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Chemical Remodeling of Cell‐Surface Sialic Acids through a Palladium‐Triggered Bioorthogonal Elimination Reaction 下载免费PDF全文
Jie Wang Bo Cheng Jie Li Zhaoyue Zhang Weiyao Hong Prof. Dr. Xing Chen Prof. Dr. Peng R. Chen 《Angewandte Chemie (International ed. in English)》2015,54(18):5364-5368
We herein report a chemical decaging strategy for the in situ generation of neuramic acid (Neu), a unique type of sialic acid, on live cells by the use of a palladium‐mediated bioorthogonal elimination reaction. Palladium nanoparticles (Pd NPs) were found to be a highly efficient and biocompatible depropargylation catalyst for the direct conversion of metabolically incorporated N‐(propargyloxycarbonyl)neuramic acid (Neu5Proc) into Neu on cell‐surface glycans. This conversion chemically mimics the enzymatic de‐N‐acetylation of N‐acetylneuramic acid (Neu5Ac), a proposed mechanism for the natural occurrence of Neu on cell‐surface glycans. The bioorthogonal elimination was also exploited for the manipulation of cell‐surface charge by unmasking the free amine at C5 to neutralize the negatively charged carboxyl group at C1 of sialic acids. 相似文献
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Laura Asturias‐Arribas Mario Raúl Delfino M. Asunción Alonso‐Lomillo Olga Domínguez‐Renedo M. Julia Arcos‐Martínez 《Electroanalysis》2016,28(9):2081-2086
This paper describes the voltammetric study of the electrochemical oxidation of the antiretroviral drug Nelfinavir using a screen‐printed sensor modified with carbon nanotubes. The performance of the sensor in the determination of the drug was characterized in terms of precision (RSD 5.05 %, n=5) and capability of detection (10.99±0.87 μM for α=β=0.05, n=5) under optimized voltammetric conditions of pH, accumulation time and potential, in the calibration range from 10 to 150 μM of NFV. In order to check the viability of the device, the determination of the analyte in pharmaceutical and biological samples was carried out and its performance was also validated comparing it with HPLC. 相似文献
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Stefan Popovi Milutin Smiljani Primo Jovanovi
Jan Vavra Raffaella Buonsanti Nejc Hodnik 《Angewandte Chemie (International ed. in English)》2020,59(35):14736-14746
To date, copper is the only monometallic catalyst that can electrochemically reduce CO2 into high value and energy‐dense products, such as hydrocarbons and alcohols. In recent years, great efforts have been directed towards understanding how its nanoscale structure affects activity and selectivity for the electrochemical CO2 reduction reaction (CO2RR). Furthermore, many attempts have been made to improve these two properties. Nevertheless, to advance towards applied systems, the stability of the catalysts during electrolysis is of great significance. This aspect, however, remains less investigated and discussed across the CO2RR literature. In this Minireview, the recent progress on understanding the stability of copper‐based catalysts is summarized, along with the very few proposed degradation mechanisms. Finally, our perspective on the topic is given. 相似文献
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Direct‐methanol Fuel Cell Based on Functionalized Graphene Oxide with Mono‐metallic and Bi‐metallic Nanoparticles: Electrochemical Performances of Nanomaterials for Methanol Oxidation 下载免费PDF全文
Mehmet Lütfi Yola Tanju Eren Necip Atar Hasan Saral İsmail Ermiş 《Electroanalysis》2016,28(3):570-579
The catalysts based on 2‐aminoethanethiol functionalized graphene oxide (AETGO) with several mono‐metallic and bi‐metallic nanoparticles such as rod gold (rAuNPs), rod silver (rAgNPs), rod gold‐platinum (rAu‐Pt NPs) and rod silver‐platinum (rAg‐Pt NPs) were synthesized. The successful synthesis of nanomaterials was confirmed by various methods. The effective surface area (ESA) of the rAu‐Pt NPs/AETGO is 1.44, 1.64 and 2.40 times higher than those of rAg‐Pt NPs/AETGO, rAuNPs/AETGO and rAgNPs/AETGO, respectively, under the same amount of Pt. The rAu‐Pt NPs/AETGO exhibited a higher peak current for methanol oxidation than those of comparable rAg‐Pt NPs/AETGO under the same amount of Pt loading. 相似文献
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Ting‐Hao Yang Chun‐Yen Liao Jen‐Lin Chang Chien‐Hung Lien Jyh‐Myng Zen 《Electroanalysis》2009,21(21):2390-2394
A simple electrochemical approach to evaluate oxygen reduction catalysts using an inexpensive screen‐printed ring disk carbon electrode system, consisting of a ring electrode deposited with MnO2 and a disk electrode modified with the catalysts for study, is developed in this study. The as‐prepared MnO2 is selective and sensitive for H2O2 oxidation in the presence of O2 and is crucial to the proposed approach. By coupling with a wall‐jet electrochemical cell, the product generated from the reduction reaction at the disk electrode can effectively be monitored at the MnO2‐deposited ring electrode. Model catalysts of nano‐Au and nano‐Pd representing 2e? reduction of O2 to H2O2 and 4e? reduction to H2O, respectively, were evaluated as electrode materials in oxygen reduction reaction to demonstrate the applicability of the proposed method. 相似文献
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A novel, simple and relative highly sensitive amperometric flow biosensor for cyanide was developed by using horseradish peroxidase (HRP)‐adsorbed carbon‐felt (CF), based on an inhibitory effect on the HRP‐catalyzed O2 reduction. The HRP‐CF showed a sufficient bioelecrocatalytic activity for O2 reduction in the potential region from 0 to ?0.5 V at pH 5.0, due to a direct electron transfer‐based O2 reduction process via ferrous‐HRP and compound III. This HRP‐catalyzed O2 reduction was reversibly inhibited by cyanide, which enabled to fabricate a novel and simple reagentless (i.e., no requirement of the ordinary substrate, H2O2, and the electron transfer mediators) flow‐biosensor for cyanide. When air‐saturated 0.1 M phosphate buffer (pH 5.0) was used as a carrier under the applied potential of ?0.2 V vs. Ag/AgCl, the steady‐state base‐current due to the HRP‐catalyzed O2 reduction was reversibly inhibited by the cyanide injection (200 µL), resulting in peak‐shape current responses. The magnitude of the inhibition peak currents linearly increased with increasing concentrations of cyanide up to 1 µM, and the detection limit was found to be 0.04 µM (S/N=2). The apparent inhibition constant Ki′ was estimated to be 0.87 µM. 相似文献
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Dongni Liu Dongyun Chen Najun Li Qingfeng Xu Hua Li Jinghui He Jianmei Lu 《Angewandte Chemie (International ed. in English)》2020,59(11):4519-4524
BiOBr containing surface oxygen vacancies (OVs) was prepared by a simple solvothermal method and combined with graphitic carbon nitride (g‐C3N4) to construct a heterojunction for photocatalytic oxidation of nitric oxide (NO) and reduction of carbon dioxide (CO2). The formation of the heterojunction enhanced the transfer and separation efficiency of photogenerated carriers. Furthermore, the surface OVs sufficiently exposed catalytically active sites, and enabled capture of photoexcited electrons at the surface of the catalyst. Internal recombination of photogenerated charges was also limited, which contributed to generation of more active oxygen for NO oxidation. Heterojunction and OVs worked together to form a spatial conductive network framework, which achieved 63 % NO removal, 96 % selectivity for carbonaceous products (that is, CO and CH4). The stability of the catalyst was confirmed by cycling experiments and X‐ray diffraction and transmission electron microscopy after NO removal. 相似文献
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Isolation of Functionalized Phenolic Monomers through Selective Oxidation and CO Bond Cleavage of the β‐O‐4 Linkages in Lignin 下载免费PDF全文
Christopher S. Lancefield Dr. O. Stephen Ojo Dr. Fanny Tran Prof. Nicholas J. Westwood 《Angewandte Chemie (International ed. in English)》2015,54(1):258-262
Functionalized phenolic monomers have been generated and isolated from an organosolv lignin through a two‐step depolymerization process. Chemoselective catalytic oxidation of β‐O‐4 linkages promoted by the DDQ/tBuONO/O2 system was achieved in model compounds, including polymeric models and in real lignin. The oxidized β‐O‐4 linkages were then cleaved on reaction with zinc. Compared to many existing methods, this protocol, which can be achieved in one pot, is highly selective, giving rise to a simple mixture of products that can be readily purified to give pure compounds. The functionality present in these products makes them potentially valuable building blocks. 相似文献
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4‐Benzamido‐TEMPO catalyzed oxidation system for conversion of a wide range of alcohols to the aldehydes or ketones with NaBrO3 under room temperature conditions has been developed. The credible, operationally convenient and economical, and condition mild oxidation protocol is particularly of interest in laboratory and in fine chemicals manufacture. 相似文献
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Controlling the Selectivity of the Surface Plasmon Resonance Mediated Oxidation of p‐Aminothiophenol on Au Nanoparticles by Charge Transfer from UV‐excited TiO2 下载免费PDF全文
Dr. Jiale Wang Prof. Dr. Romulo A. Ando Prof. Dr. Pedro H. C. Camargo 《Angewandte Chemie (International ed. in English)》2015,54(23):6909-6912
Although catalytic processes mediated by surface plasmon resonance (SPR) excitation have emerged as a new frontier in catalysis, the selectivity of these processes remains poorly understood. Here, the selectivity of the SPR‐mediated oxidation of p‐aminothiophenol (PATP) employing Au NPs as catalysts was controlled by the choice of catalysts (Au or TiO2‐Au NPs) and by the modulation of the charge transfer from UV‐excited TiO2 to Au. When Au NPs were employed as catalyst, the SPR‐mediated oxidation of PATP yielded p,p‐dimercaptobenzene (DMAB). When TiO2‐Au NPs were employed as catalysts under both UV illumination and SPR excitation, p‐nitrophenol (PNTP) was formed from PATP in a single step. Interestingly, PNTP molecules were further reduced to DMAB after the UV illumination was removed. Our data show that control over charge‐transfer processes may play an important role to tune activity, product formation, and selectivity in SPR‐mediated catalytic processes. 相似文献
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Tetsuya Ono Katsuhiko Sato Yusuke Sasano Kentaro Yoshida Takenori Dairaku Yoshiharu Iwabuchi Yoshitomo Kashiwagi 《Electroanalysis》2019,31(4):603-606
This work investigated a simple triglycerides (TGs) detection method combining an enzymatic reaction, using only lipase, and the electrocatalytic oxidation of glycerol with nortropine‐N‐oxyl (NNO). Tributyrin was employed as a model TG. In this method, TGs are degraded by lipase to glycerol and fatty acids, after which the glycerol reacts with NNO. Preliminary cyclic voltammetry trials demonstrated that the anodic peak current increased along with the glycerol concentration, giving currents of 53.2 and 97.3 μA (at +0.6 V vs. Ag/AgCl) in response to 10 and 100 mM glycerol, respectively. Amperometry confirmed the same response during constant potential electrolysis at+0.6 V vs. Ag/AgCl. This behavior was also observed in a system incorporating tributyrin and lipase, with increases in current proportional to the tributyrin concentration over the range of 0.1 to 10 mM. 相似文献
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Alumina‐former coatings have been known as the best surface engineering approach to combat high temperature corrosion in gas turbine industry. In this investigation, attempts have been made to obtain a titanium‐modified aluminide coating with improved protective properties. Modification has been achieved by introducing titanium in the coating composition by a two‐stage coating treatment; titanium coating and subsequent aluminising. The modified coatings were characterised and compared with simple aluminides by means of electron metallography, depth elemental profiling and x‐ray diffraction techniques. Experimental results indicated that pre‐titanising diffusion treatment is an effective route to modify chemical composition of simple aluminide coating. The final microstructure of the coating was β‐NiAl matrix with titanium‐bearing precipitates mainly distributed in near surface layers. The mechanism of the coating formation is discussed. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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Surface oxidation process of a diamond‐like carbon film analyzed by difference X‐ray photoelectron spectroscopy 下载免费PDF全文
Difference X‐ray photoelectron spectroscopy (D‐XPS) revealed the surface oxidation process of a diamond‐like carbon (DLC) film. Evaluation of surface functional groups on DLC solely by the C 1s spectrum is difficult because the spectrum is broad and has a secondary asymmetric lineshape. D‐XPS clarified the subtle but critical changes at the DLC surface caused by wet oxidation. The hydroxyl (C―OH) group was dominant at the oxidized surface. Further oxidized carbonyl (C?O) and carboxyl (including carboxylate) (COO) groups were also obtained; however, the oxidation of C?O to COO was suppressed to some extent because the reaction required C―C bond cleavage. Wet oxidation cleaved the aliphatic hydrogenated and non‐hydrogenated sp2 carbon bonds (C―H sp2 and C―C sp2) to create a pair of C―OH and hydrogenated sp3 carbon (C―H sp3) bonds. The reaction yield for C―H sp2 was superior at the surface, suggesting that the DLC film was hydrogen rich at the surface. Oxidation of aromatic sp2 rings or polycyclic aromatic hydrocarbons such as nanographite to phenols did not occur because of their resonance stabilization with electron delocalization. Non‐hydrogenated sp3 carbon (C―C sp3) bonds were not affected by oxidation, suggesting that these bonds are chemically inert. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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Multi‐Electron Oxygen Reduction by a Hybrid Visible‐Light‐Photocatalyst Consisting of Metal‐Oxide Semiconductor and Self‐Assembled Biomimetic Complex 下载免费PDF全文
Dr. Shin‐ichi Naya Tadahiro Niwa Ryo Negishi Prof. Dr. Hisayoshi Kobayashi Prof. Dr. Hiroaki Tada 《Angewandte Chemie (International ed. in English)》2014,53(50):13894-13897
Adsorption experiments and density functional theory (DFT) simulations indicated that Cu(acac)2 is chemisorbed on the monoclinic sheelite (ms)‐BiVO4 surface to form an O2‐bridged binuclear complex (OBBC/BiVO4) like hemocyanin. Multi‐electron reduction of O2 is induced by the visible‐light irradiation of the OBBC/BiVO4 in the same manner as a blue Cu enzyme. The drastic enhancement of the O2 reduction renders ms‐BiVO4 to work as a good visible‐light photocatalyst without any sacrificial reagents. As a model reaction, we show that this biomimetic hybrid photocatalyst exhibits a high level of activity for the aerobic oxidation of amines to aldehydes in aqueous solution and imines in THF solution at 25 °C giving selectivities above 99 % under visible‐light irradiation. 相似文献
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Controllable Release and High‐Efficiency Collection of Hydrogen Peroxide: Application on the Quantitative Investigation of Biomolecule Oxidation Induced by Reactive Oxygen Species 下载免费PDF全文
Hydrogen peroxide and hydroxyl radical, both important members of the reactive oxygen species (ROS) family, can cause serious oxidative damages in biological systems. In order to proclaim and prevent oxidation stress, researches on the biomolecule oxidation induced by H2O2 or OH. are in crucial need. However, due to the high reactivity of ROS, traditional methods are difficult to achieve the in situ quantitative investigations on those reactions involving ROS. In this work, using scanning electrochemical microscopy technique (SECM) in a tip generation‐substrate collection mode (TG‐SC), the controllable release and the high‐efficiency collection of electrogenerated H2O2 were achieved. Compared to ex situ fluorescence method, SECM improved the collection efficiency approximately two times larger. Based on it, SECM combined with surface plasmon resonance (SPR) was employed to in situ monitor the protein oxidation (taking Cu12+? MT as a model) induced by H2O2. OH., which was generated from the interaction between H2O2 and Cu12+? MT, can attack the peptide chain and induced the unrepairable protein oxidation damage. The whole process was quantitatively characterized by SPR, and the linear relationship between SPR dip shift and the amounts of released H2O2 was successfully built. Our work proves that the combined SECM‐SPR technique can realize the in situ quantitative determinations of the biomolecule oxidation induced by ROS, which affords an avenue for further elucidation on the mechanisms of oxidation stress in organisms. 相似文献