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RISS 인기검색어
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- 저자 : Li Mingke (검색결과 3 건)
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Xiaozhan Li,Wenming Zhang,Mingke Wu,Fengxue Xin,Weiliang Dong,Hao Wu,Min Zhang,Jiangfeng Ma,Min Jiang 한국생물공학회 2017 Biotechnology and Bioprocess Engineering Vol.22 No.5
Succinic acid is a platform chemical with potential for bio-based synthesis. However, the production of bio-based succinate is limited because of insufficient succinate efflux capacity in the late stage of fermentation. In the present study, three different transporters, which have been reported to be responsible for C4-dicarboxylates transport, were employed for investigation of the transport capacity of succinate in Escherichia coli. After engineered strains were constructed, the fermentative production of succinic acid was studied in serum bottles and 3 L of fermentor. The results demonstrated that engineered strain showed better efflux capacity than control strain under high concentration of succinate. The highest production of succinate was 68.66 g/L, while the NCgl2130 transporter may be the best candidate for succinate export in E. coli. Further research showed that the expression levels and relative enzyme activities involved in the metabolic pathway all increased markedly, and the maximum activities of PPC, PCK, PYK, and MDH increased by 1.50, 1.38, 1.28, and 1.27-fold in recombinant E. coli AFP111/pTrc99a- NCgl2130, respectively. Moreover, the maximum level of intracellular ATP increased by 23.79% in E. coli AFP111/ pTrc99a-NCgl2130. Taken together, these findings indicated that engineered transporters can improve succinate production by increasing key enzyme activities and intracellular ATP levels. To the best of thew authors’ knowledge, this is the first report on a mechanism to improve succinate production by engineered transporters. This strategy set up a foundation for improving the biosynthesis of other C4-dicarboxylates, such as fumaric acid and malic acid.
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Analysis of coupled vibration characteristics of PMS grinding motorized spindle
Feng Gao,Mingke Cheng,Yan Li 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.9
Field-path-kinetic coupling and the multi-body dynamics models were established and the finite element method (FEM) was used to study the coupled vibrations of motorized spindle. The results show that the frequency is mainly 1f r at low speeds, fractional-octave and 1f r at high-speed only the bearing force. The orbit of bearing transitions is from a more pronounced circle to an approximately circular shape, while the rotor changes from a rule to a random pattern. The front bearing is more obvious than the rear and the orbits are always round; the radius of the orbit at the front bearing gradually increases as the speed increases. The result is the vibration displacement changes more significantly close to the spindle end and the amplitude increases accordingly. The experimental results show that operating conditions are closer to the normal, the influence of unbalanced magnetic pull can be neglected, the bearing selection and assembly are reasonable.
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Luo Juan,Bai Luyan,Tao Jun,Wen Yu,Li Mingke,Zhu Yunzhen,Luo Sufeng,Pu Guangyu,Ma Lanqing 한국유전학회 2021 Genes & Genomics Vol.43 No.10
Background Vacuolating cytotoxin (VacA) is an important virulence factor of Helicobacter pylori (H. pylori). It was previously believed that VacA can trigger the cascade of apoptosis on mitochondria to lead to cell apoptosis. Recently, it was found that VacA can induce autophagy. However, the molecular mechanism by which VacA induces autophagy is largely unknown. Objective We aimed to explore the molecular mechanism of autophagy induced by H. pylori in gastric cancer cells and the efect of autophagy on the survival of gastric cancer cells. Methods The autophagy of human gastric cancer cell line SGC7901 was detected by Western blot and RT-PCR in the treatment of VacA protein of H. pylori. The relationship between autophagy and reactive oxygen species (ROS) in the proliferation of gastric cancer cells were studied by gene expression silences (siRNA) and CM-H2DCFDA (DCF) staining. Results The results showed that VacA protein secreted by H. pylori in the supernatant stimulated autophagy in SGC7901 cells. After VacA protein treatment, the mRNA expressions of BECN1, ATG7 and PIK3C3, were up-regulated. ATG7 silencing by siRNA inhibited VacA-induced autophagy. Furthermore, our data demonstrated that VacA protein increased ROS levels. Addition of the antioxidant N-acetyl-l-cysteine (NAC) suppressed the levels of ROS, leading to inhibition of autophagy. Conclusions H. pylori VacA is a key toxin that induces autophagy by increased ROS levels. And our fndings demonstrated that VacA signifcantly inhibited proliferation in SGC7901 cells.
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