A Metal-Free,Disulfide Oxidized Form of Superoxide Dismutase 1 as a Primary Misfolded Species with Prion-Like Properties in the Extracellular Environments Surrounding Motor Neuron-Like Cells

Superoxide dismutase 1 (SOD1) is a metalloenzyme with high structural stability, but a lack of Cu and Zn ions decreases its stability and enhances the likelihood of misfolding, which is a pathological hallmark of amyotrophic lateral sclerosis (ALS). A growing body of evidence has demonstrated that misfolded SOD1 has prion-like properties such as transmissibility between cells and intracellular propagation of misfolding of natively folded SOD1. Recently, we found that SOD1 is misfolded in the cerebrospinal fluid of sporadic ALS patients, providing a route by which misfolded SOD1 spreads via the extracellular environment of the central nervous system. Unlike intracellular misfolded SOD1, it is unknown which extracellular misfolded species is most relevant to prion-like properties. Here, we determined a conformational feature of extracellular misfolded SOD1 that is linked to prion-like properties. Using culture media from motor neuron-like cells, NSC-34, extracellular misfolded wild-type, and four ALS-causing SOD1 mutants were characterized as a metal-free, disulfide oxidized form of SOD1 (apo-SOD1^S-S). Extracellular misfolded apo-SOD1^S-S exhibited cell-to-cell transmission from the culture medium to recipient cells as well as intracellular propagation of SOD1 misfolding in recipient cells. Furthermore, culture medium containing misfolded apo-SOD1^S-S exerted cytotoxicity to motor neuron-like cells, which was blocked by removal of misfolded apo-SOD1^S-S from the medium. We conclude that misfolded apo-SOD1^S-S is a primary extracellular species that is linked to prion-like properties.     

Bottom-up synthesis of oxygen-containing carbon materials using a Lewis acid catalyst

Oxygen-containing carbon materials have been studied extensively because of their excellent dispersibility, absorptivity, separability, and supportability of catalysts. However, structural control by existing top-down methods is almost impossible. Our group has demonstrated that phloroglucinol (PG, 1,3,5-trihydroxybenzene) can be a promising raw material to synthesize structurally controlled oxygen-containing carbon materials. In this study, in addition to PG, hexahydroxybenzene (HHB), which has more oxygen and high symmetry, was used as the raw material, and a Lewis acid catalyst, tris (pentafluorophenyl) borane (TPB), was used to enhance the structural control rate and the removability of catalysts from the carbonized samples. The solubility of heat-treated HHB was lower than that of heat-treated PG, but the oxygen content of heat-treated HHB was higher than that of heat-treated PG even at 673 K. By adding TPB to PG, dibenzofuran-like structures formed, and the structural control rate increased up to 93.6%. Besides, the content of fluorine in the catalyst was reduced to 0%, indicating that TPB can be a promising recyclable catalyst to promote the structural control rate of carbonized PG.

Graphical abstract

     

Effect of TiO2 on morphology and mechanical properties of PVDF/PMMA blend films prepared by melt casting process

Effect of titanium dioxide (TiO₂) on morphology and mechanical properties of poly(vinylidene fluoride) (PVDF)/poly(methyl methacrylate) (PMMA) blend films prepared at different TiO₂ contents by a melt casting process was studied. The results showed that tensile moduli in both the machine direction (MD) and the transverse direction (TD) increased with increasing TiO₂ content, and calculated tensile moduli based on the Halpin–Tsai and the Kerner model were consistent with experimental ones in both the MD and TD of films containing 10 wt % TiO₂. However, experimental tensile moduli exhibited smaller values compared with calculated ones, as the TiO₂ content increased to 30 wt %_, and it was assumed that this is due to the decrease of crystallinity of PVDF. Morphological observations indicated that TiO₂ particles did not affect crystal structures of PVDF and the morphology of PVDF/PMMA amorphous phase, but hindered the crystallization of PVDF. The MD and TD elongation at break exhibited >200 and <20%, respectively. The SEM micrographs revealed that spherulites could deform along the MD when the tensile force was applied along the direction. By contrast, spherulites could not deform along the TD and fractured at very small elongation, owing to the anisotropic morphology of spherulites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40454.     

Identification and Characterization of D‐Succinylase,and a Proposed Enzymatic Method for D‐Amino Acid Synthesis

Chiral amino acids are important intermediates for the pharmaceutical industry. We have developed a novel one‐pot enzymatic method for D ‐amino acid synthesis by the dynamic kinetic resolution of N‐succinyl‐dl ‐amino acids using D ‐succinylase (DSA) and N‐succinylamino acid racemase (NSAR, EC 4.2.1.113). The DSA from Cupriavidus sp. P4‐10‐C, which hydrolyzes N‐succinyl‐D ‐amino acids enantioselectively to their corresponding D ‐amino acids, was identified for the first time by screening soil microorganisms. Subsequently, the DSA gene was cloned and overexpressed in Escherichia coli. DSA was shown to comprise two subunits with molecular masses of 26 kDa and 60 kDa. Additionally, the NSAR gene from Geobacillus stearothermphilus NCA1503, which racemizes N‐succinylamino acids, was also cloned and overexpressed in E. coli. The highly purified DSA and NSAR prepared from each recombinant E. coli were characterized and used for D ‐amino acid synthesis. A one‐pot enzymatic method converted 100 mM N‐succinyl‐dl ‐phenylalanine to D ‐phenylalanine in 91.1% conversion with 86.7% ee. This novel enzymatic method may be useful for the industrial production of many D ‐amino acids.

     

A study on physical and mechanical properties for soft to firm clays in Yangon area – Properties of clays deposit at the sedimentary basins in Myanmar

Recently, a great deal of foreign investment has been entered into construction of the social infrastructure of Myanmar. Many construction projects are therefore on-going, and these are especially planned in the Yangon area. While these construction booms are increasing, existing studies on the geotechnical problems in the Yangon area such as problematic soils like soft clays are limited at present. Information on soil properties has also not been shared and has been confined to individual projects. In this paper, the boring and laboratory tests carried out in the Yangon area are selected and focused upon among the tests carried out in Myanmar. Laboratory test results for clay deposits in the Yangon area are analyzed and the differences in soil properties between different sedimentary basins and sub-areas divided by the Tertiary sediment ridge that runs from north to south at the center of Yangon are clarified together with a comparison to the clays found in other countries, which have been previously investigated.     

Investigation of hydrogen plasma treatment for reducing defects in silicon quantum dot superlattice structure with amorphous silicon carbide matrix

We investigate the effects of hydrogen plasma treatment (HPT) on the properties of silicon quantum dot superlattice films. Hydrogen introduced in the films efficiently passivates silicon and carbon dangling bonds at a treatment temperature of approximately 400°C. The total dangling bond density decreases from 1.1 × 10¹⁹ cm^-3 to 3.7 × 10¹⁷ cm^-3, which is comparable to the defect density of typical hydrogenated amorphous silicon carbide films. A damaged layer is found to form on the surface by HPT; this layer can be easily removed by reactive ion etching.     

Silicon quantum dot superlattice solar cell structure including silicon nanocrystals in a photogeneration layer

The solar cell structure of n-type poly-silicon/5-nm-diameter silicon nanocrystals embedded in an amorphous silicon oxycarbide matrix (30 layers)/p-type hydrogenated amorphous silicon/Al electrode was fabricated on a quartz substrate. An open-circuit voltage and a fill factor of 518 mV and 0.51 in the solar cell were obtained, respectively. The absorption edge of the solar cell was 1.49 eV, which corresponds to the optical bandgap of the silicon nanocrystal materials, suggesting that it is possible to fabricate the solar cells with silicon nanocrystal materials, whose bandgaps are wider than that of crystalline silicon.

PACS

85.35.Be; 84.60.Jt; 78.67.Bf     

Changes in dietary bioaccumulation of tributyltin chloride (TBTCl) in red sea bream (Pagrus major) with the concentration in feed

The effect of the concentration of tributyltin (TBT) in feed on the dietary bioaccumulation of tributyltin chloride (TBTCl) was studied in an 8-week uptake experiment and a 4-week elimination experiment using red sea bream (Pagrus major). The biomagnification factor (BMF) and the assimilation efficiency (AE) decreased from 0.30 to 0.15 and from 13% to 5.9%, respectively, as the TBT concentration in feed increased from 1.3 to 20 microg/g. The elimination rate constant (k(2)) was independent of the TBT concentration in the fish. Laboratory measurements of the BMF and AE of TBTCl underestimate actual field values if highly contaminated feed is used. Judging from the BMF and AE, the risk of the bioaccumulation of TBTCl through the food chain might be smaller than that of polychlorinated biphenyls.