Predictable site-selective radical fluorination of tertiary ethers

In this communication,we disclose the first example of metal-free and site-selective radical fluorination of readily available tertiary alkyl ethers,enabled by synergistic photocatalysis and organocatalysis.This catalytic combination allows for exclusive fluorination of tertiary C–O bonds under mild conditions even in the presence of competing reaction sites.The excellent functional group tolerance affords valuable access to sterically hindered alkyl fluorides through late-stage modification of complex molecules.The successful use of tertiary alkyl ethers in radical fluorination enhances the structural diversity of aliphatic fluorides that can be derived from naturally abundant alcohols.     

固相萃取-液相色谱-质谱/质谱法同时测定蜂蜜中的多类药物残留

建立了采用固相萃取-液相色谱-质谱/质谱(SPE-LC-MS/MS)对蜂蜜中磺胺类、硝基咪唑类、喹诺酮类、大环内酯类、林可酰胺类和吡喹酮共计6大类54种药物残留同时测定的方法。蜂蜜经磷酸盐缓冲溶液(pH 8)稀释,Oasis HLB固相萃取柱净化后,通过液相色谱-质谱联用技术进行检测(正离子方式,多反应监测模式)。采用同位素稀释内标法或外标法进行定量,线性关系良好,相关系数大于0.992。方法的定量限(LOQ,以信噪比(S/N)大于10计)分别为磺胺类和硝基咪唑类药物1.0 μg/kg,喹诺酮类和林可酰胺类药物2.0 μg/kg,大环内酯类药物3.0 μg/kg,吡喹酮0.3 μg/kg。总体回收率为32.6%～114%,相对标准偏差为1.3%～28.9%。该方法的定量限满足目前国内外药物的最大残留限量要求,可作为蜂蜜中相关药物残留量的筛选检测方法。     

叶栅边界层转捩的实验研究与一个新的综合经验准则

叶栅边界层转捩的实验研究与一个新的综合经验准则蒋洪德，仲永兴，凌君（中国科学院工程热物理研究所北京１０００８０）（中国航空工业总公司６２４所）关键词转捩实验，经验准则１前言现代航空发动机的风扇、压气机和涡轮叶栅在工作状态下弦长雷诺数一般在１０５～１０...     

Chiral Brønsted acid-catalyzed Friedel–Crafts reaction of 3-indolylsulfamidates with indoles: Synthesis of enantioenriched bisindolylmethane sulfamates

A Brønsted acid-catalyzed asymmetric Friedel–Crafts alkylation of 3-indolylsulfamidates with indoles has been established toward the efficient synthesis of biologically important bisindolylarylmethane derivatives containing the phenylsulfamate group. The reaction using chiral BINOL-derived phosphoric acid as the catalyst was tolerant to a diverse range of 3-indolylsulfamates and indoles, and provided for the first time bisindolylarylmethane sulfamate derivatives in good yields and with moderate to high enantioselectivities (up to 89% yield, 94:6 er). Moreover, some of these novel compounds were evaluated for their biological activities and confirmed to show bioactivity for preventing peripheral nerve degeneration.     

Light‐Driven Reversible Intermolecular Proton Transfer at Single‐Molecule Junctions

Photoresponsive molecular systems are essential for molecular optoelectronic devices, but most molecular building blocks are non‐photoresponsive. Employed here is a photoinduced proton transfer (PIPT) strategy to control charge transport through single‐molecule azulene junctions with visible light under ambient conditions, which leads to a reversible and controllable photoresponsive molecular device based on non‐photoresponsive molecules and a photoacid. Also demonstrated is the application of PIPT in two single‐molecule AND gate and OR gate devices with electrical signal as outputs.     

Highly insulating alkane rings with destructive σ-interference

Science China Chemistry - Destructive quantum interference (DQI) provides a unique approach to controlling the leakage current in the OFF state of molecular devices. However, the DQI in...     

关于一道反常积分习题的探讨

对华东师范大学数学系编写的数学分析教材以及陈纪修等编写的数学分析教材课后一道反常积分习题给出反例,并通过增加条件,得到正确结论.     

Protein-templated Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> microspheres for highly sensitive amperometric detection of dopamine

The authors describe an amperometric sensor for dopamine (DA) by employing olive-like Fe₂O₃ microspheres (OFMs) as the electrocatalyst for DA oxidization. The OFMs were prepared by using a protein templated method. The structure and properties of the OFMs were characterized by scanning electron microscopy, X-ray powder diffraction, energy dispersive x-ray spectroscopy, cyclic voltammetry and electrochemical impedance spectroscopy. The OFMs possess excellent catalytic activity towards DA oxidization due to their unique morphology. The sensor responds to DA within less than 5 s. The sensor, best operated at a voltage of +0.2 V (vs. SCE) responds linearly in the 0.2 to 115 μM DA concentration range and has a 30 nM detection limit. The selectivity, reproducibility and long-term stability of the sensor are acceptable. It performs well when applied to spiked human urine samples.

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Graphical abstract Olive-like Fe₂O₃ microspheres (OFMs), synthesized using egg white as template, display excellent catalytic activity towards dopamine (DA) oxidization due to their unique morphology. They were applied for DA detection using the amperometric technique. The electrochemical sensor exhibited a high sensitivity and a 30 nM detection limit. DAQ: dopaquinone.

     

铈基介孔金属有机骨架固定化酶的构建及催化性能

金属有机骨架(MOF)材料由于其孔隙率高、比表面积大以及具有发达的内联通孔道结构等优点,可以作为优良的生物分子固定化载体。通过表面活性自组装策略制备了铈基介孔MOF(Ce-MOF-F),表征结果表明,该材料有大的比表面积和呈辐射状的介孔孔道结构。以其为载体、南极假丝酵母脂肪酶B(CALB)为模型酶,通过物理吸附法制备了生物催化剂CALB@Ce-MOF-F,对该固定化酶的酶载量和催化性能进行了研究。在优化条件下,CALB的负载量为162.0mg/g载体,水解活性为899.1U/g蛋白。与游离CALB相比,CALB@Ce-MOF-F表现出对高温、酸碱和有机溶剂等有更强的耐受性;将Ce-MOF-F用于多种酶的固定化,研究其作为载体的普适性,结果表明,介孔Ce-MOF-F对洋葱伯克氏菌脂肪酶(BCL)和漆酶有良好的固定效果,可以作为良好载体,并能对酶起到较好的保护作用。