Identification of quorum-sensing signal molecules and the LuxRI homologs in fish pathogen Edwardsiella tarda

Edwardsiella tarda is a gram-negative bacterium that causes septicaemia in fish and serious damage to the aquaculture industry. The virulence factors of this pathogen and control mechanisms of the expression of virulence genes have not yet been clearly elucidated. A number of gram-negative pathogenic bacteria have a quorum-sensing system. These bacteria produce N-acyl-L-homoserine lactone (AHL) that they use them as a quorum-sensing signal molecule. In this study, we found that E. tarda isolated from deceased flounder produces AHLs. Thin layer chromatography analysis indicated that the two kinds of AHL produced by E. tarda seemed to be N-hexanoyl-L-homoserine lactone (C6-HSL) and N-heptanoyl-L-homoserine lactone (C7-HSL). We have cloned and sequenced the quorum-sensing genes, luxI homolog (edwI) and luxR homolog (edwR). EdwI and EdwR showed high identity with CarI/CarR and ExpI/ExpR from Erwinia carotovora, respectively. SDS-PAGE analysis of extracellular proteins revealed that the expression of the 55-kDa protein, which was reported as a virulent-strain-specific protein, is controlled by AHLs. These results suggest that some virulence factors are regulated by the quorum-sensing system in E. tarda.     

Prospective Validation of High-Shear Wet Granulation Process by Wet Granule Sieving Method. I. Selection and Characterization of Sieving Parameters for Wet Granules

To characterize the progression of high-shear wet granulation for various drugs and formulations based on the particle size distribution of wet granules during granulation, a general sieving method for wet granules was investigated. Wet granulation was conducted in a 25-liter high-shear mixer using four model drugs with different solubilities and particle sizes (ethenzamide, unmilled and milled acetaminophen, and antipyrine). Because of its small size and efficient sifting mechanism, a sonic sifter was used to determine the wet granulation particle size distribution. From the good correlation of particle size distribution between wet granules and dry-sized granules, an intensity of 80% of full-scale amplitude and a sieving time of 3 min were selected as wet granule sieving parameters. 7% general sieving method showed good measurement precision as long as the determination was completed within 20 min after sampling, Further, the method was independent of sampling position within the mixer chamber.     

Impact of Polystyrene Oligomer Side Chains on Naphthalene Diimide–Bithiophene Polymers as n‐Type Semiconductors for Organic Field‐Effect Transistors

A series of naphthalene diimide‐based conjugated polymers are prepared with various molar percentage of low molecular weight polystyrene (PS) oligomer of narrow polydispersity as the side chain. The PS side chains are incorporated through preparation of a macromonomer by chain termination of living anionic polymerization. The effects of the PS side chains amount (0–20 mol%) versus overall sidechain on the electrical properties of the resulting polymers as n‐type polymer semiconductors in field‐effect transistors are investigated. We observe that all the studied polymers show similarly high electron mobility (≈0.2 cm² V^?1 s^?1). Importantly, the polymers with high PS side chain content (20 mol%) show a significantly improved device stability under ambient conditions, when compared to the polymers at lower PS content (0–10 mol%). By comparing this observation to the physical blending of the conjugated polymer with PS, we attribute the improved stability to the covalently attached PS side chains potentially serving as a molecular encapsulating layer around the conjugated polymer backbone, rendering it less susceptible to electron traps such as oxygen and water molecules.     

Inducing Elasticity through Oligo‐Siloxane Crosslinks for Intrinsically Stretchable Semiconducting Polymers

The promise of wearable and implantable devices has made stretchable organic semiconductors highly desirable. Though there are increasing attempts to design intrinsically stretchable conjugated polymers, their performance in terms of charge carrier mobility and maximum fracture strain is still lacking behind extrinsic approaches (i.e., buckling, Kirigami interconnects). Here, polymer crosslinking with flexible oligomers is applied as a strategy to reduce the tensile modulus and improve fracture strain, as well as fatigue resistance for a high mobility diketopyrrolopyrrole polymer. These polymers are crosslinked with siloxane oligomers to give stretchable films stable up to a strain ε = 150% and 500 strain‐and‐release cycles of 100% strain without the formation of nanocracks. Organic field‐effect transistors are prepared to assess the electrical properties of the crosslinked film under cyclic strain loading. An initial average mobility (μ^avg) of 0.66 cm² V^?1 s^?1 is measured at 0% strain. A steady μ^avg above 0.40 cm² V^?1 s^?1 is obtained in the direction perpendicular to the strain direction after 500 strain‐and‐release cycles of 20% strain. The μ^avg in the direction parallel to strain, however, is compromised due to the formation of wrinkles.     

Prospective Validation of High-Shear Wet Granulation Process by Wet Granule Sieving Method. II. Utility of Wet Granule Sieving Method

The general utility of a method for determination of high-shear wet granulation end point by monitoring the wet granule particle size distribution was evaluated. Wet granulation was conducted in a 25-liter high-shear mixer using four model drugs with different solubilities and particle sizes (ethenzamide, unmilled and milled acetaminophen, and antipyrine). For each drug formulation, its wet granule particle size fraction and target range for granulation end point determination were selected based on the tablet characteristics that are known to be influenced by the wet granulation process. Granules manufactured under different conditions (i.e., different main and chopper blade speeds and binder supplying rate) but manufactured to the same granulation end point determined by the selected fraction and range showed very similar granule characteristics and subsequently very similar tabler characteristics. From the fact that there was a good correlation between the wet and dry-sized granule particle size distributions even if the drying method was changed from fluid-bed drying to vacuum drying, the general application of the end point determining method was verified. Further, the method was shown to be sensitive to the critical granulation parameters for granulation progression and to be very capable of determining the granulation extent. Thus, it was suggested that the method is applicable to various drugs and formulations for determination of wet granulation end point.     

Selective transalkylation of naphthalene and ethylnaphthalene over solid acid catalysts

A high 2,6-diethylnaphthalene (2,6-DEN) isomer ratio (62%) and a good 2,6-DEN yield (46 mol%) were obtained by the transethylation of 2-ethylnaphthalene with tetraethylbenzenes over H-Y zeolite catalyst. Steric hindrance and electron density at the substitution sites of naphthalene are two influential factors for excellent selectivity. Silica-alumina catalyst, which cannot be expected to possess shape selectivity, also demonstrated a high 2,6-DEN selectivity.     

Generality of anomalous expansion of polymer chains in supercritical fluids

By using in-situ neutron reflectivity, we have investigated swelling isotherms of solvophilic and solvophobic end-grafted/non-grafted polymer chains on solid substrates in supercritical carbon dioxide and supercritical ethane. It was found that anomalous expansion of the polymer chains associated with excess absorption of the fluid molecules occurs in the large compressible regions of both supercritical fluids (SCFs) regardless of the polymer-fluid interactions. In addition, we found that the excess expansion of the solvophobic polymer chains in both SCFs collapse onto one master curve under the same magnitude of density fluctuations in the fluids. A simple thermodynamic two-state model along with the experimental results proposes that polymer chains are expanded independently of the polymer-fluid interactions to further change solvent density fluctuations around the polymer chains, thereby lowering the free energy of the polymer/SCF systems.     

Titanophosphate glasses as lithium-free nonsilicate pH-responsive glasses—Compatibility between pH responsivity and self-cleaning properties

Lithium silicate-based glasses have been widely used as commercially available pH glass electrodes. It was revealed that Ti³⁺-containing titanophosphate (TiO₂–P₂O₅, TP) glasses are pH-responsive as lithium-free nonsilicate glasses for the first time. The absorption coefficient at 532 nm, α₅₃₂ as a measure of Ti³⁺ content in TP glasses increased with increasing melting temperature. TP glasses with large α₅₃₂ tended to give low electrical resistivity, high pH sensitivity and the short pH response time. The first post-annealing (oxidation of Ti³⁺) of TP glasses at 600–620 °C for 60–240 h resulted in the occurrence of the photo-induced hydrophilicity along with the disappearance of pH responsivity and the increase of electrical resistivity. The second post-annealing (reduction of Ti⁴⁺) of the first post-annealed TP glasses at 600–620 °C for 48 h under vacuum recovered both pH responsivity and electrical resistivity to the level of the as-prepared TP glasses with maintaining the photo-induced hydrophilicity. Moreover, the second post-annealed TP glasses had photocatalytic activity for methylene blue (MB) comparable to commercially available self-cleaning glass. Thus, TP glasses with the compatibility between pH responsivity and self-cleaning properties were obtained by the sequential post-annealing (oxidation and reduction) of as-prepared glasses. From some circumstantial evidences, pH response of TP glasses was explained in terms of phase boundary potential model related to hopping conduction of electron from Ti³⁺ to Ti⁴⁺ via O^2? ion in TP glasses rather than diffusion potential model.