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An-Na Li,Chen Xie,Jie Zhang,Jia Zhang,Duo-Chuan Li 한국미생물학회 2011 The journal of microbiology Vol.49 No.1
The serine protease gene from a thermophilic fungus Thermoascus aurantiacus var. levisporus, was cloned,sequenced, and expressed in Pichia pastoris and the recombinant protein was characterized. The full-length cDNA of 2,592 bp contains an ORF of 1,482 bp encoding 494 amino acids. Sequence analysis of the deduced amino acid sequence revealed high homology with subtilisin serine proteases. The putative enzyme contained catalytic domain with active sites formed by three residues of Asp183, His215, and Ser384. The molecular mass of the recombinant enzyme was estimated to be 59.1 kDa after overexpression in P. pastoris. The activity of recombinant protein was 115.58 U/mg. The protease exhibited its maximal activity at 50°C and pH 8.0 and kept thermostable at 60°C, and retained 60% activity after 60 min at 70°C. The protease activity was found to be inhibited by PMSF, but not by DTT or EDTA. The enzyme has broad substrate specificity such as gelatin, casein and pure milk, and exhibiting highest activity towards casein.
Sulfonated multi-walled carbon nanotubes for the removal of copper (II) from aqueous solutions
Yuanyuan Ge,Zhili Li,Duo Xiao,Piao Xiong,Na Ye 한국공업화학회 2014 Journal of Industrial and Engineering Chemistry Vol.20 No.4
Sulfonated multi-walled carbon nanotubes (s-MWCNTs) was prepared from purified multi-walled carbon nanotubes (p-MWCNTs) by concentrated H2SO4 at elevated temperature. The structure was characterized by SEM, FTIR, Raman, XPS, and BET. It could be dispersed steadily in water at a dosage of 1.0 mg/mL for a week. The adsorption performance of s-MWCNTs toward Cu(II) was investigated including the effects of pH and ionic strength. Results indicated the adsorption was much dependent on pH but not on ionic strength. The adsorption capacity for Cu(II) was enhanced 58.9% via the sulfonation. Moreover, the adsorption mechanisms were carefully analyzed by Freundlich and D-R models.
Chen Zhang,Wei Wang,Zhi-Duo Zhu,Na Li,Shao-Yun Pu,Yu Wan,Wang-Wen Huo 대한토목학회 2022 KSCE Journal of Civil Engineering Vol.26 No.1
To investigate the effect of graphene (G) on the triaxial mechanical characteristics of cement stabilized soil, a triaxial unconsolidated and undrained (UU) test was conducted on cement stabilized expansive soil (CES) and graphene-modified cement stabilized expansive soil (GCES) with 0.05%, 0.1%, 0.15%, and 0.2%G content, respectively. The experimental results showedthat compared with CES, the deviatoric stress-strain curve of GCES showed a more obvious softening characteristic. The addition of G had a good modification effect on the triaxial mechanical characteristics of CES, and with the increase of the content of G, the compressive strength and shear strength of CES increased first and then decreased, and reached the best value when the G content was 0.1%. The failure angle predicted by the Mohr-Coulomb failure angle formula had a good correlation with the measured failure angle of soil specimens, so it could provide help for the prediction of soil failure surface in practical engineering. Besides, the scanning electron microscope (SEM) analysis indicated that the internal structure of CES was improved due to G addition.