Polymerization of Acrylonitrile Initiated by the System Tetramethyl-2-tetrazene and p-Toluenesulfonic Acid

The polymerization of acrylonitrile (AN) initiated by tetramethyl-2-tetrazene (TMT) and p-toluenesulfonic acid (TSA) in dimethylformamide (DMF) was studied. The polymerization was confirmed to proceed through a radical mechanism. The initial rate of polymerization R was expressed by the equation: R_p = k[TMT]^0.6 [TSA]^0.46 [AN]^1.35. The overall activation energy for the polymerization was estimated as 20.7 kcal/mole. In the absence of monomer, the reaction of TMT with TSA was also studied kinetically by measuring the evolution of nitrogen. From these results and ESR measurement of the TMT/TSA system, a possible initiation mechanism is proposed.     

Hydrochlorothiazide Enhances UVA‐Induced DNA Damage

The UVA is currently thought to be carcinogenic because, similar to UVB, it induces the formation of cyclobutane pyrimidine dimers (CPDs). Various drugs have been reported to cause photosensitive drug eruptions as an adverse effect. Although the precise mechanism of photosensitive drug eruption remains to be elucidated, it is generally accepted that free radicals and other reactive molecules generated via UV‐irradiated drugs play important roles in the pathogenesis of photosensitive drug eruptions. The waveband of concern for photo‐reactive drugs is UVA‐visible light, but some extend into the UVB region. We tested whether photosensitive drugs could enhance CPD formation after UVA exposure by using isolated DNA in the presence of several reported photosensitive drugs using high‐performance liquid chromatography. We found that the diuretic agent hydrochlorothiazide (HCT) significantly enhanced the production of TT dimers over a wide range of UVA. Furthermore, we investigated whether UVA plus HCT could enhance CPD production in xeroderma pigmentosum model mice defective in nucleotide excision repair. Immunofluorescence studies showed that CPD formation in the skin significantly increased after 365 nm narrow‐band UVA irradiation in the presence of HCT, compared with that in wild‐type mice. HCT could be used with caution because of its enhancement of UVA‐induced DNA damage.     

Photoinduced alignment of polymer liquid crystals containing azobenzene moieties in the side group VII. On He-Ne laser beam irradiation

Photoinduced alignment in a polymer liquid crystal prepared from 6-{1-[4-(2-cyano-4-nitrophenylazo)phenyl]piperazino}hexyl acrylate and 4'-[6-(methacryloyloxy)hexyloxy]-4-cyanobiphenyl was investigated for the first time on irradiation with a polarized He-Ne laser beam at 633 nm. The azobenzene moieties as well as the inert cyanobiphenyl mesogenic units were aligned with the molecular long axis perpendicular to the polarization direction of the irradiation light. Alignment induced on short irradiation was reversible, while that induced under prolonged irradiation was irreversible due to the occurrence of crosslinking which might be caused by photoinduced decomposition of the azobenzene moieties during the photoirradiation process.     

Electro-optic effect,propagation loss,and switching speed in polymers containing nano-sized droplets of liquid crystal

Polymers containing droplets of liquid crystal smaller than 100 nm, which have good transparency and easily form films, were prepared under various conditions to evaluate their potential as electro-optic materials for waveguide-type devices. By varying the liquid crystal concentration and the strength of the UV irradiation causing photo-induced phase separation of the droplets, we were able to control the droplet size and density. We have clarified how the birefringence generated in an applied electric field, switching speed, and optical loss of light propagating in the film depend on droplet size and density. Polymer materials having a large electro-optic effect (δn = 0.001 at 8 V μm^-1), low propagation loss (~2.5 dB cm^-1), and fast response time (~10 μs) have been developed.     

The Bioactive Peptide SL-13R Expands Human Umbilical Cord Blood Hematopoietic Stem and Progenitor Cells In Vitro

Hematopoietic stem and progenitor cell (HSPC) transplantation is a curative treatment of hematological disorders that has been utilized for several decades. Although umbilical cord blood (UCB) is a promising source of HSPCs, the low dose of HSPCs in these preparations limits their use, prompting need for ex vivo HSPC expansion. To establish a more efficient method to expand UCB HSPCs, we developed the bioactive peptide named SL-13R and cultured UCB HSPCs (CD34+ cells) with SL-13R in animal component-free medium containing a cytokine cocktail. Following 9 days of culture with SL-13R, the numbers of total cells, CD34+, CD38− cells, and hematopoietic stem cell (HSC)-enriched cells were significantly increased relative to control. Transplantation of cells cultured with SL-13R into immunodeficient NOD/Shi-scid/IL-2Rγ knockout mice confirmed that they possess long-term reconstitution and self-renewal ability. AHNAK, ANXA2, and PLEC all interact with SL-13R. Knockdown of these genes in UCB CD34+ cells resulted in reduced numbers of hematopoietic colonies relative to SL-13R-treated and non-knockdown controls. In summary, we have identified a novel bioactive peptide SL-13R promoting expansion of UCB CD34+ cells with long-term reconstitution and self-renewal ability, suggesting its clinical use in the future.     

Development of variable‐magnification X‐ray Bragg optics

A novel X‐ray Bragg optics is proposed for variable‐magnification of an X‐ray beam. This X‐ray Bragg optics is composed of two magnifiers in a crossed arrangement, and the magnification factor, M, is controlled through the azimuth angle of each magnifier. The basic properties of the X‐ray optics such as the magnification factor, image transformation matrix and intrinsic acceptance angle are described based on the dynamical theory of X‐ray diffraction. The feasibility of the variable‐magnification X‐ray Bragg optics was verified at the vertical‐wiggler beamline BL‐14B of the Photon Factory. For X‐ray Bragg magnifiers, Si(220) crystals with an asymmetric angle of 14° were used. The magnification factor was calculated to be tunable between 0.1 and 10.0 at a wavelength of 0.112 nm. At various magnification factors (M≥ 1.0), X‐ray images of a nylon mesh were observed with an air‐cooled X‐ray CCD camera. Image deformation caused by the optics could be corrected by using a 2 × 2 transformation matrix and bilinear interpolation method. Not only absorption‐contrast but also edge‐contrast due to Fresnel diffraction was observed in the magnified images.     

Total synthesis of (S)-(+)-ent-phomapyrones B and surugapyrone B

Phomapyrone B ( 1 ), the 2-pyrones isolated from the phytopathogenic fungus Leptosphaeria maculans, has been synthesized as the enantiomeric form starting from (S)-2-methylbutanol ( 4 ). Surugapyrone B ( 3 ) isolated from Streptmyces sp. USF-6280 as an antioxidant has also been synthesized as a natural form. The absolute configuration of phomapyrone B ( 1 ) was estimated to be the (R)-form and that of surugapyrone B ( 3 ) being the (S)-form. A series of 2-pyrone derivatives 17 have been synthesized through the established procedure and their DPPH radical-scavenging activities have also been evaluated.     

Spatiotemporal Dynamics of Aggregation-Induced Emission Enhancement Controlled by Optical Manipulation

We present spatiotemporal control of aggregation-induced emission enhancement (AIEE) of a protonated tetraphenylethene derivative by optical manipulation. A single submicrometer-sized aggregate is initially confined by laser irradiation when its fluorescence is hardly detectable. The continuous irradiation of the formed aggregate leads to sudden and rapid growth, resulting in bright yellow fluorescence emission. The fluorescence intensity at the peak wavelength of 540 nm is tremendously enhanced with growth, meaning that AIEE is activated by optical manipulation. Amazingly, the switching on/off of the activation of AIEE is arbitrarily controlled by alternating the laser power. This result means that optical manipulation increases the local concentration, which overcomes the electrostatic repulsion between the protonated molecules, namely, optical manipulation changes the aggregate structure. The dynamics and mechanism in AIEE controlled by optical manipulation will be discussed from the viewpoint of molecular conformation and association depending on the laser power.