Study of the Antioxidative Properties of Several Amino Acid-Type Surfactants and their Synergistic Effect in Mixed Micelle

Cysteine and methionine, two sulfur-containing amino acids (AA), were introduced in their surfactant forms as potential antioxidants. The antioxidative (AOX) properties of lauroyl methionine (C12-Met) and lauroyl cysteine (C12-Cys) was investigated by means of the oxygen radical absorbance capacity assay. Both the surfactants exhibited excellent AOX behavior at the premicellar state and micellar medium. The AOX behavior was found to be comparable for both the surfactants at their premicellar states. However, in micellar medium, C12-Met showed better AOX property than C12-Cys. The AOX power of the surfactants was compared with other previously developed AA-type surfactants. The order of the AOX power was found to be: C12-tryptophan > C12-tyrosine ≈ C12-methionine ≈ C12-cysteine > C12-histidine at the premicellar state and C12-tryptophan > C12-tyrosine > C12-methionine > C12-cysteine > C12-histidine at the micellar state. C12-Cys displayed lower AOX property in micellar medium due to its dimer formation tendency. Based on the HPLC and UPLC-Q-TOF-MS analysis, the dimer formation of C12-Cys was found to be accelerated due to the micellar environment and results into negative synergistic effect on other aromatic AA-type surfactants. However, the presence of C12-His in the micellar solution of C12-Cys resulted no synergistic effect due to stronger H-bonding between the surfactants and resulting less dimer formation.     

The Potential Role of Hepatocyte Growth Factor in Degenerative Disorders of the Synovial Joint and Spine

This paper aims to provide a comprehensive review of the changing role of hepatocyte growth factor (HGF) signaling in the healthy and diseased synovial joint and spine. HGF is a multifunctional growth factor that, like its specific receptor c-Met, is widely expressed in several bone and joint tissues. HGF has profound effects on cell survival and proliferation, matrix metabolism, inflammatory response, and neurotrophic action. HGF plays an important role in normal bone and cartilage turnover. Changes in HGF/c-Met have also been linked to pathophysiological changes in degenerative joint diseases, such as osteoarthritis (OA) and intervertebral disc degeneration (IDD). A therapeutic role of HGF has been proposed in the regeneration of osteoarticular tissues. HGF also influences bone remodeling and peripheral nerve activity. Studies aimed at elucidating the changing role of HGF/c-Met signaling in OA and IDD at different pathophysiological stages, and their specific molecular mechanisms are needed. Such studies will contribute to safe and effective HGF/c-Met signaling-based treatments for OA and IDD.     

Thermal depoling and relaxation property of (Na,K)NbO3 system

(Na,K)NbO₃ ceramics was synthesized by an ordinal solid state reaction method. Thermally stimulated depolarization current (TSDC) pattern of the poled ceramics was measured. Electrically poled Na_0.5K_0.5NbO₃ ceramics generated anomalous large discharge current at around 370 °C during the heating step due to the thermal relaxation of oxygen vacancy. The oxygen vacancy piled up around electrodes and formed the electrically inhomogeneous structure in the ceramics. In addition, the anomalous current of K-riched ceramics was larger than that of Na-riched one. This result suggested that the equilibrium composition of NaNbO₃–KNbO₃ system was near to Na-riched composition against Na_0.5K_0.5NbO₃.     

Predicting Solid–Liquid Equilibrium of Fatty Acid Methyl Ester and Monoglyceride Mixtures as Biodiesel Model Fuels

Fatty acid methyl esters from plant oils are the main component of biodiesel and used as a substitute for petroleum diesel. Biodiesel generally contains a small amount of monoglycerides as intermediate compounds, which have high melting points and often solidify and clog fuel filters. The prediction of the cold-flow property of biodiesel is of great importance for practical application. In this study, a thermodynamic study was conducted for mixtures of monoglycerides and fatty acid methyl esters. Temperatures of the solid–liquid equilibrium for the mixtures were measured by differential scanning calorimetry and visual observation, while the theoretical values were calculated using the modified Universal Quasi-chemical Functional-group Activity Coefficients (UNIFAC) model (Dortmund). The theoretical and experimental results were in good agreement, especially for binary mixtures of monoglycerides and methyl esters. The importance of monoglycerides on the cold-flow properties of biodiesel was determined, and the effects could be well described by the modified UNIFAC model (Dortmund).     

Differential Scanning Calorimetric Study of Solidification Behavior of Monoacylglycerols to Investigate the Cold-Flow Properties of Biodiesel

Monoacylglycerols (MAG) are impurities present in biodiesel as a result of incomplete reactions. MAG often solidify in biodiesel even at room temperature because of their high melting points. This worsens the cold-flow properties such as the cloud point and pour point. We hypothesized that several types of MAG solidify simultaneously; therefore, we performed differential scanning calorimetry of binary mixtures of MAG to elucidate their interactions during solidification. Three thermodynamic formulas were then applied to the experimental results: (1) non-solid-solution, (2) solid-solution, and (3) compound formation models. Binary mixtures of MAG showed complicated liquidus curves with multiple upward convex shapes, with which only the compound formation model fitted well. This model was applied to multicomponent mixtures that consisted of MAG and fatty acid methyl esters (FAME) as surrogate biodiesel fuels. We confirmed that the model still worked well. The results show that the compound formation model has good potential for predicting the cold-flow properties of biodiesel.     

Superplastic behaviour of Ti-48at.%Al two-phase titanium aluminide compacts made from mechanically alloyed powder

An HIP compact of MA-processed powder having a nominal composition of Ti-48at.% Al was produced. The compact consisted of a large amount of TiAl(λ) and a small amount of Ti₃Al (₂), in a completely ultra-fine equiaxed grain structure. This two-phase compact showed typical superplastic deformation behaviour. A maximum elongation of 550% was obtained. A strain exponent, n = 2, and grain size exponent, p = 2, were determined from the results of a strain-rate-change test and a creep test at constant initial stress using samples having various grain sizes, respectively. The activation energy for creep, Q_c at constant stress was calculated to be 350 kJ/mole. It is concluded that the superplastic deformation mechanism of the material under study is grain boundary sliding controlled by lattice diffusion in the TiAl phase.     

Protein patterning on functionalized surface prepared by selective plasma polymerization

Techniques for patterned modification of substrate surfaces are important for the formation of microarrays on protein chips. One strategy is based on partial plasma polymerization to create protein adhesive/non-adhesive regions of several tens of micrometers in size. Protein immobilization on a plasma functionalized surface occurs by physical adsorption of a protein solution. Distinct 80 × 80 μm² square spots of fluorescently labeled protein, immunoglobulin G, surrounded by a non-fluorescent 80 μm wide grid were observed. The monomer tetraethylene glycol diethyl ether was the best candidate for plasma polymerization to produce a protein-repellent surface. However, the choice of monomer for the protein adhesive surface was strongly dependent on the type of protein. Binding assays were performed by protein immobilization on the patterned substrate and subsequent reaction with fluorescently labeled counterpart proteins (secondary antibodies). Fluorescent patterning similar to the original pattern was observed. In contrast, patterning was not observed when a fluorescently labeled non-counterpart protein was reacted with the surface. This indicated that the proteins were selectively adsorbed onto the target patterned surface and retained their biofunctional activity in addition to having a suitable orientation of the molecule. Moreover, the protein non-adhesive layer plays a role for suppression of the background signal and enhancement of the signal to noise (S/N) ratio. The proposed technique provides a simple and robust method for protein patterning.     

Enzyme-Assisted Synthesis of Titania under Ambient Conditions

A low-temperature procedure for the synthesis of TiO₂ was developed using a water-soluble titanium complex and enzymes. Titanium–lactate and titanium–glycolate complexes were used as precursors of TiO₂. Digestive enzymes were chosen as biocatalysts for the synthesis of TiO₂ in aqueous solutions. TiO₂ powders were deposited from reaction solutions having optimal pH values for the enzymes to exhibit their catalytic activities for their original substrates. TiO₂ has been synthesized by an enzymatic reaction in an aqueous solution under ambient conditions. The XRD measurements indicated that TiO₂ powders thus obtained usually have an amorphous phase. However, after calcination at 550°C, the anatase phase was confirmed. Interestingly, the minor phase of TiO₂, brookite, was found in the sample obtained from the titanium–glycolate complex catalyzed by lipase at pH 10 after calcination at 550°C.     

Preparation of Ultrafine Fe–Pt Alloy and Au Nanoparticle Colloids by KrF Excimer Laser Solution Photolysis

We prepared ultrafine Fe–Pt alloy nanoparticle colloids by UV laser solution photolysis (KrF excimer laser of 248 nm wavelength) using precursors of methanol solutions into which iron and platinum complexes were dissolved together with PVP dispersant to prevent aggregations. From TEM observations, the Fe–Pt nanoparticles were found to be composed of disordered FCC A1 phase with average diameters of 0.5–3 nm regardless of the preparation conditions. Higher iron compositions of nanoparticles require irradiations of higher laser pulse energies typically more than 350 mJ, which is considered to be due to the difficulty in dissociation of Fe(III) acetylacetonate compared with Pt(II) acetylacetonate. Au colloid preparation by the same method was also attempted, resulting in Au nanoparticle colloids with over 10 times larger diameters than the Fe–Pt nanoparticles and UV–visible absorption peaks around 530 nm that originate from the surface plasmon resonance. Differences between the Fe–Pt and Au nanoparticles prepared by the KrF excimer laser solution photolysis are also discussed.