Comprehensive analyses of the inotropic compound omecamtiv mecarbil in rat and human cardiac preparations

Omecamtiv mecarbil (OM), a myosin activator, was reported to induce complex concentration- and species-dependent effects on contractile function and clinical studies indicated a low therapeutic index with diastolic dysfunction at concentrations above 1 µM. To further characterize effects of OM in a human context and under different preload conditions, we constructed a setup that allows isometric contractility analyses of human induced pluripotent stem cell (hiPSC)-derived engineered heart tissues (EHTs). The results were compared to effects of OM on the very same EHTs measured under auxotonic conditions. OM induced a sustained, concentration-dependent increase in time-to-peak under all conditions (maximally 2-3 fold). Peak force, in contrast, was increased by OM only in human, but not rat EHTs and only under isometric conditions, varied between hiPSC lines and showed a biphasic concentration-dependency with maximal effects at 1 µM. Relaxation time tended to fall under auxotonic and strongly increase under isometric conditions, again with biphasic concentration-dependency. Diastolic tension concentration-dependently increased under all conditions. The latter was reduced by an inhibitor of the mitochondrial sodium calcium exchanger (CGP-37157). OM induced increases in mitochondrial oxidation in isolated cardiomyocytes, indicating that OM, an inotrope that does not increase intracellular and mitochondrial Ca2+, can induce mismatch between an increase in ATP and ROS production and unstimulated mitochondrial redox capacity. Taken together, we developed a novel setup well suitable for isometric measurements of EHTs. The effects of OM on contractility and diastolic tension are complex with concentration-, time-, species- and loading-dependent differences. Effects on mitochondrial function require further studies.

The Impact of N-Acetyl Cysteine and Coenzyme Q10 Supplementation on Skeletal Muscle Antioxidants and Proteome in Fit Thoroughbred Horses

Horses have one of the highest skeletal muscle oxidative capacities amongst mammals, which, combined with a high glycolytic capacity, could perturb redox status during maximal exercise. We determined the effect of 30 d of oral coenzyme Q10 and N-acetyl-cysteine supplementation (NACQ) on muscle glutathione (GSH), cysteine, ROS, and coenzyme Q10 concentrations, and the muscle proteome, in seven maximally exercising Thoroughbred horses using a placebo and randomized cross-over design. Gluteal muscle biopsies were obtained the day before and 1 h after maximal exercise. Concentrations of GSH, cysteine, coenzyme Q10, and ROS were measured, and citrate synthase, glutathione peroxidase, and superoxide dismutase activities analyzed. GSH increased significantly 1 h post-exercise in the NACQ group (p = 0.022), whereas other antioxidant concentrations/activities were unchanged. TMT proteomic analysis revealed 40 differentially expressed proteins with NACQ out of 387 identified, including upregulation of 13 mitochondrial proteins (TCA cycle and NADPH production), 4 Z-disc proteins, and down regulation of 9 glycolytic proteins. NACQ supplementation significantly impacted muscle redox capacity after intense exercise by enhancing muscle glutathione concentrations and increasing expression of proteins involved in the uptake of glutathione into mitochondria and the NAPDH-associated reduction of oxidized glutathione, without any evident detrimental effects on performance.

Effect of Mn On The Performance and Mechanism of Catalysts For The Synthesis of (Ce,La)CO3F

In accordance with the cerium-lanthanum ratio of fluorocerium ores in the mineralogy of the Baiyun Ebo process, pure substances such as Ce(NO3)3·6H2O, La(NO3)3·6H2O were used to synthesize (Ce,La)CO3F grains to simulate bastnaesite minerals by hydrothermal method, and used as NH3-SCR denitrification catalysts. After being roasted at a series of different temperatures, the catalyst surface produced a well-crystallised Ce7O12 species as the active component for denitrification. The activity results showed that the synthetic (Ce,La)CO3F was roasted at 500°C, and the NOx conversion was 27% at 200°C. The NH3-SCR catalytic activity of the synthesised (Ce,La)CO3F was improved by loaded transition metal Mn. The best catalyst was found to be produced by impregnating (Ce,La)CO3F with 1 mol/L manganese nitrate solution, with a NOx conversion of 80% at 250°C. The physicochemical properties were analysed using XRD, BET, H2-TPR, NH3-TPD and XPS. The loading of Mn resulted in the appearance of numerous well-dispersed MnOx species on the catalyst surface, the dispersion of Ce7O12 species was also greatly enhanced, and the reduction in grain size indicated that Mnn+ entered into the (Ce,La)CO3F lattice causing lattice shrinkage. The number of acidic sites on the catalyst surface and the redox capacity were enhanced. The amount of Ce3+ in the catalyst was also enhanced by the introduction of Mnn+, but the proportion of adsorbed oxygen decreased, which indicated that the introduction of Mnn+ was detrimental to the increase in the proportion of adsorbed oxygen. The reaction mechanisms of the (Ce,La)CO3F and Mn/(Ce,La)CO3F catalysts were investigated by in-situ Fourier transform infrared spectroscopy (FTIR), to provide theoretical guidance for the specific reaction pathways of bastnaesite in the NH3-SCR reaction. The results showed that catalysts followed both the E-R and L-H mechanisms throughout the reaction process. When loaded with Mn, the main reactive species in the L-H mechanism were the NH4+(ad) species on the Brønsted acidic site and the O-Ce3+-O-NO, O-Mn3+-O-NO species. The main reactive species for the E-R mechanism were NH3/NH4+(ad) species on the Brønsted/Lewis acidic sites and NO. The NH4+ (ad) species on the Brønsted acidic sites act as the main reactive NH3(g) adsorbing species, bonded to the Ce4+ in the carrier (Ce,La)CO3F to participate in the acid cycle reaction. The introduction of Mnn+ increases the number of Brønsted acidic sites on the catalyst surface, and acts as an adsorption site for NO, to react with NO to generate more monodentate nitrate species, to participate in the redox cycle reactions. The above results indicated that Mnn+ and (Ce,La)CO3F have a good mutual promotion effect, which makes the loaded catalyst have excellent performance, which provides a theoretical basis for the high value utilization of bastnaesite.

Experimental Evaluation on the Catalytic Activity of a Novel CeZrK/rGO Nanocomposite for Soot Oxidation in Catalyzed Diesel Particulate Filter

A nanostructured solid solution catalyst CeZrK/rGO for soot oxidation in catalyzed diesel particulate filter was synthesized using the dipping method. The reduced graphene oxide (rGO) was used as the catalyst carrier, and CeO2, ZrO2, and K2O were mixed with the molar ratio of 5:1:1, 5:2:2 and 5:3:3, which were referred to as Ce5Zr1K1/rGO, Ce5Zr2K2/rGO, and Ce5Zr3K3/rGO, respectively. The structure, morphology and catalytic activity of the CeZrK/rGO nanocomposites were thoroughly investigated and the results show that the CeZrK/rGO nanocomposites have nanoscale pore structure (36.1–36.9 nm), high-dispersion quality, large specific surface area (117.2–152.4 m2/g), small crystallite size (6.7–8.3 nm), abundant oxygen vacancies and superior redox capacity. The 50% soot conversion temperatures of Ce5Zr1K1/rGO, Ce5Zr2K2/rGO, and Ce5Zr3K3/rGO under tight contact condition were decreased to 352 °C, 339 °C and 358 °C respectively. The high catalytic activity of CeZrK/rGO nanocomposites can be ascribed to the following factors: the doping of Zr and K ions causes the nanocrystalline phase formation in CeZrK solid solutions, reduces the crystallite size, generates abundant oxygen vacancies and improves redox capacity; the rGO as a carrier provides a large specific surface area, thereby improving the contact between soot and catalyst.

Nonpolarizing oxygen-redox capacity without O-O dimerization in Na2Mn3O7

Reversibility of an electrode reaction is important for energy-efficient rechargeable batteries with a long battery life. Additional oxygen-redox reactions have become an intensive area of research to achieve a larger specific capacity of the positive electrode materials. However, most oxygen-redox electrodes exhibit a large voltage hysteresis >0.5 V upon charge/discharge, and hence possess unacceptably poor energy efficiency. The hysteresis is thought to originate from the formation of peroxide-like O22− dimers during the oxygen-redox reaction. Therefore, avoiding O-O dimer formation is an essential challenge to overcome. Here, we focus on Na2-xMn3O7, which we recently identified to exhibit a large reversible oxygen-redox capacity with an extremely small polarization of 0.04 V. Using spectroscopic and magnetic measurements, the existence of stable O−• was identified in Na2-xMn3O7. Computations reveal that O−• is thermodynamically favorable over the peroxide-like O22− dimer as a result of hole stabilization through a (σ + π) multiorbital Mn-O bond.

Highly Efficient Photocatalytic Cr(VI) Reduction by Lead Molybdate Wrapped with D-A Conjugated Polymer under Visible Light

Well-designed composite photocatalysts are of increasing concern due to their enhanced catalytic performance compared to a single component. Here, a photocatalyst composed of PbMoO4 (PMO) and poly-benzothiadiazole (BBT, a D-A-conjugated polymer) was successfully synthesized by BBT polymerization on the surface of the PMO. The resultant BBT-PMO with a heterojunction structure represented an enhanced ability to reduce highly toxic heavy metal Cr(VI) from water under visible light irradiation. The 16.7% BBT-PMO(N, nanoscale) showed the best performance. The corresponding kobs over the 16.7% BBT-PMO(N) was 26-fold (or 53-fold) of that over the pure BBT (or pristine PMO(N)), and this activity was maintained after four cycles. The reasons for its good performance are discussed in detail based on the experimental results. Moreover, the synthesis of the BBT in situ of the PMO also altered the morphology of the BBT component, increasing the specific surface area of the BBT-PMO(N) and endowing it with the ability to adsorb Cr(VI). Additionally, the photocatalyst was also environmentally friendly as such a wrapped structure could sustain the high stability of the PMO without dissociation. This work provides a good strategy for efficient photocatalytic Cr(VI) reduction by designing an organic–inorganic hybrid system with high redox capacity.

Enhancement of redox capacity derived from O-doping g-C3N4/WO3 nanosheet for photocatalytic degradation of tetracycline under different dissolved oxygen concentration

Element-doping is an essential method to adjust band structure, light absorbance and charge transfer and separation of semiconductor. Besides, whether the photocatalyst could work in oxygen-deficient environment is also important....