Purification and characterization of two low molecular weight endoglucanases produced by Penicillium occitanis mutant pol 6

Two endoglucanases (EGs), EG A and EG B, were purified to homogeneity from Penicillium occitanis mutant Pol 6 culture medium. The molecular weights of EG A and EG B were 31,000 and 28,000 kDa, respectively. The pI was about 3 for EG A and 7.5 for EG B. Optimal activity was obtained at pH 3.5 for both endoglucanases. Optimal temperature for enzyme activity was 60 degrees C for EG A and 50 degrees C for EG B. EG A was thermostable at 60 degrees C and remained active after 1 h at 70 degrees C. EGs hydrolyzed carboxymethylcellulose, phosphoric acid swollen cellulose, and beta-glucan efficiently, whereas microcrystalline cellulose (Avicel) and laminarin were poorly hydrolyzed. Only EG B showed xylanase activity. Furthermore, these EGs were insensitive to the action of glucose and cellobiose but were inhibited by the divalent cations Hg2+, Co2+, and Mn2+.     

Enhanced ethanol sensing properties of WO3 modified TiO2 nanorods

Pristine and WO₃ decorated TiO₂ nanorods (NRs) were synthesised to investigate n-n-type heterojunction gas sensing properties. TiO₂ NRs were fabricated via hydrothermal method on fluorine-doped tin oxide coated glass (FTO) substrates. Then, tungsten was sputtered on the TiO₂ NRs and thermally oxidised to obtain WO₃ nanoparticles. The heterostructure was characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) spectroscopy. Fabricated sensor devices were exposed to VOCs such as toluene, xylene, acetone and ethanol, and humidity at different operation temperatures. Experimental results demonstrated that the heterostructure has better sensor response toward ethanol at 200 °C. Enhanced sensing properties are attributed to the heterojunction formation by decorating TiO₂ NRs with WO₃.     

Purification and Biochemical Characterization of an Acid-Stable Lipase from the Pyloric Caeca of Sardine (Sardinella aurita)

A lipolytic activity was located in the sardine digestive glands (pyloric caeca), from which a sardine digestive lipase (SaDL) was purified. Pure SaDL has a molecular mass of 43 kDa as determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis. The enzyme was found to be more active on short-chain triacylglycerols than on long-chain ones. SaDL does not present the interfacial activation phenomenon. Control experiments were performed under the same experimental conditions, with dromedary and turkey pancreatic lipases and showed a positive interfacial activation phenomenon. Sodium deoxycholate (NaDC) has an inhibitory effect on the lipase activity. The pure enzyme lost 40% of its activity in presence of 8 mM NaDC. SaDL was found to be mostly stable at low pH values. Interestingly, no colipase was detected in the sardine pyloric caeca. Analogous results were reported for the scorpion and the crab digestive systems. This is in line with the idea that colipase might has evolved in mammal animals simultaneously with the appearance of an exocrine pancreas. No similarity was found between the NH₂-terminal amino acid residues of SaDL and those of lipases from the digestive tract of other species. Altogether, these results suggest that SaDL is a member of a new group of lipases belonging to aquatic species.     

Changes in the morphology of interstellar ice analogues after hydrogen atom exposure

The morphology of water ice in the interstellar medium is still an open question. Although accretion of gaseous water could not be the only possible origin of the observed icy mantles covering dust grains in cold molecular clouds, it is well known that water accreted from the gas phase on surfaces kept at 10 K forms ice films that exhibit a very high porosity. It is also known that in the dark clouds H(2) formation occurs on the icy surface of dust grains and that part of the energy (4.48 eV) released when adsorbed atoms react to form H(2) is deposited in the ice. The experimental study described in the present work focuses on how relevant changes of the ice morphology result from atomic hydrogen exposure and subsequent recombination. Using the temperature-programmed desorption (TPD) technique and a method of inversion analysis of TPD spectra, we show that there is an exponential decrease in the porosity of the amorphous water ice sample following D-atom irradiation. This decrease is inversely proportional to the thickness of the ice and has a value of ?(0) = 2 × 10(16) D-atoms cm(-2) per layer of H(2)O. We also use a model which confirms that the binding sites on the porous ice are destroyed regardless of their energy depth, and that the reduction of the porosity corresponds in fact to a reduction of the effective area. This reduction appears to be compatible with the fraction of D(2) formation energy transferred to the porous ice network. Under interstellar conditions, this effect is likely to be efficient and, together with other compaction processes, provides a good argument to believe that interstellar ice is amorphous and non-porous.     

13C NMR study of N-unsubstituted aziridines: I—steric effects,pseudoconjugation

¹³C chemical shifts for twenty-nine alkyl and phenyl substituted N-unsubstituted aziridines have been measured. Additivity parameters for methyl, phenyl and aziridyl carbons have been derived with the aim of testing the consistency of the assignments made on the basis of chemical shift considerations and off-resonance decoupling information. The observed chemical shifts are discussed in terms of steric and pseudoconjugation effects.     

Crystal structure of penthylenediammonium pentachlorothallate(III)

The penthylenediammonium pentachlorothallate(III) salt is orthorhombic with the following unit cell dimensions: a = 7.696(3) Å, b = 13.2890(17) Å, and c = 13.503(18) Å, space group P2₁2₁2₁ with Z = 4. The structure was solved by Patterson methods and refined to a final R value of 0.0387 for 1991 observed reflections. The structure consists of penthylenediammonium cations and polynuclear anions in which slightly distorted [TlCl₆]^3– octahedral sharing two vertices are interconnected into chains. These chains are themselves interconnected by means of the N–HCl bonds originating from the [NH₃(CH₂)₅NH₃]²⁺ entities forming a three-dimensional network.     

Crystal structure of pentakis ethylenediammonium bis undecachlorodiantimonate(III) tetrahydrate, (NH3(CH2)2NH3)5(Sb2Cl11)2·4H2O

The pentakis ethylenediammonium bis undecachlorodiantimonate(III) tetrahydrate salt is monoclinic with the following unit cell dimensions:a=16.271(5) Å,b=13.004(4) Å,c=13.932(4) Å, β=111.72(2)°, space groupP2₁/c withZ=2. The structure was solved by Patterson methods and refined to a finalR value of 0.023 for 4435 reflections withF ₀>4σ(F ₀). The structure shows a layer arrangement perpendicular to thea axis: planes of the [Sb₂Cl₁₁]⁵⁻ bioctahedra alternate with planes of [NH₃(CH₂)₂NH₃]²⁺ dications. The [Sb₂Cl₁₁]⁵⁻ bioctahedra are connected through O−H...Cl hydrogen bonds, such that infinite chains of composition [Sb₂Cl₁₁(H₂O]_n ⁵ⁿ⁻ are formed in the structure, parallel to the twofold axis. These chains are themselves interconnected by means of N−H...Cl and O−H...Cl bonds originating from the [NH₃(CH₂)₂NH₃]²⁺ entities and the water molecules, respectively, and form a threedimensional network.     

Crystal structure of NH3(CH2)2NH3(BiI4)2·4H2O

The ethylenediammonium bis tetraiodobismuthate(III) tetrahydrate salt is monoclinic with the following unit cell dimensions:a=7.476(3)Å,b=13.194(3)Å,c=13.916(9)Å, β=95.22(6)°, space groupP2₁ lc withZ=2. The structure consists of disordered ethylenediammonium cations, water molecules and polynuclear anions in which slightly distored [BiI₆]^3? octahedra sharingcis edges are interconnected into chains. The [BiI₄]^? anions are connected through O(W2)?H...I hydrogen bonds, so that infinite two dimensional chains parallel to thea axis with anionic period [BiI₄(H₂O)]^? are formed in the structure. These chains are themselves interconnected by means of the O?H...I and N...O(I) bonds originating respectively from the water molecules and the ethylenediammonium entities, forming a three-dimensional network.