Excess O2 Research Articles

Oxidative and Inflammatory Imbalance in Placenta and Kidney of sFlt1-Induced Early-Onset Preeclampsia Rat Model.

Preeclampsia (PE) is a pregnancy-specific disorder characterized by the new onset of hypertension plus proteinuria and/or end-organ dysfunction. Here, we investigate the role of the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase system as a major component of reactive oxygen species generation, in a rodent model of early-onset preeclampsia induced by excess sFlt1 (soluble fms-like tyrosine kinase 1). Placenta and kidney samples were obtained from normal pregnant and PE rats to measure the sFlt1/PlGF (placental growth factor) ratio in addition to oxidative stress-related parameters, including the activities and expressions of NADPH oxidase isoforms (NOX1, NOX2, and NOX4), components of nitric oxide (NO) metabolism, and antioxidant enzymes. Peroxisome proliferator-activated receptors (PPARα, PPARγ) and cytokines IL1β, IL3, IL6, IL10, and IL18 were also measured to evaluate the inflammation status in our experimental setting. Excessive O2●− production was found in rats that were treated with sFlt1; interestingly, this alteration appears to be mediated mainly by NOX2 in the placenta and by NOX4 in the kidney. Altered NO metabolism and antioxidant defense systems, together with mitochondrial dysfunction, were observed in this model of PE. Preeclamptic animals also exhibited overexpression of proinflammatory biomarkers as well as increased collagen deposition. Our results highlight the role of NADPH oxidase in mediating oxidative stress and possibly inflammatory processes in the placenta and kidney of an sFlt1-based model of early-onset preeclampsia.

Recovery of reduced thiol groups by superoxide-mediated denitrosation of nitrosothiols

Nitrosation of critical thiols has been elaborated as reversible posttranslational modification with regulatory function in multiple disorders. Reversibility of S-nitrosation is generally associated with enzyme-mediated one-electron reductions, catalyzed by the thioredoxin system, or by nitrosoglutathione reductase.In the present study, we confirm previous evidence for a non-enzymatic de-nitrosation of nitrosoglutathione (GSNO) by superoxide. The interaction leads to the release of nitric oxide that subsequently interacts with a second molecule of superoxide (O2•−) to form peroxynitrite. Despite the formation of peroxynitrite, approximately 40–70% of GSNO yielded reduced glutathione (GSH), depending on the applied analytical assay. The concept of O2•− dependent denitrosation was then applied to S-nitrosated enzymes. S-nitrosation of isocitrate dehydrogenase (ICDH; NADP+-dependent) was accompanied by an inhibition of the enzyme and could be reversed by dithiothreitol. Treatment of nitrosated ICDH with O2•− indicated ca. 50% recovery of enzyme activity. Remaining inhibition was largely consequence of oxidative modifications evoked either by O2•− or by peroxynitrite. Recovery of activity in S-nitrosated enzymes by O2•− appears relevant only for selected examples. In contrast, recovery of reduced glutathione from the interaction of GSNO with O2•− could represent a mechanism to regain reducing equivalents in situations of excess O2•− formation, e.g. in the reperfusion phase after ischemia.

Restrictions of nitric oxide electrocatalytic decomposition over perovskite cathode in presence of oxygen: Oxygen surface exchange and diffusion

Nitric oxide (NO) abatement from engine exhaust is of great significance to alleviate air pollution and haze. Compared with the traditional selective catalytic reduction (SCR) technology, electrocatalytic decomposition of NO simplifies the reductant supply system and therefore avoids secondary pollution. In this study, typical perovskite La0.6Sr0.4CoxFe1-xO3-δ (LSCF) infiltrated by different dosages of nano ceria Ce0.9Gd0.1O1.9 (GDC) was used as composite cathodes, in order to explore the critical factors to restrain NO conversion in excess of O2. The results show that electron as reactive species transfers among NO, ABO3-type cathode and oxygen vacancy. The maximum of NO removal efficiency can reach 96.27 % in absence of O2 and up to 80.55 % in presence of 1% O2 in case of LSCF infiltrated by moderate dosages LSCF-GDC(2), which is superior to those of LSCF, LSCF-GDC(4) and LSM-GDC(nano) composite cathode. Compared to oxygen storage capacity (OSC) caused by the infiltration of nano ceria, higher surface oxygen exchange coefficient (kδ) and chemical diffusion coefficient (Dchem) lead to the significant decrease in polarization resistance (Rp), and consequently to the enhancement of NO removal in presence of O2. No matter what kind of oxygen deriving from oxygen reduction reaction (ORR) and NO reduction reaction (NORR), GDC infiltration into LSCF improves oxygen transport property and however, the property of cathode in ORR is dominant over in NORR in presence of O2. Moderate GDC loading has the highest oxygen transport kinetics, and oxygen surface exchange is faster than chemical diffusion, due to lower activation energy. Over loading of GDC with greater ohmic resistance (Rs) inversely influences the NO removal.

Modification of a 240 kWth grate incineration system for oxyfuel combustion of wood chips

The objective of this work is the application of the oxyfuel combustion technology for grate incineration systems to increase the CO2 concentration in the flue gas for higher efficiency when processing the gas for storage or utilization. Therefore, an experimental 240 kWth moving grate combustion facility has been modified to allow the investigation of the combustion behavior under various oxyfuel conditions. Subsequent to the modification, combustion experiments with dried wood chips under air and several oxyfuel atmospheres have been performed. During oxyfuel operation, the oxygen concentration in the gas supply streams towards the furnace has been set to 30 vol.-% dry with recycled flue gas being the rest of the gas composition. The oxygen distribution between primary and secondary zone has been varied (30%/70%, 40%/60%). Additionally, one case with increased oxygen concentration in the primary zone (40 vol.-% dry) has been investigated. The results show that oxyfuel grate incineration of the given fuel in this setup is feasible. However, the combustion behavior differs significantly between air and oxyfuel conditions in the investigated cases. The CO2 concentration in the dry flue gas could be increased to around 73 vol.-% with 5.7 vol.-% excess O2. Compared to the reference air cases the emission rates of CO were also increased during oxyfuel operation. However, it seems manageable given enough excess oxygen (∼7 vol.-% dry). Although the temperature at the end of the furnace is comparable among the cases, oxyfuel combustion leads to lower maximum temperatures along the combustion chamber. Differences between 150 °C and 200 °C have been measured among corresponding air and oxyfuel cases. Also, the temperatures of the grate and inside the fuel bed are reduced during oxyfuel operation even in the case with increased O2 concentration leading to the impression that the thermal strain on the grate is lower compared to air operation with the same fuel throughput.

Too much tolerance for hyperoxemia in mechanically ventilated patients with SARS-CoV-2 pneumonia? Report from an Italian intensive care unit.

BackgroundIn COVID-19 patients requiring mechanical ventilation, the administration of high oxygen (O2) doses for prolonged time periods may be necessary. Although life-saving in most cases, O2 may exert deleterious effects if administered in excessive concentrations. We aimed to describe the prevalence of hyperoxemia and excessive O2 administration in mechanically ventilated patients with SARS-CoV-2 pneumonia and determine whether hyperoxemia is associated with mortality in the Intensive Care Unit (ICU) or the onset of ventilator-associated pneumonia (VAP).Materials and methodsRetrospective single-center study on adult patients with SARS-CoV-2 pneumonia requiring invasive mechanical ventilation for ≥48 h. Patients undergoing extracorporeal respiratory support were excluded. We calculated the excess O2 administered based on the ideal arterial O2 tension (PaO2) target of 55–80 mmHg. We defined hyperoxemia as PaO2 > 100 mmHg and hyperoxia + hyperoxemia as an inspired O2 fraction (FiO2) > 60% + PaO2 > 100 mmHg. Risk factors for ICU-mortality and VAP were assessed through multivariate analyses.ResultsOne hundred thirty-four patients were included. For each day of mechanical ventilation, each patient received a median excess O2 of 1,121 [829–1,449] L. Hyperoxemia was found in 38 [27–55]% of arterial blood gases, hyperoxia + hyperoxemia in 11 [5–18]% of cases. The FiO2 was not reduced in 69 [62–76]% of cases of hyperoxemia. Adjustments were made more frequently with higher PaO2 or initial FiO2 levels. ICU-mortality was 32%. VAP was diagnosed in 48.5% of patients. Hyperoxemia (OR 1.300 95% CI [1.097–1.542]), time of exposure to hyperoxemia (OR 2.758 [1.406–5.411]), hyperoxia + hyperoxemia (OR 1.144 [1.008–1.298]), and daily excess O2 (OR 1.003 [1.001–1.005]) were associated with higher risk for ICU-mortality, independently of age, Sequential Organ failure Assessment score at ICU-admission and mean PaO2/FiO2. Hyperoxemia (OR 1.033 [1.006–1.061]), time of exposure to hyperoxemia (OR 1.108 [1.018–1.206]), hyperoxia + hyperoxemia (OR 1.038 [1.003–1.075]), and daily excess O2 (OR 1.001 [1.000–1.001]) were identified as risk factors for VAP, independently of body mass index, blood transfusions, days of neuromuscular blocking agents (before VAP), prolonged prone positioning and mean PaO2/FiO2 before VAP.ConclusionExcess O2 administration and hyperoxemia were common in mechanically ventilated patients with SARS-CoV-2 pneumonia. The exposure to hyperoxemia may be associated with ICU-mortality and greater risk for VAP.

Multi-responsive mesoporous polydopamine composite nanorods cooperate with nano-enzyme and photosensitiser for intensive immunotherapy of bladder cancer.

Bladder cancer is a common malignancy in the urinary system. Defects of drug molecules in bladder during treatment, such as passive diffusion, rapid clearance of periodic urination, poor adhesion and permeation abilities, lead to low delivery efficiency of conventional drugs and high recurrence rate of disease. In this study, we designed multi-responsive mesoporous polydopamine (PDA) composite nanorods cooperating with nano-enzyme and photosensitiser for intensive immunotherapy of bladder cancer. The strongly adhesive mesoporous PDA with wheat germ agglutinin on nanoparticles could specifically adhere to epithelial glycocalyx and made the nanoparticles aggregate in urinary pathways. Meanwhile, 2,3-dimethylmaleic anhydride could be hydrolysed in acidic conditions of tumour microenvironment, giving it a positive charge (charge reversal), which is more amenable to enter cancer cells. Afterwards, manganese dioxide nanorods could catalyse the reaction of excess H2 O2 in tumour microenvironment to generate active oxygen, so as to change the hypoxic environment in tumour, and achieve a pH-responsive for slow release of PD-L1. After the ICG was irradiated by infrared light, a large amount of singlet oxygen was generated, thereby enhancing the therapeutic effect and reducing toxicity in vivo. Besides, mesoporous PDA with indocyanine green photothermal agent could have a local heat up quickly under the near-infrared light to kill cancer cells, thereby enhancing therapeutic efficacy. Accordingly, this mesoporous PDA composite nanorods shed a light on bladder tumour treatment.

Catalysts Optimization of WO3‐SiO2 Supported Iridium for NOx Reduction by CO under Excess Oxygen Conditions

AbstractA series of Ir‐based catalysts were prepared by ultrasonic‐assisted equal‐volume impregnation to evaluate the catalytic performance of selective catalytic reduction of NOx by CO (CO‐SCR) with excess O2 in simulated flue gas. We investigated the effects of different carrier, Ir loading, and composite carrier ratio (W/Si) on the CO‐SCR activities. The results showed that WO3 and SiO2 were effective carriers for the CO‐SCR reaction under oxygen‐rich conditions. Results of XRD and H2‐TPR studies indicated that metal Ir strongly interacted with carrier WO3 and SiO2, respectively, which improved the surface dispersion of active component Ir species and was conducive to the removal of NOx and CO. When W/Si molar ratio was 1/9 and Ir loading was 2 wt%, the Ir/WO3‐SiO2 catalyst reached 49 % NOx conversion and 76 % CO conversion at 225°C, while NO2 yield was also only 5 ppm. The effects of O2, SO2, and H2O on the structure of Ir/WO3‐SiO2 were analyzed by XRD and XPS characterization methods. It was found that O2 could oxidize Ir species to IrO2, thereby inhibiting NOx reduction. A low concentration of SO2 can weaken the process of Ir oxidation, promote NOx reduction, and improve catalytic activity. H2O can reduce the NOx conversion rate and inhibit the CO‐SCR reaction, but the inhibition effect is reversible.

Longitudinal Changes in Skeletal Muscle Metabolism, Oxygen Uptake, and Myosteatosis During Cardiotoxic Treatment for Early-Stage Breast Cancer

BackgroundWhile cardiotoxic chemotherapy is known to negatively impact cardiac function and hemoglobin levels, the impact on skeletal muscle has been understudied among patients. The purpose was to longitudinally characterize myosteatosis (muscle fat), skeletal muscle metabolism, and oxygen (O2) consumption during cardiotoxic chemotherapy for breast cancer.Patients and MethodsThirty-four patients with stage I-III breast cancer were enrolled before trastuzumab-containing and/or anthracycline-containing chemotherapy. We used magnetic resonance imaging to non-invasively quantify thigh myosteatosis (fat-water imaging), and lower leg metabolism (31P spectroscopy), O2 consumption (custom techniques), and peak power output during single-leg plantarflexion exercise at pre-, mid-, end-chemotherapy, and 1-year. We also measured pulmonary VO2peak and maximal leg press strength.ResultsDuring chemotherapy, VO2peak and leg press strength decreased while peak plantarflexion power output was maintained. At mid-chemotherapy, hemoglobin decreased (16%) and lower leg blood flow increased (37%) to maintain lower leg O2 delivery; exercise Pi:PCr and myosteatosis increased. Between mid- and end-chemotherapy, lower leg O2 extraction (28%) and O2 consumption (21%) increased, while plantarflexion exercise efficiency (watts/O2 consumed) decreased. At one year, VO2peak and leg press strength returned to pre-chemotherapy levels, but lower leg exercise O2 extraction, consumption and Pi:PCr, and myosteatosis remained elevated.ConclusionLower leg skeletal muscle blood flow and O2 extraction adapt to compensate for chemotherapy-related hemoglobin reduction for small muscle mass exercise but are insufficient to maintain large muscle mass exercise (pulmonary VO2peak, leg press strength). The excess O2 required to perform work, increased Pi:PCr ratio and myosteatosis together suggest suppressed fat oxidation during chemotherapy.

Self-delivery of metal-coordinated mitochondria protonophore uncoupler for O2-exhausting enhanced bioreductive therapy

Mitochondrial uncouplers are capable of maximizing cell respiration to induce local hypoxia, which provides a promising target for bioreductive therapy. In this work, we develop a metal-coordinated mitochondria protonophore uncoupler (designated as Cu-BAQ) for O2-exhausting enhanced bioreductive therapy. In brief, carrier free Cu-BAQ is self-assembled by copper ion (Cu2+), mitochondria protonophore uncoupler (BAM15) and bioreductive drug (AQ4N), which possesses a favorable stability and an improved bioavailability. After intravenous administration, nanosized Cu-BAQ prefers to accumulate at tumor site for effective cellular uptake. Moreover, the Cu2+-coordinated nanomedicine of Cu-BAQ exhibits a glutathione (GSH) responsive drug release behavior and the released BAM15 could promote the mitochondria uncoupling to maximize the cell respiration. As a result, the excessive O2 consumption would induce local hypoxia to activate AQ4N for enhanced bioreductive therapy. In vivo investigations demonstrate that Cu-BAQ is able to regulate tumor hypoxia microenvironment and significantly inhibit tumor growth with a minimized side effect. This GSH-responsive self-delivery nanoplatform provides a new insight for the development of individualized biomedicine for hypoxic tumor precision therapy.

Operational guide to stabilize, standardize and increase power plant efficiency

Complex engineering systems, such as power plants, deliver their best performance when operating along a designed range of some priority parameters. However, plant field operation may deviate from design conditions, and new references must be identified. Actions towards high-quality operation can be supported by fine modeling, which helps building decision support tools. The present work proposes a standardization strategy for the operation of an actual coal-fired power plant based on a Design of Experiment approach, partially tested onsite and finally accomplished with surrogate models built upon a 2 year long database. Artificial Neural Networks (ANNs) and Mass and Energy balances (M&Es) are used to represent the plant’s steam generator and its mills subset, which is the core of an operational guide to increase system efficiency under actual operation. Primary and secondary air flows, pulverized coal outlet temperature, speed of the dynamic classifier, primary air flow, excess O2, primary and secondary air pressures are the seven controllable factors selected as the most relevant ones among an extensive set of parameters, able to perform effective maneuvers. The application of the operational guide indicates combinations of ranges of the seven controllable parameters that allow for achieving steam generator efficiency within the 84.0% to 88.92% range. The proposed methodology aims as well to improve safe and stable conditions to a system that undergoes operation different than the one prescribed by the original design. The study case results show an opportunity to raise efficiency by up to 2.28% during operation, which represents a reduction in coal consumption by 3.1 t/h and above 6% on CO2 emissions.

Investigation on the Role of Pd, Pt, Rh in Methane Abatement for Heavy Duty Applications

Methane abatement remains a challenge in aftertreatment systems of natural gas engines, currently under discussion in combination with synthetic methane. In this study, Pt/Rh and Pd/Rh-based three-way catalysts are investigated under various transient conditions because transients between O2 excess (lean) and O2-poor (rich) conditions can significantly enhance methane abatement. At mid to high temperatures, transitions from rich to lean feed yield higher rates of methane direct oxidation under lean conditions with the Pt/Rh catalyst, compared to the Pd/Rh catalyst. Both catalysts are able to trigger methane steam reforming (SR) after transitions from lean to rich feed. The SR reaction leads to increased H2 and NH3 formation. However, SR deactivates much faster in the Pt/Rh catalyst. At low temperature, the Pt/Rh catalyst is more active for SR. Results from an additional Pd-only catalyst confirm that Rh is essential for NOx conversion and high N2 selectivity. The distinct characteristics of Pt, Pd and Rh demonstrate the benefits obtained from the combination of the three platinum group metals. The potential of the Pt/Pd/Rh catalyst is proved to be significant throughout the complete engine map. Under optimized lean/rich oscillatory conditions, the Pt/Pd/Rh catalyst yields more than 95% methane conversion under almost all conditions while maintaining efficient abatement of all other pollutants.

Selective Catalytic Reduction of NOx over Perovskite-Based Catalysts Using CxHy(Oz), H2 and CO as Reducing Agents-A Review of the Latest Developments.

Selective catalytic reduction (SCR) is probably the most widespread process for limiting NOx emissions under lean conditions (O2 excess) and, in addition to the currently used NH3 or urea as a reducing agent, many other alternative reductants could be more promising, such as CxHy/CxHyOz, H2 and CO. Different catalysts have been used thus far for NOx abatement from mobile (automotive) and stationary (fossil fuel combustion plants) sources, however, perovskites demand considerable attention, partly due to their versatility to combine and incorporate various chemical elements in their lattice that favor deNOx catalysis. In this work, the CxHy/CxHyOz−, H2−, and CO-SCR of NOx on perovskite-based catalysts is reviewed, with particular emphasis on the role of the reducing agent nature and perovskite composition. An effort has also been made to further discuss the correlation between the physicochemical properties of the perovskite-based catalysts and their deNOx activity. Proposed kinetic models are presented as well, that delve deeper into deNOx mechanisms over perovskite-based catalysts and potentially pave the way for further improving their deNOx efficiency.

Regulate oxygen concentration using a co-culture of activated sludge bacteria and Chlorella vulgaris to maximize biophotolytic hydrogen production

The biophotolytic hydrogen (H2) production is contingent on proper oxygen (O2) concentration regulation. Co-culturing bacteria along with microalgae leads to the uptake of excess O2 produced by algal cells. This uptake of O2 by the bacteria triggers the hydrogenase enzyme activity present in microalgae which is responsible for H2 production. In this study, indigenous bacteria present in activated sludge were co-cultured with Chlorella vulgaris at different ratios. The 1:1.5 v/v (algae to bacteria) co-culture ratio produced the most significant H2 gas volume (1246 mL L−1) with a minimum O2 content (57 mL L−1) during 6 days. Gas production stopped when the pH dropped to about 4. The gas composition at different ratios consisted mainly of H2 (29–37%) and CO2 (34–35%) along with a minor fraction of N2 (10–21%) and O2 (2–4%). No methane (CH4) was observed in any co-culture under experimental conditions. Considering the exceptional inverse relation in H2 production and O2 consumption, algae-activated sludge correlation leads to substantial improvement in the H2 gas production compared to previous studies using pure bacterial cultures.

Neisseria meningitidis Opca Protein/MnO2 Hybrid Nanoparticles for Overcoming the Blood-Brain Barrier to Treat Glioblastoma.

The major hurdle in glioblastoma therapy is the low efficacy of drugs crossing the blood-brain barrier (BBB). Neisseria meningitidis is known to specifically enrich in the central nervous system through the guidance of an outer membrane invasion protein named Opca. Here, by loading a chemotherapeutic drug methotrexate (MTX) in hollow manganese dioxide (MnO2 ) nanoparticles with surface modification of the Opca protein of Neisseria meningitidis, a bionic nanotherapeutic system (MTX@MnO2 -Opca) is demonstrated to effectively overcome the BBB. The presence of the Opca protein enables the drug to cross the BBB and penetrate into tumor tissues. After accumulating in glioblastoma, the nanotherapeutic system catalyzes the decomposition of excess H2 O2 in the tumor tissue and thereby generates O2 , which alleviates tumor hypoxia and enhances the effect of chemotherapy in the treatment of glioblastoma. This bionic nanotherapeutic system may exhibit great potential in the treatment of glioblastoma.

Simultaneously achieving selective catalytic reduction of NOx with NH3 and catalytic oxidation of CO with O2 over one finely optimized bifunctional catalyst Mn2Cu1Al1Ox at low temperatures

For coke oven flue gases, the simultaneous removal of NOx and CO pollutants is highly demanded but still remains a big challenge. So far there isn't a single efficient catalyst that can simultaneously achieve selective catalytic reduction of NOx by NH3 and the catalytic oxidation of CO to CO2 in the presence of excessive O2 at low temperatures (180–220 °C). Here, we report a bifunctional catalyst Mn2Cu1Al1Ox that possesses dual active sites and is highly active for both NH3-SCR and CO oxidation reactions under the above mentioned conditions. By tuning the redox properties and surface oxygen vacancies, the optimized Mn2Cu1Al1Ox catalyst achieved high conversions of both NOx and CO in the NH3-NO-CO-O2 system, with a NOx conversion of 86.8% and a CO conversion of 100% at 200 °C. The active reaction sites and the interaction principal between NH3-SCR and CO oxidation reactions were thoroughly investigated by well-designed experiments, in-situ DRIFTS and DFT calculations. It was revealed that NH3 and CO competed for the same active sites, which significantly influenced the catalytic performance of Mn3Al1Ox and Cu3Al1Ox for CO oxidation reactions. For the bifunctional Mn2Cu1Al1Ox catalyst, CO is more easily adsorbed on the Cu sites, while NH3 is more inclined to adsorb on the Mn sites, which enables both NH3-SCR and CO oxidation reactions to proceed simultaneously on one catalyst. The improvement of CO oxidation performance on Mn2Cu1Al1Ox catalyst is mainly attributed to the reduced Jahn-Teller effect of Cu atoms by doping into Mn3O4, which leads to the lift of d-band center and finally enhances the CO adsorption.

Hydrogen diffusion mechanisms in quartz: insights from H–Li,2H–H and2H–H–Li exchange experiments

AbstractThe diffusivity and diffusion mechanisms of hydrogen together with with deuterium and lithium, parallel to thecaxis of quartz, were investigated experimentally at 800°C, 0.1 GPa with the activity of H2O or2H2O ≈ 1 [2H is used throughout this work to describe deuterium rather than D, to avoid confusion with the diffusion coefficient,D]. The pH was set using mixtures of H2O (or2H2O) and HCl. Three types of experiment were conducted: (1) H-in/Li-out; (2)2H-in/H-out; and (3)2H-in/H + Li out, using three different natural quartz crystals as starting materials. Profiles of H,2H and Li were measured using Fourier-transform infrared (FTIR) spectroscopy and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). H,2H and Li are charge-compensated by Al3+replacing Si4+, or by excess O2–. The total atomic concentration of monovalent cations appears to remain constant over the duration of the experiments. The resulting diffusion profiles are different for the three experimental designs and three starting materials, and some show complex shapes inconsistent with simple diffusion. A multi-site diffusion–reaction model is developed, with the theory based on previous models that have been derived mainly on the basis of conductivity measurements. In these models, the monovalent cations move away from their charge-balancing ion then diffuse rapidly to another site. The mobility of the monovalent cations is described by both a diffusion coefficient and an equilibrium constant that enables dissociation of the immobile charge-balanced defects. This model can describe complex step-shaped profiles formed in H-in/Li-out experiments, profiles with local maxima ('humped’ profiles) in2H-in/H + Li out experiments, and error function-shaped profiles in2H-in/H-out and previously published Li-in/H-out experiments. Our data provide support for models previously proposed for quartz. Studies of the lengths and forms of diffusion profiles from such experiments provide a useful complement to assertions from conductivity experiments.

Catalytically active gold clusters with atomic precision for noninvasive early intervention of neurotrauma

BackgroundNeurotrauma is a worldwide public health problem which can be divided into primary and secondary damge. The primary damge is caused by external forces and triggers the overproduction of peroxides and superoxides, leading to long-lasting secondary damage including oxidative stress, wound infection and immunological reactions. The emerging catalysts have shown great potential in the treatment of brain injury and neurogenic inflammation, but are limited to biosafety issues and delivery efficiency.ResultsHerein, we proposed the noninvasive delivery route to brain trauma by employing highly active gold clusters with enzyme-like activity to achieve the early intervention. The decomposition rate to H2O2 of the ultrasmall gold clusters is 10 times that of glassy carbon (GC) electrodes, indicating excellent catalytic activity. The gold clusters can relieve the oxidative stress and decrease the excessive O2·− and H2O2 both in vitro and in vivo. Besides, gold clusters can accelerate the wound healing of brain trauma and alleviate inflammation via inhibiting the activation of astrocytes and microglia through noninvasive adminstration. decrease the peroxide and superoxide of brain tissue.ConclusionsPresent work shows noninvasive treatment is a promising route for early intervention of brain trauma.

Biocatalytic CsPbX3 Perovskite Nanocrystals: A Self-Reporting Nanoprobe for Metabolism Analysis.

CsPbX3 perovskite nanocrystals (NCs), with excellent optical properties, have drawn considerable attention in recent years. However, they also suffer from inherent vulnerability and hydrolysis, causing the new understanding or new applications to be difficultly explored. Herein, for the first time, it is discovered that the phospholipid membrane (PM)-coated CsPbX3 NCs have intrinsic biocatalytic activity. Different from other peroxidase-like nanozymes relying on extra chromogenic reagents, the PM-CsPbX3 NCs can be used as a self-reporting nanoprobe, allowing an "add-to-answer" detection model. Notably, the fluorescence of PM-CsPbX3 NCs can be rapidly quenched by adding H2 O2 and then be restored by removing excess H2 O2 . Initiated from this unexpected observation, the PM-CsPbX3 NCs can be explored to prepare multi-color bioinks and metabolite-responsive paper analytical devices, demonstrating the great potential of CsPbX3 NCs in bioanalysis. This is the first report on the discovery of nanozyme-like property of all-inorganic CsPbX3 perovskite NCs, which adds another piece to the nanozyme puzzle and opens new avenues for in vitro disease diagnostics.

Nicotinamide Adenine Dinucleotide Phosphate Oxidases in Glucose Homeostasis and Diabetes-Related Endothelial Cell Dysfunction.

Oxidative stress within the vascular endothelium, due to excess generation of reactive oxygen species (ROS), is thought to be fundamental to the initiation and progression of the cardiovascular complications of type 2 diabetes mellitus. The term ROS encompasses a variety of chemical species including superoxide anion (O2•−), hydroxyl radical (OH−) and hydrogen peroxide (H2O2). While constitutive generation of low concentrations of ROS are indispensable for normal cellular function, excess O2•− can result in irreversible tissue damage. Excess ROS generation is catalysed by xanthine oxidase, uncoupled nitric oxide synthases, the mitochondrial electron transport chain and the nicotinamide adenine dinucleotide phosphate (NADPH) oxidases. Amongst enzymatic sources of O2•− the Nox2 isoform of NADPH oxidase is thought to be critical to the oxidative stress found in type 2 diabetes mellitus. In contrast, the transcriptionally regulated Nox4 isoform, which generates H2O2, may fulfil a protective role and contribute to normal glucose homeostasis. This review describes the key roles of Nox2 and Nox4, as well as Nox1 and Nox5, in glucose homeostasis, endothelial function and oxidative stress, with a key focus on how they are regulated in health, and dysregulated in type 2 diabetes mellitus.

Methane oxidation to methanol over copper-containing zeolite

Methane oxidation to methanol over copper-containing zeolite