Preparation of CaCO3‐based biomineralized polyvinylpyrrolidone–carboxymethylcellulose hydrogels and their viscoelastic behavior

In the blend of natural and synthetic polymer‐based biomaterial of polyvinylpyrrolidone (PVP) and carboxymethylcellulose (CMC), fabrication of CaCO₃ was successfully accomplished using simple liquid diffusion technique. The present study emphasizes the biomimetic mineralization in PVP–CMC hydrogel, and furthermore, several properties of this regenerated and functionalized hydrogel membranes were investigated. The physical properties were studied and confirmed the presence of CaCO₃ mineral in hydrogel by Fourier transform infrared spectroscopy and Scanning electron microscopy. Moreover, the absorptivity of water and mineral by PVP–CMC hydrogel was studied to determine its absorption capacity. Further, the viscoelastic properties (storage modulus, loss modulus, and complex viscosity) of mineralized and swelled samples (time: 5–150 min) were measured against angular frequency. It is interesting to know the increase of elastic nature of mineralized hydrogel filled with CaCO₃ maintaining the correlation between elastic property and viscous one of pure hydrogel. All these properties of biomineralized hydrogel suggest its application in biomedical field, like bone treatment, bone tissue regeneration, dental plaque and tissue replacement, etc. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40237.     

Response of Predatory Insect Scolothrips takahashii Toward Herbivore-Induced Plant Volatiles Under Laboratory and Field Conditions

We studied the response of a predatory thrips, Scolothrips takahashii, towards herbivore-induced plant volatiles emitted by Lima bean plants infested by two-spotted spider mites Tetranychus urticae (green form). Tests were conducted with a Y-tube olfactometer in the laboratory and with traps under field conditions. The odor of artificially damaged and uninfested Lima bean leaves was not more attractive than clean air in the Y-tube olfactometer. The predatory insects showed a greater preference for Lima bean leaves infested by the two-spotted spider mites than for either clean air or uninfested bean leaves. They showed the same preference towards infested leaves from which all spider mites and their visible products had been removed. Neither the spider mites themselves nor their products attracted the predators. In a satsuma mandarin grove, two traps with infested Lima bean plants as an odor source attracted 42 adult S. takahashii in 55 days, whereas no S. takahashii were trapped in two control traps with uninfested Lima bean plants during the same period. No S. takahashii were found during this period in the vicinity of either the sample traps or the control traps (5-m radius of each trap). These data showed that S. takahashii use herbivore-induced plant volatiles in their foraging behavior in natural ecosystems.     

Structural Analysis of the Complex between Penta-EF-Hand ALG-2 Protein and Sec31A Peptide Reveals a Novel Target Recognition Mechanism of ALG-2

ALG-2, a 22-kDa penta-EF-hand protein, is involved in cell death, signal transduction, membrane trafficking, etc., by interacting with various proteins in mammalian cells in a Ca²⁺-dependent manner. Most known ALG-2-interacting proteins contain proline-rich regions in which either PPYPXnYP (type 1 motif) or PXPGF (type 2 motif) is commonly found. Previous X-ray crystal structural analysis of the complex between ALG-2 and an ALIX peptide revealed that the peptide binds to the two hydrophobic pockets. In the present study, we resolved the crystal structure of the complex between ALG-2 and a peptide of Sec31A (outer shell component of coat complex II, COPII; containing the type 2 motif) and found that the peptide binds to the third hydrophobic pocket (Pocket 3). While amino acid substitution of Phe⁸⁵, a Pocket 3 residue, with Ala abrogated the interaction with Sec31A, it did not affect the interaction with ALIX. On the other hand, amino acid substitution of Tyr¹⁸⁰, a Pocket 1 residue, with Ala caused loss of binding to ALIX, but maintained binding to Sec31A. We conclude that ALG-2 recognizes two types of motifs at different hydrophobic surfaces. Furthermore, based on the results of serial mutational analysis of the ALG-2-binding sites in Sec31A, the type 2 motif was newly defined.     

Rearrangement of the main chain of the organocobalt polymers

The polymers 3 having pyridine moieties in the main chain were synthesized by the reaction of the organocobalt polymers 1 having cobaltacyclopentadiene moieties in the main chain with various nitriles 2. When brown colored 1 and excess 2 were heated in tetrahydrofuran at 80 °C for 24 h and then at 150 °C for 12 h in a sealed tube, the polymers 3 were obtained by the precipitation with methanol in good yields. From the spectroscopic measurements, the resulting polymers 3 were found to contain 35 – 90% of the pyridine moieties depending on the structures of 1. Received: 7 July 1997/Revised: 14 August 1997/Accepted: 25 August 1997     

Fiber structure formation in ultra-high-speed melt spinning of poly(ethylene 2,6-naphthalene dicarboxylate)

The high-speed melt spinning of poly(ethylene 2,6-naphthalene dicarboxylate) (PEN) was performed up to the take-up velocity of the ultra-high-speed region, 9 km/min. From the investigations of the structure and physical properties of the as-spun fibers, the high-speed spinning of PEN was divided into three regions in terms of the mechanism of fiber structure formation. The first region is the take-up velocity of up to 2.5 km/min and the birefringence of up to 0.08 where only a slight increase in molecular orientation was attained. At the take-up velocity of 2.5–4.5 km/min and the birefringence of 0.08–0.25, although some experimental evidences indicated that the orientation-induced crystallization did not occur, there was an increase in the fiber density which suggested the formation of some ordered structure. At the take-up velocity > 4.5 km/min and birefringence > 0.25, the orientation-induced crystallization occurred. The fibers obtained in this region were characterized by the formation of the crystalline structure dominated by the β form. The presence of the necklike deformation in the spinning line was also confirmed. The solidification temperature of the spinning line analyzed from the diameter profile suggested that the formation of β modification crystals occurred at relatively low crystallization temperatures in comparison with that in an isotropic state. Therefore it was indicated that the presence of elongational stress in the spinning line promoted the formation of the β modification crystals. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 1415–1427, 1997     

Mutations Associated with Functional Disorder of Xanthine Oxidoreductase and Hereditary Xanthinuria in Humans

Xanthine oxidoreductase (XOR) catalyzes the conversion of hypoxanthine to xanthine and xanthine to uric acid with concomitant reduction of either NAD⁺ or O₂. The enzyme is a target of drugs to treat hyperuricemia, gout and reactive oxygen-related diseases. Human diseases associated with genetically determined dysfunction of XOR are termed xanthinuria, because of the excretion of xanthine in urine. Xanthinuria is classified into two subtypes, type I and type II. Type I xanthinuria involves XOR deficiency due to genetic defect of XOR, whereas type II xanthinuria involves dual deficiency of XOR and aldehyde oxidase (AO, a molybdoflavo enzyme similar to XOR) due to genetic defect in the molybdenum cofactor sulfurase. Molybdenum cofactor deficiency is associated with triple deficiency of XOR, AO and sulfite oxidase, due to defective synthesis of molybdopterin, which is a precursor of molybdenum cofactor for all three enzymes. The present review focuses on mutation or chemical modification studies of mammalian XOR, as well as on XOR mutations identified in humans, aimed at understanding the reaction mechanism of XOR and the relevance of mutated XORs as models to estimate the possible side effects of clinical application of XOR inhibitors.     

A particle‐scale index in the quantification of mixing of particles

Discrete element method (DEM) is a useful tool for obtaining details of mixing processes at a particle scale. It has been shown to satisfactorily describe the flow structure developed in bladed mixers. Here, the advantage is taken of the microstructure gained from DEM to evaluate how best to quantify the microstructure created by mixing. A particle‐scale mixing index (PSMI) is defined based on coordination numbers to represent the structure of a particle mixture. The mixture quality is then analyzed qualitatively and quantitatively in three different ways: a macroscopic mixing index based on the conventional approach, coordination number, and PSMI. Their effectiveness is examined based on DEM data generated for different particle loading arrangements and binary mixtures of particles with various volume fractions, size ratios, and density ratios. Unlike the two other methods, PSMI reveals in a straightforward manner whether a binary mixture of different particles is mixing or segregating over time, while being able to detect particle‐scale structural changes accompanying the mixing or segregation processes in all the mixtures investigated. Moreover, PSMI is promising in that it is not influenced by the size and number of samples, which afflict conventional mixing indexes. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

2-[1-(2,6-Dibenzhydryl-4-chlorophenylimino)ethyl]-6-[1-(arylimino)ethyl]pyridyliron(II) dichlorides: Synthesis,characterization and ethylene polymerization behavior

A series of 2-[1-(2,6-dibenzhydryl-4-chlorophenylimino)ethyl]-6-[1-(arylimino)ethyl]pyridine ligands (L1–L5) as well as the ligand 2,6-bis[1-(2,6-dibenzhydryl-4-chloro-phenylimino)ethyl]pyridine (L6) were synthesized and reacted with FeCl₂·4H₂O to afford the iron(II) dichloride complexes [LFeCl₂] (Fe1–Fe6). All new compounds were fully characterized by elemental and spectroscopic analysis, and the molecular structures of the complexes Fe1, Fe2 and Fe4 were determined by single-crystal X-ray diffraction, which revealed a pseudo-square-pyramidal geometry at iron. Upon activation with either MAO or MMAO, all iron pre-catalysts exhibited very high activity in ethylene polymerization with good thermal stability. To the best of our knowledge, the current system showed the highest activity amongst iron bis(imino)pyridine pre-catalysts reported to-date. The polymerization parameters were explored to determine the optimum conditions for catalytic activity, which were typically found to be 2500 eq. Al to Fe at 60 °C in the presence of MMAO, and 80 °C in the presence of MAO. The resultant polyethylene possessed a narrow molecular polydispersity index (PDI) consistent with the formation of single-site active species.     

Synthesis of stable and soluble one-handed helical poly(substituted acetylene)s without chiral pendant groups via polymer reaction in membrane state

A soluble and stable one-handed helical conjugated polymer without the coexistence of any other chiral moieties was successfully synthesized by asymmetric-induced polymerization of a chiral monomer having two hydroxyl groups followed by desubstitution of the chiral groups in a solid membrane state. The reason for the success was the polymer reaction was carried out in the membrane state. This is an alternative method to obtain such a unique chiral polymer which was obtained only by the helix-sense-selective polymerization (HSSP) we reported before. In addition the efficiency of the chiral induction was higher than that of the HSSP. It is interesting that the “Membrane state” acted like as if a protecting group.     

Electrochemical durability of single-wall carbon nanotube electrode against anodic oxidation in water

The electrochemical capability of single-wall carbon nanotube (SWCNT) electrodes is investigated to establish their reliability in practical applications. Direct current (DC) voltage of +10 V is applied across the SWCNT anode and Pt cathode in water, and the electrochemical fracturing behavior of SWCNTs is analyzed using transmission electron microscopy and atomic force microscopy. A considerable number of short SWCNTs, with lengths of less than 200 nm, are observed to be electrochemically generated. This result suggests that the anodic corrosion of SWCNTs occurs even in water, a non-electrolyte liquid. Raman spectroscopy and a comparison study of the anodization behavior of SWCNTs with narrow (0.9 nm) and wide (1.8 nm) diameters indicate that the durability of narrow SWCNTs is lower than that of the wide SWCNTs.