Purification and Preliminary X-Ray Crystallographic Analysis of the Peptidyl-Prolyl cis–trans Isomerase Alr5059 from Anabaena sp. PCC 7120

Crystallography Reports - Peptidyl-prolyl cis–trans isomerases (PPIases) have a wide range of functions in all cells. They are typically classified as cyclophilin, the FK506-binding...     

Study of martensite transformation and microstructural evolution of Cu–Al–Ni–Fe shape memory alloys

In this study, variations in the transformation temperature, crystal structure, and microstructure of the arc melted alloy having nominal composition of Cu–13%Al–4%Ni–4%Fe (in mass%) were investigated for two different treatment conditions, homogenized and heat treated at 950 °C for 1 h. For both conditions, transformation temperature of the alloy was examined by DSC and it was determined as ~200 °C, similar to the value for Cu–Al–Ni alloys given in the literature. The crystal structure of the martensite Cu–13%Al–4%Ni–4%Fe (in mass%) alloy was identified as 18R using XRD. By heat treatment performed at 950 °C, diffraction peaks become more distinct. The microstructure of the alloy was studied with the help of optical microscope as a result of which parallel martensite plates and precipitates were detected. Microhardness value of the alloy was found as 361 and 375 Hv for homogenized and heat-treated conditions, respectively.     

Estimation of Magnetization Properties of the Ferromagnetic Poly-Granular Beds

In this article, magnetizing properties of the packed beds that are constructed from the mixture of the ferromagnetic spheres of various sizes, pieces of wires and chips are investigated both experimentally and theoretically in order to determine the effect of the volumetric packing factor on the magnetizing properties of the bed. The average magnetizing curve has been determined by maintaining the external homogeneous magnetic field (H) higher than 150 kA/m.     

Well parameters of two‐dimensional electron gas in Al0.88In0.12N/AlN/GaN/AlN heterostructures grown by MOCVD

Resistivity and Hall effect measurements were carried out as a function of magnetic field (0‐1.5 T) and temperature (30‐300 K) for Al_0.88In_0.12N/AlN/GaN/AlN heterostructures grown by Metal Organic Chemical Vapor Deposition (MOCVD). Magnetic field dependent Hall data were analyzed by using the quantitative mobility spectrum analysis (QMSA). A two‐dimensional electron gas (2DEG) channel located at the Al_0.88In_0.12N/GaN interface with an AlN interlayer and a two‐dimensional hole gas (2DHG) channel located at the GaN/AlN interface were determined for Al_0.88In_0.12N/AlN/GaN/AlN heterostructures. The interface parameters, such as quantum well width, the deformation potential constant and correlation length as well as the dominant scattering mechanisms for the Al_0.88In_0.12N/GaN interface with an AlN interlayer were determined from scattering analyses based on the exact 2DEG carrier density and mobility obtained with QMSA. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

A computational study on the amine-oxidation mechanism of monoamine oxidase: insight into the polar nucleophilic mechanism

The proposed polar nucleophilic mechanism of MAO was investigated using quantum chemical calculations employing the semi-empirical PM3 method. In order to mimic the reaction at the enzyme's active site, the reactions between the flavin and the p-substituted benzylamine substrate analogs were modeled. Activation energies and rate constants of all the reactions were calculated and compared with the published experimental data. The results showed that electron-withdrawing groups at the para position of benzylamine increase the reaction rate. A good correlation between the log of the calculated rate constants and the electronic parameter (sigma) of the substituent was obtained. These results agree with the previous kinetic experiments on the effect of p-substituents on the reduction of MAO-A by benzylamine analogs. In addition, the calculated rate constants showed a correlation with the rate of reduction of the flavin in MAO-A. In order to verify the results obtained from the PM3 method single-point B3LYP/6-31G*//PM3 calculations were performed. These results demonstrated a strong reduction in the activation energy for the reaction of benzylamine derivatives having electron-withdrawing substituents, which is in agreement with the PM3 calculations and the previous experimental QSAR study. PM3 and B3LYP/6-31G* energy surfaces were obtained for the overall reaction of benzylamine with flavin. Results suggest that PM3 is a reasonable method for studying this kind of reaction. These theoretical findings support the proposed polar nucleophilic mechanism for MAO-A.     

Nonlinear experimental dye-doped nematic liquid crystal optical transmission spectra estimated by neural network empirical physical formulas

In this paper, two complementary objectives related to optical transmission spectra of nematic liquid crystals (NLCs) were achieved. First, at room temperature, for both pure and dye (DR9) doped E7 NLCs, the 10-250 W halogen lamp transmission spectra (wavelength 400-1200 nm) were measured at various bias voltages. Second, because the measured spectra were inherently highly nonlinear, it was difficult to construct explicit empirical physical formulas (EPFs) to employ as transmittance functions. To avoid this difficulty, layered feedforward neural networks (LFNNs) were used to construct explicit EPFs for these theoretically unknown nonlinear NLC transmittance functions. As we theoretically showed in a previous work, a LFNN, as an excellent nonlinear function approximator, is highly relevant to EPF construction. The LFNN-EPFs efficiently and consistently estimated both the measured and yet-to-be-measured nonlinear transmittance response values. The experimentally obtained doping ratio dependencies and applied bias voltage responses of transmittance were also confirmed by LFFN-EPFs. This clearly indicates that physical laws embedded in the physical data can be faithfully extracted by the suitable LFNNs. The extraordinary success achieved with LFNN here suggests two potential applications. First, although not attempted here, these LFNN-EPFs, by such mathematical operations as derivation, integration, minimization etc., can be used to obtain further transmittance related functions of NLCs. Second, for a given NLC response function, whose theoretical nonlinear functional form is yet unknown, a suitable experimental data based LFNN-EPF can be constructed to predict the yet-to-be-measured values.     

The Effect of pH and Temperature on the Sorption of Zinc(II), Cadmium(II), and Aluminum(III) onto New Metal-Ligand Complexes of Sporopollenin

Sorption of metal ions from aqueous solution onto metal-ligand complexes of sporopollenin derivatives has been measured as a function of pH at several temperatures between 20 and 50°C. Novel metal-ligand exchange resins possessing oxime and carboxylic acid sidearm functionality were prepared through the reaction of diaminosporopollenin with dichloro-antiglyoxime and bromoacetic acid. The pH dependencies and sorption isotherms of various metal ions such as Zn(II), Cd(II), and Al(III) on the resin were investigated from aqueous solution. The sorption behavior of these metal-ligand complexes of sporopollenin derivatives and the possibilities of selectively removing and recovering heavy metals are explained on the basis of their chemical nature and complex properties and the results are interpreted in terms of the variations of pH.     

Formation and characterization of polymersomes made by a solvent injection method

In this article a solvent injection method is described for vesicle formation using poly(butadiene)‐ b‐poly(acrylic acid) diblock copolymers as the amphiphilic molecules. Vesicles composed of polymer bilayers are commonly referred to as polymersomes. Solvent injection is shown to be a rapid method for polymersome formation suitable to make large volumes of polymersome solution. The method can be manipulated to obtain a wide range of vesicle sizes depending on the polymer concentration and preparation conditions. Polymersome solutions in this study are characterized using dynamic light scattering (DLS), fluorescent microscopy, and electron microscopy. Polymersome sizes range from tens of nanometers to several microns. The membrane thickness of smaller polymersomes is found to lie between 14–20 nm. Larger polymersomes are found to have somewhat thicker membranes. The procedure involves the addition of polymers dissolved in an organic solvent to a stirred aqueous solution. The formation of polymersomes by this method is proposed to be governed by the limited mutual solubility of the two solvents and the simultaneous diffusion of solvent and water out of and in to initially formed organic solvent droplets. Copyright © 2007 John Wiley & Sons, Ltd.