Conformational change of H+-ATPase beta monomer revealed on segmental isotope labeling NMR spectroscopy

F1-ATPase has been shown to be a stepwise molecular motor. Its rotation mechanism has been explained by the interaction of the gamma axis with the open and closed forms of the beta subunit. Although NMR should be a powerful method for elucidating its mechanism, its molecular size (473 amino acid residues, 52 kDa) is a major obstacle. We have applied segmental labeling based on intein ligation to the beta subunit, and succeeded in assigning 89% of the NH (402/451), 89% of the Calpha (417/473), 83% of the Cbeta (357/431), and 90% of the CO (425/473) signals of the beta subunit monomer. The secondary structures predicted from the chemical shifts of the main chain atoms and the relative orientations determined from residual dipolar couplings indicated that the subunit beta monomer takes on the open form in the absence of nucleotide. Furthermore, the chemical shift perturbation and the residual-dipolar-coupling changes induced by nucleotide binding show that conformational change from the open to the closed form takes place on nucleotide binding. The intrinsic conformational change of the beta subunit monomer induced by nucleotide binding must be one of the essential driving forces for the rotation of F1-ATPase.     

Green Nanocomposites from Renewable Resources: Biodegradable Plant Oil‐Silica Hybrid Coatings

Green nanocomposite coatings based on renewable plant oils have been developed. An acid‐catalyzed curing of epoxidized plant oils with 3‐glycidoxypropyltrimethoxysilane produced transparent nanocomposites. The hardness and mechanical strength improved by incorporating the silica network into the organic polymer matrix, and good flexibility was observed in the nanocomposite. The nanocomposites showed high biodegradability.

     

Understanding magnetic properties of arrays of small FePt dots with perpendicular anisotropy

FePt dot arrays with dot size down to 15 nm are fabricated by film annealing and patterning. The array coercivity shows an increase with dot size decreasing from 100 to 30 nm, and a slight reduction for the 15 nm dot sample. Annealing these dot arrays at higher temperatures results in large enhancements in the coercivities, except the 15 nm dot array where the coercivity increases a little. Micromagnetic models of a 15 nm FePt dot with uniform and nonuniform edges of soft magnetic defects and with inside defects are calculated to reveal the microstructure origins of the dot magnetic properties. It is found that the volume fraction of the L1₀-phase FePt with perpendicular c-axis orientation is about 50% in the dot and the switching field distribution of the dot array can be influenced significantly by the defect arrangement in the dots.     

Microfabrication of FeMnPt films involving magnetic phase change due to structural transformation caused by ion irradiation

Correlations between crystal structures and magnetic properties of Fe_1–xMn_x Pt films were studied. The disordered films with x ≥ 0.44 had paramagnetic properties and the ordered films with x ≥ 0.46 had antiferromagnetic properties, viz. a difference of 0.02 in the x ‐value (i.e., 1.0 at%) was found. At x = 0.44 with the ordered structure, the uniaxial magnetocrystalline anisotropy was about 2.1 × 10⁷ erg cm^–3. A microfabrication process involving the slight composition difference of 0.02, which results in ferromagnetic–paramagnetic phase change due to the structural transformation caused by ion irradiation, was investigated. Only the area irradiated by Mn ions changed from ferromagnetic to paramagnetic phase. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Design and synthesis of a novel class of CK2 inhibitors: application of copper- and gold-catalysed cascade reactions for fused nitrogen heterocycles

Two classes of fused nitrogen heterocycles were designed as CK2 inhibitor candidates on the basis of previous structure-activity relationship (SAR) studies. Various dipyrrolo[3,2-b:2',3'-e]pyridine and benzo[g]indazole derivatives were prepared using transition-metal-catalysed cascade and/or multicomponent reactions. Biological evaluation of these candidates revealed that benzo[g]indazole is a promising scaffold for potent CK2 inhibitors. The inhibitory activities on cell proliferation of these potent CK2 inhibitors are also presented.     

Organic-inorganic hybrids from renewable plant oils and clay

This study deals with the preparation and properties of a new class of organic-inorganic hybrids from renewable resources. The hybrids were synthesized by an acid-catalyzed curing of epoxidized triglycerides in the presence of an organophilic montmorillonite (a modified clay). The mechanical properties were improved by the incorporation of clay in the oil-based polymer matrix. The reinforcement effect due to the addition of clay was confirmed by dynamic viscoelasticity analysis. The hybrids showed relatively high thermal stability. The co-curing of epoxidized soybean and linseed oils in the presence of clay produced hybrids with controlled mechanical and coating properties. The barrier property of the hybrid towards water vapor was superior to that of the oil polymer. The development of the present hybrids consisting of inexpensive renewable resources, triglyceride and clay is expected to contribute to global sustainability.     

Diversity of rice glutelin polypeptides in wild species assessed by the higher-temperature sodium dodecyl sulfate-polyacrylamide gel electrophoresis and subunit-specific antibodies

In efforts to find genetic resources with high nutritional value of rice seed, we assessed the diversity of the major storage protein glutelin in 13 wild and 2 cultivated rice species by a unique SDS-PAGE method and subunit-specific antibodies. Maximum separation of microheterogeneous glutelin alpha-polypeptides, which is a prerequisite for the diversity evaluation, could be attained by SDS-PAGE performed at higher temperature (45 degrees C) than the generally employed temperatures (4-25 degrees C). Seven antipeptide antibodies were raised against subunit-specific epitope sequences designed at five sites from four variable regions spanning the glutelin alpha-polypeptides. High specificity of each antibody was confirmed using rice glutelin mutants, and demonstrated considerable variation in amino acid sequence and accumulation level of glutelin subunit in wild species, in combination with the higher-temperature SDS-PAGE. The degree of the variation was, however, changed according to the site of variable regions and the type of subunit. Some wild species accumulated nutritious GluB subunits more than cultivated rice. The wild species Oryza longiglumis and O. brachyantha had glutelin with low reactivity against most antibodies examined in this study, reflecting the significant divergence. Such wild species may hopefully serve as important genetic resources for nutritional improvement of cultivated rice.     

L10 FePt thin films with [0 0 1] crystalline growth fabricated by SiO2 addition—rapid thermal annealing and dot patterning of the films

FePt films that have a high degree of order S in their L1₀ structure (S>0.90) and well-defined [0 0 1] crystalline growth perpendicular to the film plane were fabricated on thermally oxidized Si substrates by the addition of an oxide and successive rapid thermal annealing (RTA). The mechanism of L1₀ ordering and [0 0 1] crystalline growth perpendicular to the film plane arising through the oxide addition and RTA process is also discussed. The L1₀ ordering (S>0.90) and the [0 0 1] crystalline growth were achieved by (1) lowering the activation energy due to in-plane tensile stress and the initiation of L1₀ ordering at a low temperature, (2) [0 0 1] crystalline growth through in-plane tensile stress, and (3) enhancement of atomic diffusion via the addition of an oxide and the resultant lowering of the ordering temperature. Effect (1) was observed in the case of SiO₂ addition, effect (2) was generally observed in the case of oxide addition and the RTA process, and effect (3) was prominent in the case of ZnO addition. With the addition of ZnO, the L1₀ ordering started at below 400 °C and was completed at 500 °C. Finally, dot patterns were successfully fabricated down to a diameter of 15 nm using electron beam lithography, and the magnetic state of the dot pattern was observed by magnetic force microscopy.     

Broadly tunable subterahertz emission from internal branches of the current-voltage characteristics of superconducting Bi2Sr2CaCu2O(8+δ) single crystals

Continuous, coherent subterahertz radiation arises when a dc voltage is applied across a stack of the many intrinsic Josephson junctions in a Bi2Sr2CaCu2O(8+δ) single crystal. The active junctions produce an equal number of I-V characteristic branches. Each branch radiates at a slightly tunable frequency obeying the Josephson relation. The overall output is broadly tunable and nearly independent of heating effects and internal cavity frequencies. Amplification by a surrounding external cavity to allow for the development of a useful high-power source is proposed.     

Synthesis of high-performance green nanocomposites from renewable natural oils

This paper describes preparation and properties of green nanocomposites from renewable resources. The nanocomposites were synthesized by an acid-catalyzed curing of epoxidized natural oils in the presence of silane coupling agents. The resulting nanocomposites were transparent and highly glossy. Their hardness and Young's modulus of the nanocomposite coatings improved, as compared with those only from the epoxidized natural oils. Dynamic viscoelasticity analysis and TEM observation showed the homogeneous structure of the nanocomposites. The properties of the nanocomposites were strongly affected by the structure and feed ratio of the monomers.