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Liyun Su,Guanxin Huang,Ruirui Huang,Zhijun Yang 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.12
This paper proposes a long-stroke rigid-flexible coupling motion stage (RFCMS) that employs flexure hinges to compensate the friction dead zone through elastic deformation. Specifically, based on the need for a motion stage with a compact structure, this paper proposes a new rigid-flexible coupling structure (RFCS) design with a horizontally installed linear motor and asymmetric flexure hinges. Further, end leaf springs are introduced to enhance the stiffness in the non-motion direction. In addition, the nonlinear interior-point optimization method is used to obtain the optimal structural parameters of the flexure hinges for higher deformation uniformity. To verify the effectiveness of the proposed design, a motion stage benchmarked with Aerotech's PRO190LM (stroke, 500 mm) is developed, which realizes bidirectional repeatability (BR) of ±0.25 μm. The BR is improved by 37.5 %. Moreover, the deformation uniformity of the stage is ±3.7 %, which proves that the proposed RFCMS can achieve high deformation uniformity and high precision.
Biochemical Properties and Physiological Roles of NADP-Dependent Malic Enzyme in Escherichia coli
Baojuan Wang,Peng Wang,Enxia Zheng,Xiangxian Chen,Hanjun Zhao,Ping Song,Ruirui Su,Xiaoning Li,Guoping Zhu 한국미생물학회 2011 The journal of microbiology Vol.49 No.5
Malic enzymes catalyze the reversible oxidative decarboxylation of L-malate using NAD(P)^+ as a cofactor. NADP-dependent malic enzyme (MaeB) from Escherichia coli MG1655 was expressed and purified as a fusion protein. The molecular weight of MaeB was about 83 kDa, as determined by SDS-PAGE. The recombinant MaeB showed a maximum activity at pH 7.8 and 46°C. MaeB activity was dependent on the presence of Mn^(2+) but was strongly inhibited by Zn^(2+). In order to understand the physiological roles, recombinant E. coli strains (icdNADP/ΔmaeB and icdNAD/ΔmaeB) containing NADP-dependent isocitrate dehydrogenase (IDH), or engineered NAD-dependent IDH with the deletion of the maeB gene, were constructed using homologous recombination. During growth on acetate, icd^(NAD)/ΔmaeB grew poorly, having a growth rate only 60% that of the wild-type strain (icd^(NADP)). Furthermore, icd^(NAD)P/ΔmaeB exhibited a 2-fold greater adaptability to acetate than icdNAD/ΔmaeB, which may be explained by more NADPH production for biosynthesis in icd^(NAD)P/ΔmaeB due to its NADP-dependent IDH. These results indicated that MaeB was important for NADPH production for bacterial growth on acetate. We also observed that MaeB activity was significantly enhanced (7.83-fold) in icd^(NAD), which was about 3-fold higher than that in icd^(NADP), when switching from glucose to acetate. The marked increase of MaeB activity was probably induced by the shortage of NADPH in icd^(NAD). Evidently, MaeB contributed to the NADPH generation needed for bacterial growth on two carbon compounds.