Distance measurement between Tyr10 and Met35 in amyloid beta by site-directed spin-labeling ESR spectroscopy: implications for the stronger neurotoxicity of Abeta42 than Abeta40

The neurotoxicity of the 42-mer and 40-mer amyloid beta peptides (Abeta42 and Abeta40) is closely related to the radicalization at both Tyr10 and Met35. Abeta42 is more neurotoxic than Abeta40. Our previous structural analyses of Abeta42 suggested that Tyr10 and Met35 are brought closer together by the turn at positions 22 and 23, and the S-oxidized radical cation at position 35, which is the ultimate toxic radical species, can be produced effectively through oxidation by the phenoxy radical at position 10. To verify this idea, their separation was measured by site-directed spin labeling (MTSSL) by using ESR spectroscopy. Among the three kinds of Abeta42 derivatives, which are doubly or singly spin-labeled at position 10 and 35, only 10,35-MTSSL-Abeta42 showed a clear dipole coupling in continuous-wave ESR; this suggests that the intramolecular spin labels at position 10 and 35 in Abeta42 are located within approximately 15 A. In contrast, 10,35-MTSSL-Abeta40 did not give such signals. The distance between Tyr10 and Met35 in 10,35-MTSSL-Abeta40, which was successfully measured by pulsed ESR spectroscopy was 30 A long. The difference in the distance between Abeta42 and Abeta40 could explain in part the stronger neurotoxicity of Abeta42 compared to Abeta40.     

Electrospun curcumin/polycaprolactone/copolymer F-108 fibers as a new therapy for wound healing

The application of fibers associated with drugs is a promising alternative to meet the clinical needs of tissue repair. Curcumin exhibits great cicatricial potential because it has numerous pharmacological properties. This research aimed to produce fibers of polycaprolactone and copolymer F-108 associated with curcumin and to evaluate in vivo their action on the process of wound healing. The fibers were produced by electrospinning technique and characterized by scanning electron microscopy (SEM), X-ray diffractometry (XRD), and fluorescence microscopy. They were applied in cutaneous wounds of rats for the analysis of photoacoustic permeation and histological study. The characterization showed that the electrospinning allowed the preparation of homogeneous material with curcumin. The fibers benefited healing of the wounds and allowed the permeation of curcumin at all stages. The use of PCL/F-108 fibers allowed the elaboration of a new curcumin delivery system, improving its bioavailability and action in the healing of excisional wound. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48415.     

Simulation of mesophase formation of rodlike molecule,imogolite

Summary The process of mesophase formation of rodlike molecule, imogolite, was simulated by comparing the distance distribution function computed from models with that obtained by the Fourier-transformation of small angle X-ray scattering data. In the initial state below A-point (defined as a starting point of mesophase formation), imogolite molecules assemble into loosely packed hexagonal shape with their ends aligned in a line. The columns composed of hexagonal packing are arrnaged side by side to form raft-like sheets near the A-point and finally form mesophase above A-point.     

Practical Continuous‐Flow Controlled/Living Anionic Polymerization

A continuous‐flow reaction system was developed, allowing flow conditions of the entire system to be maintained at a predetermined constant level, which is one of the most significant factors for successful industrial application. Controlled/living anionic polymerization was selected as a model reaction since the characteristics of its polymer products, molecular weights, and molecular weight distributions are highly susceptible to changes in the relative flow rates of a monomer and initiator solutions. In flow microreactors, controlled/living anionic polymerization of styrene in tetrahydrofuran (THF)/hexane initiated by THF‐diluted n‐butyllithium (n‐BuLi) was examined. Poly(styrenes) of larger molecule sizes such as Mn > 15 000 were successfully synthesized. After continuous operation for four hours, ca. 0.5 kg of the polymer was readily produced with narrow molecular weight distribution, demonstrating the applicability of this continuous‐flow system for controlled/living anionic polymerization on considerably large scale with a view to its industrial usage in the future.     

Robustness of Zero Crossing Estimator

Zero crossing (ZC) statistic is the number of zero crossings observed in a time series. The expected value of the ZC specifies the first‐order autocorrelation of the processes. Hence, we can estimate the autocorrelation by using the ZC estimator. The asymptotic consistency and normality of the ZC estimator for scalar Gaussian processes are already discussed in 1980. In this article, first, we derive the joint asymptotic distribution of the ZC estimator for ellipsoidal processes. Next, we show the variance of the ZC estimator does not attain the Cramer–Rao lower bound (CRLB). However, it is shown that the ZC estimator has robustness when the process is contaminated by an outlier. In contrast with this, we observe that the quasi‐maximum likelihood estimator (QMLE) attains the CRLB. However, we can see that QMLE is sensitive for the outlier.     

Novel Route to Propylene Carbonate: Selective Synthesis from Propylene Glycol and Carbon Dioxide

High surface area zirconium phosphate in an amorphous phase exhibits high activities for water-related reactions such as hydrolysis of ethyl acetate and esterification of acetic acid with ethanol. The zirconium phosphate is insoluble during the reaction, is recoverable by simple filtration, and can be reused at least five times without any treatment.     

A multiscale simulation of polymer processing using parameter-based bridging in melt rheology

To investigate the effect of molecular structure on macroscopic flow behavior of polymeric liquid, attempts have been made to embed the microscopic information into the flow simulation. Constitutive equation based on the theory of polymer dynamics is ideal but the theory is still under development. The CONNFFESSIT approach (where microscopic simulation is embedded into calculation grid in macroscopic simulation) is another promising direction but the computational cost is not practical yet. In this study, we propose another simple method using parameter-based bridging where the parameters for phenomenological constitutive equations in macroscopic flow simulation are obtained from coarse-grained molecular simulation. As an example, we performed a simulation of injection molding and examined the effect of molecular weight on warpage of the molded product. We used the primitive chain network simulation to calculate linear viscoelasticity of linear monodispersed polystyrenes from molecular weight. The obtained linear viscoelasticity was converted into the relaxation spectrum and into the flow curve to be used in the macroscopic simulations. From the flow curve, the parameters of an inelastic non-Newtonian constitutive equation were obtained and used for the simulation of filling process. The relaxation spectrum was used to calculate residual stress from the flow profile in the filling process. From the residual stress and thermal shrinkage, warpage of the product was obtained. For the examined thin plate product, significant change in the warpage direction was demonstrated according to the molecular weight of the material. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012