Low Redox Activity Research Articles

Ligand-based electron transfer enables molecular polypyridyl Zn(II) complexes for efficient photocatalytic CO2 reduction

Electron transfer process plays a critical role in photocatalytic CO2 reduction. Owing to low redox activity of Zn(II) cation under catalytic conditions, it remains a challenge to use Zn(II) complexes as efficient molecular catalysts for CO2 photoreduction. Herein, we overcome the obstacle and demonstrate two polypyridyl Zn(II) complexes can be utilized for selective photoreduction of CO2 to CO. Thanks to more efficient ligand-based electron transfer, the polypyridyl Zn(II) complex modified with electron-donating carbazole groups displays a higher TON of CO up to 116 than the other unsubstituted polypyridyl Zn(II) complex, which is among the most efficient Zn(II) complexes molecular catalysts in CO2 photoreduction. Photocatalytic mechanism has been studied by UV–vis absorption spectroscopy and computational calculations. These results show a promising way to develop Zn(II) complexes for efficient CO2 photoreduction through ligand modification and ligand-based electron transfer.

Engineering sulfuric acid-pretreated biochar supporting MnO2 for efficient toxic organic pollutants removal from aqueous solution in a wide pH range

Manganese dioxides (MnO2) and biochar materials are both desirable candidates for environmental remediation of toxic organic pollutants (TOPs) in water due to wide availability and environmental-friendly. In practical application, however, MnO2 suffers from low redox activity owing to deprotonation, while biochar is subject to limited removal capacity. Herein, a difunctional engineering sulfuric acid-pretreated biochar supporting MnO2 composite (MBC-A) was firstly synthesized and optimized to remove various TOPs from aqueous solution. Specifically, sulfuric acid not only served as an active agent to improve the specific surface area of biochar for improvement of adsorption capacity and more MnO2 loading, but also facilitated the introduction of sulfonic acid groups (-SO3H) as an internal proton reservoir to inhibit inactivation of MnO2 due to deprotonation in alkaline. Thanks to adsorption and oxidation, MBC-A showed excellent removal capacity (214.9 mg/g) and fast reaction kinetics (360 min) for tetracycline (TC), exceeding precursor and other materials reported in literature. Importantly, the effective operation pH range of MBC-A was broadened to 1–13 with the help of buffering capacity of –SO3H groups. The dominant driving force of adsorption were π-π interaction and hydrogen bond; while reactive oxidative species were mainly ascribed to singlet oxygen (1O2), hydroxyl radical (·OH) and reactive Mn3+. The possible reactive sites and pathway were investigated by combining experimental results with density functional theory (DFT) calculation. Further, the results of multiple cyclic runs, removal in real river water and toxicity assessment demonstrated well reusability, high environmental security, and excellent practical applicability of MBC-A.

Solvothermal synthesis of hybrid nanoarchitectonics nickel-metal organic framework modified nickel foam as a bifunctional electrocatalyst for direct urea and nitrate fuel cell

Urea and nitrate-based fuel cells have emerged as promising electricity generation devices. However, most of these catalysts are expensive and limited in supply, which limits their practical applications. Hence, metal-organic frameworks (MOF) have been explored as catalysts due to their low cost, easy preparation, and high redox activity. Here, we synthesize nickel-based MOF (Ni-MOF) via one-pot solvothermal technique as bifunctional electrocatalyst for the direct urea and nitrate fuel cell. The as-synthesized Ni-MOF is deposited on nickel foam (NF) and used as working electrode (Ni-MOF/NF) which demonstrates a peak current density of 188 mA/cm2 for urea oxidation reaction (UOR) and −14 mA/cm2 for nitrate reduction reaction (NRR) at an onset potential of ∼ 1.58 V (vs RHE), and ∼ 1.12 V (vs RHE), respectively The enhanced functionality of the Ni-MOF/NF electrode can be attributed to the high catalytic efficacy of the Ni-MOF. This is mainly due to the presence of multiple oxidation states of N (i.e., Ni2+/3+) and excellent electronic conductivity of the organic ligands in MOF structure. Moreover, Ni-MOF/NF electrodes retain ∼ 71.2% and ∼ 83.9% capacity after 20000 s of UOR and NRR, respectively. This efficacy of the as-fabricated electrocatalyst proves MOF as a promising platform for direct fuel cell applications.

Enhanced cyclic redox reactivity of Fe2O3/Al2O3 by Sr doping for Chemical-Looping combustion of solid fuels

Aiming at the problems of low redox activity and easy sintering deactivation of iron-based oxygen carriers (OCs), Sr was used to modify Fe2O3/Al2O3 in chemical looping combustion (CLC) of solid fuels. The Sr doped Fe2O3/Al2O3 possessed high fuel combustion reactivity with different solid fuels (coal, coal char and biomass). During consecutive cycles, high cycling durability and morphological preservation were observed for Sr doped Fe2O3/Al2O3, signifying that the addition of strontium effectively enhanced the anti-sintering ability and inhibited the phase segregation of Fe2O3/Al2O3 during cyclic reactions. By comparing the coal char combustion reactivity of Fe2O3/Al2O3 samples doped with different SrO content (1 wt%, 5 wt% and 10 wt%), the optimum additive amount of SrO was 5 wt%. In addition, the characterization analysis proved that the Sr dopant suppressed the outward diffusion of Fe cations and maintained the surface micro-morphology of Fe2O3/Al2O3 in the process of CLC. This study presented important guiding principle and strategy for the synthesis of iron-based OCs with high cyclic redox reactivity in the CLC of solid fuels.

Carbon nanotube enables high-performance thiophene-containing organic anodes for lithium ion batteries

Poly(thiophene)-based organic compounds with reversible n-type redox behavior can be employed as anode materials for lithium ion batteries (LIBs). However, their inherent problems such as low redox activity, poor rate performance and processing difficultly limit the practical application in LIBs. Herein, a one-dimensional structure-design is reported for a poly(thiophene) derivative (i.e. poly(3-butylthiophene), briefly denoted as P3BT) with a superior lithium storage capability in LIBs. The experimental study and DFT calculation reveal that carbon nanotubes (CNTs) play a critical role in this structure design to promote the electrochemical performances of P3BT. CNTs act as a highly conductive nano-skeleton, which can facilitate the electron transfer, enlarge the electroactive surface area and shorten the ions diffusion path. Besides, the strong π-π interation between P3BT and CNT not only stabilizes the charged and discharged states of P3BT for enhancing the cycling stability, but also compensates the negative effect of introducing of butyl side chains on the energy gap and electron affinity. To the best of our knowledge, the designed one-dimensional P3BT@CNT nanocomposite exhibits a better electrochemical performance compared with the reported thiophene-containing anode materials. This work provides a new insight for the application of thiophene-containing anode materials for LIBs.

Enhanced cyclic redox reactivity of hematite via Sr doping in chemical looping combustion

Aiming at the problems of low redox activity and easy sintering deactivation of hematite, Sr was used to modify hematite in chemical looping combustion (CLC). The results showed that a low concentration (1 wt%) of Sr dopant could significantly improve the redox activity and cyclic stability of hematite. During the successive redox cycles, the surface sintering was not occurred for the Sr-doped hematite samples, indicating that Sr could significantly intensify the sintering resistance of hematite in CLC. In the first redox cycle, the oxygen carrying capacity of the Sr-doped hematite samples followed the sequence: 10Sr-HM (3.32%) > 5Sr-HM (3.20%) > 1Sr-HM (2.11%). By comparing the redox performance of hematite samples doped with different SrO content, 5 wt% is the best addition ratio of SrO dopant. The results of successive 50 cycles indicated that the hematite sample doped with 5 wt% SrO exhibited very high cyclic stability. For the 5Sr-HM, the CH4 conversion and CO2 selectivity was about 90% and 100%, respectively. In addition, the effect of calcination temperature (950 °C, 1050 °C, 1150 °C) on the redox performance of Sr-doped hematite was also considered. The results indicated that the Sr-doped hematite presented high redox activity after high temperature calcination.

Toward High‐Performance Dihydrophenazine‐Based Conjugated Microporous Polymer Cathodes for Dual‐Ion Batteries through Donor–Acceptor Structural Design

AbstractRecent studies have demonstrated that dihydrophenazine (Pz) with high redox‐reversibility and high theoretical capacity is an attractive building block to construct p‐type polymer cathodes for dual‐ion batteries. However, most reported Pz‐based polymer cathodes to date still suffer from low redox activity, slow kinetics, and short cycling life. Herein, a donor–acceptor (D–A) Pz‐based conjugated microporous polymer (TzPz) cathode is constructed by integrating the electron‐donating Pz unit and the electron‐withdrawing 2,4,6‐triphenyl‐1,3,5‐triazine (Tz) unit into a polymer chain. The D–A type structure enhances the polymer conjugation degree and decreases the band gap of TzPz, facilitating electron transportation along the polymer skeletons. Therefore the TzPz cathode for dual‐ion battery shows a high reversible capacity of 192 mAh g−1 at 0.2 A g−1 with excellent rate performance (108 mAh g−1 at 30 A g−1), which is much higher than that of its counterpart polymer BzPz produced from 1,3,5‐triphenylbenzene (Bz) and Pz (148 and 44 mAh g−1 at 0.2 and 10 A g−1, respectively). More importantly, the TzPz cathode also shows a long and stable cyclability of more than 10 000 cycles. These results demonstrate that the D–A structural design is an efficient strategy for developing high‐performance polymer cathodes for dual‐ion batteries.

Voltammetric determination of phentolamine mesylate in pharmaceutical formulations at poly (4-aminobenzene sulfonic acid)-modified glassy carbon electrode

A poly (4-aminobenzene sulfonic acid)-modified glassy carbon electrode (p-ABSA/GCE) was fabricated by electropolymerization. It was found that phentolamine mesylate, an effective and important cardiovascular dilatation drug with low redox activity at the glassy carbon electrode (GCE) can produce a sensitive well-defined anodic peak current at p-ABSA/GCE. Investigation indicated that the oxidation of phentolamine at p-ABSA/GCE was one electron/one proton transfer process which was controlled by adsorption. In optimal conditions, the anodic peak current was linear to the concentrations of phentolamine over the range of 5.0 × 10–7–1.0 × 10–5 M with a detection limit of 2.0 × 10–7 M. The modified electrode showed good stability and reproducibility. The electroanalytical method proposed was successfully applied to the determination of phentolamine mesylate in pharmaceutical formulations.

Structural water and disordered structure promote aqueous sodium-ion energy storage in sodium-birnessite

Birnessite is a low-cost and environmentally friendly layered material for aqueous electrochemical energy storage; however, its storage capacity is poor due to its narrow potential window in aqueous electrolyte and low redox activity. Herein we report a sodium rich disordered birnessite (Na0.27MnO2) for aqueous sodium-ion electrochemical storage with a much-enhanced capacity and cycling life (83 mAh g−1 after 5000 cycles in full-cell). Neutron total scattering and in situ X-ray diffraction measurements show that both structural water and the Na-rich disordered structure contribute to the improved electrochemical performance of current cathode material. Particularly, the co-deintercalation of the hydrated water and sodium-ion during the high potential charging process results in the shrinkage of interlayer distance and thus stabilizes the layered structure. Our results provide a genuine insight into how structural disordering and structural water improve sodium-ion storage in a layered electrode and open up an exciting direction for improving aqueous batteries.

A Molecular‐Cage Strategy Enabling Efficient Chemisorption–Electrocatalytic Interface in Nanostructured Li2S Cathode for Li Metal‐Free Rechargeable Cells with High Energy

AbstractUsing high‐capacity and metallic Li‐free lithium sulfide (Li2S) cathodes offers an alternative solution to address serious safety risks and performance decay caused by uncontrolled dendrite hazards of Li metal anodes in next‐generation Li metal batteries. Practical applications of such a cathode, however, still suffer from low redox activity, unaffordable cost, and poor processability of infusible and moisture‐sensitive Li2S. Herein, these difficulties are addressed by developing a molecular cage–engaged strategy that enables low‐cost production and interfacial engineering of Li2S cathodes for rechargeable Li2S//Si cells. An efficient chemisorption–electrocatalytic interface is built in extremely nanostructured Li2S cathodes by harnessing the confinement/separation effect of metal–organic molecular cages on ionic clusters of air‐stable, soluble, and low‐cost Li salt and their chemical transformation. It effectively boosts the redox activity toward Li2S activation/dissociation and polysulfide chemisorption–conversion in Li‐S batteries, leading to low activation voltage barrier, stable cycle life of 1000 cycles, ultrafast current rate up to 8 C, and high areal capacities of Li2S cathodes with high mass loading. Encouragingly, this highly active Li2S cathode can be applied for constructing truly workable Li2S//Si cells with a high specific energy of 673 Wh kg−1 and stable performance for 200 cycles at high rates against hollow nanostructured Si anode.

Toward High Performance Thiophene‐Containing Conjugated Microporous Polymer Anodes for Lithium‐Ion Batteries through Structure Design

AbstractPoly(thiophene) as a kind of n‐doped conjugated polymer with reversible redox behavior can be employed as anode material for lithium‐ion batteries (LIBs). However, the low redox activity and poor rate performance for the poly(thiophene)‐based anodes limit its further development. Herein, a structure‐design strategy is reported for thiophene‐containing conjugated microporous polymers (CMPs) with extraordinary electrochemical performance as anode materials in LIBs. The comparative study on the electrochemical performance of the structure‐designed thiophene‐containing CMPs reveals that high redox‐active thiophene content, highly crosslinked porous structure, and improved surface area play significant roles for enhancing electrochemical performances of the resulting CMPs. The all‐thiophene‐based polymer of poly(3,3′‐bithiophene) with crosslinked structure and a high surface area of 696 m2 g−1 exhibits a discharge capacity of as high as 1215 mAh g−1 at 45 mA g−1, excellent rate capability, and outstanding cycling stability with a capacity retention of 663 mAh g−1 at 500 mA g−1 after 1000 cycles. The structure–performance relationships revealed in this work offer a fundamental understanding in the rational design of CMPs anode materials for high performance LIBs.

Nanoporous TiO2/C composites synthesized from directly pyrolysis of a Ti-based MOFs MIL-125(Ti) for efficient microwave absorption

Nanoporous carbon materials derived from metal organic frameworks (MOFs) have been regarded as an important members in the microwave absorption field. Nevertheless, most attentions only focus on Co-based, Ni-based MOFs and the impedance matching. In this study, a novel nanoporous carbon material (TiO2/C) has been directly synthesized by annealing titanium based MOFs (MIL-125 (Ti), MIL stands for Material from Institute Lavoisier), which possess low toxicity, redox activity and good stability. The obtained TiO2/C composites show outstanding electromagnetic wave absorbing properties. In detail, the minimum reflection loss of −49.6 dB and broad effective bandwidth of 4.6 GHz (13.4–18 GHz) can be reached with an absorbent thickness of 1.6 mm. Our study not only opens a new avenue for artificially designed diverse nanoporous carbon but also introduce a new candidate to directly synthesize absorber by a simple method.

Studies on the redox activity of iron N,O-complexes: Potential T1-contrast agents

Objectives: The goal of this study was to determine the redox activity of iron (ethylenebis[2-(o-hydroxyphenyl)glycine]) (EHPG) and (ethylenebis[2-(o-hydroxybenzyl)glycine]) (EHBG) (N,N′-bis(2-hydroxybenzyl)ethylenediamine-N,N′-diacetic acid) derivative complexes and of some N,O–salan complexes of iron. The hexadentate chelate (EHPG and EHBG) ligands varied in their substituents (polar OMe, NHAc, or lipophilic Ph), while the latter had different charge and lipophilicity. The low redox activity of these complexes is important in their potential applications as magnetic resonance imaging contrast agents.Methods: Redox activity was assessed in the entire Haber–Weiss cycle and separately in the Fenton reaction. The spin-trapping method with 5,5-dimethyl-1-pyrroline-N-oxide monitored in electron paramagnetic resonance was used. The standard Mn marker was applied as a reference for quantitative analysis. Additionally, ascorbate oxidation was analyzed with UV–Vis spectrophotometry.Results: Both the Haber–Weiss cycle and in particular the Fenton reaction showed low redox activity of the studied complexes, which did not exceed 30% of [Fe(EDTA)]− or FeCl3 activity. The N,O–salan complexes expressed even lower activity, i.e. 10–20% activity of [Fe(EDTA)]−.Discussion: For the EHPG and EHBG complexes, it is likely that hydrophobicity and the possibility of H-bond formation play a major role in the resulting redox effects. For this reason, chelates equipped with phenyl groups in the majority belong to less redox-active complexes. For N,O–salan complexes, activity is not correlated with the charge of the coordination sphere, but again, the highly hydrophobic character of the groups and the non-pendant substituents capable of H-bonding that are present in these ligands limit the affinity of hydrophilic species.

Overexpressing superoxide dismutase 2 induces a supernormal cardiac function by enhancing redox-dependent mitochondrial function and metabolic dilation

During heightened cardiac work, O2 consumption by the heart benefits energy production via mitochondria. However, some electrons leak from the respiratory chain and yield superoxide, which is rapidly metabolized into H2O2 by SOD2. To understand the systemic effects of the metabolic dilator, H2O2, we studied mice with cardiac-specific SOD2 overexpression (SOD2-tg), which increases the H2O2 produced by cardiac mitochondria. Contrast echocardiography was employed to evaluate cardiac function, indicating that SOD2-tg had a significantly greater ejection fraction and a lower mean arterial pressure (MAP) that was partially normalized by intravenous injection of catalase. Norepinephrine-mediated myocardial blood flow (MBF) was significantly enhanced in SOD2-tg mice. Coupling of MBF to the double product (Heart Rate×MAP) was increased in SOD2-tg mice, indicating that the metabolic dilator, “spilled” over, inducing systemic vasodilation. The hypothesis that SOD2 overexpression effectively enhances mitochondrial function was further evaluated. Mitochondria of SOD2-tg mice had a decreased state 3 oxygen consumption rate, but maintained the same ATP production flux under the basal and L-NAME treatment conditions, indicating a higher bioenergetic efficiency. SOD2-tg mitochondria produced less superoxide, and had lower redox activity in converting cyclic hydroxylamine to stable nitroxide, and a lower GSSG concentration. EPR analysis of the isolated mitochondria showed a significant decrease in semiquinones at the SOD2-tg Qi site. These results support a more reductive physiological setting in the SOD2-tg murine heart. Cardiac mitochondria exhibited no significant differences in the respiratory control index between WT and SOD2-tg. We conclude that SOD2 overexpression in myocytes enhances mitochondrial function and metabolic vasodilation, leading to a phenotype of supernormal cardiac function.

Inhibition of stationary phase respiration impairs persister formation in E. coli.

Bacterial persisters are rare phenotypic variants that temporarily tolerate high antibiotic concentrations. Persisters have been hypothesized to underlie the recalcitrance of biofilm infections, and strategies to eliminate these cells have the potential to improve treatment outcomes for many hospital-treated infections. Here we investigate the role of stationary phase metabolism in generation of type I persisters in Escherichia coli, which are those that are formed by passage through stationary phase. We find that persisters are unlikely to derive from bacteria with low redox activity, and that inhibition of respiration during stationary phase reduces persister levels by up to ∼1,000-fold. Loss of stationary phase respiratory activity prevents digestion of endogenous proteins and RNA, which yields bacteria that are more capable of translation, replication and concomitantly cell death when exposed to antibiotics. These findings establish bacterial respiration as a prime target for reducing the number of persisters formed in nutrient-depleted, non-growing populations.

Abstract 13035: Overexpressing Superoxide Dismutase 2 Induces Super-normal Cardiac Function by Enhancing Mitochondrial Function and Metabolic Dilation

During heightened cardiac work, O 2 consumption by the heart increases. This increase benefits energy production via mitochondrial e − transport, but some e − “leak” from respiratory chain and yields O 2 [[Unable to Display Character: ˙]] − , which is rapidly metabolized into H 2 O 2 by SOD2. To understand the potential systemic effects of the metabolic dilator, H 2 O 2 , we studied mice with cardiac specific SOD2 overexpression, which would increase H 2 O 2 produced by the cardiac mitochondria (by 1.9 fold vs WT). To determine if this enhanced production of H 2 O 2 enhances metabolic dilation, we first evaluated the effectiveness of SOD2 overexpression to effectively enhance mitochondrial function. Mitochondria of SOD2 transgenic mice had a decreased state 3 oxygen consumption rate, but maintained the same level of ATP production; thus indicating a higher P/O ratio and bioenergetics efficiency induced by overexpressing SOD2. Mitochondria of SOD2-tg (compared to WT) produced less • O 2 − , and had lower redox activity (by EPR) and lower GSSG concentration (decreased by 37.2±4.5%). EPR analysis of the isolated mitochondria showed significant decrease of semiquinone in the SOD2-tg at the Q i site (by 69.4±9.9%), and a diminished complex I-derived protein thiyl radical(s). These results support a more reductive physiological setting of the SOD2-tg heart. Cardiac mitochondria isolated from SOD2-tg exhibited no significant differences in the respiratory control index between WT and SOD2-tg. These results support that the SOD2 overexpression is effective and results in enhanced mitochondrial function. Contrast echocardiography was employed to evaluate hemodynamic effects. Mean arterial pressure (MAP) was lower in the SOD2-tg, but was normalized by intravenous injection of catalase suggesting “spill-over” of H 2 O 2 from the myocardium in sufficient amounts to produce a systemic effect. Increasing myocardial work (norepinephrine) caused a far greater increase myocardial blood flow (MBF) per level of work in SOD2-tg compared to WT. Echocardiography indicated SOD2-tg had a significant greater ejection fraction (90±1% vs 74±2%). In conclusion, SOD2 overexpression in myocytes enhances mitochondrial function and metabolic vasodilation, leading to phenotype of super-normal cardiac function.

Investigation of perovskite supported composite oxides for chemical looping conversion of syngas

In typical chemical looping processes, a transition metal oxide based oxygen carrier is used to indirectly convert carbonaceous fuels into concentrated CO2 and carbon free products through cyclic redox reactions. Among the various oxygen carrier candidates, iron oxide represents a promising option due to its abundance, low cost, and unique thermodynamic properties. A key challenge for ferrite based oxygen carriers resides in their low redox activity. In the current study, composite iron oxides with three types of mixed ionic–electronic conductive (MIEC) supports, i.e. lanthanum strontium ferrite (Sr-substituted lanthanum ferrite or LSF), barium cerium ferrite (Ce-substituted barium ferrite, BCF) and calcium titanate ferrite (Fe-substituted calcium titanate, CTF), are synthesized using solid state reaction (SSR) and sol–gel methods. Among the three MIEC materials, CTF support is found to possess superior structural stability. MIEC supported oxygen carriers are found to be significantly more active than a reference, yttrium-stabilized zirconia (YSZ) supported oxygen carrier. Higher support conductivity and smaller iron oxide precursor sizes generally lead to enhanced oxygen carrier activity. In contrast, surface area of the oxygen carrier is weakly correlated with its redox activity. CTF, although less conductive compared to BCF and LSF, is stable and sufficiently effective in shuttling active O2− and electrons for syngas oxidation and iron oxide regeneration. Therefore, CTF supported ferrites can potentially be a cost-effective oxygen carrier candidate for chemical looping processes. Further improvements in redox activity of the oxygen carriers can be achieved through iron oxide particle size reduction and support conductivity enhancement.

The heart as an endocrine source of metabolic vasodilators (1079.26)

During heightened cardiac work, O2 consumption by the heart increases. This increase benefits energy production via mitochondrial e¯ transport, but the process of e¯ transport is not perfect and some e¯ “leak” from respiratory chain and reduce O2. This reduction yields O2˙¯, which reacts with thiol groups, iron, and is rapidly metabolized into H2O2 by mitochondrial superoxide dismutase (SOD2). To understand the potential systemic effects of the metabolic dilator, H2O2, we studied mice with cardiac specific SOD2 overexpression, which would increase the amount of H2O2 produced by the heart. To determine if this enhanced production of H2O2 results in a humoral action, i.e., systemic vasodilation, we first evaluated the effectiveness of SOD2 overexpression to effectively remove O2˙¯ from the mitochondria (EPR). SOD2 transgenic mice produced less O2, and had lower redox activity. Mitochondria of SOD2‐tg (vs WT) had lower GSSG concentration (decreased by 37.2±4.5%, GSH/GSSG ratio was increased by 66.7±6.8%). EPR analysis of the isolated mitochondria showed significant decrease of semiquinone in the SOD2‐tg vs WT at the Qi site (by 69.4±9.9%), and a diminished complex I protein thiyl radical(s) in the mitochondria of SOD2‐tg. These results support a more reducing milieu in the mitochondria of the SOD2‐tg heart. Cardiac mitochondria isolated from SOD2‐tg exhibited no significant differences in the respiratory control index between WT and SOD2‐tg (6.30.3 vs. 5.70.5, p>0.05). These results support the concept that the SOD2 overexpression is effective and results in increased production of H2O2. Moreover, arterial pressure was lower in the SOD2‐tg, but was normalized by iv injection of catalase, implying that the metabolic dilator, H2O2, “spilled” over inducing systemic vasodilation. In conclusion, SOD2 overexpression in myocytes triggers a more reductive milieu in murine heart enhancing the production of H2O2, which then acts as an endocrine dilator causing reductions in arterial pressure.Grant Funding Source: NIH RO1 HL083237

Reversible redox reactions in an epitaxially stabilized SrCoOx oxygen sponge

Fast, reversible redox reactions in solids at low temperatures without thermomechanical degradation are a promising strategy for enhancing the overall performance and lifetime of many energy materials and devices. However, the robust nature of the cation's oxidation state and the high thermodynamic barrier have hindered the realization of fast catalysis and bulk diffusion at low temperatures. Here, we report a significant lowering of the redox temperature by epitaxial stabilization of strontium cobaltites (SrCoOx) grown directly as one of two distinct crystalline phases, either the perovskite SrCoO3-{\delta} or the brownmillerite SrCoO2.5. Importantly, these two phases can be reversibly switched at a remarkably reduced temperature (200~300 {\deg}C) in a considerably short time (< 1 min) without destroying the parent framework. The fast, low temperature redox activity in SrCoO3-{\delta} is attributed to a small Gibbs free energy difference between two topotatic phases. Our findings thus provide useful information for developing highly sensitive electrochemical sensors and low temperature cathode materials.

Comparison of Overt and Cryptic Labile Plasma Iron In Thalassemia Patients In Israel and Gaza-Palestine

AbstractAbstract 5166 Background.Systemic iron overload (SIO) is characterized by persistently high levels of plasma iron that often surpass transferrin's (Tf) binding capacity and generate chemical forms identified as non-Tf bound iron (NTBI). These forms have been perceived as: a. clinically important indicators of SIO per se and of impending organ damage, because cells chronically exposed to iron overloaded plasma attain iron levels and ensuing ROS formation that override their antioxidant capacities and b. as pharmacological targets for chelation and thereby of prevention of tissue iron overload. However, NTBI determination in the clinical setting has been confounded by the chemical heterogeneity of iron forms found in fluids like plasma/sera of SIO patients, the presence of residual amounts of undefined chelates or chelators and the need to dislodge NTBI from native ligands with agents that facilitate its detection.We have assayed the overt forms of NTBI that represent the native pool of labile (= redox-active, chelatable and membrane permeant) iron in plasma/serum. We defined it as ‘labile plasma iron’ or LPI and analyzed it by the Aferrix FeROS™ test (1) and used it to asses chelation regimens in their ability to maintain patients' plasma at relatively low (basal) LPI levels (<0.4 μ M, ref. 2). Detection of NTBI forms with both low redox activity and poor chelator accessibility (defined as cryptic LPI) can also be done with the FeROS™ test by supplementing samples with an agent (nitrilotriacetate= NTA < 0.5 mM) that in plasma “extracts” iron from native NTBI. Thus whereas LPI measures overtly labile NTBI in native plasma (i.e. LPI), LPIplus detects both overt + cryptic forms, as in classical NTBI assays that involve either mobilization + filtration (3) or in the DCI (directly chelatable iron) assay that measures deferrioxamine chelatable NTBI (4). Aim.To compare SIO parameters in polytransfused thalassemia major patients, chelated and non-chelated, as revealed by measurements of overt and cryptic LPI. Methods.The studies involved: 1. The Hadassah Medical Center (HMC) in Jerusalem, where 15–20 (randomly selected, age 14–35) patients were under regular transfusion/chelation treatment and 2. The European Medical Center in Gaza (EMC), where regularly transfused patients (age 10–22) were only sporadically chelated. NTBI assays were performed on sera prepared from blood, (where applicable taken after >10 hrs drug washout, as described for LPI (1,2) and DCI (4); for LPIplus, the LPI test was conducted in the presence of 0.5 mM NTA. Results.As shown previously (2,4), LPI was detected only in patients with >70% Tf-saturation.In HMC, the mean LPI of n=18 patients rose from 0.51±0.41 μ M to 1.00 ±0.46 μ M in the presence of NTA, matching the DCI level of 0.91±0.7 μ M. The LPI rise was detected in 12/15 (= 80%) of samples with LPI>0.4 μ M (≂p 66% of the entire cohort). Thus, despite chelation, a substantial number of patients had relatively low but significant levels of both overt and cryptic NTBI. Among the 3 patients with no significant LPI or DCI (0.2-0.4 μ M), 2/3 became LPI positive (0.6-0.8 μ M) when tested with NTA.Unexpectedly, in EMC-Gaza, among 20 transfused unchelated patients with serum ferritins > 5000 ng/ml and Tf saturation >100%, 8/20 of them (≂p 40%) had undetectable levels of overt LPI but substantial cryptic NTBI. In the remaining 12/20, the mean overt LPI of 0.69±0.65 μ M rose significantly (p<0.01) to 2.05 ±1.56 μ M when the cryptic component (NTA-extractable) was added. Discussion.Overt and cryptic NTBI components were detected by two modalities of the LPI assay in both regularly chelated and unchelated thalassemia patients, although to different extents and proportions. Compared to chelated patients, those unchelated had significantly higher mean values of both overt and cryptic NTBI components, despite the higher proportion of patients with only cryptic NTBI. On an individual basis, the persistent appearance of either/both LPI component(s) of NTBI could provide a measure of SIO and/or the success of individual chelation regimens. However, remaining to be established is the pathophysiological role of each component of NTBI to SIO, disease progression and treatment success. Supported by ISF and the Canadian Friends of HUJI.1. Esposito et al. Blood 102:2670-7 (2003); 2. Zanninelli et al. Br. J. Hematol. 147: 744–51(2009); 3. Hider R. Eur J Clin Invest 32:S50–4 (2002); 4. Pootrakul et al. Blood 104: 1504–10 (2004). Disclosures:Cabantchik:Aferrix Ltd: Consultancy, Membership on an entity's Board of Directors or advisory committees.