摘要：
Rationally designed biosynthetic models provide fantastic advantages for addressing important issues in chemistry and biology. Previously, two distal histidines were introduced in the heme pocket of myoglobin (Mb) at positions 29 and 43. The resultant His29 and His43, together with the native His64, formed a metal-binding site in the designed L29H/F43H Mb mutant, which closely mimics the heterobinuclear center of native cytochrome c oxidase (CcO). Instead of studying the oxidase activity, we herein investigated the cross-reactivity, i.e., the peroxidase activity of this mutant, as well as the effect of metal ions binding to the designed metal-binding site on protein reactivity. It was found that the introduced two distal histidines with no bound metal ion serve to improve the peroxidase activity of L29H/F43H Mb compared with that of WT Mb containing a single distal histidine, whereas the binding of metal ions such as Cu(II) and Zn(II) to L29H/F43H Mb inhibits the catalytic activity to a different extent. These findings provide valuable insights into the peroxidase activity observed for the native CcO, as well as the role of metal ion in fine-tuning the protein cross-reactivity.
期刊：
JOURNAL OF AOAC INTERNATIONAL,2013年96(4):897-901 ISSN：1060-3271
通讯作者：
Peng, Tao
作者机构：
[Nie, Chang-Ming; Xie, Jie; Zhang, Qing-Jie] Univ South China, Dept Chem & Chem Engn, Hengyang 421001, Hunan, Peoples R China.;[Peng, Tao; Chen, Dong-Dong] Chinese Acad Inspect & Quarantine, Agroprod Safety Res Ctr, Beijing 100123, Peoples R China.;[Wang, Xiong] Clover Technol Grp Ltd, Beijing 100044, Peoples R China.;[Wang, Guo-Min] Chongqing Entry Exit Inspect & Quarantine Bur, Chongqing 400020, Peoples R China.
通讯机构：
[Peng, Tao] C;Chinese Acad Inspect & Quarantine, Agroprod Safety Res Ctr, Beijing 100123, Peoples R China.
摘要：
A method based on HPLC with UV detection was developed for the quantitative determination of chloramphenicol (CAP) residues in aquatic products. The samples were extracted with ethyl acetate–ammonium hydroxide (98 + 2, v/v), followed by a cleanup step using an immunoaffinity column. The analytes were determined by HPLC-UV. Optimal conditions for the extraction and cleanup procedures are described. The linear regression equation was y = 91.47x – 8.60 with R2 = 0.9998 (y = peak area and x = CAP concentration) and showed a good reproducibility. The LOQ was 0.25 μg/kg for determining CAP spiked in the aquatic products. The mean recoveries of CAP from fish and shrimp samples fortified at 0.25–1.0 μg/kg were 88.7–93.1 and 92.0–97.3%, respectively; the repeatability RSDs were less than 8.1%. It was concluded that the method is simple, highly sensitive, and low cost for quantitatively measuring CAP residues in aquatic products. Analyte identification was confirmed by HPLC/MS/MS analysis.
作者：
Nie, Changming*;Wu, Yaxin;Wu, Rongyan;Wen, Songnian
期刊：
Journal of the Chilean Chemical Society,2012年57(1):955-963 ISSN：0717-9707
通讯作者：
Nie, Changming
作者机构：
[Nie, Changming; Wu, Yaxin] Univ S China, Sch Chem & Chem Engn, Hengyang 421001, Hunan, Peoples R China.;[Wu, Rongyan; Wen, Songnian] Univ S China, Coll Elect Engn, Hengyang 421001, Hunan, Peoples R China.
通讯机构：
[Nie, Changming] U;Univ S China, Sch Chem & Chem Engn, Hengyang 421001, Hunan, Peoples R China.
关键词：
cis/trans isomers;ionicity index matrix;improved distance matrix;branching degree matrix
摘要：
In this paper, on the basis of the topological index EDm derived from ionicity index matrix, improved distance matrix and branching degree matrix, we proposed the new topological descriptor EDm' by introducing the bond angle into hidden hydrogen graph of molecules and using the geometric distance instead of the sum of bond length between two vertexes. The EDm' describes the molecular structure more accurately, and realizes unique characterization to cis-trans isomers. The quantitative structure-property relationship (QSPR) models, with correlation coefficients (R) in the range of 0.984-1.000 for the boiling point (b.p.), the standard enthalpy of formation (DrHm theta), the molar refraction (R-m) and the molar volume (V-m) of some cis-trans isomers for alkenes, are subsequently developed by index EDm'. Moreover, the good stability and predictive ability of the models were demonstrated by LOU (leave-one-out) method and RSP (random sampling prediction) method, which further manifests the index EDm' has high potential of wide applications in QSPR study.
摘要：
Myoglobin (Mb) is an ideal scaffold protein for rational protein design mimicking native enzymes. We recently designed a nitrite reductase (NiR) based on sperm whale Mb by introducing an additional distal histidine (Leu29 to His29 mutation) and generating a distal tyrosine (Phe43 to Tyr43 mutation) in the heme pocket, namely L29H/F43Y Mb, to mimic the active site of cytochrome cd
1 NiR from Ps. aeruginosa that contains two distal histidines and one distal tyrosine. The molecular modeling and dynamics simulation study herein revealed that L29H/F43Y Mb has the necessary structural features of native cytochrome cd
1 NiR and can provide comparable interactions with nitrite as in native NiRs, which provides rationality for the protein design and guides the protein engineering. Additionally, the present study provides an insight into the relatively low NiR activity of Mb in biological systems.
摘要：
A wireless sensing method for the measurement of gamma radiation dose has been developed based on the fact that gamma rays can initiate the polymerization of acrylamide, which causes an increase in solution viscosity that can be detected with a wireless magnetoelastic sensor. The magnetoelastic sensor is able to wirelessly detect the resonance frequency shifts of a magnetoelastic foil in response to changes in solution viscosity. There is a linear relationship between the resonance frequency shift and gamma radiation dose in the range of 0–50 Gy (under optimal conditions) with a detection limit of 0.25 Gy. This method has the advantage of providing real-time, continuous measurement in situ. The method has been used successfully to determine the gamma radiation dose in real exposure scenarios, with satisfactory results.
