Influence of different pretreatments on the accessibility of transglutaminase and tyrosinase to wool fibre proteins

Wool fibres are subject to a variety of industrial chemical treatments prior to finishing processes. The influence of such treatments on subsequent enzymatic treatments is still poorly characterised, but its importance is paramount to achieve maximal efficiency of enzymatic action on the fibres. The effect of such treatments on wool fibre structure and their significance on the accessibility of the enzymes transglutaminase and tyrosinase to their target amino acids within wool proteins was investigated. These enzymes are of great interest due to their potential as protein cross‐linkers and their capability to covalently graft beneficial compounds onto proteins. The accessibility of target amino acids was assessed using specific peptides tagged with fluorescent probes, followed by epifluorescence or confocal microscopy. Differences in the action of the different chemical pretreatments were found, with a treatment with permonosulphuric acid resulting in the greatest level accessibility to both enzymes, followed by chlorination and plasma treatments. This was confirmed by the increase in tensile strength of treated wool observed in the enzyme‐treated yarns. This work illustrates that the accessibility of these enzymes to their target aminoacids in solid substrates such as wool is key for their action and to achieve the desired property modifications. The techniques used have the advantage of permitting the visual monitoring of the diffusion of the active enzymes through the wool fibre structure and to relate this to the extent of enzymatic reaction. Crucially, this will allow an informed choice of the best wool processing stage at which to introduce such enzyme treatments.     

Effect of Trichoderma reesei tyrosinase on rheology and microstructure of acidified milk gels

The aim of this work was to study the potential of tyrosinase enzymes in structural engineering of acid-induced milk protein gels. Fat free raw milk, heated milk or a sodium caseinate solution were treated with tyrosinases from Trichoderma reesei (TrTyr) and Agaricus bisporus (AbTyr) and the reference enzyme transglutaminase (TG) prior to acid-induced gelation. TrTyr treatment increased the firmness of raw milk and sodium caseinate gels, but not that of heated milk gels, even though protein cross-linking was detected in heated milk. AbTyr did not cross-link proteins in any of the studied milk protein systems. TG was superior to TrTyr in gels prepared of heated milk. In acidified heated milk and sodium caseinate, TrTyr and TG treatment resulted in a decrease of the pore size. Scanning electron microscopy revealed more extensive particle interactions in the heated milk gels with TG than with TrTyr.     

Optical scattering of nanocrystalline Pb(ZrxTi1−x)O3 films

Optical characterization methods, like spectrophotometry at UV–vis-NIR wavelengths and prism-coupler method, were applied to polycrystalline Pb(Zr_xTi_1?x)O₃ thin films at various thicknesses. Thin films were deposited at room temperature by pulsed laser deposition on MgO (1 0 0) substrates and post-annealed at different temperatures. X-ray diffraction and atomic force microscopy were used to characterize the crystal structure and surface morphology of the thin films, respectively.Well oscillating transmission with a sharp fall near the absorption edge was found in films with high orientation and low surface roughness. Changes in the surface morphology and crystal orientation were found to modulate optical interference maxima and minima of the transmittance spectra and to increase the width of the TE₀ mode (Δβ ≈ 0.06) indicating an increase in the scattering losses of the films. Single-phase oriented films had sharpest coupling values (Δβ ≈ 0.005) of the TE₀ mode.     

THE EFFECT OF TRIOCTYLPHOSPHINE OXIDE ON PHASE AND EXTRACTION EQUILIBRIA IN SYSTEMS CONTAINING BIS( 2,4,4-TRIMETHYLPENTYL) PHOSPHINIC ACID

The metal extractant Cyanex© 272 contains bis(2,4,4-trimethylpentyl)-phosphinic acid (BTMPPA) as the main component and trioctylphosphine oxide as an impurity. As-received Cyanex 272 and pure BTMPPA were observed to significantly differ in respect to both their phase behavior during saponification and to their copper extraction ability. The differences were elucidated by investigating the effects of an addition of small amounts of tri(n-octyl)phosphine oxide (TOPO) on the phase equilibria in the system Water(2.4M NaOH)/BTMPPA/n-Hexane at 25?°C as well as in the system Water(2.4M NaOH)/BTMPPA at various temperatures. In the absence of TOPO a large microemulsion region and a small region of lyotropic liquid crystalline phase with lamellar structure are formed. When TOPO is added into the system the lamellar phase gradually disappears. The effects of TOPO on metal extraction equilibria were studied by measuring the distribution of copper(II) between a perchloric acid solution and a BTMPPA in chloroform solution in the presence and absence of tri(n-octyl)phosphine oxide.     

Optical properties of BaTiO3 thin films: Influence of oxygen pressure utilized during pulsed laser deposition

The crystallographic properties of BaTiO₃ thin films, grown by pulsed laser deposition on MgO substrates, were found to be strongly influenced by the oxygen pressure used during growth. Low pressure grown films were c-oriented while increasing oxygen pressure produced films with preferred a-orientation. The crystal reorientation resulted in the shift of optical birefringence from +0.04 to −0.025 with low levels of birefringence in films possessing low tetragonal distortion. Mach-Zehnder electro-optic waveguide modulators were fabricated to characterize the electro-optic properties of the deposited films and to evaluate the suitability of these films for planar optical applications. An effective electro-optic coefficient of 23 pm/V was obtained for a c-axis oriented film near the crystal c→a reorientation point.     

Tyrosinase‐catalysed grafting of food‐grade gallates to chitosan: surface properties of novel functional coatings

Plasma‐activated biaxially oriented polypropylene (BOPP) films and paper substrate have been coated with functional chitosan solutions. Plasma treatment increased the amount of surface peroxide groups and carboxyl groups on the BOPP films. As a result of plasma activation, the surface energy increased from 30 to 50 dynes/cm. The enzyme tyrosinase catalysed the grafting of octyl gallate and dodecyl gallate to amino groups of chitosan polysaccharide. Resulting coatings exhibited strong antimicrobial activity against Gram‐positive Staphylococcus aureus and Gram‐negative Listeria innocua. After 24 h of incubation, a total reduction in both bacteria cell numbers varied between >4.9 and 1.4 logarithmic units. Grafted dodecyl gallate and octyl gallate at pH 6 were found to have the lowest reduction values of <3 logarithmic units for S. aureus, while 1.4 logarithmic reduction value was obtained for grafted dodecyl gallate at pH 6 against L. innocua. Chitosan coatings were also effective barrier layers against oxygen transmission although the transmission rates clearly increased in high‐humidity conditions. In dry conditions, however, the transmission rate of 2 cm³/(m² · 24 h) was obtained with chitosan‐coated BOPP. Coatings did not have any effects on water vapour transmission. Both gallates were successfully grafted at pH 6. As increased flocculation and colour formation indicated, the tyrosinase‐catalysed grafting was more powerful with octyl gallate. Dodecyl gallate containing chitosan coatings was more hydrophobic as compared to octyl gallate. Total migration of substances into 95% ethanol was ≥5 mg/dm², thus materials may be exploitable in packaging purposes in direct contact with certain foodstuffs. Copyright © 2008 John Wiley & Sons, Ltd.     

Planar inductors on an LTCC substrate realized by thegravure-offset-printing technique

The fabrication and properties of planar inductors on a low-temperature co-fired ceramic (LTCC) substrate are studied together with computational simulations of their properties. One- and two-layer inductors with both square and spiral shapes were fabricated with and without a ground plane. The narrowest line width of conductors was 60 μm and the size of the inductors was limited to 2.5×2.5 mm². Inductors were printed on the LTCC sheet by the gravure-offset printing. Via holes needed in the two-layer structures were made by excimer and Nd-YAG lasers. The layers were aligned and laminated at 70°C with a pressure of 20 10⁶ N/mm² for 15 min, and the laminated layers were co-fired at a peak temperature of 850°C. The dependence of the electrical values on the geometrical dimensions and material properties of the inductor structures was studied both experimentally and by simulation. The electrical measurements were made by an LCR meter and a network analyzer, and the dimensions of the printed conductors were measured by a surface profilometer. The measured inductance values varied from a few nH to hundreds of nH depending on the structure and the resonant frequencies of the coils ranged from 300 MHz for the microstrip coils up to several GHz for the one-layer inductor structures. The measured inductance values were higher than the calculated ones and the variation of the measured electrical values was in the range of ±10%     

Electronic Conductivity and Dielectric Properties of Nanocrystalline CeO2 Films

The growth of dielectric layers on silicon substrates has attracted a great deal of recent interest given their potential applicability in the fabrication of high quality silicon-on-insulator (SOI) structures, high density capacitor devices, and stable buffer layers between silicon and other materials. In this study, nanocrystalline CeO₂ films were deposited on n-type (100) silicon substrates using pulsed laser deposition (PLD) to form a gate dielectric for a Pt/n-Si/CeO₂/Pt MOS device. XRD, AFM and FESEM measurements were used to characterize the crystal structure and grain size of the CeO₂ films. The electrical properties of the device structure were examined by capacitance-voltage (C-V) and impedance spectroscopy measurements. The CeO₂ films exhibited an activated conductivity, characterized by an activation energy E_a = 0.45 eV. An estimated room temperature electron mobility _e of 2.8 × 10^{– 7} cm²/Vs leads to a corresponding electron concentration n of 5.5 × 10¹⁷ cm^{– 3}. In contrast to conventional MOS capacitors, we find an additional capacitive contribution under strong accumulation conditions as a result of space charge effects inside the CeO₂ thin film.     

Unbalanced magnetic pull induced by arbitrary eccentric motion of cage rotor in transient operation. Part 1: Analytical model

Eccentric rotor motion of an electric motor induces an unbalanced magnetic pull. This eccentricity force may couple the electromagnetic system with the flexural vibration modes of the shaft. This paper presents an analytic model for this eccentricity force allowing an arbitrary rotor motion and transient operation. The general equations were simplified for the constant flux and steady-state operation. These simplified equations correspond well to the results presented earlier.