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171.
172.
“Head‐to‐Middle” and “Head‐to‐Tail” cis‐Prenyl Transferases: Structure of Isosesquilavandulyl Diphosphate Synthase
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Jian Gao Dr. Tzu‐Ping Ko Lu Chen Dr. Satish R. Malwal Jianan Zhang Xiangying Hu Fiona Qu Dr. Weidong Liu Dr. Jian‐Wen Huang Dr. Ya‐Shan Cheng Dr. Chun‐Chi Chen Yunyun Yang Prof. Dr. Yonghui Zhang Prof. Dr. Eric Oldfield Prof. Dr. Rey‐Ting Guo 《Angewandte Chemie (International ed. in English)》2018,57(3):683-687
We report the first X‐ray crystallographic structure of the “head‐to‐middle” prenyltransferase, isosesquilavandulyl diphosphate synthase, involved in biosynthesis of the merochlorin class of antibiotics. The protein adopts the ζ or cis‐prenyl transferase fold but remarkably, unlike tuberculosinol adenosine synthase and other cis‐prenyl transferases (e.g. cis‐farnesyl, decaprenyl, undecaprenyl diphosphate synthases), the large, hydrophobic side chain does not occupy a central hydrophobic tunnel. Instead, it occupies a surface pocket oriented at 90° to the hydrophobic tunnel. Product chain‐length control is achieved by squeezing out the ligand from the conventional allylic S1 binding site, with proton abstraction being achieved using a diphosphate‐Asn‐Ser relay. The structures revise and unify our thinking as to the mechanism of action of many other prenyl transferases and may also be of use in engineering new merochlorin‐class antibiotics. 相似文献
173.
Li Ao Xu Dezhong Zhang Mengnan Wu Shengzhong Li Yu Sun Weisheng Zhou Yonghui Madyan Omar Abo Fan Mizi Rao Jiuping 《Cellulose (London, England)》2022,29(3):2017-2032
Cellulose - This paper develops a novel paper additive for effectively recycling old corrugated container (OCC) by functionalizing nanocellulose (NC) with diethylenetriaminepentaacetic acid (DTPA)... 相似文献
174.
In this paper, a class of neural networks called bidirectional associative memory (BAM) networks with impulses is discussed. Some sufficient conditions are established for the existence and global exponential stability of a unique periodic solution and the exponentially convergent rate is estimated. The sufficient conditions are easy to be verified and when the impulsive jumps are absent, the results reduce to those of the non-impulsive systems. The approaches are based on employing inequality analysis, matrix theory and its spectral theory. 相似文献
175.
To investigate the flutter characteristics of a folding wing with different configurations, a parameterized aeroelastic model is proposed. First, a parameterized structural model is established based on the substructure synthesis. Afterwards, the parameterized aerodynamic model is derived for each lifting surface using the so-called Doublet Lattice Method (DLM). The correctness of the resulting aeroelastic model is verified via NASTRAN. Finally, some aeroelastic simulations are performed using the proposed aeroelastic model. The results demonstrate that the flutter characteristics of the folding wing are very sensitive to the folding angle. With increasing folding angle, a transition between two unstable modes occurs. Such a transition results in a sudden change of flutter mode shapes and a jump of critical flutter frequency. Besides, there exists a region of folding angle, where the flutter behavior of the folding wing strongly depends on the structural damping. 相似文献
176.
177.
Zhao Yong Xia Yonghui 《Annals of Differential Equations》2008,(4):498-505
In this paper, we study the existence and stability of an equilibrium of discrete-time Cohen-Grossberg BAM Neural Networks with delays. We obtain several sufficient conditions ensuring the existence and stability of an equilibrium of such systems, using discrete Halanay-type inequality and vector Lyapunov methods. In addition, we show that the proposed sufficient condition is independent of the delay parameter. An example is given to demonstrate the effectiveness of the results obtained. 相似文献
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179.
建立了畜禽产品中维吉尼亚霉素M1和S1药物残留检测的液相色谱-串联质谱分析方法。样品以甲醇-乙腈溶液(1:1, v/v)提取,上清液经0.01 mol/L磷酸二氢铵溶液稀释后,Oasis HLB固相萃取小柱净化,Luna C18色谱柱分离,以乙腈和含0.1%(体积分数)甲酸的5 mmol/L乙酸铵水溶液作为流动相进行梯度洗脱,电喷雾正离子模式电离(ESI+),多反应监测(MRM)模式检测,外标法定量。该方法对两物质线性范围均为0.15~10.0 μg/L,相关系数r2均大于0.999;定量下限均为0.25 μg/kg。在不同基质中,0.25、0.50、2.5 μg/kg3个添加水平的平均回收率范围为71.2%~98.4%,精密度范围为3.6%~15.4%。该方法具有快速简便、灵敏度高、准确性强等特点,适用于畜禽产品中维吉尼亚霉素的检测。 相似文献
180.
在pH 2.4的Britton-Robinson(B-R)缓冲溶液中,5-(5-氯-2-吡啶偶氮)-2,4-二氨基甲苯(5-Cl-PADAT)与牛血清蛋白相互作用形成复合物而导致溶液吸收光谱发生变化,用分光光度法对光谱变化进行了研究.5-Cl-PADAT溶液在430 nm处有一个强的特征吸收峰,当在其溶液中加入牛血清蛋白后,溶液发生褪色现象,吸收峰强度降低,且没有新的吸收峰出现,吸光度降低值(ΔA)与牛血清蛋白的浓度(c)成正比.在选择的最佳试验条件下,牛血清蛋白浓度与ΔA的线性方程为ΔA=0.8141c+0.0041(r=0.9996),线性范围为1.071×10-9~5.902×10-9 mol/L,检出限为5.36×10-10 mol/L,该方法的回收率为96.9%~107.1%,测定结果的相对标准偏差为1.4%~2.3%(n=6). 相似文献