Investigation of Ir-modified carbon felt as the positive electrode of an all-vanadium redox flow battery

Porous graphite felts have been used as electrode materials for all-vanadium redox flow batteries due to their wide operating potential range, stability as both an anode and a cathode, and availability in high surface area. In this paper, the carbon felt was modified by pyrolysis of Ir reduced from H₂IrCl₆. ac impedance and steady-state polarization measurements showed that the Ir-modified materials have improved activity and lowered overpotential of the desired V(IV)/V(V) redox process. Ir-modification of carbon felt enhanced the electro-conductivity of electrode materials. The Ir-material, when coated on the graphite felt electrode surface, lowered the cell internal resistance. A test cell was assembled with the Ir-modified carbon felt as the activation layer of the positive electrode, the unmodified raw felt as the activation layer of the negative electrode. At an operating current density of 20 mA cm⁻², a voltage efficiency of 87.5% was achieved. The resistance of the cell using Ir-modified felt decreased 25% compared to the cell using non-modified felt.     

Copper(I/II), α/β‐Synuclein and Amyloid‐β: Menage à Trois?

Copper binding to α‐synuclein (aS) and to amyloid‐β (Ab) has been connected to Parkinson's and Alzheimer's disease (AD), respectively, because Cu ions can modulate the peptide aggregation, and these Cu ? peptide complexes can catalyse the production of reactive oxygen species (ROS). In a significant proportion of AD brains, aggregation of aS and Ab has been detected, and it was proposed that Ab and aS interact with each other. Thus, we investigated the potential interactions of Ab and aS through their binding of copper(I) and copper(II). Additionally, β‐synuclein (bS) was investigated, due to its additional methionine residue, a potential Cu^I ligand. We found that: 1) the peptides containing the Cu‐binding domains Ab1–16, aS1–15 and bS1–15 have similar affinities towards Cu^II and towards Cu^I, with Ab1–16 being slightly stronger, 2) in the case of Cu^I, the additional Met residue in bS1–15 increased the affinity slightly, 3) the exchange of Cu^I/II between the two peptides is rapid (≤ms), 4) a/bS1–15 and Ab1–16 form a heterodimeric complex with Cu^II, 5) Cu^I probably promotes a transient ternary complex, 6) the different Cu^I/II coordination of Ab1–16, aS1–15 and bS1–15 impacts the capacity to produce ROS and to oxidise catechol, and 7) when Ab1–16, aS1–15 and Cu are present, the ROS production more closely resembles that by Ab1–16. The work gives insights into the coordination chemistry of these related peptides, and the relevance of coordination differences, the ternary complex and ROS production are discussed.     

Orthogonal Translation Meets Electron Transfer: In Vivo Labeling of Cytochrome c for Probing Local Electric Fields

Cytochrome c (cyt c), a redox protein involved in diverse fundamental biological processes, is among the most traditional model proteins for analyzing biological electron transfer and protein dynamics both in solution and at membranes. Studying the role of electric fields in energy transduction mediated by cyt c relies upon appropriate reporter groups. Up to now these had to be introduced into cyt c by in vitro chemical modification. Here, we have overcome this restriction by incorporating the noncanonical amino acid p‐cyanophenylalanine (pCNF) into cyt c in vivo. UV and CD spectroscopy indicate preservation of the overall protein fold, stability, and heme coordination, whereas a small shift of the redox potential was observed by cyclic voltammetry. The C≡N stretching mode of the incorporated pCNF detected in the IR spectra reveals a surprising difference, which is related to the oxidation state of the heme iron, thus indicating high sensitivity to changes in the electrostatics of cyt c.     

钒电解液在纳米多孔质子膜中的动态迁移规律研究

考察了不同电流密度、不同温度下电解液在纳米多孔质子膜中的迁移情况,在多次充放电循环后,钒离子与水均在负极积累,正极电解液体积线性减小,负极电解液体积线性增大,同时研究了电解液迁移对充放电容量的影响,研究表明,钒离子的跨膜迁移会导致充电与放电瓦时容量在不断衰减。     

Redox‐Active Catalyst Based on Poly(Anilinesulfonic Acid)‐ Supported Gold Nanoparticles for Aerobic Alcohol Oxidation in Water

The hybrid consisting of gold nanoparticles and poly(2‐methoxyaniline‐5‐sulfonic acid), which works as a redox mediator for transferring protons and electrons, catalyzed the oxidation reaction of various alcohols in water under molecular oxygen.     

Anaerobic Adhesive Cure Mechanism-I

Anaerobic adhesives are single-component acrylic adhesives which cure rapidly at or below room temperature when air is excluded, but they remain in an uncured stage over a long time when they are exposed to an adequate supply of air. Thus, anaerobic adhesives are widely used in retaining compounds for nuts and bolts, in sealants, and for impregnation. Recently, anaerobic adhesives have also been used in electrical and electronic applications because of their fast room temperature cure capability and their convenience.¹     

Polymerization kinetics of acrylonitrile by oxidation: Reduction system using potassium persulfate/ascorbic acid in an aqueous medium

The kinetics of acrylonitrile polymerization initiated by free radicals formed in situ in a potassium persulfate/ascorbic acid redox system was investigated in an aqueous sulfuric acid medium in the temperature range of 40–70°C. The rate of polymerization and the rate of the disappearance of potassium persulfate were measured. A kinetic scheme involving the production of initiating radicals from the oxidation of ascorbic acid by potassium persulfate ions and termination exclusively by the interaction of chain radicals with persulfate ions is proposed. The effects of some water‐miscible organic solvents on the rate of polymerization were investigated. The temperature dependence of the rate was studied. A possible mechanism consistent with the experimental data is proposed. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Cloning,Expression and Purification of Cindoxin,an Unusual Fmn‐Containing Cytochrome P450 Redox Partner

Cytochromes P450 (P450s) belong to a superfamily of haemoproteins that catalyse a remarkable variety of oxidative transformations. P450 catalysis generally requires that cognate redox proteins transfer electrons, derived ultimately from NAD(P)H, to the P450 for oxygen activation. P450_cin (CYP176A1) is a bacterial P450 that is postulated to allow Citrobacter braakii to live on cineole as its sole carbon source by initiating cineole biodegradation. Here we report the cloning, expression, purification and characterisation of one of its postulated redox partners, cindoxin (Cdx), which has strong similarity to the FMN domain of cytochrome P450 reductase. Cindoxin reductase (CdR), which displays strong similarity to NADPH‐dependent ferredoxin reductases, was unable to be expressed in a functional form. Mass spectrometric and HPLC analyses confirmed that the flavin cofactor of cindoxin was FMN. Redox potentiometric titrations were performed with cindoxin within the range 6<pH<8; this enabled the quinone/semiquinone (E₁) and semiquinone/hydroquinone (E₂) redox potentials to be determined. Our results show that cindoxin might be somewhat different to other flavodoxins that interact with P450s, in which generally only one couple is important. Both redox states of cindoxin could be catalytically relevant. A catalytically active system was reconstituted in vitro with E. coli flavodoxin reductase (Fpr) acting as the terminal redox partner in the absence of CdR. Our results show that Cdx and Fpr support regio‐ and stereoselective P450_cin‐catalysed cineole oxidation to (1R)‐6β‐hydroxycineole with turnover rates up to 1500 min^?1. This system is tightly coupled with 80 % of NADPH reducing equivalents funnelled into substrate oxidation.     

Synthesis and properties of new aromatic polyimides containing redox‐active anthraquinone moieties

A novel anthraquinone‐containing bis(ether amine) monomer, 2,6‐bis(4‐aminophenoxy)anthraquinone, was synthesized from readily available reagents. A series of novel aromatic polyimides were prepared from the newly synthesized diamine monomer with various aromatic tetracarboxylic dianhydrides. The intermediate poly(amic acid)s had inherent viscosities of 0.67–1.12 dL g^?1, and those derived from less stiff dianhydrides could be solution‐cast and thermally cyclodehydrated into flexible and tough polyimide films. The polyimides exhibited glass transition temperatures between 270 and 297 °C, and they were fairly stable up to a temperature of 500 °C in air or nitrogen. The electrochemical and electrochromic properties of one of the polyimides were investigated. The polymer could undergo two reversible steps of electrochemical reduction, with a color change from a colorless neutral state to pink and rose‐red reduced states. © 2012 Society of Chemical Industry