Analysis of alcohol oxidase isozymes in gene-disrupted strains of methylotrophic yeast Pichia methanolica

A cell-free extract of methanol-grown Pichia methanolica cells was found to contain nine alcohol oxidase (AOD) isozymes by active staining of a native polyacrylamide electrophoresis gel. Our previous study revealed that AOD in P. methanolica was encoded by two genes, MOD1 and MOD2, and the results of an experiment involving Candida boidinii as an expression host suggested that the AOD isozymes observed in P. methanolica were due to random association of Mod1p and Mod2p into an active octamer [Nakagawa et al., Yeast, 15, 1223-1230 (1999)]. This study was conducted using P. methanolica MOD1- and/or MOD2-gene disrupted strains to confirm a previous hypothesis. While the cell-free extract of the wild-type strain gave nine ladder bands, the mod1delta and mod2delta strains gave a single active AOD band corresponding to the mobilities of Mod2p and Mod1p on a native electrophoresis gel, respectively. The cell-free extract of glyceorl-grown wild-type cells gave a single band corresponding to Mod1p, showing that only MOD1 is expressed in glycerol-grown cells. While the expression of both MOD1 and MOD2 was induced by methanol, this finding and our previous observations indicated that the expression of MOD1 and MOD2 was controlled by a distinct regulatory mechanism in P. methanolica.     

Characterization of the Thermo-Viscoelastic Property of Glass and Numerical Simulation of the Press Molding of Glass Lens

A measurement technique for obtaining the thermo-viscoelastic properties of glass with high accuracy is discussed. An unidirectional compression creep test was employed to measure the relaxation modulus of the glass specimens. The creep function derived from the experimental creep test is approximated by a generalized Voigt model, and then converted into a relaxation modulus expressed by a generalized Maxwell model using the Laplace transform and its inversion. Relaxation moduli and shift factors of the glass specimens BK-7 and TaF-3 were estimated according to the presented procedure, and the accuracy of the relaxation modulus was verified by a numerical demonstration using finite element analysis. A fundamental numerical simulation of the press molding of glass lenses was carried out to illustrate the validity of the thermo-viscoelastic properties obtained by the presented approach. Residual stresses under processing conditions were estimated, and the optimal conditions for residual stress minimization are discussed.     

Bactericidal effects of konjac fluid on several food-poisoning bacteria

In this study, the bactericidal effects of Japanese alkaline foods on food-poisoning bacteria were evaluated. Konjac is an alkaline food soaked in calcinated calcium (the pH of konjac fluid ranges from 11.42 to 12.53). Konjac fluids completely inactivated Escherichia coli, enterohemorrhagic E. coli O157:H7 and E. coil O26:H9, Salmonella Enteritidis, Vibrio parahemolyticus. and Staphylococcus aureus. The initial level of 6 log CFU/ml dramatically decreased after incubation with konjac fluid, and no viable gram-negative bacterium cells could be detected within 1 to 2 days and no viable S. aureus cells could be detected within 3 to 5 days. On the other hand, treatment with konjac fluid was also effective in reducing levels of spore-forming bacteria (Bacillus subtilis, Bacillus cereus, Clostridium perfringens, and Clostridium botulinum type E and type A). At least a 4-log reduction of spore-forming bacteria was obtained in konjac fluid within 7 to 14 days. Vegetative cells were more susceptible to konjac fluid than spores were. When the initial cell count was 6 log CFU/ml, a few surviving spores remained for 60 to 90 days, but no spores could be detected after 120 days. When the initial count of spore-forming bacteria was 3 to 4 log CFU/ml, the cells considered vegetative were completely inactivated within I to 3 days. Repeated treatment with konjac fluid caused complete inactivation of spores in less than 1 to 3 days. Our studies indicate that konjac fluid, which has a long history of use in food, will control food-poisoning bacterial contamination during the production or preservation of konjac and other foods and has a preventive effect on bacteria that can cause severe disease at uniquely low levels.     

Pseudomonas aeruginosa as a model microorganism for investigation of chemotactic behaviors in ecosystem

Motile bacteria sense changes in the concentration of chemicals in environments and respond in a behavioral manner. This behavioral response is called chemotaxis. Bacterial chemotaxis can be viewed as an important prelude to metabolism, prey-predator relationships, symbiosis, infections, and other ecological interactions in biological communities. Genome analysis reveals that a large number of environmental motile bacteria possess a number of genes involved in chemosensing and chemotatic signal transduction. Pseudomonas aeruginosa has a very complex chemosensory system with more than 20 chemotaxis (che) genes in five distinct clusters and 26 chemoreceptor (methyl-accepting chemotaxis protein [mcp]) genes. Among the 26 MCPs of P. aeruginosa, nine have been identified as MCPs for amino acids, inorganic phosphate, oxygen, ethylene, and volatile chlorinated aliphatic hydrocarbons, whereas 3 MCPs were demonstrated to be involved in biofilm formation and biosynthesis of type IV pilus. Six che genes are essential for chemotactic responses, while genes in Pil-Chp cluster and Wsp cluster are involved in type IV pilus synthesis and twitching motility and biofilm formation, respectively. P. aeruginosa, with its complex chemotaxis system, is a better model microorganism for investigating ecological aspects of chemotaxis in environmental bacteria than Escherichia coli and Salmonella enterica serovar Typhimurium, which possess a relatively simpler chemotaxis system.     

Evaluation of phosphate removal from water by immobilized phosphate-binding protein PstS

The phosphate (P(i))-binding protein PstS is a member of a family of periplasmic proteins that act as high-affinity receptors for active transport systems in bacteria. PstS protein purified from Pseudomonas aeruginosa was immobilized to N-hydroxysuccinimide-activated Sepharose, packed into a plastic column (5 x 70 mm), and examined for its potential ability to remove P(i) from water. The PstS-Sepharose column completely removed P(i) from 32P-labeled pond water containing about 0.5 microM P(i) (0.015 mg P per liter). More than 90% of 32P-P(i) that was retained in the column could be eluted by washing with low-pH water.     

Influence of alkylpyridine additives in electrolyte solution on the performance of dye-sensitized solar cell

The influence of alkylpyridines additive to an I⁻/I₃⁻ redox electrolyte in acetonitrile on the performance of a bis(tetrabutylammonium)cis-bis(thiocyanato)bis(2,2′-bipyridine-4-carboxylic acid, 4′-carboxylate)ruthenium(II) dye-sensitized TiO₂ solar cell was studied. I–V measurements were performed using more than 30 different alkylpyridines. The alkylpyridine additives showed a significant influence on the performance of the cell. All the additives decreased the short-circuit photocurrent (J_sc), but most of the alkylpyridines increased the open-circuit photovoltage (V_oc) and fill factor (ff) of the solar cell. The results of the molecular orbital calculations suggest that the dipole moment of the alkylpyridine molecules correlate with the J_sc of the cell. These results also suggest that both the size and ionization energy of pyridines correlate with the V_oc of the cell. Under AM 1.5 (100 mW/cm²), the highest solar energy conversion efficiency (η) of 7.6% was achieved by using 2-propylpyridine as an additive, which was more effective than the previously reported additive, 4-t-butylpyridine.     

Lymphatic networks in the periodontal tissue and dental pulp as revealed by histochemical study.

The structural organization and fine distribution of the lymphatic networks in the periodontal tissues (gingiva, periodontal membrane, and alveolar process) and dental pulp of animals and humans were reviewed with special reference to histochemical examination by light and electron microscopy. The distinction between lymphatics and blood vessels was made on cryostat sections of undecalcified and calcified teeth treated with EDTA solution and whole mount preparations of periodontal membranes using 5'-nucleotidase (5'-Nase)-alkaline phosphatase (ALPase) double staining. This staining procedure allowed lymphatic vessels in the periodontal tissue and dental pulp to be differentiated from blood vessels. The specificity and localization of the enzyme reactions were confirmed by comparative histochemical studies of the same specimen with light microscopy and scanning or transmission electron microscopy. Well-developed 5'-Nase-positive lymphatic networks were observed on the tissue sections and whole mount preparations of the gingiva, periodontium, and dental pulp. More lymphatic vessels were seen in the root area of the periodontium than in the cervical area. In the dental pulp, lymphatic vessels were more numerous in the central part than in the peripheral odontoblastic layer. These distributions of the lymphatic capillary networks are discussed in relation to their ability to supply lymph to the teeth.     

A 1.0-V 230-MHz column access embedded DRAM for portable MPEGapplications

This paper describes a 32-Mb embedded DRAM macro fabricated using 0.13-μm triple-well 4-level Cu embedded DRAM technology, which is suitable for portable equipment of MPEG applications. This macro can operate 230-MHz random column access even at 1.0-V power supply condition. The peak power consumption is suppressed to 198 mW in burst operation. The power-down standby mode, which suppresses the leakage current consumption of peripheral circuitry, is also prepared for portable equipment. With the collaboration of array circuit design and the fine Cu metallization technology, macro size of 18.9 mm² and cell efficiency of 51.3% are realized even with dual interface and triple test functions implemented     

Fabrication by Coaxial-Type Vacuum Arc Evaporation Method and Characterization of Bismuth Telluride Thin Films

We prepared both n- and p-type bismuth telluride thin films by using a coaxial-type vacuum arc evaporation method. The atomic compositions of the as-grown thin films and several annealed thin films were comparable to that of bulk bismuth telluride. Their thermoelectric properties were measured and found to be comparable to those of bulk materials. The Seebeck coefficient and electrical conductivity of the as-grown thin films were improved by the annealing process. The measured figures of merit (ZT) of the films were 0.86 for the n-type and 0.41 for the p-type at 300 K for annealing temperatures of 573 K and 523 K, respectively.     

Liquid‐Crystal Composites Composed of Photopolymerized Self‐Assembled Fibers and Aligned Smectic Molecules

A new liquid‐crystal composite, composed of photopolymerizable self‐assembled fibers and a smectic liquid crystal, and its photopolymerized composite have been prepared. The fibers oriented along the smectic layers are obtained by self‐assembly of an amino acid derivative with terminal methacryloyl groups in the smectic liquid crystal. The oriented fibrous structures are fixed by photopolymerization, resulting in the formation of microgrooves on the substrate surfaces. The aligned direction of the liquid‐crystalline molecules is changed to the direction along the fibers after thermal annealing. The patterning of liquid‐crystal alignment is achieved for these liquid‐crystal composites by patterned photopolymerization.