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- 저자 : Asghar Zamani (검색결과 4 건)
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Reyhane Zamani,Sayyed Shahryar Rahpeyma,Moein Aliakbari,Mousa Naderi,Mohsen Yazdanei,Saeed Aminzadeh,Jafar Khezri,Kamahldin Haghbeen,Ali Asghar Karkhane 한국생물공학회 2023 Biotechnology and Bioprocess Engineering Vol.28 No.4
Improving the thermal stability of enzymes is an essential factor in the industrial applications of enzymes. Many methods related to increased thermal stability were explained, and increasing salt bridges is one of the strategies for improving the thermal stability of enzymes. In this study, mutations T59E, I145R, N149R, V219D, and A262R are introduced into the native cellulase gene to produce the mutant 5M-cel5E cellulase. In silico results showed that the mutation increased the salt bridges from 15 to 28. Root mean square fluctuation (RMSF) calculations confirmed that the mutation increased protein stability. Furthermore, the docking results showed that the affinity of cellobiose for the 5M-cel5E active site (-122.759) was slightly decreased compared to native cellulase (-130.93). No enzymatic activity was found in 5M-cel5E cellulase after cloning, expression and purification. Activated the enzyme with a back mutation of R149N, the result of which was named 4M-cel5E. The last mutation increases the salt bridges from 15 to 22, creating 4 salt bridge networks. The 4M-cel5E enzyme exhibited a maximum activity of 463 U/mg at pH 6.0 and 45°C. The mutations also increased the enzyme thermal stability up to 1.5 and 3.4-fold at temperatures of 65 and 67oC, respectively. These mutations made the Clostridium thermocellum cellulase suitable for various industries such the biofuel and paper.
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Recent developments in liquid-phase synthesis and applications of nanomagnesia
Hanie Abdollahzade,Asghar Zamani Techno-Press 2023 Advances in nano research Vol.14 No.1
Recent developments in the synthesis of nanomagnesia of controlled sizes and shapes that are suitable for various applications are reviewed. Two main methods, based on liquid-phase synthesis, i.e., chemical methods and bio-based methods, are used to synthesize nanomagnesia. Conventionally, nanomagnesia was synthesized by chemical methods such as coprecipitation, sol-gel, combustion method, and so on using different chemical agents and stabilizers which later on become responsible for several biological risks because of the toxicity of used chemicals. Bio-based protocols are growing as another environmental friend method for the synthesis of various nanostructures especially nanomagnesia using biomass, plant extracts, alga, and fungi as a source of precursor material. The ideal method should offer better control of textural properties of nanostructures and decrease the necessity for purification of the synthesized nanoproducts, which sequentially removes the use of large amounts of chemicals and organic solvents and manipulation of products that are unsafe to the environment. Finally, the broad applicability of nanomagnesia in diverse areas is presented. Employment of nanomagnesia reported in several laboratory and industrial fields are valued from the standpoint of the significance of these issues for technological requests, as described in the literature. Nanomagnesia has various applications such as antimicrobial performance, removing pollutants, batteries application, and catalysis.
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Hydrophobicity in nanocatalysis
Alimoradlu, Khadijeh,Zamani, Asghar Techno-Press 2022 Advances in nano research Vol.12 No.1
Nanocatalysts are usually used in the synthesis of petrochemical products, fine chemicals, biofuel production, and automotive exhaust catalysis. Due to high activity and stability, recyclability, and cost-effectiveness, nanocatalysts are a key area in green chemistry. On the other hand, water as a common by-product or undesired element in a range of nanocatalyzed processes may be promoting the deactivation of catalytic systems. The advancement in the field of hydrophobicity in nanocatalysis could relatively solves these problems and improves the efficiency and recyclability of nanocatalysts. Some recent developments in the synthesis of novel nanocatalysts with tunable hydrophilic-hydrophobic character have been reviewed in this article and followed by highlighting their use in catalyzing several processes such as glycerolysis, Fenton, oxidation, reduction, ketalization, and hydrodesulfurization. Zeolites, carbon materials, modified silicas, surfactant-ligands, and polymers are the basic components in the controlling hydrophobicity of new nanocatalysts. Various characterization methods such as N2 adsorption-desorption, scanning and transmission electron microscopy, and contact angle measurement are critical in the understanding of hydrophobicity of materials. Also, in this review, it has been shown that how the hydrophobicity of nanocatalyst is affected by its structure, textural properties, and surface acidity, and discuss the important factors in designing catalysts with high efficiency and recyclability. It is useful for chemists and chemical engineers who are concerned with designing novel types of nanocatalysts with high activity and recyclability for environmentally friendly applications.
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Niko Faraji,Mehdi Mahmoudian,Asghar Zamani 한국고분자학회 2024 폴리머 Vol.48 No.1
In this research, the nanofibrous polystyrene /titanium dioxide nanotube (PS/TiO2 nanotubes) membrane was prepared by the electrospinning method. Titanium dioxide nanotubes were synthesized by the anodizing method and stabilized on the fibrous polystyrene membrane. Then, the effect of different weight percentages of titanium dioxide nanotubes on the performance of the resulting membranes was investigated. The nanoparticles and nano-composites prepared in this research were analyzed using several analyses, including Fourier transform infrared spectroscopy (FTIR) and field emission scanning electron microscopy (FE-SEM), along with X-ray energy diffraction spectroscopy (EDS). The thermal behavior and crystal structure of prepared nano-composite membranes were investigated using (TGA) analysis and X-ray diffraction (XRD), respectively. Afterward, to investigate the prepared structures, analyses such as porosity measurement, water contact angle, swelling, and water flux of the membranes were performed. The photocatalytic property of the prepared membranes in the decomposition of methylene blue was investigated by two methods (static and dynamic). The obtained results demonstrated that the dye removal was accomplished in the best way in the static method (using the membrane as an absorbent) for 48 h. The prepared nano-composite membranes were also used in the dye filtration removal process, and the best result was obtained by using the membrane containing titanium dioxide nanotubes with a concentration, of 0.05 gr/V(50). The swelling degree in the fibrous polystyrene membrane was 135%, while in the membrane containing 0.1% titanium dioxide nanotubes, which is the optimal membrane, was 66%. Hydrophilicity measurements by water contact angle revealed that the presence of TiO2 nanotubes improved by about 10%.
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