of more than 1.0 mg/mL (9.00 and 3.87 mg/mL, at 6 and 24 h, respectively), confirming that the extract was not toxic. Maximum mortalities occurred at 100 mg/mL concentration while the least mortalities happened to be at 0.195 mg/mL concentration. The results of both tests confirm that E. guineensis is nontoxic and hence safe for commercial utilization.     

MimoDB: a new repository for mimotope data derived from phage display technology

Peptides selected from phage-displayed random peptide libraries are valuable in two aspects. On one hand, these peptides are candidates for new diagnostics, therapeutics and vaccines. On the other hand, they can be used to predict the networks or sites of protein-protein interactions. MimoDB, a new repository for these peptides, was developed, in which 10,716 peptides collected from 571 publications were grouped into 1,229 sets. Besides peptide sequences, other important information, such as the target, template, library and complex structure, was also included. MimoDB can be browsed and searched through a user-friendly web interface. For computational biologists, MimoDB can be used to derive customized data sets and benchmarks, which are useful for new algorithm development and tool evaluation. For experimental biologists, their results can be searched against the MimoDB database to exclude possible target-unrelated peptides. The MimoDB database is freely accessible at http://immunet.cn/mimodb/.     

One-step electrodeposition of platinum nanoflowers and their high efficient catalytic activity for methanol electro-oxidation

A facile, one-step and template-free electrodeposition method has been developed for the first time to prepare porous Pt nanoflowers. The flowerlike architectures were confirmed by SEM, and further structurally characterized by XRD and electrochemical analyses. Compared to conventional nanosized Pt catalysts, as-prepared Pt nanoflowers exhibit remarkably higher catalytic activity and stronger poisoning-tolerance for the methanol electro-oxidation, and thus they are anticipated to find interesting applications in many important fields such as energy and catalysis.