An asymmetric S(N)Ar reaction using the molecular chirality in a crystal

An asymmetric S(N)Ar reaction was performed by using molecular chirality generated and amplified by the spontaneous crystallization of achiral naphthamides; the chirality was retained in a cold solution, caused by slow racemization, and was transferred to stable axially chiral materials with high enantiomeric excesses.     

Biosynthesis of violacein: a genuine intermediate, protoviolaceinic acid, produced by VioABDE, and insight into VioC function

A biosynthetic intermediate of violacein produced by the mixed enzymes of VioABDE was elucidated to be 5-(5-hydroxy-1H-indol-3-yl)-3-(1H-indol-3-yl)-1H-pyrrole-2-carboxylic acid, named protoviolaceinic acid, indicating that VioC, responsible for the final biosynthetic step, works to oxygenate at the 2-position of the right side indole ring, and that the oxygenation reaction to form the central pyrrolidone core proceeds in a non-enzymatic fashion.     

Estrogenic and anti-estrogenic activities of Cassia tora phenolic constituents

Through an estrogenic activity bioassay-guided fractionation of the 70% ethanolic extract of Cassia tora seeds two new phenolic triglucosides, torachrysone 8-O-[beta-D-glucopyranosyl(1-->3)-O-beta-D-glucopyranosyl(1-->6)-O-beta-D-glucopyranoside] (1) and toralactone 9-O-[beta-D-glucopyranosyl-(1-->3)-O-beta-D-glucopyranosyl-(1-->6)-O-beta-D-glucopyranoside] (2), along with seven known compounds were isolated. The structures of the new compounds were elucidated on the basis of spectroscopic and chemical evidence. The estrogenic activity of the fractions and the isolated compounds were investigated using the estrogen-dependent proliferation of MCF-7 cells. In addition, the yeast two hybrid assay expressing estrogen receptor alpha (ERalpha) and beta (ERbeta) and the ERalpha competitor screening assay (ligand binding screen) were used to verify the binding affinities of the isolated compounds to ER. Furthermore, a naringinase pre-treatment of the 70% alcoholic extract of Cassia tora seeds resulted in a significant increase in its estrogenic activity. From the naringinase pre-treated extract six compounds were isolated, among which 6-hydroxymusizin and aurantio-obtusin showed the most potent estrogenic activity, while torachrysone, rubrofusarin and toralactone showed a significant anti-estrogenic activity. Finally, the structure requirements responsible for the estrogenic activity of the isolated compounds were studied by investigating the activity of several synthetic compounds and chemically modifying the isolated compounds. The basic nucleus 1,3,8-trihyroxynaphthalene (T(3)HN) was found to play a principal role in the binding affinity of these compounds to ER.     

Revised structures of gambiriins A1, A2, B1, and B2, chalcane-flavan dimers from gambir (Uncaria gambir extract)

Gambir, the aqueous extract from Uncaria gambir (Rubiaceae), has been used as an astringent medicine in Asian countries. Investigation of the constituents in the extract led to the isolation of four chalcane-flavan dimers, gambiriin A1 (6), A2 (7), B1 (8), and B2 (9), in addition to (+)-catechin (1), (+)-epicatechin (2), and dimeric proanthocyanidins, procyanidin B1 (3), procyanidin B3 (4), and gambiriin C (5). The spectroscopic and chemical data obtained in the present study indicated that their previously proposed structures 6a, 7a, 8a, and 9a should be revised to 6, 7, 8, and 9, respectively.     

Cowaniin, a C-glucosidic ellagitannin dimer linked through catechin from Cowania mexicana

A new complex tannin, cowaniin (1) was isolated from the leaves and stems of Cowania mexicana (Rosaceae), and its structure was characterized as novel C-glucosidic tannin dimer linked through (+)-catechin on the basis of spectral and chemical evidence. The inhibitory effect on activation of the Epstein-Barr virus early antigen was assessed for cowaniin. Six known polyphenols and related compounds, including a nitrile glucoside, purshianin, were also characterized.     

Hydroxyapatite nanoparticles as stimulus-responsive particulate emulsifiers and building block for porous materials

Hydroxyapatite (HAp) nanoparticles with spherical, rod-shaped or fiber-shaped morphologies were synthesized by wet chemical method in aqueous media. Scanning electron microscopy, dynamic light scattering, helium pycnometry, and aqueous electrophoresis techniques were used to characterize the nanoparticles in terms of their particle size and morphology, density and zeta potential, respectively. Stable "Pickering-type" emulsions were prepared using the HAp nanoparticles as a particulate emulsifier and methyl myristate as an oil phase above pH 7.7, but not below pH 6.1. These emulsions were characterized in terms of their emulsion type, mean droplet diameter and morphology using electrical conductivity, light diffraction and optical microscopy. Rapid demulsification could be induced by lowering the solution pH: addition of acid led to dissolution of the HAp nanoparticles attached on oil-water interface and the emulsion was destabilized. HAp nanoparticles precipitated by addition of base to the aqueous phase after demulsification and the HAp particles precipitated worked as an effective particulate emulsifier. This emulsification-demulsification cycle was reversible. Sintering of methyl myristate-in-water emulsion stabilized with the HAp nanoparticles led to a porous HAp material.     

Unidirectional crystallization of charged colloidal silica due to the diffusion of a base

Dilute aqueous dispersions of charged colloidal silica (particle volume fraction = approximately 0.03-0.04, particle diameter = 110 nm) exhibit unidirectional crystal growth due to the diffusion of a weak base, pyridine (Py). Similar diffusion-crystallization is enabled by a salt of a weak acid and a strong base, sodium hydrogen carbonate (NaHCO3). The resulting crystals consist of columnar (or cubic) crystal grains with a maximum height of a few centimeters and a maximum width of 1 cm. The crystal growth process is attributed to a combination of (i) the diffusion of Py or NaHCO3 accompanied by a charging reaction of the silica particles and (ii) the charge-induced crystallization of the silica colloids. Theoretical growth curves based on the reaction-diffusion model for the case of Py were in good agreement with the observed curves. We also report the immobilization of the resulting large crystals by using a polymer hydrogel matrix.     

Tuning the effective width of the optical stop band in colloidal photonic crystals

The optical stop band in colloidal crystals is characterized by the central frequency and bandwidth. Although the former is known to be highly tunable by changing the lattice constant, the latter is basically determined by the refractive index contrast between the particles and the background medium that is intrinsic to the materials. In this study, we show that the effective bandwidth in gelled colloidal crystals can also be tuned by controlling the fabrication conditions. Single-domain gelled colloidal crystals were prepared by photopolymerization under various photoirradiation conditions. It was observed that the width of the stop band in the transmission or reflectance spectrum could be expanded by simply adjusting the irradiation time.     

Dynamic processes in endocytic transformation of a raft-exhibiting giant liposome

The dynamic response of a raft-exhibiting giant liposome to external stimuli, such as the addition of Triton X-100 or osmotic stress, was studied. We observed that daughter vesicles are generated inside of the liposome through endocytic budding. It was found that the budding to generate daughter vesicles is classified into two different routes, simple budding through the invagination of a whole raft and budding from the boundary of a raft accompanied by waving motion. Smaller rafts show a preference for simple budding, whereas large rafts mainly adopt the other process. We discuss the mechanism of this difference in terms of the kinetic pathway of internalization by considering the line energy and bending energy of the membrane.     

Fabrication and Patterning of Submierometer-Thick Optical Polarizing Films for 800 nm Using Stretched Silver Island Multilayers

Stretched silver island multilayers have been investigated for patterned optical polarizers for the wavelength of 800 nm. Submicrometer-thick optical polarizing films are fabricated by stretching periodic multilayers consisting of silver island layers and Pyrex layers at the temperature of 660°C. As the optical anisotropy of the optical polarizing film is lost by heating at a temperature higher than the stretching temperature, the fine non-polarizing areas can be deliberately and easily formed on the optical polarizing film by laser irradiation with high power density. We have successfully formed various non-polarizing areas on the optical polarizing film with a 1 W-class carbon dioxide laser. The demonstrated fabricating techniques of deliberately patterned optical polarizing films should be useful for novel optical computing and sensing devices.