In Vitro Phosphorylation Does not Influence the Aggregation Kinetics of WT α-Synuclein in Contrast to Its Phosphorylation Mutants

The aggregation of alpha-synuclein (α-SYN) into fibrils is characteristic for several neurodegenerative diseases, including Parkinson’s disease (PD). Ninety percent of α-SYN deposited in Lewy Bodies, a pathological hallmark of PD, is phosphorylated on serine129. α-SYN can also be phosphorylated on tyrosine125, which is believed to regulate the membrane binding capacity and thus possibly its normal function. A better understanding of the effect of phosphorylation on the aggregation of α-SYN might shed light on its role in the pathogenesis of PD. In this study we compare the aggregation properties of WT α-SYN with the phospho-dead and phospho-mimic mutants S129A, S129D, Y125F and Y125E and in vitro phosphorylated α-SYN using turbidity, thioflavin T and circular dichroism measurements as well as transmission electron microscopy. We show that the mutants S129A and S129D behave similarly compared to wild type (WT) α-SYN, while the mutants Y125F and Y125E fibrillate significantly slower, although all mutants form fibrillar structures similar to the WT protein. In contrast, in vitro phosphorylation of α-SYN on either S129 or Y125 does not significantly affect the fibrillization kinetics. Moreover, FK506 binding proteins (FKBPs), enzymes with peptidyl-prolyl cis-trans isomerase activity, still accelerate the aggregation of phosphorylated α-SYN in vitro, as was shown previously for WT α-SYN. In conclusion, our results illustrate that phosphorylation mutants can display different aggregation properties compared to the more biologically relevant phosphorylated form of α-SYN.     

Highly Dense,Transparent α‐Al2O3 Ceramics From Ultrafine Nanoparticles Via a Standard SPS Sintering

Using discrete, ultrafine alumina, highly dense transparent (71% real in‐line transmission, RIT, λ = 640 nm) ceramics were achieved with grain size as small as 260 nm using standard SPS sintering. We show that use of La³⁺ as a dopant greatly reduces sensitivity to the sintering temperatures. Transparent alumina were achieved in a large range of sintering temperatures, 1140°C < T < 1200°C, thus providing better reliability and flexibility into the fabrication of large sintered transparent ceramic bodies.     

Pressurized honeycombs as soft-actuators: a theoretical study

The seed capsule of Delosperma nakurense is a remarkable example of a natural hygromorph, which unfolds its protecting valves upon wetting to expose its seeds. The beautiful mechanism responsible for this motion is generated by a specialized organ based on an anisotropic cellular tissue filled with a highly swelling material. Inspired by this system, we study the mechanics of a diamond honeycomb internally pressurized by a fluid phase. Numerical homogenization by means of iterative finite-element (FE) simulations is adapted to the case of cellular materials filled with a variable pressure fluid phase. Like its biological counterpart, it is shown that the material architecture controls and guides the otherwise unspecific isotropic expansion of the fluid. Deformations up to twice the original dimensions can be achieved by simply setting the value of input pressure. In turn, these deformations cause a marked change of the honeycomb geometry and hence promote a stiffening of the material along the weak direction. To understand the mechanism further, we also developed a micromechanical model based on the Born model for crystal elasticity to find an explicit relation between honeycomb geometry, swelling eigenstrains and elastic properties. The micromechanical model is in good qualitative agreement with the FE simulations. Moreover, we also provide the force-stroke characteristics of a soft actuator based on the pressurized anisotropic honeycomb and show how the internal pressure has a nonlinear effect which can result in negative values of the in-plane Poisson''s ratio. As nature shows in the case of the D. nakurense seed capsule, cellular materials can be used not only as low-weight structural materials, but also as simple but convenient actuating materials.     

Effect of Cloisite® 30B on the Diffusion of Irganox 1076 in HDPE

The diffusion of a thermal stabilizer, Irganox 1076, is studied both in pure high‐density polyethylene (HDPE) and HDPE matrix filled with 1 wt% of Cloisite® 30B. The diffusion experiments are carried out by using the Roe method formed by a stack of several polymer films of 120 ± 01 μm in thickness. In this study, a simple method is used to measure the diffusion coefficient, with the aid of Fourier Transform InfraRed spectroscopy without any extraction or refining steps in the analysis. The diffusion coefficient (D_p) of both materials are obtained in the temperature range 80–100°C using the second Fick's law. By applying the Arrhenius equation to the calculated D_p coefficients, an estimation of activation energies of the diffusion process is also achieved. The results indicate that the diffusion coefficient of Irganox 1076 in HDPE has been decreased by adding 1% of Cloisite® 30B.     

Experimental determination and modelling of water desorption isotherms of tropical woods: afzelia, ebony, iroko, moabi and obeche

Desorption isotherms of Afzelia, Ebony, Iroko, Moabi and Obeche have been experimentally found at 20, 30, 40, 50 and 60 °C by use of the salt method for a range of water activities from 0.06 to 0.97. The sorption capacity of these woods increases with the temperature for a given water activity. The experimental curves have been simulated by the GAB and BET models. The GAB model enables the representation of the whole desorption isotherms. Meanwhile, the BET model ensures a better representation of the experimental results for water activity lower than 0.35 with mean relative deviation of 2.9, 2.1, 1.3, 3.2 and 3.3% for respectively Afzelia, Ebony, Iroko, Moabi and Obecheand a better estimation of the water content corresponding to monolayer saturation.     

Potential m-calpain substrates during myoblast fusion

Many studies have demonstrated that m-calpain was implicated in cell membrane reorganization-related phenomena during fusion via a regulation by calpastatin, the specific Ca2+-dependent proteolytic inhibitor. However, the real biological role of this protease is unclear because many targeted proteins are still unknown. Using different digestion experiments we have demonstrated that desmin, vimentin, talin, and fibronectin represent very good substrates for this proteinase capable of cleaving them in fragments which are immediately degraded by other enzymatic systems. Concerning intermediate filaments, we showed that during the phenomenon of fusion, the amount of desmin was significantly reduced while the concentration of vimentin presented a steady level. On the other hand, we have conducted biological assays on cultured myoblasts supplemented by exogenous factors such as calpain inhibitors or antisense oligonucleotides capable of stimulating or inhibiting m-calpain activity. The effect of such factors on fusion and concomitantly on the targeted substrates was analyzed and quantified. When m-calpain activity and myoblast fusion were prevented by addition of calpain inhibitors entering the cells, the amounts of desmin, talin, and fibronectin were increased, whereas the amount of vimentin was unchanged. Using antisense strategy, similar results were obtained. In addition, when the phenomenon of fusion was enhanced by preventing calpastatin synthesis, the amounts of desmin, talin, and fibronectin were significantly reduced. Taken together, these results support the hypothesis that m-calpain is involved in myoblast fusion by cleaving certain proteins identified here. This cleavage could modify membrane and cytoskeleton organization for the myoblasts to fuse.     

The influence of aluminium on the overall properties of SnO<Subscript>2</Subscript>-based varistors

The influence of aluminium on the development of the microstructure and on the electrical behaviour of the SnO₂ · Co₃O₄ · Nb₂O₅ typical varistor system was studied. Two sources of Al were used, alumina (Al₂O₃) and boehmite (AlO(OH)). The microstructural features were characterised with scanning (SEM) and transmission (TEM) electron microscopies. The different phases present in the studied samples were also studied with XRD, EDS and electron diffraction patterns of selected areas (SAED). Particles containing Sn, Co, Al, and O were unveiled with TEM. Impedance spectroscopy measurements and current density versus electric field characteristics revealed superior electrical properties for samples with AlO(OH). The higher non-linearity (α = 19) was achieved with the addition of 0.1% mol of boehmite. The influence of the secondary phases on the electrical properties is also addressed in this work.     

Poly(di(ω-alkylphenyl)stannane)s

Poly(di(ω-alkylphenyl)stannane)s, [Sn(C _n H_2n Ph)₂] _m with n = 2–4, and a copolymer of di(3-propylphenyl)stannane and dibutylstannane of weight-average molar masses of 2–8 · 10⁴ g/mol were synthesized by dehydropolymerization of stannanes of the composition H₂SnR₂ using Wilkinson’s catalyst [RhCl(PPh₃)₃]. At least two methylene groups were required as spacers between the phenyl group and the tin atom for polymerization to occur. The polystannanes were characterized by, among other techniques, ¹H, ¹³C and ¹¹⁹Sn NMR spectroscopy, thermal analysis and X-ray diffraction. The polymers featured properties different from those of the corresponding poly(dialkylstannane)s. Specifically, the [Sn(C _n H_2n Ph)₂] _m family displayed glass transitions at remarkably low temperatures, down to ca. −50 °C, and a lower value for a copolymer (−68 °C). Polymers [Sn(C_nH_2nPh)₂]_m with n = 2 and 3 and a copolymer at room temperature were of a gel-like concistence, which enabled facile orientation with shear forces. Finally, the temperature-dependent electrical conductivity was determined for poly(di(3-propylphenyl)stannane), which followed the law of typical semiconductors, with an activation energy for conduction of 0.12 eV.     

Kinetics and Mechanism of the Water–Gas Shift Reaction Over Platinum Supported Catalysts

A dual-site reaction mechanism is proposed for Pt based water–gas shift catalysts. The sorption equilibrium parameters are evaluated in detail to validate their physical significance. The values of the van ‘t Hoff parameters for CO and H₂ correspond to those for chemisorption on platinum. The sorption parameters of H₂O and CO₂ on the supports have been quantitatively determined from temperature-programmed desorption experiments and have been compared to the values obtained from the kinetic study. Finally the proposed model is able to explain the different activities between the two catalysts.     

Le projet européen PRIME: protection de la vie privée et gestion des identités pour l’Europe

This paper presents an overview of the European project PRIME, with its objectives, main research issues and expected results.