Effects of Intramolecular Distance between Amyloidogenic Domains on Amyloid Aggregation

Peptide/protein aggregation is implicated in many amyloid diseases. Some amyloidogenic peptides/proteins, such as those implicated in Alzheimer’s and Parkinson’s diseases, contain multiple amyloidogenic domains connected by “linker” sequences displaying high propensities to form turn structures. Recent studies have demonstrated the importance of physicochemical properties of each amino acid contained in the polypeptide sequences in amyloid aggregation. However, effects on aggregation related to the intramolecular distance between amyloidogenic domains, which may be determined by a linker length, have yet to be examined. In the study presented here, we created peptides containing two copies of KFFE, a simple four-residue amyloidogenic domain, connected by GS-rich linker sequences with different lengths yet similar physicochemical properties. Our experimental results indicate that aggregation occurred most rapidly when KFFE domains were connected by a linker of an intermediate length. Our experimental findings were consistent with estimated entropic contribution of a linker length toward formation of (partially) structured intermediates on the aggregation pathway. Moreover, inclusion of a relatively short linker was found to inhibit formation of aggregates with mature fibril morphology. When the results are assimilated, our study demonstrates that intramolecular distance between amyloidogenic domains is an important yet overlooked factor affecting amyloid aggregation.     

Preparation of TiO(2) Nanocrystallite Powders Coated with 9 mol% ZnO for Cosmetic Applications in Sunscreens

The preparation of TiO(2) nanocrystallite powders coated with and without 9 mol% ZnO has been studied for cosmetic applications in sunscreens by a co-precipitation process using TiCl(4) and Zn(NO(3))(2)·6H(2)O as starting materials. XRD results show that the phases of anatase TiO(2) and rutile TiO(2) coexist for precursor powders without added ZnO (T-0Z) and calcined at 523 to 973 K for 2 h. When the T-0Z precursor powders are calcined at 1273 K for 2 h, only the rutile TiO(2) appears. In addition, when the TiO(2) precursor powders contain 9 mol% ZnO (T-9Z) are calcined at 873 to 973 K for 2 h, the crystallized samples are composed of the major phase of rutile TiO(2) and the minor phases of anatase TiO(2) and Zn(2)Ti(3)O(8). The analyses of UV/VIS/NIR spectra reveal that the absorption of the T-9Z precursor powders after being calcined has a red-shift effect in the UV range with increasing calcination temperature. Therefore, the TiO(2) nanocrystallite powders coated with 9 mol% ZnO can be used as the attenuate agent in the UV-A region for cosmetic applications in sunscreens.     

Palladium‐Catalyzed,Chelation‐Assisted Stereo‐ and Regioselective Synthesis of Tetrasubstituted Olefins by Oxidative Heck Arylation

An efficient synthesis of tetrasubstituted olefins was achieved via a palladium‐catalyzed, chelation‐assisted oxidative Heck arylation protocol from trisubstituted olefins bearing a tether with a directing group in a completely stereo‐ and regioselective manner. The stereo‐ and regioselectivity as well as excellent yields of tetrasubstituted olefins originated from the stabilization of a palladium intermediate by chelation between the palladium center and a directing group.     

Effects of irrigation solutions on the surface of protaper instruments: A microscopy study

The aim of this study was to evaluate the effects of sodium hypochlorite (NaOCl), chlorhexidine digluconate (CHX), and mixture of tetracycline, citric acid, and detergent (MTAD) solutions on the surfaces of nickel titanium (NiTi) rotary files with scanning electron microscopy (SEM) and atomic force microscopy (AFM). Irrigation solutions including 2.5% NaOCl, 5% NaOCl, 2% CHX, and MTAD were used. Four new ProTaper rotary NiTi files (F3) were immersed in each four irrigation solutions for 10 min, separately. One untreated NiTi file was used as a control specimen. The surface analysis was performed with SEM and AFM. The surface analysis in AFM was performed on 12 different regions located between first and second millimeters from the tip. SEM images were taken with different magnifications. No surface alteration was recorded under SEM evaluation. AFM revealed that the root mean square (RMS) values of all treated specimens were statistically higher than the control sample (P < 0.05). The sample which was treated with CHX showed lowest RMS values in test groups. All tested solutions caused surface alterations. CHX demonstrated limited surface alterations when compared to the other tested solutions. Microsc. Res. Tech. © 2012 Wiley Periodicals, Inc.     

Effects of microencapsulated Allyl isothiocyanate (AITC) on the extension of the shelf-life of Kimchi

Allyl isothiocyanate (AITC) is a well-recognized antimicrobial agent but, application of AITC to food systems is limited due to its high volatility and strong odor. This study was performed to overcome the volatility of AITC by encapsulation using gum Arabic and chitosan and to investigate the effect of microencapsulated AITC as a natural additive on the shelf-life and quality of Kimchi. AITC loaded microparticles were prepared using gum Arabic and chitosan and were added to Kimchi at various concentrations (0-0.02%, w/w). The titratable acidity, pH, microbial changes, and sensory test of Kimchi were examined for 15days at different fermentation temperatures (4 and 10°C). The pH of Kimchi containing AITC microparticles was significantly higher than that of control and the higher the quantity of added AITC, the higher the pH became. The titratable acidity of Kimchi increased during storage especially, titratable acidity of control increased significantly higher than those of Kimchi with added AITC microparticles. The number of Leuconostoc and Lactobacillus species in Kimchi decreased with an increase in the concentration of AITC. The addition of AITC induced reduction of sour taste and improvement of the texture of Kimchi during fermentation. However, as the content of AITC increased, the scores of overall acceptability decreased due to the odor of AITC. These results indicate that addition of AITC (less than 0.1%) to Kimchi is an effective way of enhancing the shelf-life of Kimchi without reducing quality.     

Physiochemical properties and prolonged release behaviours of chitosan-denatured β-lactoglobulin microcapsules for potential food applications

Chitosan (CS) and β-lactoglobulin (βlg) double-wall coating was designed as a shell structure to achieve prolonged release of core material in the gastrointestinal tract (GI) for potential food applications. A model core material, brilliant blue (BB) dye, was incorporated into CS as the primary wall material, and subsequently, denatured βlg, a secondary wall material, was used to coat the outer layer. The strongest interaction occurred between 0.5% (w/v) βlg and 0.5% (w/v) CS at pH 5.5 ± 0.1, where the opposite charges of CS and βlg formed a complex, which is especially favourable in acidic beverage systems. Under simulated stomach conditions, a denatured-βlg coat resisted acid conditions and pepsin hydrolysis for 2 h. While mimicking small intestine conditions, βlg was degraded by pancreatin, causing the release of BB-loaded CS to the intestinal fluid at a constant rate. The sustained release of core material later in the GI tract provided an optimal absorption rate in the small intestine.     

Lipase-catalyzed production of pinolenic acid concentrate from pine nut oil using a recirculating packed bed reactor

Pinolenic acid (PLA) concentrate in fatty acid ethyl ester (FAEE) was efficiently produced from pine nut oil via lipase-catalyzed ethanolysis using a recirculating packed bed reactor (RPBR). The effects of reaction temperature, molar ratio, and residence time on the concentration of PLA were explored. Novozym 435 lipase from Candida antarctica showed less selectivity toward PLA esterified at the sn-3 position when temperature was increased from 45 to 55 °C. For the trials of molar ratio between 1: 50 and 1: 100 (pine nut oil to ethanol), there were no significant differences in the yield of PLA. Residence time of substrate in a RPBR affected significantly the PLA content as well as the yield of PLA. Optimal temperature, molar ratio (pine nut oil to ethanol), and residence time for production of PLA concentrate via lipase-catalyzed ethanolysis in a RPBR were 45 °C, 1: 50, and 3 min, respectively. Under these conditions, the maximal PLA content (36.1 mol%) in the concentrate was obtained during the initial 10 min of reaction.     

Water condensation behavior on the surface of a network of superhydrophobic carbon fibers with high-aspect-ratio nanostructures

We have explored the condensation behavior of water on a superhydrophobic carbon fiber (CF) network with high-aspect-ratio hair-like nanostructures. Nanostructures ranging from nanopillars to hairy shapes were grown on CFs by preferential oxygen plasma etching. Superhydrophobic CF surfaces were achieved by application of a hydrophobic siloxane-based hydrocarbon coating, which increased the water contact angle from 147° to 163° and decreased the contact angle hysteresis from 71° to below 5°, sufficient to cause droplet roll-off from the surface. Water droplet nucleation and growth on the superhydrophobic CF were significantly retarded due to the high-aspect-ratio nanostructures under super-saturated vapor conditions. CFs are observed to wet with condensation between fibers of the pristine surface under super-saturated vapor conditions, which eventually leads to flooding. However, dropwise condensation became dominant in the superhydrophobic CF network, allowing for easy removal of the condensed droplets, which largely allowed the interstitial spaces of the fiber network to remain dry. It is implied that superhydrophobic CF can provide a passage for vapor or gas flow in wet environments such as a gas diffusion layer requiring the effective water removal in the operation of proton exchange membrane fuel cell.     

Separation of N2/SF6 binary mixtures using polyethersulfone (PESf) hollow fiber membrane

PESf hollow fiber membrane was used to recover sulfur hexafluoride (SF₆) from N₂/SF₆ binary mixture gas. To fabricate a hollow fiber membrane, a dry-wet phase inversion method was used. Fiber was post-treated by methanol to increase permeance. Fabricated membrane was characterized by scanning electron microscopy (SEM) and N₂, SF₆ single gas permeation according to temperature and pressure difference. Using N₂/SF₆ binary mixture gas (10 vol% of SF₆), we checked the separation of mixture gas in a manufactured single module according to temperature, pressure difference, and retentate flow rate. The highest SF₆ purity in recovered gas was 50.4 vol% when the pressure difference, temperature, and stage cut was highest in experimental conditions, but the recovery ratio marked the lowest value.     

Relationships between crystal structure and electrical properties of Li0.055[Agx(K0.5Na0.5)1−x]0.945(Nb1−yTay)O3 ceramics

Electrical properties of perovskite Li_0.055[Ag_x(K_0.5Na_0.5)_1?x]_0.945(Nb_1?yTa_y)O₃ (0.00 ≤ x ≤ 0.04, 0.01 ≤ y ≤ 0.09) ceramics were investigated based on the structural characteristics. A morphotropic phase boundary (MPB) between orthorhombic and tetragonal phase was detected through the entire range of compositions. With increasing of Ta⁵⁺ content, the dielectric constant (?_r), piezoelectric coefficient (d₃₃) and electromechanical coupling factor (k_p) of Li_0.055(K_0.5Na_0.5)_0.945(Nb_1?yTa_y)O₃ ceramics were increased up to y = 0.07 and then decreased, while mechanical quality factor (Q_m) was increased. However, the ?_r, d₃₃, k_p and Q_m of Li_0.055[Ag_x(K_0.5Na_0.5)_1?x]_0.945(Nb_0.07Ta_0.03)O₃ ceramics were not changed remarkably with Ag⁺ content. The dependence of temperature coefficient of k_p (TCk_p) on the oxygen octahedral distortion was also discussed by Raman-active vibrations modes.