Imaging of enzyme activity by scanning electrochemical microscope equipped with a feedback control for substrate-probe distance

The enzymatic activity of diaphorase (Dp) immobilized on a solid substrate was characterized using a scanning electrochemical microscope (SECM) with shear force feedback to control the substrate-probe distance. The shear force between the substrate and the probe was monitored with a tuning fork-type quartz crystal and used as the feedback control to set the microelectrode probe close to the substrate surface. The sensitivity and the contrast of the SECM image were improved in the constant distance mode (distance, 50 nm) with the shear force feedback compared to the image in the constant height mode without the feedback. By using this system, the SECM and topographic images of the immobilized diaphorase were simultaneously measured. The microelectrode tip used in this study was ground aslant like a syringe needle in order to obtain the shaper topographic images. This shape was also effective for avoiding the interference during the diffusion of the enzyme substrates.     

The Biological Effects of Forsythia Leaves Containing the Cyclic AMP Phosphodiesterase 4 Inhibitor Phillyrin

Forsythia fruit (Forsythia suspensa Vahl (Oleaceae)) is a common component of Kampo medicines for treating the common cold, influenza, and allergies. The main polyphenolic compounds in the leaves of F. suspensa are pinoresinol β-d-glucoside, phillyrin and forsythiaside, and their levels are higher in the leaves of the plant than in the fruit. It is known that polyphenolic compounds stimulate lipid catabolism in the liver and suppress dyslipidemia, thereby attenuating diet-induced obesity and polyphenolic anti-oxidants might attenuate obesity in animals consuming high-fat diets. Recently, phillyrin was reported as a novel cyclic AMP phosphodiesterase 4 (PDE4) inhibitor derived from forsythia fruit. It was expected that the leaves of F. suspensa might display anti-obesity effects and serve as a health food material. In this review, we summarized our studies on the biological effects of forsythia leaves containing phillyrin and other polyphenolic compounds, particularly against obesity, atopic dermatitis, and influenza A virus infection, and its potential as a phytoestrogen.     

Synthesis, structure and thermal stability of fully hydrophobic porphyrin-DNA conjugates

The DNAs modified with tetraphenyl porphyrin at the center of 13mer oligonucleotide were synthesized using phosphoramidite chemistry and automated DNA synthesis. When the porphyrin modified oligonucleotide was annealed with its complementary strand, they formed a standard B-form duplex. The porphyrin moiety intercalated in the duplex, and moderately lowered the thermal stability.     

Janus particles with a functional gold surface for control of surface plasmon resonance

We report in this study the presence of Janus particles, which are candidates for use with electronic color papers. We used negatively charged polystyrene particles (370 nm) as the core particles, and gold was then sputtered onto their packed monolayer under several conditions. The sputtered particles were next redispersed into the aqueous medium by gentle sonication. Gold nanoparticles localized on one side of the cores could also serve as seeds for subsequent shell growth by electroless gold plating. Through these treatments, a series of well-dispersed Janus particles were obtained with gold nanostructures of different size and shape only on one side. Their dispersions showed different colors originating from the surface plasmon resonance absorption of gold nanoparticles localized on the hemisphere. The particles obtained by this approach have potential applications such as in sensors and electronic color paper.     

Convergent synthesis of the ABCDE ring fragment of ciguatoxins

Synthesis of the ABCDE ring fragment of ciguatoxins has been achieved in a highly stereocontrolled and convergent manner via the B-alkyl Suzuki-Miyaura coupling-based approach.     

Ni-complex-catalysed addition polymerisation of 2-phenyl-1-methylenecylopropane to afford a polymer with cyclopropylidene groups

pi-Allyl-nickel complexes initiated addition polymerisation of 2-phenyl-1-methylenecyclopropane to give a polymer with three-membered rings; the formed polymer showed a high Tg and negligible thermal decomposition up to 300 degrees C.     

Saccharide-branched Cyclodextrins as Targeting Drug Carriers

A synthetic series of heptakis-galactose-branched cyclodextrins (termed CDs) having a longer spacer arm using two amino-caproic acids as an enlarging unit were prepared. Starting with heptakis-amino-β-CD or heptakis-amino-caproic-amide-β-CD, treated with galactosyl-glucono-amide-caproic acid, the new compounds heptakis (Gal-cap1)-CD (4) or heptakis (Gal-cap2)-CD (5) were obtained. The longer galactose spacer arm extremely favors the PNA association. The effect of branch length on K with PNA was enhanced up to 138-fold 3 as well as with DXR enhanced up to 81-fold. Hexakis (Gal-cap2)-CD (6) was prepared and the association constants with rat liver cells were observed to be 2.5 × 10¹⁰ M⁻¹. A multi-high mannose type oligosaccharide branched CD (7) showed a large association constant with DXR up to 1.1 × 10⁹ M⁻¹. The two-dimensional map for the association constants of newly synthesized oligosaccharide-branched CDs toward lectin or liver cells versus the association constants toward a drug (doxorubicin) suggested a method of finding a better targeting drug carrier. The structural effect of the oligosaccharide-CDs showed that the number and length of the branch were dominant factors in designing for enhanced dual recognition.     

Effect of omega-hydrogenation on the adsorption of fluorononanols at the hexane/water interface: pressure effect on the adsorption of fluorononanols

The interfacial tension gamma of the hexane solution of 1H,1H-perfluorononanol (FDFC(9)OH) and its omega-hydrogenated analogue, 1H,1H,9H-perfluorononanol (HDFC(9)OH), against water was measured as a function of pressure and concentration at 298.15 K in order to clarify the effect of omega-dipole on the orientation of fluorononanol molecules from the viewpoint of volume. The adsorbed films of both alcohols exhibit two kinds of phase transitions among three different states: the gaseous, expanded, and condensed states. The partial molar volume changes of adsorption - in the expanded and condensed states were evaluated and compared between the two systems. The - values of both alcohols are negative, and thus the alcohol molecules have smaller volume in the adsorbed film than in the bulk solution. Furthermore, the value was obtained through the evaluation of by the density measurement of the bulk hexane solution. It was found that the value of HDFC(9)OH is smaller than that of FDFC(9)OH in the condensed state. On the basis of three matters concerning the molecular structure of alcohols, the occupied area at the interface, and the orientation of FDFC(9)OH in the adsorbed film deduced from the earlier results of X-ray reflectivity measurement, the mean tilt angle of HDFC(9)OH from the interface normal in the condensed film was estimated to be 15 degrees . The thermodynamic estimation demonstrated here is highly valuable one to provide structure information on an adsorbed film.     

Unprecedented double nucleophilic addition of a hydride at a central carbon of an eta3-allyl ligand

Treatment of eta(3)-allyl compound [Cp(2)Mo(eta(3)-C(3)H(5))](+)(1; Cp =eta(5)-C(5)H(5)) with MH (M = Li, Na) resulted in reduction of the allyl ligand to give propane. Deuterium-labeling studies were used to trace the origins and fates of the hydrogen atoms. The mechanism is discussed in light of the HSAB principle. The studies showed that the formation of propane can be explained by 1,2-hydrogen migration from the central to the terminal carbon of the allyl ligand, and the subsequent double nucleophilic addition of the hydride at the central carbon.