Structural Analysis of the Complex between Penta-EF-Hand ALG-2 Protein and Sec31A Peptide Reveals a Novel Target Recognition Mechanism of ALG-2

ALG-2, a 22-kDa penta-EF-hand protein, is involved in cell death, signal transduction, membrane trafficking, etc., by interacting with various proteins in mammalian cells in a Ca²⁺-dependent manner. Most known ALG-2-interacting proteins contain proline-rich regions in which either PPYPXnYP (type 1 motif) or PXPGF (type 2 motif) is commonly found. Previous X-ray crystal structural analysis of the complex between ALG-2 and an ALIX peptide revealed that the peptide binds to the two hydrophobic pockets. In the present study, we resolved the crystal structure of the complex between ALG-2 and a peptide of Sec31A (outer shell component of coat complex II, COPII; containing the type 2 motif) and found that the peptide binds to the third hydrophobic pocket (Pocket 3). While amino acid substitution of Phe⁸⁵, a Pocket 3 residue, with Ala abrogated the interaction with Sec31A, it did not affect the interaction with ALIX. On the other hand, amino acid substitution of Tyr¹⁸⁰, a Pocket 1 residue, with Ala caused loss of binding to ALIX, but maintained binding to Sec31A. We conclude that ALG-2 recognizes two types of motifs at different hydrophobic surfaces. Furthermore, based on the results of serial mutational analysis of the ALG-2-binding sites in Sec31A, the type 2 motif was newly defined.     

Improving the photovoltaic performance of co‐evaporated Cu2ZnSnS4 thin‐film solar cells by incorporation of sodium from NaF layers

We have investigated the influence of sodium (Na) on the properties of co‐evaporated Cu₂ZnSnS₄ (CZTS) layer microstructures and solar cells. The photovoltaic performance and diode properties were improved by incorporating Na from NaF layers into the CZTS layers, while Na had a negligible effect on the microstructural properties of the layer. The best cell fabricated by using an optimal CZTS layer (Cu/(Zn + Sn) = 0.70, Zn/Sn = 1.8) yielded an active area efficiency of 5.23%. The analysis of device properties suggests that charge‐carrier recombination at CZTS/CdS interface is suppressed by intentional Na incorporation from NaF layers. Copyright © 2016 John Wiley & Sons, Ltd.     

α-HYDROXYCARBOXYLIC ACID AS ADDUCT FORMING LIGAND FOR EXTRACTION OF LANTHANIDE(III)

Lanthanide(lII) chelates with 1,1,1 -trif luoro-5,5-dimethyl-2,4-hexanedione form adducts with benzilic acid, an a-hydroxycar-boxylic acid, in chloroform. The order of. the adduct formation constants in magnitude is: La^m> Eu^m> Yb^m although it is known that the stability constant of lanthanide(III) complexes with α-hydroxycarboxylic acids in aqueous solutions increases with increasing atomic number.     

Synthesis of an AlN Polycrystalline Bulk Layer and Nanotubes by Using NH3 and Bi

A bulk layer of aluminum nitride (AlN) polycrystals was synthesized on a boron nitride crucible surface by heating Al chunks with 5 mol% of bismuth at 1273 K for 3 h under NH₃ gas flow. The fragments of the layer were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The platelet grains of AlN with a size of 0.1–1.0 μm and having preferred orientation of the c -axis perpendicular to the layer were formed at the crucible side. Nanotubes 6–15 μm long and about 20–100 nm thick grew on the gas phase side of the layer.     

Preparation of Cu2ZnSnS4 thin films by sulfurizing electroplated precursors

Cu₂ZnSnS₄ (CZTS) thin films were prepared by sulfurizing precursors deposited by electroplating. The precursors (Cu/Sn/Zn stacked layers) were deposited by electroplating sequentially onto Mo-coated glass substrates. Aqueous solutions containing copper sulfate for Cu plating, tin sulfate for Sn plating and zinc sulfate for Zn plating were used as the electrolytes. The precursors were sulfurized by annealing with sulfur at temperatures of 300, 400, 500 and 600 °C in an N₂ gas atmosphere. The X-ray diffraction peaks attributable to CZTS were detected in thin films sulfurized at temperatures above 400 °C. A photovoltaic cell using a CZTS thin film produced by sulfurizing an electroplated Sn-rich precursor at 600 °C exhibited an open-circuit voltage of 262 mV, a short-circuit current of 9.85 mA/cm² and an efficiency of 0.98%.     

CORROSION FATIGUE FRACTURE BEHAVIOUR OF A SiC WHISKERALUMINIUM MATRIX COMPOSITE UNDER COMBINED TENSIONTORSION LOADING

We describe an investigation into the fatigue fracture behaviour under combined tension–torsion loading of a SiC whisker-reinforced A6061 aluminium alloy fabricated by a squeeze casting process. Special attention was paid to the environmental effects on fatigue fracture behaviour. Tests were conducted on both the composite and its unreinforced matrix material, A6061-T6, under load-controlled conditions with a constant value of the combined stress ratio, α = τ_max /σ_max in laboratory air or in a 3.5% NaCl solution at the free corrosion potential. The corrosion fatigue strength of both the matrix and composite was less in the solution than in air. The dominating mechanical factor that determined the fatigue strength in air was either the maximum principal stress or the von Mises-type equivalent stress, depending on the combined stress ratio. However, in the 3.5% NaCl solution, the corrosion fatigue strength of both materials was determined by the maximum principal stress, irrespective of the combined stress ratio. In the case of the matrix material, crack initiation occurred by a brittle facet normal to the principal stress due to hydrogen embrittlement. However, in the composite material, the crack was initiated not at the brittle facet, but at a corrosion pit formed on the specimen surface. At the bottom of the pit, a crack normal to the principal stress was nucleated and propagated, resulting in final failure. Pitting corrosion was nucleated at an early stage of fatigue life, i.e. about 1% of total fatigue life. However, crack initiation at the bottom of a pit was close to the terminal stage, i.e. about 70% or more of total fatigue life. The dominating factor which determined crack initiation at a pit was the Mode I stress intensity factor obtained by assuming the pit to be a sharp crack. Initiation and propagation due to pitting corrosion and crack growth were closely examined, and the fatigue fracture mechanisms and influence of the 3.5% NaCl solution on fatigue strength of the composite and matrix under combined tension–torsion loading were examined in detail.     

Frictional Anisotropy of Oblique Nanocolumn Arrays Grown by Glancing Angle Deposition

Frictional anisotropy of oblique Ti nanocolumns grown by glancing angle deposition (GLAD) was investigated by ramp-scratch experiments in forward (in the direction of the column tilt) and reverse (against the column tilt) directions using rectangular and conical loading tips. Strong anisotropy in friction was generally observed, wherein the resistance or friction coefficient in reverse scratching was higher than that in forward scratching, and the reverse resistance was sensitive to the tip shape. In forward scratching, the nanocolumns bend with the column tilt direction, designated as the W-mode deformation. On the other hand, in reverse scratching, the nanocolumns deflect against the column tilt in high normal force, designated as the A-mode deformation. The deformation mode changes from the W-mode to the A-mode as the normal force increases in reverse scratching. The mechanism of the frictional anisotropy was discussed on the basis of a simple deformation model of column by finite element method. The anisotropy can be explained by the difference in the deformation mode. That is, compressive deformation in the longitudinal direction and large deflection against the column tilt induce higher friction resistance in reverse scratching than in forward scratching brought about by compliant bending deformation with the column tilt.     

Influence of alkylpyridine additives in electrolyte solution on the performance of dye-sensitized solar cell

The influence of alkylpyridines additive to an I⁻/I₃⁻ redox electrolyte in acetonitrile on the performance of a bis(tetrabutylammonium)cis-bis(thiocyanato)bis(2,2′-bipyridine-4-carboxylic acid, 4′-carboxylate)ruthenium(II) dye-sensitized TiO₂ solar cell was studied. I–V measurements were performed using more than 30 different alkylpyridines. The alkylpyridine additives showed a significant influence on the performance of the cell. All the additives decreased the short-circuit photocurrent (J_sc), but most of the alkylpyridines increased the open-circuit photovoltage (V_oc) and fill factor (ff) of the solar cell. The results of the molecular orbital calculations suggest that the dipole moment of the alkylpyridine molecules correlate with the J_sc of the cell. These results also suggest that both the size and ionization energy of pyridines correlate with the V_oc of the cell. Under AM 1.5 (100 mW/cm²), the highest solar energy conversion efficiency (η) of 7.6% was achieved by using 2-propylpyridine as an additive, which was more effective than the previously reported additive, 4-t-butylpyridine.     

Prism-pair interferometry by homodyne interferometers with a common light source for high-accuracy measurement of the absolute refractive index of glasses

A prism-pair interferometer comprising two homodyne interferometers with a common light source was developed for high-precision measurements of the refractive index of optical glasses with an uncertainty of the order of 10(-6). The two interferometers measure changes in the optical path length in the glass sample and in air, respectively. Uncertainties in the absolute wavelength of the common light source are cancelled out by calculating a ratio between the results from the interferometers. Uncertainties in phase measurement are suppressed by a quadrature detection system. The combined standard uncertainty of the developed system is evaluated as 1.1×10(-6).