Energy transfer between chlorophyll derivatives in silica mesostructured films and photocurrent generation

Layered silica/surfactant mesostructured thin films containing chlorophyllous pigments [C13(2)-demethoxycarbonyl-pheophytin b (pyroPheo b) or zinc C13(2)-demethoxycarbonyl-chlorophyll b (Zn-pyroChl b)] have been prepared on an indium tin oxide (ITO) electrode grafted with a chlorophyll derivative possessing a triethoxysilyl group (copper C13(2)-demethoxycarbonyl-chlorophyllide a 3-triethoxysilyl propylamide, Cu-APTES-Chl a) to achieve effective light harvesting and successive photocurrent generation by the mesostructured films. The incorporation of pyroPheo b and Zn-pyroChl b in the mesostructured film resulted in 1.2- and 1.6-fold increases of the photocurrent density, respectively, as compared to the case of an antenna pigment-free film also grafted to a surface-modified ITO electrode. The difference action spectra, between the electrodes with and without the antenna pigments, coincided well with the absorption spectra of the immobilized pigments. Because direct electron injection from the antenna pigments in the mesostructured films to the ITO electrode was scarcely observed, the energy transfer from the antenna pigments to Cu-APTES-Chl a plays an important role for the increase in photocurrent density. The usefulness of the mesostructured films as model systems is discussed in relation to the photosynthetic primary processes of higher plants.     

Enzymatic approach to unnatural glycosides with diverse aglycon scaffolds using glycosyltransferase VinC

Glycosyltransferase VinC was explored for a construction of glycoside libraries using dTDP-vicenisamine and structurally unrelated unnatural aglycons, and new unnatural vicenisaminides were successfully constructed. Structural elements of aglycon recognition by VinC were proposed by modeling studies and were confirmed by the success of transglycosylation upon a designed aglycon.     

Current-induced low-resistance state and its crystal structure of a TTF-based dimeric donor salt

A bromide salt of a TTF-based cross-cyclophane-type donor displayed characteristic nonlinear voltage-biased conductivity. As the applied voltage was increased, the passing current was enhanced abruptly at 54 kV.cm-1, exhibiting hysteretic behavior. X-ray analysis of the current-induced low-resistance state of the crystal, which has P41 symmetry, revealed that the degree of charge disproportionation of the dimeric donor in the crystal substantially decreased during the current application. This result is interpreted as indicating that the class I mixed-valence state of the cation-radical salt of the dimeric donor was converted into the class III state by the application of the large current.     

Highly dispersed Ce(III) species on silica and alumina as new photocatalysts for non-oxidative direct methane coupling

Highly dispersed cerium oxide species on silica and alumina, which mainly exist as Ce(III) species, promote non-oxidative direct methane coupling photocatalytically around room temperature, while Ce(IV) species as CeO2 particles do not behave as a catalyst for this reaction.     

Structure-activity relationships (SAR) of [D-Arg(2)]dermorphin(1-4) analogues,N(alpha)-amidino-Tyr-D-Arg-Phe-X

In investigating the development of compounds with potent analgesic effects after oral administration, 74 C-terminal analogues (N(alpha)-amidino-Tyr-D-Arg-Phe-X), based on the structure of N(alpha)-amidino-Tyr-D-Arg-Phe-Me beta Ala-OH (ADAMB), were synthesized. Their analgesic activity was evaluated using the mouse-tail pressure test after both subcutaneous and oral administration, and the structure-activity relationships (SAR) were examined in detail. The results clearly indicated that compounds containing beta-amino acid without a side chain at the X position are preferable for expression of potent analgesic activity, and that the free carboxyl group is superior in its analgesic activity to that of the esterified or amidated carboxy group at the C-terminal. In addition, N-methylation of the amide bond at the 4th position contributed to improved analgesic activity. These results indicated that the strong and long-lasting analgesic effect of ADAMB is expressed by the synergistic effects of N(alpha)-amidination, the N-methylation of the amide bond at the 4th position and the carbon chain length (beta-Ala) of the residue at the 4th position, and that this is the most suitable structure.     

Conformation analysis of carotenoids in the purple bacterium Rhodobium marinum based on NMR spectroscopy and AM1 calculation

Five carotenoids existing in the purple bacterium of Rhodobium marinum, lycopene, anhydrorhodovibrin, spirilloxanthin, rhodopin, and rhodovibrin, were isolated and purified. Their configurations in the chromophore region and conformations of the terminal part were determined by 1D, 2D 1H and 13C NMR spectroscopy. The semiempirical quantum chemical calculation AM1 was subsequently performed using the rough 3-D structures established by NOE correlations as an initial input. The final optimized structures are coincident with 1H-1H NOE correlations and match with the X-ray crystallographic data of carotenoids. The calculation results show that chemically symmetrical carotenoids have a Ci point group. The Ci point group of molecules was destroyed by asymmetrical terminal part although the polyene chain still keeps it roughly. The polyene region of investigated carotenoids are in all-trans with slightly twisted in-plane and slight out-plane forming s-shape carbon backbone due to the spatial interaction of the methyl groups. Terminal parts, on the other hand, have several stable conformers due to the freely rotatable single bonds, but they prefer to take extended conformations.     

Fine structural photoluminescence spectra of silica-supported zirconium oxide and its photoactivity in direct methane conversion

Highly dispersed zirconium oxide species on silica exhibit fine structure in phosphorescence emission spectra showing the vibration energy of the photoactive Zr-O-Si linkage to be 955 cm-1, and the species promotes the photoinduced non-oxidative methane coupling at room temperature.     

Convergent synthesis of the ABCDEF-ring system of yessotoxin and adriatoxin

[formula: see text] The convergent synthesis of the ABCDEF-ring system of yessotoxin and adriatoxin was accomplished. This efficient convergent strategy was performed on the basis of the coupling of the acetylide of the A-ring and the triflate of the DEF-ring, oxidation of the alkyne to diketone, intramolecular diacetalization, and stereoselective reduction of the diacetal with Et3SiH-TMSOTf.     

Total synthesis of batzelladine D

[structure: see text] Stereoselective total synthesis of batzelladine D was accomplished in 15 steps. This synthesis features (i) successive 1,3-dipolar cycloaddition reactions to form the 2,5-disubstituted pyrrolidine ring system, (ii) esterification of the side chain to the bicyclic guanidine carboxylate, a common synthetic intermediate of batzelladine alkaloids, and (iii) tricyclic guanidine formation under the Mitsunobu reaction conditions.     

A novel strategy by the action of ricin that connects phenotype and genotype without loss of the diversity of libraries.

We present a novel strategy for connection of phenotype and genotype in vitro that can be used for the selection of functional proteins even at room temperature. The strategy involves generation of a stable complex between a ribosome, an mRNA, and its translated protein, without removal of the termination codon, as a result of the action of the ricin A chain during translation. We demonstrate the potential selection capacity of this novel strategy by isolating such complexes that contain newly synthesized streptavidin and glutathione-S-transferase (GST) using appropriate ligands. The technique requires no transfection, no chemical synthesis, no ligation, and no removal of the termination codon. Thus our novel "Ribosome-Inactivation Display System (RIDS)" should provide, without loss of the pool population, a reliable, simple, and robust selection system for in vitro evolution of the properties of proteins in a predictable direction by a combination of randomization and appropriate selection strategies.