Functionalized Bilayer Membranes as Artificial Transaminase: Modification of the Active Site and Its Consequence in Catalytic Efficiency

The transamination reaction of l-phenylalanine with pyruvate as catalyzed by the artificial transaminase formed with synthetic bilayer aggregates was examined in aqueous media under mild kinetic conditions. Each catalyst system was constructed with a combination of a synthetic peptide lipid, a hydrophobic vitamin B₆ derivative, and metal ions. Modification of the active site in the present artificial transaminase was performed by changing a combination of molecular components constituting the catalytic system. While the catalytic activity was scarcely influenced by differences in aggregate structure, single- or multi-walled bilayer, and in copper-(II) concentration, molecular structures of the hydrophobic vitamin B₆ and an amino acid residue of the peptide lipid had significant effects on the reactivity.     

Potential of predominant activated sludge bacteria as recipients in conjugative plasmid transfer

We investigated the possibility of conjugative plasmid transfer to the predominant bacteria in activated sludge and the factors influencing the transfer frequency in the activated sludge process. We performed conjugative transfers of a self-transmissible, broad-host-range plasmid RP4 from Escherichia coli C600 to activated sludge bacteria by broth mating. Most of the activated sludge bacteria tested could acquire plasmid RP4, although the transfer frequencies varied from 8.8 x 10(-7) to 1.3 x 10(-2) transconjugants per recipient. The transfer frequencies in several strains were similar to, or higher than, that in intraspecific transfer to E. coli HB101. Matings under various environmental conditions showed that factors relevant to physiological activity, such as temperature and nutrient conditions, seemed to affect the transfer frequency. In addition, conjugative transfer was detected even in filtered raw and treated wastewaters. Thus, the predominant activated sludge bacteria seem to have sufficient potential as recipients in conjugative plasmid transfer under the conditions likely to occur in the activated sludge process. Transfer frequency was reduced by agitation in the presence of suspended solid. This may suggest that conjugative plasmid transfer is physically inhibited in aeration tanks.     

Development of anchored oligothiophenes on substrates for the application to the tunable transparent conductive films

Bis(triethoxysilyl)-substituted oligothiophene with a moderate π-conjugation length was newly synthesized and polymerized to give a polysilsesquioxane network having oligothiophene units dispersed homogeneously without phase separation. The polymer was fixed on glass or ITO substrate by spin-coating and annealing. The resulting film exhibited a high mechanical strength due to the covalent bonding with the substrates, and was electrochemically stable even after 300 redox cycles in electrolyte solution. Chemical oxidation of the polymer films yielded electrically conductive and almost transparent films.     

Enrichment of bacteria possessing catechol dioxygenase genes in the rhizosphere of Spirodela polyrrhiza: A mechanism of accelerated biodegradation of phenol

The bacterial community structure in bulk water and in rhizosphere fractions of giant duckweed, Spirodela polyrrhiza, was quantitatively and qualitatively investigated by PCR-based methods using 6 environmental water samples to elucidate the mechanisms underlying selective accumulation of aromatic compound-degrading bacteria in the rhizosphere of S. polyrrhiza. S. polyrrhiza selectively accumulated a diverse range of aromatic compound-degrading bacteria in its rhizosphere, regardless of the origin of water samples, despite no exposure to phenol. The relative abundances of the catechol 1,2-dioxygenase (C12O) gene (C12O DNA) and catechol 2,3-dioxygenase (C23O) gene (C23O DNA) were calculated as the ratios of the copy numbers of these genes to the copy number of 16S rDNA and are referred to as the rhizosphere effect (RE) value. The RE values for C12O DNA and C23O DNA were 1.0 × 10¹–9.3 × 10³ and 1.7 × 10²–1.5 × 10⁴ times as high, respectively, in rhizosphere fractions as in bulk water fractions, and these higher values were associated with a notably higher sequence diversity of C12O DNA and C23O DNA. The RE values during phenol degradation were 3.6 × 10⁰–4.3 × 10² and 2.2 × 10⁰–1.7 × 10², respectively, indicating the ability of S. polyrrhiza to selectively accumulate aromatic compound-degrading bacteria in its rhizosphere during phenol degradation. The bacterial communities in the rhizosphere fractions differed from those in the bulk water fractions, and those in the bulk water fractions were notably affected by the rhizosphere bacterial communities. S. polyrrhiza released more than 100 types of phenolic compound into its rhizosphere as root exudates at the considerably high specific release rate of 1520 mg TOC and 214 mg phenolic compounds/d/g root (wet weight). This ability of S. polyrrhiza might result in the selective recruitment and accumulation of a diverse range of bacteria harboring genes encoding C12O and C23O, and the subsequent accelerated degradation of phenol in the rhizosphere.     

Effect of long term ingestion of gum arabic on the adipose tissues of female mice

Abdominal obesity is the most prevalent manifestation of metabolic syndrome. The anti-obese effects of dietary fiber is generally accepted, but specifically the anti-obese properties of the dietary fiber, gum arabic (GA) has not been well studied. In this investigation, we offered GA to the female 90 days old mice in the form of drink (1% w/v) for 180 days. Such GA in drinking water reduced age-dependent fat deposition in the visceral adipose tissue and improved the gastrocnemius muscle reduction. This inhibition of fat deposition effect is due to the β3-adrenergic stimulation of adipocytes in which TNFα down-regulation is probably involved. Modification of large intestinal microflora, as evidenced by a modification of cecal short-chain fatty acid profile and of 16S rDNA profile, may contribute to such reduction in TNFα expression in the adipose tissues.     

Nanofabrication of cylindrical STEM specimen of InGaAs/GaAs quantum dots for 3D-STEM observation

We demonstrate the multiazimuth observation (360 degrees in principle) of InGaAs/GaAs quantum dots (QDs) by means of a 300 kV scanning transmission electron microscope (STEM), where both cross-sectional and plan-view observations are performed on a single STEM specimen for the first time. A cylindrical specimen with a diameter of 200-300 nm including the QD layer inside along the rotation axis was fabricated by the focused ion beam (FIB) technique, with the application of a newly developed mesa-cutting method to adjust the position and angle of the QD layer precisely. The 360 degrees STEM observation is realized by mounting the cylindrical specimen on a holder equipped with a specimen-rotation mechanism. High potential of 3D-STEM observation is briefly presented by showing high contrast images of QDs, dark field images, and moire fringes with various incident angles.     

Dietary conjugated linolenic acid in relation to CLA differently modifies body fat mass and serum and liver lipid levels in rats

The present study compared the effect of dietary conjugated linolenic acid (CLNA) on body fat and serum and liver lipid levels with that of CLA in rats. FFA rich in linoleic acid, α-linolenic acid, CLA, or CLNA were used as experimental fats. Male Sprague-Dawley rats (4 wk old) were fed purified diets containing 1% of one of these experimental fats. After 4 wk of feeding, adipose tissue weights, serum and liver lipid concentrations, serum tumor necrosis factor (TNF)-α and leptin levels, and hepatic β-oxidation activities were measured. Compared with linoleic acid, CLA and, more potently, CLNA were found to reduce perirenal adipose tissue weight. The same trend was observed in the weight of epididymal adipose tissue. CLNA, but not CLA, was found to significantly increase serum and liver IG concentrations. Serum FFA concentration was also increased in the CLNA group more than in the other groups. The activity of β-oxidation in liver mitochondria and peroxisomes was significantly higher in the CLNA group than in the other groups. Thus, the amount of liver TG exceeded the ability of hepatic β-oxidation. Significant positive correlation was found between the adipose tissue weights and serum leptin levels in all animals (vs. perirenal: r=0.557, P<0.001; vs. epididymal: r=0.405, P<0.05). A less significant correlation was found between adipose tissue weights and serum TNF-α level (vs. perirenal: r=0.069, P<0.1; vs. epididymal: r=0.382, P<0.05). Although the mechanism for the specific effect of CLNA is not clear at present, these findings indicate that in rats CLNA modulated the body fat and TG metabolism differently from CLA.     

Dinitrogen as a probe of acid sites of zeolites

Nitrogen adsorption on H-ZSM-5 and H-Y zeolites at low temperatures were studied by in situ FT-IR spectroscopy. For each zeolite, two absorption bands were observed at around 2334 and 2352 cm^–1 in thev(NN) region and were assigned to thev(NN) mode of dinitrogen species adsorbed on Brønsted and Lewis acid sites of the zeolites, respectively. These results and previous results for H-mordenite suggest that dinitrogen serves as a probe of acid sites and its advantages as probe are discussed.     

Monitoring behaviour of catabolic genes and change of microbial community structures in seawater microcosms during aromatic compound degradation

The behaviour of microbial populations responsible for degradation of the aromatic compounds, phenol, benzoate, and salicylate, and changes of microbial community structures in seawater microcosms were analysed quantitatively and qualitatively using MPN–PCR and PCR–DGGE. The purpose of the study was to investigate the ecology of the entire microbial community during bioremediation. Bacterial populations possessing catechol 1,2-dioxygenase (C12O) DNA were evidently the primary degraders of phenol and benzoate, but others possessing catechol 2,3-dioxygenase (C23O) DNA increased to enhance substrate degradation under high-load conditions when the substrates were present for long periods. However, salicylate degradation was evidently facilitated by specific bacterial populations possessing C23O DNA. PCR–DGGE analyses suggested that bacterial populations already relatively dominant in the original microcosm contributed to phenol degradation. Bacteria composing a minor fraction of the original population apparently increased and contributed to benzoate degradation. Bacterial populations possessing C23O DNA were responsible for salicylate degradation, however, and different degrading bacteria were evidently selected for, depending on the initial salicylate concentration. Microbial community structure tended to be simplified by aromatic compound degradation. Thus, microbial monitoring can elucidate the behaviour of bacterial populations responsible for aromatic compound degradation and be used to assess the effects of bioremediation on intact microbial ecosystems.