Bifidobacterium longum l-Arabinose Isomerase—Overexpression in Lactococcus lactis, Purification, and Characterization

Bifidobacterium longum NRRL B-41409 l-arabinose isomerase (l-AI) was cloned and overexpressed in Lactococcus lactis using a phosphate-depletion-inducible expression system. The purified B. longum l-AI was characterized using d-galactose and l-arabinose as the substrates. The enzyme was active and stable at acidic pH with an optimum at pH 6.0?C6.5. The enzyme showed the highest activity at 55?°C during a 20-min incubation at pH 6.5. The K _m value was 120?mM for l-arabinose and 590?mM for d-galactose. The V _max was 42?U mg^?1 with l-arabinose and 7.7?U mg^?1 with d-galactose as the substrates. The enzyme had very low requirement for metal ions for catalytic activity, but it was stabilized by divalent metal ions (Mg²⁺, Mn²⁺). The enzyme bound the metal ions so tightly that they could not be fully removed from the active site by EDTA treatment. Using purified B. longum l-AI as the catalyst at 35?°C, equilibrium yields of 36?% d-tagatose and 11?% l-ribulose with 1.67?M d-galactose and l-arabinose, respectively, as the substrates were reached.     

On Conformal Field Theory of SLE(κ,ρ)

SLE(κ ρ), a generalization of chordal Schramm-Löwner evolution (SLE), is discussed from the point of view of statistical mechanics and conformal field theory (CFT). Certain ratios of CFT correlation functions are shown to be martingales. The interpretation is that SLE(κ ρ) describes an interface in a statistical mechanics model whose boundary conditions are created in the Coulomb gas formalism by vertex operators with charges α _j = $\alpha_j = \frac{\rho_j}{2 \sqrt{\kappa}}SLE(κ ρ), a generalization of chordal Schramm-Löwner evolution (SLE), is discussed from the point of view of statistical mechanics and conformal field theory (CFT). Certain ratios of CFT correlation functions are shown to be martingales. The interpretation is that SLE(κ ρ) describes an interface in a statistical mechanics model whose boundary conditions are created in the Coulomb gas formalism by vertex operators with charges α _j = $\alpha_j = \frac{\rho_j}{2 \sqrt{\kappa}}SLE(κ ρ), a generalization of chordal Schramm-L?wner evolution (SLE), is discussed from the point of view of statistical mechanics and conformal field theory (CFT). Certain ratios of CFT correlation functions are shown to be martingales. The interpretation is that SLE(κ ρ) describes an interface in a statistical mechanics model whose boundary conditions are created in the Coulomb gas formalism by vertex operators with charges α _j = . The total charge vanishes and therefore the partition function has a simple product form. We also suggest a generalization of SLE(κ ρ)     

Potentiometric Detection of K+ Ions Using Gramicidin-Ionophore/Lipid Bilayer Assembly on Polyaniline Electrode

Summary: Organic electronics have their advantage over traditional silicon or inorganic electrodes in their easy processing and flexibility. For instance, polyaniline has shown to be promising electrode material for various sensing opportunities including as a use of pH-meter. As the ion-to-electrode transduction may be optimal in these organic materials with high surface area and controllable electric double layer, selectivity has often been approached with the use of ionophores. We have inserted a gramicidin ionophore in a lipid bilayer assembled on polyaniline surface and measured successfully K⁺ ion concentration potentiometrically.     

Atomic force microscopy on chromosomes, chromatin and DNA: A review

The purpose of this review is to discuss the achievements and progress that has been made in the use of atomic force microscopy in DNA related research in the last 25 years. For this review DNA related research is split up in chromosomal-, chromatin- and DNA focused research to achieve a logical flow from large- to smaller structures. The focus of this review is not only on the AFM as imaging tool but also on the AFM as measuring tool using force spectroscopy, as therein lays its greatest advantage and future. The amazing technological and experimental progress that has been made during the last 25 years is too extensive to fully cover in this review but some key developments and experiments have been described to give an overview of the evolution of AFM use from 'imaging tool' to 'measurement tool' on chromosomes, chromatin and DNA.     

Chromatic changes in the blends of electroactive polymers with comb-shaped flexible polymers

The effect of blending of alkylated polymers, which have different backbone structures, was investigated in order to improve the electronic properties of conducting polymers. Comb-shaped flexible polymer, poly(octadecyl acrylate) (PODA), was blended with rigid alkylated conducting polymers, poly(3-dodecyl-thiophene)(PDDT), and polyaniline emeraldine base (PANI)/p-dodecyl-benzenesulfonic acid (DBSA) complex, respectively, to investigate the effect of long alkyl chain of flexible polymer on the conformational mode change of rigid backbones and the effect of intermolecular interaction between these alkylated polymers. Optical microscopy was applied to observe the morphology change and obtain the phase diagrams of these blends. The intermolecular interactions that occurred in these blends were explained for each different characteristic peak obtained with FT-IR spectra. Solvatochromism (red-shift) of PDDT/PODA binary blends in solid state due to the planarity change of rigid backbone in the presence of PODA and electrochromism of PANI(DBSA)₄/PODA ternary blends due to the hydrogen bonding between the nitrogen cation of PANI complex and carbonyl group of PODA are observed in UV-Vis-NIR spectra. Interestingly, the increase of conductivity was observed in the presence of 5 wt% of PODA in PDDT/PODA binary blends and a homogeneous smectic liquid crystalline structure was clearly confirmed by cross polarized optical microscopy in PANI(DBSA)₄/PODA ternary blends.     

Reactivation of a Poisoned Metallocene Catalyst by Irradiation with Visible Light

Both oxygen and carbon dioxide are efficient catalyst poisons, remarkably reducing the ethylene polymerisation rate, increasing the molecular weight of the resulting polyethylene, and broadening its molecular weight distribution (MWD). By introducing visible light into the contaminated polymerisation system, the catalyst activity was totally recovered. The molecular weight and MWD became similar to those of a non‐poisoned system, supporting the formation of new active sites during poisoning that are responsible for the lower activity and broader MWD.     

Solubilization of polyaniline in water by interpolymer complexation

Water solubility of electro-active polymers in their doped state may provide a possibility for environmentally feasible manufacturing processes. Because previous results in this direction require expensive modifications or impractical template polymerization methods, we created a simple method of mixing components with a large molecular weight difference. The polymer which acts as an acidic dopant and provides water solubility, has to have the higher molecular weight. The formed complex resembles a block copolymer but in this case the polyaniline block is attached to the sulfonated polystyrene chain by strong physical interactions instead of chemical end-to-end linkage.     

Effect of Ground Rubber Powder on Properties of Natural Rubber

Ground rubber powder (GRP) with three different sizes was incorporated into nature rubber matrix with different loading. Cure characteristics, swelling behaviour, crosslink density, tensile fractured surface, and mechanical properties have been studied. Based on the cure characteristics, it is evident that the processability of the rubber compounds has not changed obviously with the different GRP loading. The introduction of GRP in virgin rubber leads to the increase in swelling degree and the decrease in crosslink density. Tensile strength, hardness and abrasion resistant deteriorate with the increase of GRP loading, but the tear resistance gets better. If the ground rubber particles are smaller, the properties are more similar to the virgin rubber. Because of the phase separation of the GRP and matrix, the properties get worse with the bigger ground rubber powder.