Sequence of Polyurethane Ionomers Determinative for Core Structure of Surfactant–Copolymer Complexes

The core of micelles self-assembled from amphiphiles is hydrophobic and contains little water, whereas complex coacervate core micelles co-assembled from oppositely charged hydrophilic polymers have a hydrophilic core with a high water content. Co-assembly of ionic surfactants with ionic-neutral copolymers yields surfactant–copolymer complexes known to be capable of solubilizing both hydrophilic and hydrophobic cargo within the mixed core composed of a coacervate phase with polyelectrolyte-decorated surfactant micelles. Here we formed such complexes from asymmetric (PUI-A2) and symmetric (PUI-S2), sequence-controlled polyurethane ionomers and poly(N-methyl-2-vinylpyridinium iodide)₂₉-b-poly(ethylene oxide)₂₀₄ copolymers. The complexes with PUI-S2 were 1.3-fold larger in mass and 1.8-fold larger in radius of gyration than the PUI-A2 complexes. Small-angle X-ray scattering revealed differences in the packing of the similarly sized PUI micelles within the core of the complexes. The PUI-A2 micelles were arranged in a more ordered fashion and were spaced further apart from each other (10 nm vs. 6 nm) than the PUI-S2 micelles. Hence, this work shows that the monomer sequence of amphiphiles can be varied to alter the internal structure of surfactant–copolymer complexes. Since the structure of the micellar core may affect both the cargo loading and release, our findings suggest that these properties may be tuned through control of the monomer sequence of the micellar constituents.     

Flexible dielectric ZnO-doped reduced graphene oxide bionanocomposites from solution blending for potential application in bio-related devices

Biocompatible materials with high dielectric constant and low dielectric loss have applications in bio-related electronic devices. Development of flexible materials with those properties is still a challenge. In this work, electrospun membranes and films are prepared from poly(vinyl alcohol) (PVA) and chitosan (CS) solutions, incorporated with a reduced graphene oxide-zinc oxide composite (rGO-ZnO). Blending CS with flexible PVA favors electrospinnability and mechanical properties. ZnO contributes to hinder agglomeration of conductive rGO sheets. The structural, mechanical, dielectric and electrical properties of the hybrid materials are investigated. Infrared spectroscopy reveals interaction between the filler and the polymeric components. For mats and films, the increase in rGO-ZnO content leads to lower crystallinity. The Young's modulus and stress at break values increase with increasing rGO-ZnO content. High dielectric constants (ε' = 132 to ε' = 166, at 10³ Hz), associated with low dielectric loss factor (tan δ = 0.02), are determined for the PVA/CS/rGO-ZnO films.     

In Silico Characterization of Masitinib Interaction with SARS-CoV-2 Main Protease

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection continues to be a global health problem. Despite the current implementation of COVID-19 vaccination schedules, identifying effective antiviral drug treatments for this disease continues to be a priority. A recent study showed that masitinib (MST), a tyrosine kinase inhibitor, blocks the proteolytic activity of SARS-CoV-2 main protease (M^pro). Although MST is a potential candidate for COVID-19 treatment, a comprehensive analysis of its interaction with M^pro has not been done. In this work, we performed molecular dynamics simulations of the MST-M^pro complex crystal structure. The effect of the protonation states of M^pro H163 residue and MST titratable groups were studied. Furthermore, we identified the MST substituents and M^pro mutations that affect the stability of the complex. Our results provide valuable insights into the design of new MST analogs as potential treatments for COVID-19.     

Protein Misfolding and Aggregation: The Relatedness between Parkinson’s Disease and Hepatic Endoplasmic Reticulum Storage Disorders

Dysfunction of cellular homeostasis can lead to misfolding of proteins thus acquiring conformations prone to polymerization into pathological aggregates. This process is associated with several disorders, including neurodegenerative diseases, such as Parkinson’s disease (PD), and endoplasmic reticulum storage disorders (ERSDs), like alpha-1-antitrypsin deficiency (AATD) and hereditary hypofibrinogenemia with hepatic storage (HHHS). Given the shared pathophysiological mechanisms involved in such conditions, it is necessary to deepen our understanding of the basic principles of misfolding and aggregation akin to these diseases which, although heterogeneous in symptomatology, present similarities that could lead to potential mutual treatments. Here, we review: (i) the pathological bases leading to misfolding and aggregation of proteins involved in PD, AATD, and HHHS: alpha-synuclein, alpha-1-antitrypsin, and fibrinogen, respectively, (ii) the evidence linking each protein aggregation to the stress mechanisms occurring in the endoplasmic reticulum (ER) of each pathology, (iii) a comparison of the mechanisms related to dysfunction of proteostasis and regulation of homeostasis between the diseases (such as the unfolded protein response and/or autophagy), (iv) and clinical perspectives regarding possible common treatments focused on improving the defensive responses to protein aggregation for diseases as different as PD, and ERSDs.     

Temperature sensor based on the power reflected by a Bragg grating in a tapered fiber

We present a temperature sensor based on two chirped gratings made in optical fibers tapered by fusion. One of the gratings has a metallic shielding and acts as sensor element, whereas the second grating provides a reference signal. The sensor is interrogated by measuring the power reflected by the two gratings, and the system has an accuracy of 0.05 degrees C over a linear operation range of more than 10 degrees C that can be adjusted in the fabrication process.     

Optical system design for orthosymplectic transformations in phase space

On the basis of a matrix formalism, we analyze the paraxial optical systems composed by generalized lenses and fixed free-space intervals, suitable for orthosymplectic transformations in phase space. Flexible configurations to perform the attractive operations for optical information processing such as image rotation, separable fractional Fourier transformation, and twisting for different parameters are proposed.     

Growth morphology and spectroscopy of multiwall carbon nanotubes synthesized by pyrolysis of iron phthalocyanine

Carbon nanotubes (CNTs) were synthesized by Chemical Vapor Deposition (CVD) from the pyrolytic decomposition of Iron Phthalocyanine (FePc) molecules, on SiO2/Si(111) substrates in the presence of a hydrogen flow. FePc molecules contribute simultaneously both to the formation of the precursor Fe nanoparticles and also as a Carbon source. Different experimental conditions were examined. Samples were characterized by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, and inverse photoemission. The resulting samples are highly oriented multiwall carbon nanotubes films, with heights in the range between: 4 and 20 microm. The tubes diameter is strongly dependent on growth temperature. Our experimental results show evidence of a transition in the growth mechanism, from a tip growth to a base growth mode, as the decomposition temperature is increased. Preliminary spectroscopic measurements performed on these MWCNTs, show the unoccupied density of states has several resonances close to Fermi level, related both to the graphene electronic structure and the formation of the tube.     

A new approach to the calculation of cross-section deformation modes in the framework of generalized beam theory

This paper presents a new and general approach for the calculation of cross-section deformation modes in thin-walled beams, to be used in the framework of generalized beam theory (GBT). The proposed approach subdivides and hierarchizes the cross-section deformation modes by employing several kinematic hypotheses. This makes it possible to discard a priori specific types of deformation modes and consequently reduce the number of cross-section degrees-of-freedom. The approach is applicable to arbitrary (with open and closed parts) polygonal cross-sections with external and internal constraints and allows for the a posteriori inclusion of particular deformation modes (e.g., shear deformation modes in a part of the cross-section). Although only GBT applications are dealt with, the deformation modes obtained may be straightforwardly incorporated in other thin-walled beam formulations that include cross-section deformation.     

Dielectric and piezoelectric characterization of PSZT–BT ceramics for capacitor applications

The ceramic compositions (1 − x)Pb_0.9875Sr_0.0125(Zr_0.53Ti_0.47)O₃ –xBaTiO₃ where x = 0.2, 0.4, 0.6 and 0.8, fabricated through solid state reaction method were investigated for phase formation, microstructure, density, dielectric and piezoelectric properties. The X-ray diffraction patterns indicated that introduction of BaTiO₃ in isovalent donor Sr modified PZT lattice, diminished the tetragonality. All the specimens were homogenous in nature due to the coarse grains of BaTiO₃, which had undergone inter-granular growth and were homogeneously distributed within the PSZT–BT lattice. Introduction of BaTiO₃ in PSZT perovskite lattice resulted in enhanced grain growth till x = 0.6 (2.03 μm). Dielectric properties (ε_RT, Tanδ and T _c) were influenced by both BaTiO₃ and Sr. The maximum ε_RT = 1588 and ε_Tc = 10478 were found in 0.2PSZT–0.8BT ceramic system. The optimum dielectric permittivity at room temperature with a low Curie transition temperature was found in 0.2PSZT–0.8BT composition. Piezoelectric properties are very sensitive to isovalent substitutions, where isovalent donor Sr modification and BT concentrations in PZT, affected the piezoelectric properties (k _p and d ₃₃) in the ceramic system. Thus, the series PSZT–BT compositions could be ideal candidates for capacitors and suitable sensor applications.