Molecular dynamics simulation of swollen membrane of perfluorinated ionomer

Molecular dynamics simulations of the swollen membrane of perfluorinated ionomer, which is composed of poly(tetrafluoroethylene) backbones and perfluosulfonic pendant side chains, have been undertaken to analyze the static and dynamic properties of the water and the side chain in the membrane. The calculations were carried out for four different water contents, 5, 10, 20 and 40 wt %, at 358.15 K and 0.1 MPa. The results are summarized as follows: (1) The sulfonic acid is the unique site to which water molecules can bind, and the other sites in the pendant side chain have no bound water even at high water concentration. (2) Sulfonic acids aggregate in the short range within 4.6-7.7 A despite the electrostatic repulsion between them. In such aggregates, a water molecule bridges two sulfonic acids. (3) Pendant side chains prefer to orient perpendicular to the hydrophilic/hydrophobic interface, and long-range correlation of side chain orientations is observed at 20 and 40 wt % water uptake membranes. (4) In a low water uptake membrane, the dynamics of water is substantially restricted due to strong attractive interactions with acidic sites. In contrast, at high water content, even the water locating near the sulfonic acid is relatively mobile. The short residence time of the bound water reveals that such water can frequently exchange position with relatively free water, which locates in the center of water cluster, in highly swollen membranes.     

A single-strand conformation polymorphism method for the large-scale analysis of mutations/polymorphisms using capillary array electrophoresis

We present a high-throughput single-strand conformation polymorphism (SSCP) method, performed on a commercially available capillary array DNA sequencer. We tested various sieving matrices and electrophoretic conditions, using 51 DNA fragments which included 45 fragments carrying only one single nucleotide polymorphism (SNP), 4 fragments having two SNPs and 2 fragments with insertion or deletion. Resolution of alleles was improved by increasing concentrations of both sieving matrices and buffers, and all examined polymorphisms of DNA fragments were detected, most of them (45 fragments) as clearly split allele peaks in heterozygotes. Allele frequencies of SNPs can be estimated accurately by determining the relative amounts of alleles in pooled DNA. In this method, the turn-around time for the analysis of 96 samples is less than 3 h. These results demonstrate that capillary array-based SSCP is an efficient and accurate technique for the large-scale quantitative analysis of mutations/polymorphisms.     

Random-phase-approximation calculations on triplet spectra of conjugated molecules

Random-phase approximations (RPA) have been applied to the calculation of the triplet π-π* transition spectra of 18 conjugated molecules in the framework of Pariser-Parr-Pople approximations. It is found that the normal RPA (n-RPA) shows the triplet instability for most molecules in the Nishimoto-Mataga approximation of electron-repulsion integrals. However, it is shown that this instability can be circumvented by the use of the renormalized RPA (r-RPA) in which the correlated ground states are calculated by the second-order perturbation theory. It is also shown that even in the n-RPA the suitable parametrization of electron-repulsion integrals removes this instability. It is ascertained that such an increasing order of energies as ω(n-RPA)<ω(Tamm-Dancoff approximation)<ω(r-RPA) holds for most of energy levels.     

Association behavior of fluorine-containing and non-fluorine-containing methacrylate-based amphiphilic diblock copolymer in aqueous media

Fluorine-containing amphiphilic block copolymers, poly(sodium methacrylate)-block-poly(nonafluorohexyl methacrylate) (NaMAm-b-NFHMAn) (m:n = 61:12, 72:33, 64:57), and the corresponding non-fluorine-containing amphiphilic block copolymer, poly(sodium methacrylate)-block-poly(hexyl methacrylate) (NaMAm-b-HMAn) (m:n = 64:10, 69:37, 67:50), were synthesized. Both polyNaMA-b-polyNFHMA and polyNaMA-b-polyHMA formed micelles above critical micelle concentrations, (cmc's), around 3 x 10(-5) to 1 x 10(-4) mol/L, while neither polymer decreased surface tension of aqueous solutions. The size and shape of the micelles were examined by dynamic light scattering, small-angle neutron scattering, and small-angle X-ray scattering. PolyNaMA-b-polyHMA appeared to form only spherical micelles, while polyNaMA-b-polyNFHMA with a long NFHMA segment formed both spherical and rodlike micelles. The micelles of fluorine-containing block copolymers were obviously larger than those of non-fluorine-containing block copolymers with the same chain length and the same hydrophilic/hydrophobic chain ratio. The fluorine-containing block copolymer selectively solubilized fluorinated dye into the water phase when a mixture of decafluorobiphenyl and 2,6-dimethylnaphthalene was added to the micelle solution.     

ISOLATION OF BLEPHARISMIN-BINDING 200 kDa PROTEIN RESPONSIBLE FOR BEHAVIOR IN Blepharisma

Abstract— The ciliated protozoan, Blepharisma, shows an avoidance reaction (step-up photophobic response) in response to light stimulation. A profile of a gel-permeation of a crude detergent-solubilized sample of the cells resulted in several red-colored fractions. Among these blepharismin-containing fractions, the fractions III-V did not contain amino acids. The peak of fraction II monitored by 580 nm absorbance was much smaller. A prominent peak appeared in fraction I, which contained a large amount of amino acids. The absorption spectrum of fraction I was well fitted to the action spectrum of the step-up photophobic response, although free pigment (blepharismin) also fitted. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of this fraction resulted in a thicker band corresponding to molecular mass of 200 kDa. These results suggest that the 200 kDa chromoprotein (blepharismin-protein complex) is responsible for the step-up photophobic response in Blepharisma. The absorption spectrum of free chromophore dissociated from the chromophore-protein complex was identical to free red pigment termed blepharismin. The absorption spectrum of the other fractions agreed with that of thin-layer chromatography-purified red pigment, indicating that the pigments contained in these fractions are free pigment dissociated from the chromophore-protein complex.     

Synthesis and characterization of polypropylene-based block copolymers possessing polar segments via controlled radical polymerization

A new method to prepare the polypropylene (PP) macroinitiator for controlled radical polymerization was described. Bromination of terminally-unsaturated PP was carried out by using N-bromosuccinimide and 2,2′-azobis(isobutyronitrile) to give a brominated PP (PP-Br), that has allylic bromide moieties at or near the chain ends. Thus, the obtained PP-Br was successfully used as a macroinitiator for radical polymerization of styrene, methyl methacrylate, and n-butyl acrylate using a copper catalyst system. From ¹H NMR analysis, it was confirmed that the chain extension polymerization was certainly initiated from allylic bromide moieties with high efficiency, leading to the PP-based block copolymers linking the polar segment. From differential scanning calorimetry, it was observed that peak melting temperature of block copolymers was higher than that of PP-Br and the obtained PP-PS block copolymers with different compositions of each segment demonstrated the unique morphological features due to the microphase separation between both segments. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 812–823, 2009     

Nanometer‐sized polyradical particles: Organic magnetic dot array formed on a silicon microfabricated substrate

A magnetically active, purely organic dot array was formed by the selective deposition of polyradical nanoparticles on array‐like‐formed pits on a silicon substrate. The nanometer‐sized polyradical particles, poly(4‐methacryoyloxy‐2,2,6,6‐tetramethylpiperidine‐1‐oxyl), were prepared by the emulsion polymerization of 4‐methacryloyloxy‐2,2,6,6‐tetramethylpiperidine‐1‐acetoxyl followed by a deprotection reaction and oxidation in air. The size (diameter) and radical spin concentration of the polyradical nanoparticles were tunable between the polymerization and oxidation conditions. Electrochemical studies revealed the redox property of the polyradical nanoparticles. The magnetic response image of the polyradical nanoparticles was obtained by magnetic force microscopy, reflecting their radical spin concentrations. These results suggested a possible approach for the use of organic polyradical nanoparticles as organic magnetic dot arrays. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 521–530, 2007     

In-situ investigations of the photocatalytic reaction of no with propane on the vanadium silicalite-1 catalyst

The in-situ characterization of the vanadium silicalite-1 catalyst (VS-1) by means of photoluminescence, ESR and XAFS investigative techniques revealed that this catalyst includes highly dispersed V-O moieties having a tetrahedral coordination in C_3v symmetry with one short V=O bond (1.63Å) and three long V-O bonds (1.73Å). The photocatalytic decomposition reaction of NO into N₂ was found to proceed much more efficiently in the presence of propane than without. A dynamic quenching study of the photoluminescence spectrum of the VS-1 catalyst by the addition of NO and propane indicates that the excited state of the V-O moieties plays a significant role in this photocatalytic reaction.