Self-sufficient Cytochrome P450s and their potential applications in biotechnology

Cytochrome P450s(CYPs) are ubiquitously found in all kingdoms of life, playing important role in various biosynthetic pathways as well as degradative pathways; accordingly find applications in a vast variety of areas from organic synthesis and drug metabolite production to modification of biomaterials and bioremediation.Significantly, CYPs catalyze chemically challenging C—H and C—C activation reactions using a reactive high-valent iron-oxo intermediate generated upon dioxygen activation at their heme center,while the other oxygen atom is reduced to the level of water by electrons provided through a reductase partner protein.Self-sufficient CYPs, encoding their heme domain and reductase protein in a single polypeptide, facilitate increased catalytic efficiency and render a less complicated system to work with.The self-sufficient CYP enzyme from CYP102A family(CYP102A1, BM3) is among the earliest and most-investigated model enzymes for mechanistic and structural studies as well as for biotechnological applications.An increasing number of self-sufficient CYPs from the same CYP102 family and from other families have also been reported in last decade.In this review, we introduce chemistry and biology of CYPs, followed by an overview of the characteristics of self-sufficient CYPs and representative reactions.Enzyme engineering efforts leading to novel self-sufficient CYP variants that can catalyze synthetically useful natural and non-natural(nature-mimicking) reactions are highlighted.Lastly, the strategy and efforts that aim to circumvent the challenges for improved thermostability, regio-and enantioselectivity,and total turnover number; associated with practical use of self-sufficient CYPs are reviewed.     

Preparation of poly(methyl methacrylate-co-ethylene glycol dimethacrylate-co-glycidyl methacrylate) walled thermochromic microcapsules and their application to cotton fabrics

This study focused on fabrication of the thermochromic microcapsules and their application to the cotton fabric. In this study, thermochromic systems composed of crystal violet lactone, bisphenol A, and 1-tetradecanol were prepared and microencapsulated by emulsion polymerization method in poly(methyl methacrylate-co-ethylene glycol dimethacrylate-co-glycidyl methacrylate) wall. The microcapsules were analyzed by Fourier transform infrared spectroscopy, scanning electron microscope, transmission electron microscope, differential scanning calorimetry, and thermogravimetric analysis. Their thermoregulating property was tested by T-history test. The results revealed that microcapsules with smooth surfaces, core–shell structured, and spherical shape were successfully produced. The latent heat storage capacity of the microcapsules decreased from 202 J g⁻¹ to 167 J g⁻¹ when their shell/core ratio changed from 0.5/1 to 2/1. Microcapsules were adequately had sufficient thermal resistance to the temperatures they will encounter during their application to textile products and their usage. According to the UV–visible spectroscopy analysis and color measurements, the microcapsules exhibited reversible color change from blue to colorless and vice versa. Besides, the microcapsule impregnated fabric was able to absorb latent heat energy of 21.79 J g⁻¹ at around 35 °C and had cooling effect. According to the colorimetric parameters, the fabric was at blue color at room temperature and became colorless when heated to the temperature above the melting point of thermochromic system. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48815.     

Preparation of Porous Ca10(PO4)6(OH)2 and β-Ca3(PO4)2 Bioceramics

Submicrometer-sized, pure calcium hydroxyapatite (HA, (Ca₁₀(PO₄)₆(OH)₂)) and β-tricalcium phosphate (β-TCP, Ca₃(PO₄)₂) bioceramic powders, that have been synthesized via chemical precipitation techniques, were used in the preparation of aqueous slurries that contained methyl cellulose to manufacture porous (70%–95% porosity) HA or β-TCP ceramics. The pore sizes in HA bioceramics of this study were 200–400 μm, whereas those of β-TCP bioceramics were 100–300 μm. The pore morphology and total porosity of the HA and β-TCP samples were investigated via scanning electron microscopy, water absorption, and computerized tomography.     

The functional importance of Leu15 of human epidermal growth factor in receptor binding and activation

The biological importance of Leu15 of epidermal growth factor(EGF) is suggested by its conservation through evolution, itscritical location in the domain–domain interface of EGFand its close proximity to Arg41, a residue that is crucialfor receptor binding and activation. Mutagenesis of Leu15 ofhuman EGF (hEGF) was employed to examine the role of this residuein the ligand-receptor interaction. The relative receptor affinitiesof the hEGF variants, as determined by radioreceptor competitionassays, varied depending on the amino acid substitution. TheL15F, L15W and L15V hEGF analogues had receptor affinities 45,26 and 18% respectively of wild type hEGF. The L15A and L15Ranalogues displayed receptor affinities of only 2.4 and 1.6%relative to wild type hEGF. No binding of the L15E analoguewas detected. The relative agonist activities, as measured byreceptor tyrosine kinase stimulation assays, generally followeda similar trend. The L15F, L15W and L15V analogues stimulatedthe receptor kinase to a level (V_max) similar to that for wildtype hEGF. A striking difference was observed between the L15Aand L15R variants; although having similar binding affinities,the L15A mutant activated the receptor to only {small tilde}5%of the wild type V_max in contrast to 53% for the L15R mutant¹H-NMR analysis of the L15R and L15A mutants showed only minorstructural alterations that were not sufficient to account forthe dramatic losses in binding and agonist activities. The resultsindicate that both the size and hydrophobicity of the -branchedaliphatic side chain of Leu15 of hEGF are important in the formationof a catalytically active ligand–receptor complex.     

Optimising the T6 heat treatment for gravity cast AlSi7MgCu0.5 alloy V8 cylinder heads

Alternatives to the Standard T6 heat treatment that relied on a 5-h solution heat treatment at 490 °C were investigated in effort to reduce the heat treatment cycle time for the manufacture of AlSi7MgCu0.5 alloy V8 cylinder heads without sacrificing the mechanical properties while providing extra capacity in the heat treatment plant. The optimum T6 heat treatment process was identified to be a SHT at 545 °C for 1 h followed by ageing treatment at 180 °C for 3 h. Mechanical properties of the cylinder heads thus manufactured were markedly superior while the total heat treatment duration was reduced by 2.5 h with respect to the Standard heat treatment. This implied a capacity increase of %61 and rendered the undertaking of a major customer order possible.     

Synthesis,characterization of poly‐2‐ (2‐hydroxybenzylideneamino)‐6‐phenyl‐4,5,6, 7‐tetrahydrobenzo[b]thiophene‐3‐carbonitrile: Investigation of antibacterial activity and optical properties

The oxidative polycondensation reaction conditions of 2‐(2‐hydroxybenzylideneamino)‐6‐phenyl‐4,5,6,7‐tetrahydrobenzo[b]thiophene‐3‐carbonitrile were examined. The magnitude of the reflectance of the polymer decreases sharply with increasing of wavelength up to 524 nm, then reflectance of the polymer increases slowly with increasing of wavelength. The refractive index values of the polymer vary from 1.474 to 2.350. The E_p and E_d values of the polymer were found to be 4.56 and 7.068 eV, respectively. Absorption coefficient K of the polymer is of the order 817.062–1434.77 m^?1. Angle values of incidence and refraction of the polymer vary from 57.36 to 66.95° and from 23.05 to 32.65°, respectively. The film‐phase thickness of the polymer increases with increasing photon energy. The thickness, d, of the polymer was of the order 439.3–4184.7 Å for 190 and 1100 nm, respectively. The real part of dielectric constant of the polymer decreases slowly with increasing of frequency up to about 600 THz, then the real part of dielectric constant of the polymer increases sharply with increasing of frequency. The real and imaginary parts of dielectric constant of the polymer vary from 2.17 to 5.52 and from 5.81 × 10^?5 to 3.58 × 10^?4, respectively. Finally, polymer was tested for antibacterial activities against some bacteria. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

Activatable Photosensitizers: Agents for Selective Photodynamic Therapy

Recent developments in the design of bifunctional and activatable photosensitizers rejuvenate the aging field of photodynamic sensitization and photodynamic therapy. While systematic studies have uncovered new dyes that can serve as potential photosensitizers, the most promising results have come from studies aimed at gaining precise control over the location and rate of cytotoxic singlet oxygen generation. As a consequence, higher selectivities and efficiencies in photodynamic treatment protocols are now within reach. This feature article highlights the variety of approaches that have been pursued to improve photodynamic therapy and to transform simple photosensitizers into smarter theranostic agents.     

Preparation and characterization of new window material CdS thin films at low substrate temperature (<300 K) with vacuum deposition

Low-temperature vacuum deposition instead of the commonly used vacuum deposition at high substrate temperatures has been applied to prepare new window material CdS thin films. The structural, optical and electrical properties of vacuum-evaporated CdS thin films were investigated as a function of substrate temperature (100–300 K) and the post-deposition annealing temperature (at 473, 573 and 673 K). It was determined that films deposited at all substrate temperatures were polycrystalline in nature with hexagonal structure and a strong (0 0 2) texture. The AFM and SEM studies showed that the microstructures of the as-deposited films agreed with the expectations from structure zone model. X-ray diffraction studies showed that the crystallinity of the CdS films was improved on annealing. Optical spectroscopy results of the films indicated that the optical band gap value increased from 2.40 to 2.42 eV with decreased substrate temperature. Increasing the annealing temperature sharpened the band edge. The dark resistivity increased from 4.5×10³ to 7.3×10³ Ω cm and the carrier concentration decreased from 4.7×10¹⁷ to 3.5×10¹⁵ cm⁻³ as the substrate temperature decreased from 300 to 100 K.     

Si/Zr mesoporous catalysts for the vapour phase synthesis of alkylindoles

Si/Zr mesoporous MCM-41 catalysts were investigated in the vapour phase synthesis of 7-ethylindole (7-ETI) starting from 2-ethylaniline (2-ETAN) and ethylene glycol (EG). The catalysts were prepared from the corresponding alkoxides in the presence of a cationic surfactant, which acts as a structure-directing agent. After removal of the surfactant, the resulting mesoporous solids were characterised by X-ray diffraction, N₂ adsorption–desorption, temperature programmed desorption (TPD) of NH₃ and pyridine adsorption coupled with FTIR spectroscopy. As the amount of ZrO₂ increased in the catalysts, the BET surface area decreased, while an enhancement of the acidity took place. The activation of EG to 2-hydroxyacetaldehyde and its attack on 2-ETAN, leading to the formation of 7-ETI, was favoured by increasing the amount of ZrO₂ The maximum yield for the catalyst was obtained with ca. 50 wt.% of ZrO₂, which promoted the presence of Lewis and Brönsted acid sites of suitable strength and concentration, although mesoporous catalysts exhibited very good regenerability.     

Investigation of UV and I–V characteristics of high refractive index polymer thin film for optoelectronic applications

In this study, high refractive index polymer (HRIP) [poly(pentabromobenzyl methacrylate-co-glycidyl methacrylate)] was investigated to obtain its optical and electrical performance for optoelectronic applications. UV characteristics of the polymer in solution of tetrahydrofuran were obtained and optical band gap energy of the polymer was calculated as 3.8 eV. I–V characteristics of the polymer were investigated after HRIP thin film was prepared using spin coating technique. The electrical parameters such as barrier height Φ_Bo, ideality factor n and reverse saturation current I_o were extracted from the forward biasing I–V characteristics. At the same time, series resistance R_s and Φ_Bo were determined by using a modified Norde function combined with conventional forward I–V method.