Effect of Fiber-Polymer Interactions on Fracture Toughness Behavior of Carbon Fiber-Reinforced Epoxy Matrix Composites

The effect of anodic oxidation on high-strength polyacrylonitrile-based carbon fibers has been studied in terms of fiber surface energetics and fracture toughness of the composites. According to contact angle measurements based on the wicking rate of a test liquid, anodic oxidation leads to an increase in surface free energy, mainly due to the increase of its specific (or polar) component. For the carbon-fiber-reinforced epoxy resin matrix system, a direct linear relationship is shown between the specific component and the critical stress intensity factor measured by the single edge notched beam fracture toughness test. From a surface-energetic point of view, the anodic treatment may be suitable for carbon fibers incorporated in a polar organic matrix, resulting in an increased specific component of the surface free energy. Good wetting plays an important role in improving the degree of adhesion at interfaces between fibers and matrices of the resulting composites. Copyright 2000 Academic Press.     

Inhibitory effects of 1,3-selenazol-4-one derivatives on mushroom tyrosinase

This study reports depigmenting potency of 1,3-selenazol-4-one derivatives, which would be based upon the finding of direct inhibition to mushroom tyrosinase. 1,3-Selenazol-4-one derivatives exhibited inhibitory effect on dopa oxidase activity of mushroom tyrosinase. In this study, inhibitory effects of six kinds of 1,3-selenazol-4-one derivatives (A, B, C, D, E and F) on mushroom tyrosinase were investigated. Compounds at a concentration of 500 microM exhibited 33.4-62.1% of inhibition on dopa oxidase activity of mushroom tyrosinase. Their inhibitory effects were higher than that of kojic acid (31.7%), a well known tyrosinase inhibitor. 2-(4-Methylphenyl)-1,3-selenazol-4-one (A) exhibited the strongest inhibitory effect among them dose-dependently and in competitive inhibition manner.     

A novel way to study the initial stages of soap-free emulsion polymerizations: The intercalation of polystyrene oligomers into hydrotalcite

The dominant species in the early stages of an emulsifier-free emulsion polymerization of styrene has been found to be an oligomer of two to three monomer units using a novel trapping technique. This involved the intercalation of charged primary oligomers between the layers of a hydrotalcite, [Mg₄Al₂(OH)₁₂]²⁺[A]^2- (where A = dianion). Hydrotalcites are an important class of lamellar, inorganic compounds whose interlayer spacing can be mod-ified by anion exchange. Our approach first involved preparing a hydrotalcite precursor in which the layers were propped apart by an organic dianion (terephthalate = TA). This material was then used to capture the negatively charged polystyrene oligomers from the emulsion polymerization reaction mixture. We found that TA was rapidly ion-exchanged for the charged oligomers. The resulting pillared hydrotalcite material was characterized using XRD and SEC. We found that the interlayer spacing between the hydroxide layers increased to 23.2 Å on exposure to the emulsion reaction mixture. This represents an interlayer expansion of 18.3 Å (after subtraction of the hydroxide layer contribution), which is cnsistent with intercalation of oligomers with two to three monomer units arranged in a bilayer. This size estimate was confirmed by the results of size exclusion chromatography. © 1995 John Wiley & Sons, Inc.     

Alcohol sensing membrane based on immobilized ruthenium(II) complex in carboxylated PVC and surface covalently bonded alcohol oxidase

Alcohol sensing membranes coated on overhead transparency films for the continuous monitoring of ethanol, propanol and butanol are presented. Alcohol oxidation catalyzed by alcohol oxidase in conjunction with the fluorescence quenching reaction of oxygen-sensitive dye ion-pair, tris(4,7-diphenyl-1,10-phenanthroline) ruthenium(II) didodecylsulphate was chosen for the determination. Alcohol oxidase was immobilized covalently on a plasticized carboxylated poly(vinyl chloride) membrane and the oxygen-sensitive dye ion-pair was entrapped in the same membrane. The sensing membrane relates oxygen consumption, as a result of enzymatic oxidation, to alcohol concentration. Measurements have been performed in air-saturated alcohol standard solutions of pH 7.0. Storage stability, reproducibility and the effect of pH on sensing membrane performance have been studied in detail. The alcohol sensing membrane proposed here is simple to prepare and has a fairly rapid response time of <1 min. It has been successfully applied to the determination of the ethanol contents in various spirits.     

bPAK-interacting exchange factor may regulate actin cytoskeleton through interaction with actin

p21-activated kinase (PAK)-interacting exchange factor (PIX) is known to be involved in regulation of Cdc42/Rac GTPases and PAK activity. PIX binds to the proline-rich region of PAK, and regulates biological events through activation of Cdc42/Rac GTPase. To further investigate the role of PIX we produced monoclonal antibodies (Mab) against bPIX. Three clones; N-C6 against N-terminal half and C-A3 and C-B7 against C- terminal half of bPIX were generated and characterized. N-C6 Mab detected bPIX as a major band in most cell lines. C-A3 Mab recognizes GIT-binding domain (GBD), but it does not interfere with GIT binding to bPIX. Using C-A3 Mab possible bPIX interaction with actin in PC12 cells was examined. bPIX Mab (C-A3) specifically precipitated actin of the PC12 cell lysates whereas actin Mab failed to immunoprecipitate bPIX. Co-sedimentation of PC12 cell lysates with the polymerized F-actin resulted in the recovery of most of bPIX in the cell lysates. These results suggest that bPIX may not interact with soluble actin but with polymerized F-actin and revealed that bPIX constitutes a functional complex with actin. These data indicate real usefulness of the bPIX Mab in the study of bPIX role(s) in regulation of actin cyoskeleton.     

Effective isolation of magnesium lithospermate B and its inhibition of aldose reductase and fibronectin on mesangial cell line

We developed an effective isolation method of magnesium lithospermate B from Salviae miltiorrhizae Radix and found for the first time that magnesium lithospermate B shows strong in vitro inhibition (IC50=0.04 microM) of aldose reductase (AR), 2.5 times than that of clinically used epalrestat (IC50=0.1 microM) and accumulation of fibronectin dose dependently.     

Improved immunodetection of human papillomavirus E7

Human papillomavirus E7 (HPV E7) is a viral oncoprotein that plays an important role in cervical carcinogenesis through binding with retinoblastoma protein (Rb). Inactivation of Rb by E7 is necessary but not sufficient for cellular transformation, suggesting other protein-protein interactions are required for E7-mediated cellular transformation aside from the interaction with Rb. However, studies on the oncogenic function of HPV E7 have been limited by its poor immunoreactivity. In this report, we show that the fixation of purified recombinant HPV E7 on blotted nitrocellulose membrane with glutaldehyde markedly enhanced the immunoreactivity of HPV E7 protein. Using HeLa and Caski cell lines which are infected with HPV 18 and HPV 16, respectively, we demonstrated that native HPV E7 proteins also could be detected by this method. These results therefore can provide the experimental conditions for detection of HPV E7 proteins with greater sensitivity and may help to analyze E7 functions.     

Photochemical interaction of polystyrene nanospheres with 193 nm pulsed laser light

The photochemical interaction of 193 nm light with polystyrene nanospheres is used to produce particles with a controlled size and morphology. Laser fluences from 0 to 0.14 J/cm2 at 10 and 50 Hz photofragment nearly monodisperse 110 nm spherical polystyrene particles. The size distributions before and after irradiation are measured with a scanning mobility particle sizer (SMPS), and the morphology of the irradiated particles is examined with a transmission electron microscope (TEM). The results show that the irradiated particles have a smaller mean diameter ( approximately 25 nm) and a number concentration more than an order of magnitude higher than nonirradiated particles. The particles are formed by nucleation of gas-phase species produced by photolytic decomposition of nanospheres. A nondimensional parameter, the photon-to-atom ratio (PAR), is used to interpret the laser-particle interaction energetics.     

Isolation of rice allergenic cDNA clones from a rice cDNA library by immunoscreening with a polyclonal antibody specific to 16 kD rice allergenic protein

Clinical cases of type-1 hypersensitive reaction to rice (Oryza sativa) have been reported in western countries as well as in Japan. Among rice proteins, 14-16 kD globulin proteins encoded by multiple gene family have been identified as major rice allergens. In this study, a rice cDNA library was constructed using lambda UniZap vector and screened with a rat anti-16 kD globulin protein polyclonal antibody in order to isolate Korean rice allergenic cDNA clones. Five independent cDNA clones, termed RAK1-5, were obtained after second rounds of plaque assay and immunoblot analysis. These clones encoded 13-19 kD recombinant proteins upon IPTG induction, which were identified by the polyclonal antibody in immunoblot analysis. DNA sequencing analysis showed that RAK1-4 have 99% sequence homology with RA5b, and RAK5 is closely related with RA14c. This result indicated that RA5b gene is widely distributed in our cDNA library among other possible rice allergenic genes, and more study is needed to isolate heterogeneous or novel rice allergen genes.     

Calix[2]furano[2]pyrrole and related compounds as the neutral carrier in silver ion-selective electrode

The performance of calix[2]furano[2]pyrrole and related compounds used as neutral carriers for silver selective polymeric membrane electrode was investigated. The silver ion-selective electrode based on calix[2]furano[2]pyrroles gave a good Nernstian response of 57.1 mV per decade for silver ion in the activity range 1×10⁻⁶ to 1×10⁻² M. The present silver ion-selective electrode displayed very good selectivity for Ag⁺ ion against alkali and alkaline earth metal ions, NH₄⁺, and H⁺. In particular, the present Ag⁺-selective electrode exhibited very low responses towards Hg²⁺ and Pb²⁺ ions. The potentiometric selectivity coefficients of the silver ion-selective electrode exhibited a strong dependence on the solution pH. In particular, the response of the electrode to the Hg²⁺ activity was greatly diminished at pH 2.5 compared to that at pH 5.0. Overall, the performance of the present silver ion-selective electrode based on the ionophore, calix[2]furano[2]pyrrole, is very comparable to that of the electrode prepared with the commercially available neutral carrier in terms of slope, linear range, and detection limits.