Peroxide Degradation Research Articles

Extremophile enzyme activity lab: using catalase from Pyrobaculum calidifontis to highlight temperature sensitivity and thermostable enzyme activity.

There are places on earth that are considered to possess extreme physico-chemical characteristics as they relate to life. Surprisingly, there are microbes that have adapted various strategies that enable them to form robust communities in these environments. The microbes that live in these environments, called extremophiles, are described as being thermophilic, psychrophilic, halophilic, acidophilic, alkaliphilic, barophilic, and so on. Given that extremophiles were not discovered until relatively recently due to a view point that the environments in which they inhabited were not conducive to life, it is reasonable to conclude that the concept of extremophiles may be hard to grasp for students. Herein is described a laboratory exercise adapted from laboratory exercises that use mesophilic catalase enzymes to illustrate the influence of physico-chemical parameters on enzyme activity. Catalase is an enzyme that accelerates the degradation of hydrogen peroxide to water and oxygen gas. In addition to mesophilic catalases, the catalase from Pyrobaculum calidifontis, a hyperthermophile with an optimal growth temperature of 90°C, is used to highlight the adaptation of an enzyme to an extreme environment. A visual comparison of bubble production by the hyperthermophilic and mesophilic enzymes after heating at high temperatures dramatically illustrates differences in thermostability that will likely reinforce concepts that are given in a pre-laboratory lecture that discusses not only the extremophiles themselves but also their applications in biotechnology and possible role in the field of astrobiology.

Degradation of oil filed pollutants by hydrogen peroxide and persulfate activated over zero-valent metal

Nano zero-valent metal were prepared to activate hydrogen peroxide (HP) and persulfate (PS) for efficient degradation of hydroxypropyl guar gum (HPG) in oilfield water to avoid secondary contamination caused by transition metal ions in the homogeneous reaction. The effects of H2O2/Na2S2O8 concentration, catalyst concentration, temperature and pH on the degradation rate of HPG were comprehensively evaluated in this study. It was found that Cu0 coupled with HP or PS provided an effective treatment pathway which was based on rapid Cu0-mediated decomposition of the oxidants, resulting in complete removals by decreasing the (chemical oxygen demand) COD from 7350 mg/L to 360 mg/L, in particular when PS was employed as the oxidant. The HPG degradation rate was 81% at 45 ℃, pH 7, oxidant ratio of 2:3 (H2O2:Na2S2O8), total oxidant dosage of 10% and Cu0 dosage of 0.3 g/L. The results of this study demonstrated that the combined degradation of HPG pollutants by Cu0-activated H2O2/Na2S2O8 has a wide range of applications which provides new strategies and mechanism insights for advanced oxidation of oilfield pollutants.

Активность супероксиддисмутазы и каталазы в лишайниках с разным составом фотобионтов

Data on the activity of catalase and superoxide dismutase in the thalli of the cyanolichen Peltigera praetextata and the green algal lichen Hypogymnia physodes (See Fig. 1) at different ontogenetic conditions are not available in the literature. At the same time, the study of antioxidant system of lichen thalli with different photobionts during ontogenesis is relevant and can contribute to understanding the mechanisms of adaptation of symbionts to changing environmental conditions, and also serve as indicators of the functional state of the organism. The aim of the study was to investigate the activity of catalase and superoxide dismutase enzymes in lichen thalli P. praetextata and H. physodes at different stages of ontogenesis. P. praetextata and H. physodes thalli samples were collected from aspen and pine trunks under similar ecological conditions of mixed aspen-spruce communities in the middle taiga (62°15'15.9'' N, 33°58'746.1'' E, 61°50'17'' N, 34°23'13'' E, the Republic of Karelia) and northern taiga (64°34'13.9' 'N, 43°15'48'' E, Arkhangelsk Oblast, 64° 33'19'' N, 30°20'46'' E, the Republic of Karelia). Based on morphological features, thalli samples were divided into groups of different age. P. praetextata thalli were divided into 3 groups: virginal (pregenerative, young thalli without reproduction structures), generative (thalli with apothecia and phyllidia – structures of vegetative reproduction), and senile thalli (thalli with signs of degradation over a larger area). H. physodes thalli were divided into 2 groups: virginil and senile thalli; generative thalli with apothecia are extremely rare in the study areas. Catalase activity measured based on enzymatic degradation of hydrogen peroxide, superoxide dismutase activity was determined spectrophotometrically by inhibition of photoreduction of nitroblue tetrazolium, protein content was determined by the method Bradford. Statistical analysis of the data was carried out using one-way analysis of variance. The protein content (mg/g dry mass) in P. praetextata thalli within the studied sample averaged 1.12 ± 0.09, in H. physodes thalli – 2.45 ± 0.32. The activity of superoxide dismutase (units/mg of protein) in thalli of P. praetextata reached an average of 0.34 ± 0.12, in thalli of H. physodes – 0.09 ± 0.01. The values of catalase activity (µmol H2O2/µg protein) in P. praetextata thalli averaged 2.06 ± 0.48, H. physodes – 0.49 ± 0.07. For the thalli of the cyanolichen P. praetextata, a lower (2 times) protein content (See Fig. 2) and a higher (4-5 times) activity of superoxide dismutase (See Fig. 3) and catalase (See Fig. 4) were found in compared with the chlorobiont lichen H. physodes. The species P. praetextata belongs to the group of cyanolichens, and its photobiont is cyanobacteria of the genus Nostoc located in the algal layer of the thallus. In both lichen species, the maximum values of catalase activity were established for virginal thalli, and the minimum values for senile thalli. Perhaps this is due to the high intensity of "growth respiration" of young lichen thalli, which leads to the formation of reactive oxygen species. Differences in the activity of superoxide dismutase in thalli of different ontogenetic stages in the studied species were not shown. In the thalli of P. praetextata and H. physodes, the activity of catalase in thalli from the northern taiga communities is higher than in the thalli of the middle taiga, while the activity of superoxide dismutase, on the contrary, was on average higher in the lichen thalli of the middle taiga. This might be due to variability in the intensity of photosynthesis and respiration along the latitudinal gradient. In lichens, catalase activity can be a marker of mycobiont respiration, and superoxide dismutase activity is a marker of photobiont photosynthesis. The question of contribution of the fungal or algal components of the lichen thallus to the activity of antioxidant enzymes remains open.

Surface disinfection of wheat kernels using gas phase hydroxyl-radical processes: Effect on germination characteristics, microbial load, and functional properties.

Wheat kernels harbor a diverse microflora that can negatively affect the suitability of the grains for further processing. To reduce surface microflora, a kernel disinfection method is required that does not affect grain functionality. Three different versions of gas phase hydroxyl-radical processes were compared with the common method for grain disinfection, that is, a bleach treatment. The gas phase hydroxyl-radicals are generated by the UV-C mediated degradation of hydrogen peroxide and/or ozone in a near water-free process. It was found that treating kernels with a bleach solution could reduce total aerobic count (TAC) and fungal count to below the level of enumeration. In comparison, the gas phase hydroxyl-radical treatment, that is, H2 O2 -UV-ozone treatment, could support a 1.3 log count reduction (LCR) in TAC and a 1.1 LCR in fungal count. The microbial load reduction for the wholemeal samples was less pronounced as endophytic microorganisms were less affected by all treatments, hinting at a limited penetration depth of the treatments. Despite reducing the microbial load on the kernel surface through the bleach and H2 O2 -UV-ozone treatments, none of these treatments resulted in a reduced microbial count on grains that underwent sprouting after the treatments. No negative effect on germination power or development of the seedling was observed for any of the treatments. The gluten aggregation behavior and xylanase activity of the wholemeal also remained unchanged after the gas phase hydroxyl-radical treatments. Our findings suggest that UV-H2 O2 -ozone treatment shows promise for dry-kernel disinfection, but further optimization of the processing parameters is required.

Present and Future Perspectives on Fuel Cell Membrane Chemical Stability

Durability is key to the value proposition of proton exchange membrane (PEM) fuel cells for transportation applications. Ultimately, fuel cell vehicles need to match the lifetimes of diesel powered trucks, and last longer than lithium batteries, for widespread adoption[1]. The burden of reaching these aggressive targets falls on all components of the system, stack, and membrane electrode assembly. Of these, membrane durability remains an important area of research, in particular the chemical stability of the ionomer. The recognition of the ‘simple unzipping’ of the perfluorosulfonic acid (PFSA) backbone by hydroxyl radicals (HO·)[2],[3] and the subsequent introduction of cerium radical scavengers[4],[5] mark significant advancements in fuel cell lifetimes. Yet, even with this technology, it is unclear if this class of membranes can meet the 25,000+ hours required for heavy duty applications without additional improvements. Furthermore, recent proposals to restrict usage of fluorochemicals in many applications[6] presents a risk to the rapidly growing PEM fuel cell and water electrolysis markets. This talk will outline recent work that looks beyond simple peroxide degradation of PFSA ionomers and highlight the role of other reaction mechanisms suspected in accelerated fuel cell durability testing. Analysis of effluent water for ionomer fragments during these tests provides a greater understanding of the degradation mechanisms and suggests additional pathways beyond back-bone unzipping. Not only are these fragments useful in inferring reaction mechanisms, but there is also evidence they adsorb to the platinum surface, ultimately adding to performance decay. In other words, increased membrane durability may also result in increased catalyst stability. Finally, chemical stability of hydrocarbon membranes will be considered in light of the advances over the last two decades in understanding PFSA stability. Similarities and differences will be discussed between these two classes of PEM membrane with suggestions on how the techniques used to understand PFSA stability could be applied to hydrocarbon ionomers and advance the understanding of chemical stability in these systems.[1] Cullen, D. A.; Neyerlin, K. C.; Ahluwalia, R. K.; Mukundan, R.; More, K. L.; Borup, R. L.; Weber, A. Z.; Myers, D. J.; Kusoglu, A. New Roads and Challenges for Fuel Cells in Heavy-Duty Transportation. Nat Energy 2021, 6 (5), 462–474. .[2] Curtin, D. E.; Lousenberg, R. D.; Henry, T. J.; Tangeman, P. C.; Tisack, M. E. Advanced Materials for Improved PEMFC Performance and Life. Journal of Power Sources 2004, 131 (1), 41–48.[3] Coms, F. D. The Chemistry of Fuel Cell Membrane Chemical Degradation. ECS Trans. 2008, 16 (2), 235.[4] Frey, M. H., Pierpont, D. M., Hamrock, S. J., US 8,367,267 and US 9,431,670[5] Coms, F. D.; Liu, H.; Owejan, J. E. Mitigation of Perfluorosulfonic Acid Membrane Chemical Degradation Using Cerium and Manganese Ions. ECS Trans. 2008, 16 (2), 1735.[6] European Chemicals Agency (ECHA) proposal submitted 7th February 2023

Evaluating the efficiency of the enhanced ultrasonic–assisted hydrogen peroxide degradation of low–rank coal biogenic gas

ABSTRACT The efficiency of biogas formation from low-rank coal was improved through ultrasonic-assisted hydrogen peroxide degradation. We investigated various aspects of this process, including the mass of the small-molecule organic matter, changes in the composition of biogas components in three systems, and alterations in the microscopic morphology of coal before and after biogas formation. Our analytical methods included UV-vis spectrophotometry, drainage gas collection method, gas chromatography, infrared spectroscopy, and scanning electron microscopy. Optimal pretreatment conditions were identified with an ultrasonic power of 400 W, a reaction time of 90 min, and a reaction temperature of 60°C. The biogenic methanogenic cycle was delineated into three stages, with the raw coal and filtrate systems exhibiting fast and slow gas production stages during the first and second stages, respectively. In contrast, the residual coal system displayed slow and fast gas production stages during these stages. Methane yields were measured at 270.72 μmol g−1 (raw coal), 303.50 μmol g−1 (residual coal), and 293.43 μmol g−1 (filtrate). Pretreated coal exhibited biomethane yields (residual coal and filtrate) approximately 120% higher than untreated raw coal. Notably, the gas-forming potential of the filtrate should not be underestimated. Ultrasonic-assisted hydrogen peroxide pretreatment disrupted the macromolecular reticulation structure within the raw coal, resulting in the opening of a portion of the aromatic ring structure. This innovative approach offers a novel strategy for augmenting biomethane production from low-rank coal and furnishes a scientific foundation for advancing industrial applications.

Preparation of nickel-doped iron-based bimetallic organic framework carbonized derivatives for heterogeneous catalytic hydrogen peroxide degradation of 4-NP

A nickel-doped iron-bimetallic organic framework carbon-derived material (Fe-Ni-MOF@C) was successfully constructed by microwave-pyrolysis and used as a new non-homogeneous Fenton-like catalyst for the catalytic degradation of p-nitrophenol (4-NP) by hydrogen peroxide (H2O2). Several characterization results such as SEM and XRD show that Fe-Ni-MOF@C is successfully synthesized and has porous, strong stability and magnetic properties. Fe-Ni-MOF@C materials exhibit excellent catalytic performance for the degradation over a wide temperature (15–45 °C) and pH (3.00–9.00). Complete removal of 4-NP (30 mg/L) was achieved in 30 min at 25 °C and pH = 3. The material properties can be restored by calcination. According to the radical burst experiments, electron paramagnetic resonance spectroscopy (EPR) combined with the characterization results, the radicals acting in the Fe-Ni-MOF@C/H2O2 system are mainly •OH and, to a lesser extent, •O2−. The synergistic effect between Fe and Ni species accelerates electron transfer and radical generation, which is the reason for the material's high catalytic performance. High-performance liquid chromatography coupled with mass spectrometry (HPLC-MS) was used to analyze the main degradation products and pathways. This study demonstrates that bimetallic organic framework carbon-derived materials with synergistic effects have great application prospects as non-homogeneous Fenton-like catalysts in the field of H2O2 oxidation of organic pollutants.

An introductory laboratory class in sonochemistry

This article proposes a substantive scope and scenario of a laboratory class that introduces students to the field of sonochemistry. The class requires only basic laboratory equipment - typical laboratory glassware like graduated pipettes and conical flasks, as well as simple inorganic chemicals. It is designed to acquaint students with fundamental aspects of sonochemistry. In the qualitative aspect, they will conduct and observe some sonochemical reactions like a synthesis of hydrogen peroxide and ultrasound-assisted degradation of toxic chromates(VI) which will demonstrate the indirect consequences of water sonolysis which is the most basic sonochemical reaction, as well as they will illustrate the applications of sonochemistry. In the quantitative aspect, students will learn about how to measure the power of ultrasound and the sonochemical efficiency of the reaction and will conduct experiments allowing for the calculation of these parameters. Finally, an introduction to and demonstration of the sonocatalytic effect is planned. An evaluation system, consisting of a report and test, is also proposed.

Efficient photocatalytic production of H2O2 and photodegradation of tetracycline by CdS/square tubular g-C3N4 S-scheme heterojunction photocatalyst

Photocatalytic technology is an effective method for clean energy production and wastewater treatment. In this work, a square tubular g-C3N4 (MCN) is first synthesized by the aid of thermal polymerization of melamine in mixed KCl/LiCl molten salt and then loaded with CdS nanoparticles via a solvothermal method to obtain the final composite (MCN@CdS). This complex exhibits dual catalytic characteristics: photocatalytic oxygen reduction to produce hydrogen peroxide and photocatalytic degradation ability of antibiotics. The specific surface area (SSA) of MCN was enhanced by calcination with the help of molten salt, and the introduction of CdS expanded the absorption edge of MCN@CdS. In addition, electrochemical impedance and photocurrent spectroscopy confirmed that separation and migratory efficiency of photoproduced charge carriers could be promoted by the combination of MCN and CdS. As a result, the yield of hydrogen peroxide photocatalyzed by MCN@CdS is up to 0.95 mmol· L−1 in 80 min under visible light, which is 1.2 and 1.9 times larger than that of pure MCN and CdS. More importantly, the removal rate of tetracycline photocatalyzed by MCN@CdS, within 30 min with the participation of O2, achieved up to 99.5 %, 4 times faster than that in O2-free environment.

Inactivation of Salmonella Enteritidis on Hatchery and Table Eggs Using a Gas-phase Hydroxyl-Radical Process

Eggs represent a significant vehicle for Salmonella Enteritidis with the pathogen being transferred to chicks in the hatchery, or to consumers via table eggs. In the following, the efficacy of a gas-phase hydroxyl-radical process for decontaminating hatchery and table eggs was evaluated. Recovery of Salmonella was maximized through holding eggs in tryptic soy broth containing 20% w/v glycerol for 1 h prior to plating. By using this technique, it was possible to recover 63% of the theoretical Salmonella inoculated onto eggs. The continuous hydroxyl-radical reactor consisted of a bank of UV-C lamps (254 nm) that generated hydroxyl-radicals from the degradation of hydrogen peroxide (H2O2) mist and ozone gas. The optimal treatment was defined as that which supports a 5 log CFU/egg reduction of Salmonella without negatively affecting egg quality or leaving H2O2 residues. A process of 2% v/v H2O2 delivered at 30 mL/min with a UV-C dose of 19 mJ/cm2 and ozone (20 ppm) with a total treatment time of 10s was selected. The egg quality metrics (Haugh value, yolk index, albumin pH, yolk pH) did not negatively differ over a 35-day shelf-life at 4 or 25℃ compared to washed eggs or nontreated controls. The cuticle layer of eggs remained intact following hydroxyl-radical treatment. Fertilized eggs (n = 61) treated with the hydroxyl-radicals exhibited the same hatchery rate (75%) as nontreated controls (71–79%) with no defects (unhealed navels or red hocks) being observed. The same hydroxyl-radical treatment could be applied to table eggs to support >5 log CFU/egg reduction of Salmonella and was compatible with egg washing regimes practiced in industry. In comparison, the egg washing process based on sodium hydroxide and chlorine supported a 2.76 ± 0.38 log CFU/egg reduction of Salmonella. The hydroxyl-radical treatment represents a preventative control step to reduce the carriage of Salmonella on hatchery and table eggs.

Mechanism study on a novel Cu/Fe co-catalyzed heterogeneous particle mediated activation of hydrogen peroxide for efficient degradation of cyanides

The degradation of cyanide ions in cyanide containing wastewater is a major challenge in water treatment. This article uses a one-step hydrothermal method to prepare iron copper bimetallic oxide catalysts and applies them for the rapid degradation of cyanide (CN−). The experimental results show that under the optimal conditions, the removal rate of CN− in the bimetallic catalyst/H2O2 system is close to 100 % within 1 h, which is significantly better than the single metal oxide catalyst. Through characterization by SEM-EDS, XRD, XPS, and combined with catalytic performance experimental analysis, it was found that. There is a synergistic effect between Cu and Fe, which can effectively promote the cycling of metal ions and improve the generation efficiency of hydroxyl radicals (HO•) to a certain extent, thereby improving the degradation performance of CN−. In addition, ion chromatography was used to analyze the oxidation products and a possible pathway for CN− degradation was proposed. This provides new insights and ideas for the development of high-performance bimetallic oxide catalysts for cyanide degradation.

A Novel Analytical approach for Simultaneous Estimation of Esomeprazole and Ondansetron by HPLC-DAD Method with Degradation Studies

Objective: A simultaneous estimation of Esomeprazole and Ondansetron by HPLC-DAD method with degradation studies was developed. Method: It was carried out using Kromasil (150mm×4.6mm, 5µm particle size) column with mobile phase consists 0.01M KH2PO4 Phosphate buffer (1mL of Triethylamine added and pH was adjusted to 3.5 with Orthophosphoric acid): Acetonitrile (35:65, %v/v) with flow rate 1mL/min at 265nm. Esomeprazole and Ondansetron were eluted at 2.350 and 2.831mins respectively. Results and Discussion: Validation was performed as per ICH guidelines, which shows linearity 25-150μg/mL of Esomeprazole and 10-60μg/mL of Ondansetron with R2 was 0.999. Accuracy was obtained to be 99.75-100.21% for Esomeprazole and 99.39-100.3% for Ondansetron respectively and precision which shows %RSD less than 2%. Stress studies were carried out which shows that both Esomeprazole and Ondansetron is moderately degraded in acid, base, peroxide and thermal degradation and less degraded in photolytic degradation. Conclusion: This method was applicable for routine analysis and stability of Esomeprazole and Ondansetron.

Understanding unique tolerance limits in Hydrocotyle verticillata: From submergence to water deficiency

Hydrocotyle verticillata can tolerate varying degrees of flooding, up to complete submergence, and is at the same time extremely sensitive to drought. Understanding the structural and biochemical principles of these unusual tolerance limits is of particular importance. We analyzed the effect of soil flooding, complete submergence (rooted plants and floating stems), and dehydration on root anatomy, alcohol dehydrogenase (ADH), heat shock proteins 70 (HSP70), hydrogen peroxide, and DNA integrity using light microscopy, biochemical and histological methods. It was shown that anatomical traits of adventitious roots with a triarch stele were similar in the plants growing under different conditions; the single-layered and thin-walled epidermis formed relatively short root hairs; essential air spaces were absent in the cortex parenchyma. Results on ADH clearly showed that anaerobic energetic metabolism in root apices and individual rhizoderma cells of the mature root zone was normal for this species in optimal and suboptimal conditions, while leaves changed metabolism to anaerobic in response to submergence. Alterations in the protein spectrum were accompanied by adequate up-regulation of HSP70 under different levels of flooding and dehydration/rehydration. These results appear to indicate a flooding adaptation strategy for H. verticillata based primarily on metabolic plasticity rather than morphoanatomical adaptations. Most notably, the resistance of this species to long-term submergence has been associated with strong ADH induction in leaves, transient activation of 70 kDa isoform of HSP70 and induction of 66 kDa isoform, as well as a significant delay in the accumulation of hydrogen peroxide and DNA degradation.

Combination of curcumin and catalase protects against chondrocyte injury and knee osteoarthritis progression by suppressing oxidative stress

Knee Osteoarthritis (KOA) is an age-related progressive degenerative joint disease, which is featured with pain, joint deformity, and disability. Accumulating evidence indicated oxidative stress plays a crucial role in the occurrence and development of KOA. Curcumin is a polyphenolic compound with significant antioxidant activity among various diseases while catalase (CAT) is an enzyme degrading hydrogen peroxide in treating oxidative diseases. We previously showed that the expression of CAT was low in cartilage. However, the combination of curcumin and CAT in KOA is still elusive. In this study, we demonstrated that the combination of curcumin and CAT has the potential to inhibit the IL1β-induced chondrocyte apoptosis without cytotoxicity in vitro. Mechanistically, we found that the synergistic application curcumin and CAT not only promotes curcumin's regulation of the NRF2/HO-1 signaling pathway to enhance antioxidant enzyme expression to remove superoxide radicals, but also CAT can further remove downstream hydrogen peroxide which enhances the ability to scavenge reactive oxygen species (ROS). In vivo, studies revealed that combination of curcumin and catalase could better inhibit oxidative stress-induced chondrocyte injury by promoting the expression of ROS scavenging enzymes. In sum, the combination of curcumin and catalase can be used to treat KOA. Thus, combination of curcumin and catalase may act as a novel therapeutic agent to manage KOA and our research gives a rationale for their combined use in the therapeutic of KOA.

Neuroprotective Bioorthogonal Catalysis in Mitochondria Using Protein‐Integrated Hydrogen‐Bonded Organic Frameworks

AbstractMitochondria‐targeted bioorthogonal catalysis holds promise for controlling cell function precisely, yet achieving selective and efficient chemical reactions within organelles is challenging. In this study, we introduce a new strategy using protein‐integrated hydrogen‐bonded organic frameworks (HOFs) to enable synergistic bioorthogonal chemical catalysis and enzymatic catalysis within mitochondria. Utilizing catalytically active tris(4,4′‐dicarboxylicacid‐2,2′‐bipyridyl) ruthenium(II) to self‐assemble with [1,1′‐biphenyl]‐4,4′‐biscarboximidamide, we synthesized nanoscale RuB‐HOFs that exhibit high photocatalytic reduction activity. Notably, RuB‐HOFs efficiently enter cells and preferentially localize to mitochondria, where they facilitate bioorthogonal photoreduction reactions. Moreover, we show that RuB‐HOFs encapsulating catalase can produce hydrogen sulfide (H2S) in mitochondria through photocatalytic reduction of pro‐H2S and degrade hydrogen peroxide through enzymatic catalysis simultaneously, offering a significant neuroprotective effect against oxidative stress. Our findings not only introduce a versatile chemical toolset for mitochondria‐targeted bioorthogonal catalysis for prodrug activation but also pave the way for potential therapeutic applications in treating diseases related to cellular oxidative stress.

Neuroprotective Bioorthogonal Catalysis in Mitochondria Using Protein-Integrated Hydrogen-Bonded Organic Frameworks.

Mitochondria-targeted bioorthogonal catalysis holds promise for controlling cell function precisely, yet achieving selective and efficient chemical reactions within organelles is challenging. In this study, we introduce a new strategy using protein-integrated hydrogen-bonded organic frameworks (HOFs) to enable synergistic bioorthogonal chemical catalysis and enzymatic catalysis within mitochondria. Utilizing catalytically active tris(4,4'-dicarboxylicacid-2,2'-bipyridyl) ruthenium(II) to self-assemble with [1,1'-biphenyl]-4,4'-biscarboximidamide, we synthesized nanoscale RuB-HOFs that exhibit high photocatalytic reduction activity. Notably, RuB-HOFs efficiently enter cells and preferentially localize to mitochondria, where they facilitate bioorthogonal photoreduction reactions. Moreover, we show that RuB-HOFs encapsulating catalase can produce hydrogen sulfide (H2 S) in mitochondria through photocatalytic reduction of pro-H2 S and degrade hydrogen peroxide through enzymatic catalysis simultaneously, offering a significant neuroprotective effect against oxidative stress. Our findings not only introduce a versatile chemical toolset for mitochondria-targeted bioorthogonal catalysis for prodrug activation but also pave the way for potential therapeutic applications in treating diseases related to cellular oxidative stress.

Study of enhancing photocatalytic activity of solvothermal grown MoS2 nanocrystals under visible light irradiation by the influence of hydrogen peroxide

In this article, two-dimensional molybdenum sulfide has been synthesized by simple and conventional solvothermal methods and the combined effect of MoS2 nanocrystals and hydrogen peroxide in photocatalytic degradation of methylene blue (MB) in water has been investigated under visible light. Synthesized MoS2 nanocrystals have been characterised by FEG-TEM, FE-SEM, XRD, Raman, FTIR, UV–Vis absorption, PL and TCSPC studies. FEG-TEM and FE-SEM images confirm nanosheets/nanoflowers like morphology and Raman & XRD patterns confirm the 2H-MoS2 phase. Layer-dependent absorption spectra and its Tauc plot were studied and the calculated band gap are found to be 1.73 eV and 1.43 eV for a few layers, bulk MoS2 respectively. This layer-dependent band gap energy is also verified by calculating electronic band structure for mono-layer, bi-layer and bulk MoS2 through density functional theory (DFT). The calculated average lifetime of in MoS2 is 1.5 ns. The kinetic study of the degradation of MB dye with MoS2 in the presence of H2O2 showed complete degradation of MB within 20 min. Whereas, pure MoS2 and H2O2 showed 28.27 % and 89.2 % degradation of MB within 210 min time intervals respectively. Thus, these results show MoS2 has good photocatalytic activity in the presence of H2O2.

Activation of H2O2 via sulfide-modified nanoscale zero-valent iron for tetracycline removal: Performance and mechanism

Tetracycline (TC) is widely detected in various environments and promotes bacterial resistance. In the present research, sulfide-modified nanoscale zero-valent iron (S-nZVI) was fabricated and used as activator of hydrogen peroxide (H2O2) for TC degradation. Sulfidation could improve the hydrophobicity of nZVI and its reactivity for TC degradation by up to 260 %. The reaction rate constant of the S-nZVI/H2O2 system was 16 times faster than that of the S-nZVI system. The quenching experiments results proved that •OH was the predominant radical involved in TC degradation. •OH played a significant role in ferryl ion (Fe(IV)) formation under acid conditions, while TC plays crucial roles under neutral pH condition in Fe(IV) formation by accelerating Fe(III) oxidation into Fe(IV). The possible degradation pathways were analyzed, and the toxicity analysis confirmed that the S-nZVI/H2O2 system is an effective method for degrading, and thus reducing the toxicity of TC. Therefore, this study suggests the possibility of an S-nZVI/H2O2 system for the efficient degradation of TC.

Bicarbonate-Activated Hydrogen Peroxide for an Azo Dye Degradation: Experimental Design

The present study investigated the degradation of an aqueous Allura Red AC (AR–AC) solution by activating hydrogen peroxide with bicarbonate using cobalt ion (Co2+) as the catalyst. Four independent variables (H2O2, NaHCO3, Co2+, and dye concentrations) were analyzed in the composite central design (CCD). AR–AC degradation was optimized using the response surface methodology (RSM). Under optimal degradation conditions (41.86 mg/L AR–AC, 5.58 mM H2O2, 2.00 mM NaHCO3, and 9.00 µM Co2+), decolorization > 99.86%, mineralization (CO2 to conversion) of 12.99%, and total nitrogen removal of 51.97% were achieved. The predicted values for the three response variables were consistent with the experimental values, with determination coefficients (R2) greater than 0.9053. Because cobalt ions (Co2+) are a source of water pollution, after oxidation, these were adsorbed on sodium bentonite (Na–Bent), obtaining a final concentration of <0.01 mg/L. Bicarbonate-activated hydrogen peroxide is a potential technology for dye wastewater treatment that operates at an alkaline pH and at ambient temperature.

Probing conformational kinetics of catalase with and without magnetic field by single-entity collision electrochemistry

The conformational motions of enzymes are crucial for their catalytic activities, but these fluctuations are usually spontaneous and unsynchronized and thus difficult to obtain from ensemble-averaged measurements. Here, we employ label-free single-entity electrochemical measurements to monitor in real time the fluctuating enzymatic behavior of single catalase molecules toward the degradation of hydrogen peroxide. By probing the electrochemical signals of single catalase molecules at a carbon nanoelectrode, we were able to observe three distinct current traces that could be attributed to conformational changes on the sub-millisecond timescale. Whereas, nearly uniform single long peaks were observed for single catalase molecules under a moderate magnetic field due to the restricted conformational changes of catalase. By combining high-resolution current signals with a multiphysics simulation model, we studied the catalytic kinetics of catalase with and without a magnetic field, and further estimated the maximum catalytic rate and conformational transition rate. This work introduces a new complementary approach to existing single-molecule enzymology, giving further insight into the enzymatic reaction mechanism.