Mössbauer spectrometric study of nonstoichiometric perovskite,A (Co0.8Fe0.2) O3−° (A=Ba,Sr, Ca), for oxidative coupling of methane

Nonstoichiometric perovskites. A(Co_0.8Fe_0.2)O₃₋₆, were prepared by a pyrolysis of mixed metal citrates, and the catalytic property and structure of these perovskites were investigated. The efficiency of an oxidative coupling of methane increases with the order of Ba. Sr, and Ca substituted in A site and decreases with the amounts of deficient oxygens. The mixed valence of B site ions in the disordering of deficient oxygen is considered to contribute mainly to the oxidative coupling of methane.     

New class of cationic ring‐opening polymerizations of 2,2‐diphenyl‐1,3‐oxathiolanes accompanying quantitative elimination of benzophenone

Cationic polymerizations of three 2‐substituted 1,3‐oxathiolanes, 2,2‐diphenyl‐1,3‐oxathiolane ( 1a ), 5‐methyl‐2,2‐diphenyl‐1,3‐oxathiolane ( 1b ), and 4‐methyl‐2,2‐diphenyl‐1,3‐oxathiolane ( 1c ), were carried out with boron trifluoride etherate (BF₃ · OEt₂) in dichloromethane at 30 °C to obtain poly(alkylene sulfide)s accompanying the elimination of benzophenone. In the cationic polymerization of 1b and 1c , the consumption of the monomers and formation of benzophenone proceeded simultaneously. The obtained poly(propylene sulfide)s from 1b and 1c contain 41% head–head units, which is in good agreement with that of the polymer from methylthiirane with BF₃ · OEt₂. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2943–2949, 2004     

Isolation, absolute configuration, and chiral crystallization of optically active seleninic acid

An optically pure seleninic acid was isolated as stable crystals for the first time by chiral crystallization. The relationship between the absolute configurations and the circular dichroism spectra of the enantiomers could be determined by X-ray crystallographic analysis.     

Evaluation of the copper(II) complexing ability of ultrafiltered humic acid by the solvent extraction method.

A commercial humic acid dissolved in water was fractionated to nine samples by means of ultrafiltration (UF); the nominal molecular weight used for UF membranes was 1 k-200 kDa. Concerning the nine samples, copper(II) complexing capacities (CuCC) and conditional stability constants (beta) of the formed copper(II) complexes were measured by a solvent extraction method. A total organic carbon (TOC) and the UV-VIS absorption ratio (E350 nm/E450 nm) were also measured. From a comparison of these data, it was found that a) humic acids in each fraction formed two kinds of copper(II) complexes with different stability; b) the beta values obtained from each fraction were almost the same; c) large CuCC values were observed in the molecular weight range from 10 kDa to 20 kDa and below 1 kDa; d) molecules with molecular weight higher than 50 kDa scarcely had any copper(II) complexing ability; e) the values of CuCC/TOC of each fraction were in the range from 1.7 to 3.4 x 10(-7) mol mg(-1).     

Natural product-like macrocyclic N-methyl-peptide inhibitors against a ubiquitin ligase uncovered from a ribosome-expressed de novo library

Naturally occurring peptides often possess macrocyclic and N-methylated backbone. These features grant them structural rigidity, high affinity to targets, proteolytic resistance, and occasionally membrane permeability. Because such peptides are produced by either nonribosomal peptide synthetases or enzymatic posttranslational modifications, it is yet a formidable challenge in degenerating sequence or length and preparing libraries for screening bioactive molecules. Here, we report a new means of synthesizing a de novo library of “natural product-like” macrocyclic N-methyl-peptides using translation machinery under the reprogrammed genetic code, which is coupled with an in vitro display technique, referred to as RaPID (random nonstandard peptides integrated discovery) system. This system allows for rapid selection of strong binders against an arbitrarily chosen therapeutic target. Here, we have demonstrated the selection of anti-E6AP macrocyclic N-methyl-peptides, one of which strongly inhibits polyubiqutination of proteins such as p53.     

Biocompatible, surface functionalized mesoporous titania nanoparticles for intracellular imaging and anticancer drug delivery

Mesoporous titania nanoparticles (MTNs) with excellent biocompatibility (LC(50)≈ 400 μg mL(-1)) and a large surface area (ca. 237.3 m(2) g(-1)) were synthesized and further functionalized with a phosphate-containing fluorescent molecule (i.e. flavin mononucleotide; FMN) and loaded with an anticancer drug (i.e. Doxorubicin) for successful intracellular bioimaging and drug delivery, respectively, in human breast cancer cells BT-20.     

Dramatically improved catalytic activity of an artificial (S)-selective arylmalonate decarboxylase by structure-guided directed evolution

Using three rounds of structure-guided directed evolution, the catalytic activity of the (S)-selective arylmalonate decarboxylase variant G74C/C188S could be increased up to 920-fold. The best variant had a 220-fold improved activity in the production of (S)-naproxen with excellent enantioselectivity (>99% ee).     

Metal-intercalated aromatic hydrocarbons: a new class of carbon-based superconductors

New carbon-based superconductors are synthesized by intercalating metal atoms into the solid-phase hydrocarbons picene and coronene. The highest reported superconducting transition temperature, T(c), of a hydrocarbon superconductor is 18 K for K(3)picene. The physics and chemistry of the hydrocarbon superconductors are extensively described for A(x)picene (A: alkali and alkali earth-metal atoms) for x = 0-5. The theoretical picture of their electronic structure is also reviewed. Future prospects for hydrocarbon superconductors are discussed from the viewpoint of combining electronics with condensed-matter physics: modification of the physical properties of hydrocarbon solids is explored by building them into a field-effect transistor. The features of other carbon-based superconductors are compared to clarify the nature of hydrocarbon superconductors.     

A microfluidic in situ analyzer for ATP quantification in ocean environments

We have developed and tested a functionally integrated in situ analyzer, the IISA-ATP system, for microbial activity assays based on a quantitative determination of the total (particulate and dissolved) ATP in ocean environments. The IISA-ATP utilizes a PDMS-glass hybrid microfluidic device as its core functional element, which can perform cell lysis and total ATP quantification by a luciferin-luciferase bioluminescence assay in situ. Transparent heaters and a temperature sensor fabricated on a glass substrate provide temperature control. As a result of the evaluation using the microfluidic device with ATP standard solutions, the bioluminescence intensity was linearly correlated with 2 × 10(-12) to 2 × 10(-8) M of ATP. A detection limit of 1.1 × 10(-11) M was determined using the completed IISA-ATP system, which includes a miniature pumping module and a control module. As a result of the evaluation using the environmental seawater sample collected from Tokyo Bay, Japan, 2.7 × 10(-10) M of total ATP was successfully determined in the laboratory by the IISA-ATP. The system was operated at a shallow submarine hot spring area in Okinawa, Japan for an in situ trial. The result shows the system was successfully operated in situ and the total ATP was determined to be 3.4 × 10(-10) M.