The effect of ionizing radiation on genetic transcription - Aspects of the mechanism.
Genetic transcription as affected by ionizing radiation and hydrogen peroxide
METABOLISM↗
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Method and apparatus for eliminating luminol interference material
A method and apparatus for removing porphyrins from a fluid sample which are unrelated to the number of bacteria present in the sample and prior to combining the sample with luminol reagent to produce a light reaction is disclosed. The method involves a pre-incubation of the sample with a dilute concentration of hydrogen peroxide which inactivates the interfering soluble porphyrins. Further, by delaying taking a light measurement for a predetermined time period after combining the hydrogen peroxide-treated water sample with a luminol reagent, the luminescence produced by the reaction of the luminol reagent with ions present in the solution, being short lived, will have died out so that only porphyrins within the bacteria which have been released by rupturing the cells with the sodium hydroxide in the luminol reagent, will be measured. The measurement thus obtained can then be related to the concentration of live and dead bacteria in the fluid sample.
Jeffers, E. L.↗
Solvent molecules form surface redox mediators in situ and cocatalyze O 2 reduction on Pd
Solvent molecules influence the reactions of molecular hydrogen and oxygen on palladium nanoparticles. Organic solvents activate to form reactive surface intermediates that mediate oxygen reduction through pathways distinct from reactions in pure water. Kinetic measurements and ab initio quantum chemical calculations indicate that methanol and water cocatalyze oxygen reduction by facilitating proton-electron transfer reactions. Methanol generates hydroxymethyl intermediates on palladium surfaces that efficiently transfer protons and electrons to oxygen to form hydrogen peroxide and formaldehyde. Formaldehyde subsequently oxidizes hydrogen to regenerate hydroxymethyl. Water, on the other hand, heterolytically oxidizes hydrogen to produce hydronium ions and electrons that reduce oxygen. These findings suggest that reactions of solvent molecules at solid-liquid interfaces can generate redox mediators in situ and provide opportunities to substantially increase rates and selectivities for catalytic reactions.
Adams, Jason S.↗
Study of basic bio-electrochemistry Sixth monthly progress report, 1-31 Aug. 1963
Contribution of hydrogen peroxide to electrode reaction in electrochemical cell by considering effect of catalyst on cell current
ELECTRIC CURRENT↗
Photodissociation of Cl2O2 in the spring Antarctic lower stratosphere
The likely photodissociation pathways of chlorine peroxide are examined. Reasoning by analogy between hydrogen peroxide and chlorine peroxide, it is shown that photodissociation of chlorine peroxide at wavelengths longer than 250 nm is not likely to give chlorine atoms as a primary product. Reasoning by analogy with molecules whose visible spectra are known, it is concluded that chlorine peroxide is also likely to photodissociate in the visible to give ClO radicals as primary products.
Eberstein, Igor J.↗
High Test Peroxide Incident at Stennis Space Center
A renewed interest n hydrogen peroxide as a rocket engine propellant has created a void in the experience base since the last era of significant peroxide use. Advanced catalyst beds and high concentration formulations are currently being developed and tested in the propulsion community. Although peroxide has many positive attributes, there are situations where peroxide must be handled with extreme care. An incident occurred at NASA's Stennis Space Center (SSC) in December 2000 where a significant over pressurization event damaged facility and test hardware. A description of the event and findings of the investigation board are presented and discussed.
Ross, R.↗
Preparation of a Bimetal Using Mechanical Alloying for Environmental or Industrial Use
Following the 1976 Toxic Substances Control Act ban on their manufacture, PCBs remain an environmental threat. PCBs are known to bio-accumulate and concentrate in fatty tissues. Further complications arise from the potential for contamination of commercial mixtures with other more toxic chlorinated compounds such as polychlorinated dibenzodioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs). Until recently, only one option was available for the treatment of PCB-contaminated materials: incineration. This may prove to be more detrimental to the environment than the PCBs themselves due to the potential for formation of PCDDs. Metals have been used for the past ten years for the remediation of halogenated solvents and other contaminants in the environment; however, zero-valent metals alone do not possess the activity required to dehalogenate PCBs. Palladium has been shown to act as an excellent catalyst for the dechlorination of PCBs with active metals. This invention is a method for the production of a palladium/magnesium bimetal capable of dechlorinating PCBs using mechanical milling/mechanical alloying. Other base metals and catalysts may also be alloyed together (e.g., nickel or zinc) to create a similarly functioning catalyst system. Several bimetal catalyst systems currently can be used for processes such as hydrogen peroxide synthesis, oxidation of ethane, selective oxidation, hydrogenation, and production of syngas for further conversion to clean fuels. The processes for making these bimetal catalysts often involve vapor deposition. This technology provides an alternative to vapor deposition that may provide equally active catalysts. A hydrogenation catalyst including a base material coated with a catalytic metal is made using mechanical milling techniques. The hydrogenation catalysts are used as an excellent catalyst for the dehalogenation of contaminated compounds and the remediation of other industrial compounds. The mechanical milling technique is simpler and cheaper than previously used methods for producing hydrogenation catalysts. Preferably, the hydrogenation catalyst is a bimetallic particle formed from a zero-valent iron or zero-valent magnesium particle coated with palladium that is impregnated onto a high-surface-area graphite support. The zero-valent metal particles should be microscale or nanoscale zero-valent magnesium or zero-valent iron particles. Other zero-valent metal particles and combinations may be used. Additionally, the base material may be selected from a variety of minerals including, but not limited to, alumina and zeolites. The catalytic metal is preferably selected from the group consisting of noble metals and transition metals, preferably palladium. The mechanical milling process includes milling the base material with a catalytic metal impregnated into a high-surface-area support to form the hydrogenation catalyst. In a preferred mechanical milling process, a zero-valent metal particle is provided as the base material, preferably having a particle size of less than about 10 microns, preferably 0.1 to 10 microns or smaller, prior to milling. The catalytic metal is supported on a conductive carbon support structure prior to milling. For example, palladium may be impregnated on a graphite support. Other support structures such as semiconductive metal oxides may also be used.
Quinn, Jacqueline↗
Aging-associated stem/progenitor cell dysfunction in the salivary glands of mice
Highlights: • The function of CD133-positive cells changes with age and is expected to be one of the causative factors associated with salivary gland aging. Although stem cell aging leads to a decline in tissue homeostasis and regenerative capacity, it remains unclear whether salivary gland stem cell function changes during this process. However, the salivary glands are gradually replaced by connective tissue during aging. Here, we show a decline in the stem cell ability of CD133-positive stem/progenitor cells in the salivary glands of aged mice. The CD133-positive cells were isolated from young, adult, and aged mice. The number of CD133-positive cells was significantly decreased in aged mice. They also showed a lower sphere formation capacity compared to young and adult mice. RNA sequencing revealed that CD133-positive cells in aged mice exhibited lower gene expression of several aging-related genes, including FoxO3a, than those in young and adult mice. Salivary gland cells infected with a recombinant lentivirus encoding the FoxO3a gene showed a reduction in oxidative stress induced by hydrogen peroxide compared with those infected with a control virus. Thus, FoxO3a may inhibit stem cell aging via oxidative stress.
60 APPLIED LIFE SCIENCES↗
Copper peroxide
A number of oxidizing agents, including chlorine, bromine, ozone and other peroxides, were allowed to act on copper solutions with the intention of forming copper peroxide. The only successful agent appears to be hydrogen peroxide. It must be used in a neutral 50 to 30 percent solution at a temperature near zero. Other methods described in the literature apparently do not work. The excess of hydrogen must be quickly sucked out of the brown precipitate, which it is best to wash with alcohol and ether. The product, crystalline under a microscope, can be analyzed only approximately. It approaches the formula CuO2H2O. In alkaline solution it appears to act catalytically in causing the decomposition of other peroxides, so that Na2O2 cannot be used to prepare it. On the addition of acids the H2O2 is regenerated. The dry substance decomposes much more slowly than the moist but is not very stable.
Moser, L.↗
An isotope harvesting beam blocker for the National Superconducting Cyclotron Laboratory
Harvesting isotopes from beam stops and other activated materials at accelerator facilities is a promising source of environmentally, scientifically and socially important radionuclides. At the Facility for Rare Isotope Beams (FRIB), a multitude of short- and long-lived radionuclides will be collected in a synergistic manner by dumping unused beams into a flowing-water beam stop. Ongoing exploratory research at the National Superconducting Cyclotron Laboratory (NSCL) with an analogous beam blocker aims towards obtaining the necessary radiochemical expertise for this endeavor. Herein we present a beam blocker and an isotope harvesting system which allows collection of a wide variety of aqueous and gaseous radionuclides. The water which flows through the beam blocker functions as an isotope production target and concurrently transports the newly formed radionuclides to collection sites. The system includes analytical instruments for online measurements of conductivity, dissolved oxygen, temperature, pressure and for detection of radiolytic products. To limit the levels of radiolytically produced hydrogen peroxide, a stainless-steel based degradation system was designed and implemented. Here, the suitability of the constructed system for the anticipated radionuclide harvesting project was demonstrated by offline tests and under irradiation with 140 MeV/u 48 Ca 20+ ions at the NSCL Coupled Cyclotron Facility.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Ferrous and Ferric Ion-Facilitated Dilute Acid Pretreatment of Lignocellulosic Biomass under Anaerobic or Aerobic Conditions: Observations of Fe Valence Interchange and the Role of Fenton Reaction
Ferrous ion co-catalyst enhancement of dilute-acid (DA) pretreatment of biomass is a promising technology for increasing the release of sugars from recalcitrant lignocellulosic biomass. However, due to the reductive status of ferrous ion and its susceptibility to oxidation with exposure to atmosphere, its effective application presumably requires anaerobic aqueous conditions created by nitrogen gas-purging, which adds extra costs. The objective of this study was to assess the effectiveness of oxidative iron ion, (i.e., ferric ion) as a co-catalyst in DA pretreatment of biomass, using an anaerobic chamber to strictly control exposure to oxygen during setup and post-pretreatment analyses. Remarkably, the ferric ions were found to be as efficient as ferrous ions in enhancing sugar release during DA pretreatment of biomass, which may be attributed to the observation that a major portion of the initial ferric ions were converted to ferrous during pretreatment. Furthermore, the detection of hydrogen peroxide in the liquors after DA/Fe ion pretreatment suggests that Fenton reaction chemistry was likely involved in DA/Fe ion pretreatments of biomass, contributing to the observed ferric and ferrous interchanges during pretreatment. These results help define the extent and specification requirements for applying iron ions as co-catalysts in DA pretreatments of biomass.
09 BIOMASS FUELS↗
Modular Electrochemical Synthesis Using a Redox Reservoir Paired with Independent Half-Reactions
Electrochemical synthesis of high-value chemicals using renewable electricity could lead to sustainability advantages over conventional chemical manufacturing. The tight coupling between paired anodic and cathodic reactions in conventional electrochemical processes, however, constrains the products and their efficiencies. Here, we demonstrate a strategy to achieve modular electrochemical synthesis (ModES) of different chemicals by decoupling and pairing the oxidative and reductive half-reactions with a heterogeneous redox reservoir (RR). Specifically, sodium nickel hexacyanoferrate (NaNiHCF) can serve as a robust and reversible RR that enables the modular production of several strong oxidants, hydrogen peroxide (H 2 O2) and sodium persulfate (Na 2 S 2 O 8 ) or active chlorine, in separate RR-coupled electrochemical processes. The system’s excellent performance and operational stability is demonstrated by continuous operation over 100 cycles (~36 h) to produce H 2 O 2 and Na 2 S 2 O 8 with a high voltage efficiency. The concept presented here highlights the prospects for using RRs to enable efficient, modular, and on-demand electrochemical synthesis of valuable chemicals.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
How a Formate Dehydrogenase Responds to Oxygen: Unexpected O 2 Insensitivity of an Enzyme Harboring Tungstopterin, Selenocysteine, and [4Fe–4S] Clusters
The reversible two-electron interconversion of formate and CO 2 is catalyzed by both nonmetallo- and metallo-formate dehydrogenases (FDHs). The latter group comprises molybdenum- or tungsten-containing enzymes with the metal coordinated by two equivalents of a pyranopterin cofactor, a cysteinyl or selenocysteinyl (Sec) ligand supplied by the polypeptide, and a catalytically essential terminal sulfido ligand. In addition, these biocatalysts incorporate one or more [4Fe–4S] clusters for facilitating long-distance electron transfer. However, an interesting dichotomy arises when attempting to understand how the metallo-FDHs react with O 2 . Whereas existing scholarship portrays these enzymes as being unable to perform in air due to extreme O 2 lability of their metal centers, studies dating as far back as the 1930s emphasize that some of these systems exhibit formate oxidase (FOX) activity, coupling formate oxidation to O 2 reduction. Therefore, to reconcile these conflicting views, we explored context-dependent functional linkages between metallo-FDHs and their cognate electron acceptors within the same organism vis-à-vis catalysis under atmospheric O 2 . Here, we report the discovery and characterization of an O 2 -insensitive FDH2 from the sulfate-reducing bacterium Desulfovibrio vulgaris Hildenborough (DvH) that ligates tungsten, Sec, and four [4Fe–4S] clusters. By advancing a robust expression platform for its recombinant production, we eliminate both the requirement of nitrate or azide during purification and reductive activation with thiols and/or formate prior to catalysis. Because the distinctive spectral signatures of formate-reduced DvH-FDH2 remain invariant under anaerobic and aerobic conditions, we benchmarked the enzyme activity in air, identifying CO 2 as the catalytic product. Full reaction progress curve analysis discloses a high catalytic efficiency when probed with a high-potential artificial electron acceptor. Furthermore, we show that DvH-FDH2 enables near-stoichiometric hydrogen peroxide production without superoxide release to achieve O 2 insensitivity. Notably, simultaneous electron transfer to cytochrome c and O 2 reveals that metal-based electron bifurcation is operational in this system. Taken together, our work proves the co-occurrence of redox bifurcated FDH and FOX activities within a metalloenzyme scaffold. These findings set the stage for uncovering previously unknown O 2 -insensitive flavin-based electron bifurcation mechanisms, as well as for developing authentic formate/air biofuel cells, engineering O 2 -stable FDHs and biohybrid metallocatalysts, and discerning formate bioenergetics of gut microbiota.
13C NMR↗
Gas–Liquid Chemical Reactions with Nanosecond Pulses: Role of Frequency and Pulse Delivery Modes
The effects of changes in the mode of delivery of nanosecond pulses in a gas-liquid plasma reactor on the formation of hydrogen peroxide, H 2 O 2 , and, as an indicator for ·OH radicals, the decoloration of methylene blue, MB, were determined for pulse delivery by a) increasing frequency with uniform pulses (5-50 kHz), b) variation of the time between bursts of pulses (burst period), c) changing the inner burst frequency (1 over the time between the pulses in the burst), and d) variation of number of pulses in a burst (N-cycles). H 2 O 2 peroxide formation was not affected by the method of pulse delivery in the range of parameters studied here and all data followed an approximately linear increase in H 2 O 2 production rate with discharge power. In contrast, the MB decoloration rate was affected by the burst modes. In terms of discharge power, the MB decoloration rate was highest for the uniform pulse mode; however, the linear trend in increase of MB decoloration with power when the burst period was varied, suggest that at higher power the burst mode may be more effective than the uniform pulsing. Consideration of the per pulse decoloration with energy per pulse and with number of pulses suggest that the burst mode can affect reactions differently from applying a uniform pulse.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Scale-Up of a Two-Stage Cu-Catalyzed Alkaline-Oxidative Pretreatment of Hybrid Poplar
A two-stage alkaline-oxidative pretreatment of hybrid poplar was investigated at scale (20 L reactor volume) with the goals of understanding how reaction conditions as well as interstage mechanical refining impact downstream process responses. The pretreatment comprises a first stage of alkaline delignification (alkaline pre-extraction) followed by a second delignification stage employing Cu-catalyzed alkaline hydrogen peroxide with supplemental O 2 (O 2 -enhanced Cu-AHP). Increasing pre-extraction severity (i.e., temperature and alkali loading) and pre-treatment oxidation (increasing H 2 O 2 loading) were found to increase mass and lignin solubilization in each stage. Lignin recovered from the first stage was subjected to oxidative depolymerization and led to aromatic monomer yields as high as 23.0% by mass. As a result, lignins recovered from the second stage Cu-AHP pretreatment liquors were shown to exhibit aliphatic hydroxyl contents more than six-fold higher than for a typical hardwood kraft lignin, indicating these lignins could serve as a biobased polyol for a range of polyurethane applications.
09 BIOMASS FUELS↗
Minimizing energy demand and environmental impact for sustainable NH 3 and H 2 O 2 production—A perspective on contributions from thermal, electro-, and photo-catalysis
There is an urgent need to provide adequate and sustainable supplies of water and food to satisfy the demand of an increasing population. Catalysis plays important roles in meeting these needs by facilitating the synthesis of hydrogen peroxide that is used in water decontamination and chemicals production, and ammonia that is used as fertilizer. However, these chemicals are currently produced with processes that are either very energy-intensive or environmentally unfriendly. This article offers the perspectives of the challenges and opportunities in the production of these chemicals, focusing on the roles of catalysis in more sustainable, alternative production methods that minimize energy consumption and environmental impact. While not intended to be a comprehensive review, the article provides a critical review of selected literature relevant to its objectives, discusses areas needed for further research, and potential new directions inspired by new developments in related fields. For each chemical, production by thermal, electro-, and photo-excited processes are discussed. Problems that are common to these approaches and their differences are identified and possible solutions suggested.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Intense cavitation-assisted electric discharge as a promising tool for water treatment
This study investigates interrelations between one-electrode Cavitation-Assisted Electric Discharge (CAED), two-electrode CAED, and recently discovered Intense CAED (I-CAED). The one-electrode CAED is a self-triggered nanosecond discharge with pulse energy in the micro-Joule range, which can be generated even by a DC voltage. I-CAED consists of a non-equilibrium part within a low-pressure cavitating region and a micro-spark traversing a liquid film. We hypothesize that CAED propagates from the high-voltage electrode as an ionization wave through bubbles of saturated vapor. Subsequently, the streamer-like discharges in the bubbles may form a continuous plasma channel. Inside the cavitating region, the plasma is strongly non-equilibrium, providing an ideal environment for generating chemically unstable species such as hydrogen peroxide (H 2 O 2 ). Plasma of I-CAED spark is characterized by high electron density and near-thermal equilibrium, emitting a continuous ultraviolet spectrum. The combination of these different discharge parts makes I-CAED in water a highly effective tool for the Advanced Oxidation Process, particularly in water disinfection. Experimentally demonstrated Electric Energy per Order value for disinfection of E. coli-contaminated water is as low as 0.135 ± 0.035 kWh/m 3 /order. Estimates show that the implementation of “dry electrodes” configuration reduces the erosion rate of the electrode material by at least one order of magnitude. Spectral analysis reveals that the continuum emission generated by I-CAED in proximity to metal electrodes deviates from the spectra of discharges spatially decoupled from the electrodes. We assume that this spectral divergence is attributable to blackbody-like emission originating from metallic nanoparticles form during the electrode's erosion process.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Decomposition Kinetics of H 2 O 2 on Pd Nanocrystals with Different Shapes and Surface Strains
Direct synthesis of hydrogen peroxide (H 2 O 2 ) from H 2 and O 2 on a Pd-based catalyst has emerged as a promising route to replace the energy-consuming, highly inefficient anthraquinone process. However, Pd is also a good catalyst for the decomposition of H 2 O 2 , thereby compromising the selectivity toward the desired product. The coupling between the formation and decomposition reactions makes it difficult to single out the most important parameter that controls the selectivity toward direct synthesis of H 2 O 2 . Herein, support-free monometallic Pd nanocrystals with different shapes and surface strains are used to investigate their impacts on the decomposition kinetics of H 2 O 2 . The kinetics are analyzed by tracking the concentration of the remaining H 2 O 2 using infrared spectroscopy. The data indicates that both surface structure and strain affect the decomposition kinetics of H 2 O 2 , but their impacts are inferior to that caused by Br – , a surface capping agent for the Pd{100} facets. The experimental results are consistent with the trend obtained through density functional theory calculations. Furthermore, this work helps shed light on the development of Pd-based catalysts for the direct synthesis of H 2 O 2 by offering strategies to mitigate the decomposition of the desired product.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗