A Facile Strategy for Construction of Sensor for Detection of Ondansetron and Investigation of its Redox Behavior and Thermodynamic Parameters

A sodium dodecylsulfate‐doped polypyrrole (SDS‐PPy) film was elaborated on glassy carbon electrode (GCE) by an electrodeposition method in phosphate buffer solution (pH 2.0) containing pyrrole (Py) and sodium dodecyl sulfate (SDS). SDS‐PPy/GCE was used for the construction of sensor, which showed excellent electrochemical response for the detection of ondansetron (OND) compared to conventional PPy. The application of the square wave (SW), with the adsorptive accumulation, indicates a maximum response at 1.33 V in H₂SO₄ (0.5 M). The influence of experimental parameters on determination of OND is discussed. The adsorptive stripping technique showed to be more sensitive, giving responses twice as big as those of non‐accumulated OND. The substantial improvement of response permits the development of an electroanalytical technique with a linear concentration in the range (1.0–80 μM), low detection (0.09 μM), and quantification limits (0.3 μM), and acceptable relative standard deviations of repeatability (0.59 %), and reproducibility (1.51 %). Consequently, this electrode is promising candidate for an accurate electroanalytical determination of OND in pharmaceutical samples with high sensitivity and selectivity, good accuracy and precision. The electrooxidation of OND at SDS‐PPy/GCE at various temperatures were studied by cyclic voltammetry to evaluate both the kinetic (k_s and E_a) and thermodynamic (ΔG*, ΔH* and ΔS*) parameters.     

A Very Short and Efficient Total Synthesis of Otanthus Maritima Amide.

A new total synthesis of Otanthus Maritima amide 1 was achieved from 6-trimetylsily N-tert-butyl sorbaldimine 6 in 76% global yield. The natural product 1 was obtained in three steps by condensation of 6 on thiophenal in the presence of catalytic amount of CsF (10%) in DMSO followed by oxidation and amidification of the corresponding intermediate.     

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.     

A Novel Serine Metallokeratinase from a Newly Isolated <Emphasis Type="BoldItalic">Bacillus pumilus</Emphasis> A1 Grown on Chicken Feather Meal: Biochemical and Molecular Characterization

A keratinolytic enzyme (KerA1) secreted by a newly isolated Bacillus pumilus strain A1 cultivated in medium containing chicken feather meal was purified and characterized, and the gene was isolated and sequenced. The molecular mass of the purified enzyme was estimated to be 34,000 Da by sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis and gel filtration. The optimum pH and temperature for the purified keratinase were 9.0 and 60 °C, respectively, using keratin as a substrate. KerA1 showed a high stability towards nonionic surfactants. It was found to be relatively stable toward the strong anionic surfactant (SDS). The deduced amino acid sequence of the keratinase KerA1 differs from both the organic solvent tolerant protease of B. pumilus 115b and the dehairing protease of B. pumilus UN-31-C-42 by one and nine amino acids, respectively. These results suggest that this keratinase may be a useful alternative and ecofriendly route for handling the abundant amount of waste feathers and for applications in detergent formulations.     

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 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.     

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.     

Styrene cis—trans photoisomerisation treated through a Heisenberg non-empirical hamiltonian

Using a recently proposed non-empirical Heisenberg hamiltonian, the ground and excited covalent surfaces of the styrene molecule are calculated as functions of the external double-bond twisting angle θ, including full bond-length optimisation. The lowest excited singlet surface exhibits a barrier at 0 ?~ 45° resulting from a weakly avoided crossing of two neutral diabatic surfaces. The isomerisation should proceed from the twisted funnel. This model and the calculated transition energies are in good agreement with experiment.     

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.