Redox-active Transition Metal Research Articles

Elucidation of key antioxidant components in red wine via challenge with a range of oxidants using an HPLC comparison to faux wine

The purported health benefits of red wine owing to its antioxidant capacity attract persistent attention. The aims of this study were (1) to explore the contribution of individual phenolic constituents to the antioxidant capacity of red wine and (2) to investigate if non-phenolic components have oxidant or antioxidant effects. Red wine and a faux wine model systems of 11 constituent phenolic compounds were challenged with increasing concentrations of selected oxidants, namely hydrogen peroxide, redox-active transition metal ions and Fenton systems. Antioxidant activity was assessed through loss of phenolic components upon oxidant challenge measured using a reversed-phase high-performance liquid chromatography (HPLC) method. Elemental analysis of the red wine showed that the concentration of metal ions was in the range of 0.01–1.11 mM, whereas the concentration of antioxidant phenolics in the wine was in the range of 0.10–4.40 mM. As expected, addition of all five oxidant systems to both red wine and faux wine resulted in considerable loss of phenolics as quantified by HPLC. However, the pattern of phenolic loss was largely similar for both red wine and the faux wine across the five oxidant systems (frequently ca. 50–60% with the initial addition of oxidant), with only marginal effects on antioxidant activity after further additions of oxidants. The data revealed that the non-phenolic wine constituents had little influence over oxidative processes under the conditions studied, suggesting that the antioxidant properties observed in the tested red wine could be attributable to the phenolics.

PEDOT: PSS as a Functional Binder for Cathodes in Lithium Ion Batteries

The application areas of rechargeable Li-ion batteries continue to grow, hence improvement in their energy density, rate capability and cycle life is necessary. A typical cathode contains usually redox active transition metal oxides as active materials, conductive additives to ensure electronic conductivity and binder supporting matrix. In this work we report the behavior and properties of carbon black free LiFePO4 composite electrode, where poly (3,4-ethylene dioxythiophene): poly (styrene sulfonate) (PEDOT:PSS) is accomplishing a dual role of binder and conducting additive. The effect of the polymer amount on the morphometric properties of the electrodes was studied using SEM, mercury porosimetry and high resolution X-ray computed tomography. The electrochemical performance and the cycling stability of the composite electrodes were compared to the behavior of conventional cathodes with carbon additives and PVDF binder. With increasing PEDOT:PSS content a decrease in the overvoltage and correspondingly an improvement in the rate capability is observed. Composite cathodes containing 8% PEDOT:PSS show comparable electrode capacity and better cyclic stability than conventional composite cathode.

Stabilization of Battery Electrode/Electrolyte Interfaces Employing Nanocrystals with Passivating Epitaxial Shells

Chemical degradation at electrode/electrolyte interfaces in high-energy storage devices, such as Li-ion batteries, imposes durability challenges that affect their life and cost. In oxide electrodes, degradation is linked to the presence of redox active transition metals at the surface. Here, we demonstrate a strategy toward the stabilization of interfaces using core–epitaxial shell nanocrystals. The core of the nanocrystal is composed of an electroactive oxide, which is passivated by an ultrathin epitaxial oxide shell enriched in a redox inactive ion. This approach imparts interfacial stability while preserving the high storage capability and fast carrier transport of the material, compared to unmodified versions. The validity of the concept is proved with Li1+xMn2–xO4 nanocrystals with a 1–2 nm Al-rich shell, which showed reduced sensitivity to harsh environments, compared to bare counterparts. The approach is generalizable to any transition-metal-based battery system where electrode–electrolyte interact...

Human recombinant cytochrome P450 enzymes display distinct hydrogen peroxide generating activities during substrate independent NADPH oxidase reactions.

Microsomal enzymes generate H2O2 in the presence of NADPH. In this reaction, referred to as "oxidase" activity, H2O2 is generated directly or indirectly via the formation of superoxide anion. In the presence of redox active transition metals, H2O2 can form highly toxic hydroxyl radicals and, depending on the "oxidase" activity of individual cytochrome P450 isoenzymes, this can compromise cellular functioning and contribute to tissue injury. In the present studies, we compared the initial rates of H2O2 generating activity of microsomal preparations containing various human recombinant cytochromes P450s. In the absence of cytochrome P450s the human recombinant NADPH cytochrome P450 reductase (CPR) generated low, but detectable amounts of H2O2 (∼0.04 nmol H2O2/min/100 units of reductase). Significantly greater activity was detected in preparations containing individual cytochrome P450s coexpressed with CPR (from 6.0 nmol H2O2/min/nmol P450 to 0.2 nmol/min/nmol P450); CYP1A1 was the most active, followed by CYP2D6, CYP3A4, CYP2E1, CYP4A11, CYP1A2, and CYP2C subfamily enzymes. H2O2 generating activity of the cytochrome P450s was independent of the ratio of CYP/CPR. Thus, similar H2O2 generating activity was noted with the same cytochrome P450s (CYP3A4, CYP2E1, and CYP2C9) expressed at or near the ratio of CYP/CPR in human liver microsomes (5-7), and when CPR was present in excess (CYP/CPR = 0.2-0.3). Because CYP3A4/5/7 represent up to 40% of total cytochrome P450 in the liver, these data indicate that these enzymes are the major source of H2O2 in human liver microsomes.

Elucidating self-assembly mechanisms of uranyl-peroxide capsules from monomers.

Self-assembly of uranyl peroxide polyoxometalates (POMs) in alkaline peroxide solutions has been known for almost a decade, but in these dynamic solutions that contain high concentrations of base and peroxide the reaction pathway could never be discerned, mixed species are obtained, and reproducibility is sometimes a challenge. Here we elucidate the reaction mechanisms utilizing self-assembly of the U24 cluster, [UO2(O2)(OH)]24(24-), from monomers as a model system. Using Raman as our main spectroscopic probe, we learned that the monomeric species is persistent in water at room temperature indefinitely. However, if a redox-active transition metal catalyst (copper (Cu(2+)) or cobalt (Co(2+))) is added, self-assembly is accelerated in a significant manner, forming U24 peroxide clusters in several hours, which is a good time scale for studying reaction mechanisms. From semiquantitative treatment of the spectroscopic data, we elucidate reaction mechanisms that are consistent with prior structural and computational studies that suggest uranyl peroxide rings templated by alkalis are the building units of clusters. By understanding aqueous speciation and processes, we are moving toward assuming control over cluster self-assembly that has been mastered for decades now in the analogous transition-metal POM systems.

The Effect of Composition, Size, and Solubility on Acute Pulmonary Injury in Rats Following Exposure to Mexico City Ambient Particulate Matter Samples

Particulate matter (PM)-associated metals can contribute to adverse cardiopulmonary effects following exposure to air pollution. The aim of this study was to investigate how variation in the composition and size of ambient PM collected from two distinct regions in Mexico City relates to toxicity differences. Male Wistar Kyoto rats (14 wk) were intratracheally instilled with chemically characterized PM10 and PM2.5 from the north and PM10 from the south of Mexico City (3 mg/kg). Both water-soluble and acid-leachable fractions contained several metals, with levels generally higher in PM10 South. The insoluble and total, but not soluble, fractions of all PM induced pulmonary damage that was indicated by significant increases in neutrophilic inflammation, and several lung injury biomarkers including total protein, albumin, lactate dehydrogenase activity, and γ-glutamyl transferase activity 24 and 72 h postexposure. PM10 North and PM2.5 North also significantly decreased levels of the antioxidant ascorbic acid. Elevation in lung mRNA biomarkers of inflammation (tumor necrosis factor [TNF]-α and macrophage inflammatory protein [MIP]-2), oxidative stress (heme oxygenase [HO]-1, lectin-like oxidized low-density lipoprotein receptor [LOX]-1, and inducibile nitric oxide synthase [iNOS]), and thrombosis (tissue factor [TF] and plasminogen activator inhibitor [PAI]-1), as well as reduced levels of fibrinolytic protein tissue plasminogen activator (tPA), further indicated pulmonary injury following PM exposure. These responses were more pronounced with PM10 South (PM10 South > PM10 North > PM2.5 North), which contained higher levels of redox-active transition metals that may have contributed to specific differences in selected lung gene markers. These findings provide evidence that surface chemistry of the PM core and not the water-soluble fraction played an important role in regulating in vivo pulmonary toxicity responses to Mexico City PM.

Magnetic Structure and Properties of NaFePO4 Polymorphs: Antiferromagnetic Ordering and Spin-Flop Transition

In recent years, the cost and sustainability concerns have renewed research efforts on sodium-ion batteries, propelling investigation on various layered oxides and polyanionic family of insertion compounds for low-cost and large-scale cathode applications. These cathode insertion compounds are functional materials, involving redox active 3d transition metals (e.g. Fe/Co/Ni) that are often magnetic in nature. During the Na (de)insertion process involving redox reaction of transition metals and structural alteration, the magnetic magnetic structure/ properties can vary significantly.We have investigated the magnetic structure and properties of NaFePO4 polyanionic system, which exists in two distinct polymorphs: metastable triphylite and stable maricite. The details of these structures are shown in the figure. Both these polymoprhs undergo antiferromagnetic ordering below 50 K (for triphylite) and 13 K (for maricite). Using the magnetic susceptibility, heat capacity and low temperature neutron powder diffraction, the magnetic structure of these two distinct polymorphs have been solved. The details of these antiferromagnetic structures will be described considering the super- and super-superexchange interactions. In addition, investigating the maricite NaFePO4 polymorph, which consists of edge-sharing FeO6 octahedral chains, we have discovered the occurrence of spin-flop transition below 40 kOe using susceptibility measurement and low-temperature Mossbauer spectroscopy. This spin-flopping (or metamagnetism) phenomenon in maricite NaFePO4 will be described in detail [1-5] to showcase the rich magnetism present in NaFePO4 insertion materials.

Multinuclear Solid-State NMR Studies of Cathode Materials for Lithium and Sodium Ion Batteries

Lithium ion batteries have long been promised as an alternative energy technology, owing to their high volumetric and gravimetric energy densities.1 The cathode (positive electrode) material is of particular importance as the choice of this component can dictate overall battery performance. Polyanionic structural frameworks such as phosphates or fluorosulfates are an attractive alternative to the traditional layered oxide cathode structures due to their high electrochemical and thermal stability.2 More recently, the reconsideration of sodium ion batteries has become popular, and while the larger, heavier, sodium ion decreases overall energy density for a given material vs. Li, the cost and abundance benefits are expected to largely outweigh this disadvantage.3 Despite considerable research efforts to improve cathode materials for both lithium and sodium ion batteries, the role of structure on ion mobility is not yet fully understood; a property integral to electrochemical success.Solid-state nuclear magnetic resonance (ssNMR) is a valuable tool for studying these polyanionic structures, as it is sensitive to both the mobile ion of interest (23Na or 6Li/7Li) as well as the surrounding structural framework (31P, 19F). The fluorophosphate family of sodium cathode materials is extremely promising, as the materials are both thermally and electrochemically stable, with the advantage of being relatively inexpensive depending on the redox active transition metal of choice. In particular, the electrochemical performance of Na2MPO4F (M= Fe, Co, Ni, Mn) has been investigated in recent years, and is found to be an exemplary candidate for use in Na ion batteries.4 We have utilized 23Na NMR to gain understanding of the structural changes that occur during electrochemical extraction and reinsertion of Na ions during the charging and discharging processes of a number of fluorophosphate analogues. The paramagnetic nature of many of these materials makes their investigation by NMR non-trivial, requiring the use of fast magic-angle spinning (MAS) and low external magnetic fields. In particular, the structural changes occurring upon desodiation of Na2FePO4F were investigated by NMR, where the attenuation of one of the two sites is attributed to the selective removal of Na ions from a single crystallographic position. Additionally, by cycling Na2FePO4F versus a Li-metal counter electrode we observe evidence of substantial Na-Li ion exchange by 7Li NMR, opening the door for interesting heteronuclear correlation experiments with a hybrid Na/Li cathode material. The movement of Li ions as a function of electrochemical cycling can also be tracked in Li cathode materials. Receiving significant attention is the fluorosulfate structure of the form LiFeSO4F, which benefits from a high redox potential and excellent electrochemical behaviour.5,6 6,7Li ssNMR was used here to identify any changes to the Li environment at various stages along the electrochemical charge/discharge cycle, providing valuable insight into the structural stability of this material.(1) Tarascon, J.-M.; Armand, M. Nature 2001. (2) Padhi, A. K.; Nanjundaswamy, K. S.; Masquelier, C.; Masque; Okada, S.; Goodenough, J. B. J. Electrochem. Soc. 1997, 144, 1609–1613. (3) Ellis, B. L.; Nazar, L. F. Current Opinion in Solid State & Materials Science 2012, 16, 168–177. (4) Ellis, B. L.; Makahnouk, W. R. M.; Rowan-Weetaluktuk, W. N.; Ryan, D. H.; Nazar, L. F. Chem. Mater. 2010, 22, 1059–1070. (5) Barpanda, P.; Ati, M.; Melot, B. C.; Rousse, G.; Chotard, J.-N.; Doublet, M.-L.; Sougrati, M. T.; Corr, S. A.; Jumas, J.-C.; Tarascon, J.-M. Nature Materials 2011, 10, 772–779. (6) Tripathi, R.; Gardiner, G. R.; Islam, M. S.; Nazar, L. F. Chem. Mater. 2011, 23, 2278–2284. Figure 1: 23Na 30 kHz MAS NMR spectra of pristine Na2FePO4F (red) and electrochemically generated Na1.5FePO4F (blue) demonstrating the decrease in intensity at site A during cycling as well as the formation of a novel site (#).

Prodigiosin analogue designed for metal coordination: stable zinc and copper pyrrolyldipyrrins.

The pyrrolyldipyrrin motif is found in several naturally occurring prodigiosin pigments. The potential roles of the interactions of prodigiosins with transition metals and the properties of metal-bound pyrrolyldipyrrins, however, have been difficult to assess because of the very limited number of well-characterized stable complexes. Here, we show that the introduction of a meso-aryl substituent and an ethyl ester group during the sequential assembly of the three heterocycles affords a pyrrolyldipyrrin of enhanced coordinating abilities when compared to that of natural prodigiosins. UV–visible absorption studies indicate that this ligand promptly binds Zn(II) ions with 2:1 ligand-to-metal stoichiometry and Cu(II) ions with 1:1 stoichiometry. Notably, no addition of base is required for the formation of the resulting stable complexes. The crystal structures reveal that whereas the tetrahedral zinc center engages two nitrogen donors on each ligand, the pseudosquare planar copper complex features coordination of all three pyrrolic nitrogen atoms and employs the ester group as a neutral ligand. This first example of coordination of a redox-active transition metal within a fully conjugated pyrrolyldipyrrin framework was investigated spectroscopically by electron paramagnetic resonance to show that the 1:1 metal-to-ligand ratio found in the crystal structure is also maintained in solution.

Radiocopper for the imaging of copper metabolism

The redox-active transition metal copper is an essential trace element for growth and development and serves as a structural or catalytic cofactor for many enzymes in a range of physiological processes. Mammalian copper homeostasis is tightly regulated, and an imbalance in copper metabolism is implicated in various pathological disorders. Radioactive copper isotopes, in particular (64) Cu (t1/2 = 12.7 h) and (67) Cu (t1/2 = 62.01 h), have made important contributions to the understanding of copper metabolism in health and disease. This review gives a brief account of how radiolabelled copper(II) salts and bioreductive copper complexes have been used to trace copper uptake, transport and efflux in vitro and in vivo. Recently, positron emission tomography (PET) has emerged as a noninvasive tool to image copper metabolism in living subjects and (64) Cu-PET is investigated for the study of copper-related neurological disorders, genetic diseases and cancer.

EPR Spectroscopy of a Clinically Active (1:2) Copper(II)-Histidine Complex Used in the Treatment of Menkes Disease: A Fourier Transform Analysis of a Fluid CW-EPR Spectrum

Redox active transition metal ions (e.g., iron and copper) have been implicated in the etiology of many oxidative stress-related diseases including also neurodegenerative disorders. Unbound copper can catalyze formation of reactive oxygen species (hydroxyl radicals) via Fenton reaction/Haber–Weiss chemistry and therefore, under physiological conditions, free copper is potentially toxic and very rarely exists inside cells. Copper(II) bound to the aminoacid l-histidine represents a species discovered in blood in the mid 60s and since then extensive research on this complex was carried out. Copper bound to l-histidine represents an exchangeable pool of copper(II) in equilibrium with the most abundant blood plasma protein, human serum albumin. The structure of this complex, in aqueous solution, has been a subject of many studies and reviews, however without convincing success. The significance of the (1:2) copper(II)-l-histidine complex at physiological pH documents its therapeutic applications in the treatment of Menkes disease and more recently in the treatment of infantile hypertrophic cardioencephalomyopathy. While recently the (1:2) Cu(II)-l-His complex has been successfully crystallized and the crystal structure was solved by X-ray diffraction, the structure of the complex in fluid solution at physiological pH is not satisfactorily known. The aim of this paper is to study the (1:2) Cu(II)-l-histidine complex at low temperatures by X-band and S-band EPR spectroscopy and at physiological pH at room temperature by Fourier transform CW-EPR spectroscopy.

Myths, Artifacts, and Fatal Flaws: Identifying Limitations and Opportunities in Vitamin C Research

Research progress to understand the role of vitamin C (ascorbic acid) in human health has been slow in coming. This is predominantly the result of several flawed approaches to study design, often lacking a full appreciation of the redox chemistry and biology of ascorbic acid. In this review, we summarize our knowledge surrounding the limitations of common approaches used in vitamin C research. In human cell culture, the primary issues are the high oxygen environment, presence of redox-active transition metal ions in culture media, and the use of immortalized cell lines grown in the absence of supplemental ascorbic acid. Studies in animal models are also limited due to the presence of endogenous ascorbic acid synthesis. Despite the use of genetically altered rodent strains lacking synthesis capacity, there are additional concerns that these models do not adequately recapitulate the effects of vitamin C deprivation and supplementation observed in humans. Lastly, several flaws in study design endemic to randomized controlled trials and other human studies greatly limit their conclusions and impact. There also is anecdotal evidence of positive and negative health effects of vitamin C that are widely accepted but have not been substantiated. Only with careful attention to study design and experimental detail can we further our understanding of the possible roles of vitamin C in promoting human health and preventing or treating disease.

Copper induces – and copper chelation by tetrathiomolybdate inhibits – endothelial activation in vitro

Endothelial activation with increased expression of cellular adhesion molecules and chemokines critically contributes to vascular inflammation and atherogenesis. Redox-active transition metal ions play an important role in vascular oxidative stress and inflammation. Therefore, the goal of the present study was to investigate the role of copper in endothelial activation and the potential anti-inflammatory effects of copper chelation by tetrathiomolybdate (TTM) in human aortic endothelial cells (HAECs). Incubating HAECs with cupric sulfate dose- and time-dependently increased mRNA and protein expression of vascular cell adhesion molecule-1 (VCAM-1), intercellular adhesion molecule-1 (ICAM-1), and monocyte chemotactic protein-1 (MCP-1). Copper also activated the redox-sensitive transcription factors, nuclear factor kappa B (NF-κB) and activator protein-1 (AP-1), which was inhibited by pretreatment of the cells with TTM. Furthermore, TTM dose-dependently inhibited tumor necrosis factor α (TNFα)-induced activation of NF-κB and AP-1, as well as mRNA and protein expression of VCAM-1, ICAM-1, and MCP-1, which was abolished by preincubating the cells with 5 µM TTM and 15 µM cupric sulfate. The inhibitory effect of TTM on TNFα-induced NF-κB activation was associated with decreased phosphorylation and degradation of IκBα. These data suggest that intracellular copper causes activation of redox-sensitive transcription factors and upregulation of inflammatory mediators in endothelial cells. Copper chelation by TTM may attenuate TNFα-induced endothelial activation and, hence, inhibit vascular inflammation and atherosclerosis.

Pro-oxidative synergic bactericidal effect of NO: kinetics and inhibition by nitroxides

NO plays diverse roles in physiological and pathological processes, occasionally resulting in opposing effects, particularly in cells subjected to oxidative stress. NO mostly protects eukaryotes against oxidative injury, but was demonstrated to kill prokaryotes synergistically with H2O2. This could be a promising therapeutic avenue. However, recent conflicting findings were reported describing dramatic protective activity of NO. The previous studies of NO effects on prokaryotes applied a transient oxidative stress while arbitrarily checking the residual bacterial viability after 30 or 60min and ignoring the process kinetics. If NO-induced synergy and the oxidative stress are time-dependent, the elucidation of the cell killing kinetics is essential, particularly for survival curves exhibiting a “shoulder” sometimes reflecting sublethal damage as in the linear-quadratic survival models. We studied the kinetics of NO synergic effects on H2O2-induced killing of microbial pathogens. A synergic pro-oxidative activity toward gram-negative and gram-positive cells is demonstrated even at sub-μM/min flux of NO. For certain strains, the synergic effect progressively increased with the duration of cell exposure, and the linear-quadratic survival model best fit the observed survival data. In contrast to the failure of SOD to affect the bactericidal process, nitroxide SOD mimics abrogated the pro-oxidative synergy of NO/H2O2. These cell-permeative antioxidants, which hardly react with diamagnetic species and react neither with NO nor with H2O2, can detoxify redox-active transition metals and catalytically remove intracellular superoxide and nitrogen-derived reactive species such as •NO2 or peroxynitrite. The possible mechanism underlying the bactericidal NO synergy under oxidative stress and the potential therapeutic gain are discussed.

Alleviation of phyto-toxicity of copper on agricultural plants

Copper (Cu), a redox-active transition metal, is known to be involved in protein metabolism, photosynthetic and respiratory electron transport, cell wall metabolism, antioxidant activity, nitrogen fixation, ion metabolization, and hormone perception, among others in plants. Though Cu has been listed among the essential elements, it could potentially result in complete inhibition of plant growth and development at excess concentrations. Measures available for alleviating Cu toxicity in plants are discussed in the present paper. Exogenous application of nitric oxide through up-regulating the components of antioxidant defense system [catalase (CAT-EC 1.11.1.6), peroxidase (POD-EC 1.11.1.7), superoxide dismutase (SOD-EC 1.15.1.1), and ascorbate peroxidase (APX-EC 1.11.1.11) activities] and stimulating the enzyme P5CS (D1-pyrroline-5-carboxylate synthetase), which catalyzes proline biosynthesis, has been proved to stand against the adverse impacts of Cu toxicity. Addition of cations (such as Ca2+ and Mg2+) through stimulating site-specific competition for metal ions could also prevent excess accumulation of Cu in cell interior. Silicon application, through nutrient balancing and physically blocking the apoplastic bypass flow has also been recognized to be effective in alleviating Cu toxicity. Addition of organic amendments and use of arbuscular mycorrhizal fungi as soil inoculants have also proved successful in amelioration of Cucontaminated soils. Though molecular and physiological mechanisms associated with Cu toxicity have been substantially investigated, information on the regulation of the expression of stress-related genes in key agricultural plant species is still lacking. Additional research efforts focusing at field validation of the toxicity alleviation methods are also equally important.

Oxidoreductases that Act as Conditional Virulence Suppressors in Salmonella enterica Serovar Typhimurium

In Salmonella enterica serovar Typhimurium, oxidoreductases of the thioredoxin superfamily contribute to bacterial invasiveness, intracellular replication and to the virulence in BALB/c mice as well as in the soil nematode Caenorhabditis elegans. The scsABCD gene cluster, present in many but not all enteric bacteria, codes for four putative oxidoreductases of the thioredoxin superfamily. Here we have analyzed the potential role of the scs genes in oxidative stress tolerance and virulence in S. Typhimurium. An scsABCD deletion mutant showed moderate sensitization to the redox-active transition metal ion copper and increased protein carbonylation upon exposure to hydrogen peroxide. Still, the scsABCD mutant was not significantly affected for invasiveness or intracellular replication in respectively cultured epithelial or macrophage-like cells. However, we noted a significant copper chloride sensitivity of SPI1 T3SS mediated invasiveness that strongly depended on the presence of the scs genes. The scsABCD deletion mutant was not attenuated in animal infection models. In contrast, the mutant showed a moderate increase in its competitive index upon intraperitoneal challenge and enhanced invasiveness in small intestinal ileal loops of BALB/c mice. Moreover, deletion of the scsABCD genes restored the invasiveness of a trxA mutant in epithelial cells and its virulence in C. elegans. Our findings thus demonstrate that the scs gene cluster conditionally affects virulence and underscore the complex interactions between oxidoreductases of the thioredoxin superfamily in maintaining host adaptation of S. Typhimurium.

Trace metals can affect hydroxyl radical production and yellowing of photo-irradiated wool

Previous studies identified that trace metals within the wool fibre are associated with the production of free radicals and yellowing in photo-irradiated wool, and that protein-bound redox-active transition metals, particularly iron and copper, can catalyse the production of hydroxyl radicals and oxidation of proteins in biological systems. This present study investigated the relationship between trace metal content, hydroxyl radical production, tensile strength and yellowing of photo-irradiated metal-doped wool fabric. Iron increased the production of hydroxyl radicals and phototendering, and both copper and iron increased the rate of photoyellowing. The tensile strength of iron-doped wool fabric decreased whereas the strength of copper-doped wool increased after artificial weathering while wet. Manganese reduced hydroxyl radical production and had little effect on photoyellowing. Antioxidants and chelating agents were added to quench hydroxyl radicals and sequester metal ions. Ascorbic acid, citric acid and ethylenediamine tetraacetic acid increased hydroxyl radical production whereas deferoxamine mesylate (desferal) and diethylenetriamine pentaacetic acid reduced production.

Efficient visible-light-induced hydrogenation over composites of CdS and ruthenium carbonyl complexes

Hybrid systems built by coupling CdS with a series of Ru carbonyl complexes ([Ru(bpy)2(CO)2](PF6)2 (RC-1), [Ru(phen)2(CO)2](PF6)2 (RC-2), [Ru(bpy)(CO)2Cl2] (RC-3), [Ru(Me2bpy)(CO)2Cl2] (RC-4), and [Ru(phen)(CO)2Cl2] (RC-5)) showed activity for the hydrogenation of carbonyl compounds under visible-light irradiations in the presence of appropriate sacrificial agent. The influences of the irradiations mode, sacrificial agent, substrates, and the structure of the Ru complexes on the hydrogenation performance of these composites were investigated. Results indicated that CdS act as the photosensitizer, while the Ru carbonyl complexes as catalytic active component. This study provides some guidance in the development of feasible hybrid photocatalytic systems encompassing visible-light-responsive semiconductors and redox-active transition metal complexes, which are expected to find great potentials in the photocatalytic organic transformations. It is believed that such photocatalytic systems can be built in a more controllable way based on our understanding on the structure–activity relationship of the molecular electro-catalyst.

PP027. Alterations in maternal antioxidant micronutrient concentrations in women prior to developing pre-eclampsia

Changes in plasma antioxidant trace elements during pregnancy are closely related to mortality and morbidity in the newborn. Deficiencies of specific micronutrient antioxidant activities, associated with copper, selenium, zinc and manganese have previously been associated with pre-eclampsia (PE) at term. The purpose of the present study was to investigate these maternal plasma micronutrient concentrations with associated enzyme activities, specifically the copper-related caeruloplasmin, in a subcohort of the international SCreening fOr Pregnancy Endpoints (SCOPE) study, in early pregnancy, prior to disease onset. Pre-disease plasma samples (14-16+6 weeks') collected from women who subsequently developed PE (n=245) and age- and BMI-matched uncomplicated normotensive controls (NC; n=471) were used following written informed consent. Micronutrient concentrations were measured by inductively-coupled mass spectrometry and caeruloplasmin activity by colorimetric activity assay. Plasma copper concentrations at 15 weeks' gestation were significantly elevated in women who subsequently developed PE; no differences were seen for all other micronutrients (Table). No differences were seen in caeruloplasmin activity between the two groups. However, a positive association between copper concentration and caeruloplasmin activity was observed (r=0.305; R2=0.093; P<0.0001). Copper has a dual function in pregnancy, while it may be beneficial as a cofactor for numerous antioxidant enzymes, it also a redox-active transition metal, which catalyses the formation of free radicals and increased levels may contribute to oxidative stress status in PE. These data indicate that although women with PE show significantly higher copper, the caeruloplasmin activity is not significantly higher. It seems that during PE, the activity does not increase proportionally with the levels of copper and may indicate a dysfunction of the antioxidant enzyme. Work is underway to characterise copper-dependent antioxidant superoxide dismutase activity and markers of oxidative stress in these women. British Heart Foundation (Charity No. 225971).

Tandem Postsynthetic Metal Ion and Ligand Exchange in Zeolitic Imidazolate Frameworks

Herein, we report a general postsynthetic exchange (PSE) approach to introduce a redox-active transition metal, specifically Mn(II), into "inert" zeolitic imidazolate frameworks (ZIFs), a subclass of metal-organic frameworks (MOFs). It is shown that metal ion PSE occurs in ZIF-71 (RHO topology) and ZIF-8 (SOD topology) under ambient conditions. The metal exchanged ZIFs are the first porous, Mn(II)-based ZIFs and a rare example of ZIFs with two transition metal centers in a single lattice. Exchanged materials are characterized by scanning electron microscopy-energy dispersed X-ray spectroscopy (SEM-EDX), aerosol time-of-flight mass spectrometry (ATOFMS), X-ray fluorescence spectroscopy (XRF), and Brunauer-Emmett-Teller (BET) surface area analysis. In addition, stepwise "tandem" PSE strategies are described to exchange of metal ions and organic linkers consecutively in ZIFs. These findings are important for probing the chemical dynamics of ZIFs, despite their high crystallinity and robustness, and inspire the more widespread use of PSE to prepare multimetallic and multifunctional MOFs.