PPE−FeNPC−900 is used as the electrode material in a 6 M KOH electrolyte; it manifests a decent specific capacitance of 400 F g−1. The assembled symmetrical supercapacitor exhibits a high energy density of 12.8 Wh kg−1 at a 300 W kg−1 power density and excellent cycle stability. As a catalyst, it also exhibits a half−wave potential of 0.850 V (vs. RHE) and a diffusion-limited current of 5.79 mA cm−2 at 0.3 V (vs. RHE). It has a higher electron transfer number and a lower hydrogen peroxide yield compared to commercial Pt/C catalysts. The green, simple, and efficient strategy designed in this study converts abundant, low−cost waste biomass into high-value multifunctional carbon materials, which are critical for achieving multifunctional applications.This paper proposes a different strategy for deriving carbon materials from biomass, abandoning traditional strong corrosive activators and using a top−down approach with a mild green enzyme targeted to degrade the pectin matrix in the inner layer of pomelo peel cotton wool, inducing a large number of nanopores on its surface. Meanwhile, the additional hydrophilic groups produced via an enzymatic treatment can be used to effectively anchor the metallic iron atoms and prepare porous carbon with uniformly dispersed Fe−N As the global economy and population continue to grow, the global energy demand is increasing at an unprecedented rate. However, traditional fossil fuels are unable to meet this demand, necessitating the development of new energy storage and utilization technologies that are environmentally friendly, economically efficient, and high-performing. Among these technologies, supercapacitors, in particular, have shown excellent charge–discharge capabilities and outstanding stability ,2,3. MetPorous carbon materials have a high specific surface area (SSA) and high porosity with adjustable pore structure layering, good electrical conductivity, and stable physical and chemical properties, making them ideal for use as supercapacitor electrodes and ORR catalysts . RecentlPrevious studies have employed large amounts of strong corrosive chemicals  to treat pomelo peels for application in SCs, resulting in environmental pollution and impeding practical production ,18,19,20x structure with atomic dispersion anchored on the surface, and the best samples had a high SSA of 1453 m2 g−1. The structure and electrochemical performance were thoroughly characterized as supercapacitor electrodes and ORR catalysts.In this study, a novel approach was developed to produce efficient and versatile porous carbon materials without using harsh chemical reagents. Instead, the gentle treatment of pectin, a substance abundant in pomelo peel cell walls, with the help of a specific enzyme was carried out. This enzymatic process, known as enzymolysis, effectively broke down the pectin, creating numerous nanopores on the material’s surface. This resulted in an increased surface area and more active sites, ideal for further modifications. After this, Fe and N were doped onto the porous carbon to create an Fe−N3·6H2O), and ammonium chloride  were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., Shanghai, China.Pomelo peel was purchased from a local market in Jinan, Shandong Province, China. Pectinase was purchased from Xia Sheng enzyme retail store. Potassium hydroxide , ferric chloride hexahydrate  along with 75 μL and 150 μL of pectinase  and kept shaking at a constant temperature of 50 °C for 12 h, 18 h, and 24 h. Post enzymatic treatment, the pomelo peels were washed with deionized water and then dried in an oven at 60 °C. These treated peels were heated under nitrogen in a tube furnace at a heating rate of 5 °C·min−1 to 800 °C for 2 h and identified as PPC−Ex−y, where x represents the amount of pectinase and y represents the time of the enzymatic treatment. As control samples, pomelo peels that did not undergo enzymatic treatment were directly carbonized and named PPC.The fresh pomelo peels were prepared by removing their yellow skin and cutting their white cotton wool inner layer into 3 × 1.5 × 1 cm3·6H2O were dispersed in 50 mL of deionized water under sonication. The suspension was further dried in an oven at 80 °C. The dried sample was collected, ground together with 20 g of NH4Cl, and then subjected to various carbonation temperatures  in a nitrogen atmosphere at a heating rate of 5 °C·min−1 for a period of 2 h. The resulting black solid was washed with 1.0 M of hydrochloric acid for 24 h to wash away the iron oxide within it and then washed with deionized water. The final product was named PPE−FeNPC−T, where T represents the pyrolysis temperature, and it was dried at 60 °C overnight.The PPC−E150−18 carbon precursor was selected to prepare Fe, N−doped carbon materials. Firstly, 1.0 g of PPC−E150−18 and 0.5 g of FeClTo investigate the impact of enzymatic treatment and the role of Fe atom doping, different comparison samples were prepared from PPC or PPC−E150−18 as carbon precursors for comparison with the optimal sample PPE−FeNPC−900. These included PPE−PC−900, which was obtained via the direct carbonization of PPC−E150−18; PPE−NPC−900, which was obtained from PPC−E150−18 without Fe atom doping; and PP−FeNPC−900, which was obtained from PPC without enzymatic treatment.All electrochemical performances were studied using a CHI 760E electrochemical workstation. The details on the procedures used for the preparing electrodes and conducting electrochemical measurements for supercapacitors’ application and use as the catalyst for ORR are provided in the Supporting Information.3·6H2O to the resulting carbon precursor (PPC−E) suspension was followed by low−temperature pyrolysis. During this process, the abundant hydrophilic groups  of PPC−E coordinated with iron ions [3+ in the aqueous solution was hydrolyzed to amorphous Fe(OH)3 and FeO(OH) crystals (Equations (1) and (2), and 4Cl, the FeO(OH) crystals in FeO(OH)@PPC−E were initially converted into Fe2O3 (Equation (3)), and when the temperature was >700 °C, the reducing substances  produced during the pyrolysis of pomelo peel reduced Fe2O3 to Fe3O4 or further to metallic Fe, which subsequently reacted with volatile HCl to form volatile FeCl3 and promoted the decomposition of NH4Cl (Equations (4)–(7)). The coordinated iron atoms on the carbon precursor were immobilized by the N species generated from NH4Cl’s decomposition, forming Fe−N−C. FeCl3·6H2O and NH4Cl also contributed to the creation of specific microporous and mesoporous structures in the resulting carbon material [As shown in ron ions , and thematerial ,25. Fina2 g−1, respectively, with PPC−E150−18 exhibiting a larger SSA. Additionally, severe structural damage occurred when the enzyme dosage was 150 μL and the enzymatic treatment time was 24 h . Additionally, the XRD pattern also displayed peaks at 2θ = 30.1° and 43.1°, which were attributed to the Fe3O4 lattice plane (PDF#19−0629). These indicated that the FeO(OH) deposited on the carbon precursor was converted into Fe2O3 below 800 °C, and some of the Fe2O3 was reduced to Fe3O4 via pyrolysis. For sample PPE−FeNPC−900, the number of Fe2O3 (PDF#33−0664) diffraction peaks decreased, accompanied by an increasing number of Fe3O4 (PDF#19−0629) diffraction peaks, suggesting a further pyrolytic reduction of Fe2O3 to Fe3O4. At 1000 °C, the Fe2O3 lattice plane disappeared, and the number of Fe3O4 lattice plane peaks was similarly small, indicating the complete pyrolytic reduction of Fe2O3 to Fe3O4 and Fe3O4 to other amorphous substances. The disappearance of diffraction peaks of Fe2O3 and Fe3O4 might also indicate that acid washing was effective in removing Fe2O3 and Fe3O4 , indicating the presence of micropores in the samples, and a hysteresis loop in the high−pressure region (P/P0 = 0.4–1.0) signified the presence of mesopores in the samples [x structures (in agreement with the XPS results) contributed to the development of additional micropores. The pore structure, primarily characterized by these newly formed micropores, accounted for the slight reduction in average pore size. When the pyrolysis temperature increased to 1000 °C, the average pore size decreased to 2.92 nm, and the mesopore volume declined significantly, suggesting that an excessively high pyrolysis temperature led to the collapse of the pore structure. PPE−FeNPC−900 exhibited the largest SSA and the optimal micropore and mesopore structures, indicating that 900 °C was the optimal pyrolysis temperature. It was also observed that fewer micropores were created in sample PP−FeNPC−900 than in sample PPE−PC−900, revealing that NH4Cl and FeCl3·6H2O could play an activating role during the pyrolysis process, but they were less effective than enzymatic treatment. When comparing samples PPE−NPC−900 and PPE−FeNPC−900, it was found that introducing FeCl3·6H2O not only significantly increased the SSA of the samples but also enhanced their micropore volume and reduced their average pore size. This may be attributed to the formation of the Fe−Nx structure, which could prevent the collapse of micropores to mesopores due to high−temperature pyrolysis. It can be concluded that enzymatic treatment, NH4Cl, and FeCl3·6H2O pyrolysis were essential factors in creating the unique surface structure and high SSA of pomelo−peel−based porous carbon materials. The pore size distribution  and G peaks (graphite structure), respectively [D/IG) could be compared across all samples to assess the extent of defects [D/IG value of 1.01 , which is consistent with the maximum curve area of its CV curve and demonstrates its reliability regarding maximum capacitance. The GCD curves of PPE−FeNPC−900 at current densities of 0.5–10 A g−1 are shown in −1 at a current density of 0.5 A g−1. During rapid charging and discharging, the electrolyte was unable to completely permeate the electrode surface at elevated current densities, leading to a reduction in specific capacitance [−1, a high specific capacitance of 312 F g−1 (78% capacitance retention) could still be achieved, displaying an excellent rate performance, even surpassing that of the biomass−derived carbon materials described in recent publications , and the cross−axis intercept is related to the equivalent series resistance (Rs) [s, indicating its lowest internal and interfacial resistance, with higher accessibility of the surface to electrolyte ions [s, Rct, and Zw (ion diffusion resistance) are provided in ct value. Since Rct was closely associated with the charge transfer capacity of the electrodes, the lowest Rct indicated that electrodes prepared from PPE−FeNPC−900 displayed an enhanced charge transfer and superior electrical conductivity [The ion transport and charge transfer rates of the samples were studied using EIS. nce (Rs) . A largeyte ions . Utiliziuctivity . The low2 > 0.99) at different potentials. Generally, b−values were utilized to assess the kinetics of redox reactions, and a b−value approaching 1 indicated that the reaction kinetics corresponded to a fast surface−controlled process [The fast charging/discharging kinetics of PPE−FeNPC−900 were investigated using Equations (S2) and (S3).  process . The b−v−1. −1. The significant improvement in rate capability could be attributed to the significant contribution of surface−controlled capacitance. This was mainly due to the highly accessible surface area and appropriate pore structure of PPE−FeNPC−900, which resulted in a substantial EDLC. The surfaces containing abundant micropores and mesopores acted as an ideal electrolyte ion storage buffer, which facilitated short spreading distances of ions to the inner surface, thereby enhancing electron transfer.Moreover, the contributions of different capacitors were further compared quantitatively using Equation (S4). As shown in −1, indicating good EDLC characteristics and rate performance. The GCD curves  and (S7) to assess their performance for practical applications. −1 at a power density of 300 W kg−1 and remained at 8.3 Wh kg−1 at a power density of 6000 W kg−1. As depicted in −1, yielded a capacitance retention rate of 96% and a coulombic efficiency of approximately 100% after 10,000 cycles, indicating outstanding electrochemical stability and high reversibility  was equal to that of 20% Pt/C and higher than that of other samples. At +0.300 V, the diffusion limit current of sample PPE−FeNPC−900 exceeded that of commercial Pt/C (20 wt%). 2 is proportional to the dissolved concentration of O2 in the electrolyte, and it also revealed that the catalyst’s action had first−order reaction kinetics. The catalysis conformed to first−order reaction kinetics. The electron transfer number of sample PPE−FeNPC−900 at 0.6 V was 3.94, which confirmed that the reaction was a four−electron transfer process.The performance of PPE−FeNPC−900 as a catalyst in an ORR was assessed using cyclic voltammetry . All thes carbon . The ons2O2 yields were determined via the calculation of the ring current and disk current data via Equations (S10) and (S11)  and the slopes of other samples. This suggests that PPE−FeNPC−900 and Pt/C share similar catalytic mechanisms, and the initial electron reduction process of oxygen was likely the rate−determining step. Therefore, the PPE−FeNPC−900 catalyst demonstrated superior ORR performance, even surpassing that of Pt/C, due to its high specific surface area and abundant microporous mesopore structure, which enabled the full exposure of the uniformly dispersed Fe−Nx structure and electrocatalytic active sites.To analyze the ORR kinetics, the electron transfer number (n) and Hnd (S11) . The elemV dec−1 , which i2−saturated 0.1 M KOH. After 40,000 s, the current of the electrode loaded with commercial Pt/C diminished to only 51.2% of its initial current  and ORR catalyst . Importantly, the abundant raw materials used in and simplicity of the preparation process provided a novel, green, straightforward, and efficient method for the large−scale production of high−performance energy materials, which is expected to offer new opportunities for the future study of multifunctional carbon materials derived from biomass and open new possibilities for the development of environmentally friendly materials for multifunctional applications.In the current work, high−specific surface area Fe, N−doped porous carbon materials were successfully synthesized using the versatile pomelo peel as the carbon source via enzymatic treatment. This study not only eliminated the traditional treatment with strong corrosive chemicals and made it easier to scale up but also expanded the application scope, as the prepared porous carbon materials could be optimally applied to supercapacitors and ORR catalysts. The prepared PPE−FeNPC−900, with its abundant micro− and mesopores, high specific surface area, multi−atom doping, and homogeneously dispersed Fe−N


The responses were calcium-dependent since their generation was inhibited by lanthanum, a calcium channel inhibitor (2 mM), and EDTA, a calcium chelator (0.5 mM). The electrical signals were partially dependent on glutamate receptor (GLR) ion channels since knocking-out the GLR genes only slightly reduced the amplitude of the responses. The basal part of the gametophyte, which is rich in protonema cells, was the most sensitive to H2O2. The measurements carried out on the protonema expressing fluorescent calcium biosensor GCaMP3 proved that calcium signals propagated slowly (>5 µm/s) and showed a decrement. We also demonstrate upregulation of a stress-related gene that appears in a distant section of the moss 8 min after the H2O2 treatment. The results help understand the importance of both types of signals in the transmission of information about the appearance of ROS in the plant cell apoplast.Electrical and calcium signals in plants are some of the basic carriers of information that are transmitted over a long distance. Together with reactive oxygen species (ROS) waves, electrical and calcium signals can participate in cell-to-cell signaling, conveying information about different stimuli, e.g. abiotic stress, pathogen infection or mechanical injury. There is no information on the ability of ROS to evoke systemic electrical or calcium signals in the model moss Physcomitrella nor on the relationships between these responses. Here, we show that the external application of hydrogen peroxide (H Physcomitrium patens) had to cope with exposure to UV radiation, ozone, wounding and many other abiotic and biotic stressors that enhance the synthesis of reactive oxygen species (ROS)  , 2020. Pes (ROS) . It is wes (ROS) .2+ fluxes from external and internal stores were involved in the generation of APs in Physcomitrella. They interacted with K+ and, to a lesser extent, with Cl− fluxes. Our recent study on GCaMP mutants allowing the monitoring of changes in the cytoplasmic Ca2+ concentration ([Ca2+]cyt) demonstrated that the local Glu application caused an increase in [Ca2+]cyt confined to the site of the Glu treatment, whereas AP was transmitted to distant cells  AtGLR3.3 and AtGLR3.6 were identified as key players in wound-induced SWP generation and transmission  key genes and other stress-related gene expressions  after illumination with light of sufficient (over-threshold) intensity, cooling, glutamate (Glu) treatment, etc. , 2020. Ent cells . This waependent . In the smission . Both geressions .2+]cyt wave formation and transmission, a ROS-based component supplements the long-distance signaling system (2−), which is quickly converted to hydrogen peroxide (H2O2). They possess EF-hand motifs that are activated upon binding of Ca2+ to enhance ROS production , was discovered  plants and KOglr1 mutants treated with H2O2. We demonstrated that in the WT plants, H2O2 evoked the electrical signals recorded both in the gametophyte leaves and protonema and the calcium signals predominantly in protonema. The susceptibility of the protonema to the treatment was much higher than in the leaf cells (0.5 mM versus 5 mM). These signals were blocked by La3+—a calcium channel inhibitor—and by EDTA—a Ca2+ chelator. In the KOglr1 mutants, the electrical signals were reduced but not totally blocked, which reveals that GLR channels are not crucial in H2O2-induced membrane potential changes and Ca2+ fluxes in Physcomitrella. The involvement of other factors affecting [Ca2+]cyt is discussed. Looking for the downstream effects of the signals, we demonstrate an enhanced expression of stress-related genes.The goal of our study was to examine for the first time the effect of the H tissues , to addr2O2 evoked systemic electrical signals in the form of membrane potential changes transmitted along the plant. The long-distance responses transmitted from the basal part of the plant (from the rhizoid side) and recorded in apical leaf cells are presented in 2O2 concentrations influenced both the amplitude and the membrane potential characteristic of the response. Stimulation of the basal part of the plant with 0.05 mM and 0.1 mM H2O2 evoked irregular membrane potential changes with similar amplitude, duration and rate of depolarization  and reached more positive values. The amplitude of the depolarization (A) amounted to 68 ± 3 mV (n = 19) and was ∼30 mV higher than after treatment with 0.05 and 0.1 mM H2O2, respectively. Another difference occurred in the shape of the responses, where after the peak of depolarization evoked by 0.5 mM H2O2, a several-minute plateau of the membrane potential was recorded.The microelectrode measurements carried out on leaf (phylloid) cells from the Physcomitrella gametophyte proved that the application of H2O2 in the concentration of 0.5 mM to compare the transmission ability of electrical signals in the opposite direction—from the apical to the basal part of the plant , lower amplitude  and lower voltage at the peaks of the signals (V(max) = −142 ± 8 mV, n = 9). The additional feature was an absence of a characteristic plateau of the membrane potential. The shape of the membrane potential changes resembled the responses obtained after direct stimulation of a cell in the apical part of the plant (2O2 concentration (to 5 mM) evoked responses similar to these transmitted from the basal part after 0.5 mM H2O2 administration. These results indicate that the highest susceptibility to H2O2 occurs in the basal part of the plant having protonema cells and rhizoids, which act as an initial place for the generation of long-distance electrical signals propagated toward the plant apex. The results also showed that an increase in the H2O2 concentration facilitates the generation of fully developed responses resembling APs.We used Hn = 9). Lanthanum also shifted the membrane potential (V(0)) to positive values . The depolarization after the lanthanum application was slower  and reached more negative values (V(max) = −128 ± 5, n = 9) than in the control plants. After a washout of lanthanum from the measuring chamber, the amplitude of the responses increased to 27 ± 4 mV (n = 4), which indicated that the inhibition of the responses by lanthanum is partially reversible. EDTA totally blocked the responses in 9 of the 18 tested cells. Similar to lanthanum, EDTA evoked the reduction of the amplitude , the shift of the membrane potential to more positive values  and the reduction of the rate of depolarization . The shift of the membrane potential after EDTA was partially reversible since a washout resulted in a restoration of the membrane potential close to the values measured in standard solution .APs belong to the basic long-distance electrical signals recorded in plant cells whose generation is dependent on an influx of calcium ions into the cytoplasm. We decided to study the dependence of the recorded responses on the presence of an inhibitor of calcium channels (2 mM lanthanum) or a calcium chelator (0.5 mM EDTA), respectively  and the duration measured in half of the amplitude . Surprisingly, weaker effects were achieved by the direct stimulation of the tested cell or the stimulation of adjacent cells located close to the tested cell. This method of stimulation evoked electrical signals with a smaller amplitude  than when H2O2 was applied in the gametophyte base. The responses recorded in the protonema after the direct or indirect stimulation also exhibited a low depolarization rate , compared to the responses in the basal part of the gametophyte  or those recorded in the leaf cells. Cell-to-cell transmission of the electrical signal evoked by stimulation of the single protonema cells was rarely recorded and occurred only in 2 out of 18 tested plants . In the Ppglr1KO mutants, as in the WT, electrical signals propagated from the base of the gametophyte to the leaf and protonema cells  and a lower depolarization rate . The amplitude and rate of depolarization of responses in the protonema cells from Ppglr1KO recorded after the stimulation of the basal gametophyte part reached similar values to those recorded in the WT protonema cells . As in the WT protonema cells, the direct or indirect stimulation of the cells from Ppglr1KO evoked a smaller amplitude  and a lower depolarization rate  than after the stimulation of the basal part of the Ppglr1KO gametophyte. All these changes in the parameters of membrane potential changes in the protonema cells are presented in One of the candidates responsible for cell-to-cell communication in plants is the GLR, which can act as a non-selective calcium-permeable channel. The participation of the GLR in the transmission of electrical signals recorded in our experiments was tested with the use of a 2O2 evoked calcium waves which propagated from cell to cell in thread-like protonema cells. In contrast to electrical signals, the calcium signals were slower and appeared a few minutes after the application of the stimulus (n = 4) and 5.2 ± 0.3 µm/s (n = 7), respectively. A characteristic trait of some recorded calcium signals was its decrement with distance  in all leaves . Here, the gene encoding a galacturonosyltransferase-like 10 protein (AT3G28340) was 5-fold upregulated 5 min after the light stress treatment  and hence was selected for further analysis. For Pp3c5_28420V3.1, an increase in gene expression was detectable . The candidates were selected based on homology to Arabidopsis genes differentially expressed after local stress stimulus . In thatreatment . In PhysP search  against P search . In anal2O2. Apices of gametophores were harvested after treatment with 0.5 mM H2O2 at the base for 8 min (P = 0.00184) was observed (P = 0.06075). Thus, a local stress stimulus (here H2O2 at the gametophore base) triggers alteration of gene expression within 8 min in distant sections (here apex) in Physcomitrella.For these two selected candidates, we tested whether both genes are regulated in gametophore sections distant from a local treatment with H2O2) evokes a systemic response in the form of electrical and calcium signals to analyze the interdependence of these signals and their impact on gene expression in distant regions.Plant cell signaling is based mainly on the generation and transmission of different types of signals including electrical, calcium and ROS. Investigations of the relationship between these signals allow unraveling signaling pathways triggered in response to biotic and abiotic stresses. In this study, we tried to answer the question of whether the external application of ROS , also indicates a low probability of the appearance of a calcium-associated ROS wave. The ability to evoke local calcium signals but not self-propagating calcium waves by the extracellular H2O2 application implies the engagement of some other factors taking part in the transmission of information about such stimuli. It seems that, in P. patens, electrical signals, which appear at the moment of stimulation and propagate along the whole plant, are a proper carrier of the information about H2O2 enhancement. There still remains the question of the relationships between electrical, calcium and ROS signals.As shown by the results of our study, Hmulation . Calciummulation , where t2O2) to activate different ion channels  are paralogs to GLR clade III from Arabidopsis  or the calcium chelator (EDTA)  . A patchcurrents . Involvecurrents , but thecurrents  leading currents . The rol by TPC1 .2O2 at the base of gametophores was sufficient to trigger an increase in gene expression in the apex of a component of the homogalacturonan biosynthesis (2O2. Both selected candidates are homologs of an Arabidopsis isoform (AT3G28340) whose gene expression is regulated via ROS waves  were used for the analysis of membrane potential changes in leaf and protonema cells with the use of the microelectrode technique. A Physcomitrella mutant expressing GCaMP3 was used for the fluorescence imaging of changes in the calcium concentration. The plants were grown in a growing chamber  at a photoperiod of 16-/8-h light/dark, with light intensity 50 µmol/m2 s and at a temperature set to 23°C.Physcomitrella gametophytes were grown on Knop solid agar medium  in 160-mP. patens (Hedw.) Mitt.; 2PO4, 250 mg/l KCl, 250 mg/l MgSO4 × 7 H2O, 1,000 mg/l Ca(NO3)2 × 4 H2O and 12.5 mg/l FeSO4 × 7 H2O was prepared as described by 3BO3, 845 mg/l MnSO4 × 1 H2O, 431 mg/l ZnSO4 × 7 H2O, 41.5 mg/l KI, 12.1 mg/l Na2MoO4 × 2 H2O, 1.25 mg/l CoSO4 × 5 H2O and 1.46 mg/l Co(NO3)2 × 6 H2O) was also prepared as described by Physcomitrella WT protonema  was performed as described by L21 coding for the ribosomal protein L21  with ∆CT = CT[GOI] − CT[reference]. P < 0.05.Extraction of RNA was done with the innuPREP Plant RNA Kit  using the extraction buffer ‘PL’. Of the total RNA, 5 µg was treated with DNAseI  at 37°C for 1 h, and integrity of the RNA was checked on agarose gels. Two-microgram DNAseI digested RNA was used for reverse transcription using the TaqManpcad051_SuppClick here for additional data file.


Coherent with proposed elementary steps, we expose products of CH4 dehydrogenation + to CO2 in a ring electrode ion trap. Product analysis and reaction kinetics indicate a predisposition of the tetramers for C−O coupling with a conversion to products of CH2O, whereas atomic cations enable C−C coupling yielding CH2CO. Selected experimental findings are supported by thermodynamic computations, connecting structure, electronic properties, and catalyst function. Moreover, the study of bare Ta1,4+ compounds indicates that methane dehydrogenation is a significant initial step in the direct coupling reaction, enabling new, yet unknown reaction pathways.Understanding molecular‐scale reaction mechanisms is crucial for the design of modern catalysts with industrial prospect. Through joint experimental and computational studies, we investigate the direct coupling reaction of CH How the tantalum cluster cations catalyze: The cationic tantalum atom and the cationic tetramer exhibit a strong size‐dependent reactivity with methane and carbon dioxide: The monomer yields products from C−C coupling reactions, while the tetramer enables the formation of formaldehyde or syngas. When facing challenges such as climate change and a human's reliance on fossil fuels, the design and application of heterogeneous catalysts towards the activation of these small molecules is one of the main focuses of modern chemistry.4 and CO2 has been applied on an industrial scale to produce syngas (CO+H2).4 and CO2 under mild conditions, yielding higher oxygenated hydrocarbons. However, it requires a catalyst enabling simultaneous CH4 and CO2 activation followed by the coupling of the two substrates, i. e., C−C or C−O bond formations.Direct conversion of carbon dioxide CH2+, and Ta(O)CH2(CO2)1,2+. The underlying reaction mechanism determined by pseudo‐first order kinetics confirms the process to start with two competing parallel reactions. While Ta(O)CH2+ is formed through CO2 deoxygenation on the carbene, the presence of TaO+ indicates that TaCH2+ can also undergo a C−C coupling with CO2 followed by the loss of a C2H2O moiety. Both intermediates can, however, react further with CO2: TaO+ can deoxygenate another molecule of CO2 to form TaO2+, and Ta(O)CH2+ is converted either into Ta(O)CH2(CO2)1,2+ through adsorption of CO2 or into TaO2+ by virtue of a possible C−C coupling with concomitant elimination of a C2H2O moiety. Overall, the primary gaseous reaction products are postulated to be CO formed in a deoxygenation step and ketene, CH2CO (ethenone). Note that the formation of the ketene is energetically favored over other possible structural isomers such as ethynol or an oxirene.As several studies reported the dissociative adsorption of methane to a metal core to be the first step in the CH−9 cm3 s−1; see Table S1) is, however, significantly higher than in the FT‐ICR experiment (1.3×10−10 cm3 s−1) reported in that study, related most likely to the different reaction conditions in both studies. In addition to that, the kinetic fit identifies a new coupling reaction, which occurs directly from TaCH2+ in a single‐step process without the necessity to generate Ta(O)CH2+. A more detailed kinetic analysis reveals that CO2 deoxygenation as a first step is preferred over C−C coupling with a branching ratio of 5 : 1. Yet, as the subsequent C−C coupling on Ta(O)CH2+ is suppressed by a factor of 2.2 in comparison to CO2 adsorption (3 : 7), the contribution of both pathways to the formation of CH2CO yields ∼40 %.It should be stressed that the observation of the two‐step coupling, i. e., deoxygenation followed by coupling, is in good agreement with the earlier measurement of Wesendrup and Schwarz performed under single collisional conditions.2+ and Ta3+  impedes the study of their products from methane dehydrogenation, the only remaining cluster that facilitates this reaction with this hydrocarbon is Ta4+.4CH2]+ with CO2, several species are detected in the mass spectra, as shown in Figure 4(C)O+ and traces of Ta4C+, Ta4(C)O2+, and Ta4C(CO2)+. As the reaction progresses, further oxygenated species, Ta4(C)O2–7+, appear, along with CO2 adsorption products, Ta4(C)O1–7(CO2)+. According to the kinetic models, Ta4CH2+ is exclusively dissociated either into a formaldehyde‐like (H2CO) species or a syngas (H2+CO) with an overall rate coefficient of 13.1×10−9 cm3 s−1 (see Table S2). After that, further carbon dioxide molecules are either adsorbed or deoxygenated. It should be noted that Ta4(C)O(CO2)+ ions are considerably lower in intensity than Ta4(C)O2+ and rapidly disappear with decreasing intensity of the corresponding reactant ion, i. e., Ta4(C)O+, as a result of a reversible reaction.As the low ion abundance of bare Ta4 and CO2 coupling. Whereas the single atom promotes C−C coupling, the tetramer facilitates C−O coupling. It ought to be mentioned that parts of the atomic tantalum ion pathway have been examined extensively in the literature.+ with O2,2 is a process of much higher exothermicity (as for example evidenced by pathways resulting in the fragmentation of the cluster) and the pathway mentioned in that work is only a minor reaction channel. In any case, the formation of syngas molecules represents a plausible option in addition to the release of formaldehyde, as such a reaction outcome has recently been reported for rhodium–titanium oxide anions.2O species might be either a formaldehyde molecule, CO/H2, or a mixture thereof. Figure 2O formation has to be expected. The overall reaction equation can therefore be written as:While for atomic tantalum ions the spin state plays a fairly significant role, it is known that cationic tantalum tetramers prefer to be in a doublet state.For both species, the atomic cation and the cationic tetramer of tantalum, the resulting products are energetically favored by less than 1 eV. Thus, they do not represent deep thermodynamic sinks and may be accessible for consecutive reactions leading to the closure of a catalytic cycle.+ cations with methane and carbon dioxide at 300 K under multi‐collisional conditions, for which the kinetic fits, shown in Figure S1, result in the corresponding rate coefficients given in Table S3. As the CO2 deoxygenation proceeds far more rapidly than the CH4 dehydrogenation, this reaction is probed by using a reaction gas mixture containing only small amounts of carbon dioxide with the concentration of methane in the buffer gas being one or two orders of magnitude greater. Despite the complex reaction scheme, four types of reactions are identified, namely CH4/CO2 coupling, CO2 deoxygenation, CH4 dehydrogenation, and adsorption of both precursors. The experiment shows that both coupling reactions occur as identified previously in this work for the reaction of the carbene with CO2: while one reaction takes place via the Ta(O)CH2+ intermediate, the other one results from the direct conversion of TaCH2+ with CO2. The latter reaction yields TaO+, which is also formed from the Ta+ oxygenation by CO2. However, kinetic modeling reveals that the dominant process is coupling with a rate of (2.0±0.7)×10−8 cm3 s−1 while decarbonylation proceeds more than three times slower (see Table S3). It must be stressed that only the inclusion of both coupling reactions in the reaction sequence is capable to replicate the experimental data. The other reactions, such as the consecutive dehydrogenation of four methane molecules and the deoxygenation of two molecules of CO2, are consistent with previous experiments on the reaction of tantalum cations with methane and carbon dioxide.++CO2 is clearly identified again. Consequently, for both species, the cationic atom and the tetramer, the coupling reaction also occurs in mixtures of the two reactants.Analogously to the atomic cation, both molecules, CH2+, the product from methane dehydrogenation further reacts with carbon dioxide to form a Ta(O)CH2+ intermediate. Another CO2 molecule then enables the C−C coupling and the release of neutral C2H2O. The present experiments at elevated pressures confirm this pathway but also demonstrate a direct coupling of isolated TaCH2+ with CO2 with a similar ion yield as the two‐step process. We attribute this to different thermalization conditions in comparison to single collision studies. Surprisingly, the C−C coupling is completely suppressed when the reaction is mediated by tetrameric Ta4+ cation. In this case, only [Ta4CH2]+ reacts with CO2 to release a neutral “CH2O” unit, which is either formaldehyde, CO+H2, or a mixture thereof. Most likely the difference in the reactivity of the tetramer and the atomic cation is caused by the different structures of [Ta4CH2]+ (carbyne or carbide) compared to TaCH2+ (carbene). The corresponding DFT analysis demonstrates that the [Ta4CH2]+ ion taking part in the coupling reaction most likely features the carbyne hydride structure, i. e., HTa4CH+. While both, the carbyne hydride and the carbide dihydride, would show an exergonic conversion to the carbide oxide structure under exposure of CO2, the combination of a high desorption barrier of formaldehyde and a mandatory hydrogen diffusion step in case of H2 formation indicate that H2Ta4C+ is less likely to support the investigated reaction step than HTa4CH+.In summary, the tantalum‐mediated coupling reactions exhibit a more complex pattern than described previously.6a, 14+ is the only size of bare Ta clusters, which enables C−C coupling in consecutive reactions with further CH4 molecules.2+ and Ta3+, whose intensities were too low to be studied, may also exhibit a reaction scheme related to Ta4+ in the reaction of CH4 and CO2. A reason for this peculiar reactivity of the atomic cation may be that the lack of additional Ta atoms does not enable the carbon to bind to further metal atoms as it is the case in larger system such as Ta4+. This study clearly demonstrates that the reaction of methane and CO2 undergoes completely different pathway when going from single atoms to clusters. While single atoms support products from C−C coupling reactions, species with more Ta atoms instead may rather yield molecules from C−O bond formations.Besides of the structural differences of the methane dehydrogenation products, it must be noted that DFT results from our previous study suggest that Ta4 in a second reaction volume in the cluster source. The cations formed are then guided by electrostatic lenses and separated from neutrals by a quadrupole bender. A quadrupole mass filter enables the selection of particular cluster sizes prior to their eventual storage in a gas‐filled ring electrode ion trap. In the trap the ions are thermalized by collisions with the buffer gas (here: He) and exposed to the reactants (either CO2 or mixtures of CO2 and CH4). The tuning of the clusters’ storage time, which directly corresponds to the tuning of the reaction time, enables the elucidation of reaction kinetics. The qualitative and quantitative analysis of the charged species from the trap is performed with a reflectron time‐of‐flight mass spectrometer. Rate coefficients are obtained by modelling pseudo first‐order reaction kinetics of the experimental data with a home‐written computer program. (Further details are given in the Supporting Information.)Tantalum cations are created in a laser ablation cluster source. For investigations of methane dehydrogenation products, the clusters are additionally modified chemically by the exposure to CHThe authors declare no conflict of interest.1As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re‐organized for online delivery, but are not copy‐edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors.Supporting InformationClick here for additional data file.


Co‐registration to higher resolution 1H images allowed T1 and T2* relaxation times of deuterium in HDO in cerebrospinal fluid (CSF), gray matter (GM), and white matter (WM) to be estimated.2H concentrations measured during the eight‐hour loading were consistent with values estimated from cumulative D2O dose and body mass. Signal changes measured from three different regions of the brain during loading showed similar time‐courses. After summing over echoes, gradient echo brain images acquired in 7.5 minutes with a voxel volume of 0.36 ml showed an SNR of ˜16 in subjects loaded to 1.5%. T1‐values for deuterium in HDO were significantly shorter than corresponding values for 1H in H2O, while T2* values were similar. 2H relaxation times in CSF were significantly longer than in GM or WM.2H in brain during heavy water loading. 2H T1 and T2* relaxation times from water in GM, WM, and CSF are reported.Deuterium MR Measurements at 7T were used to track the increase in concentration of  However, the shorter longitudinal relaxation times of 2H allow faster signal averaging, partially compensating for the reduction in SNR associated with the reduced signal strength. The minimal equipment modifications required for implementing 2H imaging and the simplicity of the pulse sequences that can be used, mean that 2H imaging has significant potential for use in clinical applications. This has led to an increasing interest in the use of deuterium magnetic resonance in conjunction with injection or ingestion of 2H‐labeled compounds, as a means of monitoring cellular metabolism.The low natural abundance (˜0.015%) and gyromagnetic ratio (6.54 MHz/T) of deuterium  involves using 2H signals from metabolites. The signal from naturally abundant HDO can be used in calculating absolute concentrations of other metabolites. Therefore, knowledge of the relaxation times of HDO in different tissues is important for quantitative measurements. Previous measurements of HDO relaxation times in human participants have used non‐localized signalsDMI can provide spatially resolved measurements of metabolite concentrations and pathway fluxes,2H magnetic resonance allows direct, non‐invasive, measurement of the concentration of HDO, deuterated lipids, and other metabolic products of 2H labeled water and so could complement invasive measurements. The feasibility of imaging the distribution of HDO in the body following oral ingestion of D2O was demonstrated in animal experiments carried out in the 1980 s,Oral intake of heavy water is commonly used for assessment of body composition2O. The heavy water loading was carried out as part of a parallel study.Here, we implemented deuterium MRI at 7T and used it to characterize HDO signals from the human brain in four healthy participants who increased their deuterated water content to ˜1.5% for a six‐week period by drinking D22H‐imaging sub‐study which was approved by the local institutional ethics committee with the volunteers giving informed consent. Two participants were scanned during a set‐up phase in which we established the feasibility of 2H imaging and identified favorable imaging parameters. Here, we report data from four participants (A‐D) who were subsequently scanned using the optimized imaging protocols on a 7T Achieva scanner , operating at 45.8 MHz for 2H. A 26.4‐cm‐inner‐diameter, dual‐tuned 1H/2H birdcage coil  was used for deuterium measurements, while the standard, 32‐channel Rx/2‐channel Tx head coil  was used for acquiring anatomical 1H images.Six healthy participants took part in this 2O/30% H2O (one dose every ˜30 minutes), with the total amount of D2O consumed adjusted according to the participant's body weight to produce 1.5% enrichment. Participants subsequently drank ˜50 ml of D2O each morning over the six‐week study period to maintain 1.5% enrichment. Similar enrichment levels and durations have been used in recent studiesThe parallel study required an initial loading regime in which the targeted enrichment was built up in around eight hours. This involved the participants drinking between 12 and 16, ˜50 ml doses of 70% D1H scout scan for planning, followed by acquisition of 2H pulse‐acquire spectra from the whole head and from a 2‐cm‐thick axial slice positioned over the lateral ventricles. Both used the following scan parameters: flip angle α = 90°, 2048 samples, bandwidth (BW) = 3000 Hz, repetition time TR = 1 s an 64 averages . We then acquired axial, 3D MEGE 2H images . Axial 1H 3D GE images  were also acquired. This scanning protocol was repeated 17 days after the initial loading to provide comparative data at steady‐state enrichment. The spectroscopy measurements made before loading provided an estimate of the signal from naturally abundant deuterium in water: scaling subsequent measurements then allowed the absolute HDO concentration to be estimated at each time‐point. The HDO concentration in the body was also estimated from the ratio of the total imbibed D2O volume to an estimate of total body water.Two participants (A and B) were scanned during the initial eight‐hour loading period to monitor the time‐course of deuterated water concentration changes in the brain. A scanning protocol of ˜15 minutes duration was performed before dosing and after 30, 90, 150, 210, 270, 360, 420, and 540 minutes. The protocol comprised a 2H signal from different tissue compartments. The 2H images acquired at each time‐point were summed over the five echoes, and regions of interest (ROI) were then formed for a background region, general brain tissue, the lateral ventricles and for a region of high signal intensity thought to arise from blood vessels and CSF in the superior cistern. The SNR in images acquired before loading was too low to make good estimates of natural abundance signals, so values were normalized to the signal measured in the superior cistern ROI at the last time point of the initial loading period.We used the image data to track the changes in 2H relaxation times for water in CSF, GM, and WM were calculated from data acquired during the six‐week loading period using the dual‐tuned 2H/1H coil. In each session, we acquired 2H 3D sagittal MEGE images  at a range of TR values, along with 1H 3D MEGE images . 2H MEGE data from Participants A and B were acquired with five echoes , α = 60°, and TR = 68, 136, 272, 544 ms, with 8, 4, 2, and 1 averages, so that Tscan = 487 s per image. 2H MEGE data from participants C and D were acquired with six echoes  and one additional TR‐value . The number of TE and TR values were increased to improve fitting quality. The 2H scanning sessions were performed twice on Participants C and D.1H MPRAGE images (0.7 mm resolution) and 1H 3D MEGE images  from each participant in a separate scanning session using the Nova coil. These images were used for image segmentation and estimation of the 1H T2* values.We also acquired 2H relaxation rate constants R1 and R2*, we first estimated the variation of flip angle (α) over the image volume by summing the images across TEs, at each TR, and fitting the data voxel‐wise to a saturation recovery curve . The resulting flip‐angle maps were smoothed by averaging over 5 × 5 × 5 voxel neighborhood and the α‐values then used as fixed parameters in dual‐fitting the variation in signal intensity Si,j across TRi and TEj values for R1, R2* and signal amplitude, A. This involved minimisation of1H R2* maps were obtained by similar fitting to the exponential signal decay with TE in the 1H MEGE data acquired using the Nova coil.For calculation of maps of 1H MPRAGE data . After summing over echo times these images . The measured T1 and T2* values were consistently higher in GM than in WM, but the differences did not reach statistical significance . The relatively coarse resolution of the 2H images made it difficult to avoid the effects of partial voluming, particularly of CSF and GM, and the limited range of TE (4.3–46.3 ms) and TR (68–816 ms) values reduced the accuracy of measurement of the long T1 and T2* values in CSF, as is evident from the larger SDs of these measurements  and CSF (90 ms).Focusing on human brain measurements, De Feyter et al.2*‐weighting, with the CSF appearing hyperintense relative to gray and white matter, as is the case in T2*‐weighted 1H images. A notable difference between the 1H and 2H R2* maps  are only evident in the 2H images acquired with the shortest TE value (Figure 2* of HDO in muscle.The TE‐summed MEGE images in Figures e Figure  most lik2H spectra are in reasonably good agreement with the values calculated from the cumulative D2O dose and body mass (Figure 2*‐weighting and water fraction in the different brain regions. This implies that the dispersal kinetics following oral ingestion of D2O are rapid throughout the body on the timescale of the measurements. This is consistent with previous measurements based on blood sampling which indicate that the half‐life of absorption into blood is ˜12 minutes, with similar time constants for dispersal into other body water compartments.2H signals tracked the monotonically increasing dose and the values measured at maximum dose were similar to those measured 17 days later during the steady state loading period. Although both participants had approximately the same weight and target D2O dose, Participant B was only able to ingest 600 ml during the initial loading. The deuterium concentration measured from Participant A was consequently higher at the end of the loading period. The rest of participant B's loading was completed over the following 4 days, along with the daily 50 ml top‐up and similar concentrations were measured from the two participants in the steady state (Figure Figure s Figure . The sige Figure . The GCM2O loading was slowed. The rapid loading was required for the parallel study, but a more gradual increase in heavy water uptake could be used for future MR‐loading experiments to minimize these effects.Rapid increases in body water enrichment can lead to feelings of dizziness and nausea. These symptoms can occur at relatively low enrichments while equilibrium has not yet been achieved and are thought to result from temporary effects on the vestibular system due to density changes in the semi‐circular canals of the inner ear.52H in brain during heavy water loading to 100 times natural abundance, in four human participants. Gradient echo images with an SNR of 16 and a voxel volume of 0.36 ml could be acquired in 7.5 minutes. 2H T1 and T2* relaxation times from water in GM, WM, and CSF have also been measured at 7T. These relaxation times can be applied in research protocols using the natural abundance 2H signal from water for calibration. In future work we aim to track uptake from a single D2O dose on a shorter time scale, using faster, interleaved acquisition of 2H images and spectra.Deuterium MR measurements at 7T have been successfully used to track the increase in concentration of


Hypoxia, that is, an inadequate oxygen supply, is linked to neurodegeneration and patients with cardiovascular disease are prone to Alzheimer's disease (AD). 2‐Oxoglutarate and ferrous iron‐dependent oxygenases (2OGDD) play a key role in the regulation of oxygen homeostasis by acting as hypoxia sensors. 2OGDD also have roles in collagen biosynthesis, lipid metabolism, nucleic acid repair, and the regulation of transcription and translation. Many biological processes in which the >60 human 2OGDD are involved are altered in AD patient brains, raising the question as to whether 2OGDD are involved in the transition from normal aging to AD. Here we give an overview of human 2OGDD and critically discuss their potential roles in AD, highlighting possible relationships with synapse dysfunction/loss. 2OGDD may regulate neuronal/glial differentiation through enzyme activity‐dependent mechanisms and modulation of their activity has potential to protect against synapse loss. Work linking 2OGDD and AD is at an early stage, especially from a therapeutic perspective; we suggest integrated pathology and in vitro discovery research to explore their roles in AD is merited. We hope to help enable long‐term research on the roles of 2OGDD and, more generally, oxygen/hypoxia in AD. We also suggest shorter term empirically guided clinical studies concerning the exploration of 2OGDD/oxygen modulators to help maintain synaptic viability are of interest for AD treatment. The precise reasons for this are unclear but may reflect the many forms of dementia, lack of clear knowledge of factors affecting its progression, and knowledge that deterioration of brain function begins long before clinical diagnosis of dementia. The molecular basis of the neurobiology of dementia is not well understood. There is, however, evidence that massive loss of synapses in specific neural networks correlates with cognitive defects in dementia.1.22, dioxygen) to organs, tissues, and cells, is linked to neurodegeneration,Hypoxia, that is, the inadequate supply of atmospheric oxygen (O1Systematic Review: The authors reviewed the literature on human Fe (II) and 2‐oxoglutarate (2OG)‐dependent oxygenases (2OGDD) and their functions focusing on  links to Alzheimer's disease (AD), especially those that are synapse related. Future research directions and methods that can be applied to test the roles of 2OGDD in AD and their suitability as drug targets are proposed. Several 2OGDD that have shown potential to treat AD are highlighted.Interpretation: Our findings show the potential role of 2OGDD in synapse function, though research making direct causal links between 2OGDD malfunction and AD is presently lacking.Future Directions: We believe long term integrated pathology and in vitro discovery research on the roles of 2OGDD and shorter term empirically guided clinical studies concerning 2OGDD inhibitors and other brain oxygen availability modulators in AD treatment are necessary.VEGF) and erythropoietin (EPO), which are neuroprotective and have roles in neurogenesis and synapse protection.HIF target genes include vascular endothelial growth factor (e‐methyl‐lysine histone demethylases (KDMs).Other members of the structural subfamily of 2OGDD to which FIH (but not the PHDs) belongs, that is the Jumonji C (JmjC) 2OGDD, have been shown to be N1.3The complexity and context‐dependent natures of the roles of many 2OGDD, especially those involved in the regulation of transcription, such as the JmjC KDMs, means work to identify preferred targets among them for AD treatment is challenging. Presently, there is no direct evidence of role for 2OGDD in AD development in the manner that there is for them in some cancers .Pioneering work with prolyl hydroxylase inhibitors has identified mechanisms of inhibiting 2OGDD via 2OG competition/active site Fe(II) chelation; although other types of 2OGDD inhibition can be envisaged, developing brain penetrating versions of active site targeting inhibitors may be a good place to start such work on exploring the utility of 2OGDD inhibition outside of the hypoxic response in AD treatment. The recent approval of PHD inhibitors for treatment of anemia in chronic disease means that at least some of the human 2OGDD are therapeutically tractable and as far as is known safe targets. However, the current clinically approved PHD inhibitors are optimized for treatment of anemia in chronic kidney disease via upregulation of EPO production in the liver and kidneys. While these drugs might be of some value in treating the symptoms of AD, they are not optimized for brain penetration; in fact, this was likely minimized during their development. We therefore propose that development of brain penetrating PHD inhibitors, with and without additional activity versus FIH (which contributes to regulation of the set of HIF target genes), is pursued with a view to investigating their potential for AD treatment, via alteration of synaptic function in the hippocampus, either mediated via EPO upregulation or not.It should beBelow we give an overview of human 2OGDD and critically discuss their potential roles in AD, highlighting possibilities for future studies and clinical applications, with a particular emphasis on synapse dysfunction/loss associated with neurodegenerative disorders. We propose future research directions and methods that can be applied to test the roles of 2OGDD in AD and their suitability as drug targets. Our aims are twofold: first, we aim to promote and enable long‐term research on the roles of 2OGDD and, more generally, oxygen/hypoxia; second, we aim to encourage shorter term empirically guided clinical studies concerning 2OGDD inhibitors and other brain oxygen availability modulators in AD treatment.2N‐methyl demethylations, the latter proceeding via initial hydroxylation.2 into succinate and CO2.15 The activities of some 2OGDD are promoted by reducing agents, in particular catalysis by prolyl‐hydroxylases involved in collagen biosynthesis is promoted by vitamin C (L‐ascorbic acid), a deficiency of which causes the disease scurvy, which is associated with defective collagen (see below).In humans there are 60 to 70 2OGDD, the reported reactions of which comprise hydroxylations and related two electron oxidations and http://www.alzdata.org/], a high‐throughput collection of AD dataAnalysis of the expression profiles of 2OGDD in four brain regions, the entorhinal cortex (EC), the hippocampus (HPC), the temporal cortex (TC), and the frontal cortex (FC) suggests a link between 2OGDD and AD , the role of vascular pathology in the loss of synapses in cognitive impairment in AD has perhaps been overlooked. However, vascular dysfunction and damage have been identified as critical components of the pathophysiology of late‐life dementia including AD.Many reported studies on 2OGDD and AD are related to the HIFs, which are α, β‐heterodimeric transcription factors, the gene targets of which, including some 2OGDD,Over 20 human 2OGDD, in particular, but not exclusively, from the JmjC KDM and the TETs  2OGDD subfamilies participate in both the healthy regulation and disease‐associated changes in transcription.Below we describe the functions of specific human 2OGDD focusing on  links to AD, especially those that are related to synapse function; to guide the reader, we have summarized the domain organization and substrates of human 2OGDD in Tables 33.12OGDD use the tricarboxylic acid (TCA) intermediate 2OG and oxygen as cosubstrates and produce succinate, also a TCA intermediate, and carbon dioxide as coproducts. Recently, 2OG was observed to be significantly increased in plasma and CSF of AD patients.L‐ascorbic acid, is often added to promote 2OGDD catalysis in vitro. Ascorbate is a pivotal antioxidant that supports neuronal health and may play a role in slowing the progression of AD.L‐ascorbic acid in 2OGDD catalysis is lacking though there is indirect evidence that the activity of some 2OGDD (prolyl hydroxylases) involved in collagen biosynthesis is promoted by L‐ascorbic acid. Despite this incomplete knowledge, it is plausible that 2OGDD catalysis is limited by reducing agents’, including L‐ascorbic acid, availability in cells. AD patients are reported to be deficient in even ascorbate, despite adequate supplementation,A reducing agent, typically but not necessarily To date they have all been found to use Fe(II) as a cofactor and there is good evidence that the activity of some 2OGDD can be limited in cells by iron availability.3.2N‐ and the C‐terminal oxygen‐dependent degradation domains of HIF‐α subunits signals for proteasomal degradation of HIF‐α isoforms by promoting their binding to the von‐Hippel–Lindau (VHL) protein, which is the targeting component of a ubiquitin ligase complex.Both the levels and transcriptional activity of HIF are regulated by 2OGDD. PHD catalyzed prolyl‐hydroxylation in the EPO and VEGF genes, and of the role of the PHDs as hypoxia sensors for the HIF system.There are three human PHD isoforms ‐8‐hydroxyquinoline (M30) and 5‐[4‐propargylpiper‐azin‐1‐ylmethyl]‐8‐hydroxyquinoline (HLA20) are brain permeable, iron chelating drugs, which compete for Fe(II) with the PHDs, so increasing HIF‐α levels and inducing the transcription of HIF‐α regulated neuroprotective genes. These drugs have shown pro‐cognitive and anti‐inflammatory effects in a mouse model of AD.Early studies provide evidence that pursuing brain penetrating PHD inhibitors is of interest with respect to treating AD. 5‐, to various subtypes of neurons and glial cells.KDM4D has a role in hippocampal dentate gyrus (DG) neurogenesis, which drops sharply in AD patients.FBXL11 (KDM2A), JMJD1A/B (KDM3A/B), and JMJD2A/B (KDM4A/B) are substantially higher in post mortem prefrontal cortex tissue from patients with AD compared to controls, whereas FBXL10 (KDM2B) mRNA levels are downregulated in the AD patient brain.KDM3B and KDM5A show a trend of upregulation in AD in 12 datasets.KDM2, KDM3, KDM4A, or KDM4B genes in flies overexpressing tauR406W ameliorated tauR406W‐engendered eye defects, indicating JmjC KDMs have roles in neuronal function.KDM4A reduces heterochromatic loss in a tauR406W‐induced transgenic drosophila model;A study focusing on JmjC KDMs in tauopathies reports expression levels of The links among hypoxia, HIF, and JmjC KDMs are also of interest to AD, but are complex. It is reported that during AD progression, impaired Krebs cycle function and low‐level hypoxia alters the activity and expression of JmjC KDMs,3.3.2+ cells.JARID2 is a complex protein that has homology with JARID1s (KDM5s), as defined by the presence of conserved JmjC/JmjN and ARID domains. As yet, however, JARID2 has not been shown to have catalytic activity, but it is important in the regulation of transcription. The interaction of JARID2 with the polycomb repressive complex 2 (PRC2) confers transcriptional repression, at least in part, through production of H3K27me33.4In humans, the JmjC domain‐containing protein family contains ≈33 members, many with KDM activity (see above).——The catalytic activity of a JmjC domain enzyme was first demonstrated for FIH, which hydroxylates asparagines in HIF‐α isoforms and both asparagines and other residues in non‐HIF‐α susbtrates.3.4.1JMJD5 is likely essential in animals and is reported to have both KDM and, on the basis of detailed studies with peptides, arginine C‐3 hydroxylase activities.JMJD5 is proposed to have multiple roles including regulating osteoclast differentiation by destabilizing nuclear factor of activated T‐cells, cytoplasmic 1 (NFATC1),3.4.2S)‐lysyl hydroxylation of developmentally regulated GTP‐binding proteins 1 and 2 (DRG1/2), promoting their binding to RNA and so regulating translation .JMJD7 catalyzes ‐associated protein 1 (HSPBAP1) is a likely 2OGDD, the enzymatic activity of which is unknown, but which is reported to interact with the HSPB1 and so suppress the ability of the latter to protect cells from heat shock.3.53.5.1εN‐trimethyl‐lysine hydroxylase (TMLH) and γ‐butyrobetaine hydroixylase (GBBH) catalyze the C‐3 hydroxylation of εN‐trimethyl‐lysine and γ‐butyrobetaine, respectively.2OGDD play key roles in lipid metabolism in humans Table . CarnitiL‐carnitine and its acetylated derivative acetyl‐L‐carnitine (ALCAR) have therapeutic potential for neuroprotection.L‐carnitine availability, possibly in turn due to reduced BBOX1 and TMLHE activity. A meta‐analysis at the mRNA level found that BBOX1 was upregulated in AD across 12 datasets.Carnitine concentration is altered in AD brains,3.5.2Phytanoyl CoA hydroxylase plays a key role in the metabolism of phytanic acid, which is derived from the hydrophobic side chain of chlorophyll from the diet. After CoA‐esterification outside the peroxisome, phytanoyl CoA is transported into the peroxisome where it undergoes α‐oxidation due to the presence of a 3‐methyl‐group, which blocks the more normal β‐oxidation.Peroxisomal function declines with age and peroxisomal dysfunction in AD has been extensively reviewed.C‐terminal region of the dual‐specificity tyrosine‐phosphorylated and regulated kinase 1A (DYRK1A), an interaction that may induce relocalization of nuclear DYRK1A to the cytosol.The brain‐specific protein phytanoyl‐CoA‐hydroxylase associated protein 1 (PHYHIP), is reported to interact with PHYH via the 3.6Collagens are key components of the fibrillar and microfibrillar networks of the ECM and basement membranes.The C‐P3H subfamily consists of leucine proline‐enriched proteoglycan (leprecan) 1 (LEPRE1) and leprecan‐like 1/2 (LEPREL1/2), also known as prolyl 3‐hydroxylase 1/2/3 (P3H1/2/3). P3H1 catalyzes formation of 3‐hydroxyproline in Pro‐Gly‐rich sequences in collagens ; P3H2 catalyzes the post‐translational formation of 3‐hydroxyproline in ‐Gly‐Pro‐Hyp sequences where Hyp is 4‐hydroxyproline in collagens.P4HA1 is in the top 5% of genes associated with AD.P4HA2 is a HIF‐target gene in astrocytes.PLOD1 is in the top 5% of genes associated with AD.PLOD1 in whole blood from AD fast progressors compared to slow progressorsPLOD3 was significantly upregulated in AD across 12 datasets.PLOD1 and PLOD2 have been shown to be HIF targets,Meta‐analysis of four GWAS showed It is possible that the PLODs and C‐P4Hs have roles relating to hypoxia in AD. P4HA1 is reported to enhance the stability of HIF‐1α protein in breast cancer cells, possibly by reducing 2‐OG levels and/or increasing succinate production.3.7N‐alkylation; AlkB catalyzes demethylation via initial hydroxylation followed by fragmentation to give an aldehyde .Nucleobases/nucleic acids are a major class of oligomeric 2OGDD substrates.3.7.1N‐methyl mitochondrial nucleic acid demethylaseS‐adenosylmethionine‐dependent methyltransferase domain, which is required for the generation of 5‐methoxycarbonylmethyluridine (mcm5U) by methylation of 5‐carboxymethyluridine (cm5U), and a dioxygenase domain, which generates (S)‐5‐methoxycarbonylhydroxymethyluridine (mchm5U) by hydroxylation of mcm5U.Although further work is required, like bacterial AlkB, there is evidence that ALKBH2 and ALKBH3 repair alkylated DNA and RNA containing 1‐methyladenine (m1A) and 3‐methylcytosine (m3C) by oxidative demethylation.ALKBH3.Reverse transcription polymerase chain reaction (RT‐PCR) analyses have shown the intracellular domain of APP (AICD) strongly enhances the expression of N6‐methyladenine (m6A) in mRNA.ALKBH5 and ALKBH6 genes are significantly downregulated in incipient AD cases,ALKBH6 expression is downregulated in the Tg2576 mouse model of AD.ALKBH6 expression is related to AD; the potential association of ALKBH6 with AD thus merits further evaluation. ALKBH5 has been confirmed as a HIF‐1α target gene, that is, is induced by hypoxia, which is characteristic of AD development.The primary function of ALKBH5 appears to be demethylation of 3.7.2FTO AA‐genotype have an increased risk of AD, possibly through the interaction with apolipoprotein E ε4.FTO gene is regulated in AD via a leptin‐regulated pathway activated by factors such as a high midlife body mass index (BMI), which has an independent and direct effect on the central nervous system (CNS).FTO gene influences the risk of AD requires further investigation.Like ALKBH5, the primary function of FTO appears to be oxidation of m6A in mRNA, although FTO, the overexpression of which is closely linked to obesity and diabetes,Two recent papers reports come to opposing conclusions concerning protein expression of FTO in AD brains in model studies. Elevated levels of FTO were found in the brain of 3xTg‐AD mice, leading to inhibition of tuberous sclerosis complex 1 (TSC1) and an elevation in mTOR signaling, which is critical in AD pathology.3.7.3The TET subfamily, comprising TET1‐3, catalyzes sequential 5mC oxidation to generate 5hmC, 5fmC, and then 5caC in both DNA and RNAThe results of genome‐wide profiles of both 5mC and 5hmC in the human frontal cortex tissues from late‐onset Chinese AD patients and cognitively normal controls, suggest a role for 5hmC in AD pathogenesis.Levels of TET1, 5mC, and 5hmC are reported to be increased in AD brains, while levels of 5‐formylcytosine (5fmC) and 5‐carboxylcytosine (5caC) are decreased.TET3 is reported to be downregulated through activation of the IL‐6/JAK2/STAT3 pathway in the hippocampus of APP/PS1 mice.Chronic inflammation and Aβ accumulation are established features of AD.By contrast, a significant decrease in 5hmC and TET2 levels was observed in the hippocampus of aged 2×Tg‐AD mice;3.83.8.1The human epidermal growth factor aspartate/asparaginyl hydroxylase (EGFH) subfamily contains three members, that is ASPH, aspartate‐β‐hydroxylase domain‐containing protein 1 (ASPHD1), and aspartate‐β‐hydroxylase domain‐containing protein 2 (ASPHD2). ASPH catalyzes the C‐3 hydroxylation of aspartyl and asparaginyl residues in the epidermal growth factor‐like domains of proteins such as Notch and its homologs,Lawton et al. report evidence for cross‐talk among ASPH, HIF‐1α, and Notch in the regulation of neuronal motility, suggesting a possible role for ASPH in AD.3.8.2The 2OG and Fe(II)‐dependent oxygenase domain‐containing protein (OGFOD) subfamily contains three members, OGFOD1–3. OGFOD1 has been shown to catalyze hydroxylation of Pro‐62 of the small ribosomal subunit protein RPS23 and may have a role in the regulation of translation, though this has not been demonstrated in humans3.8.3P4HTM is highly expressed in the brain and, like the PHDs, there is evidence that it participates in O2‐dependent regulation of HIF‐α isoforms.P4HTM is one of the top 5% of genes associated with AD.Transmembrane prolyl 4‐hydroxylase (P4HTM) is a member of the prolyl 4‐hydroxylase (P4H) structural 2OGDD family and its sequence more closely resembles those of the C‐P4Hs than the PHDs.3.8.442.268 Human microarray data analysis shows that expression of PHYHD1 is substantially increased in human AD cortices, especially in the temporal cortices.phyhd1 expression was also observed in APPNL‐G‐F/NL‐G‐F mice, which are characterized by Aβ amyloidosis and neuroinflammation.phyhd1 expression in APPNL‐G‐F/NL‐G‐F mice.There are three known isoforms of PHYHD1, of which only PHYHD1A has been shown to be a functional 2OG oxygenase.PHYHD1 and unconventional myosin‐Vc (MYO5c) are associated with Braak NFT stage progression in human AD brains.PHYHD1 and MYO5c expression levels were found in patients with LOAD, indicating that they may be involved in the development of AD.Increased expression of PHYHD1, which is a highly expressed gene in human AD brains to cortical Aβ amyloidosis, NFT progression, and the neuroinflammatory response, possibly via the PHYHD1/POT1/MYO5C axis. Stimulation of naïve T cells resulted in upregulation of PHYHD1 after stimulation leading to differentiation into effector T cells.PHYHD1 is related to T cell infiltration in AD brains merits further exploration.Overall, PHYHD1 is a 2OGDD of particular interest to AD. There is good evidence linking The authors declare no competing financial interests. Author disclosures are available in the supporting information.SUPPORTING INFORMATIONClick here for additional data file.SUPPORTING INFORMATIONClick here for additional data file.SUPPORTING INFORMATIONClick here for additional data file.SUPPORTING INFORMATIONClick here for additional data file.


In Methods section “Transcutaneous immunizations” DI-TCI was replaced by DIVA, and finally typos were fixed in Figs 3 and 6. Those changes have now been updated in the HTML and PDF version of this Article.Figs. 3 and 6 are attached.