Oxidation Step Research Articles

Superhydrophilicity and Electronic Modulation on Self-Supported Lignin-Derived Carbon Coupled with NiO@MoNi4 for Enhancing Urea Electrolysis.

Developing highly efficient biomass-derived carbon-based electrocatalysts remains challenging for urea electrolysis because most of these electrocatalysts show powder morphology, which can lead to Ostwald ripening during the reaction process, and its reaction mechanism should be further verified. Herein, self-supported lignin-derived carbon coupling NiO@MoNi4 heterojunction (NiO@MoNi4/C) possesses superhydrophilic properties and electronic modulation, boosting the performance of urea electrolysis. Electrochemical results show that an indirect oxidation step for urea oxidation reaction (UOR) and Volmer-Heyrovsky mechanism for hydrogen evolution reaction (HER) occurs on the surface of NiO@MoNi4/C. It displays low potentials for UOR (E10/500/1000 = 1.28/1.41/1.47 V) and for HER (E-10/-500/-1000 = -38/-264/-355 mV) in 1.0 MKOH + 0.5M urea electrolyte solution. The good activity is ascribed to the self-supported lignin-derived carbon and heterojunction, which increases the number of active sites, optimizes electronic structure, and improves electron transfer. Benefiting from the self-supported lignin-derived carbon, NiO@MoNi4/C demonstrates corrosion resistance and superhydrophilicity, which avoids Ostwald ripening and accelerates gas-liquid transfer, thus, maintaining for 100 h at ±1000/±1500 mA cm-2 during the UOR and HER test. This work provides a good catalyst for urea electrolysis and presents a promising way for preparing lignin-derived carbon-based catalysts while expanding the application of lignin-based biomass carbon materials.

Bilayered Phosphorus‐Doped Polysilicon Passivating Contact Structures for TOPCon Solar Cell Applications

ABSTRACTThe use of single‐layer polysilicon (poly‐Si) in tunnel oxide passivated contact (TOPCon) structures has demonstrated excellent passivation and contact performance. However, commercial TOPCon solar cell fabrication requires screen‐printing and cofiring techniques for electrode preparation. The single‐layer structure is less efficient at preventing metal atoms in the electrode paste from penetrating the silicon bulk. Furthermore, the uniformity of doping concentration and crystallinity within this structure poses challenges as it fails to optimally meet the intricate requirements for achieving superior performance in terms of passivation, contact, and mitigating parasitic absorption. In this study, the deposition process of the amorphous silicon (a‐Si) precursor layer using an in‐line magnetron sputtering system incorporated an additional plasma oxidation step, resulting in a bilayer poly‐Si structure with the newly introduced SiOx acting as a partition. Detailed investigations were conducted into the passivation quality, contact resistivity, crystallinity, and the distribution of critical atoms in the bilayer structure. Subsequently, the bilayer configuration was utilized in the manufacturing process of TOPCon solar cells. These efforts resulted in a notable enhancement in open‐circuit voltage (Voc) and short‐circuit current (Isc), leading to a 0.06% efficiency improvement, based on the average performance of ~200 cells per group.

The Catalytic Mechanism of a Highly Active Cobalt Chlorin Complex for Photocatalytic Water Oxidation.

Highly active catalysts for electrocatalytic and photocatalytic water oxidation are strongly demanded to realize artificial photosynthesis. A cobalt complex with a chlorin derivative ligand (CoII(Ch)) exhibited high activity for electrocatalytic water oxidation with an overpotential of 0.45 V at pH 9.0. Spectroelectrochemistry (UV-vis) unveiled the formation of two intermediates by successive one-electron oxidations. Also, the Pourbaix diagram depicted by the pH dependence of redox potentials indicated that the water oxidation proceeded after the oxidation of both the central cobalt ion and chlorin ligand with proton-coupled electron transfer (PCET). Then, the photocatalytic activity of CoII(Ch) was examined for water oxidation using [RuII(bpy)3]2+ (bpy: 2,2'-bipyridine) and S2O82- as a photosensitizer and a sacrificial electron acceptor, respectively. The turnover number, turnover frequency, and oxygen yield reached as high as 980, 5.2 s-1, and 98%, respectively, under optimized conditions. The O2-evolution rates increased in proportion to the square of the catalyst concentration in the reaction solution, suggesting that the formation of the O-O bond regarded as the rate-determining step of water oxidation proceeded by the interaction of two metal centers (I2M) mechanism in which two molecules of high-valent metal oxo or oxyl radical species react with each other.

Expediting the Volmer Step of Alkaline Hydrogen Oxidation with High-Efficiency and CO-Tolerance by Ru-O-Eu Bridge.

The quest for economical and highly efficient nanomaterials for the alkaline hydrogen oxidation reaction (HOR) is imperative in advancing the technology of anion exchange membrane fuel cells (AEMFCs). Efforts using Pt-based electrocatalysts for alkaline HOR are greatly plagued by their finitely intrinsic activities and significant CO poisoning, stemming from the difficulty of simultaneously optimizing surface adsorption toward different hydrogen-related adsorbates. Herein, Ru clusters coupled with Eu2O3 immobilized within N-doped carbon nanofibers (Ru/Eu2O3@N-CNFs) are developed toward drastically boosted electrocatalysis for HOR via a d-p-f gradient orbital coupling strategy. Theoretical calculations and in situ operando spectroscopy discover that the induction of Eu2O3 optimizes the Ru site electronic structure via constructing the gradient orbital coupling of Ru(3d)-O(2p)-Eu(4f), leading to optimal H intermediates, improved adsorption ability of OH and reduced energy barrier of water formation, and promoted CO oxidation, endowing the Ru/Eu2O3 as the promising catalyst alternative for fast alkaline hydrogen electrooxidation. As a result, the Ru/Eu2O3@N-CNFs reach an impressive kinetic current densities (jk) value of 156.3 mA cm-2 at 50 mV (38.4 times higher than Pt/C), and decent stability over 35000 s continuous operation. This comprehensive investigation featuring d-p-f gradient orbital coupling provides valuable insights for the strategic development of high-performance Ru-based materials for HOR and beyond.

Advanced Al Hydrogel Propellants: Preparation, Thermal Stability, and Self-Sustainable Combustion Characteristics.

A new group of Al-based hydrogel propellants has been prepared and evaluated, aiming to replace currently used Al-ice propellants. The theoretical specific impulse (Isp) of these formulations is around 235 s. To enhance the ignition and combustion performances of these propellants, a 2% metastable intermixed composite Al@PVDF-CuO and minor ammonium perchlorate (AP) were introduced. The measured maximum ignition temperature of these hydrogel propellants was 2277 °C, higher than that of the Al-ice propellant (1700 °C). This increase in the ignition temperature could be attributed to the enhanced reactivity and energy release provided by the additives. Additionally, the initial mass loss temperature for this kind of hydrogel propellant, ranging from 211 to 235 °C, indicates higher thermal stability compared to the evaporation temperature of moisture water, indicating the strong water-locking capability of the gelling agent triaminoguanidine-glyoxal polymer (TAGP). The two main reaction steps involved in the combustion process are the oxidation of Al by H2O with H2 release, which coincides with the decomposition of TAGP at 246 °C, and a subsequent oxidation step with remaining H2O and TAGP residues peaking at 320 °C. The burn rate of these propellants is stable and controllable, ranging from 2.5 to 5.9 mm·s-1, which is crucial for maintaining a consistent thrust during propulsion. The combustion condensed products are predominantly α-Al2O3, which could influence the overall combustion efficiency and thermodynamic properties of the system. The effect of AP on the Al-water reaction has been further studied using reactive force field (ReaxFF) molecular dynamic simulations. It has been shown that the presence of AP may lead to a slight decrease in H2 production, which was attributed to the increase in the H2O concentration as the major decomposition product of AP.

Surface Modification of Si3N4 via Silane Coating and Oxidation for Photocurable Slurry Preparation

To address the issues of low curing depth and high viscosity in VPP slurries caused by the high refractive index and hydrophilic surface of silicon nitride (Si3N4), this study proposes a novel surface modification method. The process starts with the pre-coating of Si3N4 powder using the silane coupling agent KH570. This is followed by an oxidation step that forms a uniform SiO2 layer on the powder surface, effectively reducing the refractive index mismatch between Si3N4 and the resin, as well as minimizing light scattering. The KH570 pre-coating also protects the Si3N4 lattice, mitigating oxidation-induced damage and preserving structural integrity. Subsequently, the Si3N4 powder undergoes further modification with the silane coupling agent KH560 to enhance the slurry’s flowability and stability. Using this three-step method of pre-coating, oxidation, and surface modification, a Si3N4 slurry with 45 vol.% solid content was successfully prepared. The slurry’s viscosity decreased by 20-30%, and under a laser power of 1200 mW, the curing depth increased by 52.9%, reaching a value of 192.7 μm with a viscosity of 7.69 Pa·s (at a shear rate of 30 s⁻1 and 47.8 rpm). This approach enables the fabrication of high-quality Si3N4 ceramic components with intricate geometries.

The catalytic reduction-oxidation collaborative processes for enhanced elimination of TBBPA over Pd/CeO2-R catalyst

The degradation of tetrabromobisphenol A (TBBPA) was inhibited due to the existence of strong electron attraction Br. The reduction of TBBPA usually generated bisphenol A (BPA), which still do harm to the environment. Herein, we prepared Pd/CeO2 catalysts for the valid elimination of TBBPA with clean products via the catalytic hydrodebromination-oxidation (R-O) synergy processes. TBBPA suffered debromination and BPA and Br- were the products after reaction for 60min during the catalytic hydrodebromination (HDBr) processes, BPA could be degraded smoothly in the following oxidation step involved PMS activation, reflecting an excellent ability of the Pd based catalyst for the activation of H2, C-Br bond and PMS. Both Pd0 and Pdn+ played key roles for the HDBr of TBBPA, while Pd0 was the main active sites for the oxidation of BPA. HOBr generated from Br- oxidation favored the removal of BPA while the reactive species such as 1O2 generated from PMS activation further accelerated the TOC removal. The TOC removal rate was 5.2% for the direct degradation of TBBPA in the PMS/DP-Pd/CeO2-R system, while this value increased to 57.5% in the R-O synergy system. In addition, after reaction for 120min to eliminate TBBPA, the products were friendly to the aquatic organisms in the R-O synergy system, while the products remain exhibited strong toxicity in the single oxidation system, highlighting the advantages of the Pd/CeO2 catalyst triggered reduction/oxidation cooperation processes.

Carboxymethyl cellulose assisted hydrothermal synthesis of litchi-like zinc ferrite nanoparticles for water remediation through visible photo-Fenton-like catalysis

The conventional methods for the synthesis of zinc ferrite (ZnFe2O4) basically require high temperature calcination oxidation step, which produces environmentally unfriendly high energy consumption and may produce harmful gases that pollute the atmosphere, as well as the calcination synthesis limits the application of ZnFe2O4 such as preparation of organic composite materials. To end this, by adding carboxymethyl cellulose (CMC) to the reaction system, homogeneous litchi-like ZnFe2O4/CMC nanoparticles were successfully synthesized without alkali and calcination in this paper. The rich carboxyl group of CMC is conducive to the chelation and fixation of metal ions in the reaction precursor, which greatly promotes the synthesis of ZnFe2O4. The synthesized particle size is ~100 nm, with obvious ZnFe2O4 diffraction peaks and good crystallinity. The photocatalytic performance of the synthesized photocatalyst was evaluated by visible light-Fenton-like method. With the activation of peroxymonosulfate (PMS), 80.27 % of tetracycline hydrochloride (TC) was degraded in just 18 min, suggesting that the synthesized catalyst had an excellent photocatalytic performance. After four cycles, the catalyst still could degrade 64.52 % TC. And the same behavior in XRD and FTIR spectra confirms the stability of the photocatalyst. In addition, it was determined that singlet oxygen (1O2) dominated the visible light catalytic degradation.

Multiplexed perturbation of yew reveals cryptic proteins that enable a total biosynthesis of baccatin III and Taxol precursors.

Plants make complex and potent therapeutic molecules, but difficulties in sourcing from natural producers or chemical synthesis can challenge their use in the clinic. A prominent example is the anti-cancer therapeutic paclitaxel (Taxol ® ). Identification of the full paclitaxel biosynthetic pathway would enable heterologous drug production, but it has eluded discovery despite a half century of intensive research. Within the search space of Taxus' large, enzyme-rich genome, we suspected the complex paclitaxel pathway would be difficult to resolve using conventional gene co-expression analysis and small sample sets. To improve the resolution of gene set identification, we developed a multiplexed perturbation strategy to transcriptionally profile cell states spanning tissues, cell types, developmental stages, and elicitation conditions. This approach revealed a set of paclitaxel biosynthetic genes that segregate into expression modules that suggest consecutive biosynthetic sub-pathways. These modules resolved seven new genes that, when combined with previously known enzymes, are sufficient for the de novo biosynthesis and isolation of baccatin III, an industrial precursor for Taxol, in Nicotiana benthamiana leaves at levels comparable to the natural abundance in Taxus needles. Included are taxane 1β-hydroxylase (T1βH), taxane 9α-hydroxylase (T9αH), taxane 7β- O -acyltransferase (T7ΑΤ), taxane 7β- O -deacetylase (T7dA), taxane 9α- O -deacetylase (T9dA), and taxane 9-oxidase (T9ox). Importantly, the T9αH we discovered is distinct and independently evolved from those recently reported, which failed to yield baccatin III with downstream enzymes. Unexpectedly, we also found a nuclear transport factor 2 (NTF2)-like protein (FoTO1) crucial for high yields of taxanes; this gene promotes the formation of the desired product during the first taxane oxidation step, resolving a longstanding bottleneck in paclitaxel pathway reconstitution. Together with a new β-phenylalanine-CoA-ligase, the eight genes discovered in this study enables the complete reconstitution of 3'- N -debenzoyl-2'-deoxy-paclitaxel with a 20-enzyme pathway in Nicotiana plants. More broadly, we establish a generalizable approach for pathway discovery that scales the power of co-expression studies to match the complexity of specialized metabolism, enabling discovery of gene sets responsible for high-value biological functions.

Construction of Axially Chiral 4-Aminoquinolines by Cycloaddition and Central-to-Axial Chirality Conversion.

A two-step strategy has been established for the enantioselective synthesis of 4-aminoquinolines possessing axial chirality. This approach involves a chiral phosphoric acid-catalyzed cycloaddition, followed by a DDQ oxidation step. The method offers efficient access to a variety of 1,1'-biaryl-2,2'-amino alcohol derivatives in excellent yields and enantioselectivities (up to 98% yield and 93% ee). Furthermore, the synthetic transformation of the products was also investigated.

(5+1)−1] Cyclization of Nitroepoxides to Pyridinium 1,4‐Zwitterionic Thiolates for the Synthesis of Indolizine Derivatives

AbstractThe synthesis of indolizine derivatives was achieved through the reaction of pyridinium 1,4‐zwitterionic thiolates with a diverse array of 2‐methyl‐2‐nitro‐3‐aryloxiranes. Subsequent investigations unveiled a synthetic route to indolizines via a stepwise [(5+1)−1] pathway, with unstable pyridothiazines serving as transient intermediates. DFT calculations elucidated that this transformation entails sequential annulation, deacylation, desulfurization, and oxidation steps.

Tracking Water Dissociation on RuO2(110) Using Atomic Force Microscopy and First-Principles Simulations.

The interaction between interfacial water and transition metal oxides is a primary enabling step for the oxygen evolution reaction (OER). RuO2 is a prototypical OER electrocatalyst whose ability to activate interfacial water molecules is essential to its OER activity. We image the dissociation of surface water into OH* and O* on RuO2(110), where * denotes adsorbed species, using atomic force microscopy. Starting from the surface-bound water molecules, which form a one-dimensional network along the rows of Ru surface sites, increasing the oxidative potential strips hydrogen away and transforms the water molecules into OH* and O*. This oxidative step changes the pattern of the adsorbates from one- to two-dimensional. First-principles calculations with interfacial polarization, capacitive charging, and adsorbate interactions attribute this evolution to the cooperative dehydrogenation of adsorbed water and OH* on RuO2. We use these results to map the surface phase diagram of RuO2(110) and provide a quantitative interpretation of its cyclic voltammetry. Our result provides the visualization of the water dissociation on a conductive oxide surface, a critical step in the OER, and demonstrates that the water activation is a collective phenomenon at RuO2(110) electrodes.

Al-N3 Bridge Site Enabling Interlayer Charge Transfer Boosts the Direct Photosynthesis of Hydrogen Peroxide from Water and Air.

Manipulating the electronic environment of the reactive center to lower the energy barrier of the rate-determining water oxidation step for boosting the direct generation of H2O2 from water, air, and sunlight is fascinating yet remains a grand challenge. Driven by a first-principles screening across a series of metal single atoms in carbon nitride, we report a class of an Al-N3 bridge site enabling interlayer charge transfer in carbon nitride nanotubes (CNNT-Al) for the highly efficient photosynthesis of H2O2 directly from water, oxygen, and sunlight. We demonstrate that the interlayered Al-N3 bridge site in CNNT-Al is able to activate the neighboring surface N atom for promoting the rate-determining step of the two-electron water oxidation to H2O2. It is also able to act as a bridge for enhancing the vertical interlaminar charge transfer due to the hybridization between the 3s and 3p states of the interstitial Al atom and the conduction band of two adjacent carbon nitride layers. Collectively, these factors lead to a highest photocatalytic mass activity of 1410.2 μmol g-1 h-1 (with a photocatalyst concentration of 1 g L-1) for direct photosynthesis of H2O2 out of all CN-based photocatalysts and a 7-fold higher solar-to-chemical conversion efficiency (0.73%) compared to that of the natural photosynthesis of typical plants (∼0.1%). Most importantly, the CNNT-Al-based flow reactor can steadily produce H2O2 for 200 h and be directly used for the on-site degradation of organic dye in water. The CNNT-Al-based flow reactor can also kill a 10 times higher concentration of bacteria in deionized water than that in natural water with 100% efficiency, which makes our design economically appealing for practical water treatment.

Mechanistic Insights on Coverage-Dependent Selectivity Limitations in Vinyl Acetate Synthesis.

Developing improved catalysts for sustainable chemical processes often involves understanding atomistic origins of catalytic activity, selectivity, and stability. Using density functional theory and steady-state kinetic analyses, we probe the elementary steps that form decomposition products that limit selectivity in vinyl acetate (VA) synthesis on Pd surfaces covered with acetate species. Acetate formation and coupling with ethylene control the VA formation catalytic cycle and steady-state coverage, but acetate and ethylene can separately decompose to form CO2. Both decompositions involve initial C-H activations at acetate vacancies, followed by additional C-H activations and eventual C-O formations and C-C cleavages involving reactions with molecular oxygen. Acetate decomposition paths with non-oxidative kinetically-relevant steps exhibit similar free energy barriers to oxidative paths. In contrast, the non-oxidative ethylene path involving an ethylidyne intermediate exhibits a much lower barrier than paths with oxidative kinetically-relevant steps. Ethylene decomposition is very facile at low coverages but is more coverage-sensitive, leading to similar decomposition and VA formation barriers at coverages accessible at steady state, which is consistent with moderate VA selectivity in measurements and ethylene vs. acetate decomposition contributions assessed from regressed kinetic parameters. These insights provide a detailed framework for describing VA synthesis rates and selectivity on metallic catalyst surfaces.

Combined thermochemical-biotechnological approach for the valorization of polyolefins into polyhydroxyalkanoates: Development of an integrated bioconversion process by microbial consortia

Waste management of persistent polymers such as polyolefins (PO)1 still represents a major challenge, often leading to material loss from the value chain and contributing to plastic pollution. This study investigated an integrated process to valorize PO pyrolysis side stream. PO wax was recovered and used as a feedstock for a microbial bioconversion process. A modified emulsification protocol (using two-surfactants system) allowed the successful dispersion and bioconversion of PO wax without the need of the extra oxidation step. Enrichment of plastic landfill inocula allowed to develop efficient mixed microbial consortia (MMC) able to grow on PO wax. Adaptive laboratory evolution improved 4 times cell growth, leading to 2.6–17.3 times shorter lag phase. The bioconversion process using the adapted MMC was performed in a 2 L-bioreactor with PO wax-emulsified media (10 g L−1) at neutral pH and 20% pO2. 87% of substrate was consumed within 12 h and complete consumption was achieved within 48 h (4 times faster than previously reported). A maximum of 2.95 gCDW L−1of biomass was produced, while the intracellular triglycerides reached a maximum of 105.5 mg L−1 at 30 h. Moreover, the conversion of PO wax into polyhydroxyalkanoates (PHAs) was demonstrated and the production was maximized by statistical optimization. Maximum PHA titer of 384 0.1 mg L−1 was achieved, which represents a 1.5–17 times improvement from previous reports. This integrated thermochemical-biotechnological approach might represent an interesting strategy to valorize and upcycle currently unrecyclable PO-rich mixed plastic waste streams, thus improving the circularity of the plastic sector.

Independent evolution of plant natural products: Formation of benzoxazinoids in Consolida orientalis (Ranunculaceae)

Benzoxazinoids (BXDs) are important defense compounds produced by a number of species from different, evolutionarily unrelated plant families. While BXD biosynthesis has been extensively studied in the grasses (monocots) and core eudicots, the mechanism of BXD synthesis in the basal eudicots is still unclear. We used an integrated metabolomics and transcriptomics approach to elucidate the BXD pathway in Consolida orientalis, a Ranunculaceae species known to produce the BXD DIBOA-Glc. Overexpression of candidate genes in Nicotiana benthamiana identified a flavin-dependent monooxygenase (CoBX2-3) and two cytochrome P450 enzymes (CoBX4 and CoBX5) that catalyze the oxidation steps that transform indole into DIBOA. Co-expression of CoBx2-3, CoBx4, and CoBx5 with the previously described indole synthase gene CoBx1 and the UDP-glucosyltransferase gene CoBx8 in N. benthamiana resulted in the reconstitution of a fully active BXD pathway. The fact that CoBX2-3, CoBX4, and CoBX5 are not phylogenetically related to their counterparts in the grasses and core eudicots suggests independent evolution of benzoxazinoids biosynthesis in these three angiosperm lineages.

Exploring the Physicochemical, Antioxidant and Sensory Properties of the Flavoured Virgin Olive Oil With Chavir Extract During Storage

ABSTRACTThis study aimed to study the impact of Ferulago angulata (Schlecht) Boiss (known as an antioxidant known as Chavir) extract, obtained through ultrasound‐assisted extraction (UAE), on the physicochemical, antioxidant and sensory properties of virgin olive oil (VOO) during a 90‐day storage period at room temperature. For this purpose, different concentrations of Chavir extract (100, 200 and 300 ppm) were added to VOO. Key parameters, including total phenol content (TPC), extract composition by HPLC‐DAD and quality indicators like acidity value (AV), p‐anisidine value (p‐AV) and UV indices (parameters: K232, K270 and ΔK), were determined. AVs increased overall during the storage period, but adding Chavir extract at 300 ppm appeared to counteract the rise in free fatty acids, suggesting a potential role in reducing hydrolysis. p‐AVs decreased in unflavoured and flavoured samples, indicating reduced oxidation in Chavir‐flavoured VOO. K232 values exhibited a decline in the presence of flavouring agents and their concentrations. In contrast, the values of K270 showed an increase over the storage period, which indicated the formation of aldehyde and ketones in the second oxidation step. All samples maintained ΔK values below permissible limits (≥ 0.01), signifying good stability. The sensory evaluation emphasised positive attributes such as bitterness, fruitiness and pungency, indicating the high quality of VOO. The addition of Chavir extract further enhanced all of these positive characteristics, particularly at the 300 ppm concentration. However, a gradual decline was observed in all these attributes over time. Notably, the Chavir extract played a crucial role in delaying the formation of secondary oxidation products, which contribute to negative attributes like rancidity in VOO. Moreover, adding Chavir extract increases oxidative stability, infuses the positive qualities in VOO and provides valuable insights into its potential applications for enhancing the overall quality of VOO during storage. This enhancement not only helps maintain high quality and nutritional value but also makes the product more appealing to consumers.

CO2 utilization and on-purpose ethylene production: A chemical looping approach

CO2-assisted ethane dehydrogenation (CO2-ODHE) is a promising carbon atom economy process for upgrading CO2 to CO in tandem with C2H6 to C2H4 conversion. Iron oxide-based materials are selective for on purpose ethylene production through CO2-ODHE. The feed admission mode was found to play an important role on catalytic performance. Alternating C2H6 (reduction step) and CO2 (oxidation step) feedstock to a fixed bed reactor (chemical looping concept, CO2-ODHE-CL) attained constant ethane and CO2 conversion per step at 600 °C, equal to ∼17.6 %, while C2H4 selectivity during the reduction step was ∼75 %. The lattice oxygen mobility is a descriptor for the materials used during the CO2-ODHE-CL, since low mobility resulted in an increased C-H bond scission selectivity, i.e., C2H4 production, during the reduction step. Temperature programmed 18O2 isotope exchange experiments, along with temperature programmed H2 – reduction, were employed to exemplify the latter statement, investigating the lattice oxygen reactivity of the examined materials and the mechanism through which the lattice oxygen is reacting. X-ray techniques (X-ray Diffraction, X-ray Raman Scattering Spectrometry, X-ray Absorption Spectrometry) along with structural modeling demonstrated that the formation of a spinel like arrangement between Mg and Fe, stabilized lattice oxygen and thus minimized the undesired C-C bond scission during the C2H6 step of CO2-ODHE-CL.

Ethane-oxidising archaea couple CO2 generation to F420 reduction

The anaerobic oxidation of alkanes is a microbial process that mitigates the flux of hydrocarbon seeps into the oceans. In marine archaea, the process depends on sulphate-reducing bacterial partners to exhaust electrons, and it is generally assumed that the archaeal CO2-forming enzymes (CO dehydrogenase and formylmethanofuran dehydrogenase) are coupled to ferredoxin reduction. Here, we study the molecular basis of the CO2-generating steps of anaerobic ethane oxidation by characterising native enzymes of the thermophile Candidatus Ethanoperedens thermophilum obtained from microbial enrichment. We perform biochemical assays and solve crystal structures of the CO dehydrogenase and formylmethanofuran dehydrogenase complexes, showing that both enzymes deliver electrons to the F420 cofactor. Both multi-metalloenzyme harbour electronic bridges connecting CO and formylmethanofuran oxidation centres to a bound flavin-dependent F420 reductase. Accordingly, both systems exhibit robust coupled F420-reductase activities, which are not detected in the cell extract of related methanogens and anaerobic methane oxidisers. Based on the crystal structures, enzymatic activities, and metagenome mining, we propose a model in which the catabolic oxidising steps would wire electron delivery to F420 in this organism. Via this specific adaptation, the indirect electron transfer from reduced F420 to the sulphate-reducing partner would fuel energy conservation and represent the driving force of ethanotrophy.

On the interaction of uric acid with ammonium molybdate in acidic medium

This communication is a theoretical organic chemistry study on the interaction of uric acid with ammonium molybdate in acidic medium (Gigli test for uric acid). Colour tests give rapid, visible, results. However, it is interesting know what is happening in the test tube at molecular level. In the present paper we describe the reaction route of the above mentioned assay. Each step is fully commented and the electron flow is also given. The key stages are: addition of molybdic acid to the C-C double bond, acidolysis of the organometallic ester with reduction to molybdenum (IV) and epoxide formation (oxidation step). Ring opening of the oxirane and reaction with water. A glycol is formed followed by opening of the five-member ring giving a carbonyl and an ureido chain. Finally, elimination of urea gives rise to 2,4,5,6-tetraoxo-hexahydropyrimidine (alloxan) which is hydrated. The blue colour observed (molybdenum blue) is a mixture of several oxides.