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To realize the soluble expression of human-derived Tumstatin in Escherichia coli. Five recombinant E. coli (BL21(DE3)) expressed by fusion of different solubility-promoting fusion tags and tumstatin genes were constructed, and isopropyl-beta-D-thiogalactopyranoside (IPTG) was used to induce the recombinant bacteria to express the target protein. SDS-PAGE and Western-Blot were employed to analyze and screen for the recombinant bacteria that could solubility express Tumstatin. The results indicated that BL21/pGEX-6p-1-Tum (containing glutathione mercaptotransferase tag -GST tag), BL21/pET28a-MBP-Tum (containing maltose-binding protein tag-MBP tag), BL21/pET28a-Tum (no tag) all expressed the fusion protein Tumstatin in the form of inclusion bodies. Only the recombinant bacteria BL21/pET28a-XXA-Tum (containing the reverse protein of antifreeze protein-XXA tag) expressed fusion proteins in a soluble form, and the target protein accounts for more than 45% of the total protein of the bacteria. The target protein was purified by affinity chromatography and analyzed by Western-Blot. The band of interest with a molecular weight of 50.9 kDa was obtained, which was consistent with the theoretical molecular weight. Furthermore, the inducer concentration, addition time, induction temperature, and induction time of recombinant bacteria BL21/pET28a-XXA-Tum were optimized. Finally, the induction conditions of tumstatin fusion protein were selected as follows: Inducer concentration 0.1 mmol/L, inducer added at 2 h, induction temperature 16°C, induction time 36 h. The soluble expression of human Tumstatin in E. coli laid the foundation for the preparation of soluble human-derived Tumstatin in a large scale, which could provide a reference for the soluble expression of functional polypeptides in E. coli. [ABSTRACT FROM AUTHOR]

An accurate prediction of nonlinear hydro‐mechanical (HM) coupling in subsurface structures with pronounced heterogeneity at multiple spatial scales is still an open topic and crucial for numerous engineering applications, for example, hydraulic fracturing and enhanced geothermal systems. In this study, novel high‐order multi‐scale asymptotic solutions are developed to accurately capture the locally oscillating characteristics of gas flow and solid displacement fields at multiple scales. First, the formal macro‐meso two‐scale asymptotic expansion is performed to establish the homogenized solutions and macro‐meso high‐order models which can predict the HM coupling problems at the macroscale and mesoscale. By directly expanding the cell functions defined at the mesoscale to the microscopic levels, the high‐order two‐scale expansion for the mesoscopic cell functions is built, and the upscaled relations for the flow parameters and constitutive coefficients from the microscale to the mesoscale and macroscale are developed correspondingly. The multi‐scale low/high‐order models are established by combining the high‐order expansion of all cell functions at the mesoscale and the developed macro‐meso two‐scale models. The main contributions are that the present approaches follow the reverse thought processes of reiteration homogenization methods, and offer a very innovative and efficient way to establish high‐accuracy high‐order models for the nonlinear HM coupling problems in the heterogeneous porous medium with any number of spatial scales. The effectiveness and accuracy of the present solution are validated by several representative cases with different constitutive coefficient contrasts. The results demonstrate that the high‐order solutions provide an accurate prediction for gas transport and solid deformation of heterogeneous porous media with multi‐scale configurations. [ABSTRACT FROM AUTHOR]

As a chewing hobby, areca nut (Areca catechu L.) has become the most common psychoactive substance in the world, besides tobacco, alcohol and caffeinated beverages. Moreover, as a first‐class carcinogen designated by International Agency for Research on Cancer, long‐term chewing areca nut can result in oral mucosal diseases and even oral cancer. To clarify the potential mechanism of areca nut addiction, an integrated strategy of metabolomics and network pharmacology was adopted in this study. Network pharmacology study indicated that all the key targets related to areca nut addiction could be regulated by arecoline and pointed out the importance of G‐protein coupled receptor signalling pathway. Analysis results of mice plasma metabolome and faeces metabolome intervened by arecoline suggested that the component may affect the dopamine system and 5‐HT system by regulating phenylalanine, tyrosine and tryptophan biosynthesis, phenylalanine metabolism, primary bile acid biosynthesis, glycerophospholipid metabolism and intestinal flora structure. Moreover, the potential importance of bile acids in formation of addictive behaviour of chewing areca nut was investigated by integrative analysis of the relationships between metabolites and intestinal flora. The study can provide scientific basis for the addiction intervention and treatment of areca nut chewers. [ABSTRACT FROM AUTHOR]

This paper studies a method for high-precision acquisition of position signals for permanent magnet direct drive servo motors at low speed. First of all, the problem of poor position feedback accuracy and sensor feedback delay in the low-speed operation of the permanent magnet direct drive servo motor is analyzed. Secondly, through analysis and simulation, it is found that the interpolation method can play a certain role in compensating the rotor position signal. However, when the speed is close to 0, the output signal of the sensor will fluctuate in a short time, which will affect the speed control accuracy. Therefore, this paper uses the observer method to achieve high-precision acquisition of the position signal of the permanent magnet direct drive servo motor at low speed. The observer method adopts the idea of combining the system model and closed-loop control. Additionally, it makes full use of the parameter information of the motor system. The control performance of the motor can be better guaranteed through the design of the observer parameters and the accuracy of the rotor position estimation result has been greatly improved. Finally, an experimental platform for permanent magnet direct drive servo motors is built, and the rotor position signal acquisition method based on the observer method is verified to have good performance through simulation and experiments. Not only the accuracy of the rotor position estimation result is improved, but also the motor control performance is improved, realizing the stable operation of the permanent magnet direct drive servo motor at low speed. [ABSTRACT FROM AUTHOR]