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Singlet molecular oxygen evolution upon simple acidification of aqueous hypochlorite: Application to studies on the deleterious health effects of chlorinated drinking water

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Abstract

A study of the pH profile of the decomposition of aqueous hypochlorite has revealed the evolution (onset at pH 8) of single (1 delta g) molecular oxygen (singlet spin state dioxygen) detected spectroscopically (1268 nm), prior to the appearance of chlorine (onset at pH 5.5). The possible mechanism of the singlet state dioxygen evolution is presented, and the origin of its chloride ion dependence is discussed, especially in reference to chloride ion dependence of singlet molecular oxygen evolution in biological systems. Recent epidemiological analyses of the correlation of human cancer with chlorinated water supplies focus attention on the singlet oxygen mechanisms of DNA lesion formation.

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... The disinfecting efficiency of the chlorine residue decreases significantly as the pH rises. Reports by Khan and Kasha (1994) indicated that acidification of sodium hypochlorite yielded singlet oxygen (onset at pH 8, 1268 nm) before the appearance of chlorine (onset at pH 5.5). The highest emission intensity was observed by adding 200 µl concentrated HCl to a 5 ml 0.6 M sodium hypochlorite solution with a final pH of 5. Singlet oxygen is a powerful oxidant and as such a strong antimicrobial agent that reacts with lipids, proteins and nucleic acids. ...
... Reports by Khan and Kasha (1994) (1) Haber-Weiss: ...
... al. 2003). In addition, some chloramines (e.g., chloramines T) can react with hydrogen peroxide resulting in the generation of singlet oxygen (Khan and Kasha, 1994 Sporolactobacillus, and thermophilic actinomycetes also produce spores (Russell, 1990). The bacterial spore is a complex entity and its resistance appears to be associated with both the spore coats and the cortex. ...
... It is thus expected that PMS can show good performance in lowering the COD of CWC. In addition, chlorine gas and singlet oxygen could be also formed during the PMS/chloridion process [22]. In this case, hypochlorous acids, chlorine gas, singlet oxygen and chlorine radicals could contribute to the degradation of organic pollutants during the PMS/chloridion process. ...
... Ethanol was thus used as the scavenger of both hydroxyl radicals and sulfate radicals [26,27]. Singlet oxygen could be also produced by the decomposition of hypochlorite [22]. Thus, sodium azide was selected as the scavenger of singlet oxygen [28]. ...
... The singlet oxygen could be derived from the decomposition of hypochloric acids as Eq. (6) [22]. In addition, considering that the redox potential of hypochloric acids (1.48 V) is lower than that of PMS (1.8 V), it is thus speculated that PMS may react with hypochloric acids to form singlet oxygen (Eq. ...
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... In order to discern if this nonlocal photon coupling could be reproduced with a more direct photon reaction, we selected a classic physical chemical process: H 2 O 2 + NaClO → H 2 O + NaCl + O 2 or more precisely HOOH + OCl -→ 1 O 2 for generating photons [11]. The source of the photon has been attributed to the excited singlet oxygen 1 O 2 . ...
... At the end of 6 min, the AD field was stopped and the DI field was activated from the computer, which required about 50 s, and occurred continuously for the next 12 min. Starting at 9 min single quantities of 0.1 cc of hydrogen peroxide were injected during the odd minutes (9,11,13,15) and the simultaneous "double" quantities at the nonlocal and local dishes were injected during even minutes (10, 12, 14, 16, 18 min). Each injection by both experiments required ~2 s and was always verified independently by stopwatches. ...
... tion of this "window" for the "doubling" of photon emission, the duration of the first standard component, AD, was varied in a randomized order over several days to be: 0.5, 1, 2, 3, 4, 6, 8, 9, 10, 12 and 16 min before the standard AI field was initiated. The sequence of single and double injections followed the same procedure as usual: single injections 1, 3,5,9,11,13,15, and 17 min after the beginning of the experiment and nonlocal + local paired injections 2, 4, 6, 10, 12, 14, 16, and 18 min after the beginning of the experiment. The emergence of the local + nonlocal paired injection effect was measured by averaging the duration of those photon spikes and subtracting the values from the previous spike durations of the local injections. ...
Article
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The aim of the present experiments was to dis-cern if the "entanglement"-like photon emis-sions from pairs of cell cultures or human brains separated by significant distances but sharing the same circling magnetic field could be dem-onstrated with a classic chemiluminescent re-action produced by hydrogen peroxide and hy-pochlorite. Simultaneous injection of the same amount of peroxide into a local dish (above a photomultiplier tube) and a dish 10 m away in a closed chamber produced a "doubling" of the durations of the photon spikes only when the two reactions were placed in the center of sepa-rate spaces around each of which magnetic fields were generated as accelerating group ve-locities containing decreasing phase modula-tions followed by decelerating group velocities embedded with increasing phase modulations. The duration of this "entanglement" was about 8 min. These results suggest that separate dis-tances behave as if they were "the same space" if they are exposed to the same precise temporal configuration of magnetic fields with specific angular velocities.
... 16,17 However, this technique relies on the availability of both dissolved oxygen and light penetration, which are also limiting factors in PDT. 3 Thermal decomposition of endoperoxides, 18 dioxetanes and dioxiranes, 19 or perchromate, 20 and catalytic decomposition of peroxomonosulfate by LaMnO3 perovskites 21 have been employed to generate 1 O2, but the starting materials are not commonly available or are toxic and are thus unsuitable for industrial use. Khan and Kasha discovered that the simple chemical reaction between hypochlorite ions and hydrogen peroxide (H2O2), 22,23 or acidification of hypochlorite, 24 was capable of producing 1 O2 in aqueous solutions, which offered the possibility of generating 1 O2 for both fundamental and applied research. However, the presence of hypochlorite in reaction media can result in unwanted chlorination of substrates, and this reaction is fairly rapid and not easily controlled. ...
... Even if a small number of chlorine radicals are generated, they are not the main reactive species in the system and are unlikely to chlorinate substrates because they will react with the excess amount of H2O2 to form • OH and 1 O2. [22][23][24] In addition to small amounts of • OH, a small amount of superoxide radicals (O2 •-) were detected in the system through reaction with the chromogenic XTT dye ( Supplementary Fig. 7), 37 which is reduced by O2 •-, but is present at concentrations far less than the 1 O2 generated. ...
Preprint
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p>Singlet oxygen (<sup>1</sup>O<sub>2</sub>), a widely used reactive oxygen species (ROS) in industry and biomedical applications, plays a fundamental role throughout nature. We report a novel method to generate <sup>1</sup>O<sub>2</sub>selectively and efficiently through copper-based Fenton chemistry under circumneutral conditions enhanced by chloride as co-catalyst, with reactivity completely different than that observed in classical iron-based Fenton chemistry. The mechanism of its formation was elucidated through the kinetic studies of orthogonally reactive reporter molecules, i.e., singlet oxygen sensor green, 4-hydroxy-2,2,6,6-tetramethylpiperidine, and phenol, and selective ROS quenchers. This method selectively generates <sup>1</sup>O<sub>2</sub> in situ neither relying on photosensitization nor resulting in side reactions, and together with the mechanistic understanding of the Cu-Fenton reaction, not only opens new possibilities in many industries, such as organic synthesis and antimicrobial treatments, but also provides insight into Cu and H<sub>2</sub>O<sub>2</sub>containing chemical, environmental, and biological systems.</p
... These features confer a great deal of biological and chemical significance on this reactive oxygen species. Singlet oxygen can be produced as a product in a (ground state) reaction between sodium hypochlorite and hydrogen peroxide [6]. It can also be generated through direct laser excitation of 3 O 2 at~1064 nm [7]. ...
Article
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Singlet oxygen (1O2) is the excited state electronic isomer and a reactive form of molecular oxygen, which is most efficiently produced through the photosensitized excitation of ambient triplet oxygen. Photochemical singlet oxygen generation (SOG) has received tremendous attention historically, both for its practical application as well as for the fundamental aspects of its reactivity. Applications of singlet oxygen in medicine, wastewater treatment, microbial disinfection, and synthetic chemistry are the direct results of active past research into this reaction. Such advancements were achieved through design factors focused predominantly on the photosensitizer (PS), whose photoactivity is relegated to self-regulated structure and energetics in ground and excited states. However, the relatively new supramolecular approach of dictating molecular structure through non-bonding interactions has allowed photochemists to render otherwise inactive or less effective PSs as efficient 1O2 generators. This concise and first of its kind review aims to compile progress in SOG research achieved through supramolecular photochemistry in an effort to serve as a reference for future research in this direction. The aim of this review is to highlight the value in the supramolecular photochemistry approach to tapping the unexploited technological potential within this historic reaction.
... The standard reaction equation between hypochlorite and hydrogen is NaOCl + H 2 O 2 → O 2 + NaCl + H 2 O in which the oxygen is initially produced in singlet form. 50 This highly exothermic reaction under normal conditions is not reversible. Enzymes such as myoperoxidase in a neutrophil can reverse the reaction to produce HOCl because they lower the activation ener-gy substantially. ...
Article
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Wound complications such as infection continue to inflict enormous financial and patient quality-of-life burdens. The traditional practice of using antiseptics and antibiotics to prevent and/or treat infections has been questioned with increasing concerns about the cytoxitity of antiseptics and proliferation of antibiotic resistant bacteria. Solutions of sodium hypochlorite (Hod), commonly known as Dakin's solution, have been used in wound care for 100 years. In the last 15 years, more advanced HOCl acid solutions, based on electrochemistry, have emerged as safe and viable wound-cleansing agents and infection treatment adjunct therapies. After developing a literature-based sun-unary of available evidence, a consensus panel of wound care researchers and practitioners met to review the evidence for 1) the antimicrobial effectiveness of HOCl based On in vitro studies, 2) the safety of HOCl solutions, and 3) the effectiveness of HOCl acid in treating different types of infected wounds in various settings and to develop recommendations for its use and application to prevent wound infection and treat infected wounds in the context of accepted wound care algorithms. Each participant gave a short presentation; this was followed by a moderated roundtable discussion with consensus-making regarding conclusions. Based on in vitro studies, the antimicrobial activity of HOCl appears to be comparable to other antiseptics but without cytotoxicity; there is more clinical evidence about its safety and effectiveness. With regard to the resolution of infection and improvement in wound healing by adjunct HOCl use, strong evidence was found for use in diabetic foot wounds; moderate evidence for use in septic surgical wounds; low evidence for venous leg ulcers, wounds of mixed etiology, or chronic wounds; and no evidence for burn wounds. The panel recommended HOCl should be used in addition to tissue management, infection, moisture imbalance, edge of the wound (the TIME algorithm) and aggressive debridement. The panel also recommended intralesional use of HOCl or other methods that ensure the wound is covered with the solution for 15 minutes after debridement. More controlled clinical studies are needed to determine the safety and efficacy of HOCl in wound types with limited outcomes data and to evaluate outcomes of various application methods.
... The singlet oxygen ( l O 2 ) is formed from hypochlorite either in the presence of hydrogen peroxide or upon its simple acidification onset at pH 8 [36] and plays a significant role in oxidative stress. l O 2 production by the spontaneous dismutation of O •− 2 does have also physiological relevance. ...
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Fibrinogen is one of the plasma proteins most susceptible to oxidative modification. It has been suggested that modification of fibrinogen may cause thrombotic/bleeding complications associated with many pathophysiological states of organism. We exposed fibrinogen molecules to three different modification reagents-malondialdehyde, sodium hypochlorite, and peroxynitrite-that are presented to various degrees in different stages of oxidative stress. We studied the changes in fibrin network formation and platelet interactions with modified fibrinogens under flow conditions. The fastest modification of fibrinogen was caused by hypochlorite. Fibers from fibrinogen modified with either reagent were thinner in comparison with control fibers. We found that platelet dynamic adhesion was significantly lower on fibrinogen modified with malondialdehyde and significantly higher on fibrinogen modified either with hypochlorite or peroxynitrite reflecting different prothrombotic/antithrombotic properties of oxidatively modified fibrinogens. It seems that, in the complex reactions ongoing in living organisms at conditions of oxidation stress, hypochlorite modifies proteins (e.g., fibrinogen) faster and more preferentially than malondialdehyde. It suggests that the prothrombotic effects of prior fibrinogen modifications may outweigh the antithrombotic effect of malondialdehyde-modified fibrinogen in real living systems.
... This indicates that ClO − oxidizes the TMB that did not react H 2 O 2 , adding to the signal. Alternative reactions between ClO − and H 2 O 2 , e.g., the production of 1 O 2 [59] cannot be ruled out. Figure 3D shows that 1 O 2 reacts readily with TMB to produce the blue complex 2. 1 O 2 is a metastable ROS that has a lifetime of 3.5 µs in PBS. Therefore, it was generated in situ by irradiation of Rose Bengal (a well-known 1 O 2 photosensitizer) with green light [50]. ...
Article
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Photoacoustic imaging is attracting a great deal of interest owing to its distinct advantages over other imaging techniques such as fluorescence or magnetic resonance image. The availability of photoacoustic probes for reactive oxygen and nitrogen species (ROS/RNS) could shed light on a plethora of biological processes mediated by these key intermediates. Tetramethylbenzidine (TMB) is a non-toxic and non-mutagenic colorless dye that develops a distinctive blue color upon oxidation. In this work, we have investigated the potential of TMB as an acoustogenic photoacoustic probe for ROS/RNS. Our results indicate that TMB reacts with hypochlorite, hydrogen peroxide, singlet oxygen, and nitrogen dioxide to produce the blue oxidation product, while ROS, such as the superoxide radical anion, sodium peroxide, hydroxyl radical, or peroxynitrite, yield a colorless oxidation product. TMB does not penetrate the Escherichia coli cytoplasm but is capable of detecting singlet oxygen generated in its outer membrane.
... 1 O 2 is the major damaging ROS in plants (Triantaphylides et al., 2008), and it is formed primarily by energy transfer from the triplet state of cellular photosensitizers such as Chl, other tetrapyrroles, retinals, and flavins (Knox and Dodge, 1985;Krieger-Liszkay, 2005). 1 O 2 can also be formed chemically with H 2 O 2 and hypochlorite (Rosen and Klebanoff, 1977;Khan and Kasha, 1994), or through lipid hydroperoxides (Miyamoto et al., 2014). Unlike O 2˙À and H 2 O 2 , 1 O 2 is not detoxified through enzymatic reactions; it is quenched chemically or physically by various antioxidants (Triantaphylides and Havaux, 2009), such as tocopherols and carotenoids (Figure 4). ...
Article
Plants and algae require light for photosynthesis, but absorption of too much light can lead to photo-oxidative damage to the photosynthetic apparatus and sustained decreases in the efficiency and rate of photosynthesis (photoinhibition). Light stress can adversely affect growth and viability, necessitating that photosynthetic organisms acclimate to different environmental conditions in order to alleviate the detrimental effects of excess light. The model unicellular green alga, Chlamydomonas reinhardtii, employs diverse strategies of regulation and photoprotection to avoid, minimize, and repair photo-oxidative damage in stressful light conditions, allowing for acclimation to different and changing environments. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
... The potential of HOCl to initiate lipid peroxidation is contentious. Nevertheless, it is well-established that in the presence of peroxides, HOCl can form singlet molecular oxygen O 2 ð 1 D g Þ (11) [28]. ...
Article
Nanosized titanium dioxide (TiO(2)) is a common component of sunscreen preparations and cosmetics as it reflects UV and visible light in accordance to Rayleigh's law. However, in aqueous environments, TiO(2) is an efficient photocatalyst, producing superoxide (O(2)(-•)) and hydroxyl (HO(•)) radicals, which are highly damaging to biomolecules. We investigated the role of TiO(2) in promoting the peroxidation of linoleic acid (LA) alone and in the presence of hypochlorous acid (HOCl). TiO(2) significantly enhanced peroxidation of LA, which was further enhanced in the presence of HOCl. This latter finding involved the formation of singlet molecular oxygen in a Russell-type mechanism appearing to involve preformed lipid hydroperoxides (LOOH). In addition to lipid peroxidation, HOCl also mediated formation of 18:1 monochlorohydrins, which in the presence of TiO(2) appeared to decompose to kinetic products which supplemented peroxidation of linoleic acid. We present a theoretical mechanism which fits the available experimental data and may partially explain the dichotomy associated with HOCls role in lipid modification.
... The Cl atom in HOCl behaves like Cl + , a strong electrophile, and combines with a pair of electrons in the substrate. In addition, it has been reported that singlet oxygen ( 1 O 2 ) is generated in neutral and mildly acidic solutions of HOCl (13). Moreover, in the presence of superoxide (O 2 -• ) or reduced metal ions, HOCl may generate hydroxyl radicals ( • OH) (14,15). ...
Article
Hypochlorous acid (HOCl), generated by myeloperoxidase from H2O2 and Cl–, plays an important role in host defense and inflammatory tissue injury. We report here the identification of products generated from 2′-deoxyguanosine (dGuo) with HOCl. When 1 mM dGuo and 1 mM HOCl were reacted at pH 7.4 and 37°C for 15 min and the reaction was terminated with N‐acetylcysteine (N-AcCys), two products were generated in addition to 8-chloro-2′-deoxyguanosine (8-Cl-dGuo). One was identified as an amino-imidazolone nucleoside (dIz), a previously reported product of dGuo with other oxidation systems. The other was identified as a novel diimino-imidazole nucleoside, 2,5-diimino-4-[(2-deoxy-β-d-erythro-pentofuranosyl)amino]-2H,5H-imidazole (dDiz) by spectrometric measurements. The yields were 1.4% dDiz, 0.6% dIz and 2.4% 8-Cl-dGuo, with 61.5% unreacted dGuo. Precursors of dDiz and dIz containing a chlorine atom were found in the reaction solution in the absence of termination by N-AcCys. dDiz, dIz and 8-Cl-dGuo were also formed from the reaction of dGuo with myeloperoxidase in the presence of H2O2 and Cl– under mildly acidic conditions. These results imply that dDiz and dIz are generated from dGuo via chlorination by electrophilic attack of HOCl and subsequent dechlorination by N-AcCys. These products may play a role in cytotoxic and/or genotoxic effects of HOCl.
... Hence, the study of the possible interaction between H 2 O 2 and À OCl is a forced step towards understanding their meaning in the chemistry of the environment. In effect, the reaction between H 2 O 2 and À OCl has also been analysed for several decades (Brestel, 1985;Connick, 1947) and it is demonstrated by Khan and Kasha (1994) that this reaction produces singlet molecular oxygen ( 1 O 2 ). ...
Article
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We studied the reaction between hypochlorite anion (-OCl) and hydrogen peroxide (H2O2) by using spin-trapping agents such as 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) and 5-diethoxy-phosphoryl-5-methyl-1-pyrroline-N-oxide (DEPMPO). The obtained data demonstrate that hydroxyl radical is produced in this reaction. Thus, -OCl and H2O2 could assume new relevance in environmental chemistry by representing a potential source of hydroxyl radicals and other oxidant species, such as HO-OCl and (OCl)-O-center dot radical. (C) 2008 Elsevier Ltd. All rights reserved.
... It should be noted that NO also enhanced hydrogen peroxide (H2O2)-mediated microvascular endothelial permeability, and this NO effect was concentration dependent [146] . McQuaid et al [170] demonstrated that the permeability produced by H2O2 could be exacerbated when relatively high levels of NO (100 μM sodium nitroprusside) were present, and this endothelial dysfunction may be associated with generation of singlet oxygen from H2O2 [171] . NO did not affect H2O2 metabolism by endothelial cells but markedly depleted intracellular glutathione [146] . ...
Research
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This work for the first time provide evidence that T. gondii may be an environmental factor responisble for inducing development of autism spectrum disorders
... Added to these is the singlet oxygen ( 1 O 2 ) with spin reversal formed from peroxo groups on oxidation by hypohalous acids. Known as reactive oxygen species (ROS), these are responsible for many of the essential actions and also the damages attributed to oxygen (Khan and Kasha, 1994). ...
... In bacteria, sodium hypochlorite has been shown to elicit responses similar to those produced by hydrogen peroxide. Bacterial treatment with these oxidative chemicals causes the generation of superoxide anions (oxygen singlets) and hydroxyl radicals, which are presumed to account for the major bactericidal activity (Albrich and Hurst 1982; Candeias et al. 1993; Dukan and Touati 1996; Imlay and Linn 1986; Khan and Kasha 1994a, b; hence, it has been speculated that sodium hypochlorite functions by similar mechanisms as other oxidizing agents (Miller and Britigan 1997). ...
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Tuberculosis is a common and often deadly infectious disease caused by mycobacteria, mainly Mycobacterium tuberculosis and infrequently by other subspecies of the M. tuberculosis complex, such as M. bovis. Sodium hypochlorite (bleach) is routinely used in hospitals and health care facilities for surface sterilization; however, the modes of action of bleach on M. bovis BCG and how this organism develops resistance to sodium hypochlorite have not been elucidated. In this study, we performed a global toxicogenomic analysis of the M. bovis response to 2.5 mM sodium hypochlorite after 10 and 20 min. M. bovis BCG growth was monitored by measuring the quantity of ATP in picomoles produced over a short exposure time (10-60 min) to sodium hypochlorite. This study revealed significant regulation of oxidative stress response genes of M. bovis BCG, such as oxidoreductase, peroxidase, heat shock proteins and lipid transport, and metabolism genes. We interpreted this response as a potentially more lethal interplay between fatty acid metabolism, sulfur metabolism, and oxidative stress. Our results also suggest that sodium hypochlorite repressed transcription of genes involved in cell wall synthesis of M. bovis. This study shows that the treatment of M. bovis BCG with bleach inhibits the biosynthesis of outer cell wall mycolic acids and also induces oxidative damage.
... With the exception of macrophages, all phagocytic cells show detectable levels of MPO (Hassett and Cohen 1989). HOCl reacts with a wide range of cellular components causing (1) sulfhydryl oxidation, (2) inactivation of iron-sulfur centers, (3) inactivation of enzymes involved in respiration, (4) disruption of nutrient transport, (5) inhibition of energy generation, and (6) inactivation of chromosomal DNA replication (Khan and Kasha 1994;Leyer and Johnson 1997;Mokgatla et al. 2002). Resistance to HOCl is thought to depend on similar molecular mechanisms as those described for hydrogen peroxide. ...
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To survive, Salmonella enterica serovar Typhimurium (S. Typhimurium) must sense signals found in phagocytic cells and modulate gene expression. In the present work, we evaluated the expression and cross-regulation of the transcription factors MarA, Rob, and SoxS in response to NaOCl. We generated strains ΔsoxS and ΔmarA, which were 20 times more sensitive to NaOCl as compared to the wild-type strain; while Δrob only 5 times. Subsequently, we determined that marA and soxS transcript and protein levels were increased while those of rob decreased in a wild-type strain treated with NaOCl. To assess if changes in S. Typhimurium after exposure to NaOCl were due to a cross-regulation, as in Escherichia coli, we evaluated the expression of marA, soxS, and rob in the different genetic backgrounds. The positive regulation observed in the wild-type strain of marA and soxS was retained in the Δrob strain. As in the wild-type strain, rob was down-regulated in the ΔmarA and ΔsoxS treated with NaOCl; however, this effect was decreased. Since rob was down-regulated by both factors, we generated a ΔmarA ΔsoxS strain finding that the negative regulation was abolished, confirming our hypothesis. Electrophoretic mobility shift assays using MarA and SoxS confirmed an interaction with the promoter of rob.
... At 15 °C and a pH level of 6, the Cl2 fraction is in the 10 -5 magnitude [42]. The relative concentration of Cl2 is about 5 % at room temperature, indicating three order of magnitude increment by the increase of the temperature with 10 °C [43][44][45]. Considering the 60 °C of exposure temperature at 6.8 pH, Cl2 might be present in a significant amount. The increased amount of Cl2 gas can serve as an explanation for the AO consumption in a few hundred microns of depth [13,14] without the significant material embrittlement of this layer (see Fig. 2 a). ...
Conference Paper
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SHORT SUMMARY (One paragraph, ~6 sentences) Accelerated aging experiments by the immersion of a commercial polyethylene (PE) pipe grade in 10 ppm of chlorine dioxide (ClO2) and in 100 ppm of hypochlorite (HOCl) solution at 60 °C were performed. An additional immersion test was conducted in 1 ppm of ClO2 at 40 °C. The exposure parameters were continuously controlled especially the disinfectant concentration during the aging of 1 mm thick tensile specimens. Analysis techniques such as SEM, tensile test, FTIR and DSC-OOT, revealed significant differences in the aging mechanism caused by the two disinfectants. On the one hand, the presence of ClO2 induced an apparent parallel material embrittlement with the consumption of active stabilizers, displaying surface cracks and a few hundred microns thick degraded surface layer. On the other hand, the results of HOCl exposure indicate an accelerated auto-oxidative degradation, displaying an etched-like, rough surface characteristic with numerous cavities, without the appearance of distinct surface cracks and degraded layer. ABSTRACT Chlorine dioxide (ClO2) and hypochlorite (HOCl) are the most used oxidizing agents for secondary drinking water disinfection due to their high effectivity against pathogenic microorganisms. Considering the strong oxidative nature of these disinfectants, accelerated antioxidant consumption and material degradation can be expected in the
... The standard reaction equation between hypochlorite and hydrogen is NaOCl + H 2 O 2 → O 2 + NaCl + H 2 O in which the oxygen is initially produced in singlet form. 50 This highly exothermic reaction under normal conditions is not reversible. Enzymes such as myoperoxidase in a neutrophil can reverse the reaction to produce HOCl because they lower the activation ener-gy substantially. ...
Article
Experiments were performed to identify the reactive intermediate(s) involved in the degradation of several vinyl polymers upon exposure to chlorinated water. The potential intermediates of concern are Cl2, HClO, and singlet molecular oxygen, O2(a1Δg), all of which exist in chlorinated water and whose concentration profiles are pH-dependent. The degradation of polystyrene and poly(styrene-co-butadiene) films was monitored in a variety of pH-dependent experiments using FTIR spectroscopy. Data obtained indicate that Cl2 is the principle reactive intermediate that initiates polymer degradation, and that singlet oxygen does not play a significant role under these conditions. Moreover, poly(styrene-co-butadiene) samples were significantly more susceptible to the effects of chlorinated water than were polystyrene samples and, thus, identify olefinic residues as an important reactive functional group under these conditions. Data obtained also indicate that the thermal history of the sample is important. Specifically, upon immersion in chlorinated water, samples that had been exposed to high temperatures during processing and/or that had been annealed for longer periods of time degraded at a much faster rate than did samples that had only minimal exposure to high temperatures. This effect was particularly pronounced with the poly(styrene-co-butadiene) samples. These results are important with respect to the development of polymers that can better resist exposure to water that has been chlorinated to kill bacteria (e.g., drinking water).
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Experiments were performed in an attempt to identify the reactive intermediate(s) involved in the degradation of a polyamide, Nylon 66, in chlorinated water. According to previous studies, N-chlorination is certainly one reaction that ultimately contributes to polyamide degradation. In this case, the intermediates involved could either be Cl 2 or HClO. Available information also indicates that, for many polymers, singlet molecular oxygen (a 1Δ g), chemically generated from HClO, could likewise be involved as an intermediate in a degradation reaction. Thus, tests were undertaken to specifically address this latter issue with respect to polyamide degradation. The degradation of Nylon 66 was monitored under a variety of conditions by FT-IR spectroscopy. The rate of degradation was pH-dependent, and degradation was most pronounced at pH < 5. Characteristic tests for the intermediacy of singlet oxygen, however, were negative. Rather, the data strongly pointed to Cl 2 as the key intermediate in the degradation. The presence of compounds capable of being oxidized by Cl 2 arrested the degradation reaction. These results should be pertinent in an attempt to stabilize polymers exposed, e.g., to water that has been chlorinated to kill bacteria (i.e., drinking water).
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Selection for carotenogenesis in Phaffia rhodozyma was achieved by exposure of yeast strains to dark chemical reactions that generate singlet oxygen. Incubation of a mixture of P. rhodozyma strains containing varying levels of carotenoids in hypochlorous acid or hydrogen peroxide resulted in weak selection for pigmented strains. However, the combination of hydrogen peroxide and hypochlorous acid was strongly selective for carotenogenesis and gave a monoculture of a carotenoid-hyperproducer. Exposure of the yeast to ozone for 10 to 20 min also selected for a hyperproducing strain. These selections were relieved by 1,4-diazabicyclo(2.2.2)-octane, a specific quencher of singlet oxygen or by L-ascorbic acid. Continuous growth of P. rhodozyma on agar plates in an ozone/air atmosphere for 5 d decreased astaxanthin and total carotenoid levels and increased the levels of carotenoid biosynthetic intermediates. Repeated rounds of random mutagenesis followed by ozone exposure yielded mutant strains with higher pigmentation than control cultures. Our results support the hypothesis that a primary function of carotenoids in P. rhodozyma is to protect against singlet oxygen generated in the natural environment of the yeast and that a practical method for preventing strain degeneration during industrial fermentations may be achieved by generation of singlet oxygen using simple chemical supplements or by bubbling ozone through P. rhodozyma cultures during fermentation.
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Proprietary formulations of the amino acid L-histidine are under development as pharmaceutical agents because of the molecule’s antioxidant and anti-inflammatory properties. L-histidine has been well characterized in terms of probable dietary requirements, plasma and tissue concentrations, pharmacokinetics, metabolism and excretion, and medical conditions related to physiologic handling. Previous experience with histidine dosing in the literature is extensive, and both clinical and preclinical data suggest that histidine administration is very safe. L-histidine has been shown to scavenge both the hydroxyl radical and singlet oxygen (102) in many studies. These interactions may involve free histidine, small histidine-containing peptides such as carnosine, and histidine residues in proteins. Histidine appears to interfere with redox reactions involving iron and perhaps other metal ions and to interact directly with 102; the ability of histidine to scavenge 102, a toxic oxygen species of increasing concern, has been well established in the laboratory. Many recent studies have demonstrated the therapeutic efficacy of “pharmacologic” doses of L-histidine in animal models of inflammatory conditions, particularly gastrointestinal conditions and cardiac ischemia-reperfusion injury, and have specifically linked the anti-inflammatory capabilities of histidine to its ability to scavenge toxic oxygen species. The maintenance of histidine pools, therefore, may contribute to the body’s physiologic antioxidant capacity. Taken together, the data suggest that histidine supplementation could provide a safe, efficacious method to increase antioxidant protection.
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Nitroxyl radical TEMPO is found to catalyze the decomposition of sodium hypochlorite in an aqueous-alkali medium. The mechanism of NaOCl decomposition to form ClO· radical is proposed which involves protonated TEMPO, oxoammonium salt TEMPO+, and hydroxyl radical.
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The relationship between the susceptibility to rapid temperature drop induced leaf injury, i.e. “leaf spot”, and the antioxidant capacities of several Saintpaulia (African violet) cultivars was examined. Cultivars ‘Ritali’ and ‘Tamiko’, that are more susceptible to leaf spot caused by a rapid drop in leaf temperature from 30 to 15°C than are cultivars ‘Maui’ and ‘New Jersey’. The susceptible cultivars were also more susceptible to oxidative stress caused by H2O2 and active chlorine than the tolerant cultivars. Reduction of available chlorine, considered to be accelerated by antioxidants of leaf tissue, was rapid in ‘Maui’ and ‘New Jersey’. Activity of the antioxidant enzymes superoxide dismutase and catalase were higher in the leaves of ‘Maui’ and ‘New Jersey’ than in the susceptible cultivars. These findings show a correlation between leaf spot injury and antioxidant capacity in Saintpaulia leaves.
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An attempt is made to produce gas-phase singlet oxygen O2(a1Δg) in a liquid-liquid reaction between acidic hydrogen peroxide (AHP) and sodium hypochlorite (NaOCl). The attempt arises from the fact that basic hydrogen peroxide (BHP) has long been the prime source for producing singlet delta oxygen through its reaction with chlorine. However, BHP suffers from the defect of being unstable during storage. Exploratory experiments were performed in a centrifugal flow singlet oxygen generator (CF-SOG) with two streams of solutions, AHP and NaOCl, mixed in a slit nozzle and then injected into the arc-shaped concavity in the CF-SOG to form a rotating liquid flow with a remarkable centrifugal force. With the help of this centrifugal force, the product of the O2(1Δ) reaction was quickly separated from the liquid phase. The gas-phase O2(1Δ) was detected via the spectrum of O2(1Δ) cooperative dimolecular emission with a CCD spectrograph. Experimental results show that it is feasible to produce gas-phase O2(1Δ) from the AHP + NaOCl reaction, and the stronger the acidity, the more efficient the O2(1Δ) production. However, since in the AHP + NaOCl reaction, Cl2 unavoidably appears as a byproduct, its catalytic action on the decomposition of H2O2 into ground-state O2 remains a major obstacle to utilising the AHP + NaOCl reaction in producing gas-phase O2(1Δ). Qualitative interpretation shows that the AHP + NaOCl reaction is virtually the reaction of interaction of molecular H2O2 with molecular HOCl, its mechanism being analogous to that of reaction of BHP with Cl2, where HOOCl is the key intermediate. It is difficult to form the intermediate HOOCl via the H2O2 + NaOCl reaction in a basic medium, thus gas-phase O2(1Δ) cannot be obtained in appreciable quantities.
Article
Non-basic hydrogen peroxide was found to be very easy to react with Cl(2) to produce singlet oxygen O(2)(a(1)Δ(g)) (i.e. the molecular oxygen in its first electronic excited state) when an H(+) absorbent such as C(5)H(5)N, CH(3)COONH(4), HCOONH(4) or NH(4)F was added into H(2)O(2) aqueous solution, and the long concealed fact that molecular H(2)O(2) can react with Cl(2) to produce O(2)(a(1)Δ(g)) was then uncovered. It is only when an H(+) absorbent has provided a stronger base than H(2)O to absorb the H(+) produced during the reaction that O(2)(a(1)Δ(g)) can be produced.
Article
Experiments were performed to characterize events pertinent to the degradation of poly(1,4-phenylene sulfide) upon exposure to chlorinated water. Studies were specifically undertaken to identify the reactive species involved in the degradation reactions. Species of concern are Cl2, HOCl, and singlet molecular oxygen, O2(a1Δg), all of which exist in chlorinated water and whose concentration profiles are pH-dependent. Polymer degradation was monitored in pH-dependent experiments using FTIR spectroscopy. Data obtained indicate that Cl2 and HOCl are the principal reactive species that initiate degradation, and that the pertinent reactions occur over the pH range of ∼2–8. Reaction products include not just the sulfoxide and sulfone, but species derived from the chlorination of the aromatic ring and subsequent ring oxidation. Spatially-resolved FTIR mapping experiments illustrate how the progress of the reactions depends on the diffusion of reactive species from the surface of a given sample into the bulk. These results are important with respect to the development of polymers that can better resist exposure to water that has been chlorinated to kill bacteria.
Article
A mechanism for the production of singlet oxygen by acidification of hypochlorite in aqueous solution is proposed based on electron structure calculations. The mechanism involves two transition states and a peroxyhypochlorous acid intermediate. The calculations include six explicit water molecules to give some allowance for solvation of the produced electrolyte. The theoretical level is the density functional theory and the isodensity polarized continuum method. (c) 2007 Elsevier B.V. All rights reserved.
Article
Hypochlorous acid (HOCl), generated by myeloperoxidase from H2O2 and Cl-, is a strong chlorinating and oxidizing agent, playing an important role in host defense and inflammatory tissue injury. As several recent studies have shown that various oxidizing agents including peroxynitrite and singlet oxygen react readily with 8-oxo-7,8-dihydro-2 ' -deoxyguanosine (8-oxodGuo) to yield further oxidized products, we have studied the reaction of 8-oxodGuo with reagent HOCl and with a myeloperoxidase-H2O2-Cl- system. When I mM 8-oxodGuo was reacted with 0.5 mM HOCl at pH 7.4 and 37 degreesC, two major products were formed. They were identified as the diastereomers of spiroiminodihydantoin deoxyribonucleoside (dSph) on the basis of their identical ESI-MS and UV spectra and HPLC retention times with those of the major reaction products which were reported to be formed in other oxidation systems including potassium monopersulfate plus cobalt (II) chloride, peroxynitrite plus thiol, and type II photosensitization. Under the above reaction conditions, the yield of the diastereomers of dSph was 0.38 mM, with 0.57 mM 8-oxodGuo remaining unreacted. Since the presence of 50% D2O, 10 mM sodium azide, or 2% ethanol did not affect the yield of the products, involvement of singlet oxygen and hydroxyl radical in the formation of dSph from 8-oxodGuo with HOCl was ruled out. A 1000-fold excess of dGuo did not inhibit the reaction of 8-oxodGuo with HOCl, indicating that 8-oxodGuo reacts more readily than dGuo with HOCL dSph was also formed by reaction of 8-oxodGuo with myeloperoxidase in the presence of H2O2 and Cl-. Our results suggest that formation of dSph from 8-oxodGuo is mediated, possibly via an addition of Cl- to, or two-electron oxidation of 8-oxodGuo, with HOCl or the myeloperoxidase-H2O2-Cl- system.
Article
Two biologic elicitors prepared from panus conchatus and coriolus versicolor as well as two chemical elicitors were examined to determine their effects on the growth and astaxanthin formation by xanthophyllomyces dendrorhous. H2O2 accumulations in the fresh yeast cell after treatment by different elicitors were measured. The results showed that different elicitors could cause diversely stimulating effects. Among the fungal elicitors tested, the P. conchatus elicitor concentration of 30 mg I"1 promoted the biomass and astaxanthin yield very remarkably, resulting in 68.87±5.66 percent and 60.80±5.25 percent higher than the control, respectively. at the concentration of 30 mg I-1, C. versicolor elicitor stimulated the highest biomass and astaxanthin yield with 69.81 ±6.00 percent and 62.77±5.11 percent increases compared to the control, respectively. The titanium dioxide and cadmium chloride elicitors concentration of 0.12 and 0.16 mg I-1 gave the maximal increase in astaxanthin yeilds by 94.60±6.15 percent and 113.14±9.48 percent of the control, respectively. At 40 H after treatment the cadmium chloride concentration of 0.12 mg I-1 increased H2O2 accumulation in the wet cell most remarkably, resulting in 239.77±17.14 percent higher than the control. At the concentration of 0.16 mg I-1 at 40 H after treatment, titanium dioxide gave an increase in H 2O2 accumulation of the wet cell markedly by 225±15.91 percent of the control. Association between H2O 2 accumulation and biologic and chemical elicitors at the optimal dosages indicated that the biologic and chemical elicitors might stimulate biosynthesis of X. Dendrorhous by inducing abundant reactive oxygen species in the wet yeast cell.
Article
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Oxygen is a natural acceptor of electrons in the respiratory pathway of aerobic organisms and in many other biochemical reactions. Aerobic metabolism is always associated with the formation of reactive oxygen species (ROS). ROS may damage biomolecules but are also involved in regulatory functions of photosynthetic organisms. This review presents the main properties of ROS, the formation of ROS in the photosynthetic electron transport chain and in the stroma of chloroplasts, and ROS scavenging systems of thylakoid membrane and stroma. Effects of ROS on the photosynthetic apparatus and their roles in redox signaling are discussed.
Article
Water splitting to its elements, either by electrochemistry or by solar light, is among the most covered areas in nanostructured functional materials. This personal account article analyzes potential downstream translation problems and reviews alternative chemistries with a potential higher return. Liberation of oxygen for accepting the holes is a kinetically demanding half reaction afflicted with kinetic hindrances and high overpotentials, while at the same time no marketable value is created (atmospheric oxygen is free to use). In spite of exciting science created, application in real industrial set-ups is currently impossible, and possible funding promises to contribute to a sustainable society become a debt difficult to return. We discuss possible alternative targets of (photo)electrochemistry as entry points where chemical value products and technical oxidants are created, with partially greater ease, lower losses, and higher benefits.
Article
Production of bio-based functional polymers from woody biomass is becoming increasingly important for biorefineries. We studied the direct production of vanillin and vanillic acid, which are key monomer components for thermostable polymers, from a softwood Japanese cedar by an alkaline copper oxide–peroxide reaction using microwave (MW) and conventional heating (CH) reactors. MW heating at 180°C for 10 min produced vanillin and vanillic acid in yields nearly three times higher than those produced by conventional heating (10.1% vs 3.4%). The MW and CH experiments were precisely compared using the same heating conditions and the same reaction vessel. A cavity resonator (single-mode microwave) which can separate electric (E) and magnetic (H) fields were used for wood degradation. The results revealed that the reactions were accelerated by both fields with a slightly more prominent effect of electric fields (Emax>). The activation energy of experiments under CH, MW-Emax>, and MW-Hmax>. was calculated. The yield enhancement and decrease of activation energy unequivocally indicate the MW-sensitive character of this reaction. When hardwood (Eucalyptus globulus) was used as a feedstock, syringaldehyde and syringic acid were produced together with vanillin and vanillic acid, and the maximum yield of the monomers reached 11.4% based on the original wood weight under MW heating. This method was successfully scaled up by using a 1-L scale MW reactor to give vanillin and vanillic acid at a total yield of 8.5%.
Article
Since reactive oxygen species are involved in a range of pathologies, developing analytical tools for this group of molecules opens new vistas for biomedical diagnostics. Herein, we fabricate a porous silicon microcavity (pSiMC) functionalized with the luminescent singlet oxygen (¹O2) probe EuA ((Eu(III)-2,2',2''-(10-(2-((4-(2-((4-(2-((anthracen-9-ylmethyl)amino)ethyl)-1H-1,2,3-triazol-1-yl)amino)-2-oxoethyl)-2-oxo-1,2-dihydroquinolin-7-yl)amino)-2-oxoethyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetic acid) as proof-of-concept of an optical sensor for reactive oxygen species. We characterize each surface modification step of the pSiMC by means of FTIR and X-ray photoelectron spectroscopy as well as by determining the optical shifts of the resonance wavelength of the pSiMC. The luminescence signal upon detection of 1O2 on the EuA-modified pSiMC is enhanced ~2-fold compared to that of a single layer and detuned microcavity. The sensing performance of the EuA probe is improved significantly on the pSiMC compared to that in aqueous solution giving a limit of 1O2 detection of 3.7 x 10-8 M.
Chapter
The present review discusses three important aspects which are intimately related to human health at the molecular level. The first aspect is the formation of DNA lesions caused due to the reactions of DNA with certain free radicals known as reactive oxygen species (ROS) and reactive nitrogen oxide species (RNOS). Some of these free radicals are constantly formed in biological systems during the metabolic activities while others can be ascribed to the exposure to radiation or pollution. These species react with DNA bases, particularly guanine, leading to base misparing, mutation and several diseases including cancer. The mechanisms of reactions of certain ROS and RNOS with the DNA bases, particularly guanine or its modifications are discussed. The second aspect discussed here is the role of anti-oxidants some of which are present inside biological systems while others can be taken from external sources as food supplements. Certain endogenous anti-oxidants present in biological systems inhibit the formation of reactive free radicals while others, particularly those taken from outside, scavenge the same through appropriate chemical reactions. The molecular mechanisms of action of several anti-oxidants are discussed. The third aspect discussed here is the working of the complex and intelligent molecular machinery which is constantly active in biological systems and removes or repairs the damaged bases. Molecular mechanisms involved in some of these activities are reviewed. Details of recent theoretical studies on all the three aspects mentioned above are discussed.
Article
The physiological activity of osteoblasts is known to be closely related to increased intracellular Ca2+ activity ([Ca2+](i)) in osteoblasts. The cellular regulation of [Ca2+](i) in osteoblasts is mediated by Ca2+ movements associated with Ca2+ release from intracellular Ca2+ stores, and transmembrane Ca2+ influx via Na+-Ca2+ exchanger, and Ca2+ ATPase. Reactive oxygen species, such as H2O2, play an important role in the regulation of cellular functions, and act as signaling molecules or toxins in cells. In this study, we investigated the effects of H2O2 on cellular Ca2+ regulation in osteoblasts by measuring intracellular Ca2+ activities using cellular calcium imaging techniques. Osteoblasts were isolated from the femurs and tibias of neonatal rats, and cultured for 7 days. The cultured osteoblasts were loaded, with a Ca2+-sensitive fluorescent dye, Fura-2, and fluorescence images were monitored using a cooled CCD camera, and subsequently analyzed using image analyzing software. The results obtained are as follows: (1) The ostcoblasts with lower basal Ca2+ activities yielded a transient Ca2+ increase, a Ca2+ spike, while osteoblasts with higher basal Ca2+ activities showed a continuous increase in [Ca2+](i) leading to cell death. (2) Ca2+ spikes, generated after removing Na+ from superfusing solutions, were blocked by H2O2 and this was followed by a sustained increase in Ca2+ activity. (3) ATP- induced Ca2+ spikes were inhibited by pretreating with H2O2 and this was followed by a continuous increase of [Ca2+](i). When cells were pretreated with the exogenous nitric oxide (NO) donor S-Nitroso-N-acetylpenicilance (SNAP, 50,muM), treatments of ATP (1 mM) induced a Ca2+ spike-like increase, but [Ca2+](i) did not return to the basal level. (4) The expression of inositol-1,4,5-triphosphate receptor (IP3R) was enhanced by H2O2. Our results suggest that H2O2 modulates intracellular Ca2+ activity in osteoblasts by increasing Ca2+ release from the intracellular Ca2+ stores.
Thesis
Während der letzten Dekade neurobiologischer Forschung wurde deutlich, dass inflammatorische Vorgänge in einem Netwerk nicht-neuronaler und neuronale Zellen wesentlich zur Entstehung und zur Progredienz einiger wichtiger neurodegenerativer Erkrankungen beitragen. Therapeutische Ansätze sollten daher auch auf die Protektion initial überlebender Neurone vor dieser sekundären inflammatorischen Schädigung zielen. Ein wesentlicher Bestandteil dieser sekundären Schädigung besteht aus der Migration von Makrophagen und Mikrogliazellen in die Regionen neuronaler Schädigung, wo sie grosse Mengen an toxischen Zytokinen und Sauerstoffradikalen freisetzen. In einer Makrophagen-ähnlichen Zelllinie, sowie in phagozytierenden Mikrogliazellen wurde eine nukleäres proteolytisches System identifiziert, dass in der Lage war, oxidativ geschädigte Kernproteine zu erkennen und abzubauen. Im Gegensatz zu dem bisherigen Konzept relativer Langlebigkeit der Histonproteine, wurde diese nach oxidativer Schädigung innerhalb von Minuten abgebaut und vom Chromatin entfernt. Dieser schnelle Abbau war von der nicht-kovalenten Interaktion der automodifizierten Poly(ADP-Ribose)-Polymerase-1 (PARP-1) mit dem 20S Proteasom abhängig. Die PARP-1 wurde somit als ein Signalmolekül zwischen dem Chromatinschaden und der Einleitung einer protektiven Zellantwort charakterisiert, die Mikrogliazellen das Überleben ihres eigenen Aktivierungszustandes ermöglicht. Es zeigte sich, dass dieses PARP-Proteasom-System in Abhängigkeit vom Differenzierungsgrad Makrophagen-ähnlicher Zellen abhängig ist und auch funktionell in die Chemotherapieresistenz humaner Leukämiezellen involviert ist. Darüberhinaus regulierte die PARP-1 auch die Expression des Integrins CD11a durch Interaktion mit dem translozierten NF-kappaB und HMG-I(Y) und dadurch die Migration von Mikrogliazellen zum Ort der neuronalen Schädigung. Diese Ergebnisse machem die PARP-1 zu einem potentiellen Ziel therapeutischer Interventionen zur Verhinderung der destruktiven Migration von Mikrogliazellen, womit eine Protektion initial überlebender Neurone vor weiterer inflammatorischer Schädigung erreicht werden könnte.
Article
The chlorine used as disinfectant in tap water degrades most materials, including polyethylene. The most adequate (functional) test method, the pressure test, is complicated and expensive because the chlorinated aqueous media (Cl2 or ClO2 in water) are unstable and they undergo reactions that are dependent on the pH. A new method which assesses the protection efficiency of phenolic antioxidants in polyolefins was developed. The method uses a liquid hydrocarbon analogue, squalane, in which antioxidants are dissolved. The organic phase was dispersed in the aqueous chlorinated phase (containing 10ppm of either Cl2 or ClO2; pH=6.8) at 70°C by intense stirring. The depletion of antioxidant (Irganox 1010) was monitored by standard DSC determination of the oxidation induction time. It was shown that 300min of exposure was sufficient to obtain useful data.
Chapter
Singlet oxygen (1O2) is produced in the environment almost exclusively by photochemical pathways. Although it can be detected in many environmental compartments, its potential roles in chemical reactions under environmental conditions are not completely understood. For example, in the atmosphere, it is formed at lower elevations (1O2 participates in emission processes that contribute to the airglow, but in the stratosphere and troposphere its importance appears to be negligible. In natural surface waters, it is formed with about 1% efficiency from dissolved humic materials, but its deactivation by water molecules is so rapid that very few chemical reactions are able to compete. Its steady-state concentrations in most natural waters appear to center around 10-13 M. In water bodies polluted by light-absorbing chemicals such as dyestuffs, it is possible that it might be somewhat more important. In hydrophobic environments such as aquatic surface layers, especially those containing aromatic petroleum derivatives, lO2 might play a quite significant role due to its increased concentration and lifetime. Some solid phases, such as plant, soil, and mineral surfaces, could be sites where lO2 is formed, but little is known about its importance; and similar statements could be made about 1O2 in living cells, despite many decades of investigation of the mechanisms of “photodynamic toxicity.”
Article
Reactive oxygen species are formed in the body by several natural processes and by induced oxidative stress. The reactive oxygen species may react with the various biomolecules of the body, including proteins. In order to assess the impact of oxidative damage to proteins, we have tried to identify oxidized amino acids in blood proteins which might serve as biomarkers of oxidative damage. When oxidative damage is induced into bovine serum albumin by metal-catalysed oxidation systems, the aldehyde groups formed can be derivatized by fluoresceinamine (FINH2). Following acid hydrolysis of FINH2-derivatized protein, two major oxidation products, γ-glutamyl semialdehyde (GGS) and 2-amino-adipic semialdehyde (AAS), were found and identified by HPLC and MS. Isolation and identification of oxidized amino acids from homopolymers (poly-Arg, -Pro, -Lys, -Trp or -Leu) confirmed that GGS can originate from Arg or Pro, while AAS is an oxidation product of Lys. When oxidative stress was induced in rats by treatments with t-butyl hydroperoxide or acrolein, rat plasma protein levels of GGS and AAS were found to be significantly higher compared with control rats. The AAS-content in serum albumin or in total plasma proteins collected from eight different mammalian species was found to be inversely proportional to their maximum lifespan potential. The content of AAS in plasma proteins of untreated adult rats showed a positive correlation with the age of the rat. In young rats a negative correlation with age was found for both GGS and AAS. We conclude that GGS or AAS may be useful novel biomarkers of oxidative damage to proteins in vivo.
Article
Plasmonic photocatalysts of the form Ag@AgCl/rGO were synthesized by a deposition–precipitation–photoreduction method and the composite materials characterized using Raman spectroscopy, attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The as-prepared plasmonic photocatalysts exhibited enhanced photoactivity for the degradation of formic acid (FA) under visible light irradiation, however, both the Ag@AgCl and the graphene oxide support underwent continuous transformation during photolysis. The high activity was attributed principally to the ability of the composite Ag0/AgCl system to absorb light in the visible wavelength region and to retard the recombination of electron–hole pairs. While the presence of the reduced graphene oxide (rGO) support may also have contributed to a reduction in rate of electron–hole pair recombination, the effect was not found to be particularly significant. HO trapping experiments with phthalhydrazide as well as the influence of t-butanol on FA degradation suggested that either photo-formed holes or surface chlorine atoms were the main reactive species inducing degradation of FA under visible light irradiation. Total free chlorine, but not hydrogen peroxide, could be detected by N,N-diethyl-p-phenylenediamine (DPD) spectrophotometry suggesting that while photogenerated holes decay via reaction with chloride ions, photogenerated electrons decay via a pathway other than reaction with oxygen. Possible reaction mechanisms that conform to these observations are discussed. Although this system has potential for the oxidative degradation of contaminants, greater understanding of the factors that promote excessive Ag(I) reduction, concomitant formation of Ag(0) and eventual deactivation of the catalyst is needed.
Article
Oxidative stress is linked to serious diseases and longevity of aerobic cells, including those in humans, which makes the topic of special interest. In this article the basic chemistry involved in the formation of free radicals and other reactive oxygen and nitrogen species will be reviewed along with an account of the major reaction types they induce. In addition, it will be shown how the technique of computational chemistry may provide detailed information on specific reaction channels of importance in oxidative stress. Specifically, preliminary data for a mechanism for the NO mediated production of HO radicals in the absence of transition metal catalysts will be presented.
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Chlorine species used as disinfectants in tap water have a deteriorating effect on many materials including polyethylene. There are only very few scientific reports on the effect on polyethylene pipes of water containing chlorine dioxide. Medium-density polyethylene pipes stabilized with hindered phenol and phosphite antioxidants were pressure tested with water containing 4 ppm chlorine dioxide at 90 °C and pH = 6.8 as internal medium. The stabilizers were rapidly consumed towards the inner pipe wall; the rate of consumption was four times greater than in chlorinated water (4 ppm, pH = 6.8) at the same temperature. The depletion of stabilizer occurred far into the pipe wall. A supplementary study on a polymer analogue (squalane) containing the same stabilizer package showed that the consumption of the phenolic antioxidant was 2.5 times faster when exposed water containing chlorine dioxide than on exposure to chlorinated water. The subsequent polymer degradation was an immediate surface reaction. It was confirmed by differential scanning calorimetry, infrared spectroscopy and size exclusion chromatography that in the surface layer which came into contact with the oxidising medium, the amorphous component of the polymer was heavily oxidized leaving a highly crystalline powder with many carboxylic acid chain ends in extended and once-folded chains. Scanning electron microscopy showed that propagation of cracks through the pipe wall was assisted by polymer degradation.
Article
The presence of the cholesterol ozonolysis products, 3beta-hydroxy-5-oxo-5,6-secocholestan-6-al (atheronal-A) and its aldolization product 3beta-hydroxy-5beta-hydroxy-B-norcholestane-6beta-carboxaldehyde (atheronal-B) in human atherosclerotic tissues was recently reported as evidence for the generation of ozone by activated human neutrophils. However, the mechanism for the formation of atheronals in atherosclerotic tissues is unknown. In this study, we found that atheronals were formed by the reaction of cholesterol with human myeloperoxidase (MPO) in the presence of its substrates H(2)O(2) and Cl(-). The omission of either H(2)O(2) or Cl(-) from the MPO-H(2)O(2)-Cl(-) system resulted in a significant reduction in yields. The formation of atheronals by the MPO-H(2)O(2)-Cl(-) system was inhibited by an inhibitor of MPO and scavengers of reactive oxygen species such as sodium azide, methionine, beta-carotene, and vinylbenzoic acid. Our results suggest that MPO produces atheronals at least partly through an ozone-free mechanism, via the reaction of cholesterol with singlet oxygen generated from HOCl and H(2)O(2).
Article
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Myeloperoxidase, H2O2, and a halide form a potent anti-microbial system which is operative in the polymorphonuclear leukocyte (PMN). The formation of singlet oxygen (1O2) by this system is suggested by (a) the conversion of 2,5-diphenylfuran to its specific singlet oxygen product cis-dibenzoylethylene (cis-DBE); (b) the inhibition of this reaction by the 1O2 quenchers β-carotene, bilirubin, histidine, and 1,4-diazabicyclo[2,2,2]octane (DABCO); and (c) the stimulation of conversion by D2O, which prolongs the lifetime of 1O2 in solution. Diphenylfuran conversion by the myeloperoxidase system has a pH optimum of 4.5 and an optimum H2O2 concentration of 30 μM and the halides vary in effectiveness in the order Br- > Cl- > I-. Reagent H2O2 could be replaced by the H2O2-generating system, glucose + glucose oxidase. Hypochlorous acid, which is formed by the myeloperoxidase/H2O2/chloride system, also converts diphenylfuran to cis-DBE. As with the myeloperoxidase system, this conversion has an acid pH optimum, is inhibited by 1O2 quenchers, and is stimulated by D2O. Diphenylfuran coversion by HOCl is increased by chloride, but not by H2O2, in the concentrations employed in the myeloperoxidase system. Our studies suggest that 1O2 is formed by the myeloperoxidase/H2O2/chloride system and that the mechanism involves the initial oxidation of chloride to HOCl and the subsequent decomposition of HOCl, particularly in the presence of excess chloride, to form 1O2. The singlet oxygen so formed may participate in the microbicidal activity of the isolated myeloperoxidase system and of the intact PMN.
Article
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Individual epidemiological investigations into the association between chlorination by-products in drinking water and cancer have been suggestive but inconclusive. Enough studies exist to provide the basis for a meaningful meta-analysis. An extensive literature search was performed to identify pertinent case-control studies and cohort studies. Consumption of chlorinated water, surface water, or water with high levels of chloroform was used as a surrogate for exposure to chlorination by-products. Relative risk estimates were abstracted from the individual studies and pooled. A simple meta-analysis of all cancer sites yielded a relative risk estimate for exposure to chlorination by-products of 1.15 (95% CI: 1.09, 1.20). Pooled relative risk estimates for organ-specific neoplasms were 1.21 (95% CI: 1.09, 1.34) for bladder cancer and 1.38 (95% CI: 1.01, 1.87) for rectal cancer. When studies that adjusted for potential confounders were pooled separately, estimates of relative risks did not change substantially. The results of this meta-analysis suggest a positive association between consumption of chlorination by-products in drinking water and bladder and rectal cancer in humans.
Article
A method of calculating the matrix components, corresponding to the continuous absorption of light by diatomic molecules in various vibrational and rotational levels of the lower state, is described and applied to the calculation of the absorption of Cl2 gas at various temperatures. The theory shows that the absorption from a single vibrational level is practically independent of temperature, and that the temperature effect is due to the changing distribution of the absorbing molecules among the various levels. Assuming the Morse function to be approximately correct for the potential energy of the lower state, the theory enables one to calculate the form of the upper potential energy curve. The matrix component of the electric moment corresponding to the absorption from the lower state has been calculated for Cl2 and found to correspond to the displacement of one electronic charge through 0.016A.
Article
Direct spectroscopic observation of (0,0) at 1.27 μm and (0, 1) at 1.58 μm of 1Δg→ 3Σg− transitions of molecular oxygen in H2O2-OCl− chemiluminescence reaction and in dye-sensitized fluorocarbon solutions at room temperature is reported. Observation of these weak and ultraweak emissions was accomplished by developing an extremely sensitive near IR spectrophotometer using a thermoelectrically cooled PbS detector, optimized optics, and a boxcar integrator, as a data processor.
Chapter
Introduction Techniques Bimolecular processes Conclusions
Article
4- to more than 10-fold acceleration of the Hill reaction (electron acceptor: indophenol dyes, ferricyanide, FMN, etc.) by Cl− is consistently observed over a wide range of pH (5.7–8.3) when EDTA-uncoupled chloroplasts are used as experimental material. Using such highly Cl−-sensitive chloroplasts the effect of Cl− was examined on the photooxidation of reducing agents which are capable of donating electrons to Photosystem II. No Cl− effect is observed on the photooxidation of hydroxylamine (at substrate level with indophenol dye as electron acceptor) or of ascorbate (FMN as acceptor). These observations strongly suggest that Cl− acts near the water-splitting end of Photosystem II.High concentrations of ammonia and methylamine, like low concentrations of hydroxylamine, block water splitting on the oxidizing side of Photosystem II. Apparently the unprotonated forms of simple amines act as a specific inhibitor at a point near the site of Cl− involvement.Upon removal of Cl− the steady-state fluorescence yield of chloroplasts is markedly and reversibly depressed. However, the addition of a substrate level of hydroxylamine obliterates the Cl− effect on fluorescence and the yield becomes higher than in the presence of Cl− alone. These observations are discussed in connection with the site of Cl− involvement and with the current model of the chloroplast fluorescence quenching mechanism.
Article
Singlet oxygen is a major oxidative species that can be generated by numerous biological processes such as photosensitization. This oxidant can react with deoxyguanosine and with guanine in deoxyribonucleic acid (DNA) leading to the induction of at least four different reaction products such as 4,8-dihydro-4-hydroxy-8-oxodeoxyguanosine and 7,8-dihydro-8-oxodeoxyguanosine. The induction of true single-stranded breaks in the oxidated DNA is still a matter of controversy and is not yet clearly established. This paper focuses mainly on several biological consequences which can be associated with the induction of DNA lesions by singlet oxygen. Oxidated DNA loses its transformation efficiency probably because unrepaired lesions can partially inhibit DNA replication. Mutagenesis is one of the main effects induced by guanine oxidation products. Molecular analysis of mutated genes reveals that G to T transversions are the most frequent mutations; these are probably introduced in DNA by misincorporation of deoxyadenosine monophosphate (dAMP) opposite to the lesion. Efficient repair of these oxidated guanine residues can take place via specific glycosylase, endonuclease or the SOS network. However, the data concerning the toxicity of singlet oxygen for eukaryotic cells are not frequent enough in the literature to draw a clear picture of the effects of this activated species in several biologically revelant phenomena.
Article
Populations of fibroblast-like cells of corneal stroma, heart ventricle, and back skin of day-14 embryonic chicks were grown in vitro as primary and secondary cultures and were found to differ from one another by several criteria. Such cells were obtained from tissues either directly (cornea) by dissection or indirectly (heart and skin) by the rapid adhesion of the fibroblast-like cells to glass and plastic substrata. Individual fibroblast-like cells of cornea and heart were distinguishable from one another during their first 24--48 h in vitro. The morphologies of the individual cels of these 2 populations became indistinguishable during logarithmic growth, although each could be distinguished from individual fibroblast-like cells of skin. When the cultures reached saturation, corneal cells formed a monolayer of randomly oriented polygonal cells; skin cells formed a monolayer of long, narrow, ragged cells in parallel arrays with occasional double-layering; and heart cells formed multilayers of criss-crossed cells whose broad, smooth outlines were in parallel array in each layer. Saturation densities of the 3 fibroblast-like populations were different: heart greater than skin greater than cornea. By 3 methods of assay the cells were found to be differentially sensitive to treatment with trypsin and EDTA, and to EDTA alone, heart cells consistently being the least sensitive. Taken together, these data suggest that fibroblast-like cell populations isolated from different tissues of a single organism are different from one another and thus may behave differently from one another during in vitro studies.
Article
Singlet oxygen is a major oxidative species that can be generated by numerous biological processes such as photosensitization. This oxidant can react with deoxyguanosine and with guanine in deoxyribonucleic acid (DNA) leading to the induction of at least four different reaction products such as 4,8-dihydro-4-hydroxy-8-oxodeoxyguanosine and 7,8-dihydro-8-oxodeoxyguanosine. The induction of true single-stranded breaks in the oxidated DNA is still a matter of controversy and is not yet clearly established. This paper focuses mainly on several biological consequences which can be associated with the induction of DNA lesions by singlet oxygen. Oxidated DNA loses its transformation efficiency probably because unrepaired lesions can partially inhibit DNA replication. Mutagenesis is one of the main effects induced by guanine oxidation products. Molecular analysis of mutated genes reveals that G to T transversions are the most frequent mutations; these are probably introduced in DNA by misincorporation of deoxyadenosine monophosphate (dAMP) opposite to the lesion. Efficient repair of these oxidated guanine residues can take place via specific glycosylase, endonuclease or the SOS network. However, the data concerning the toxicity of singlet oxygen for eukaryotic cells are not frequent enough in the literature to draw a clear picture of the effects of this activated species in several biologically revelant phenomena.
Article
Hypochlorite is a reactive oxidant formed as an end product of the respiratory burst in activated neutrophils. It is responsible for killing bacteria and has been implicated in neutrophil-mediated tissue injury associated with the inflammatory process. Although hypochlorite is a potent cytotoxic agent, the primary mechanism by which it exerts its effect is unclear. This review examines evidence that the primary event in hypochlorite cytotoxicity is the loss of adenine nucleotides from the target cell. This loss appears to be mediated by the formation of adenine nucleotide chloramines which are reactive intermediates with a free radical character and are capable of forming stable ligands with proteins and nucleic acids.
Article
A covalently closed, circular, supercoiled plasmid was exposed to singlet oxygen by a separated-surface sensitizer. For each exposure, the quantity of single oxygen entering the DNA target solution was estimated by its oxidation of histidine. After singlet oxygen exposure, some DNA samples were treated to disclose occult lesions. Agarose gel electrophoresis was then used to resolve the unrelaxed supercoils from the relaxed circular and linear species, and all bands were quantitated fluorometrically. Exposure of supercoiled plasmid DNA to singlet oxygen induced frank DNA strand breaks, alkali-labile sites (pH 12.5, 90 degrees C, 30 min), and piperidine-labile sites (0.4 M, 60 degrees C, 30 min), all in a dose-dependent manner. Yields of alkali-labile and piperidine-labile sites ranged from one to four times the frank strand break yield. Replacement of buffered H2O by buffered D2O as the DNA solvent for singlet oxygen exposures increased DNA lesion yields by a factor of 2.6 (averaged over lesion classes). Our data for the detection of frank strand breaks is at variance with published results from studies in which singlet oxygen was derived from a thermolabile endoperoxide dissolved in the DNA solution.
Article
Damage of plasmid and bacteriophage DNA inflicted by singlet molecular oxygen (1O2) includes loss of the biological activity measured as transforming capacity in E. coli and single-strand break formation. Three different sources of 1O2 were employed: (i) photosensitization with Rose bengal immobilized on a glass plate physically separated from the solution; (ii) thermal decomposition of the water-soluble endoperoxide 3,3'-(1,4-naphthylidene) dipropionate (NDPO2); and (iii) microwave discharge. Loss of transforming activity was documented after exposing bacteriophage M13 DNA to 1O2 generated by photosensitization employing immobilized Rose bengal, and with bacteriophage luminal diameter X174 DNA, using the thermodissociable endoperoxide (NDPO2) as a source of 1O2. These findings are in agreement with experiments in which plasmid DNA pBR322 was exposed to a gas stream of 1O2 generated by microwave discharge. The effects of 1O2 quenchers and of 2H2O indicate 1O2 to be the species responsible. Strand-break formation in pBR322 and luminal diameter X174, measured as an increase of the open circular form at the expense of the closed circular supercoiled form, was observed without alkaline treatment after exposing the DNA to 1O2, using either agarose gel electrophoresis or sucrose gradient separation. The effect of quenchers and 2H2O indicate the involvement of 1O2 in DNA damage. We conclude that singlet oxygen can cause loss of biological activity and DNA strand breakage.
Article
4- to more than 10-fold acceleration of the Hill reaction (electron acceptor: indophenol dyes, ferricyanide, FMN, etc.) by Cl- is consistently observed over a wide range of pH (5.7-8.3) when EDTA-uncoupled chloroplasts are used as experimental material. Using such highly Cl--sensitive chloroplasts the effect of Cl- was examined on the photooxidation of reducing agents which are capable of donating electrons to Photosystem II. No Cl- effect is observed on the photooxidation of hydroxylamine (at substrate level with indophenol dye as electron acceptor) or of ascorbate (FMN as acceptor). These observations strongly suggest that Cl- acts near the water-splitting end of Photosystem II. High concentrations of ammonia and methylamine, like low concentrations of hydroxylamine, block water splitting on the oxidizing side of Photosystem II. Apparently the unprotonated forms of simple amines act as a specific inhibitor at a point near the site of Cl- involvement. Upon removal of Cl- the steady-state fluorescence yield of chloroplasts is markedly and reversibly depressed. However, the addition of a substrate level of hydroxylamine obliterates the Cl- effect on fluorescence and the yield becomes higher than in the presence of Cl- alone. These observations are discussed in connection with the site of Cl- involvement and with the current model of the chloroplast fluorescence quenching mechanism.
Article
Myeloperoxidase in micromolar concentrations reacting with half-millimolar stock solution H2O2 in acetate buffer containing KBr and in 50% D2O (pH + pD = 4.5) at 298 K is shown to generate singlet delta molecular oxygen efficiently. The near infrared electronic emission of singlet oxygen at 1268 nm is detected directly by novel ultrasensitive IR spectrophotometer equipment. The quantum efficiency of singlet oxygen generation by the MPO X Br- X H2O2 reaction is shown to be comparable with that of the standard chemical reaction OCl- X H2O2 at identical peroxide concentrations.
Article
The direct observation of dye-photosensitized 1268-nm emission of the (1)Delta(g) --> (3)Sigma(g) transition of molecular oxygen in liquid solution at room temperature is reported. Singlet oxygen was photosensitized by UV excitation of perfluorobenzophenone in fluorocarbon solvent, by 3,4-benzpyrene and hematoporphyrin in carbon tetrachloride, and by methylene blue in water. Also reported is the development of an extremely sensitive near-infrared spectrophotometer that uses a thermoelectrically cooled lead sulfide detector, optimized optics, and a boxcar integrator as a data processor.
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