An Engineered Cholesterol Oxidase Catalyses Enantioselective Oxidation of Non-steroidal Secondary Alcohols

The enantioselective oxidation of 2° alcohols to ketones is an important reaction in synthetic chemistry, especially if it can be achieved using O₂-driven alcohol oxidases under mild reaction conditions. However to date, oxidation of secondary alcohols using alcohol oxidases has focused on activated benzylic or allylic substrates, with unactivated secondary alcohols showing poor activity. Here we show that cholesterol oxidase (EC 1.1.3.6) could be engineered for activity towards a range of aliphatic, cyclic, acyclic, allylic and benzylic secondary alcohols. Additionally, since the variants demonstrated high (S)-selectivity, deracemisation reactions were performed in the presence of ammonia borane to obtain enantiopure (R)-alcohols.     

The Columnar-to-Equiaxed Transition in Melt Pools During Laser Powder Bed Fusion of M2 Steel

Metallurgical and Materials Transactions A - This work integrates experimental and numerical methods to determine the process conditions under which the columnar-to-equiaxed transition (CET)...     

Comparison of primary and secondary aminosilance coupling agents in anhuydride-curde epoxy fiberglass composites

Fourier transform infrared spectroscopy (FT-IR) has been utilized to investigate the interfacial chemical bonding at the interfaces of the aminosilanes and the nedic methyl anhydiride cured epoxy matrix in fiber-reinforced composites. It is found that the nedic methyl anhydride can react with γ-aminopropyltriethoxysilane (APS) and N-methylaminoproplytrimethoxysilane (MAPS). In comparing the relative reactivities of two coupling agents to the epoxy resin, the secondary aminosilance has a higher reactivity than the primary aminosilance. An elevated temperature is required for the copolymerization to take place between the silane and the epoxy resin. The results indicate that covalent bonds form at the coupling agents. The molecular structure of the interface in MAPS treated fiberglass reinforced composites is different from that of the APS treated fiber composites. In addition, an accelerated copolymerization initiated by the coupling agent treated surface is also found in the resin interphase which may be important in determining the mechanical properties of the composites.     

Silicon-29 solid-state nuclear magnetic resonance spectroscopy of composite interfaces

The types of structures and bonds that are formed with silicons in the composite interface were studied using ²⁹Si cross-polarization/magic angle sample spinning (CP/MAS) nuclear magnetic resonance spectroscopy (NMR). The change in mobility of silane coupling agent bonded to silica, as compared with bulk hydrolyzed silane coupling agent, can be monitored by the change in line width and the shift of resonances to higher fields, as well as by the change in the silicon-proton cross-polarization time T_SiH. In the silane coupling agent-matrix resin interface, the T_SiH values reflect the change in mobility as a function of the concentration and degree of hydrolysis of the silane coupling agent. It has been demonstrated that quantitative measurements of T_SiH can be used to investigate relative mobilities.     

Investigation of the Sharkskin melt instability using optical Fourier analysis

An optical method allowing the characterization of melt flow instabilities typically occurring during an extrusion process of polymers and polymer compounds is presented. It is based on a camera-acquired image of the extruded compound with a reference length scale. Application of image processing and transformation of the calibrated image to the frequency domain yields the magnitude spectrum of the instability. The effectiveness of the before mentioned approach is shown on Styrene-butadiene rubber (SBR) compounds, covering a wide range of silica filler content, extruded through a Göttfert capillary rheometer. The results of the image-based analysis are compared with the results from the sharkskin option, a series of highly sensitive pressure transducers installed inside the rheometer. A simplified version of the code used to produce the optical analysis results is included as supplementary material. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48806.     

Characterisation of CYP102A25 from Bacillus marmarensis and CYP102A26 from Pontibacillus halophilus: P450 Homologues of BM3 with Preference towards Hydroxylation of Medium‐Chain Fatty Acids

Cytochrome P450 monooxygenases are highly desired biocatalysts owing to their ability to catalyse a wide variety of chemically challenging C?H activation reactions. The CYP102A subfamily of enzymes are natural catalytically self‐sufficient proteins consisting of a haem and FMN‐FAD reductase domain fused in a single‐component system. They catalyse the oxygenation of saturated and unsaturated fatty acids to produce primarily ω?1, ω?2 and ω?3 hydroxy acids. These monooxygenases have potential applications in biotechnology; however, their substrate range is still limited and there is a continued need to add diversity to this class of biocatalysts. Herein, we present the characterisation of two new members of this class of enzymes, CYP102A25 (BMar) from Bacillus marmarensis and CYP102A26 (PHal) from Pontibacillus halophilus, both of which express readily in a recombinant bacterial host. BMar exhibits the highest activity toward myristic acid and shows moderate activity towards unsaturated fatty acids. PHal exhibits broader activity towards mid‐chain‐saturated (C₁₄–C₁₈) and unsaturated fatty acids. Furthermore, PHal shows good regioselectivity for the hydroxylation of myristic acid, targeting the ω?2 position for C?H activation.     

Applications of one-cycle control to improve the interconnection of a solid oxide fuel cell and electric power system with a dynamic load

Adding distributed generation (DG) is a desirable strategy for providing highly efficient and environmentally benign services for electric power, heating, and cooling. The interface between a solid oxide fuel cell (SOFC), typical loads, and the electrical grid is simulated in Matlab/Simulink and analyzed to assess the interactions between DG and the electrical grid. A commercial building load profile is measured during both steady-state and transient conditions. The load data are combined with the following models that are designed to account for physical features: a One-Cycle Control grid-connected inverter, a One-Cycle Control active power filter, an SOFC, and capacitor storage. High penetration of DG without any power filter increases the percentage of undesirable harmonics provided by the grid, but combined use of an inverter and active power filter allows the DG system interconnection to improve the grid tie-line flow by lowering total harmonic distortion and increasing the power factor to unity.     

Corrosion of aluminium in the aqueous chemical environment of a loss-of-coolant accident at a nuclear power plant

Aluminium corrosion is a significant concern in the aqueous chemical environment of the reactor containment building following a hypothetical loss-of-coolant accident (LOCA) at a nuclear power plant. Aluminium corrosion may lead to the formation of precipitates that can, in combination with insulation debris, block the recirculation sump screens. This study investigated aluminium corrosion experimentally at both bench and pilot scale under conditions representative of several types of nuclear power plants. Evidence of corrosion was determined using aqueous concentrations measured with inductively-coupled plasma (ICP) spectrometry and surface examinations using scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), X-ray photoelectron spectrometry (XPS), X-ray fluorescence (XRF), and X-ray diffraction (XRD). Corrosion proceeded slowly at pH near 7, but more rapidly at higher pH when the representative pipe insulation material was fibreglass. However, when calcium silicate pipe insulation was introduced into the system, corrosion became insignificant even at pH values near 10. Experimental evidence indicates that the calcium silicate insulation released a significant amount of silicate to the solution. Silicate formed a passivation layer composed of Al₂OSiO₄ with a thickness of more than 10 nm, and this layer effectively inhibited corrosion.