In the onset of many chronic illnesses including Parkinson’s, Alzheimer’s, and cardiovascular diseases, there is evidence to support the delicate balance between prooxidant and antioxidant species is shifted in favor of the former. Under these conditions, many reactive oxygen species (ROS) including hydroxyl radicals, are generated. Hydroxyl radicals formed in close proximity to DNA, nucleotides, proteins, and lipids rapidly oxidize these biological molecules in a nonspecific way. However, their toxicity is limited by their short lifetimes. Currently, the mechanism by which hydroxyl radicals are involved in the onset of many illnesses, particularly with regard to lipid peroxidation, has yielded some controversy in the literature. Conventional studies which generate hydroxyl radicals with Fenton chemistry through bolus additions of iron and hydrogen peroxide do not mimic conditions found physiologically because there is a steady-state concentration of hydrogen peroxide concentration found in normal cellular systems. Also, former reports that used fluorescent fatty acids or free probes intercalated within liposomal membranes did not have the probes covalently attached to the phospholipids making up the liposomes. Thus, the actual placement of the probes over the analysis time may vary with experimental conditions. The objective of this research project was to prepare, characterize, and employ liposomes as models for cell membranes during free radical oxidation. Also, compared to the popularly-used technique of electron spin resonance, (ESR), our aim was to use a fluorescence-based approach which yielded the advantages of high sensitivity, fast analysis time, and less expensive equipment requirements. Degradation of fluorescently-tagged liposomes with probes covalently bound to the phospholipids was correlated with the ability of hydroxyl radicals and other possible reactive oxygen species to penetrate into the liposomes to deeper into the lipophilic layer. However, alone this experimental setup may not fully define the mechanistic role of hydroxyl radicals in lipid oxidation. Thus, a complementary approach embracing the use of MALDI-TOF mass spectrometry, lipophilic scavenger studies, and the effects of cholesterol and temperature allow a deeper understanding of the radically-driven oxidation of lipids. It was determined that hydroxyl radicals were generated and reacted with three fluorescent probes.

Environmental pollution has been a serious concern worldwide. Many degradation methods have been developed to clean sites contaminated with pollutants. More knowledge and better understanding in this field will help to protect our environment. The goal of the research in this thesis is to gain a better understanding of the mechanism of organic pollutant degradation in Fenton reactions and sonochemical reactions. Fenton degradation uses hydroxyl radical to oxidize organic compounds. The radical is produced by catalytic decomposition of hydrogen peroxide with Fe(II). Further research has found that addition of cyclodextrins can enhance degradation efficiency of hydrophobic organic pollutants. To study the mechanism of the enhancement, pollutant-cyclodextrin-Fe(II) aqueous systems were studied by fluorescence and NMR techniques. The results indicated the formation of pollutant/carboxymethyl-â-cyclodextrin/Fe(II) ternary complexes in the solution. With the ternary complex, the catalyst Fe(II) becomes closer to the pollutant, therefore leading to more efficient hydroxyl radical attack on the pollutant. Additional studies showed that hydropropyl-â- cyclodextrin, â-cyclodextrin and á-cyclodextrin bound pollutant well, but bound Fe(II) poorly. Sulfated-â-cyclodextrin did not bind well with pollutant although it bound Fe(II) well. Sonochemical degradation is another important pollutant treatment method in practice. It was found that phenol sonolysis can be enhanced by volatile hydrogen atom scavengers such as carbon tetrachloride and perfluorohexane. The non-volatile hydrogen atom scavenger iodate did not enhance phenol degradation. The first order rate constant for aqueous phenol degradation increased by about 2.2-2.8 times in the presence of 150 ìM carbon tetrachloride. In the presence of less than 1.5 ìM perfluorohexane the first order rate constant increased by about 2.3 times. Hydroquinone was the major observed reaction intermediate both in the presence and absence of hydrogen atom scavengers. Hydroquinone yields were substantially higher in the presence of hydrogen atom scavengers, suggesting that hydroxyl radical pathways for phenol degradation were enhanced by the hydrogen atom scavengers. The additives investigated in this study have potential to improve pollutant degradation efficiency. Other fields may also benefit from the information gained in this study. For example the improvement could be achieved in synthetic processes that rely on hydroxyl radical as a key intermediate.

Cerium is the most abundant of the rare earth metals, found on average at a level of 66 parts per million in the earth's crust. The unique redox properties of cerium and cerium oxide nanoparticles have led to its use in a wide variety of industrial and commercial uses such as oxygen sensors, fertilizers and as a catalyst to remove toxic gases in automobile exhaust. The use of cerium has also garnered interest in the nanotechnology field. Nanoceria has been generated in its oxide form as nanoparticles and nanorods. Recently, nanoceria has been shown to protect against oxidative stress in both animal and cell culture models. Although not fully understood, this observed protective effect of nanoceria is believed to be the result of recently identified SOD mimetic activity. Currently there is little understanding as to how nanoceria is capable of scavenging radicals or what properties makes nanoceria an effective SOD mimetic. Our data shows strong evidence that the oxidation state of nanoceria is directly related to its reported SOD mimetic activity. As such, future studies of nanoceria should be mindful of the oxidation state of nanoceria preparations as only nanoceria with a high concentration of cerium (III) have shown effective SOD mimetic activity. In addition to the characterization of nanoceria and its SOD mimetic activity, we have evidence that free cerium is capable of generating radicals and damaging DNA in vitro in the presence of hydrogen peroxide. These data strongly suggests that the rare earth inner-transition metal cerium is capable of generating hydroxyl radicals via a Fenton-like reaction. Based on these results the use of free cerium salts should be monitored to limit environmental exposure to cerium. Altogether our data would suggest that cerium by virtue of its unique redox chemistry is quite capable of accepting and donating electrons from its surroundings. In its free form cerium is able to redox cycle easily and can generate radicals. However, paradoxically nanoceria may not easily redox cycle due to the bound lattice structure of the particle. The unique nature of nanoceria and cerium leads to a unique circumstance where nanoceria is a radical scavenger while free cerium generates radicals. As such, further investigation is needed to insure that leeching or cerium from nanoceria does not abrogate any potential benefit nanoceria may provide.

The potential to use acidic hydrogen peroxide in the presence of ferrous ions (Fenton’s reagent) as a pre-treatment when producing microfibrillar cellulose (MFC) from a fully bleached birch (Betula verucosa) kraft pulp was investigated and the properties of the produced MFC was compared to the properties of a MFC produced with enzymatic pre-treatment with a monocomponent endoglucanase (FiberCare® R). The mechanical treatment to MFC was performed in a laboratory colloid mill or in a pilot high-pressure homogeniser and the pre-treated pulps as well as the produced MFCs were chemically and morphologically characterised. Additionally, the MFCs produced in the colloid mill were evaluated as strength enhancers in test sheets representing the middle ply of paperboard. From the chemical characterisation, it was concluded that the Fenton pre-treatment caused a decrease in the degree of polymerisation (DP) and an increase in both carboxyl- and carbonyl groups. The increase in carbonyl groups could not be explained by the formation of new reducing end groups due to depolymerisation which indicates that carbonyl groups are introduced along the cellulose chain. The enzymatic pre-treatment as performed in this study caused less impact on the cellulosic material, i.e. resulted in a pulp with a higher DP and a much lower amount of carbonyl- and carboxylic groups compared with the Fenton pre-treated pulps. In the subsequent mechanical treatment in a colloid mill, the Fenton pre-treated pulps were easier to process mechanically i.e. reached a higher specific surface area and a higher surface charge at a given mechanical treatment time compared to enzymatic pre-treated pulps and pulps not subjected to any pre-treatment. These findings were confirmed when MFCs were produced by homogenisation at high pressure in multiple passes; the birch kraft pulp was either pre-treated with Fenton’s reagent or the combined mechanic and enzymatic pre-treatment methodology used at the Centre Technique du Papier (CTP, France). By size fractionation, rheological measurements and scanning electron microscopy, it was revealed that Fenton pre-treatment resulted in MFC suspension containing a significantly higher proportion of small sized material (< 0.2 mm). When the MFCs were evaluated as strength enhancers in test sheets produced from a furnish consisting of a spruce (Picea abies) chemithermomechanical pulp, MFC and a retention system containing cationic starch and an anionic silica sol, Fenton pre-treated MFCs increased the strength properties more than the enzymatic pre-treated MFCs. Addition of 5 wt% Fenton pre-treated MFC resulted in an increase in z-directional strength of about 50%, an increase in tensile stiffness index of about 25% and an increase in tensile index of 35% compared to test sheets prepared without MFC addition. / The potential to use acidic hydrogen peroxide in the presence of ferrous ions (Fenton’s reagent) as a pre-treatment when producing microfibrillar cellulose (MFC) from a bleached birch kraft pulp was investigated and the properties of the produced MFC was compared to the properties of a MFC produced with enzymatic pre-treatment. Additionally, the MFCs evaluated as strength enhancers in test sheets representing the middle ply of paperboard. From the chemical characterisation, it was concluded that the Fenton pre-treatment caused a decrease in the degree of polymerisation (DP) and an increase in both carboxyl- and carbonyl groups. In the subsequent mechanical treatment in a colloid mill, the Fenton pre-treated pulps were easier to process mechanically indicating a potential to lower the energy consumption. When the MFCs were evaluated as strength enhancers in test sheets, Fenton pre-treated MFCs increased the strength properties more than the enzymatic pre-treated MFCs at a given mechanical treatment time. Addition of 5 wt% Fenton pre-treated MFC resulted in an increase in z-directional strength of about 50%, an increase in tensile stiffness index of about 25% and an increase in tensile index of 35% compared to test sheets prepared without MFC addition.

Field and greenhouse experiments were conducted to determine the effect of auxin injury on soybean and cotton due to spray hose material, formulation and cleanout procedures on auxin equipment cleanout. Visual estimations of injury (VEOI) in wheat, height reduction, and yield reduction due to rimsulfuron and glyphosate titration was higher when compared to rimsulfuron only treatments with respect to 1/2X through the 1/256X treatments. Sequestration of 2,4-D within agricultural hose types did differ due to hose type and is confirmed by analytical testing, but field observation of wheat did not show differences among treatments due to VEOI, height reduction or yield reduction. Using soybean as a bio-indicator, differences did occur with respect to dicamba sequestration in agricultural hose types with respect to VEOI, height reduction, node reduction, yield reduction and ppm analyte retained. Results indicate chemical makeup of hose type in determination of ppm analyte dicamba retained. Cleaning procedures of water or ammonia do not prove to be different with respect to VEOI, height reduction, yield reduction or ppm analyte retained. Sequestration of 2,4-D within valved manifold systems and using water or ammonia as cleanout procedures in conjunction with rinse procedures did not show differences with respect to VEOI, height reduction, nodes above cracked boll (NACB), yield reduction or ppm analyte retained. It was not until standard 2,4-D applications were applied in field experiments when differences were observed. Deactivation of dicamba and 2,4-D using the Fenton procedure within various rates, showed an interaction with respect to VEOI, height reduction, node reduction, yield reduction and ppm analyte. Using soybean as a bio-indicator showed differences with the Fenton procedure deactivating the dicamba analyte in the 1/16X, 1/64X and 1/256X rate with respect to VEOI, height reduction, node reduction, yield reduction and ppm analyte retained. Using cotton as a bio-indicator showed differences with the Fenton procedure deactivating the 2,4-D analyte in every rate with respect to VEOI, height reduction, yield reduction and ppm analyte.

no / Vitiligo is characterized by a mostly progressive loss of the inherited skin color. The cause of the disease is still unknown, despite accumulating in vivo and in vitro evidence of massive oxidative stress via hydrogen peroxide (H2O2) and peroxynitrite (ONOO−) in the skin of affected individuals. The most favored hypothesis is based on autoimmune mechanisms. Since depletion of the essential amino acid l-tryptophan (Trp) severely affects various immune responses, we here looked at Trp metabolism and signaling in these patients. Our in vivo and in vitro data revealed total absence of epidermal Trp hydroxylase activities and the presence of H2O2/ONOO− deactivated indoleamine 2,3-dioxygenase. Aryl hydrocarbon receptor signaling is severely impaired despite the ligand (Trp dimer) being formed, as shown by mass spectrometry. Loss of this signal is supported by the absence of downstream signals (COX-2 and CYP1A1) as well as regulatory T-lymphocytes and by computer modeling. In vivo Fourier transform Raman spectroscopy confirmed the presence of Trp metabolites together with H2O2 supporting deprivation of the epidermal Trp pool by Fenton chemistry. Taken together, our data support a long-expressed role for in loco redox balance and a distinct immune response. These insights could open novel treatment strategies for this disease.—Schallreuter, K. U., Salem, M. A. E. L., Gibbons, N. C. J., Maitland, D. J., Marsch, E., Elwary, S., Healey, A. R. Blunted epidermal l-tryptophan metabolism in vitiligo affects immune response and ROS scavenging by Fenton chemistry, part 2: epidermal H2O2/ONOO−-mediated stress in vitiligo hampers indoleamine 2,3-dioxygenase and aryl hydrocarbon receptor-mediated immune response signaling.

Numerous chemical species are important to the health of biological systems. Some species can be beneficial at low doses and harmful at high doses. Other species are highly reactive and trigger serious cell damage. Improved methods to detect the presence and activity of such species are needed. In this work, several biologically important species were studied using appropriate analytical techniques. Fluoride is an important species in human physiology. It strengthens teeth and gives protection against dental caries. However, elevated concentrations of fluoride in the body can lead to health problems such as dental and skeletal fluorosis. Reported fluoride sensors used fluorescence quenching methods in determining fluoride concentration. Our study explored synthesis and characterization of 1,8-bis(phenylthioureido) naphthalene (compound 1) as a fluoride sensing molecule. Compound 1 showed a remarkable 40 fold enhancement in fluorescence with 5 eq of fluoride addition. Compound 1 also showed possibility of visual colorimetric sensing with fluoride. Free radical mediated oxidations of biomolecules are responsible for different pathological conditions in the human body. Superoxide is generated in cells and tissues during oxidative burst. Moderately reactive superoxide is converted to peroxyl, alkoxyl and hydroxyl radicals by various enzymatic, chemical, and biochemical processes. Hydroxyl radical imparts rapid, non specific oxidative damage to biomolecules such as proteins and lipids. Superoxide also reacts with nitric oxide in cells to yield peroxynitrite, which is highly reactive and damages biomolecules. Both hydroxyl radical and peroxynitrite readily react with amino acids containing aromatic side chains. Low density lipoprotein (LDL) carries cholesterol in the human body. Elevated concentration of LDL is a potential risk factor for atherosclerosis. Previous research drew a strong correlation between oxidized low density lipoprotein (ox-LDL) and plaque formation in the arterial wall. More importantly, oxidative damage causes structural changes to the LDL protein (apo B-100) which might facilitate the uptake of LDL by macrophages. In this study LDL was exposed to various concentrations of hydroxyl radical peroxynitrite and hypochlorite. Thereafter oxidized amino acid residues in apo B-100 were mapped by LC-MS/MS methods. We found widely distributed oxidative modifications in the apo B-100 amino acid sequence.

no / Vitiligo is characterized by a progressive loss of inherited skin color. The cause of the disease is still unknown. To date, there is accumulating in vivo and in vitro evidence for massive oxidative stress via hydrogen peroxide (H2O2) and peroxynitrite (ONOO−) in the skin of affected individuals. Autoimmune etiology is the favored theory. Since depletion of the essential amino acid l-tryptophan (Trp) affects immune response mechanisms, we here looked at epidermal Trp metabolism via tryptophan hydroxylase (TPH) with its downstream cascade, including serotonin and melatonin. Our in situ immunofluorescence and Western blot data reveal significantly lower TPH1 expression in patients with vitiligo. Expression is also low in melanocytes and keratinocytes under in vitro conditions. Although in vivo Fourier transform-Raman spectroscopy proves the presence of 5-hydroxytryptophan, epidermal TPH activity is completely absent. Regulation of TPH via microphthalmia-associated transcription factor and l-type calcium channels is severely affected. Moreover, dopa decarboxylase (DDC) expression is significantly lower, in association with decreased serotonin and melatonin levels. Computer simulation supports H2O2/ONOO−-mediated oxidation/nitration of TPH1 and DDC, affecting, in turn, enzyme functionality. Taken together, our data point to depletion of epidermal Trp by Fenton chemistry and exclude melatonin as a relevant contributor to epidermal redox balance and immune response in vitiligo.

Eutypa dieback, one of several grapevine trunk diseases (GTDs), is of serious concern to the grape industry globally. This disease is caused by the fungus Eutypa lata but it is often seen in consortia growth with Phaeoacremonium minimum and Phaeomoniella chlamydospora. It is vital to understand the mechanisms for how this disease functions to develop control measures to combat it. Brown rot fungi are able to use a complex of low molecular weight (LMW) metabolites to induce a Fenton reaction to deconstruct woody tissue. These metabolites are part of a chelator mediated Fenton (CMF) chemistry that produces reactive oxygen species that are capable of depolymerizing wood polymers. We propose that a mechanism similar to CMF chemistry may be occurring in grapevine trunk disease pathogens. This thesis investigates how LMW metabolites produced by the fungi contribute to the disease and decay progression in GTDs. Research on Mite control in the laboratory with abamectin was also investigated, as research in this area was required when mites infested our fungal cultures and suitable laboratory controls were not available. Research on the GTD fungi was initiated by first examining whether metabolites produced by the three fungi can function in a manner to promote reactions like the CMF system. We separated and identified specific metabolites that potentially could contribute to CMF chemistry. We found that all three GTD fungi were able to produced LMW metabolites that promoted CMF chemistry, and we hypothesized that this mechanism contributes to processes leading to tissue necrosis in grapevine trunk wood. To explore the development of effective control measures based on this newly discovered mechanism for pathogenesis, we also explored the use of antioxidant/chelator compounds, BHA and BHT, in the control of the consortia fungi. Biocontrol organisms, Bacillus subtilis and Trichoderma atroviride, that produce antioxidants were also tested as biocontrols against the fungi involved in Eutypa Dieback disease. We found that BHA was highly effective in inhibiting fungal growth for all three fungi at concentrations higher than 0.5mM, and both B. subtilis and T. atroviride proved to be effective biocontrol agents in inhibiting E. lata, P. minimum, and P. chlamydospora.