Efficient, earth‐abundant, and acid‐stable catalysts for the oxygen evolution reaction (OER) are missing pieces for the production of hydrogen via water electrolysis. Here, we report how the ...limitations on the stability of 3d‐metal materials can be overcome by the spectroscopic identification of stable potential windows in which the OER can be catalyzed efficiently while simultaneously suppressing deactivation pathways. We demonstrate the benefits of this approach using gamma manganese oxide (γ‐MnO2), which shows no signs of deactivation even after 8000 h of electrolysis at a pH of 2. This stability is vastly superior to existing acid‐stable 3d‐metal OER catalysts, but cannot be realized if there is a deviation as small as 50‐mV from the stable potential window. A stable voltage efficiency of over 70 % in a polymer–electrolyte membrane (PEM) electrolyzer further verifies the availability of this approach and showcases how materials previously perceived to be unstable may have potential application for water electrolysis in an acidic environment.
Window of opportunity: Spectroscopic measurements allowed the identification of a stable potential window in which γ‐MnO2 is able to catalyze the oxygen evolution reaction under acidic conditions for more than 8000 hours. This shows how the limitations on the stability of 3d‐metal materials acting as electrocatalysts can be overcome.
Manganese oxides have been extensively investigated as model systems for the oxygen-evolving complex of photosystem II. However, most bioinspired catalysts are inefficient at neutral pH and ...functional similarity to the oxygen-evolving complex has been rarely achieved with manganese. Here we report the regulation of proton-coupled electron transfer involved in water oxidation by manganese oxides. Pyridine and its derivatives, which have pKa values intermediate to the water ligand bound to manganese(II) and manganese(III), are used as proton-coupled electron transfer induction reagents. The induction of concerted proton-coupled electron transfer is demonstrated by the detection of deuterium kinetic isotope effects and compliance of the reactions with the libido rule. Although proton-coupled electron transfer regulation is essential for the facial redox change of manganese in photosystem II, most manganese oxides impair these regulatory mechanisms. Thus, the present findings may provide a new design rationale for functional analogues of the oxygen-evolving complex for efficient water splitting at neutral pH.
By rationally designing superhydrophobic electrodes with different underwater wetting states, it is revealed that only the underwater Wenzel‐Cassie coexistent state shows the clearly enhanced ability ...in catalyzing the oxygen reduction reaction, a typical underwater gas‐consuming reaction at electrode. It is proposed that the maximizing and stabilizing the liquid/gas/solid triphase interface, endowed by the underwater Wenzel‐Cassie coexistent state, plays a rather crucial role.
Inflammation is involved in the induction of chronic inflammatory and neuropathic pain. Moreover, the ketogenic diet, a high-fat, low-carbohydrate, and adequate protein diet, has an anti-inflammatory ...effect. Thus, we hypothesized that a ketogenic diet has a therapeutic effect on both types of chronic pain. In the present study, we investigated the effect of a ketogenic diet on mechanical allodynia, a chronic pain symptom, in formalin-induced chronic inflammatory pain and nerve injury-induced neuropathic pain models using adult male mice. Formalin injection into the hind paw induced mechanical allodynia in both the injected and intact hind paws, and the ketogenic diet alleviated mechanical allodynia in both hind paws. In addition, the ketogenic diet prevented formalin-induced edema. Furthermore, the diet alleviated mechanical allodynia induced by peripheral nerve injury. Thus, these findings indicate that a ketogenic diet has a therapeutic effect on chronic pain induced by inflammation and nerve injury.
DNA methylation of cytosine bases is a major epigenetic modification that regulates gene expression and vertebrate development. The ten-eleven translocation (TET) enzymes oxidize 5-methylcytosine ...(5mC) to 5-hydroxymethylcytosine (5hmC), and active DNA demethylation influences gene expression specific to each developmental stage, although recent reports have shown that TET also has a non-catalytic function. In fetal mice, the epithelium in the submandibular gland (SMG) buds as a derivative of the oral cavity at embryonic day 11 (E11) and, by E15, it begins to differentiate into the salivary epithelium, which expresses water-channel aquaporin 5 (AQP5). The functional differentiation of the SMG epithelium can be regulated epigenetically, but how TET enzymes contribute is largely unknown. Here, we used several techniques, including hydroxymethylated DNA immunoprecipitation qPCR and histological analysis, to examine the changes in 5hmC levels and AQP5 and TET expression during SMG development. We found that 5hmC levels and AQP5 expression increased in the E15 SMG epithelium, while TET2 expression in the terminal buds decreased at E15. In agreement with the in vivo observations, Tet2 inhibition ex vivo led to the upregulation of AQP5 expression in terminal buds of the SMG epithelium. These results suggest that the downregulation of TET2 expression at E15 is a critical epigenetic event that establishes the epithelial fate for functional SMGs during development.
•AQP5 expression is regulated epigenetically during differentiation.•5-hydroxymethylcytosine (5hmC) levels increase at E15 in SMG epithelium.•Ten-eleven translocation-2 (TET2) expression in terminal buds decreases at E15.•TET2 inhibition induces functional differentiation in SMG epithelium.
Epithelial-mesenchymal interactions are required to coordinate cell proliferation, patterning, and functional differentiation of multiple cell types in a developing organ. This exquisite coordination ...is dependent on various secreted molecules that provide developmental signals to mediate these tissue interactions. Recently, it was reported that mature mesenchymal-derived microRNAs (miRNAs) in the fetal mouse salivary gland are loaded into exosomes, and transported to the epithelium where they influence progenitor cell proliferation. The exosomal miRNAs regulated epithelial expression of genes involved in DNA methylation in progenitor cells to influence morphogenesis. Thus, exosomal miRNAs are mobile genetic signals that cross tissue boundaries within an organ. These findings raise many questions about how miRNA signals are initiated to coordinate organogenesis and whether they are master regulators of epithelial-mesenchymal interactions. The development of therapeutic applications using exosomal miRNAs for the regeneration of damaged adult organs is a promising area of research.
The development of active water oxidation catalysts is critical to achieve high efficiency in overall water splitting. Recently, sub-10 nm-sized monodispersed partially oxidized manganese oxide ...nanoparticles were shown to exhibit not only superior catalytic performance for oxygen evolution, but also unique electrokinetics, as compared to their bulk counterparts. In the present work, the water-oxidizing mechanism of partially oxidized MnO nanoparticles was investigated using integrated in situ spectroscopic and electrokinetic analyses. We successfully demonstrated that, in contrast to previously reported manganese (Mn)-based catalysts, Mn(III) species are stably generated on the surface of MnO nanoparticles via a proton-coupled electron transfer pathway. Furthermore, we confirmed as to MnO nanoparticles that the one-electron oxidation step from Mn(II) to Mn(III) is no longer the rate-determining step for water oxidation and that Mn(IV)O species are generated as reaction intermediates during catalysis.
Epithelial-mesenchymal interactions involve fundamental communication between tissues during organogenesis and are primarily regulated by growth factors and extracellular matrix. It is unclear ...whether RNA-containing exosomes are mobile genetic signals regulating epithelial-mesenchymal interactions. Here we identify that exosomes loaded with mesenchyme-specific mature microRNA contribute mobile genetic signals from mesenchyme to epithelium. The mature mesenchymal miR-133b-3p, loaded into exosomes, was transported from mesenchyme to the salivary epithelium, which did not express primary miR-133b-3p. Knockdown of miR-133b-3p in culture decreased endbud morphogenesis, reduced proliferation of epithelial KIT+ progenitors, and increased expression of a target gene, Disco-interacting protein 2 homolog B (Dip2b). DIP2B, which is involved in DNA methylation, was localized with 5-methylcytosine in the prophase nucleus of a subset of KIT+ progenitors during mitosis. In summary, exosomal transport of miR-133b-3p from mesenchyme to epithelium decreases DIP2B, which may function as an epigenetic regulator of genes responsible for KIT+ progenitor expansion during organogenesis.
Display omitted
•Exosomal miRNAs are transported from mesenchyme to epithelium during organogenesis•Exosomal mesenchymal miR-133b-3p is delivered to the epithelium but not transcribed•miR-133b-3p targets DIP2B, which is involved in DNA methylation in KIT+ progenitors•Exosomal miRNA epigenetically regulates genes controlling KIT+ progenitor expansion
Epithelial-mesenchymal interactions are critical for salivary gland development. Hayashi et al. show that miRNA-containing exosomes produced by mesenchyme are transported to the epithelium, where they regulate KIT+ progenitor cell proliferation. A specific mesenchymal miRNA (miR-133b-3p) targets DIP2B, which is involved in DNA methylation, thus regulating progenitor cell expansion during organogenesis.
PDF
