Effect of Glass Additions on BaO–TiO2–WO3 Microwave Ceramics

The effect of glass addition on the properties of BaO–TiO₂-WO₃ microwave dielectric material N-35, which has Q = 5900 and K = 35 at 7.2 GHz for samples sintered at 1360°C, was investigated. Several glasses including B₂O₃, SiO₂, 5ZnO–2B₂O₃, and nine other commercial glasses were selected for this study. Among these glasses, one with a 5 wt% addition of B₂O₃ to N-35, when sintered at 1200°C, had the best dielectric properties: Q = 8300 and K = 34 at 8.5 GHz. Both Q and K increased with firing temperature as well as with density. The Q of N-35, when sintered with a ZnO–B₂O₃ glass system, showed a sudden drop in the sintering temperature to about 1000°C. The results of XRD, thermal analysis, and scanning electron microscopy indicated that the chemical reaction between the dielectric ceramics and glass had a greater effect on Q than on the density. The effects of the glass content and the mixing process on the densification and microwave dielectric properties are also presented. Ball milling improved the densification and dielectric properties of the N-35 sintered with ZnO–B₂O₃.     

Diffracted X-ray Tracking Method for Measuring Intramolecular Dynamics of Membrane Proteins

Membrane proteins change their conformations in response to chemical and physical stimuli and transmit extracellular signals inside cells. Several approaches have been developed for solving the structures of proteins. However, few techniques can monitor real-time protein dynamics. The diffracted X-ray tracking method (DXT) is an X-ray-based single-molecule technique that monitors the internal motion of biomolecules in an aqueous solution. DXT analyzes trajectories of Laue spots generated from the attached gold nanocrystals with a two-dimensional axis by tilting (θ) and twisting (χ). Furthermore, high-intensity X-rays from synchrotron radiation facilities enable measurements with microsecond-timescale and picometer-spatial-scale intramolecular information. The technique has been applied to various membrane proteins due to its superior spatiotemporal resolution. In this review, we introduce basic principles of DXT, reviewing its recent and extended applications to membrane proteins and living cells, respectively.     

Insertion of a Loop Structure into the “Loopless” GH19 Chitinase from Bryum coronatum

Chitinases belonging to the GH19 family have diverse loop structure arrangements. A GH19 chitinase from rye seeds (RSC-c) has a full set of (six) loop structures that form an extended binding cleft from -4 to +4 (“loopful”), while that from moss (BcChi-A) lacks several loops and forms a shortened binding cleft from -2 to +2 (“loopless”). We herein inserted a loop involved in sugar residue binding at subsites +3 and +4 of RSC-c (Loop-II) into BcChi-A (BcChi-A+L-II), and the thermal stability and enzymatic activity of BcChi-A+L-II were then characterized and compared with those of BcChi-A. The transition temperature of thermal unfolding decreased from 77.2 ˚C (BcChi-A) to 63.3 ˚C (BcChi-A+L-II) by insertion of Loop-II. Enzymatic activities toward the chitin tetramer (GlcNAc)₄ and the polymeric substrate glycol chitin were also suppressed by the Loop-II insertion to 12 and 9 %, respectively. The Loop-II inserted into BcChi-A was found to be markedly flexible and disadvantageous for protein stability and enzymatic activity.     

Investigation of the Interaction of Human Origin Recognition Complex Subunit 1 with G-Quadruplex DNAs of Human c-myc Promoter and Telomere Regions

Origin recognition complex (ORC) binds to replication origins in eukaryotic DNAs and plays an important role in replication. Although yeast ORC is known to sequence-specifically bind to a replication origin, how human ORC recognizes a replication origin remains unknown. Previous genome-wide studies revealed that guanine (G)-rich sequences, potentially forming G-quadruplex (G4) structures, are present in most replication origins in human cells. We previously suggested that the region comprising residues 413–511 of human ORC subunit 1, hORC1^413–511, binds preferentially to G-rich DNAs, which form a G4 structure in the absence of hORC1^413–511. Here, we investigated the interaction of hORC1^413-511 with various G-rich DNAs derived from human c-myc promoter and telomere regions. Fluorescence anisotropy revealed that hORC1^413–511 binds preferentially to DNAs that have G4 structures over ones having double-stranded structures. Importantly, circular dichroism (CD) and nuclear magnetic resonance (NMR) showed that those G-rich DNAs retain the G4 structures even after binding with hORC1^413–511. NMR chemical shift perturbation analyses revealed that the external G-tetrad planes of the G4 structures are the primary binding sites for hORC1^413–511. The present study suggests that human ORC1 may recognize replication origins through the G4 structure.     

Effect of Nitrogen Content on the Microstructure and Mechanical Properties of Ti-Mo-N Coating Films

Effects of nitrogen content on the microstructure, hardness, and friction coefficient of Ti-Mo-N coating films were investigated. Ti-Mo-N films were deposited onto an AISI304 stainless steel substrate by reactive r.f. sputtering in the mixture of argon and nitrogen gases with various gas flow rates. The hardness and friction coefficients were measured by nanoindentation and ball-on-disk testing systems, respectively. The hardness of the Ti-Mo-N films increased with increasing a nitrogen gas flow rate ( f_\textN2 ) \left( {f_{{{\text{N}}_{2} }} } \right) and showed a maximum hardness of about 30 GPa at a f_\textN2 = 0.3 \textccm f_{{{\text{N}}_{2} }} = 0.3\,{\text{ccm}} . On the one hand, the films deposited at f_\textN2 3 1.0  \textccm f_{{{\text{N}}_{2} }} \ge 1.0\;{\text{ccm}} showed a constant hardness value of approximately 25 GPa. On the other hand, the friction coefficient of the Ti-Mo-N film decreased with increasing N content and was 0.44 in the film deposited at f_\textN2 = 2.0  \textccm. f_{{{\text{N}}_{2} }} = 2.0\;{\text{ccm}}.     

Ferroelectric and Photostrictive Properties of Fine-Grained PLZT Ceramics Derived from Mechanical Alloying

Single-phase lead lanthanum zirconate titanate (PLZT) solid solution powder was synthesized from the constituent oxides at ambient temperature through a mechanical alloying (MA) process and was then densified to fine-grained ceramics by sintering and hot-pressing. The anomalous photovoltaic effect (APV) and photoinduced strain of the resultant PLZT ceramics were investigated and analyzed in association with the influence of grain size. It was found that a photoinduced voltage up to 6000 V·cm⁻¹ can be obtained as the grain size is reduced to 0.42 μm. This is extremely high and about three times that achievable in normal micrometer-grained PLZT ceramics. The maximum photoinduced strain of the PLZT ceramics with an average grain diameter of 0.54 μm reached 0.01%, which is equivalent to electric-field-induced strain of common piezoelectric materials.     

Formation and Microstructures of Whipped Oils Composed of Vegetable Oils and High-Melting Fat Crystals

This paper reports the experimental results of processes used for the formation of whipped oils composed of vegetable oils (salad oil) and high‐melting fat crystals [fully hydrogenated rapeseed oil rich in behenic acid (FHR‐B)]. No emulsifier was added to form this whipped oil. Microprobe FT‐IR spectroscopy, synchrotron radiation microbeam X‐ray diffraction (SR‐μ‐XRD), polarized optical microscopy, and differential scanning calorimetry (DSC) were employed to observe fine fat crystal particles of the most stable polymorph of β (β‐fat crystal), FHR‐B, and their adsorption at the air–oil surface before, during, and after the formation of the whipped oil. The results obtained revealed the following: (1) The preparation of an organogel composed of salad oil and small fibrous β‐fat crystals using a special tempering procedure was a prerequisite for forming whipped oil. (2) The β‐fat crystals were adsorbed at the air–oil surface to encapsulate the air bubbles during the formation process of whipped oil. (3) The values of overrun of the whipped oil reached >200 % after an aeration time of 30 min at 20 °C. (4) The SR‐μ‐XRD experiments demonstrated that the lamellar planes of the β‐fat crystals near the air–oil surface were arranged almost parallel to the air–oil surface plane. The present study provides the first evidence that tiny fat crystal particles may cause aeration in liquid oils without the addition of other whip‐assisting substances such as emulsifier crystals.     

Multi‐Enzymatic Synthesis of Optically Pure β‐Hydroxy α‐Amino Acids

A novel enzymatic production system of optically pure β‐hydroxy α‐amino acids was developed. Two enzymes were used for the system: an N‐succinyl L ‐amino acid β‐hydroxylase (SadA) belonging to the iron(II)/α‐ketoglutarate‐dependent dioxygenase superfamily and an N‐succinyl L ‐amino acid desuccinylase (LasA). The genes encoding the two enzymes are part of a gene set responsible for the biosynthesis of peptidyl compounds found in the Burkholderia ambifaria AMMD genome. SadA stereoselectively hydroxylated several N‐succinyl aliphatic L ‐amino acids and produced N‐succinyl β‐hydroxy L ‐amino acids, such as N‐succinyl‐L ‐β‐hydroxyvaline, N‐succinyl‐L ‐threonine, (2S,3R)‐N‐succinyl‐L ‐β‐hydroxyisoleucine, and N‐succinyl‐L ‐threo‐β‐hydroxyleucine. LasA catalyzed the desuccinylation of various N‐succinyl‐L ‐amino acids. Surprisingly, LasA is the first amide bond‐forming enzyme belonging to the amidohydrolase superfamily, and has succinylation activity towards the amino group of L ‐leucine. By combining SadA and LasA in a preparative scale production using N‐succinyl‐L ‐leucine as substrate, 2.3 mmol of L ‐threo‐β‐hydroxyleucine were successfully produced with 93% conversion and over 99% of diastereomeric excess. Consequently, the new production system described in this study has advantages in optical purity and reaction efficiency for application in the mass production of several β‐hydroxy α‐amino acids.

     

Palladium‐Catalyzed Benzylic C?H Benzylation via Bis‐Benzylpalladium(II) Complexes in Water: An Effective Pathway for the Direct Construction of N‐(1,2‐Diphenylethyl)anilines

A strategy for the N‐benzylation/benzylic C H benzylation cascade of anilines by the π‐benzylpalladium system using a water‐soluble palladium(0)/sodium diphenylphosphinobenzene‐3‐sulfonate (TPPMS) catalyst and benzyl alcohol in water has been developed. This tandem process is devised as a novel and efficient synthetic route for N‐(1,2‐diphenylethyl)anilines. Benzylic C H activation of a mono‐N‐benzylated intermediate with a π‐benzylpalladium(II) complex affords a bis‐π‐benzylated palladium(II) intermediate. The nucleophilic η¹‐σ‐benzyl anion ligand attacks the electrophilic η³‐π‐benzyl ligand to give a dibenzylated product. The intermolecular competition between mono‐N‐benzylaniline and its monodeuterated form (monodeuterated at the benzylic group) with benzyl alcohol gave a KIE=4.6, suggesting that C H bond cleavage was involved in the rate‐determining step. Hammett studies on the rate constants of benzylation by various substituted anthranilic acids and mono‐N‐benzylanilines show a good correlation between the log(k_X/k_H) and the σ values of the respective substituents. From the slope, negative ρ values are obtained, suggesting that there is a build‐up of positive charge in the transition state. The reaction of anilines with electron‐donating and electron‐withdrawing groups affords the corresponding N‐(1,2‐diphenylethyl)anilines in moderate to good yields (54–86%). Interestingly, the reaction of anthranilic acids proceeded smoothly to give only the corresponding dibenzylated products in good to excellent yields (70–87%). The carboxyl group of the anthranilic acids acts as a directing group in the benzylic C H activation process.