Independent self-assembly of cadmium-binding {alpha}-fragment of metallothionein in Escherichia coli without participation of {beta}-fragment

We examined the independent self-assembly of the - and ß-fragmentsof human metallothionein (MT) into cadmiumbinding conformationin an Escherichia coli expression system, in addition to wild-typeMT expression. The expressed -fragment formed independentlythe structure of a metal-binding cluster without the aid ofthe ß-fragment. The -fragment and wild-type MT expressedin E.coli were purified and analyzed for their biochemical andspectroscopic properties. The apparent cadmium binding of the-fragment was approximately 12-fold greater than that for thewild-type MT, whereas in other respects the studied biochemicalproperties were similar. In contrast, we were unable to obtainany independently expressed ß-fragment as the cadmium-bindingform in this study. Possible explanations for this phenomenonare discussed.     

Enhanced compatibility of SAN and PC in their blends exposed to extremely high shear field

Originally incompatible blends of SAN 30% and PC 70% were extruded with extremely high shear rate up to 10⁷ s⁻¹ as a typical example of the blends. The materials were examined with a scanning electron microscope (SEM), a pulsed NMR, etc. The molecular weight of the blends was also measured with gel permeation chromatography. The blends are of binary systems microscopically in the first run of extruding, in which the minor constituent is present as small spherical particles in the major constituent. The apparent volume fraction of the spherical minor constituent estimated from the microscopic photographs decreases with the shear rate. The fraction is decreased also with the repeated runs. SEM observation reveals that dimple fracture of microsize takes place on SAN sphere dispersed in PC matrix. And at the bottom of the dimple, a small particle, which would be composed of PC, is present. From these, SAN in the blend is thought to be partly ductile even at the temperature of liquid nitrogen. At the fifth run, the blend appears uniform or structureless. Dynamic loss tangent gives two peaks corresponding to that of SAN and that possibly attributed to PC. The latter shifts to lower temperatures with the number of extruding run. These show that some of SAN is mixed with PC in a compatible form. The pulsed NMR analysis supports the conclusion. Furthermore, the analysis suggests that some of SAN is mixed in PC. This result shows the compatibility of SAN with PC is enhanced in extremely high shear rate processing.     

Halochromism of acrylic fibres dyed with some disperse dyes

Anomalous dyeing behaviour has been found when regular acrylic fibre treated in hydrochloric acid, in which the sulphonic acid group was present entirely in the acid form, was dyed in neutral condition with azo and anthraquinone disperse dyes. In the very early stages of dyeing there was an abnormally high degree of dye exhaustion, with bathochromic (azo) or hypsochromic (anthraquinone) colour changes on the fibre. These phenomena gradually disappeared after prolonged dyeing, with normal adsorption equilibria and colours eventually being obtained. The results were explained on the basis of protonation by the sulphonic acid groups of treated fibre which occurs at the azo nitrogen or the amino nitrogens of the substituents in the 1 — or 1,4-positions of anthraquinone. The normal adsorption equilibria after prolonged dyeing was attributed to hydrolysis of the cyano side group to form carboxylic acid. This produces ammonia to liberate neutral dye from the protonated dye cation adsorbed electrostatically by the sulphonic acid anion of the treated fibre.     

Feasibility of direct oxygenation of primary-cultured rat hepatocytes using polyethylene glycol-decorated liposome-encapsulated hemoglobin (LEH)

We tested the short-term efficacy of liposome-encapsulated hemoglobin (LEH) in cultured rat hepatocytes. Supplementation with LEH (20% of the hemoglobin concentration of blood) did not lower albumin production in static culture, and completely reversed the cell death and deterioration in albumin production caused by an oxygen shortage in 2D flat-plate perfusion bioreactors.     

Preparation and characterization of magnetically separable photocatalyst (TiO2/SiO2/Fe3O4): effect of carbon coating and calcination temperature

TiO2/SiO2/Fe3O4 composite was synthesized by sol-gel technique for silica and titania coatings on magnetite core to enable recovery after photocatalytic degradation. Carbon coating was also carried out by calcination of TiO2/SiO2/Fe3O4 under nitrogen atmosphere in presence of PVA as a source of carbon to enhance the adsorption of organic compounds on catalyst surface and to get better activity. All prepared samples were characterized using EDX, CN analyzer, XRD, BET and SEM. Degradation of methyl orange dye was used to assess the photocatalytic performance of the prepared samples. Calcination temperature was found to affect rate of reaction because of the formation of rutile phase at high calcination temperature. Carbon coated samples unexpectedly exhibited lower rate of reaction at almost all calcination temperatures.     

Evaluation of molecular orientation and alignment of poly(3-hexylthiophene) on Au (111) and on poly(4-vinylphenol) surfaces

The orientation and alignment of regioregular poly(3-hexylthiophene) (P3HT) molecules on Au (111) surface and on poly(4-vinylphenol) (PVP) thin film were investigated. The P3HT molecules on the smooth Au (111) are oriented with both the backbones and the side chains parallel to the substrate (plane-on orientation) as revealed by the scanning tunneling microscope (STM) images. However, the P3HT molecules on the PVP thin films are preferably oriented with side chains perpendicular to the surface (edge-on orientation). Surface modification of the PVP by hexamethyldisilazane (HMDS) can increase the crystalline size in the P3HT semicrystalline films. The performance of an all-polymer organic field-effect transistor (OFET) with the drop-cast P3HT semiconductor layer and the crosslinked PVP gate insulator on poly(ethylene naphthalate) (PEN) substrate was evaluated.     

Mg-mediated Copolycondensation of α,α-Dibromotoluene with Bifunctional Electrophiles

Copolycondensation of α,α-dibromotoluene (1) with α,α‘-dibromo-p-xylylene (2) was found to proceed in the presence of excess Mg via nucleophilic substitution of in situ generated Grignard reagents to Br-bearing benzylic carbons. The use of dichlorodimethylsilane (3) and 1,6-dibromohexane (4) as a comonomer in the ternary copolycondensation with 1 and 2 was effective to give higher molecular weight polymers by improving their solubility. In the series of the copolycondensation, the copolymer with the highest M _n of 8480 was obtained in a 41% yield by the reaction of a feed ratio of [1]:[2]:[4] = 1:1:1 in THF at room temperature.     

Engineering a chimeric pyrroloquinoline quinone glucose dehydrogenase: improvement of EDTA tolerance, thermal stability and substrate specificity

An engineered Escherichia coli PQQ glucose dehydrogenase (PQQGDH)with improved enzymatic characteristics was constructed by substitutingand combining the gene-encoding protein regions responsiblefor EDTA tolerance, thermal stability and substrate specificity.The protein region responsible for complete EDTA tolerance inAcinetobacter calcoaceticus, which is recognized as the indicatorof high stability in co-factor binding, was elucidated. Theregion is located between 32 and 59% from the N-terminus ofA.calcoaceticus PQQGDH(A27 region) and also corressponds tothe same position from 32 to 59% from the N-terminus in E.coliPQQGDH, though E.coli PQQGDH is EDTA sensitive. We previouslyreported that the C-terminal 3% region of A.calcoaceticus (A3region) played an important role in the increase of thermalstability, and that His775Asn substitution in E.coli PQQGDHresulted in an increase in the substrate specificity of E.coliPQQGDH towards glucose. Based on these findings, chimeric and/ormutated PQQGDHs, E97A3 H775N, E32A27E41 H782N, E32A27E38A3 andE32A27E38A3 H782N were constructed to investigate the compatibilityof two protein regions and one amino acid substitution. His775substitution to Asn corresponded to His782 substitution to Asn(H782N) in chimeric enzymes harbouring the A27 region. Sinceall the chimeric PQQGDHs harbouring the A27 region were EDTAtolerant, the A27 region was found to be compatible with theother region and substituted amino acid responsible for theimprovement of enzymatic properties. The contribution of theA3 region to thermal stability complemented the decrease inthe thermal stability due to the His775 or His782 substitutionto Asn. E32A27E38A3 H782N, which harbours all the above mentionedthree regions, showed improved EDTA tolerance, thermal stabilityand substrate specificity. These results suggested a strategyfor the construction of a semi-artificial enzyme by substitutingand combining the gene-encoding protein regions responsiblefor the improvement of enzyme characteristics. The characteristicsof constructed chimeric PQQGDH are discussed based on the predictedmodel, ß-propeller structure.     

Stabilization of a high-power diode-side-pumpedintracavity-frequency-doubled CW Nd:YAG laser by compensating forthermal lensing of a KTP crystal and Nd:YAG rods

We have analyzed the stability of a high-power diode-side-pumped intracavity-frequency-doubled CW Nd:YAG laser. It is found that large green power fluctuations observed experimentally are suppressed by compensating thermal lensing of the nonlinear crystal KTP and that of the Nd:YAG rods with an advanced resonator design. Stable CW green powers of 27 W with a beam quality of M²=8 and 16 W with M ²=1.2 (TEM₀₀-mode) were generated