SHIP1 DELETION ENHANCES ROS PRODUCTION AND DECREASES SURVIVAL OF THE S. AUREUS INFECTED MICE

Reactive oxygen species (ROS) production by neutrophils is essential for host innate immune defense. However, although ROS production is advantageous for killing various infectious organisms, excessive ROS can cause tissue damage. Thus, ROS production by neutrophils must be tightly controlled.　In this study, we investigated a role for SH2 domain-containing inositol- 5-phosphatase 1 (SHIP1), a PtdIns(3,4,5)P3 phosphatase, in ROS production by neutrophils using ship1−/− mice. SHIP1 deletion enhanced ROS production as well as the bacterial killing capability of neutrophils. However, the ship1−/− mice showed decreases survival of the mice infected with Staphylococcus aureus (S. aureus). Our results suggest that SHIP1 controls appropriate host defenses against S. aureus infections in mice

Effects of Surface Defects on Photocatalytic H₂O₂ Production by Mesoporous Graphitic Carbon Nitride under Visible Light Irradiation

Photocatalytic production of hydrogen peroxide (H₂O₂) from ethanol (EtOH) and molecular oxygen (O₂) was carried out by visible light irradiation (λ > 420 nm) of mesoporous graphitic carbon nitride (GCN) catalysts with different surface areas prepared by silica-templated thermal polymerization of cyanamide. On these catalysts, the photoformed positive hole oxidize EtOH and the conduction band electrons localized at the 1,4-positions of the melem unit promote two-electron reduction of O₂ (H₂O₂ formation). The GCN catalysts with 56 and 160 m² g^–1 surface areas exhibit higher activity for H₂O₂ production than the catalyst prepared without silica template (surface area: 10 m² g^–1), but a further increase in the surface area (228 m² g^–1) decreases the activity. In addition, the selectivity for H₂O₂ formation significantly decreases with an increase in the surface area. The mesoporous GCN with larger surface areas inherently contain a larger number of primary amine moieties at the surface of mesopores. These defects behave as the active sites for four-electron reduction of O₂, thus decreasing the H₂O₂ selectivity. Furthermore, these defects also behave as the active sites for photocatalytic decomposition of the formed H₂O₂. Consequently, the GCN catalysts with relatively large surface area but with a small number of surface defects promote relatively efficient H₂O₂ formation

Graphitic Carbon Nitride Doped with Biphenyl Diimide: Efficient Photocatalyst for Hydrogen Peroxide Production from Water and Molecular Oxygen by Sunlight

Photocatalytic hydrogen peroxide (H₂O₂) production from water and molecular oxygen (O₂) by sunlight is a promising strategy for green, safe, and sustainable H₂O₂ synthesis. We prepared graphitic carbon nitride (g-C₃N₄) doped with electron-deficient biphenyl diimide (BDI) units by a simple calcination procedure. The g-C₃N₄/BDI catalyst, when photoirradiated by visible light (λ >420 nm) in pure water with O₂, successfully promotes water oxidation by the photogenerated valence band holes and selective two-electron reduction of O₂ by the conduction band electrons, resulting in successful production of millimolar levels of H₂O₂. Electrochemical analysis, Raman spectroscopy, and ab initio calculation results revealed that, upon photoexcitation of the catalyst, the photogenerated positive holes are localized on the BDI unit while the conduction band electrons are localized on the melem unit. This spatial charge separation suppresses rapid recombination of the hole–electron pairs and facilitates efficient H₂O₂ production. The solar-to-chemical energy conversion efficiency for H₂O₂ production is 0.13%, which is comparable to that for photosynthetic plants. This metal-free photocatalysis therefore shows potential as an artificial photosynthesis for clean solar fuel production

Mellitic Triimide-Doped Carbon Nitride as Sunlight-Driven Photocatalysts for Hydrogen Peroxide Production

Generating hydrogen peroxide (H₂O₂) from water and dioxygen (O₂) by photocatalysis is one ideal artificial photosynthesis for solar fuel production. Several early reported powdered photocatalysts, however, produce small amounts of H₂O₂ (<0.1 mM). We prepared graphitic carbon nitride (g-C₃N₄) doped with mellitic triimide (MTI) units by thermal condensation of melem and mellitic acid anhydride. The g-C₃N₄/MTI photocatalyst, when irradiated by visible light (λ > 420 nm) in pure water with O₂, successfully produces millimolar levels of H₂O₂ via water oxidation by valence band holes and selective two-electron reduction of O₂ by conduction band electrons. The incorporation of triply branched MTI units creates a condensed melem layer. This facilitates efficient intra- and interlayer transfer of photogenerated charge carriers and shows high electrical conductivity. The solar-to-chemical conversion efficiency for H₂O₂ production on the catalyst is 0.18%, which is higher than that of natural photosynthesis (∼0.1%) and similar to the highest values obtained by semiconductor water-splitting catalysts

Carbon Nitride–Aromatic Diimide–Graphene Nanohybrids: Metal-Free Photocatalysts for Solar-to-Hydrogen Peroxide Energy Conversion with 0.2% Efficiency

Solar-to-chemical energy conversion is a challenging subject for renewable energy storage. In the past 40 years, overall water splitting into H₂ and O₂ by semiconductor photocatalysis has been studied extensively; however, they need noble metals and extreme care to avoid explosion of the mixed gases. Here we report that generating hydrogen peroxide (H₂O₂) from water and O₂ by organic semiconductor photocatalysts could provide a new basis for clean energy storage without metal and explosion risk. We found that carbon nitride–aromatic diimide–graphene nanohybrids prepared by simple hydrothermal–calcination procedure produce H₂O₂ from pure water and O₂ under visible light (λ > 420 nm). Photoexcitation of the semiconducting carbon nitride–aromatic diimide moiety transfers their conduction band electrons to graphene and enhances charge separation. The valence band holes on the semiconducting moiety oxidize water, while the electrons on the graphene moiety promote selective two-electron reduction of O₂. This metal-free system produces H₂O₂ with solar-to-chemical energy conversion efficiency 0.20%, comparable to the highest levels achieved by powdered water-splitting photocatalysts

Rapamycin-sensitive mechanisms confine the growth of fission yeast below the temperatures detrimental to cell physiology

Summary: Cells cease to proliferate above their growth-permissible temperatures, a ubiquitous phenomenon generally attributed to heat damage to cellular macromolecules. We here report that, in the presence of rapamycin, a potent inhibitor of Target of Rapamycin Complex 1 (TORC1), the fission yeast Schizosaccharomyces pombe can proliferate at high temperatures that usually arrest its growth. Consistently, mutations to the TORC1 subunit RAPTOR/Mip1 and the TORC1 substrate Sck1 significantly improve cellular heat resistance, suggesting that TORC1 restricts fission yeast growth at high temperatures. Aiming for a more comprehensive understanding of the negative regulation of high-temperature growth, we conducted genome-wide screens, which identified additional factors that suppress cell proliferation at high temperatures. Among them is Mks1, which is phosphorylated in a TORC1-dependent manner, forms a complex with the 14-3-3 protein Rad24, and suppresses the high-temperature growth independently of Sck1. Our study has uncovered unexpected mechanisms of growth restraint even below the temperatures deleterious to cell physiology

Rapamycin-sensitive mechanisms confine the growth of fission yeast below the temperatures detrimental to cell physiology

Cells cease to proliferate above their growth-permissible temperatures, a ubiquitous phenomenon generally attributed to heat damage to cellular macromolecules. We here report that, in the presence of rapamycin, a potent inhibitor of Target of Rapamycin Complex 1 (TORC1), the fission yeast Schizosaccharomyces pombe can proliferate at high temperatures that usually arrest its growth. Consistently, mutations to the TORC1 subunit RAPTOR/Mip1 and the TORC1 substrate Sck1 significantly improve cellular heat resistance, suggesting that TORC1 restricts fission yeast growth at high temperatures. Aiming for a more comprehensive understanding of the negative regulation of high-temperature growth, we conducted genome-wide screens, which identified additional factors that suppress cell proliferation at high temperatures. Among them is Mks1, which is phosphorylated in a TORC1-dependent manner, forms a complex with the 14-3-3 protein Rad24, and suppresses the high-temperature growth independently of Sck1. Our study has uncovered unexpected mechanisms of growth restraint even below the temperatures deleterious to cell physiology

Nitrogen Fixation with Water on Carbon-Nitride-Based Metal-Free Photocatalysts with 0.1% Solar-to-Ammonia Energy Conversion Efficiency

Ammonia (NH₃), which is an indispensable chemical, is produced by the Haber–Bosch process using H₂ and N₂ under severe reaction conditions. Although photocatalytic N₂ fixation with water under ambient conditions is ideal, all previously reported catalysts show low efficiency. Here, we report that a metal-free organic semiconductor could provide a new basis for photocatalytic N₂ fixation. We show that phosphorus-doped carbon nitride containing surface nitrogen vacancies (PCN-V), prepared by simple thermal condensation of the precursors under H₂, produces NH₃ from N₂ with water under visible light irradiation. The doped P atoms promote water oxidation by the photoformed valence-band holes, and the N vacancies promote N₂ reduction by the conduction-band electrons. These phenomena facilitate efficient N₂ fixation with a solar-to-chemical conversion (SCC) efficiency of 0.1%, which is comparable to the average solar-to-biomass conversion efficiency of natural photosynthesis by typical plants. Thus, this metal-free catalyst shows considerable potential as a new method of artificial photosynthesis