Characterization of micropatterned lipid membranes on a gold surface by surface plasmon resonance imaging and electrochemical signaling of a pore-forming protein

We report the fabrication and characterization of a micropatterned membrane electrode for electrochemical signaling of a bacterial pore-forming toxin, Streptolysin O (SLO) from S. pyogenes. Microcontact printing of an alkylthiol monolayer was used to fabricate an array template, onto which cholesterol-containing DMPC vesicles were fused to form lipid layer structures. The construction of the supported membranes, including pattern transfer and vesicle fusion, was characterized by in-situ surface plasmon resonance (SPR) imaging and electrochemistry. Quantitative analysis of the resulting membrane by using SPR angular shift measurements indicates that the membranes in the hydrophilic pockets have an average thickness of 8.2 +/- 0.4 nm. Together with fluorescence microscopy studies, the results suggest that this could be a mixed lipid assembly that may consist of a bilayer, vesicle fragments, and lipid junctions. The voltammetric response of the redox probe ferrocene carboxylic acid (FCA) was measured to quantify the toxin action on the supported membrane. The electrochemical measurements indicate that fusion of vesicles on the template blocked the access of FCA, whereas the injection of SLO toxin restored the redox response. The anodic peak current of FCA was found to increase with toxin concentration until a plateau was reached at 40 HU/mL. The method is highly sensitive such that 0.1 HU/mL of SLO (1.25 pM) can yield a well-defined response. In addition, it eliminates the need for a highly insulating layer in membrane sensing, which opens up new avenues in developing novel sensing interfaces for membrane-targeting proteins and peptides.     

Cover Picture: Transition‐Metal‐Free Defluorosilylation of Fluoroalkenes with Silylboronates* (Chin. J. Chem. 10/2019)

The cover picture shows a simple, inexpensive and robust method on defluorosilylation of diverse fluoroalkenes with silylboronates in the presence of alkoxy base to directly synthesize various silylated fluoroalkenes. Density functional theory calculations revealed that transient silyl anion complex undergoes S_N2’ or S_N^V substitution, which is responsible for this base‐mediated defluorosilylation reaction, thus obviating the need for copper salts. More details are discussed in the article by Shi et al. on page 1009–1014.

     

An efficient MnCl2‐catalyzed tandem acylation‐cross‐coupling reaction of o‐halobenzoyl chloride with diorganyl magnesium compounds

An efficient tandem cross‐coupling reaction of o‐chlorobenzoyl chloride with dialkyl and diaryl magnesium compounds in the presence of manganese (II) chloride was developed, which proceeds in good yield under mild conditions. Copyright © 2009 John Wiley & Sons, Ltd.     

Electrochemical Cross-Dehydrogenative Coupling between Phenols and β-Dicarbonyl Compounds: Facile Construction of Benzofurans

Preparative electrochemical synthesis is an ideal method for establishing green, sustainable processes. The major benefits of an electro-organic strategy over that of conventional chemical synthesis are the avoidance of reagent waste and mild reaction conditions. Here, an intermolecular cross-dehydrogenative coupling between phenols and β-dicarbonyl compounds has been developed to build various benzofurans under undivided electrolytic conditions. Neither transition metals nor external chemical oxidants are required to facilitate the dehydrogenation and dehydration processes. The key factor in success was the use of nBu₄NBF₄ as the electrolyte and hexafluoroisopropanol as the solvent, which play key roles in the cyclocondensation step. This electrolysis is scalable and can be used as a key step in drug synthesis. On the basis of several experimental results, the mechanism, particularly of the remarkable anodic oxidation and cyclization process, was illustrated.     

可控表面磷原子修饰提升超细W2C纳米颗粒电解水析氢反应性能

研究高活性和稳定性的非贵金属基析氢催化剂对解决当前能源危机和环境污染问题具有重要意义.碳化钨具有与贵金属Pt类似的d带电子结构,因而成为一类新兴的非贵金属析氢催化剂,受到广泛关注.磷掺杂是提高催化剂析氢活性的有效方法之一,然而目前最常见的构筑磷掺杂方法是使用多金属氧酸盐(POMs,如H3PW12O40),其固定的W/P原子比导致W2C中的掺杂浓度难以调控,并且磷掺杂主要是进入碳载体而不是碳化物本身,从而导致无法明确杂原子对其电催化析氢活性的贡献.本文采用植酸(PA)为磷源设计合成了可控磷掺杂W2C纳米颗粒,并探讨了催化剂组分、杂原子掺杂位置与析氢性能之间的关系.深入研究了磷掺杂碳化钨(WCP)的化学结构和析氢活性.与原始的W2C催化剂相比,WCP具有更高的本征活性、更快的电子转移速率和更多的活性位数量,并且在酸性和碱性条件下均表现出较好的析氢性能.特别是过电位为-200 mV时,WCP催化剂的本征活性在酸性和碱性条件下分别为0.07和0.56 H2 s-1,高出纯W2C(0.01和0.05 H2 S-1)数倍.同时,在电流密度为-10 mA cm-2时,优化后的WCP催化剂在酸性和碱性条件下的析氢过电位分别降低了96和88 mV.XPS及EDS元素分析结果表明,随磷源添加量增加,磷掺杂从碳化钨表面逐渐向内部扩散,进一步说明磷取代位置与析氢活性之间的构效关系,高浓度的表面磷取代可以加速质子捕获过程,从而显著提高其析氢活性,而过量的内部磷取代会破坏W2C结构,降低电子转移速率,从而导致析氢性能下降.利用密度泛函理论计算深入研究了WCP具有较好析氢性能的原因,与内部磷取代相比,表面磷取代会使碳化钨表现出更合适的氢吸附自由能,并且更加有效地降低了氢释放势垒,从而优化了析氢反应动力学.综上,本文为元素掺杂工艺提供了新的思路,同时研究了表面异质原子对析氢活性的关键作用,为该类催化材料的构效关系研究提供了新思路.     

Radical Addition Enables 1,2‐Aryl Migration from a Vinyl‐Substituted All‐Carbon Quaternary Center

An efficient method for photocatalytic perfluoroalkylation of vinyl‐substituted all‐carbon quaternary centers involving 1,2‐aryl migration has been developed. The rearrangement reactions use fac‐Ir(ppy)₃, visible light and commercially available fluoroalkyl halides and can generate valuable multisubstituted perfluoroalkylated compounds in a single step that would be challenging to prepare by other methods. Mechanistically, the photoinduced alkyl radical addition to an alkene leads to the migration of a vicinal aryl substituent from its adjacent all‐carbon quaternary center with the concomitant generation of a C‐radical bearing two electron‐withdrawing groups that is further reduced by a hydrogen donor to complete the domino sequence.     

Recent advances in transition-metal catalyzed reactions using molecular oxygen as the oxidant

For green and sustainable chemistry, molecular oxygen is considered as an ideal oxidant due to its natural, inexpensive, and environmentally friendly characteristics, and therefore offers attractive academic and industrial prospects. This critical review introduces the recent advances over the past 5 years in transition-metal catalyzed reactions using molecular oxygen as the oxidant. This review highlights the scope and limitations, as well as the mechanisms of these oxidation reactions (184 references).     

Transition‐metal‐catalyzed Chelation‐assisted C–H Functionalization of Aromatic Substrates

In the past decade, transition‐metal‐catalyzed C–H activations have been very popular in the research field of organometallic chemistry, and have been considered as efficient and convenient strategies to afford complex natural products, functional advanced materials, fluorescent compounds, and pharmaceutical compounds. In this account, we begin with a brief introduction to the development of transition‐metal‐catalyzed C–H activation, especially the development of transition‐metal‐catalyzed chelation‐assisted C–H activation. Then, a more detailed discussion is directed towards our recent studies on the transition‐metal‐catalyzed chelation‐assisted oxidative C–H/C–H functionalization of aromatic substrates bearing directing functional groups.     

光纤耦合的全固态中红外QEPAS光声探测模块

石英增强光声光谱(QEPAS)技术是近年来发展迅速的一种气体检测技术,具有灵敏度高、设备体积小、对环境噪声免疫等优点.本课题组设计了一种光纤耦合的全固态中红外QEPAS光声探测模块,并基于气体热动力学和一维声学谐振腔理论,利用COMSOL软件对探测模块的声压分布及声压级进行了研究;然后设计并加工了光机电一体化探测模块,...