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- 저자 : ( Hongwen Chen ) (검색결과 2 건)
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Ma, Junpeng,Fan, Jingbiao,Chen, Shang,Yang, Xinyue,Hui, Kwun Nam,Zhang, Hongwen,Bielawski, Christopher W.,Geng, Jianxin American Chemical Society 2019 ACS APPLIED MATERIALS & INTERFACES Vol.11 No.14
<P>Lithium-sulfur (Li-S) batteries have received significant attention due to the high theoretical specific capacity of sulfur (1675 mA h g<SUP>-1</SUP>). However, the practical applications are often handicapped by sluggish electrochemical kinetics and the “shuttle effect” of electrochemical intermediate polysulfides. Herein, we propose an in-situ copolymerization strategy for covalently confining a sulfur-containing copolymer onto reduced graphene oxide (RGO) to overcome the aforementioned challenges. The copolymerization was performed by heating elemental sulfur and isopropenylphenyl-functionalized RGO to afford a sulfur-containing copolymer, that is, RGO-<I>g</I>-poly(S-<I>r</I>-IDBI), which is featured by a high sulfur content and uniform distribution of the poly(S-<I>r</I>-IDBI) on RGO sheets. The covalent confinement of poly(S-<I>r</I>-IDBI) onto RGO sheets not only enhances the Li<SUP>+</SUP> diffusion coefficients by nearly 1 order of magnitude, but also improves the mechanical properties of the cathodes and suppresses the shuttle effect of polysulfides. As a result, the RGO-<I>g</I>-poly(S-<I>r</I>-IDBI) cathode exhibits an enhanced sulfur utilization rate (10% higher than that of an elemental sulfur cathode at 0.1C), an improved rate capacity (688 mA h g<SUP>-1</SUP> for the RGO-<I>g</I>-poly(S-<I>r</I>-IDBI) cathode vs 400 mA h g<SUP>-1</SUP> for an elemental sulfur cathode at 1C), and a high cycling stability (a capacity decay of 0.021% per cycle, less than one-tenth of that measured for an elemental sulfur cathode).</P> [FIG OMISSION]</BR>
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( Hongwei Guo ),( Jinyao Han ),( Jingjing Wu ),( Hongwen Chen ) 한국미생물생명공학회(구 한국산업미생물학회) 2019 Journal of microbiology and biotechnology Vol.29 No.4
The engineered Aspergillus oryzae has a high NADPH demand for xylose utilization and overproduction of target metabolites. Glucose-6-phosphate dehydrogenase (G6PDH, E.C. 1.1.1.49) is one of two key enzymes in the oxidative part of the pentose phosphate pathway, and is also the main enzyme involved in NADPH regeneration. The open reading frame and cDNA of the putative A. oryzae G6PDH (AoG6PDH) were obtained, followed by heterogeneous expression in Escherichia coli and purification as a his6-tagged protein. The purified protein was characterized to be in possession of G6PDH activity with a molecular mass of 118.0 kDa. The enzyme displayed maximal activity at pH 7.5 and the optimal temperature was 50°C. This enzyme also had a half-life of 33.3 min at 40°C. Kinetics assay showed that AoG6PDH was strictly dependent on NADP+ (K<sub>m</sub> = 6.3 μM, k<sub>cat</sub> = 1000.0 s<sup>-1</sup>, k<sub>cat</sub>/K<sub>m</sub> =158.7 s<sup>-1</sup>·μM<sup>-1</sup>) as cofactor. The K<sub>m</sub> and k<sub>cat</sub>/K<sub>m</sub> values of glucose-6-phosphate were 109.7 s<sup>-1</sup>·μM<sup>-1</sup> and 9.1 s<sup>-1</sup>·μM<sup>-1</sup> respectively. Initial velocity and product inhibition analyses indicated the catalytic reaction followed a two-substrate, steady-state, ordered BiBi mechanism, where NADP<sup>+</sup> was the first substrate bound to the enzyme and NADPH was the second product released from the catalytic complex. The established kinetic model could be applied in further regulation of the pentose phosphate pathway and NADPH regeneration of A. oryzae to improve its xylose utilization and yields of valued metabolites.
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