New Thermostable Amylase from <Emphasis Type="Italic">Bacillus cohnii</Emphasis> US147 with a Broad pH Applicability

A new thermophilic bacterial strain identified as Bacillus cohnii US147 was isolated from the southern Tunisian soil. The identification was based on physiological tests and molecular techniques related to the 16S ribosomal ribonucleic acid. The isolated strain produced amylase, which was purified. This amylase had an apparent molecular mass of 30 kDa as estimated by sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis. Amylase US147 showed K _m and V _max values of 0.7 mg/ml and 2.2 U/ml, respectively, with starch as the substrate. The enzyme was active in acid and basic pH and had a maximal activity on starch at pH 9 and 70 °C. The enzyme was stable at pH 9 for 72 h and retained half of its activity after incubation at 70 °C for 150 min. A partially inhibition (15%, 25%, 23%, 20%, and 22%) was obtained with 1 mM SDS, 1 mM NaBO₃, 1 mM H₂O_2, 1 mM Zn⁺², and 5 mM ethylenediamine tetraacetic acid (EDTA), respectively. The amylase recovered its original activity by the addition of 10 mM Ca ²⁺ to the 5 mM EDTA. These properties indicated a possible use of this amylase in starch saccharification, in detergent, and in other industrial applications.     

CHARACTERIZATION OF NANOSTRUCTURES:TOOLS AND CHALLENGES

Apart from long-known and applied nanostructures like carbon black for tyres or pigments for coatings nanotechnology has created highly sophisticated structures used for nano/molecular electronics,diagnostics,drug delivery, UV-absorbers etc.Often the main question to be solved analytically is the local determination of tiny amounts of chemicals resulting in an ever increasing need for highly sensitive as well as locally resolved techniques.Applications of techniques like mass spectroscopy,transmission el...     

Synthese d'ethyleniques monofluores

Monofluorinated ethylenic compounds have been prepared by action of potassium tertiobutylate either on2-fluorotosylates or 2-fluorochlorides. In the case of 2-fluorochlorides the action, at higher temperature, of basic salt such as KF in ethylene glycol, may be used to prepare monofluorinated ethylenics compounds.     

掺杂Eu2O3的SrTiO3及SnO2光致发光

用具有大能隙的本征半导体(SrTiO₃及SnO₂)粉末作本体,分别掺杂1%(原子百分数)的Eu₂O₃;所得物质表现出Eu³⁺离子的线发射光谱特性,但相对发光强度及光谱形状有相当大的变化。X射线衍射结构分析显示Eu³⁺在SrTiO₃晶格里是处在间隙位置,而它在SnO₂晶格里则形成新物相Eu₂Sn₂O₇。     

N-Bromosuccinimide-thiol cobromination in basic medium: an efficient one-pot transformation of olefins into the corresponding enol thioethers

A convenient method for the one-pot conversion of olefins into the corresponding enol thioethers is reported. The products were obtained via the N-bromosuccinimide cobromination reaction of olefins with thiols in basic medium. Steric hindrance present in the product alkenes may explain the stereochemistry observed.     

α- to β-[C6H4(NH3)2]2Bi2I10 reversible solid-state transition, thermochromic and optical studies in the p-phenylenediamine-based iodobismuthate(III) material

α-[C₆H₄(NH₃)₂]₂Bi₂I₁₀, which is a new material containing low-dimensional iodobismuthate anions, was synthesized and through its single crystal X-ray diffraction measurements, was proven to crystallize at room temperature in the centrosymmetric space group P2₁/c. It consists of a p-phenylenediammonium dication and a discrete (0-D) anion built up of edge-sharing bioctahedron. Due to the hydrogen bonds and the interatomic distances (Bi-I, I?I and π-π) changes, α-phase was transformed into the corresponding centrosymmetric β-phase, β-[C₆H₄(NH₃)₂]₂Bi₂I₁₀, through a single-crystal to single-crystal transformation occurring upon cooling to −28/−26 °C. Below the transition temperature, β-[C₆H₄(NH₃)₂]₂Bi₂I₁₀ crystallizes in the monoclinic system, centrosymmetric space group P2₁/n. Besides, the optical transmission measurements on α-[C₆H₄(NH₃)₂]₂Bi₂I₁₀ thin films have revealed two absorption bands at 2.47 and 3.01 eV. Finally, two room temperature photoluminescence emissions attributed to excitons radiative recombinations confined within the bioctahedra Bi₂I₁₀⁴⁻, were observed in the red spectral range at 1.9 and 2.05 eV energy.     

Crystal structure of NH3(CH2)2NH3BiCl5·2H2O

The ethylenediammonium pentachlorobismuthate(III) dihydrate salt is monoclinic with the following unit cell dimensions: a = 10.902(8)Å, b = 7.926(6)Å, c = 15.199(6)Å, = 96.40(1)°, space group P2₁/n with Z = 4. The structure shows a layer arrangement parallel to the axis: planes of the [Bi₂Cl₁₀]^4– bioctahedra alternate with planes of [NH₃(CH₂)₂NH₃]²⁺ dications. The [Bi₂Cl₁₀]^4– bioctahedra are connected through O(W)–H··· Cl hydrogen bonds, so that infinite unidimensional chains of composition [Bi₂Cl₁₀(H₂O)₂] _n ^4n– are formed in the structure parallel to the axis. These chains are themselves interconnected by means of the N–H···Cl bonds originating from the [NH₃(CH₂)₂NH₃]²⁺ entities, forming a three-dimensional network.