Ozone-induced Oxidation Research Articles

Determination of Calcium Isotopes Using Inductive Coupled Plasma-Tandem Mass Spectrometry with Ozone-Induced Oxidation.

In this study, we propose a new method for determination of calcium (Ca) isotopes using inductive coupled plasma-tandem mass spectrometry (ICP-MS/MS). The most abundant isotope of Ca, 40Ca, has a spectrum identical with that of argon (Ar), which is often used as the carrier gas in ICP-MS analysis. The detection capability for 40Ca is thus significantly reduced in the presence of 40Ar. To avoid interference from 40Ar during the 40Ca measurements, ozone (O3) was used as the reaction gas in the ICP-MS/MS analysis. The reaction of Ca+ with O3 in the collision cell preferentially produced CaO3+. In contrast, the reaction between Ar+ and O3 produced ArO+, which further reacted with the oxidized O3 to produce Ar+. Because Ar+ does not produced ArO3+ as the main product of the reaction with O3, the measurement of Ca+ as CaO3 via O3-induced oxidation resulted in considerably less interference from Ar+. The detailed mechanism of CaO3+ formation was investigated via quantum chemistry calculations by using density functional theory. The interaction between Ca+ and O3 yielded CaO3+, which immediately dissociated into either Ca+ and O3 or CaO+ and O2 because the pressure in the collision cell was approximately 1 Pa in the MS/MS experiments. Consequently, CaO3+ was formed by the consecutive reaction of Ca+ with O3, with CaO+ and CaO2+ as intermediates. The present method achieved the detection of less abundant Ca isotopes in certified reference materials such as 43Ca, 44Ca, 46Ca, and 48Ca, thereby allowing the determination of Ca isotopes with high sensitivity.

Quantitative Evaluation on the Degradation Process of the Pulmonary Surfactant Monolayer When Exposed to Low-Level Ozone of Ambient Environment.

Ozone is a potent environmental oxidant with high chemical reactivity and is present in the ambient environment at a low level of a few tens of ppb. However, only limited information is known about low-level ozone's influence on the respiratory system. In the present study, we systematically investigated the degradation of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), which is one of the major components of the pulmonary surfactant (PS), enabling breath function of the lung exposed to low ambient-level ozone (40 ± 10 ppb). Using the liquid chromatography-mass spectrometry technique combined with the Langmuir-Blodgett approach, we first tracked the degradation process of POPC molecules by determining the degradation products during exposure to the ambient environment. As a result, we found that the POPC molecules can be readily degraded from the C═C moiety in 45 min, yielding an aldehyde-type product of 1-palmitoyl-2-(9'-oxo-nonanoyl)-sn-glycero-3-phosphocholine (POnPC) and a trace amount of an acid-type one of 1-palmitoyl-2-azelaoyl-sn-glycero-3-phosphocholine (PAzPC), as well as a pair of secondary ozonide (SOZ) isomers. Furthermore, with prolonged exposure, the SOZ stayed constant but the yield of PAzPC significantly increased with the decrease in POnPC. The low-level ozone-induced oxidation mechanisms for unsaturated lipids are discussed based on the quantitative analyses of these experimental observations. The present results demonstrate that the ground-level ozone is strong enough to induce dramatic oxidation damage to the unsaturated lipids of the PS. These oxidized species may trigger the lung's inflammatory response and be used as biomarkers for oxidative stress and inflammation.

Impact of ozone-induced oxidation on the textural, moisture, micro-rheology and structural properties of egg yolk gels

The impact of ozone-induced oxidation on the gel properties of egg yolk was investigated for the first time in this research. The textural properties, water-holding capacity, cooking loss rate and color of the chicken egg yolk gel (CEYG) were significantly improved after ozonation. The maximum hardness value (976.04 g) was reached at 20 min of ozonation and it was 134.92 g higher than that of the natural group. Additionally, the ozone-treated yolk showed an increase of 58.47% in carbonyl content and a decrease of 44.33% in free sulfhydryl groups. The results of low-field nuclear magnetic resonance indicated that ozone promoted the conversion of free water to non-flowing water in the CEYG. Scanning electron microscopy represented that the moderate ozone treatment resulted in a more regular, continuous and smooth network structure of the CEYG. These results provided a theoretical basis for the application of ozone to improve the performance of heat-induced CEYG.

Investigation of the ozone-induced oxidation of soot over LaMnO3 catalyst using O3/O2 temperature-programmed desorption experiments

Investigation of the ozone-induced oxidation of soot over LaMnO3 catalyst using O3/O2 temperature-programmed desorption experiments

Enhancement of Combustive Removal of Soot at Low Temperatures (~ 150 °C) Using Ozone as an Oxidant and Potassium-Substituted Lanthanum Manganite as a Catalyst

ABSTRACT Ozone (O3) is a strong oxidant, which is able to oxidize carbonaceous solid soot even at ambient temperature. In this study, we found that the ozone-induced oxidation of soot was noticeably enhanced in the range 100–150 °C when La1-x K x MnO3 (x = 0, 0.1, 0.25) was used as a catalyst. The oxidation was limited at T < 300 °C owing to the thermal instability of ozone, but during temperature-programmed oxidation of soot from 25 to 700 °C, more than 70% of the carbon was combusted at T < 300 °C. The O3-induced soot oxidation rate over LaMnO3 at 150 °C was comparable to the NO2 (and O2)-induced soot oxidation rates over LaMnO3 at 430 °C and Pt/γ-Al2O3 at 410 °C. The K-substitution degree (x) of La1-x K x MnO3 had little influence on the catalytic activity in ozone-induced soot oxidation, which is a reflection of the similarity of the substituted catalysts in the number of surface oxygen vacancies.

Oxidation-induced modifications of the catalytic subunits of plasma fibrin-stabilizing factor at the different stages of its activation identified by mass spectrometry

Plasma fibrin-stabilizing factor (pFXIII) is a heterotetrameric proenzyme composed of two catalytic A subunits (FXIII-A2) and two inhibitory/carrier B subunits (FXIII-B2). The main function of the protein is the formation of cross-links between the polypeptide chains of the fibrin clot. The conversion of pFXIII into the enzymatic form FXIII-A2* is a multistage process. Like many other blood plasma proteins, pFXIII is an oxidant-susceptible target. The influence of distinct sites susceptible to oxidation-mediated modifications on the changes in the structural-functional characteristics of the protein remains fully unexplored. For the first time, a set of the oxidation sites within FXIII-A2 under ozone-induced oxidation of pFXIII at different stages of its activation have been identified by mass spectrometry, and the extent as well as the chemical nature of these modifications have been explored. It was shown that the set of amino acid residues susceptible to oxidative attack and the degree of oxidation of these residues in FXIII-A2 of non-activated pFXIII, pFXIII activated by Ca2+ and fully activated pFXIII treated with thrombin and Ca2+ significantly differ. The obtained data enable one to postulate that in the process of the proenzyme conversion into FXIII-A2*, new earlier-unexposed amino acid residues become available for the oxidizer while some of the initially surface-exhibited residues are buried within the protein globule.

The strengthening role of D:D interactions in fibrin self-assembly under oxidation.

The effect on ozone-induced oxidation on the self-assembly of fibrin in the presence of fibrin-stabilizing factor FXIIIa of soluble cross-linked fibrin oligomers was studied in a medium containing moderate urea concentrations. It is established that fibrin oligomers were formed by the protofibrils cross-linked through γ-γ dimers and the fibrils additionally cross-linked by through α-polymers. The oxidation promoted both the accumulation of greater amounts of γ-γ dimers and the formation of protofibrils, fibrils, and their dissociation products emerging with increasing urea concentrations, which have a high molecular weight. It is concluded that the oxidation enhances the axial interactions between D-regions of fibrin molecules.

α-Tocopherol/Gallic Acid Cooperation in the Protection of Galactolipids Against Ozone-Induced Oxidation.

The protective ability of α-tocopherol (TOH) and gallic acid (GA) acting simultaneously at the moment of oxidizer application was evaluated by determination of galactolipid layers’ oxidation degree. Addition of GA resulted in a significant decrease of ozone-derived radicals shifting the threshold of lipid sensitivity by an amount approximately corresponding to the GA intake in bulk reaction with ozone. TOH presence in lipid layers results in a change of the role of GA which additionally may be involved in the reduction of tocopheroxyl radical formed during oxidation. This leads to a decrease in effectiveness of GA in diminishing the amount of ozone radicals. Such an effect was not observed for mixed layers containing galactolipid and pre-oxidized tocopherol where the ozone threshold level was associated with a stoichiometry of GA + O3 reaction. It was concluded that probably subsequent transformations of tocopheroxyl radical to less reactive forms prevent its reaction with GA the entire quantity of which is used for radicals scavenging. This result shows the role of time parameter in systems where substrates are engaged in various reactions taking place simultaneously. The inactivation of 1,1-diphenyl-2-picrylhydrazyl radical by studied antioxidants in homogeneous system confirmed observations made on the basis of lipid layer properties indicating their antagonistic action (at least at studied conditions). Formation of layers in post-oxidation situation did not depend whether tocopherol was oxidized during oxidation of lipid/tocopherol mixture or was introduced as pre-oxidized. This may be interpreted as indication that products of tocopherol oxidation may stabilize lipid layers.

Role of grain boundaries in tailoring electronic properties of polycrystalline graphene by chemical functionalization

Grain boundaries, inevitably present in chemical vapor deposited graphene, are expected to have considerable impact on the development of graphene-based hybrid materials with tailored material properties. We demonstrate here the critical role of polycrystallinity on the chemical functionalization of graphene comparing ozone-induced oxidation with remote plasma hydrogenation. We show that graphene oxidation and hydrogenation occur in two consecutive stages upon increasing defect density: an initial step in which surface-bound functional groups are generated, followed by the creation of vacancies. Remarkably, we find that hydrogenation yields homogeneously distributed defects while ozone-induced defects are preferentially accumulated at the grain boundaries eventually provoking local cracking of the structure. Supported by quantum simulations, our experimental findings reveal distinct electronic transport regimes depending on the density and distribution of induced defects on the polycrystalline graphene films. Our findings highlight the key role played by grain boundaries during graphene functionalization, and at the same time provide a novel perspective to tailor the properties of polycrystalline graphene.

Controllable Modification of Optical Properties of Graphene Oxide

Controllable generation of band gaps in graphene is one of the important current tasks in modern nanoelectronics. To investigate whether this can be achieved by controllable functionalization, we have studied the changes in optical properties of graphene oxide in water suspension upon ozone-induced oxidation of reduced graphene oxide (RGO). The reduced graphene oxide, whose properties strongly resemble graphene, was produced by oxidizing graphite using the Hummers method followed by a hydrazine reduction. Exposure of the resulting RGO to ozone for the periods of 5 to 35 minutes caused a dramatic bleaching of the sample’s visible and ultraviolet absorption and the concurrent appearance of strong visible fluorescence in previously nonemissive samples. These observed spectral changes suggest a functionalization-induced band gap opening. The ozone treatment also caused solubilization of RGO in water. Such fluorescence emission from graphene oxide was found to be highly pH-dependent. Sharp and structured excitation and emission features resembling the spectra of molecular fluorophores were present near 500 nm in basic conditions. In acidic conditions fluorescence spectra reversibly broadened and shifted to 680 nm, while the excitation spectra remained similar in shape and position, suggesting the excited state protonation of the emitting species in acidic media. Oxygen-containing addends resulting from the ozonation treatment were detected by XPS and ATR FTIR spectroscopy and computational modeling was used to relate their presence to optical transitions in localized graphene oxide fluorophores. Further research on controlled ozonation-induced functionalization of graphene will be directed towards producing graphene-based optoelectronic devices with tailored and controllable optical properties.

Nature of active intermediate particles formed during ozone-induced oxidation.

Nature of active intermediate particles formed during ozone-induced oxidation.

Ozone-induced oxidative modification of fibrinogen: Role of the D regions

Native fibrinogen is a key blood plasma protein whose main function is to maintain hemostasis by virtue of producing cross-linked fibrin clots under the influence of thrombin and fibrin-stabilizing factor (FXIIIa). The aim of this study was to investigate mechanisms of impairment of both the molecular structure and the spatial organization of fibrinogen under ozone-induced oxidation. FTIR analysis showed that ozone treatment of the whole fibrinogen molecule results in the growth of hydroxyl, carbonyl, and carboxyl group content. A similar analysis of fibrinogen D and E fragments isolated from the oxidized protein also revealed transformation of distinct important functional groups. In particular, a remarkable decay of N–H groups within the peptide backbone was observed along with a lowering of the content of C–H groups belonging to either the aromatic moieties or the aliphatic chain CH2 and CH3 units. The model experiments performed showed that the rather unexpected decay of the aliphatic CH units might be caused by the action of hydroxyl radicals, these being produced in the water solution from ozone. The observed dissimilarities in the shapes of amide I bands of the fibrinogen D and E fragments before and after ozone treatment are interpreted in terms of feasible local conformational changes affecting the secondary structure of the protein. Taken as a whole, the FTIR data suggests that the terminal D fragments of fibrinogen are markedly more susceptible to the ozone-induced oxidation than the central E fragment. The data on elastic and dynamic light scattering provide evidence that, in the presence of FXIIIa, both the unoxidized and the oxidized fibrinogen molecules bind to one another in an “end-to-end” fashion to form the flexible covalently cross-linked fibrinogen homopolymers. The γ and α polypeptide chains of the oxidized fibrinogen proved to be involved in the enzymatic cross-linking more readily than those of unaffected fibrinogen. The experimental data on fibrinogen oxidation acquired in the present study, combined with our earlier findings, make it reasonable to suppose that the spatial structure of fibrinogen could be evolutionarily adapted to some reactive oxygen species actions detrimental to the protein function.

Effects of Ozone-Induced Oxidation on the Physicochemical Properties of Myofibrillar Proteins Recovered from Bighead Carp (Hypophthalmichthys nobilis)

The effect of oxidation with ozone on myofibrillar proteins from bighead carp (Hypophthalmichthys nobilis) and its influence on the textural properties of surimi gels of bighead carp were investigated. Treatment with ozone of an appropriate concentration significantly increased the salt extractable protein (SEP), Ca2+-ATPase activity, total sulfhydryl and active sulfhydryl contents, surface hydrophobicity, and carbonyl content of the myofibrillar proteins. The breaking force and deformation of the surimi gels of bighead carp initially increased and subsequently decreased as the extent of oxidation increased. Based on sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) analysis, there were no apparent changes in the protein distribution and no new patterns appeared in electrophoresis processing analysis after the ozone treatment. Differential scanning calorimetry (DSC) found that low concentrations of ozone water rinse had slight effects on thermal stabilities of myofibrillar proteins, which coincided with the above results. The present study indicates that ozone treatment is a prospectively mild oxidation protocol for enhancing the physicochemical properties of fish proteins from bighead carp.

Effect of free radical oxidation on the structure and function of plasma fibrin-stabilizing factor

Plasma fibrin-stabilizing factor (pFXIII) is a heterosubunit protein, the main function of which is the covalent stabilization of the fibrin matrix. This paper examines the ozone-induced free radical oxidation of plasma fibrin-stabilizing factor at different stages of its enzymatic activation. Electrophoretic data on the accumulation of γ-γ-dimers and α-polymers in the formation of stabilized fibrin suggests that a reduction in the enzymatic activity of FXIIIa is largely dependent on the stage of activation of pFXIII at which the oxidation is carried out. The results of UV, IR, and Raman spectroscopy measurements suggests that the oxidation of the amino acid residues of the polypeptide chains of pFXIII primarily affects cyclic, cysteine, and cystine groups and leads to the formation of oxidation products, being accompanied by the disruption of the protein secondary structure. Dynamic light scattering measurements revealed a loosening of the protein structure in the course of free radical oxidation. Spin label EPR spectroscopy data are suggestive of a change in the pFXIII conformation as a result of oxidative modification. Possible reasons for the different sensitivity of pFXIII to oxidative modification in the process of enzymatic activation are discussed. It is presumed that FXIII-B2 regulatory subunits function as scavenges of reactive oxygen species, thereby protecting FXIII-A2 catalytic subunits from oxidation.

Ozone-induced oxidative modification of fibrinogen molecules

Ozone-induced oxidation of fibrinogen has been investigated. The conversion of oxidized fibrinogen to fibrin catalyzed either by thrombin or by a reptilase-like enzyme, ancistron, in both cases is accompanied by production of gels characterized by a higher weight/length ratio of fibrils in comparison with the native fibrin gels. IR spectra of the D and E fragments isolated from unoxidized and oxidized fibrinogen suggest a noticeable transformation of functional groups by oxidation. A decrease in content of N-H groups in the peptide backbone and in the number of C-H bonds in aromatic structures, as well as a decrease in the intensity of the C-H valence vibrations in aliphatic fragments CH2 and CH3 were found. The appearance in the differential spectra of the D fragments of rather intense peaks in the interval of 1200-800 cm(-1) clearly indicates the interaction of ozone with amino acid residues of methionine, tryptophan, histidine, and phenylalanine. Comparison of the differential spectra for the D and E fragments suggests that fibrinogen fragment D is more sensitive to the oxidant action than fragment E. Using EPR spectroscopy, differences are found in the spectra of spin labels bound with degradation products of oxidized and unoxidized fibrinogen, the D and E fragments, caused by structural and dynamical modifications of the protein molecules in the areas of localization of the spin labels. The relationship between the molecular mechanism of oxidation of fibrinogen and its three-dimensional structure is discussed.

Effect of an Inclusion Complex of an Aminomethylated Dihydroquercetin Derivative in Cyclodextrin on Ozone-Induced Oxidation of Fibrinogen

The ability of a water-soluble inclusion complex (KN-14-CD) of an aminomethylated dihydroquercetin derivative (KN-14) in β-cyclodextrin (CD) to inhibit ozone-induced oxidation of fibrinogen was evaluated. KN-14-CD prevented ozone-induced oxidation of fibrinogen and preserved its ability to form clots after the addition of thrombin. The ability of KN-14-CD to prevent oxidative modification of fibrinogen was more pronounced than that of native dihydroquercetin (taxifolin).

Ozone-induced oxidative modification of plasma fibrin-stabilizing factor

The plasma fibrin-stabilizing factor (pFXIII) function is to maintain a hemostasis by the fibrin clot stabilization. The conversion of pFXIII to the active form of the enzyme (FXIIIа) is a multistage process. Ozone-induced oxidation of pFXIII has been investigated at different stages of its enzyme activation. The biochemical results point to a decrease of an enzymatic activity of FXIIIа depending largely on the stage of the pFXIII conversion into FXIIIа at which oxidation was carried out. UV-, FTIR- and Raman spectroscopy demonstrated that chemical transformation of cyclic, NH, SH and S–S groups mainly determines the oxidation of amino acid residues of pFXIII polypeptide chains. Conversion of pFXIII to FXIIIa proved to increase protein sensitivity to oxidation in the order: pFXIII<pFXIII activated by thrombin<pFXIII in the presence of calcium ions<FXIIIa. The dynamic light scattering data indicate that the three-dimensional structure of pFXIII becomes loosened due to oxidative modification. ESR spectroscopy data also point to conformational changes of the fibrin-stabilizing factor under oxidation. Taking into account these new findings it seems reasonable to assume that the inhibitory/carrier FXIII-B subunits can serve as scavengers of ROS. Hypothetically, this mechanism could help to protect the key amino acid residues of the FXIII-A subunits responsible for the enzymatic function of FXIIIa.

Oxidized modification of fragments D and E from fibrinogen induced by ozone

Ozone-induced free-radical oxidation of fragments D and E from fibrinogen has been studied. The methods of elastic and dynamic light scattering in combination with electrophoresis of unreduced samples have shown the acceleration of enzymatic covalent crosslinking of molecules of oxidation-modified fragment D under the action of factor XIIIa. UV and IR spectroscopy shows that free-radical oxidation of amino acid residues of polypeptide chains catalyzed by ozone affects the cyclic and amino groups, giving rise to generation of mainly oxygen-containing products. Comparison of the IR spectra obtained for the oxidation-modified D and E fragments revealed more significant transformation of functional groups for the D fragment. EPR spectroscopy showed that the rotational correlation time of spin labels bound to the ozonized proteins decreased in comparison with the non-ozonized proteins. The rotation correlation time of the radicals covalently bound to the ozonized D and E fragments suggests that D fragment of fibrinogen is more sensitive to free-radical oxidation followed by local structural changes. Possible causes of different degrees of oxidation for fragments D and E are discussed.

Low-Concentration Ozone Reacts with Plasmalogen Glycerophosphoethanolamine Lipids in Lung Surfactant

Ozone is a common environmental toxicant to which individuals are exposed to on a daily basis. While biochemical end points such as increased mortality, decrements in pulmonary function, and initiation of inflammatory processes are known, little is actually understood regarding the chemical mechanisms underlying changes in pulmonary health, especially for low concentrations of ozone. This study was undertaken to investigate ozone-induced oxidation of endogenous lipids that are potentially exposed to environmental ozone within lung, specifically focusing on plasmalogen glycerophospholipids present in pulmonary surfactant. Sensitive liquid chromatography-mass spectrometry methods were developed to follow oxidation of diacyl and plasmalogen phosphatidylethanolamine (PE) phospholipids and to identify and quantitate products generated by ozonolysis. Using a unilamellar vesicle system containing a 1:1 molar mixture of 1-O-octadec-1'-enyl-2-octadecenoyl-PE and 1,2-dihexadecanoyl-PC, these studies revealed that the vinyl ether bond of plasmalogens was oxidized preferentially at low concentrations of ozone (100 ppb), when compared to olefinic bond oxidation on omega-9 of the fatty acyl chain in the same phospholipids. Major phospholipid products generated were identified as 1-formyl-2-octadecenoyl-PE and 1-hydroxy-2-octadecenoyl-PE. Heptadecanal and heptadecanoic acid production was also quantitated using gas chromatography-mass spectrometry, and production was consistent with oxidation of the vinyl ether, at low concentrations of ozone. Analysis of murine lung surfactant from C57Bl/6 mice revealed several plasmalogen PE lipid species, encompassing approximately 38% of total PE species. Upon exposure of ozone (0 and 100 ppb) to murine surfactant, plasmalogen PE molecular species preferentially reacted, as compared to diacyl PE molecular species. Lysophospholipids, pentadecanal, and nonanal were found to be the primary products of surfactant ozone oxidation.

Impact of ozone exposure on the phagocytic activity of human surfactant protein A (SP-A) and SP-A variants

Surfactant protein A (SP-A) enhances phagocytosis of Pseudomonas aeruginosa. SP-A1 and SP-A2 encode human (h) SP-A; SP-A2 products enhance phagocytosis more than SP-A1. Oxidation can affect SP-A function. We hypothesized that in vivo and in vitro ozone-induced oxidation of SP-A (as assessed by its carbonylation level) negatively affects its function in phagocytosis (as assessed by bacteria cell association). To test this, we used P. aeruginosa, rat alveolar macrophages (AMs), hSP-As with varying levels of in vivo (natural) oxidation, and ozone-exposed SP-A2 (1A, 1A0) and SP-A1 (6A2, 6A4) variants. SP-A oxidation levels (carbonylation) were measured; AMs were incubated with bacteria in the presence of SP-A, and the phagocytic index was calculated. We found: 1) the phagocytic activity of hSP-A is reduced with increasing levels of in vivo SP-A carbonylation; 2) in vitro ozone exposure of hSP-A decreases its function in a dose-dependent manner as well as its ability to enhance phagocytosis of either gram-negative or gram-positive bacteria; 3) the activity of both SP-A1 and SP-A2 decreases in response to in vitro ozone exposure of proteins with SP-A2 being affected more than SP-A1. We conclude that both in vivo and in vitro oxidative modifications of SP-A by carbonylation reduce its ability to enhance phagocytosis of bacteria and that the activity of SP-A2 is affected more by in vitro ozone-induced oxidation. We speculate that functional differences between SP-A1 and SP-A2 exist in vivo and that the redox status of the lung microenvironment differentially affects function of SP-A1 and SP-A2.