Formation of supramolecular isomers; poly[2]rotaxane and supramolecular assembly

Poly[2]rotaxane and supramolecular assembly have been prepared by modified cyclodextrins bearing an adamantyl group in an aqueous medium.     

Multielectron-transfer reactions at single Cu(II) centers embedded in polyoxotungstates driven by photo-induced metal-to-metal charge transfer from anchored Ce(III) to framework W(VI)

Using carbon monoxide as a probe molecule for the oxidation state of Cu ions, we demonstrated that anchored polynuclear charge-transfer complexes consisting of Ce(III) ions and Cu(II)-substituted Keggin-type polyoxotungstates function as efficient visible-light-driven multielectron-transfer catalysts.     

Copper(II)/phenanthroline-mediated CD-enhancement and chiral memory effect on a meta-ethynylpyridine oligomer

meta-Ethynylpyridine 18-mer associates with octyl β-D-glucopyranoside to show an induced circular dichroism (CD) band at around 337 nm in CH(2)Cl(2). The addition of copper(II) triflate and o-phenanthroline enhanced the CD band. Even when an equimolar amount of β-L-glucopyranoside was added to make the system racemic, the CD was memorized and remained for several weeks.     

Direct asymmetric synthesis of α-deuterated α-amino acid derivatives from the parent α-amino acids via memory of chirality

A method for asymmeyric α-deuteration of α-amino acid derivatives has been developed by a memory of chirality (MOC) strategy. The α-deuterated α-amino acid derivatives with 88–93% D were obtained in 60–98% ee in retention of the configuration (7 examples). The characterisrtic feature of the present procedure is that asymmeric induction was achieved by employing the parent amino acid derivatives as a sole source of chirality without the use of any external chiral souces.     

Effect of molding parameters on the properties of PP/PP sandwich injection moldings

The basic characteristics of a sandwich injection molded product depend on the properties of the respective resins that comprise the skin and core layers, and the skin/core resin volume ratio. The characteristics of the core layer resin and the skin/core ratio in particular may vary depending on the injection molding conditions. This report considers the influences that the molding conditions such as injection speed, cylinder temperature, and mold temperature confer on the mechanical properties of the sandwich moldings. The study employed, skin/core resin combinations involving similar and dissimilar materials i.e. homopolymer PP/homopolymer PP and homopolymer PP/copolymer PP, respectively. It was demonstrated that core cylinder temperature and mold temperature could be used to adjust the mechanical properties of sandwich injection moldings. In the case of single material sandwich moldings, injection speed seemed to play no significant role, even though it was clearly demonstrated that core volume increases with injection speed. However, core injection speed plays a significant role in the dual material system by lowering or increasing the mechanical strength of moldings as the case may be. Thus, the dormant or active role of injection speed depending on the material system has been highlighted.     

Citric acid oxidation by vanadium(V) in sulfuric acid medium: Kinetic and mechanistic study

The citric acid oxidation by vanadium(V) in sulfuric acid medium at 303 K is reported. The reaction rate was determined spectrophotometrically by monitoring the formation of vanadium(IV) at 760 nm. The oxidation showed a first‐order dependence with respect to vanadium(V) concentration and fractional order with respect to citric acid concentrations, with no control and with constant ionic strength. The reaction is also first order with respect to sulfuric acid concentration with no control and of fractional order at constant ionic strength. The reaction rate is enhanced by an increase of ionic strength and increased by a decrease of the dielectric constant. The activation parameters were calculated based on the rate constants determined in the 293 to 313 K interval. The proposed oxidation mechanisms and the derived rate laws are consistent with the experimental rate laws. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 566–572, 2000     

Chemistry of the Positive and Negative Electrical Discharges Formed in Liquid Water and Above a Gas–Liquid Surface

The physical processes and chemical reactions that take place inside different temperature plasma zones in water are only partially understood. The present study uses the emission spectroscopy and hydrogen peroxide measurements as indicators of the processes that take place on the gas–liquid boundary and inside plasma. Based on the hydrogen peroxide measurements with negative and positive high-voltage polarities as a function of solution conductivity, it was concluded that the main difference between positive polarity plasma and negative polarity plasma lies in the active radical concentration inside plasma. Data suggested that in the positive polarity electrical discharge the hydrogen peroxide concentration depends on the solution pH, whereas in the negative polarity discharge, it depends on the solution conductivity. Also, only in the negative polarity discharge do some of the electrons that are emitted from the high voltage electrode diffuse into the bulk where they react with the solutes.     

General Method for the 11C‐Labeling of 2‐Arylpropionic Acids and Their Esters: Construction of a PET Tracer Library for a Study of Biological Events Involved in COXs Expression

Cyclooxygenase (COX) is a critical enzyme in prostaglandin biosynthesis that modulates a wide range of biological functions, such as pain, fever, and so on. To perform in vivo COX imaging by positron emission tomography (PET), we developed a method to incorporate ¹¹C radionuclide into various 2‐arylpropionic acids that have a common methylated structure, particularly among nonsteroidal anti‐inflammatory drugs (NSAIDs). Thus, we developed a novel ¹¹C‐radiolabeling methodology based on rapid C‐[¹¹C]methylation by the reaction of [¹¹C]CH₃I with enolate intermediates generated from the corresponding esters under basic conditions. One‐pot hydrolysis of the above [¹¹C]methylation products also allows the synthesis of desired ¹¹C‐incorporated acids. We demonstrated the utility of this method in the syntheses of six PET tracers, [¹¹C]Ibuprofen, [¹¹C]Naproxen, [¹¹C]Flurbiprofen, [¹¹C]Fenoprofen, [¹¹C]Ketoprofen, and [¹¹C]Loxoprofen. Notably, we found that their methyl esters were particularly useful as proradiotracers for a study of neuroinflammation. The microPET studies of rats with lipopolysaccharide (LPS)‐induced brain inflammation clearly showed that the radioactivity of PET tracers accumulated in the inflamed region. Among these PET tracers, the specificity of [¹¹C]Ketoprofen methyl ester was demonstrated by a blocking study. Metabolite analysis in the rat brain revealed that the methyl esters were initially taken up in the brain and then underwent hydrolysis to form pharmacologically active forms of the corresponding acids. Thus, we succeeded in general ¹¹C‐labeling of 2‐arylpropionic acids and their methyl esters as PET tracers of NSAIDs to construct a potentially useful PET tracer library for in vivo imaging of inflammation involved in COXs expression.     

Macroscopic Self‐Assembly Based on Complementary Interactions between Nucleobase Pairs

We have created a selective macroscopic self‐assembly process by using polymer gels modified with complementary DNA oligonucleotides or nucleobases. The hydrogels modified with complementary DNA oligonucleotides adhered to each other by simple contact. The organogels modified with complementary nucleobases selectively formed macroscopic assemblies by agitation in nonpolar organic solvents. The adhesion strength of each gel was estimated semi‐quantitatively by stress–strain measurements. We achieved direct adhesion between macroscopic materials both in water and in organic media, based on complementary hydrogen bonds.     

Development of an AND Logic‐Gate‐Type Fluorescent Probe for Ratiometric Imaging of Autolysosome in Cell Autophagy

The concomitant detection of two biological events facilitates the highly selective and sensitive analysis of specific biological functions. In this article, we report an AND logic‐gate‐type fluorescent probe that can concurrently sense two biological events in living cells: H₂O₂ accumulation and acidification. The probe exhibits a unique fluorescence sensing mechanism, in which a xanthene fluorophore is oxidatively transformed to a xanthone derivative by H₂O₂, thereby resulting in a clear dual‐emission change. This transformation is significantly accelerated under weak acidic conditions, which enables the selective and sensitive detection of H₂O₂ production in an acidic cellular compartment. This unique sensing property was successfully applied to the ratiometric fluorescence imaging of autolysosome formation in selective mitochondrial autophagy (mitophagy), which highlights the utility of this novel probe in autophagy research.