Explore the vast range of titles available.

As widely used peroxidase-like nanozymes, Fe-based nanozymes still suffer from an unclear reaction mechanism, which limits their further application. In this work, through alkaline treatment and then the replacement or occupation of strong acid sites by isolated Fe species, porous ZSM-5-confined atomic Fe species nanozymes with separated medium acid sites (Al-OH) and isolated Fe-O[sub.4] sites were prepared. And the structure and the state of Fe-O[sub.4] confined by ZSM-5 were determined by AC-HAADF-STEM, XPS, and XAS. In the oxidation of 3, 3′, 5, 5′-tetramethylbenzidine (TMB) by the hydrogen peroxide (H[sub.2]O[sub.2]) process, the heterolysis of H[sub.2]O[sub.2] to ∙OH mainly occurs at the isolated Fe-O[sub.4] sites, and then the generated ∙OH can spill over to the Al-OH sites to oxidize the adsorbed TMB. The synergistic effect between Fe-O[sub.4] sites and medium acid sites can significantly benefit the catalytic performance of Fe-based nanozymes.

Peroxodisulfate (PDS), peroxymonosulfate (PMS), and hydrogen peroxide (H[sub.2]O[sub.2]) might coexist in a persulfate system. It leads to the mutual interference in concentration determination due to their similar structures. Simultaneous detection of the three peroxides involves limited reporting. Herein, a multi-step iodometry was established to simultaneously determine the concentrations of PDS, PMS, and H[sub.2]O[sub.2] coexisting in a solution. Firstly, molybdate–NaHCO[sub.3]-buffered iodometry was proposed to uplift the overall detection of peroxides since the recovery rate of H[sub.2]O[sub.2] was unexpectedly lower in the peroxide mixture than in the single H[sub.2]O[sub.2] solution with reported NaHCO[sub.3]-buffered iodometry. Then, multi-step iodometry was proposed based on the established molybdate–NaHCO[sub.3]-buffered iodometry using the combination with catalase and revised acetate-buffered iodometry (pH 3). The multi-step iodometry determined the coexisting PMS, PDS, and H[sub.2]O[sub.2] with the recovery rate of 95–105% and a standard deviation of ≤7% of two replicates at the individual centration of 13–500 μmol∙L[sup.−1]. The recovery rates of peroxides were within 95–105% at pH 3–11 and within 90–110% in the presence of Cl[sup.−] (0–150 mg∙L[sup.−1]), F[sup.−] (0–1.5 mg∙L[sup.−1]), SO[sub.4] [sup.2−] (0–150 mg∙L[sup.−1]), or NO[sub.3] [sup.−] (0–20 mg∙L[sup.−1]). The recovery rate of H[sub.2]O[sub.2] was lowered down to 91% or 87% in the sample containing 100 mg/L Ca[sup.2+] or Mg[sup.2+], respectively, but was lifted up to 100% or 93% once pretreated by adding 0.11–1.06 g∙L[sup.−1] Na[sub.2]CO[sub.3]. In the background of tap water, surface water, and ground water, peroxides were all detected in 90–110%, which indicates the applicability of multi-step iodometry in real waters.

Developing high-efficiency photoelectrodes plays an important role in the photoelectrocatalytic generation of hydrogen peroxide (H[sub.2]O[sub.2]) in the photoelectrochemical (PEC) water splitting field. In this work, an innovative strategy was proposed, the synergistic photocatalytic production of H[sub.2]O[sub.2] using a bidirectional photoanode–photocathode coupling system under visible-light irradiation. Fe[sub.2]O[sub.3]-Ti, as the photoanode, which was built by way of Fe[sub.2]O[sub.3] loaded on Ti-mesh using the hydrothermal-calcination method, was investigated in terms of the suitability of its properties for PEC H[sub.2]O[sub.2] production after optimization of the bias voltage, the type of electrolyte solution, and the concentration of the electrolyte. Afterwards, a H-type double-electrode coupling system with an Fe[sub.2]O[sub.3]-Ti photoanode and a WO[sub.3]@Co[sub.2]SnO[sub.4] photocathode was established for the bidirectional synergistic production of H[sub.2]O[sub.2] under visible-light irradiation. The yield of H[sub.2]O[sub.2] reached 919.56 μmol·L[sup.−1]·h[sup.−1] in 2 h over −0.7 V with 1 mol·L[sup.−1] of KHCO[sub.3] as the anolyte and 0.1 mol·L[sup.−1] Na[sub.2]SO[sub.4] as the catholyte (pH = 3). It was inferred that H[sub.2]O[sub.2] production on the WO[sub.3]@Co[sub.2]SnO[sub.4] photocathode was in line with the 2e[sup.-] oxygen reduction reaction (ORR) principle, and on the Fe[sub.2]O[sub.3]-Ti photoanode was in line with the 2e[sup.-] water oxidation reaction (WOR) rule, or it was indirectly promoted by the electrolyte solution KHCO[sub.3]. This work provides an innovative idea and a reference for anode–cathode double coupling systems for the bidirectional production of H[sub.2]O[sub.2].

Ozonide OZ439 is a synthetic peroxide antimalarial drug candidate designed to provide a single-dose oral cure in humans. OZ439 has successfully completed Phase I clinical trials, where it was shown to be safe at doses up to 1,600 mg and is currently undergoing Phase lia trials in malaria patients. Herein, we describe the discovery of OZ439 and the exceptional antimalarial and pharmacokinetic properties that led to its selection as a clinical drug development candidate. In vitro, OZ439 is fast-acting against all asexual erythrocytic Plasmodium falciparum stages with IC₄₀ values comparable to those for the clinically used artemisinin derivatives. Unlike all other synthetic peroxides and semisynthetic artemisinin derivatives, OZ439 completely cures Plasmodium berghe/-infected mice with a single oral dose of 20 mg/kg and exhibits prophylactic activity superior to that of the benchmark chemoprophylactic agent, mefloquine. Compared with other peroxide-containing antimalarial agents, such as the artemisinin derivatives and the first-generation ozonide OZ277, OZ439 exhibits a substantial increase in the pharmacokinetic half-life and blood concentration versus time profile in three preclinical species. The outstanding efficacy and prolonged blood concentrations of OZ439 are the result of a design strategy that stabilizes the intrinsically unstable pharmacophoric peroxide bond, thereby reducing clearance yet maintaining the necessary Fe (ll)-reactivity to elicit parasite death.

Astaxanthin (AST) is a carotenoid that has positive effects on various organs and tissues. It also exhibits a cardioprotective action. In this study, the influence of AST on the survival of H9c2 cardiomyocytes under hydrogen peroxide (H[sub.2]O[sub.2])- and doxorubicin (DOX)-induced cardiotoxicity was investigated. Under these conditions, the content of cytosolic Ca[sup.2+] was measured, and changes in the area of the mitochondrial mass, as well as in the content of the voltage-dependent anion channel 1 (VDAC1), the autophagy marker LC3A/B, and the pro-apoptotic transcription factor homologous protein (CHOP), were determined. It was found that AST removed the cytotoxic effect of H[sub.2]O[sub.2] and DOX, while cell survival increased, and the mitochondrial mass did not differ from the control. At the same time, a decrease in the content of cytosolic Ca[sup.2+] and the restoration of the VDAC1 level to values close to the control were observed. The restoration of the CHOP level suggests a reduction in endoplasmic reticulum (ER) stress in cells. The results allow us to consider AST as a potential agent in the prevention and/or treatment of cardiac diseases associated with oxidative stress.

Necroptosis and ferroptosis are two distinct necrotic cell death modalities with no known common molecular mechanisms. Necroptosis is activated by ligands of death receptors such as tumor necrosis factor-α (TNF-α) under caspase-deficient conditions, whereas ferroptosis is mediated by the accumulation of lipid peroxides upon the depletion/or inhibition of glutathione peroxidase 4 (GPX4). The molecular mechanism that mediates the execution of ferroptosis remains unclear. In this study, we identified 2-amino-5-chloro-N,3-dimethylbenzamide (CDDO), a compound known to inhibit heat shock protein 90 (HSP90), as an inhibitor of necroptosis that could also inhibit ferroptosis. We found that HSP90 defined a common regulatory nodal between necroptosis and ferroptosis. We showed that inhibition of HSP90 by CDDO blocked necroptosis by inhibiting the activation of RIPK1 kinase. Furthermore, we showed that the activation of ferroptosis by erastin increased the levels of lysosome-associated membrane protein 2a to promote chaperone-mediated autophagy (CMA), which, in turn, promoted the degradation of GPX4. Importantly, inhibition of CMA stabilized GPX4 and reduced ferroptosis. Our results suggest that activation of CMA is involved in the execution of ferroptosis.

Hydrogen peroxide (H₂O₂) is produced, via superoxide and superoxide dismutase, by electron transport in chloroplasts and mitochondria, plasma membrane NADPH oxidases, peroxisomal oxidases, type III peroxidases and other apoplastic oxidases. Intracellular transport is facilitated by aquaporins and H₂O₂ is removed by catalase, peroxiredoxin, glutathione peroxidase-like enzymes and ascorbate peroxidase, all of which have cell compartment-specific isoforms. Apoplastic H₂O₂ influences cell expansion, development and defence by its involvement in type III peroxidase-mediated polymer cross-linking, lignification and, possibly, cell expansion via H₂O₂-derived hydroxyl radicals. Excess H₂O₂ triggers chloroplast and peroxisome autophagy and programmed cell death. The role of H₂O₂ in signalling, for example during acclimation to stress and pathogen defence, has received much attention, but the signal transduction mechanisms are poorly defined. H₂O₂ oxidizes specific cysteine residues of target proteins to the sulfenic acid form and, similar to other organisms, this modification could initiate thiol-based redox relays and modify target enzymes, receptor kinases and transcription factors. Quantification of the sources and sinks of H₂O₂ is being improved by the spatial and temporal resolution of genetically encoded H₂O₂ sensors, such as HyPer and roGFP2-Orp1. These H₂O₂ sensors, combined with the detection of specific proteins modified by H₂O₂, will allow a deeper understanding of its signalling roles.

Background Salinity-alkalinity stress is one of the major abiotic stresses affecting plant growth and development. γ-Aminobutyrate (GABA) is a non-protein amino acid that functions in stress tolerance. However, the interactions between cellular redox signaling and chlorophyll (Chl) metabolism involved in GABA-induced salinity-alkalinity stress tolerance in plants remains largely unknown. Here, we investigated the role of GABA in perceiving and regulating chlorophyll biosynthesis and oxidative stress induced by salinity-alkalinity stress in muskmelon leaves. We also evaluated the effects of hydrogen peroxide (H 2 O 2 ), glutathione (GSH), and ascorbate (AsA) on GABA-induced salinity-alkalinity stress tolerance. Results Salinity-alkalinity stress increased malondialdehyde (MDA) content, relative electrical conductivity (REC), and the activities of superoxide dismutase (SOD), ascorbate peroxidase (APX) and dehydroascorbate reductase (DHAR). Salinity-alkalinity stress decreased shoot dry and fresh weight and leaf area, reduced glutathione and ascorbate (GSH and AsA) contents, activities of glutathione reductase (GR) and monodehydroascorbate reductase (MDAR). By contrast, pretreatment with GABA, H 2 O 2 , GSH, or AsA significantly inhibited these salinity-alkalinity stress-induced effects. The ability of GABA to relieve salinity-alkalinity stress was significantly reduced when the production of endogenous H 2 O 2 was inhibited, but was not affected by inhibiting endogenous AsA and GSH production. Exogenous GABA induced respiratory burst oxidase homologue D ( RBOHD ) genes expression and H 2 O 2 accumulation under normal conditions but reduced the H 2 O 2 content under salinity-alkalinity stress. Salinity-alkalinity stress increased the accumulation of the chlorophyll synthesis precursors glutamate (Glu), δ-aminolevulinic acid (ALA), porphobilinogen (PBG), uroporphyrinogen III (URO III), Mg-protoporphyrin IX (Mg-proto IX), protoporphyrin IX (Proto IX), protochlorophyll (Pchl), thereby increasing the Chl content. Under salinity-alkalinity stress, exogenous GABA increased ALA content, but reduced the contents of Glu, PBG, URO III, Mg-proto IX, Proto IX, Pchl, and Chl. However, salinity-alkalinity stress or GABA treated plant genes expression involved in Chl synthesis had no consistent trends with Chl precursor contents. Conclusions Exogenous GABA elevated H 2 O 2 may act as a signal molecule, while AsA and GSH function as antioxidants, in GABA-induced salinity-alkalinity tolerance. These factors maintain membrane integrity which was essential for the ordered chlorophyll biosynthesis. Pretreatment with exogenous GABA mitigated salinity-alkalinity stress caused excessive accumulation of Chl and its precursors, to avoid photooxidation injury.

Five representatives of a novel type of di(hydroperoxy)alkane adducts of phosphine oxides have been synthesized and fully characterized, including their solubility in organic solvents. The phosphine oxide Cy[sub.3]PO (1) has been used in combination with the corresponding aldehydes to create the adducts Cy[sub.3]PO·(HOO)[sub.2]CHCH[sub.3] (2), Cy[sub.3]PO·(HOO)[sub.2]CHCH[sub.2]CH[sub.3] (3), Cy[sub.3]PO·(HOO)[sub.2]CH(CH[sub.2])[sub.2]CH[sub.3] (4), Cy[sub.3]PO·(HOO)[sub.2]CH(CH[sub.2])[sub.3]CH[sub.3] (5), and Cy[sub.3]PO·(HOO)[sub.2]CH(CH[sub.2])[sub.7]CH[sub.3] (6). All adducts crystallize easily and contain the peroxide and phosphine oxide hydrogen-bonded in 1:1 ratios. The single crystal X-ray structures of 2–6 and their unique features are discussed. The [sup.31]P NMR spectra of the adducts 2–6 show downfield-shifted signals as compared to Cy[sub.3]PO. In the IR spectra, the ν(P=O) wavenumbers of the adducts have smaller values than the neat phosphine oxide. All spectroscopic results of 2–6 show that the P=O bond is weakened by hydrogen-bonding to the di(hydroperoxy)alkane moieties. Adduct 6 selectively oxidizes PPh[sub.3] to OPPh[sub.3] within minutes, and nonanal is reformed in the process. The easy synthesis, handling, and administration of these stable, solid, and soluble peroxides with well-defined composition will have a positive impact on synthetic chemistry.