Comb-like triblock copolymers by Wurtz-Grignard coupling of syndiotactic PMMA anions to poly[(p-bromomethyl)styrene]-b-polyisobutylene-b-poly[(p-bromomethyl)styrene]

Summary Poly[(p-bromomethyl)styrene]-b-polyisobutylene-b-poly[(p-bromomethyl)styrene]s prepared by sequential monomer addition technique of living cationic polymerization were connected with living syndiotactic (st)-poly(methyl methacrylate) macroanions via Wurtz-Grignard-type coupling. In nonpolar medium (toluene), the coupling resulted in the formation of chemically crosslinked network. In polar solvent (tetrahydrofuran), however, a comb-like triblock copolymer with properties of thermoplastic elastomer was obtained.     

Molecular cloning of the isoamyl alcohol oxidase-encoding gene (mreA) from Aspergillus oryzae

Isoamyl alcohol oxidase (IAAOD) is a novel enzyme that catalyzes the formation of isovaleraldehyde, which is the main component of mureka that gives sake an off-flavor (Yamashita et al. Biosci. Biotechnol. Biochem., 63, 1216–1222, 1999). We cloned the genomic DNA sequence encoding IAAOD from a koji mold, Aspergillus oryzae, using a PCR-amplified DNA fragment corresponding to the partial amino acid sequences of the purified protein as a probe. The cloned gene comprises 1903 bp of an open reading frame with three putative introns and encodes 567 amino acids with a presumed signal peptide consisting of 24 amino acids at the N-terminus. Moreover, nine potential N-glycosylation sites were present. Homology search on amino acid sequence showed that IAAOD has a region significantly similar to those conserved in FAD-dependent oxidoreductases. Southern hybridization analysis revealed that the cloned gene exists as a single copy in the A. oryzae RIB 40 chromosome. The cloned gene was overexpressed under the control of the amyB promoter in A. oryzae. The isovaleraldehyde-producing activity in the culture supernatant of one transformant was over 800 times as high as that of transformant with the control vector. This result demonstrates that the cloned gene encodes IAAOD. We named this novel alcohol oxidase gene “mreA”.     

Mutant influenza viruses with a defective NS1 protein cannot block the activation of PKR in infected cells

A short model genome RNA and also the genome RNA of influenza A virus bearing both 5'- and 3'-terminal common sequences activated the interferon-induced double-stranded-RNA-dependent protein kinase, PKR, by stimulating autophosphorylation in vitro. The activated PKR catalyzed phosphorylation of the alpha subunit of eucaryotic translation initiation factor 2 (eIF2alpha). The NS1 protein efficiently eliminated the PKR-activating activity of these RNAs by binding to them. Two mutant NS1 proteins, each harboring a single amino acid substitution at different regions, exhibited temperature sensitivity in their RNA binding activity in the mutant virus-infected cell lysates as well as when they were prepared as fusion proteins expressed in bacteria. The virus strains carrying these mutant NS1 proteins exhibited temperature sensitivity in virus protein synthesis at the translational level, as reported previously, and could not repress the autophosphorylation of PKR developing during the virus growth, which is normally suppressed by a viral function(s). As a result, the level of eIF2alpha phosphorylation was elevated 2.5- to 3-fold. The defect in virus protein synthesis was well correlated with the level of phosphorylation of PKR and eIF2alpha.     

Synthesis of 1,3-Oxazines and Furo[2,3-b]pyrans by reaction of 2-amino-4,5-dihydro-3-furancarbonitriles with dibenzoyldiazomethanes

2-Amino-4,5-dihydro-3-furancarbonitriles ( 1 ) react with a slight excess of dibenzoyldiazomethane in the presence of rhodium(II) acetate to give 1,3-oxazin-4-ones ( 2 ). With three equivalents of dibenzoyldiazomethane compounds 1 react to afford furo[2,3-b]pyran-3a-carbonitriles ( 3 ). Compound 3a was also obtained by treatment of 2a with two equivalents of dibenzoyldiazomethane.     

On-line GPC/NMR analyses of block and random copolymers of methyl and butyl methacrylates prepared with t-C4H9MgBr

Summary The isotactic block and random copolymers of methyl methacrylate and butyl methacrylate prepared with t-C₄H₉MgBr in toluene, were analyzed by using a 500 MHz ¹H NMR spectrometer as a detector of gel permeation chromatography. The molecular weight dependence of the chemical compositions of these copolymers could be directly determined with this method by monitoring signal intensities of OCH₃ and OCH2 due to methyl methacrylate and butyl methacrylate units, respectively. From the results mechanism of the copolymerizations was discussed in some detail.     

Determining Server Locations in Server Migration Service to Minimize Monetary Penalty of Dynamic Server Migration

In this paper, we propose a new class of service called server migration service (SMS) to augment the existing IaaS (Infrastructure as a Service). SMS allows servers (server-side processes of a network application) to dynamically and automatically migrate as their clients (client-side processes of a network application) change their locations in order to reduce the total monetary penalty that the SMS provider pays to its SMS subscribers when failing to provide them with the guaranteed level of QoS. In this paper, we consider the monetary impact that arises from QoS degradation due to server migration and build an integer programming model to determine when and to which location servers should migrate to minimize the total monetary penalty incurred by the SMS provider. Numerical examples show that SMS achieves up to 96% lower total monetary penalty compared to that without server migration. Numerical examples also show that the integer programming model developed in this paper requires reasonable computation time under realistic parameter settings.     

High-yield synthesis of conductive carbon nanotube tips for multiprobe scanning tunneling microscope

We have established a fabrication process for conductive carbon nanotube (CNT) tips for multiprobe scanning tunneling microscope (STM) with high yield. This was achieved, first, by attaching a CNT at the apex of a supporting W tip by a dielectrophoresis method, second, by reinforcing the adhesion between the CNT and the W tip by electron beam deposition of hydrocarbon and subsequent heating, and finally by wholly coating it with a thin metal layer by pulsed laser deposition. More than 90% of the CNT tips survived after long-distance transportation in air, indicating the practical durability of the CNT tips. The shape of the CNT tip did not change even after making contact with another metal tip more than 100 times repeatedly, which evidenced its mechanical robustness. We exploited the CNT tips for the electronic transport measurement by a four-terminal method in a multiprobe STM, in which the PtIr-coated CNT portion of the tip exhibited diffusive transport with a low resistivity of 1.8 kOmega/microm. The contact resistance at the junction between the CNT and the supporting W tip was estimated to be less than 0.7 kOmega. We confirmed that the PtIr thin layer remained at the CNT-W junction portion after excess current passed through, although the PtIr layer was peeled off on the CNT to aggregate into particles, which was likely due to electromigration or a thermally activated diffusion process. These results indicate that the CNT tips fabricated by our recipe possess high reliability and reproducibility sufficient for multiprobe STM measurements.     

Statistical analysis for the generating mechanism of ground surface roughness

This paper discusses a statistical approach for determining the roughness of a ground surface by considering the dressing characteristics of the grinding wheel.The statistical analyses are derived for the distribution curve of the cutting edges and the probability density function for the occurrence of “peaks” throughout the surface profile of the grinding wheel after dressing treatment and the root mean square roughness of the workpiece surface ground by the wheel. The theory shows that when the grinding wheel is repeatedly dressed by a sharp-pointed dresser, the distribution curve of cutting edges is parabolic. The root mean square of the surface ground by the cutting edges may be calculated from wheel speed, wheel diameter, workpiece speed, the apical angle of the dresser, size sample and the distribution of cutting edges on the circumferential direction of wheel. Good agreement was found between theoretically calculated and experimental results.     

Enzymatic properties of a novel liquefying alpha-amylase from an alkaliphilic Bacillus isolate and entire nucleotide and amino acid sequences

A novel liquefying alpha-amylase (LAMY) was found in cultures of an alkaliphilic Bacillus isolate, KSM-1378. The specific activity of purified LAMY was approximately 5,000 U mg of protein-1, a value two- to fivefold greater between pH 5 and 10 than that of an industrial, thermostable Bacillus licheniformis enzyme. The enzyme had a pH optimum of 8.0 to 8.5 and displayed maximum activity at 55 degreesC. The molecular mass deduced from sodium dodecyl sulfate-polyacrylamide gel electrophoresis was approximately 53 kDa, and the apparent isoelectric point was around pH 9. This enzyme efficiently hydrolyzed various carbohydrates to yield maltotriose, maltopentaose, maltohexaose, and maltose as major end products after completion of the reaction. Maltooligosaccharides in the maltose-to-maltopentaose range were unhydrolyzable by the enzyme. The structural gene for LAMY contained a single open reading frame 1, 548 bp in length, corresponding to 516 amino acids that included a signal peptide of 31 amino acids. The calculated molecular mass of the extracellular mature enzyme was 55,391 Da. LAMY exhibited relatively low amino acid identity to other liquefying amylases, such as the enzymes from B. licheniformis (68.9%), Bacillus amyloliquefaciens (66.7%), and Bacillus stearothermophilus (68.6%). The four conserved regions, designated I, II, III, and IV, and the putative catalytic triad were found in the deduced amino acid sequence of LAMY. Essentially, the sequence of LAMY was consistent with the tertiary structures of reported amylolytic enzymes, which are composed of domains A, B, and C and which include the well-known (alpha/beta)8 barrel motif in domain A.