Chemoenzymatic synthesis of amylose-grafted polyacetylenes

Summary This paper reports chemoenzymatic synthesis of amylose-grafted polyacetylenes according to the following reaction manners. Polymerization of a N-propargylamide monomer having a maltooligosacchairde chain was firstly carried out using a water-soluble Rh-catalyst in water, giving maltooligosaccharide-grafted polyacetylene. The ¹H NMR spectrum of the product supported the structure of the desired polyacetylene. Then, the enzymatic chain-elongation from the oligosaccharides of the polymer was performed using glucose-1-phosphate catalyzed by phosphorylase to give the polyacetylene having amylose side-chains. Furthermore, copolymerization of the monomer with the other N-propargylamide monomer was performed under the conditions similar to those of homopolymerization. The phosphorylase-catalyzed enzymatic chain-elongation of the copolymer was also carried out. The DLS measurement of the amylose-grafted polyacetylenes in alkaline solution was conducted.     

Experimental study on geometric structure of isolated mixing region in impeller agitated vessel

Isolated mixing region in agitated vessel with rotated two-bladed paddle impeller and no baffle was visualized experimentally and its structural property was investigated in detail. A set of thin filaments spirally wrapping around the core of the toroidal isolated mixing region is observed under low Reynolds number conditions, which is smaller than 60. Three-dimensional geometrical structure of filament in isolated mixing region depends on the periodical perturbations caused by the rotating impeller. We have succeeded in the determination of three-dimensional geometrical structure of filament in isolated mixing region based on relation between the movement of fluid particle and filament numbers and/or wire turns. Interestingly, the wire turns of filaments are opposite to movements of fluid particles.     

Characterization of pH-dependent micellization of polystyrene-based cationic block copolymers prepared by reversible addition-fragmentation chain transfer (RAFT) radical polymerization

A series of block copolymers composed of a fixed length of an (ar-vinylbenzyl)trimethylammonium chloride (Q) block (the number average degree of polymerization of the Q block, DP_n,Q=57) and varying lengths of an N,N-dimethylvinylbenzylamine (A) block (the number average degrees of polymerization of the A blocks, DP_n,A, ranging 11-50) were prepared by reversible addition-fragmentation chain transfer (RAFT) radical polymerization, and their pH-dependent micellization was characterized by potentiometric titration, ¹H NMR spectroscopy, dynamic and static light scattering, and fluorescence techniques as a function of the A block length. At pH<5.5, the A block is fully protonated, and hence the block copolymers act as a simple polyelectrolyte, dissolving molecularly in acidic water. At pH>7, the A block becomes deprotonated, and thereby the block copolymers aggregate into a micelle composed of hydrophobic microdomains formed from the deprotonated A blocks. Results of light scattering and fluorescence measurements indicated that the micellization behavior depended strongly on the length of the A block. The number of polymer chains comprising one micelle (i.e. mean aggregation number, N_agg) increased from 3 to 12 as DP_n,A increased from 11 to 50 at pH 10.0. In the case of a random copolymer of Q and A with an A/Q molar ratio similar to that of a block copolymer with DP_n,A=50, N_agg∼1 (i.e. unimolecular micelle) was confirmed by static light scattering at pH 10.0.     

Method for identification of mutant glutathione S-transferases conferring enhanced resistance to the anti-cancer drug chlorambucil

We screened library of mutant glutathione S-transferases (GSTs) in Escherichia coli by successive treatments with anti-cancer drug chlorambucil and identified mutant GSTs that conferred enhanced resistance to host against chlorambucil compared with wild-type GST. This study provides a method to develop enzymes with improved efficiency of detoxification against cytotoxic substances.     

Asymptotic stabilization with locally semiconcave control Lyapunov functions on general manifolds

Asymptotic stabilization on noncontractible manifolds is a difficult control problem. If a configuration space is not a contractible manifold, we need to design a time-varying or discontinuous state feedback control for asymptotic stabilization at the desired equilibrium.     

Distributed Telerobotics System Based on Common Object Request Broker Architecture

This paper proposes using CORBA as communication architecture to integrate network-distributed software and robotic systems in support systems for the aged or disabled. The proposed method keeps system costs low and expands availability. Its high scaling and inter-operating ability allows clients and server objects that are written in different languages, run in different operating systems, and connected to different networks to inter-operate. It also enables the system to be extended and integrated with other technologies and applications distributed over the Internet. Based on CORBA, we developed hardware base including a robot arm and an omnidirectional mobile robot and application servers including a task-level robot arm control server, live feedback image server, mobile robot control server and iGPS server. By remotely controlling mobile robot to cooperate with the robot arm, the caregivers or family member can use the developed system for some basic services to the aged or disabled.     

Facilitated transport of ethyl docosahexaenoate through solution-cast perfluorosulfonated ionomer membranes

The facilitated transport of ethyl docosahexaenoate (DHA-Et) through the thin solution-cast perfluorosulfonated ionomer membranes has been studied. The carrier of DHA-Et was silver ion and was immobilized in the support ionomer membrane by electrostatic forces. In this system, the feed phase, membrane phase, and receiving phase had the same solvent. This system was already proved to be highly stable in our previous work. When ethanol/water (85/15) was used as the solvent, the DHA-Et permeance in the cast membrane was about four times higher than that in the commercial Nafion® 117 membrane, due to the smaller membrane thickness. In the case of acetone solvent, a high selectivity of DHA-Et to ethyl oleate of 42 and a high facilitation factor of 153 were obtained. These membrane performances were superior to those of the Nafion® 117 membrane. The effects of membrane preparation conditions, such as annealing temperature and kinds of polar solvents added to the ionomer solution before annealing, on the membrane performance was investigated in detail. Furthermore, small-angle X-ray scattering (SAXS) measurement was carried out to study the membrane structure. The experimental result suggests higher crystallinity in the cast membrane annealed at higher temperature. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 961–968, 1999     

Catalytic dehydrochlorination of 1,2-dichloroethane into vinyl chloride over polyacrylonitrile-based active carbon fiber

Dehydrochlorination of 1,2-dichloroethane (1,2-DCE) into vinyl chloride (VC) was carried out over polyacrylonitrile-based active carbon fibers (PAN-ACFs). PAN-ACFs showed excellent catalytic activity, although the lifetime was not sufficiently long enough for practical application. X-ray photoelectron spectroscopy (XPS) revealed that the active site was pyridinic nitrogen and that chlorine stayed on the surface after the reaction. Coke was also produced in the pores, as suggested by the weight increase. The heat-treatment after the reaction released hydrogen chloride from the ACF, but no catalytic activity was restored. The preheat-treatment was found to shorten the catalytic lifetime.

An optimum temperature and uniform distribution in the catalyst bed achieved by this fluidized bed may provide a practical process of sufficient life.     

Preparation and properties of bio‐based epoxy montomorillonite nanocomposites derived from polyglycerol polyglycidyl ether and ε‐polylysine

Glycerol polyglycidyl ether (GPE) and polyglycerol polyglycidyl ether (PGPE) were cured with ε‐poly(L ‐lysine) (PL) using epoxy/amine ratios of 1 : 1 and 2 : 1 to create bio‐based epoxy cross‐linked resins. When PGPE was used as an epoxy resin and the epoxy/amine ratio was 1 : 1, the cured neat resin showed the greatest glass transition temperature (T_g), as measured by differential scanning calorimetry. Next, the mixture of PGPE, PL, and montomorillonite (MMT) at an epoxy/amine ratio of 1 : 1 in water was dried and cured finally at 110°C to create PGPE‐PL/MMT composites. The X‐ray diffraction and transmission electron microscopy measurements revealed that the composites with MMT content 7–15 wt % were exfoliated nanocomposites and the composite with MMT content 20 wt % was an intercalated nanocomposite. The T_g and storage modulus at 50–100°C for the PGPE‐PL/MMT composites measured by DMA increased with increasing MMT content until 15 wt % and decreased at 20 wt %. The tensile strength and modulus of the PGPE‐PL/MMT composites (MMT content 15 wt %: 42 and 5300 MPa) were much greater than those of the cured PGPE‐PL resin (4 and 6 MPa). Aerobic biodegradability of the PGPE‐PL in an aqueous medium was ～ 4% after 90 days, and the PGPE‐PL/MMT nanocomposites with MMT content 7–15 wt % showed lower biodegradability. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009