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41.
Anirudra Parajuli Daniel H. Kwak Luca Dalponte Dr. Niina Leikoski Tomas Galica Ugochukwu Umeobika Dr. Laurent Trembleau Andrew Bent Prof. Kaarina Sivonen Matti Wahlsten Dr. Hao Wang Dr. Ermanno Rizzi Prof. Gianluca De Bellis Prof. James Naismith Prof. Marcel Jaspars Prof. Xinyu Liu Dr. Wael Houssen Dr. David Peter Fewer 《Angewandte Chemie (International ed. in English)》2016,55(11):3596-3599
Cyanobactins are a rapidly growing family of linear and cyclic peptides produced by cyanobacteria. Kawaguchipeptins A and B, two macrocyclic undecapeptides reported earlier from Microcystis aeruginosa NIES‐88, are shown to be products of the cyanobactin biosynthetic pathway. The 9 kb kawaguchipeptin (kgp) gene cluster was identified in a 5.26 Mb draft genome of Microcystis aeruginosa NIES‐88. We verified that this gene cluster is responsible for the production of the kawaguchipeptins through heterologous expression of the kgp gene cluster in Escherichia coli. The KgpF prenyltransferase was overexpressed and was shown to prenylate C‐3 of Trp residues in both linear and cyclic peptides in vitro. Our findings serve to further enhance the structural diversity of cyanobactins to include tryptophan‐prenylated cyclic peptides. 相似文献
42.
介绍用无动力采样技术采集样品、离子色谱法分析SO2污染物浓度的监测方法。国际实验室间分析结果的比对实验表明,离子色谱法具有快捷、准确及自动化程度较高等优点。该方法在城市和背景区域环境空气背景值研究,如SO2污染物迁移规律、空气质量预测预报模型验证及远距离传输等方面具有很大的实用价值。 相似文献
43.
毛细管电泳法快速测定保健食品中免疫球蛋白G 总被引:10,自引:0,他引:10
建立了毛细管电泳法快速测定保健食品中免疫球蛋白G(IgG)含量的方法,成功测定了不同剂型(片剂、粉剂及胶囊)牛初乳保健品中IgG的含量。以37 cm×50μm(i.d.)未涂敷熔融石英毛细管为色谱分离柱,50 mmol/L四硼酸钾 65 g/L聚乙二醇20 000(1 mol/L氢氧化铯调pH 10.0)为运行缓冲液,于214 nm波长处检测。详细研究了影响实际样品中IgG分离及准确定量的关键因素,如添加剂的种类、浓度;运行及样品缓冲液的浓度及pH等。采用峰面积外标法定量。方法的精密度为2.1%(n=7);检出限为6.25 mg/L(S/N=3);线性范围为50~2000 mg/L;400 mg/L IgG迁移时间的相对标准偏差(RSD)为0.14%;峰面积的RSD为2.9%(n=7)。6 m in内即可实现保健食品中IgG的分离与测定,结果与产品标示值基本吻合。 相似文献
44.
Feasibility study on qualitative and quantitative analysis in tea by near infrared spectroscopy with multivariate calibration 总被引:2,自引:0,他引:2
This study attempted the feasibility to use near infrared (NIR) spectroscopy as a rapid analysis method to qualitative and quantitative assessment of the tea quality. NIR spectroscopy with soft independent modeling of class analogy (SIMCA) method was proposed to identify rapidly tea varieties in this paper. In the experiment, four tea varieties from Longjing, Biluochun, Qihong and Tieguanyin were studied. The better results were achieved following as: the identification rate equals to 90% only for Longjing in training set; 80% only for Biluochun in test set; while, the remaining equal to 100%. A partial least squares (PLS) algorithm is used to predict the content of caffeine and total polyphenols in tea. The models are calibrated by cross-validation and the best number of PLS factors was achieved according to the lowest root mean square error of cross-validation (RMSECV). The correlation coefficients and the root mean square error of prediction (RMSEP) in the test set were used as the evaluation parameters for the models as follows: R = 0.9688, RMSEP = 0.0836% for the caffeine; R = 0.9299, RMSEP = 1.1138% for total polyphenols. The overall results demonstrate that NIR spectroscopy with multivariate calibration could be successfully applied as a rapid method not only to identify the tea varieties but also to determine simultaneously some chemical compositions contents in tea. 相似文献
45.
Di CA Yu G Liu Y Xu X Wei D Song Y Sun Y Wang Y Zhu D Liu J Liu X Wu D 《Journal of the American Chemical Society》2006,128(51):16418-16419
The characteristics of organic field-effect transistors (OFETs) were dramatically improved by chemically modifying the surface of the bottom-contact Ag or Cu source-drain (D-S) electrodes with a simple solution method. The contact resistance and energetic mismatch typically observed with Ag D-S electrodes in pentacene bottom-contact OFETs can be properly eliminated when modified by the Ag-TCNQ (TCNQ = 7,7,8,8-tetracyanoquinodimethane). The pentacene transistors with low-cost Ag-TCNQ-modified Ag bottom-contact electrodes exhibit outstanding electrical properties, which are comparable with that of the Au top-contact devices. It thus provides a novel way toward high-performance low-cost bottom-contact OFETs. 相似文献
46.
Matheus Dorneles de Mello Gaurav Kumar Tarnuma Tabassum Sheetal K. Jain Tso‐Hsuan Chen Stavros Caratzoulas Xinyu Li Dionisios G. Vlachos Songi‐I Han Susannah L. Scott Paul Dauenhauer Michael Tsapatsis 《Angewandte Chemie (International ed. in English)》2020,59(32):13260-13266
Phosphorus‐modified all‐silica zeolites exhibit activity and selectivity in certain Brønsted acid catalyzed reactions for biomass conversion. In an effort to achieve similar performance with catalysts having well‐defined sites, we report the incorporation of Brønsted acidity to metal–organic frameworks with the UiO‐66 topology, achieved by attaching phosphonic acid to the 1,4‐benzenedicarboxylate ligand and using it to form UiO‐66‐PO3H2 by post‐synthesis modification. Characterization reveals that UiO‐66‐PO3H2 retains stability similar to UiO‐66, and exhibits weak Brønsted acidity, as demonstrated by titrations, alcohol dehydration, and dehydra‐decyclization of 2‐methyltetrahydrofuran (2‐MTHF). For the later reaction, the reported catalyst exhibits site‐time yields and selectivity approaching that of phosphoric acid on all‐silica zeolites. Using solid‐state NMR and deprotonation energy calculations, the chemical environments of P and the corresponding acidities are determined. 相似文献
47.
本文构建了特异性识别黄曲霉毒素B1(AFB1)的磁珠-适配体,并与高效液相色谱-串联质谱联用(LC-MS/MS),建立食品中AFB1的定量检测方法。 利用碳二亚胺盐酸盐(EDC)活化法,将羧基磁珠进行活化。 活化后的羧基磁珠与5'端氨基修饰的适配体进行孵育结合,通过酰胺反应将适配体共价连接在羧基磁珠表面,固定在磁珠表面的适配体作为捕捉探针将样品提取液中的AFB1分离,通过LC-MS/MS对AFB1进行定性和定量分析。 检测结果表明:AFB1在浓度0.25~25 ng/mL呈良好的线性关系,相关系数R2=0.999,定量检出限为0.25 ng/mL,回收率达到80.3%~92.5%,相对标准偏差(RSD)低于8%。 该方法操作简单、快速便捷、可痕量地检测AFB1,所制备的磁珠-适配体可重复利用,为定量检测AFB1提供了另一种技术支持。 相似文献
48.
Yongxing Tang Yajun Yu Xinyu Wei Jin Yang Yeting Zhu Yun-Hui Zhao Zilong Tang Zhihua Zhou Xiaofang Li Xianyong Yu 《Tetrahedron letters》2019,60(43):151187
A novel 6-endo-dig cyclization followed by oxidation/elimination of o-alkynylarylaldimines with 4-hydroxybenzylamine was developed for preparation of isoquinolines. The intermediates of this tandem reaction were monitored by mass spectroscopy (MS) to confirm the reaction pathway. This methodology was further applied to the design and synthesis of a novel ratiometric chemosensor for determination of fluoride. 相似文献
49.
Jianyou Mao Zhiting Wang Xinyu Xu Guoqing Liu Runsheng Jiang Haixing Guan Zhipeng Zheng Patrick J. Walsh 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(32):11149-11154
Indoles are essential heterocycles in medicinal chemistry, and therefore, novel and efficient approaches to their synthesis are in high demand. Among indoles, 2‐aryl indoles have been described as privileged scaffolds. Advanced herein is a straightforward, practical, and transition‐metal‐free assembly of 2‐aryl indoles. Simply combining readily available 2‐fluorotoluenes, nitriles, LiN(SiMe3)2, and CsF enables the generation of a diverse array of indoles (38 examples, 48–92 % yield). A range of substituents can be introduced into each position of the indole backbone (C4 to C7, and aryl groups at C2), providing handles for further elaboration. 相似文献
50.
Acceptorless photocatalytic dehydrogenation is not only a promising alternative to photocatalytic water splitting for hydrogen generation but also provides a green and sustainable strategy for the synthesis of value-added organic compounds. In this work, Ti3C2Tx/CdS nanocomposites were obtained by self-assembly of hexagonal CdS in the presence of preformed Ti3C2Tx nanosheets, which serves as a photocatalyst for acceptorless dehydrogenation of biomass-derived furfuryl alcohol (FOL) to furfural (FAL) and furoic acid (FA) in neutral and alkaline medium respectively, with simultaneous generation of stoichiometric hydrogen under visible light. Ti3C2Tx MXene acts as an efficient cocatalyst for the photocatalytic dehydrogenation of FOL over CdS, with an optimum performance achieved over 0.50 wt% Ti3C2Tx/CdS nanocomposite. This study provides an economic and sustainable strategy for the simultaneous valorization of biomass-derived FOL to produce FAL and FA as well as the production of clean energy hydrogen under mild condition based on noble metal-free semiconductor-based photocatalysts. 相似文献