Polymerized ionic liquid-wrapped carbon nanotubes: The promising composites for direct electrochemistry and biosensing of redox protein

Polymerized ionic liquid-wrapped carbon nanotubes (PIL-CNTs) were firstly designed for direct electrochemistry and biosensing of redox proteins. The CNTs were coated successfully with polymerized ionic liquid (PIL) layer, as verified by transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and Fourier transform infrared (FT-IR) spectroscopy. The PIL-CNTs were dispersed better in water and showed superior electrocatalysis toward O₂ and H₂O₂ comparing to pristine CNTs and the mixture of IL monomer and CNTs. With glucose oxidase (GOD) as a protein model, the direct electrochemistry of the redox protein was investigated on the PIL-CNTs modified glassy carbon (GC) electrode and excellent direct electrochemical performance of GOD molecules was observed. The proposed biosensor (GOD/PIL-CNTs/GC electrode) displayed good analytical performance for glucose with linear response up to 6 mM, response sensitivity of 0.853 μA mM⁻¹, good stability and selectivity.     

Study on the bioactivity changes of hydroxylated sulfonylureas derivatives: A possible metabolism

Some new sulfonylureas and their hydroxylation products had been synthesized from 2-amino-4-methylpyrimidine. Their bioactivities against E. coli AHAS II in vitro were tested and the results indicated that the hydroxylation decreased the inhibition activities of sulfonylureas significantly. Subsequently herbicidal tests against stem-growth of barnyard grass and root-growth of rape confirmed the above conclusion. The preliminary molecular docking studies were also carried out to investigate the binding modes of non-hydroxylated and hydroxylated sulfonylureas with AHAS.     

Quinone-based molecular electrochemistry and their contributions to medicinal chemistry: A look at the present and future

Molecular electrochemistry is closely linked to life sciences. Electron transfers play important roles in the bioactivation of redox-active drugs, in their metabolism/catabolism, and in their targeted release at precise destinations and frequently promote their ligand–target interactions. Altogether, this rich chemistry and the complexity of cellular environments and biocompartmentation often impede full investigation in situ of the whole chain of processes that sustain their therapeutic applications. Conversely, electrochemical ex situ investigations of drug properties and interactions performed in aqueous/aprotic/micellar/membrane/cell-mimetic media, combined with in vitro and in vivo data, are expected to provide extremely useful information on these processes. Therein, considering the ubiquitous case of quinones, we exemplified how such strategies allow controlling their beneficial or negative impact on cellular environments.     

四种药物中席夫碱基团在玻碳电极上的电化学行为

选择呋喃妥因、盐酸二甲双胍、西咪替丁和醋甲唑胺4种含有席夫碱基团的常见药物,运用电化学循环伏安法对其中的-C=N-基团在玻碳电极上的电化学氧化还原行为进行了研究。呋喃妥因、盐酸二甲双胍和西咪替丁中的席夫碱基团(-CH=N-)在玻碳电极上能够被还原,而且是一个电化学的不可逆过程,其还原电位分别为-0.864V,-1.36...     

Prediction of clozapine metabolism by on-line electrochemistry/liquid chromatography/mass spectrometry

Combining electrochemical conversion, liquid chromatography and electrospray ionization mass spectrometry (EC/LC/ESI-MS) on-line allows the rapid identification of possible oxidation products of clozapine (CLZ) in the absence and in the presence of glutathione. CLZ is, depending on the applied potential, oxidized to various products in an electrochemical flow-through cell using a porous glassy carbon working electrode. Several hydroxylated and demethylated species are detected on-line using LC/MS. While hydroxy-CLZ is most abundant at a potential of 400 mV, demethylation occurs more readily at higher potentials (at around 700 mV versus Pd/H₂ reference). In the presence of glutathione (GSH), various isomeric glutathione adducts and respective products of further oxidation can be identified. The thioadducts are characterized by tandem MS. Mono-GSH and bis-GSH derivatives can be seen in the chromatograms. The results correlate well with the cyclic voltammetric profile of CLZ. The data are relevant from a pharmacological point of view, since similar metabolites (phases I and II) have been reported in the literature. The EC/LC/MS and EC/MS methods should be valuable tools that can be used to anticipate and understand the metabolization patterns of molecules of pharmacological interest and to point out reactive intermediates.     

Anthraquinone as a redox label for DNA: synthesis, enzymatic incorporation, and electrochemistry of anthraquinone-modified nucleosides, nucleotides, and DNA

Modified 2'-deoxynucleosides and deoxynucleoside triphosphates (dNTPs) bearing anthraquinone (AQ) attached through an acetylene or propargylcarbamoyl linker at the 5-position of pyrimidine (C) or at the 7-position of 7-deazaadenine were prepared by Sonogashira cross-coupling of halogenated dNTPs with 2-ethynylanthraquinone or 2-(2-propynylcarbamoyl)anthraquinone. Polymerase incorporations of the AQ-labeled dNTPs into DNA by primer extension with KOD XL polymerase have been successfully developed. The electrochemical properties of the AQ-labeled nucleosides, nucleotides, and DNA were studied by cyclic and square-wave voltammetry, which show a distinct reversible couple of peaks around -0.4 V that make the AQ a suitable redox label for DNA.     

Organic electrochemistry: Anodic construction of heterocyclic structures

The construction of heterocyclic frameworks constitutes one of the most dynamic and attractive branches in organic chemistry. Electrochemistry provides a versatile and powerful approach to assemble a heterocyclic skeleton. In this review, a selection of representative examples published during 2018–2019 are presented and discussed to showcase how to make use of anodic oxidation for the constitution of heterocyclic compounds.     

Electrochemical methods in understanding the redox processes of drugs and biomolecules and their sensing

Progression of the biochemical information of drugs and its interaction with biological substances require efficient methodologies suitable for generating information without incurring any significant damage to the analytes. Electrochemical methods provide useful information and compatible to the biological environments, without any significant alterations in the analyte, the methods are capable in onsite applications. Present review discusses about the application of the electrochemical techniques in evaluating the mechanism of interaction of drugs with the biomaterials like proteins, lipids, and DNA. The redox process leads to the determination of the drugs and biomolecules through the development of modified electrodes. The modified ultra-microelectrodes (UMEs) or nano electrodes are useful in sensing at the extracellular level of single cells. The electrochemical collision using UMEs provides information about the single molecular level. Present article discusses a brief review of some of the drug and biomolecule interactions using macro and also UMEs.     

An investigation of the role of the disparate redox states of the tetrathiafulvalene unit in modulating hydrogen bonding interactions in solution

We have investigated the electrochemically controlled hydrogen bonding interactions between tetrathiafulvalene host 3 and guests 4 or 5. Stabilisation of the 3⁺ state is dependent upon the nature of the guest species, whereas both guests prevent precipitation of the electrochemically generated 3²⁺ species at the working electrode via hydrogen bonded molecular recognition processes.     

The electrochemistry of some ferrocene derivatives: redox potential and substituent effects

Fifteen ferrocene derivatives I–IX (four of which have been prepared for the first time: II, IIIf, V and VIII) have been prepared by Friedel–Crafts acetylation, Claisen condensation, Michael reaction, and ring closure by hydrazine hydrate. The anodic behaviour of these compounds has been studied by cyclic voltammetry at a platinum electrode in an aprotic solvent. All these substituted ferrocenes exhibit a reversible one‐electron oxidation reduction centred at each iron centre, and the effect of substituents on the half‐wave oxidation potential is discussed in terms of their electronic properties. Linear correlations have been observed between these potentials and the Hammett σ_x constant for the substituents. Cyclic voltammetry has been carried out for ferrocene derivatives IIIa, V and IX. Copyright © 2003 John Wiley & Sons, Ltd.     

The Bingel monoadducts of La@C82: synthesis, characterization, and electrochemistry

The reaction of La@C82 with diethyl bromomalonate in the presence of base (the Bingel reaction) generated five monoadducts which have been fully characterized. It was found that four of them (mono-A, -B, -C, and -D) are ESR-inactive, suggesting singly bonded regioisomers. In contrast, the fifth product (mono-E) is ESR-active, indicating that it possesses a cyclic moiety between the appended malonate group and the fullerene cage, analogous to conventional Bingel adducts. The differences in the molecular structures of mono-A, -B, -C, and -E result in varying thermal stabilities and electrochemical behavior. In particular, the singly bonded monoadducts undergo the retro-Bingel reaction either under thermal treatment or during electron transfer on the cyclic voltammetric timescale. However, mono-E shows remarkable thermal stability and perfect reversibility under the same experimental conditions.     

Unveiling the relevance of the redox character of nitroaromatic and nitroheteroaromatic compounds as potential medicines

This review discusses the state of the art, challenges, and perspectives in recent applications of nitroaromatics and nitroheteroaromatics, which are redox-bio-activated drugs or leads, in Medicinal Chemistry. It deals mainly with the electrochemical approach toward the electron transfer-based molecular mechanisms of drug action, drug design, estimation and measurement of redox potentials, correlation of physicochemical and pharmacological data, and electrochemical studies of the main representatives of nitro-containing prodrugs, along with approaches to combat their toxicity issues, aiming at a better therapeutic profile. Electrochemical investigation plays essential roles, being strategic in the design and discovery of potential medicines.     

The principles of bipolar electrochemistry and its electroanalysis applications

The present study reports the wireless technique that generates asymmetric reactivity on the surface of the conducting substrate without any direct electrical connection in the electrolyte solution by inducing external power. In recent years, bipolar electrochemical systems have received special attention that they are used for new kinds of electrochemical applications ranging from electrodeposition to electroanalytical chemistry. Bipolar electrochemistry is a unique technique because of the lack of direct electrical connection to the bipolar electrode. In this perspective article, we first illustrate the concept and history of the bipolar electrochemistry as well as their application based on the open and closed bipolar configuration in different fields.     

A comparative spectroelectrochemical study of the redox electrochemistry of nitroanilines

The oxidative and reductive electrochemistry of the three isomeric nitroanilines has been studied in neutral (0.1 mol L⁻¹ KClO₄) and acidic (0.1 mol L⁻¹ HClO₄) aqueous electrolyte solutions by cyclic voltammetry and surface enhanced Raman spectroscopy (SERS). The cyclic voltammograms recorded for o- and p-nitroanilines with a gold electrode in acidic solution, scanning toward negative potentials, revealed formation of phenylenediamine not observed in neutral solution. Similar behavior of nitroanilines and phenylenediamines was observed on gold and platinum electrodes. An oxygen–gold adsorbate stretching mode was detected between 400 and 430 cm⁻¹ in the SER-spectra of the three isomeric nitroanilines in both electrolyte solutions at positive electrode potentials, implying perpendicular adsorption via the nitro group.     

CVD graphene electrochemistry: the role of graphitic islands

Graphitic islands are shown to dominate the electrochemical response at CVD grown graphene electrodes.     

Ionic liquid modified GC electrode for the direct electrochemistry of chloroperoxidase

Chloropcroxidase （CPO） was immobilized by konjac glucomannan （KGM） on the 1-butyl-3-methyl imidazolium tetrafluoroborate [BMIM][BF4]/Nafion modified glassy carbon eloctrode. The electrochemical behaviors of the immobilized CPO were investigated by cyclic voltammetry. The results showed that CPO was successfully immobilized on the GCE and underwent fast direct electron transfer reactions with the formal potential at -0.3 V vs. SCE. The modified electrode showed a good catalytic activity for elcctrocatalytical reduction of O2 and H2O2.     

Localising the electrochemistry of corrosion fatigue

The damage to a metal is significantly enhanced when simultaneously exposed to a corrosive solution and a cyclic mechanical stress. However, decoupling the contributions from each damage mechanisms is difficult. Localised electrochemical techniques, in particular scanning electrochemical microscopy (SECM), scanning electrochemical cell microscopy (SECCM), scanning kelvin probe force microscopy (SKPFM), and scanning vibrating electrode technique (SVET), can be advantageous when determining corrosion fatigue damage mechanisms and local phenomena, such as the transition between a corrosion pit and a fatigue crack. The recent corrosion fatigue literature is reviewed to highlight the usefulness of each localised electrochemical technique and how they can contribute to advancing the corrosion fatigue field.     

Use of magnetic fields in electrochemistry: A selected review

Electrochemical reactions are usually thermally activated and submitted to mass-transfer effects. Although classically, enhanced kinetics of an electrochemical reaction is obtained by heating the cell and feeding the reactant by forced convection, other means can be used to improve mass-transfer and charge-transfer. This article shortly reviews the effects of magnetic fields in electrochemistry. Using a static or an alternating magnetic field enables to enhance electrodeposition and electrocatalysis, via improved gas and species convection, electrochemical kinetics, and whole reaction efficiency. Such enhancement can mainly be related to Lorentz and Kelvin forces, magneto-hydrodynamics, chiral-induced spin selectivity, and hyperthermia, these effects being described herein.     

The solid state electrochemistry of samarium (III) hexacyanoferrate (II)

A new electroactive polynuclear inorganic compound of a rare earth metal hexacyanoferrate, samarium hexacyanoferrate (SmHCF), was prepared chemically and characterized using techniques of FTIR spectroscopy, thermogravimetric analysis (TGA), X-ray powder diffraction, UV–Vis spectrometry and X-ray photoelectron spectroscopy (XPS) etc. The cyclic voltammetric behavior of SmHCF mechanically attached to the surface of graphite electrode was well defined and exhibited a pair of redox peaks with the formal potential of 180.5 mV (versus SCE) at a scan rate of 100 mV/s in 0.2-M NaCl solution and the redox peak currents increased linearly with the square root of the scan rates up to as high as 1,000 mV/s. The effects of the concentration of supporting electrolyte on the electrochemical characteristics of SmHCF and the transport behavior of K⁺, Na⁺ and Li⁺ counter-ions through the ion channel of SmHCF were studied by voltammetry.