Photochemical electron transfer through [corrected] the interface of hybrid films of titania nano-sheets and mono-dispersed spherical mesoporous silica particles

Photochemical Electron Transfer (ET) between an organic dye, the porphyrin derivative TMPyP, and an electron acceptor, methyl viologen MV2+, have been investigated at the interface of two different inorganic films, i.e., layered titania nano-sheets (TNS) and a monolayer film of spherical and mono-dispersed mesoporous silica (sMPS) particles (ca. 0.5 microm). TMPyP ions were intercalated within the sMPS nano-cavities to form (TMPyP-sMPS) while MV2+ ions were intercalated into the TNS interlayers to form (MV2+-TNS). The (TMPyP-sMPS) and (MV2+-TNS) films were then stacked on a silica substrate in this order to form a (MV2+-TNS)/(TMPyP-sMPS) film and, upon UV light irradiation, ET could be induced. However, when this film was stacked inversely, i.e., for the (TMPyP-sMPS)/(MV2+-TNS) films on a silica substrate, no photoinduced ET were observed. Interestingly, however, even for this photo-inactive inversely stacked film, ET could be generated by inserting a gold vapor-deposited layer between the (MV2+-TNS) and (TMPyP-sMPS) films. The conjugation conditions at the interface of the inversely stacked (TMPyP-sMPS)/(MV2+-TNS) hybrid film were, thus, confirmed to strongly affect the photoinduced electron transfers and their efficiencies.     

Physarigins A-C, three new yellow pigments from a cultured myxomycete Physarum rigidum

Physarigins A-C (1-3), three new pigments have been isolated from a cultured plasmodium of myxomycete Physarum rigidum and their structures were elucidated by spectral data.     

Light-driven open-close motion of chiral molecular scissors

The first example of "light-driven chiral molecular scissors" (1), which consists of 1,1',3,3'-tetraarylferrocene as a pivot part and azobenzene as a driving part, was synthesized. Absorption, circular dichroism (CD), and 1H NMR spectral studies on the photoinduced isomerization process of an enantiomer of 1 agreed well with a prediction by a DFT calculation, where a motion of the handles via light-driven contraction/expansion of the connecting azobenzene strap was transformed, through a pivotal motion of the ferrocene unit, into an open-close motion of the blade parts.     

Iridium-catalyzed enantioselective cycloisomerization of nitrogen-bridged 1,6-enynes to 3-azabicylo[4.1.0]heptenes

A cationic iridium complex catalyzes a cycloisomerization of nitrogen-bridged 1,6-enynes to give 3-azabicyclo[4.1.0]heptenes in good to high yield. When an iridium-chiral diphosphine complex is used, the reaction proceeds enantiomerically to give chiral cyclopropanes fused by a six-membered ring system.     

(E)-Selective Horner-Wadsworth-Emmons reaction of aryl alkyl ketones with bis(2,2,2-trifluoroethyl)phosphonoacetic acid

The stereoselective Horner-Wadsworth-Emmons reaction of aryl alkyl ketones with bis(2,2,2-trifluoroethyl)phosphonoacetic acid utilizing lithium hexamethyldisilazide in DMF afforded (E)-α,β-unsaturated carboxylic acids as the major products.     

Analysis of the conserved P9-G10.1 metal-binding motif in hammerhead ribozymes with an extra nucleotide inserted between A9 and G10.1 residues

Hammerhead ribozymes (Rz) have catalytically important tandem G:A pairs in the core region, and we recently demonstrated that the P9-G10.1 motif (a sheared-type G:A pair with a guanine residue on the 3' side of the adenine residue) with several flanking base pairs is sufficient for capture of divalent cations, such as Mg(2+) and Cd(2+) ions that are important to maintain full activities (Tanaka et al. J. Am. Chem. Soc. 2002, 124, 4595-4601; Tanaka et al. J. Am. Chem. Soc. 2004, 126, 744-752). We also found that mutant hammerhead ribozymes that have an additional G residue inserted between A9 and G10.1 residues (the metal-binding P9-G10.1 motif) have significant catalytic activities. In this study, we demonstrate that the hammerhead ribozymes are capable of maintaining the catalytically competent structure even when the tandem, sheared-type G:A pairs were perturbed by an insertion of an additional nucleotide, whereas the chirality of the phosphorothioate at the P9 position significantly influenced the enzymatic activity for both the natural and G-inserted ribozymes.     

Cyano2Dbase updated: linkage of 234 protein spots to corresponding genes through N-terminal microsequencing.

The cyanobacterium Synechocystis sp. strain PCC6803 is an interesting model organism for preoteome study because it is a photosynthetic procaryote and its genomic sequence has already been determined at our institute. We thus initiated characterization of this organism from a proteomic viewpoint by exploiting two-dimensional (2-D) gel electrophoresis coupled with N-terminal protein sequencing. In a previous study, we linked 130 protein spots on two dimensional gels with the genes that encoded them. As an extension of the previous study, the number of protein spots linked to their corresponding genes was increased to 227 in this study by separately analyzing cyanobacterial proteins in four different fractions (soluble, insoluble, thylakoid membrane, and secretory protein fractions). The resultant updated 2-D protein-gene linkage database, named Cyano2Dbase, will serve as an indispensable tool in future cyanobacterial proteomic studies. From the data compiled in the Cyano2Dbase, we can extract many items of information concerning translation, posttranslational processing including characteristics of cyanobacterial signal sequences and modification of cyanobacterial proteins. The Cyano2Dbase is available to the public through the World Wide Web (http://www.kazusa.or.jp/tech/sazuka/cyano/pr oteome.html).     

Evaluation of dispersion state of the two racemic compounds of troglitazone in pharmaceutical granules using IR-to-THz imaging

Troglitazone exists as four isomers in equal amount and these isomers compose two racemic compounds, RR/SS and RS/SR. The objective of this study was to discriminate between the racemic compounds and between the crystal and amorphous forms of troglitazone in solid dispersions (SDs) using IR-to-THz imaging. SDs of troglitazone with polyvinylpyrrolidone (PVP, carrier) were prepared by the closed melting method. SDs were heated at various temperatures and water content. The mid-to-far infrared measurements for the powder samples were performed by using the synchrotron radiation source at the BL43IR in SPring-8. Crystalline RR/SS (L) and RS/SR (H) showed different spectra, that is, each form had a specific peak, respectively. However, amorphous forms prepared from each crystalline form exhibited the same spectra. Using the chemo-metric analysis, the existing component was decided in each pixel and the distribution of crystalline L, H and amorphous troglitazone in SDs could be illustrated. For the sample heated at 105 °C, 75%RH, scattered plots of H and amorphous against PVP showed the trend for H was negative; on the other hand, amorphous showed positive correlation. This result suggested that H existed separately, whereas amorphous would be dissolved in PVP. Based on these evaluations, it was clear that the physical state and distribution of troglitazone in SDs, including the discrimination between L, H, and amorphous, reflect the preparation conditions. Chemical imaging can observe a difference in the dispersed state of drug and ingredient in a visible image by performing statistical processing.     

Thermotropic liquid crystalline polymers containing five-membered heterocyclic groups IX. Synthesis and optical properties of liquid crystalline semi-rigid polyesters composed of a quinquephenyl analogue containing 1,3,4-thiadiazole and aliphatic chains

Novel semi-rigid polyesters containing a quinquephenyl analogue containing 1,3,4-thiadiazole and a central 1,3-phenylene unit in the main chain were synthesized by high temperature solution polycondensation of a dimethyl ester derivative of 1,3-bis(5-phenyl-1,3,4-thiadiazol-2-yl)benzene with an aliphatic (octa-, deca- and dodecamethylene) diol. The proposed structures were confirmed using FTIR and ¹H NMR spectroscopies, and elemental analyses; their liquid crystalline and photoluminescent (PL) properties were examined by means of differential scanning calorimetry, optical texture observations using polarizing microscopy, powder X-ray diffraction, and UV-vis and PL spectra measurements. These measurements showed that the polymers not only show a monotropic solid smectic or disordered crystal phase, but also PL properties with blue emission in HFIP solutions and in the solid phase, Stokes shifts of 116.5-119 nm being observed.     

Epoxy-based electroactive polymer gels

We describe a new type of electroactive polymer gel. In contrast to cross-linked polyacrylates, this system is based on triepoxides cross-linked with polyfunctional amines. The stoichiometry is selected to form a cross-linked gel with excess amino hydrogens. In acid solutions these become cationic and the ionic interactions cause the gel to swell. We describe the mechanical properties of the gels, their response to changes in pH and to electrical activation. The response time is in rough agreement with what would be expected for a diffusional process through a gel of this size (about 100 μm). Samples of smaller dimensions would be expected to respond more rapidly.