Yulin Huang,Xike Tian,Yulun Nie,Chao Yang,Yanxin Wang
Cu(II) doped mesoporous MnO 2 (Cu-MnO 2 ) was prepared to establish an intimate functional link between the structure substitution and catalytic peroxymonosulfate (PMS) activation. Based on the characterization of powder X-ray diffraction (XRD), N 2 adsorption-desorption measurement, scanning electron microscope (FE-SEM) and transmission electron microscope (TEM), Cu-MnO 2 had a typical long range ordered mesoporous structure and Cu was successfully introduced in octahedral framework. It exhibited excellent catalytic activity and stability for the phenol degradation by PMS. Phenol was always efficiently degraded over Cu-MnO 2 at a pH range of 3.5–9.0. For example, the reaction rate constant at pH 7.0 was 0.073 min −1 , which was two times higher than that of MnO 2 (0.039 min −1 ). Importantly, 1 O 2 was identified as the primary reactive species in Cu-MnO 2 /PMS system. X-ray photoelectron spectroscopy (XPS) confirmed that more exposed surface oxygen defects due to Cu doping were responsible to the enhancement of PMS activation for phenol degradation. The results of PMS decomposition and oxygen evolution indicated that surface oxygen defects lower the reaction energy barrier of PMS decomposition by generating 1 O 2 via the energy trapping by oxygen. Finally, the heterogeneous PMS activation mechanism over Cu-MnO 2 was proposed.
Jun Ren,Hao Xiong,Chundong Huang,Fangling Ji,Lingyun Jia
Camelid-derived nanobody is emerging as a resourceful platform for developing immunoaffinity ligands for chromatography applications. Featured by high affinity and selectivity, BC2 nanobody (BC2-Nb), which can recognize a specific epitope tag (PDRKAAVSHWQQ, termed BC2T), is potential to be developed as a general tool for recombinant protein purification. However, excessively high affinity between binding partners makes the desorption of products less efficient and limits its application. Aiming to improve elution efficiency, structure-guided mutations of BC2-Nb were conducted to adjust the structural flexibility of its antigen-binding site. Six ligand variants were obtained with their binding affinity decreasing by about 100-fold. Among them, one mutated BC2-Nb named 44D was chosen to prepare immunoaffinity resin, and its adsorption and elution performance were well characterized. The site-directed mutation led to the equilibrium dissociation constant (K D ) of BC2-Nb changing from 1.4 × 10 −9 M to 1.4 × 10 −7 M (44D). The resin using 44D as ligand retained a static binding capacity of 19.14 mg/mL toward BC2T-fused enhanced green fluorescent protein (eGFP-BC2T). Significantly improved elution efficiency was obtained with the mutated ligand. Protein recovery reached 94% at pH 3.5 for 44D-based resin, while the resin based on original BC2-Nb could only achieve its highest recovery of 84% at pH 2. In addition, a neutral elution condition (1 M arginine containing 50% propylene glycol, pH 7.4) was also found effective, which allowed a product recovery of 95%. The resin enabled direct capturing of eGFP-BC2T from bacterial lysates, and the one-step purification with the both elution conditions could achieve a product purity of more than 90%. This study provided a promising affinity ligand, and also proved the feasibility of controlling the elution process of nanobody-based affinity resin through the strategy of binding sites modification.
危险品化学品经营许可证（带存储）