The spatial distribution of Zn during galvanic corrosion of a Zn/steel couple

The spatial distribution of Zn²⁺ during galvanic corrosion of a model Zn/steel couple in 0.01 M NaCl was investigated using a scanning zinc disk electrode. The couple had a coplanar arrangement of a steel substrate with an electroplated zinc layer at the center. During galvanic corrosion, the marked changes in the Zn²⁺ concentration were confined to a thin solution layer ca. 1.0 mm thick above the couple surface. In this thin solution layer above the zinc layer, a higher concentration region of Zn²⁺ in the range of 5-18 mM extended around the zinc layer in the solution during galvanic corrosion. Conversely, above the steel surface distant from the zinc layer, the surface concentration of Zn²⁺ was almost zero during galvanic corrosion. On this surface, the precipitation of zinc corrosion products due to the hydrolysis reaction of Zn²⁺ was observed. The distribution of the Zn²⁺ concentration supported that Zn²⁺ acted as a buffer that suppressed the increased pH due to the cathodic reaction on the steel surface near the zinc layer and almost no corrosion products formed there. The spatial distribution of Zn²⁺ is discussed in relation to the distributions of potential and pH and the surface morphology of the galvanic couple.     

Ultra-high pressure sterilization of powdery food stuff—a new application of a roller compactor

A new non-heating technique was developed for the sterilization of food stuff. Applying a roller compactor, ultra-high pressure sterilization has experimentally demonstrated its ability to sterilize dry powders, such as corn flour and Chinese herbs, with little quality deterioration. Also, the degree of food sterilization was found correlated well with the linear press forces between the rollers, roller gaps, and number of compaction passes. In comparison to the conventional high pressure sterilization technique, the new dry continuous processing method has the advantage of lower investment cost and is more versatile for sterilizing various food powders.     

Efficient usage of highly dispersed Pt on carbon nanotubes for electrode catalysts of polymer electrolyte fuel cells

A Pt-deposited carbon nanotube (CNT) shows higher performance than a commercial Pt-deposited carbon black (CB) with reducing 60% Pt load per electrode area in polymer electrolyte fuel cells (PEFCs) below 500 mA/cm². K₂PtCl₄ and H₂PtCl₆·6(H₂O) are used for the Pt deposition onto multi-walled CNTs (MWCNTs), which are produced by the catalytic decomposition of hydrocarbons. The electric power densities produced using the Pt/CNT electrodes are greater than that of the Pt/CB by a factor of two to four on the basis of the Pt load per power. CNTs are thus found to be a good support of Pt particles for PEFC electrodes. TEM images show 2–4-nm Pt nanoparticles dispersed on the CNT surfaces. These high performances are considered to be due to the efficient formation of the triple-phase boundaries of gas–electrode–electrolyte. The mechanisms of Pt deposition are discussed for these Pt-deposited CNTs.     

Detection of cytochrome P450 substrates by using a small-molecule droplet array on an NADH-immobilized solid surface

Seeing below the surface: A small-molecule droplet array platform on an NADH-immobilized solid surface and a biotinylated acetophenone derivative were developed to identify the substrate candidates for soluble P450 enzymes of interest. This methodology is thought to be easily applicable to other class I P450 systems, including those that use NADPH as cofactor.     

Thermal and electrical conduction properties of vertically aligned carbon nanotubes produced by water-assisted chemical vapor deposition

We present both thermal and electrical conduction properties of vertically aligned carbon nanotubes (VACNTs), synthesized by the water-assisted chemical vapor deposition method using Fe–Ti–O nanoparticles as catalyst. Thermal diffusivity and electrical resistance of VACNTs have been measured by the laser flash method and direct-current four-terminal method, respectively. The VACNTs are found to have thermal diffusivities of the same order as isotropic graphite and the electrical characteristics of semiconductors. The electrical resistance shows a T^−1/4 temperature dependence, which implies that the conduction of electrons is dominated by 3D Mott variable range hopping.     

Strictly Conserved Residues in Euphorbia tirucalli β‐Amyrin Cyclase: Trp612 Stabilizes Transient Cation through Cation–π Interaction and CH–π Interaction of Tyr736 with Leu734 Confers Robust Local Protein Architecture

The functions of Trp612, Leu734, and Tyr736 of Euphorbia tirucalli β‐amyrin synthase were examined. The aliphatic variants (Ala, Val, Met) of Trp612 showed almost no activity, but the aromatic variants exhibited high activities: 12.5 % of the wild‐type activity for the W612H variant, 43 % for W612F, and 63 % for W612Y. That is, the enzymatic activities of the variants increased in proportion to the increase in π‐electron density. Thus, the major function of Trp612 is to stabilize transient cations through a cation–π interaction. The Phe and Tyr variants caused a distorted folding conformation, especially at the E‐ring site, which generated the aberrantly cyclized products germanicol and lupeol. The L734G and L734A variants exhibited significantly decreased activities but yielded taraxerol in a high production ratio. The Val, Ile, and Met variants showed markedly high activities (56–78 % of wild‐type activity); therefore, appropriate steric bulk is required at this position. The aliphatic variants of Tyr736 showed markedly decreased activities, but the Phe mutant exhibited high activity (67 %), which indicates that the π electrons are critical for catalysis. Homology modeling indicated that Tyr736 and Leu734 are perpendicular to the substrate and are situated face to face, which suggests that a CH–π interaction occurs between Tyr736 and Leu734, reinforcing the protein architecture, and that Tyr736 cannot stabilize cationic intermediates through a cation–π interaction.     

Combinatorial Measurement of CDKN1A/p21 and KIF20A Expression for Discrimination of DNA Damage-Induced Clastogenicity

In vitro mammalian cytogenetic tests detect chromosomal aberrations and are used for testing the genotoxicity of compounds. This study aimed to identify a supportive genomic biomarker could minimize the risk of misjudgments and aid appropriate decision making in genotoxicity testing. Human lymphoblastoid TK6 cells were treated with each of six DNA damage-inducing genotoxins (clastogens) or two genotoxins that do not cause DNA damage. Cells were exposed to each compound for 4 h, and gene expression was comprehensively examined using Affymetrix U133A microarrays. Toxicogenomic analysis revealed characteristic alterations in the expression of genes included in cyclin-dependent kinase inhibitor 1A (CDKN1A/p21)-centered network. The majority of genes included in this network were upregulated on treatment with DNA damage-inducing clastogens. The network, however, also included kinesin family member 20A (KIF20A) downregulated by treatment with all the DNA damage-inducing clastogens. Downregulation of KIF20A expression was successfully confirmed using additional DNA damage-inducing clastogens. Our analysis also demonstrated that nucleic acid constituents falsely downregulated the expression of KIF20A, possibly via p16 activation, independently of the CDKN1A signaling pathway. Our results indicate the potential of KIF20A as a supportive biomarker for clastogenicity judgment and possible mechanisms involved in KIF20A downregulation in DNA damage and non-DNA damage signaling networks.