Synthesis of a novel polymeric carbohydrate via regio‐ and stereoselective cyclopolymerization of 1,2:5,6‐dianhydrohexitol

The selective cyclopolymerization of 1,2:5,6‐dianhydrohexitols corresponding to diepoxides was a new synthetic strategy for polycarbohydrates, though the polymer is a lack of the anomeric linkage which is found in the naturally occurring polysaccharides. 1,2:5,6‐Dianhydro‐3,4‐di‐O‐methyl‐D‐mannitol, L‐iditol, and D‐glucitol were polymerized using t‐BuOK and BF₃·Oet₂ to produce the polymers consisting of five‐membered rings. On the other hand, the polymers consisting of six‐membered rings were obtained by the cationic and anionic polymerizations of meso allitol and galactitol monomers, respectively.     

Characterization of shock accelerometers using davies bar and strain-gages

This paper proposes a novel method for evaluating the dynamic characteristics of shock accelerometers under high acceleration levels and a wide frequency bandwidth. High accelerations of 10³∼10⁵m/s² can be generated by the reflection of an elastic wave pulse propagating in a metal bar known as the Davies bar. The elastic wave pulse is produced by the collision of a projectile against one end of the bar, and is detected by straingages. The accelerometer to be characterized is attached to the other end of the bar. The one-dimensional theory of elastic waves enables the derivation of an input acceleration to the accelerometer from the measured strain. The dispersion of the elastic waves caused by the lateral inertia of the bar is compensated for by using a two-dimensional analytical solution. This method was validated by an experiment characterizing a piezoelectric-type accelerometer within the frequency band approximately 1 kHz∼70 kHz.     

The Action of √−Δ on Weighted Sobolev Spaces

The action of – on distributions is examined within the context of weighted Sobolev spaces. The results obtained are as follows: (1) – is a continuous map of R ⁿ ), the space of rapidly decreasing functions, to L ^{2, s} (R ⁿ for any s < n/2 +1; (2) if k R and s > –n/2 – 1, then – is a continuous map from H ^{k, s} (R ⁿ ), the weighted Sobolev space, to H ^{k–1, t} (R ⁿ for some t. The results are optimal in a sense.     

Electron spin resonance observation of the Si(111)-(7x7) surface and its oxidation process

Electron spin resonance (ESR) observation of dangling-bond states on the Si(111)-(7x7) surface is demonstrated for the first time. The ESR spectra clearly show that a reaction of molecular oxygen with the Si(111)-(7x7) surface is associated with the appearance of a new dangling-bond center at unreacted Si adatoms. Most of the oxidized surface sites do not show ESR signals, but in a minor part of the surface another new type of surface defect is detected. The well known P(b) center at the SiO2/Si interface is found to evolve at an oxide thickness as thin as 0.3 nm.     

Single-walled carbon nanotubes acquire a specific lectin-affinity through supramolecular wrapping with lactose-appended schizophyllan

Single-walled carbon nanotubes can be entrapped within a helical superstructure composed of schizophyllan bearing lactoside-appendages to show an excellent water-solubility as well as a specific lectin-affinity.     

Lactose-appended schizophyllan is a potential candidate as a hepatocyte-targeted antisense carrier

A schizophyllan (beta-1,3-glucan) derivative carrying lactose-appendages prepared by reductive amination can form stable macromolecular complexes with polynucleotides, shows excellent affinity with a lactose-binding lectin, and effectively mediates gene transfection into hepatocytes.     

Control of colloidal interactions between microgels with stimulus-responsive properties

Microgels can switch their chemical/physical properties with external stimulus, and the colloidal behavior of microgels is strongly affected by interparticle interactions. In this article, we introduce smart microgels, focusing on Janus microgels and oscillating microgels developed by our group. Janus microgels show anisotropic shape and chemical/physical properties, and thus the structures of their flocs are also anisotropic. Oscillating microgels show autonomous swelling/deswelling and dispersing/flocculating oscillations through synchronization with chemical reactions. The interparticle interactions of these microgels are discussed. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3021–3026     

Selective Metallation of 3-Halothiophenes: Practical Methods for the Synthesis of 2-Bromo-3-formylthiophene

Selective lithiation of 3-bromothiophene was accomplished under controlled conditions without formation of undesired thienyllithium compounds. A thienyl Grignard reagent derived from 2-bromo-3-iodothiophene was transformed into 2-bromo-3-formylthiophene in high selectivity by formylation with dimethylformamide (DMF) at optimal reaction temperature.     

The p53‐Dependent Expression of Frataxin Controls 5‐Aminolevulinic Acid‐Induced Accumulation of Protoporphyrin IX and Photo‐Damage in Cancerous Cells

Mitochondrial frataxin is involved in various functions such as iron homeostasis, iron–sulfur cluster biogenesis, the protection from oxidative stress and apoptosis and acts as a tumor suppressor protein. We now show that the expression of frataxin is stimulated in a p53‐dependent manner and prove that frataxin is a direct p53 target gene by showing that the p53‐responsive element in the promoter of the mouse frataxin gene is bound by p53. The bacterial expression of human frataxin stimulated maturation of human ferrochelatase, which catalyzes the insertion of iron into protoporphyrin at the last step of heme biosynthesis. Overexpression of frataxin in human cancer A431 and HeLa cells lowered 5‐aminolevulinic acid(ALA)‐induced accumulation of protoporphyrin and induced resistance to ALA‐induced photo‐damage, whereas p53 silencing with siRNA in non tumor HEK293T cells down‐regulated the expression of frataxin and increased the accumulation of protoporphyrin. Thus, the decrease of the expression of frataxin unregulated by p53 in tumor cells enhances ALA‐induced photo‐damage, by down‐regulation of mitochondrial functions.