2-Pyridyl-benzimidazole-Pd(II)/Pd(0) Supported on Magnetic Mesoporous Silica: Aerobic Oxidation of Benzyl Alcohols/Benzaldehydes and Reduction of Nitroarenes

Catalysis Surveys from Asia - 2-(2-Pyridyl)benzimidazole (PyBzIm) was supported onto magnetic mesoporous silica, Fe3O4@SiO2@SBA-15 via the click chemistry. The supported ligand was treated with...     

Luciferin‐Regenerating Enzyme Mediates Firefly Luciferase Activation Through Direct Effects of D‐Cysteine on Luciferase Structure and Activity

Luciferin‐regenerating enzyme (LRE) contributes to in vitro recycling of D‐luciferin. In this study, reinvestigation of the luciferase‐based LRE assay is reported. Here, using quick change site‐directed mutagenesis seven T‐LRE (Lampyris turkestanicusLRE) mutants were constructed and the most functional mutant of T‐LRE (T⁶⁹R) was selected for this research and the effects of D‐ and L‐cysteine on T⁶⁹R T‐LRE‐luciferase‐coupled assay are examined. Our results demonstrate that bioluminescent signal of T⁶⁹R T‐LRE‐luciferase‐coupled assay increases and then reach equilibrium state in the presence of 5 mm D‐cysteine. In addition, results reveal that 5 mm D‐ and L‐cysteine in the absence of T⁶⁹R T‐LRE cause a significant increase in bioluminescence intensity of luciferase over a long time as well as decrease in decay rate. Based on activity measurements, far‐UV CD analysis, ANS fluorescence and DLS (Dynamic light scattering) results, D‐cysteine increases the activity of luciferase due to weak redox potential, antiaggregatory effects, induction of changes in conformational structure and kinetics properties. In conclusion, in spite of previous reports on the effect of LRE on luciferase bioluminescent intensity, the majority of increase in luciferase light output and time‐course originate from the direct effects of D‐cysteine on structure and activity of firefly luciferase.     

Synthetic magnetic opals

We present studies of novel nanocomposites of BiNi impregnated into the structure of opals as well as inverse opals. Atomic force microscopy and high resolution elemental analyses show a highly ordered structure and uniform distribution of the BiNi filler in the matrix. These BiNi-based nanocomposites are found to exhibit distinct ferromagnetic-like ordering with transition temperature of about 675 K. As far as we know there exists no report in literature on any BiNi compound which is magnetic.     

Graphene and Graphene/Polymer Composites as the Most Efficient Protective Coatings for Steel,Aluminum and Copper in Corrosive Media: A Review of Recent Studies

The metal corrosion is considered as a severe threat to the national economy and industry structure, capable of triggering significant economic losses and severe damages, involving innumerable fields in daily life and industries. This review provides an overview of the physioelectrochemical studies on anticorrosive properties of various types of graphene coatings. Required electrochemical techniques for the investigation of anticorrosive efficiency, various types of graphene‐based materials coatings along with different routes to provide desirable coated layers are discussed in detail. After all, we intend to show that the modified graphene nanosheets can be regarded as effective protective layers against metal corrosion not only because of their extraordinary mechanical strength and toughness, which can be reached with a vastly thin layer, but also for their high transparency, cost‐efficiency and stability.     

On the Loewy Length and the Noetherian Dimension of Artinian Modules

The problem of computing the automorphism groups of an elementary Abelian Hadamard difference set or equivalently of a bent function seems to have attracted not much interest so far. We describe some series of such sets and compute their automorphism group. For some of these sets the construction is based on the nonvanishing of the degree 1-cohomology of certain Chevalley groups in characteristic two. We also classify bent functions f such that Aut(f) together with the translations from the underlying vector space induce a rank 3 group of automorphisms of the associated symmetric design. Finally, we discuss computational aspects associated with such questions.     

A host-guest optical sensor for aliphatic amines based on lipophilic cyclodextrin

A host-guest optical sensor for the determination of aliphatic amines as exemplified by octylamine is proposed. It is based on the reversible fluorescence enhancement of heptakis(2,6-di-O-isobutyl)-β-cyclodextrin(DOB-β-CD) hosting tetraphenylporphyrin (TPP) immobilized in poly(vinyl chloride) (PVC) membrane by aliphatic amine extracted from aqueous phase into membrane phase. The optimum membrane contained 1.15 wt % TPP, 6.15 wt % DOB-β-CD as sensing reagent and other membrane materials. The fluorescence enhancement of the membrane resulted from the formation of a stable three-component complex among DOB-β-CD, TPP, and aliphatic amines. With the optimum conditions described, the fluorescence response of the sensor to octylamine shows a good correlation with the theoretically derived equation in the range 1.0 × 10^–6 to 8.0 × 10^–4 mol/L. The response characteristics including reversibility, response time, reproducibility and lifetime and selectivity of this optical device are also discussed in detail. This sensor has also been applied for the determination of octylamine in water samples containing interferents with satisfactory recovery.     

Thiol-dependent serine alkaline proteases from Bacillus sp. HR-08 and KR-8102

Two Bacillus sp. strains, HR-08 and KR-8102, isolated from soil of the west and north parts of Iran were screened on gelatin agar medium for their ability to produce alkaline protease. The enzymes were active in a wide pH range (6.0–11.0) and stable in the alkaline range (7.0–12.0). The optimum temperatures for the protease from HR-08 and KR-8102 were 65 and 50°C, respectively. The irreversible thermoinactivation of HR-08 and KR-8102 proteases showed that the stability of HR-08 enzyme was higher than that of KR-8102 and the half-lives of these enzymes were 95 and 32 min at 50°C, respectively. In the presence of 10 mM Ca²⁺, HR-08 retained 100, 90, and 20% of its initial activity after heating for 30 min at 50, 60, and 70°C, respectively. Enzymes were inhibited by phenylmethylsulfonyl fluoride and iodoacetate. After inhibition by iodoacetate, both enzymes were reactivated by dithiothreitol. These data show that the enzymes seem to be thiol-dependent serine alkaline proteases. The enzymes especially from HR-08 were stable in the presence of H₂O₂, surfactants, and local detergents; their activities were enhanced in the presence of 5 mM Fe²⁺; and the presence of 5mM metal ions such as Mg²⁺, Cu²⁺, and Mn²⁺ produced almost no effect.     

The Effect of Surface Charge Saturation on Heat‐induced Aggregation of Firefly Luciferase

We present here the effect of firefly luciferase surface charge saturation and the presence of some additives on its thermal‐induced aggregation. Three mutants of firefly luciferase prepared by introduction of surface Arg residues named as 2R, 3R and 5R have two, three and five additional arginine residues substituted at their surface compared to native luciferase; respectively. Turbidimetric study of heat‐induced aggregation indicates that all three mutants were reproducibly aggregated at higher rates relative to wild type in spite of their higher thermostability. Among them, 2R had most evaluated propensity to heat‐induced aggregation. Therefore, the hydrophilization followed by appearing of more substituted arginine residues with positive charge on the firefly luciferase surface was not reduced its thermal aggregation. Nevertheless, at the same condition in the presence of charged amino acids, e.g. Arg, Lys and Glu, as well as a hydrophobic amino acid, e.g. Val, the heat‐induced aggregation of wild type and mutants of firefly luciferases was markedly decelerated than those in the absence of additives. On the basis of obtained results it seems, relinquishment of variety in charge of amino acid side chains, they via local interactions with proteins cause to decrease rate and extent of their thermal aggregation.