We studied the effects of regioregularity of the poly(3-hexylthiophene) (P3HT) molecules on the order of molecular arrangement in the P3HT lamellar structure using molecular dynamics simulations. We found that the RR-P3HT molecule shows the aligned molecular arrangement in the ordered lamellar structure, while the RRa-P3HT molecule produces disorders in the π-π interchain stacking due to the formation of disordered network of intermolecular interactions between alkyl side chains of the P3HT molecules. RR-P3HT gains more stabilization energy with respect to the intermolecular interactions than RRa-P3HT due to the formation of ordered lamellar structure in the former system. The order of molecular arrangement in the P3HT lamellar structure is considered to be controlled by the intermolecular interactions between the alkyl side chains.

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Expression of some pathogenesis-related genes in gram-negative bacteria is controlled by bacterial cell-to-cell communication system, quorum sensing (QS), of which signal molecule is N-acylhomoserine lactone (AHL). The AHL concentration-dependent prodigiosin production in Serratia marcescens AS-1 as one of model pathogens could be suppressed by trapping AHLs onto cyclic oligosaccharide cyclodextrins (CDs). Adding CDs could suppress the prodigiosin production because the AHL concentration was kept at a low level below a threshold of the QS activation during the culture. The QS inactivation due to formation of the CD-AHL inclusion complex was demonstrated by bioassay of an AHL-synthase defective mutant, Chromobacterium violaceum CV026, in which purple pigment violacein production could be induced by adding AHLs from outside of cells. A small spot of N-hexanoyl-_L-homoserine lactone (C6HSL) solution onto an agar gel plate containing 20 wt% hydroxypropyl-β-CD and CV026 cells resulted in a meaningful reduction of violacein production after a 10-h incubation at 30℃. A quartz crystal microbalance based on admittance analysis (QCM-A) could determine stability constants between β-CD and C6HSL as (7 ± 2) × 10² M^-1.

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  The X-ray refraction imaging technique was applied to the quantitative study of hydrogen diffusion in titanium-hydride. Hydrogen diffusivity in titanium-hydride was determined by direct observation of the hydride. The hydride was formed on the surface of titanium by electrolytic-charging at 63°C. The specimens were cut into 1-mm thick slices for cross-sectional observations. The hydride layer was observed using the diffraction-enhanced X-ray imaging (DEI) method with asymmetric analyzer. Boundaries between titanium and the hydride were observed as thick black or white lines parallel to the specimen surface in the DEI images similar to previously reported results. Hydride distribution caused by hydrogen diffusion from the surface was converted to the intensity profiles of refraction images of the hydride using the measured rocking curve from an analyzer. The hydrogen diffusivity was calculated from the intensity profiles using the solution of the appropriate diffusion equation. The obtained hydrogen diffusivity in titanium-hydride depended upon the hydrogen concentration. The diffusivity showed good agreement with the widely accepted values in the low hydride concentration region.

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Geranylgeranyl diphosphate (GGPP) synthase catalyzes the condensation of isopentenyl diphosphate with dimethylallyl diphosphate, geranyl diphosphate or farnesyl diphosphate to produce GGPP as the final product. GGPP synthase in the thermophilic bacterium Sulfolobus acidocaldarius can hardly accept substrate analogs possessing oxygen atoms in their prenyl chains. We have prepared several point-mutated S. acidocaldarius GGPP synthases in which phenylalanine was substituted with glycine (F77G) or serine (F77S). Interestingly, the reactivity of the mutated GGPP synthase was enhanced with respect to substrate analogs possessing ω-oxygen atoms in their prenyl chains.

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In this study cell attachment and detachment on the surface was selectively controlled using a photochemical reaction. We prepared a photolabile and cytocompatible polymer surface to control on cell attachment and detachment. As a polymer, poly [(2-methacryloyloxyethyl-phosphorylcholine(MPC)-co-n-butylmethacrylate(BMA)-co-photocleavable-monomer(PL)](PMB-PL) was synthesized. Photocleavable linker with active ester catches suitable for biomacromolecules, therefore cells bind for a culturing on a glass surface. The irradiation with UV light removes the cell adhesive molecules and biofouling surface is remained. Thus, it will be able to detach attached cells with photoirradiation on the surface. The photochemical activity of PMB-PL was examined by absorbance spectra. Features of before and after photoirradiated PMB-PL surface were characterized by Fourier transformed infrared reflection adsorption spectroscopy, X-ray photoelectron spectroscopy, and static contact angle measurement. Also, photo-induced detachment of cells on the surface was examined. As a result, 91% of seeded 4×10⁴ cells were attached onto PMB-PL surface and 67% of attached cells were detached by photochemical reaction. We expect expansion of this tool can be applied for various field, e.g., single cell analysis system, cell and tissue engineering.

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