Concept: Carbon monoxide
Recombinant human erythropoietin (rHuEpo) increases haemoglobin mass (Hb(mass)) and maximal oxygen uptake ([Formula: see text] O(2 max)). PURPOSE: This study defined the time course of changes in Hb(mass), [Formula: see text] O(2 max) as well as running time trial performance following 4 weeks of rHuEpo administration to determine whether the laboratory observations would translate into actual improvements in running performance in the field. METHODS: 19 trained men received rHuEpo injections of 50 IU•kg(-1) body mass every two days for 4 weeks. Hb(mass) was determined weekly using the optimized carbon monoxide rebreathing method until 4 weeks after administration. [Formula: see text] O(2 max) and 3,000 m time trial performance were measured pre, post administration and at the end of the study. RESULTS: Relative to baseline, running performance significantly improved by ∼6% after administration (10∶30±1∶07 min:sec vs. 11∶08±1∶15 min:sec, p<0.001) and remained significantly enhanced by ∼3% 4 weeks after administration (10∶46±1∶13 min:sec, p<0.001), while [Formula: see text] O(2 max) was also significantly increased post administration (60.7±5.8 mL•min(-1)•kg(-1) vs. 56.0±6.2 mL•min(-1)•kg(-1), p<0.001) and remained significantly increased 4 weeks after rHuEpo (58.0±5.6 mL•min(-1)•kg(-1), p = 0.021). Hb(mass) was significantly increased at the end of administration compared to baseline (15.2±1.5 g•kg(-1) vs. 12.7±1.2 g•kg(-1), p<0.001). The rate of decrease in Hb(mass) toward baseline values post rHuEpo was similar to that of the increase during administration (-0.53 g•kg(-1)•wk(-1), 95% confidence interval (CI) (-0.68, -0.38) vs. 0.54 g•kg(-1•)wk(-1), CI (0.46, 0.63)) but Hb(mass) was still significantly elevated 4 weeks after administration compared to baseline (13.7±1.1 g•kg(-1), p<0.001). CONCLUSION: Running performance was improved following 4 weeks of rHuEpo and remained elevated 4 weeks after administration compared to baseline. These field performance effects coincided with rHuEpo-induced elevated [Formula: see text] O(2 max) and Hb(mass).
Solar-driven photocatalytic conversion of CO2 into fuels has attracted a lot of interest; however, developing active catalysts that can selectively convert CO2 to fuels with desirable reaction products remains a grand challenge. For instance, complete suppression of the competing H2 evolution during photocatalytic CO2-to-CO conversion has not been achieved before. We design and synthesize a spongy nickel-organic heterogeneous photocatalyst via a photochemical route. The catalyst has a crystalline network architecture with a high concentration of defects. It is highly active in converting CO2 to CO, with a production rate of ~1.6 × 10(4) μmol hour(-1) g(-1). No measurable H2 is generated during the reaction, leading to nearly 100% selective CO production over H2 evolution. When the spongy Ni-organic catalyst is enriched with Rh or Ag nanocrystals, the controlled photocatalytic CO2 reduction reactions generate formic acid and acetic acid. Achieving such a spongy nickel-organic photocatalyst is a critical step toward practical production of high-value multicarbon fuels using solar energy.
Electroreduction of carbon dioxide into higher-energy liquid fuels and chemicals is a promising but challenging renewable energy conversion technology. Among the electrocatalysts screened so far for carbon dioxide reduction, which includes metals, alloys, organometallics, layered materials and carbon nanostructures, only copper exhibits selectivity towards formation of hydrocarbons and multi-carbon oxygenates at fairly high efficiencies, whereas most others favour production of carbon monoxide or formate. Here we report that nanometre-size N-doped graphene quantum dots (NGQDs) catalyse the electrochemical reduction of carbon dioxide into multi-carbon hydrocarbons and oxygenates at high Faradaic efficiencies, high current densities and low overpotentials. The NGQDs show a high total Faradaic efficiency of carbon dioxide reduction of up to 90%, with selectivity for ethylene and ethanol conversions reaching 45%. The C2 and C3 product distribution and production rate for NGQD-catalysed carbon dioxide reduction is comparable to those obtained with copper nanoparticle-based electrocatalysts.
Hydrogen-dependent reduction of carbon dioxide to formic acid offers a promising route to greenhouse gas sequestration, carbon abatement technologies, hydrogen transport and storage, and the sustainable generation of renewable chemical feedstocks . The most common approach to performing direct hydrogenation of CO2 to formate is to use chemical catalysts in homogeneous or heterogeneous reactions . An alternative approach is to use the ability of living organisms to perform this reaction biologically. However, although CO2 fixation pathways are widely distributed in nature, only a few enzymes have been described that have the ability to perform the direct hydrogenation of CO2 [3-5]. The formate hydrogenlyase (FHL) enzyme from Escherichia coli normally oxidizes formic acid to carbon dioxide and couples that reaction directly to the reduction of protons to molecular hydrogen . In this work, the reverse reaction of FHL is unlocked. It is established that FHL can operate as a highly efficient hydrogen-dependent carbon dioxide reductase when gaseous CO2 and H2 are placed under pressure (up to 10 bar). Using intact whole cells, the pressurized system was observed to rapidly convert 100% of gaseous CO2 to formic acid, and >500 mM formate was observed to accumulate in solution. Harnessing the reverse reaction has the potential to allow the versatile E. coli system to be employed as an exciting new carbon capture technology or as a cell factory dedicated to formic acid production, which is a commodity in itself as well as a feedstock for the synthesis of other valued chemicals.
Coal seam gas (CSG) production can have an impact on groundwater quality and quantity in adjacent or overlying aquifers. To assess this impact we need to determine the background groundwater chemistry and to map geological pathways of hydraulic connectivity between aquifers. In south-east Queensland (Qld), Australia, a globally important CSG exploration and production province, we mapped hydraulic connectivity between the Walloon Coal Measures (WCM, the target formation for gas production) and the overlying Condamine River Alluvial Aquifer (CRAA), using groundwater methane (CH4) concentration and isotopic composition (δ(13)C-CH4), groundwater tritium ((3)H) and dissolved organic carbon (DOC) concentration. A continuous mobile CH4 survey adjacent to CSG developments was used to determine the source signature of CH4 derived from the WCM. Trends in groundwater δ(13)C-CH4 versus CH4 concentration, in association with DOC concentration and (3)H analysis, identify locations where CH4 in the groundwater of the CRAA most likely originates from the WCM. The methodology is widely applicable in unconventional gas development regions worldwide for providing an early indicator of geological pathways of hydraulic connectivity.
Mutations in hemoglobin can cause a wide range of phenotypic outcomes, including anemia due to protein instability and red cell lysis. Uncovering the biochemical basis for these phenotypes can provide new insights into hemoglobin structure and function as well as identify new therapeutic opportunities. We report here a new hemoglobin α chain variant in a female patient with mild anemia, whose father also carries the trait and is from the Turkish city of Kirklareli. Both the patient and her father had a His58(E7)→Leu mutation in α1. Surprisingly, the patient’s father is not anemic, but he is a smoker with high levels of HbCO (~16%). In order to understand these phenotypes, we examined recombinant human Hb (rHb) Kirklareli containing the α H58L replacement. Mutant α subunits containing Leu58(E7) autooxidize ~8 times and lose hemin ~200 times more rapidly than native α subunits, causing the oxygenated form of rHb Kirklareli to denature very rapidly under physiological conditions. The crystal structure of rHb Kirklareli shows that the α H58L replacement creates a completely apolar active site, which prevents electrostatic stabilization of bound O2, promotes autooxidation, and enhances hemin dissociation by inhibiting water coordination to the Fe(III) atom. At the same time, the mutant α subunit has an ~80,000 fold higher affinity for CO than O2, causing it to rapidly take up and retain carbon monoxide, which prevents denaturation both in vitro and in vivo and explains the phenotypic differences between the father, who is a smoker, and his daughter.
Carbon nanofibers, CNFs, due to their superior strength, conductivity, flexibility and durability have great potential as a material resource, but still have limited use due to the cost intensive complexities of their synthesis. Herein, we report the high-yield and scale-able electrolytic conversion of atmospheric CO2 dissolved in molten carbonates into CNFs. It is demonstrated that the conversion of CO2 → CCNF + O2 can be driven by efficient solar, as well as conventional, energy at inexpensive steel or nickel electrodes. The structure is tuned by controlling the electrolysis conditions, such as the addition of trace transition metals to act as CNF nucleation sites, the addition of zinc as an initiator and the control of current density. A less expensive source of CNFs will facilitate its adoption as a societal resource, and using carbon dioxide as a reactant to generate a value added product such as CNFs provides impetus to consume this greenhouse gas to mitigate climate change.
We report selective electrocatalytic reduction of carbon dioxide (CO2) to carbon monoxide (CO) on gold (Au) nanoparticles (NPs) in 0.5 M KHCO3 at 25℃. Among monodisperse 4-, 6-, 8-, and 10-nm NPs tested, the 8 nm Au NPs show the maximum Faradaic efficiency (FE) (up to 90% at -0.67 V vs. reversible hydrogen electrode, RHE). Density functional theory (DFT) calculations suggest that the presence of dominant edge sites over corner sites (active for the competitive H2 evolution reaction) on the Au NP surface facilitates the stabilization of the reduction intermediates, such as COOH*, and the formation of CO. This mechanism is further supported by the fact that Au NPs embedded in a matrix of butyl-3-methylimidazolium hexafluorophosphate for more efficient COOH* stabilization exhibit even higher reaction activity (3 A/g mass activity) and selectivity (97% FE) at -0.52 V (vs. RHE). The work demonstrates the great potentials of using monodisperse Au NPs to optimize the available reaction intermediate binding sites for efficient and selective electrocatalytic reduction of CO2 to CO.
Nanoscopic uranyl coordination cages have been prepared by a facile route involving self-assembly via temperature and solvent-driven, in situ ligand synthesis. The synthesis of hydrogen arsenate and pyroarsonate ligands in situ enhances flexibility, which is an important factor in producing these compounds.
Binary co-catalysts of Pt and Cu2 O with a core-shell structure significantly enhance the photocatalytic reduction of CO2 with H2 O to CH4 and CO. The Cu2 O shell provides sites for the preferential activation and conversion of CO2 , whereas the Pt core extracts the photogenerated electrons from TiO2 . The deposition of Cu2 O shell on Pt nanoparticles markedly suppresses the reduction of H2 O to H2 .