Recombination System Based on Cre α Complementation and Leucine Zipper Fusions

A gene encoding β-1,3-1,4-glucanase was cloned by polymerase chain reaction (PCR) from Bacillus subtilis MA139. Sequencing result showed 97% homology to the corresponding gene from Bacillus licheniformis. The open reading frame (ORF) of the gene contained 690 bp coding for a 226 amino-acid matured protein with the estimated molecular weight of 24.44 kDa. The β-1,3-1,4-glucanase gene was subcloned into an expression vector of pET28a and expressed in Escherichia coli BL21 and then purified by metal affinity chromatography using a nickel–nitrilotriacetic acid (Ni–NTA) column. The purified β-1,3-1,4-glucanase demonstrated 24.05 and 12.52 U ml^-1 activities for the substrates of barley β-glucan and lichenan, respectively, and the specific activities were 728.79 and 379.1 U mg^-1 for them, respectively. The optimal temperature and pH of the purified enzyme were 40°C and 6.4, respectively. When barley β-glucan was used as the substrate, K _m was 5.34 mg ml^-1, and K _cat showed 7,206.71 S^-1, thus the ratio of K _cat and K _m was 1,349.67 ml s^-1 mg^-1. The activity of β-1,3-1,4-glucanase was affected by a range of metal ions or ethylenediaminetetraacetic acid (EDTA).     

Aptamer-based sensor for diclofenac quantification using carbon nanotubes and graphene oxide decorated with magnetic nanomaterials

In this contribution, a novel label-free electrochemical biosensor for diclofenac (DCF) detection was developed using the unique properties of acid-oxidized carbon nanotubes (CNT), graphene oxide (GO), and Fe₃O₄ magnetic nanomaterials. The GO sheets and CNT were interlinked by ultrafine Fe₃O₄ nanoparticles forming three-dimensional (3D) architectures. The characterization of the nanocomposite was studied by scanning electron microscopy (SEM), energy-dispersive X-ray (EDS), and wavelength-dispersive X-ray (WDX) spectroscopy. Initially, aminated detection probe (aptamer) was surface-confined on the CNT/GO/Fe₃O₄ nanocomposite via the covalent amide bonds formed by the carboxyl groups on the CNT/GO and the amino groups on the oligonucleotides at the 5′ end. Our constructed folding-based electrochemical sensor was used for detection of target molecule utilizing structure-switching aptamers. Signaling arose from changes in electron transfer efficiency upon target-induced changes in the conformation of the aptamer probe. These changes were readily monitored using differential pulse voltammetry technique. This sensor exhibited binding affinities ranging from 100 to 1300 pM with a low detection limit of 33 pM.     

Synthesis,structure, and electrochemistry of pyridinecarboxamide cobalt(III) complexes; the effect of bridge substituents on the redox properties

Two series of complexes of the types trans-[Co^III(Mebpb)(amine)₂]ClO₄ {Mebpb²⁻ = N,N-bis(pyridine-2-carboxamido)-4-methylbenzene dianion, and amine = pyrrolidine (prldn) (1a), piperidine (pprdn) (2a), morpholine (mrpln) (3a), benzylamine (bzlan) (4a)}, and trans-[Co^III(cbpb)(amine)₂]X {cbpb²⁻ = N,N-bis(pyridine-2-carboxamido)-4-chlorobenzene dianion, and amine = pyrrolidine (prldn), X = PF₆ (1b), piperidine (pprdn), X = PF₆ (2b), morpholine (mrpln), X = ClO₄ (3b), benzylamine (bzlan), X = PF₆ (4b)} have been synthesized and characterized by elemental analyses, IR, UV–Vis, and ¹H NMR spectroscopy. The crystal structure of 1a has been determined by X-ray diffraction. The electrochemical behavior of these complexes, with the goal of evaluating the effect of axial ligation and equatorial substitution on the redox properties, is also reported. The reduction potential of Co^III, ranging from −0.53 V for (1a) to −0.31 V for (3a) and from −0.48 V for (1b) to −0.22 V for (3b) show a relatively good correlation with the σ-donor ability of the axial ligands. The methyl and chloro substituents of the equatorial ligand have a considerable effect on the redox potentials of the central cobalt ion and the ligand-centered redox processes.     

Crystal growth of thin [Zn<Subscript>2</Subscript>(H<Subscript>2</Subscript>N-BDC)<Subscript>2</Subscript>(4-bpdb)] · 3DMF metal–organic framework nanostructure on functionalized surfaces: study of structure effect on methyldopa adsorption affinity

Thin films of a three-dimensional porous Zn(II)-based metal–organic framework, [Zn₂(NH₂-BDC)₂(4-bpdb)] · 3DMF (TMU-17-NH₂), containing azine-functionalized pores, were deposited on surfaces of silk fiber via a stepwise manner. The effect of sequential dipping steps in growth of TMU-17-NH₂ has been studied. These systems depicted a decrease in the size accompanying a decrease in the sequential dipping steps. The TMU-17-NH₂ has been used as matrices for the adsorption and in vitro guest delivery of methyldopa (MD).     

Synthesis of 2‐Oxopyridine‐Fused 1,3‐Diazaheterocyclic Compounds via a Three‐Component Reaction

An efficient and simple route for the preparation of 2‐oxopyridine‐fused 1,3‐diazaheterocyclic compounds via a three component reaction is described. It involves the reaction between alkylenediamines 1 , 1,1‐bis(methylsulfanyl)‐2‐nitroethene, and alkyl prop‐2‐ynoates 2 in refluxing THF (Table). The structures were corroborated by spectroscopic (IR, ¹H‐ and ¹³C‐NMR, and EI‐MS) and elemental analyses. A plausible mechanism for this type of cyclization is proposed (Scheme).     

A novel and efficient solvent-free and heterogeneous method for the synthesis of primary, secondary and bis-N-acylsulfonamides using metal hydrogen sulfate catalysts

Some metal hydrogen sulfates were used as acid catalysts in the N-acylation of different sulfonamides using carboxylic acid chlorides and anhydrides as acylating agents under both heterogeneous and solvent-free conditions. Al(HSO₄)₃ and Zr(HSO₄)₄ were found to have the highest activity and catalyze the reactions efficiently to furnish the primary N-acyl sulfonamides (RCONHSO₂R′), secondary N-acylsulfonamides (RCONR″SO₂R′) and bis-N-acylsulfonamnides [RCO(SO₂R′)N-R″-N(SO₂R′)COR] in good to high yield. The mild reaction conditions, inexpensive and low toxicity of catalysts and easy work-up procedure make this method attractive.     

Identifying the Interfacial Polarization in Non-stoichiometric Lead-Free Perovskites by Defect Engineering

Recent advances in perovskite ferroelectrics have fostered a host of exciting sensors and actuators. Defect engineering provides critical control of the performance of ferroelectric materials, especially lead-free ones. However, it remains a challenge to quantitatively study the concentration of defects due to the complexity of measurement techniques. Here, a feasible approach to analyzing the A-site defect and electron in alkali metal niobate is demonstrated. The theoretical relationships among defect concentration, conductivity, and oxygen partial pressure can be established based on the defect chemistry equilibria. The type and concentration of defects are reflected through the conductivity variation with oxygen partial pressure. As a result, the variation of defect concentration gives rise to defect-driven interfacial polarization, which further leads to distinct properties of the ceramics. e.g., abnormal dielectric behavior. Furthermore, this study also suggests a strategy to manipulate defects and charges in perovskite oxides for performance optimization.