Soft polyurethanes treated by plasma immersion ion implantation: Structural and mechanical properties of the surface‐modified layer

The surfaces of soft polyurethanes (with elastic moduli of 7 and 50 MPa) treated by plasma immersion ion implantation were studied; the materials became hard and wrinkled. The characteristics of the modified surface (modulus, roughness, wave and fractal parameters, linear deformation) and the cross‐sectioned layer were studied in relation to the treatment regime and the modulus of the polymer. A hypothesis that the wrinkling was solely caused by thermal expansion was checked but rejected. The cross‐section of the treated material had a hard part of a certain thickness and a transition zone. The elastic modulus of the hard part was estimated by the finite element method. A comparison of the obtained thicknesses with calculations by TRIM software indicated that the latter gave underestimated results. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45983.     

Studies of Membrane Topology of Mitochondrial Cholesterol Hydroxylases CYPs 27A1 and 11A1

Mitochondrial cytochrome P450 enzymes (CYP or P450, EC 1.14.13.15) play an important role in metabolism of cholesterol. CYP27A1 hydroxylates cholesterol at position 27 and, thus, initiates cholesterol removal from many extrahepatic tissues. CYP11A1 is a steroidogenic P450 that converts cholesterol to pregnenolone, the first step in the biosynthesis of all steroid hormones. We utilized a new approach to study membrane topology of CYPs 27A1 and 11A1. This approach involves heterologous expression of membrane-bound P450 in E. coli, isolation of the P450-containing E. coli membranes, treatment of the membranes with protease, removal of the digested soluble portion and extraction of the membrane-associated peptides, which are then identified by mass spectrometry. By using this approach, we found four membrane-interacting peptides in CYP27A1, and two peptides in CYP11A1. Peptides in CYP27A1 represent a contiguous portion of the polypeptide chain (residues 210–251) corresponding to the putative F-G loop and adjacent portions of the F and G helices. Peptides in CYP11A1 are from the putative F-G loop (residues 218–225) and the C-terminal portion of the G helix (residues 238–250). This data is consistent with those obtained previously by us and others and provide new information about the membrane topology of CYPs 27A1 and 11A1.     

Improving glass transition temperature of unsaturated polyester thermosets: Conventional unsaturated polyester resins

Highly crosslinkable unsaturated polyester resins (UPR) have attracted many interests in the application as reinforced matrix materials. Here, we present a systematical study of the influence of different curing conditions and styrene concentrations on resin viscosity and dynamic-mechanical properties of the thermoset. The pure maleic Palapreg® P18-03 was selected as model UPR because of its broad industrial use. By applying newly developed thermal curing profiles (without thermal initiators) and by raising the styrene content, the T_g of the network could be increased up to 206/215°C (1/10 Hz). For the first time, a fast curable UPR based on propylene glycol and neopentyl glycol with a T_g of up to 215°C is described. A partial substitution of problematic styrene with methylmethacrylate, tert-butylacrylate, and maleic anhydride (MA) was studied as well. MA leads to significantly improved resin reactivity. A resin containing 42 wt% styrene and 8 wt% MA yields thermosets with remarkably improved mechanical properties and with a narrower glass transition range compared to the original P18-03.     

Trypsin Induced Degradation of Amyloid Fibrils

Proteolytic enzymes are known to be involved in the formation and degradation of various monomeric proteins, but the effect of proteases on the ordered protein aggregates, amyloid fibrils, which are considered to be extremely stable, remains poorly understood. In this work we study resistance to proteolytic degradation of lysozyme amyloid fibrils with two different types of morphology and beta-2-microglobulun amyloids. We showed that the proteolytic enzyme of the pancreas, trypsin, induced degradation of amyloid fibrils, and the mechanism of this process was qualitatively the same for all investigated amyloids. At the same time, we found a dependence of efficiency and rate of fibril degradation on the structure of the amyloid-forming protein as well as on the morphology and clustering of amyloid fibrils. It was assumed that the discovered relationship between fibrils structure and the efficiency of their degradation by trypsin can become the basis of a new express method for the analysis of amyloids polymorphism. Unexpectedly lower resistance of both types of lysozyme amyloids to trypsin exposure compared to the native monomeric protein (which is not susceptible to hydrolysis) was attributed to the higher availability of cleavage sites in studied fibrils. Another intriguing result of the work is that the cytotoxicity of amyloids treated with trypsin was not only failing to decline, but even increasing in the case of beta-2-microglobulin fibrils.     

Multi-wall carbon nanotubes coated with polyaniline

Multi-wall carbon nanotubes (CNT) were coated with protonated polyaniline (PANI) in situ during the polymerization of aniline. The content of CNT in the samples was 0-80 wt%. Uniform coating of CNT with PANI was observed with both scanning and transmission electron microscopy. An improvement in the thermal stability of the PANI in the composites was found by thermogravimetric analysis. FTIR and Raman spectra illustrate the presence of PANI in the composites; no interaction between PANI and CNT could be proved. The conductivity of PANI-coated CNT has been compared with the conductivity of the corresponding mixtures of PANI and CNT. At high CNT contents, it is not important if the PANI coating is protonated or not; the conductivity is similar in both cases, and it is determined by the CNT. Polyaniline reduces the contact resistance between the individual nanotubes. A maximum conductivity of 25.4 S cm⁻¹ has been found with PANI-coated CNT containing 70 wt% CNT. The wettability measurements show that CNT coated with protonated PANI are hydrophilic, the water contact angle being ∼40°, even at 60 wt% CNT in the composite. The specific surface area, determined by nitrogen adsorption, ranges from 20 m² g⁻¹ for protonated PANI to 56 m² g⁻¹ for neat CNT. The pore sizes and volumes have been determined by mercury porosimetry. The density measurements indicate that the compressed PANI-coated CNT are more compact compared with compressed mixtures of PANI and CNT. The relaxation and the growth of dimensions of the samples after the release of compression have been noted.     

Studies on surface activity of petroleum sulfonates prepared from extracts of solvent refining

Petroleum sulfonates with the active substance content from 21 to 32.5 % wt were prepared from four extracts of solvent refining by phenol and N-methylpyrrolidone (oil side streams II and III) in laboratory conditions. Their average molecular weight, composition, and surface activity were evaluated using a rotating drop test. The sulfonated products were characterized by NMR, IR spectroscopy, and HPLC methods.     

Relationship between land use composition and PM<Subscript>10</Subscript> concentrations in Iskandar Malaysia

Air pollution has always been a concern with increasing urbanization and poor land use planning adding to the problem. This study sets out to investigate the relationship between land use composition of an area and its ambient concentration of 10-μm-or-less particulate matter (PM₁₀). For this study, Iskandar Malaysia has been chosen as the study area. To compensate for the limited number of air quality monitoring stations in the study area, Terra MODIS aerosol optical depth Level 2 products are used to assess PM₁₀ concentration spatially. Land use data were developed from LANDSAT images used together with the land use database from the local authority. Finally, the relationship between land use composition and concentrations of PM₁₀ in the study area are explained using contour ternary plots. The plots show how different compositions of three major urban land uses (residential, commercial, industrial) in an area results in different concentration levels of PM₁₀. Concentrations of PM₁₀ are evidently more affected by commercial land use, followed by industrial land use. Hence, responsible authorities in Iskandar Malaysia could control or reduce air pollution in an area by planning a better land use composition.