Formaldehyde activation factor, tetrahydromethanopterin, a coenzyme of methanogenesis

An oxygen-labile formaldehyde activation factor (FAF) was isolated in highly purified form by use of anoxic fractionation procedures. The molecular weight of FAF was determined to be 776 and that of methanopterin (MPT) 772 by fast-atom-bombardment mass spectrometry (FABMS). High-resolution FABMS measurements on MPT and FAF indicated molecular formulas of C₃₀H₄₁N₆O₁₆P and C₃₀H₄₅N₆O₁₆P, respectively. The presence of phosphorus was confirmed by 100-MHz ³¹P NMR. The 360-MHz ¹H NMR spectrum of FAF in deuterium oxide was similar to that of MPT. A functional relationship between MPT and FAF was documented; both compounds stimulated the reductive demethylation of 2-(methylthio)ethanesulfonic acid (CH₃-S-CoM) to CH₄ when formaldehyde oxidation provided a source of electrons, and FAF replaced MPT in the CH₃-S-CoM-stimulated conversion of CO₂ to CH₄ under H₂ (the RPG effect). MPT was enzymically converted to FAF during the reduction of CH₃-S-CoM, and HCHO to CH₄ under H₂. Evidence indicates that FAF is tetrahydromethanopterin.     

Inspecting Insulin Products Using Water Proton NMR. I. Noninvasive vs Invasive Inspection

Background:There is a clear need to transition from batch-level to vial/syringe/pen-level quality control of biologic drugs, such as insulin. This could be achieved only by noninvasive and quantitative inspection technologies that maintain the integrity of the drug product.Methods:Four insulin products for patient self-injection presented as prefilled pens have been noninvasively and quantitatively inspected using the water proton NMR technology. The inspection output is the water proton relaxation rate R₂(¹H₂O), a continuous numerical variable rather than binary pass/fail.Results:Ten pens of each product were inspected. R₂(¹H₂O) displays insignificant variation among the 10 pens of each product, suggesting good insulin content uniformity in the inspected pens. It is also shown that transferring the insulin solution out of and then back into the insulin pen caused significant change in R₂(¹H₂O), presumably due to exposure to O₂ in air.Conclusions:Water proton NMR can noninvasively and quantitatively inspect insulin pens. wNMR can confirm product content uniformity, but not absolute content. Its sensitivity to sample transferring provides a way to detect drug product tampering. This opens the possibility of inspecting every pen/vial/syringe by manufacturers and end-users.     

Synthesis,Structure and Thermal Behavior of Oxalato-Bridged Rb+ and H3O+ Extended Frameworks with Different Dimensionalities

Correlative studies of three oxalato-bridged polymers, obtained under hydrothermal conditions for the two isostructural compounds {Rb(HC₂O₄)(H₂C₂O₄)(H₂O)₂}_∞¹, 1, {H₃O(HC₂O₄)(H₂C₂O₄).2H₂O}_∞¹, 2, and by conventional synthetic method for {Rb(HC₂O₄)}_∞³, 3, allowed the identification of H-bond patterns and structural dimensionality. Ferroïc domain structures are confirmed by electric measurements performed on 3. Although 2 resembles one oxalic acid sesquihydrate, its structure determination doesn’t display any kind of disorder and leads to recognition of a supramolecular network identical to hybrid s-block series, where moreover, unusual H₃O⁺ and NH₄⁺ similarity is brought out. Thermal behaviors show that 1D frameworks with extended H-bonds, whether with or without a metal center, have the same stability. Inversely, despite the dimensionalities, the same metallic intermediate and final compounds are obtained for the two Rb⁺ ferroïc materials.     

Energetic basis of catalytic activity of layered nanophase calcium manganese oxides for water oxidation

Previous measurements show that calcium manganese oxide nanoparticles are better water oxidation catalysts than binary manganese oxides (Mn₃O₄, Mn₂O₃, and MnO₂). The probable reasons for such enhancement involve a combination of factors: The calcium manganese oxide materials have a layered structure with considerable thermodynamic stability and a high surface area, their low surface energy suggests relatively loose binding of H₂O on the internal and external surfaces, and they possess mixed-valent manganese with internal oxidation enthalpy independent of the Mn³⁺/Mn⁴⁺ ratio and much smaller in magnitude than the Mn₂O₃-MnO₂ couple. These factors enhance catalytic ability by providing easy access for solutes and water to active sites and facile electron transfer between manganese in different oxidation states.     

Hydrogen peroxide-mediated alteration of the heme prosthetic group of metmyoglobin to an iron chlorin product: Evidence for a novel oxidative pathway

Treatment of metmyoglobin with H₂O₂ is known to lead to the crosslinking of an active site tyrosine residue to the heme [Catalano, C.E., Y.S. Choe, and P.R. Ortiz de Montellano (1989) J. Biol. Chem. 264, 10534–10541]. We have found in this study that this reaction also leads to an altered heme product not covalently bound to the protein. This product was characterized by visible absorption, infrared absorption, and mass and NMR spectrometry as an iron chlorin product formed from the saturation of the double bond between carbon atoms at positions 17 and 18 of pyrrole ring D with concomitant addition of a hydroxyl group on the carbon atom at position 18 and lactonization of the propionic acid to the carbon atom at position 17. Studies with the use of ¹⁸O-labeled H₂O₂, O₂, and H₂O clearly indicate that the source of the added oxygen on the heme is water. Evidently, water adds regiospecifically to a cationic site formed on a carbon atom at position 18 after oxidation of the ferric heme prosthetic group with peroxide. Prolonged incubation of the reaction mixture containing the iron hydroxychlorin product led to the formation of an iron dihydroxychlorin product, presumably from a slow addition of water to the initial iron hydroxychlorin. The iron chlorin products characterized in this study are distinct from the meso-oxyheme species, which is thought to be formed during peroxide-mediated degradation of metmyoglobin, cytochrome P450, ferric heme, and model ferric hemes, and give further insight into the mechanism of H₂O₂-induced heme alterations.     

Aquaporin-3 mediates hydrogen peroxide uptake to regulate downstream intracellular signaling

Hydrogen peroxide (H₂O₂) produced by cell-surface NADPH Oxidase (Nox) enzymes is emerging as an important signaling molecule for growth, differentiation, and migration processes. However, how cells spatially regulate H₂O₂ to achieve physiological redox signaling over nonspecific oxidative stress pathways is insufficiently understood. Here we report that the water channel Aquaporin-3 (AQP3) can facilitate the uptake of H₂O₂ into mammalian cells and mediate downstream intracellular signaling. Molecular imaging with Peroxy Yellow 1 Methyl-Ester (PY1-ME), a new chemoselective fluorescent indicator for H₂O₂, directly demonstrates that aquaporin isoforms AQP3 and AQP8, but not AQP1, can promote uptake of H₂O₂ specifically through membranes in mammalian cells. Moreover, we show that intracellular H₂O₂ accumulation can be modulated up or down based on endogenous AQP3 expression, which in turn can influence downstream cell signaling cascades. Finally, we establish that AQP3 is required for Nox-derived H₂O₂ signaling upon growth factor stimulation. Taken together, our findings demonstrate that the downstream intracellular effects of H₂O₂ can be regulated across biological barriers, a discovery that has broad implications for the controlled use of this potentially toxic small molecule for beneficial physiological functions.     

Calcium deficient diet,acetazolamide and gas exchange characteristics of avian eggshells

The effects of calcium deficient diet and acetazolamide on the gas exchange characteristics of avian eggshells were independently investigated in two groups of unmated hens (Gallus domesticus). In one group, eggs were collected during both a normal diet (3.00% Ca) and a calcium deficient diet (0.34% Ca). In another group, eggs were collected both before and after acetazolamide administration (200 mg/kg) per os. Eggshell water vapor conductance (G_H2O) increased 30% during the calsium deficient diet and was accompanied by a 21% decrease in eggshell thickness (L). Eggshell G_H2O increased 200% one day after acetazolamide administration and was not only accompanied by a 36% decrease in L, but also by an 89% increase in total functional pore area (A_p). We conclude that a calcium deficient die increases G_H2O by eggshell thinning with litle effect on A_p. On the other hand, acetazolamide profoundly increases G_H2O, not only by eggshell thinning but also by a remarkable increase in A_p.     

Ammonia, Hydrogen Peroxide, and Monochloramine Retard Gastric Epithelial Restoration in Rabbit Cultured Cell Model

Ammonia (NH₃), hydrogen peroxide(H₂O₂) and monochloramine(NH₂Cl) produced by Helicobacter pyloriinfection might be responsible for mucosal injury. Theaim of this study was to evaluate the role ofNH₃, H₂O₂, andNH₂Cl in the restoration of rabbit primarycultured gastric mucosal cells with a wound repairmodel. Artificial wounds were made in confluentmonolayer gastric epithelial cell sheets by mechanicaldenudation, and changes in the size of the cell-freearea were analyzed quantitatively. Cell proliferation was assessed by bromodeoxyuridine staining. Incontrols, the wound healed within 48 hr. However,mucosal cell repair was inhibited by treatment withNH₃, H₂O₂, andNH₂Cl in a dose-dependent manner. These resultsindicate that NH₃,H₂O₂, and NH₂Clretarded the wound healing, which included epithelialcell migration and proliferation of gastric mucosa. Therefore, it is suggestedthat NH₃, H₂O₂, andNH₂Cl delays the healing process of pepticulcers.     

Hydrogen peroxide,an inhibitor of platelet function: Effect on adenine nucleotide metabolism,and the release reaction

The in vitro effects of H₂O₂ on platelet adenine nucleotide metabolism and on the ADP-induced platelet release reaction were examined. All studies were performed on human platelet-rich plasma (PRP) preincubated with (³ H)-adenine. Within 3 min of incubation with PRP, H₂O₂ (100–500 μM) caused an irreversible reduction in the (³ H)-ATP level with a concomitant increase in (³ H)-IMP and (³ H)-inosine and hypoxanthine levels. The adenylate energy charge (AEC) initially decreased while the ATP level fell. The AEC, however, returned to levels slightly lower than the control during further incubation. No leakage of ATP and ADP to plasma was observed. The fall in the steady-state levels of (³ H)-ATP increased with increase of the H₂O₂ concentration (decrease of 8.7–40% at H₂O₂ concentrations from 5 to 600 μM). H₂O₂ pretreatment of PRP caused absence of ADP-induced biphasic aggregation, partial inhibition of the primary wave, and complete inhibition of release of platelet nonmetabolic ATP and ADP. Our in vitro findings support the view that part of the inhibitory effect of H₂O₂ may be related to the lowering of metabolic ATP levels in platelets.     

Characterization and Performance Evaluation of Metakaolin-Based Geopolymer Foams Obtained by Adding Palm Olein as the Foam Stabilizer

Geopolymer foams with different pore structures can be used in construction, water treatment, and heavy metal adsorption. The preparation of high porosity geopolymer foams using vegetable oil as a foam stabilizer is a feasible and cost-effective route. In this study, metakaolin-based geopolymer foams with hierarchical pore structures were fabricated by adding H₂O₂ as the foaming agent with palm olein as the foam stabilizer. The effects of H₂O₂ and palm olein content on the chemical features and pore structure of geopolymer foams were evaluated. Water absorption, thermal conductivity, and mechanical behaviors of geopolymer foams were also investigated. The results indicate that fatty acid salt surfactants were generated in situ in the geopolymer matrix due to the addition of palm olein. Geopolymer foams with H₂O₂ and palm olein addition possess a homogeneously concentrated macropore distribution. Palm olein exhibits a refining effect on intrinsic pores formed by geopolymerization. In addition, using appropriate amounts of palm olein and H₂O₂, geopolymer foams can achieve higher open porosity and better pore connectivity, resulting in the improvement of water absorption and thermal insulation capacity.     

The Corrosion Behavior of Pure Iron under Solid Na2SO4 Deposit in Wet Oxygen Flow at 500 °C

The corrosion behavior of pure Fe under a Na₂SO₄ deposit in an atmosphere of O₂ + H₂O was investigated at 500 °C by thermo gravimetric, and electrochemical measurements, viz. potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and surface characterization methods viz. X-ray diffraction (XRD), and scanning electron microscope (SEM)/energy dispersive spectroscopy(EDS). The results showed that a synergistic effect occurred between Na₂SO₄ and O₂ + H₂O, which significantly accelerated the corrosion rate of the pure Fe. Briefly, NaFeO₂ was formed in addition to the customary Fe oxides; at the same time, H₂SO₄ gas was produced by introduction of water vapor. Subsequently, an electrochemical corrosion reaction occurred due to the existence of Na₂SO₄, NaFeO₂, and H₂O. When this coupled to the chemical corrosion reaction, the progress of the chemical corrosion reaction was promoted and eventually resulted in the acceleration of the corrosion of the pure Fe.     

New Heterotrinuclear CuIILnIIICuII (Ln = Ho,Er) Compounds with the Schiff Base: Syntheses,Structural Characterization,Thermal and Magnetic Properties

New heterotrinuclear complexes with the general formula [Cu₂Ln(H₂L)(HL)(NO₃)₂]·MeOH (Ln = Ho (1), Er (2), H₄L = N,N′-bis(2,3-dihydroxybenzylidene)-1,3-diaminopropane) were synthesized using compartmental Schiff base ligand in conjugation with auxiliary ligands. The compounds were characterized by elemental analysis, ATR-FTIR spectroscopy, X-ray diffraction, TG, DSC, TG-FTIR and XRD analysis. The N₂O₄ salen-type ligand coordinates 3d and 4f metal centers via azomethine nitrogen and phenoxo oxygen atoms, respectively, to form heteropolynuclear complexes having CuO₂Ln cores. In the crystals 1 and 2, two terminal Cu(II) ions are penta-coordinated with a distorted square-pyramidal geometry and a Ln^III ion with trigonal dodecahedral geometry is coordinated by eight oxygen atoms from [Cu^II(H₂L)(NO₃)]⁻ and [Cu^II(HL)(NO₃)]²⁻ units. Compounds 1 and 2 are stable at room temperature. During heating, they decompose in a similar way. In the first decomposition step, they lose solvent molecules. The exothermic decomposition of ligands is connected with emission large amounts of gaseous products e.g., water, nitric oxides, carbon dioxide, carbon monoxide. The final solid products of decomposition 1 and 2 in air are mixtures of CuO and Ho₂O₃/Er₂O₃. The measurements of magnetic susceptibilities and field dependent magnetization indicate the ferromagnetic interaction between Cu^II and Ho^III ions 1.     

Endothelium‐Derived Hyperpolarization and Coronary Vasodilation: Diverse and Integrated Roles of Epoxyeicosatrienoic Acids,Hydrogen Peroxide,and Gap Junctions

Myocardial perfusion and coronary vascular resistance are regulated by signaling metabolites released from the local myocardium that act either directly on the VSMC or indirectly via stimulation of the endothelium. A prominent mechanism of vasodilation is EDH of the arteriolar smooth muscle, with EETs and H₂O₂ playing important roles in EDH in the coronary microcirculation. In some cases, EETs and H₂O₂ are released as transferable hyperpolarizing factors (EDHFs) that act directly on the VSMCs. By contrast, EETs and H₂O₂ can also promote endothelial K_Ca activity secondary to the amplification of extracellular Ca²⁺ influx and Ca²⁺ mobilization from intracellular stores, respectively. The resulting endothelial hyperpolarization may subsequently conduct to the media via myoendothelial gap junctions or potentially lead to the release of a chemically distinct factor(s). Furthermore, in human isolated coronary arterioles dilator signaling involving EETs and H₂O₂ may be integrated, being either complimentary or inhibitory depending on the stimulus. With an emphasis on the human coronary microcirculation, this review addresses the diverse and integrated mechanisms by which EETs and H₂O₂ regulate vessel tone and also examines the hypothesis that myoendothelial microdomain signaling facilitates EDH activity in the human heart.     

Surface Modification of Additively Manufactured Nitinol by Wet Chemical Etching

Three-dimensional printed nitinol (NiTi) alloys have broad prospects for application in medicine due to their unique mechanical properties (shape memory effect and superplasticity) and the possibilities of additive technologies. However, in addition to mechanical properties, specific physicochemical characteristics of the surface are necessary for successful medical applications. In this work, a comparative study of additively manufactured (AM) NiTi samples etched in H₂SO₄/H₂O₂, HCl/H₂SO_4, and NH₄OH/H₂O₂ mixtures was performed. The morphology, topography, wettability, free surface energy, and chemical composition of the surface were studied in detail. It was found that etching in H₂SO₄/H₂O₂ practically does not change the surface morphology, while HCl/H₂SO₄ treatment leads to the formation of a developed morphology and topography. In addition, exposure of nitinol to H₂SO₄/H₂O₂ and HCl/H₂SO₄ contaminated its surface with sulfur and made the surface wettability unstable in air. Etching in NH₄OH/H₂O₂ results in surface cracking and formation of flat plates (10–20 microns) due to the dissolution of titanium, but clearly increases the hydrophilicity of the surface (values of water contact angles are 32–58°). The etch duration (30 min or 120 min) significantly affects the morphology, topography, wettability and free surface energy for the HCl/H₂SO₄ and NH₄OH/H₂O₂ etched samples, but has almost no effect on surface composition.     

From the Cover: Condensing water vapor to droplets generates hydrogen peroxide

It was previously shown [J. K. Lee et al., Proc. Natl. Acad. Sci. U.S.A., 116, 19294–19298 (2019)] that hydrogen peroxide (H₂O₂) is spontaneously produced in micrometer-sized water droplets (microdroplets), which are generated by atomizing bulk water using nebulization without the application of an external electric field. Here we report that H₂O₂ is spontaneously produced in water microdroplets formed by dropwise condensation of water vapor on low-temperature substrates. Because peroxide formation is induced by a strong electric field formed at the water–air interface of microdroplets, no catalysts or external electrical bias, as well as precursor chemicals, are necessary. Time-course observations of the H₂O₂ production in condensate microdroplets showed that H₂O₂ was generated from microdroplets with sizes typically less than ∼10 µm. The spontaneous production of H₂O₂ was commonly observed on various different substrates, including silicon, plastic, glass, and metal. Studies with substrates with different surface conditions showed that the nucleation and the growth processes of condensate water microdroplets govern H₂O₂ generation. We also found that the H₂O₂ production yield strongly depends on environmental conditions, including relative humidity and substrate temperature. These results show that the production of H₂O₂ occurs in water microdroplets formed by not only atomizing bulk water but also condensing water vapor, suggesting that spontaneous water oxidation to form H₂O₂ from water microdroplets is a general phenomenon. These findings provide innovative opportunities for green chemistry at heterogeneous interfaces, self-cleaning of surfaces, and safe and effective disinfection. They also may have important implications for prebiotic chemistry.

Water molecules in liquid water are considered stable and inert. We and other investigators have reported that water molecules become electrochemically active and catalytic for various reactions when bulk water is formed into micrometer-sized droplets (microdroplets). Reaction rates for various chemical reactions are accelerated in microdroplets by factors of 10² or more compared to bulk solution (1). The microdroplet environment provides conditions for a lowered entropic barrier, which allows thermodynamically unfavorable reactions to proceed in microdroplets at room temperature (2, 3). We also have shown that water microdroplets induce spontaneous charge exchanges between solutes and water molecules to induce the spontaneous reduction of organic molecules and metal ions as well as the formation of nanostructures without any added reducing agent or template (4, 5). Moreover, we have reported that water molecules undergo spontaneous oxidation to form reactive oxygen species, including hydroxyl radicals (OH) and hydrogen peroxide (H₂O₂) (6–8). Recent investigations attributed the origin of these unique physicochemical properties observed in microdroplets to the enrichment of reactants at the interface (9–11), restricted molecular rotations (12), partial solvation at the water surface (1, 13), and a strong interfacial electric field at the surface of the water microdroplet (14).Microdroplets can be formed either by atomizing bulk water (top down) with various methods such as high-pressure gas nebulization (15), ultrasonic nebulization (16), vibrating micromesh nebulization (17), and piezoelectric nebulization (18), or by condensing vapor-phase molecules (bottom up) (19). A question may be asked whether those unique properties of microdroplets arise only in microdroplets formed by atomization of bulk water. In addition, it may be wondered whether the spontaneous oxidation of water to form H₂O₂ in microdroplets (6) was caused by the atomizing process involving friction or vibration. These questions motivated us to investigate whether H₂O₂ becomes spontaneously generated in water microdroplets formed by the condensation of water vapor in air on cold surfaces, and how universal might this process be. We have paid special attention to the influence of different surface properties, including hydrophilicity and surface roughness, as well as environmental factors, including relative humidity and surface temperature.     

Investigations Regarding the Addition of ZnO and Li2O-TiO2 to Phosphate-Tellurite Glasses: Structural,Chemical, and Mechanical Properties

Phosphate and tellurite glasses can be used in optics, optoelectronics, magneto-optics, and nuclear and medical fields. Two series of phosphate-tellurite glasses, (50-x)ZnO-10Al₂O₃-40P₂O₅-xTeO₂ and (40-x)Li₂O-10Al₂O₃-5TiO₂-45P₂O₅-xTeO₂ (x = 5, 10), were synthesized by a non-conventional wet-route, and the mechanical properties as key performance measures for their application in optoelectronics were investigated. X-ray Diffraction (XRD) measurements revealed the vitreous nature of the investigated materials. Instrumented indentation tests allowed the calculation of hardness (H) and Young’s modulus (E) using the Oliver and Pharr model. The influence of increasing the TeO₂ content, as well as the substitution of ZnO by Li₂O-TiO₂, on the variation of hardness, Young’s modulus, penetration depth (PD), and fracture toughness (FT) was evaluated in both series. As a general trend, there is a decrease in the hardness and Young’s modulus with increasing penetration depth. The addition of Li₂O and TiO₂ instead of ZnO leads to improved hardness and elastic modulus values. Regarding the H/E ratio, it was found that the samples with lower TeO₂ content should be significantly more crack-resistant compared to the higher TeO₂ content samples. The H³/E² ratio, being lower than 0.01, revealed a poor resistance of these glasses to plastic deformation. At the same time, a decrease of the fracture toughness with increasing TeO₂ content was noticed for each glass series. Based on dilatometry measurements, the thermal expansion coefficient as well as the characteristic temperatures of the glasses were measured. Field Emission Scanning Electron Microscopy-Energy Dispersive X-ray analysis (FESEM-EDX) revealed a uniform distribution of the elements in the bulk samples. The mechanical properties of these vitreous materials are important in relation to their application as magneto-optical Faraday rotators in laser cavities.     

H2S as an Indicator of Water Supply Vulnerability and Health Risk in Low-Resource Settings: A Prospective Cohort Study

In this large-scale longitudinal study conducted in rural Southern India, we compared a presence/absence hydrogen sulfide (H₂S) test with quantitative assays for total coliforms and Escherichia coli as measures of water quality, health risk, and water supply vulnerability to microbial contamination. None of the three indicators showed a significant association with child diarrhea. The presence of H₂S in a water sample was associated with higher levels of total coliform species that may have included E. coli but that were not restricted to E. coli. In addition, we observed a strong relationship between the percent positive H₂S test results and total coliform levels among water source samples (R² = 0.87). The consistent relationships between H₂S and total coliform levels indicate that presence/absence of H₂S tests provide a cost-effective option for assessing both the vulnerability of water supplies to microbial contamination and the results of water quality management and risk mitigation efforts.     

Melatonin‐induced calbindin‐D9k expression reduces hydrogen peroxide‐mediated cell death in rat pituitary GH3 cells

Abstract: In this study, we investigated whether calbindin‐D9k (CaBP‐9k) expression was regulated by melatonin during hydrogen peroxide (H₂O₂)‐induced cell death in rat pituitary GH3 cells. CaBP‐9k expression was increased by melatonin in a dose‐ and time‐dependent manner, indicating that CaBP‐9k expression is regulated by melatonin. Cell survival was increased approximately 27–30% where H₂O₂‐treated cells (0.25 or 0.5 mm ) were also incubated with 1 mm melatonin, when compared with H₂O₂ alone or H₂O₂ plus 0.5 mm melatonin. This result was consistent with 4,6‐diamidino‐2‐phenylindole staining. CaBP‐9k expression was also augmented by co‐treatment with H₂O₂ and 1 mm melatonin, suggesting a functional relationship between increased cell death and melatonin‐induced CaBP‐9k expression during H₂O₂‐mediated apoptosis. Bcl‐2‐associated protein expression increased following treatment with H₂O₂ alone, whereas Bcl‐2 expression was elevated following treatment with melatonin alone, or H₂O₂ plus melatonin. The expression of p53 was depressed by treatment with melatonin alone, or co‐treatment with H₂O₂ plus melatonin. These results correlated with CaBP‐9k expression levels and activation of the mitogen‐activated protein kinase/extracellular signal‐regulated kinase signaling pathway. Knockdown of CaBP‐9k expression using a small inhibitory RNA resulted in an elevation of H₂O₂‐induced cell death, whereas cell survival was increased in cells that overexpressed CaBP‐9k, providing additional evidence that the induction of CaBP‐9k expression may be associated with survival signaling during H₂O₂‐mediated oxidative cell death. CaBP‐9k appears to interact with p53, suggesting a possible role for this interaction in cell proliferation and cell cycle progression.     

Non-enzymatic Hydrogen Peroxide Sensors Based on Multi-wall Carbon Nanotube/Pt Nanoparticle Nanohybrids

A novel strategy to fabricate a hydrogen peroxide (H₂O₂) sensor was developed by using platinum (Pt) electrodes modified with multi-wall carbon nanotube-platinum nanoparticle nanohybrids (MWCNTs/Pt nanohybrids). The process to synthesize MWCNTs/Pt nanohybrids was simple and effective. Pt nanoparticles (Pt NPs) were generated in situ in a potassium chloroplatinate aqueous solution in the presence of multi-wall carbon nanotubes (MWCNTs), and readily attached to the MWCNTs convex surfaces without any additional reducing reagents or irradiation treatment. The MWCNT/Pt nanohybrids were characterized by transmission electron microscope (TEM), and the redox properties of MWCNTs/Pt nanohybrids-modified Pt electrode were studied by electrochemical measurements. The MWCNTs/Pt-modified electrodes exhibited a favorable catalytic ability in the reduction of H₂O₂. The modified electrodes can be used to detect H₂O₂ in the range of 0.01–2 mM with a lower detection limit of 0.3 μM at a signal-to-noise ratio of 3. The sensitivity of the electrode to H₂O₂ was calculated to be 205.80 μA mM⁻¹ cm⁻² at working potential of 0 mV. In addition, the electrodes exhibited an excellent reusability and long-term stability as well as negligible interference from ascorbic acid, uric acid, and acetaminophen.     

Proteomic and metabolomic analysis of H2O2-induced premature senescent human mesenchymal stem cells

Stress induced premature senescence (SIPS) occurs after exposure to many different sublethal stresses including H₂O₂, hyperoxia, or tert-butylhydroperoxide. Human mesenchymal stem cells (hMSCs) exhibit limited proliferative potential in vitro, the so-called Hayflick limit. According to the free-radical theory, reactive oxygen species (ROS) might be the candidates responsible for senescence and age-related diseases. H₂O₂ may be responsible for the production of high levels of ROS, in which the redox balance is disturbed and the cells shift into a state of oxidative stress, which subsequently leads to premature senescence with shortening telomeres. H₂O₂ has been the most commonly used inducer of SIPS, which shares features of replicative senescence (RS) including a similar morphology, senescence-associated β-galactosidase activity, cell cycle regulation, etc. Therefore, in this study, the senescence of hMSC during SIPS was confirmed using a range of different analytical methods. In addition, we determined five differentially expressed spots in the 2-DE map, which were identified as Annexin A2 (ANXA2), myosin light chain 2 (MLC2), peroxisomal enoyl-CoA hydratase 1 (ECH1), prosomal protein P30-33K (PSMA1) and mutant β-actin by ESI-Q-TOF MS/MS. Also, proton (¹H) nuclear magnetic resonance spectroscopy (NMR) was used to elucidate the difference between metabolites in the control and hMSCs treated with H₂O₂. Among these metabolites, choline and leucine were identified by ¹H-NMR as up-regulated metabolites and glycine and proline were identified as down-regulated metabolites.