III-V compound Gallium Antimonide (GaSb), with a low bandgap of 0.72 eV at room temperature, is an attractive candidate for a variety of potential applications in optoelectronic devices. Ion implantation, among non-epitaxial methods, is a common and reliable doping technique to achieve local doping and obtain high-performance ohmic contacts in order to form a pn junction in such devices. An advantage of this technique over the diffusion method is the ability to perform a low-temperature process leading to accurate control of the dopant profile and avoiding Sb evaporation from GaSb surface occurring at 370 C. In this work, the effect of protons and sulfur ions as two implant species on the electrical behavior of MBE-grown undoped GaSb on semi-insulating (SI) GaAs was investigated via the Hall Effect. Protons and sulfur ions were implanted at room temperature (27 C) and 200 C, respectively, and rapid thermal annealing (RTA) was implemented at various temperatures and durations upon encapsulated GaSb. The damage induced by protons enhanced the hole density of GaSb up to around 10 times, whereas mobilities showed both increase and decrease compared to the un-implanted one, depending on the dose. While the activation of sulfur donors at an elevated temperature was anticipated after annealing sulfur implanted GaSb, instead it led to increase in p-type concentration, as the residual damage originated from sulfur implantation dominated substitutional doping. Furthermore, GaSb p/n photovoltaic devices were fabricated by applying sulfur implantation through silicon nitride layer at RT into an n-GaSb wafer (n-type base, p-type emitter). The device showed a rectifying current and photovoltaic characteristic. The J-V plot under AM1.5G illumination conditions, before and after an etch-back optimizing process, indicated lower short circuit current density J_sc, the same open circuit voltage V_oc, and higher fill factor FF, compared to the photovoltaic device with a p-type base. Also, both normalized series R_s and shunt R_p resistances in p/n diode indicated lower and higher values, respectively, as opposed to a GaSb p++/p diode, indicative of higher quality and lower manufacturing defects. / Master of Science / Generally, the photovoltaic effect is a process by which voltage or electric current is generated in a photovoltaic cell when exposed to light. A solar cell is a photovoltaic device, typically consisting a pn junction, that converts incident photon power into electrical power and delivered to a load to do electrical work for variety of applications. There are variety of methods to form a pn junction and fabricate such devices, among which ion implantation is a reliable doping technique. In this process, dopant ions are accelerated and smashed into a perfect semiconductor lattice, creating a cascade of damage that may displace a thousand atoms for each implanted ion and become activated after an annealing process. The ions themselves can act as either electron donors, make the semiconductor n-type, or electron acceptors, make it p-type. In this work, sulfur ions and protons, as two implant species, were implanted into separate Gallium Antimonide (GaSb) substrates and the effect of each on the electrical behavior of GaSb was investigated by Hall effect experiment. Both species raised hole carrier concentration. This behavior was not expected for sulfur ions as they would be assumed to act as electron donors after activation and convert the GaSb surface to an n-type semiconductor. It was identified that this behavior is due to the domination of created defects during implantation over the number of activated sulfur donors. The same characteristics were predicted and verified for proton implantation as well, the effect of which is just leaving damage in the lattice. Furthermore, to verify this method for converting n-type GaSb to p-type and fabricating a pn junction in GaSb for photovoltaic application, sulfur implantation into an n-type GaSb wafer was performed and optimized by removing the excess surface damage away from the device's metal contacts using wet etching. The device showed a diode-like rectifying current and photovoltaic characteristic. Some parameters such as short circuit current density J_sc, open circuit voltage V_oc, fill factor FF, and resistances (shunt and series) were measured and calculated using J-V plot under dark and illuminated conditions.

Virginia's Coastal Plain region contains the majority of the state's agricultural production despite having low nutrient soils. The soils in this region are predominantly coarse-textured acid soils with low cation exchange capacities (CEC) (< 3 cmol kg-1) and thus frequently exhibit nutrient deficiencies, including cationic nutrients which are not easily lost by leaching in soils with greater CEC. As a result, soils require careful nutrient management to maintain production levels. Soybean (Glycine max), the world's fourth largest crop, shows sensitivity to manganese availability and regularly experiences deficiency symptoms in low-CEC coastal plain soils. Tomato (Solanum lycopersicum) production, one of the 3 largest vegetable production systems in the world, requires careful management of various nutrients, particularly phosphorous, sulfur, and boron, for proper fruit development. Two novel coated fertilizer products consisting of granular KCl coated in a nutrient powder and a sugar-acid chelating agent are investigated as multi-nutrient sources for soybeans and tomatoes. A comprehensive review of the chemistry, behavior, and functionality of key nutrients provided by the fertilizer (P, S, Mn, and B) in both soils and plant tissues and the current state of chelate use in agriculture is provided along with related production issues with tomatoes and soybean. A greenhouse study investigating the ability of the first coated product (Mn + B coated KCl) to provide micronutrients to soybeans was conducted. Using both low and high organic matter (OM) soils (10 g kg-1; 36 g kg-1), Mn + B coated KCl increased soil Mn compared to no fertilizer and uncoated KCl. Additionally, Mn + B coated KCl increased total above ground tissue Mn compared to control and uncoated KCl for the low OM soil but not for the high OM soil, which was likely due to OM leading to the formation of metal-ligand complexes. There were no significant results regarding B concentration in either the soil or plant tissue due to the low application rate provided by the coating. The same fertilizer (Mn + B coated KCl) was investigated under field conditions to determine if increased soil and tissue Mn can be maintained under various environmental factors. Our results found that for all growing seasons and locations, there were no significant treatment differences between months for both Mn and B, but total monthly averages did fluctuate between months, probably reflecting changes in soil moisture and redox status. When averaged across the entire growing season, differences between treatments were inconsistent. Under field conditions, environmental conditions such as soil moisture and leaching likely masked any consistent treatment effects of the coated products. Two potential soil amendments, P + S + B coated KCl and glucoheptonate (GH), were investigated for their ability to provide nutrients to tomatoes. Three greenhouse trials, each lasting 3 weeks, were conducted. In the first trial, P + S + B coated KCl was compared to the current agronomic recommendation rates for P, S, and B. The coated KCl significantly increased soil and plant tissue P and B compared to all but the KCl + P and KCl + B treatments. The second trial was a glucoheptonate rate trial and showed a significant positive correlation between GH rate and soil and tissue B. The third trial combined and compared the coated KCl and GH products and showed that the treatments containing the coated KCl had significantly increased P, S, and B soil and tissue concentrations, with GH application having no synergistic effect / Ph. D. / The majority of the Virginia’s agricultural production occurs on the nutrient poor soils of the coastal plains where nutrient deficiencies are common. As a result, careful nutrient management strategies are required to maintain crop production levels, including major crops like soybean and tomato. Soybean (Glycine max) show sensitivity to manganese (Mn) availability and regularly experience deficiency symptoms in this region. On the other hand, tomato (Solanum lycopersicum) production requires careful management of nutrients such as phosphorous, sulfur, and boron for proper fruit development. In this dissertation, two novel coated fertilizer products, granular KCl coated in a nutrient powder and a sugar-acid chelating agent, are investigated as multi-nutrient sources for soybeans and tomatoes. This dissertation starts with a comprehensive review of the chemistry, behavior, and functionality of key nutrients provided by the fertilizer in soils and plant tissues, followed by a review of the current state of sugar acid use in agriculture. The production systems for soybeans and tomatoes for VA and the USA will also be discussed. The second component of this dissertation is a greenhouse study investigating the ability of the first coated product (Mn+B coated KCl) to provide micronutrients to soybeans. The Mn+B coated KCl significantly increased Mn compared to control and uncoated KCl treatments in the soil for both soil types and in tissue for the low OM soil. The third component of this dissertation investigates the same fertilizer under field conditions. Our results showed that for all growing seasons and locations, there were no significant treatment differences between months for both Mn and B, but monthly averaged concentrations did fluctuate over time, probably reflecting seasonal environmental shifts. When averaged annually, inconsistent differences were seen between treatments. Under field conditions, environmental conditions like increased soil moisture and leaching likely masked any consistent treatment effects of the coated products. The fourth component of this dissertation investigates two potential soil amendments, the second coated KCl product (P+S+B coated KCl) and glucoheptonate (GH), for their ability to provide nutrients to tomatoes. The study consists of 3 separate greenhouse trials, each lasting 3 weeks. In the first trial, P+S+B coated KCl was compared to the current agronomic recommendation rates for P, S, and B. The coated KCl significantly increased soil and plant tissue P and B compared to all but the KCl + P and KCl + B treatments. The second trial was a glucoheptonate rate trial and showed a significant positive correlation between GH rate and soil and tissue B. The third trial combined and compared the coated KCl and GH products and showed that the treatments containing the coated KCl had significantly increased P, S, and B soil and tissue concentrations, with GH application having no enhancing effect.

The thermodynamic properties of aqueous sulfur species were estimated using a structure-based, group contribution additivity method that is based upon first-order approximations. Structural groups were chosen so as to minimize subjectivity and maximize the ease of recognition and include: (1) Sn^*, polymeric sulfur (as 1/n, where n is the length of the longest continuous sulfur chain in the species), (2) O₃S^IV; (3) O₃S^VI; (4) O₂S^III and (5) bridging oxygen. In addition, a modified "charge-to-size" ratio (C) is used to model the coulombic interaction between ions and the solvent. Multiple linear regressions of these thermodynamic data were performed in terms of structural groups to yield fundamental equations for the model. Regression coefficients were used to estimate thermodynamic properties of a number of aqueous species for which no experimental data currently exist. Model-derived thermodynamic data were used to find the thermodynamic stability of intermediate sulfur species that occur during the aqueous oxidation of sulfide minerals, which identified at least one thermodynamically feasible pathway for the overall reaction. The data were also used to construct an EhpH diagram for aqueous sulfur species with average sulfur oxidation states less than sulfate (VI). The structure-thermodynamic correlation was used to determine the likely structure of the aqueous S₂O₅²⁻ ion, which has been debated over the past 50 years. The rate of decomposition of the ferric thiosulfate complex was observed to vary as the square of the concentration of the complex. The decomposition of this complex in acid solutions is strongly dependent on temperature, E_a = 120(±15) kJ mol⁻¹. The rate of reaction increases was observed to increase with increasing ionic strength, consistent with the interaction of two positively charged ions to form the activated complex. This study resolves many of the inconsistencies found in earlier studies and shows that reaction with H⁺ is a more important sink for S₂O₃²⁻ than reaction with Fe³⁺ when pH > -1.7. Comprehensive rate laws for aqueous pyrite oxidation were produced using experimentally determined data and data reported in the literature. Rate data available in the literature for the reaction of pyrite with dissolved oxygen (DO) to were compiled to produce a rate law that is applicable over three and one half orders of magnitude in DO concentration over the pH range 2-10. A series of batch, and mixed flow reactor experiments were performed to determine the effect of SO₄²⁻, Cl⁻, ionic strength and dissolved oxygen on the rate of reaction of pyrite with ferric tron. Only dissolved oxygen was found to have any appreciable effect. The results of this study were combined with kinetic data reported in the literature to formulate rate laws that are applicable over a six order of magnitude range in Fe³⁺ and Fe²⁺ concentration for the pH range ~0.5-3.0. Fundamental rates laws were formulated for each system and showed that the reaction order for ferric iron changed, thus suggesting a change in reaction mechanism. An observed rate correlation with the Fe³⁺/Fe²⁺ ratio indicates that the rate is proportional to Eh, and is best modelled by a non-ideal, non-site specific Freundlich multilayer isotherm. Because rate is observed to be positively correlated with the concentration of the aqueous oxidant only, the rate determining step for the aqueous oxidation of pyrite can be identified as the electron transfer from the mineral to the oxidant. / Ph. D.

Dewatered sludges and biosolids generated from wastewater treatment facilities are known to emit malodorous odors causing public inconvenience. The odors typically comprise of reduced organo sulfur based compounds and nitrogen containing compounds. Lime stabilization is a technique which is commonly used in the wastewater industry to produce biosolids having reduced odors that can be safely land disposed. In this research, odors produced from dewatered sludges and lime stabilized biosolids were investigated. Lime dosing and incorporation in sludge play an important role in generation of reduced sulfur and trimethylamine (TMA) odor compounds. Results revealed that poor lime dosing can lead to an increase in odors due to biological generation of volatile sulfur compounds (VSCs) during storage. In this study, a belt filter press gave a higher production of sulfur and TMA odors compared to a vacuum filter for the same sludge, which is attributed to the shear imparted to sludge during the dewatering process. Preliming studies suggested incomplete mixing of lime with sludge led to biological activity. The achievement of the correct pH and its maintenance during storage is considered critical for effective odor management from lime stabilized biosolids. A positive linear relation was obtained between sulfur based odor production and labile protein content in sludge. Furthermore, as the Al/Fe ratio increased, the labile proteins was observed to decrease. Trivalent metals are found to play an important role in binding of labile proteins thus effecting odor potential contained in sludge/biosolids. This was found true for most sludge irrespective of their liming status and independent of upstream process conditions. Further work in this area is needed to be able to provide a better understanding of odor production to aid in development of odor control techniques. Trimethylamine odors, having a characteristic fishy odor, are commonly found in lime stabilized biosolids. Cationic polymers used as dewatering aids are the primary precursors for TMA production. Proteins present in sludge are also associated with odor forming compounds but they produce much lower levels than polymers. These two components under the action of shear present in dewatering devices such as centrifuge are more likely to cause an increase in odor production from lime stabilized biosolids. It was also determined that abiotic polymer degradation to produce TMA either does not occur, or the rate is so slow that TMA production in this way is insignificant for actual field situations. / Master of Science

Iron sulfur (FeS) clusters are ubiquitous cofactors required for numerous fundamental biochemical processes, including DNA replication and repair, transcription, and translation. In the cell, these metallocofactors require a dedicated protein pathway for assembly. The Cytosolic Iron Sulfur Cluster Assembly (CIA) pathway is conserved across higher-level eukaryotes and is responsible for building and inserting these cofactors into the FeS proteins that need them. A major unsolved problem in the FeS cluster biogenesis field is how so many diverse FeS proteins are identified for cluster insertion. Several studies have identified a multiprotein complex containing Cia1, Cia2, and Met18 as the CIA targeting complex responsible for FeS cluster recognition and target maturation. The CIA targeting complex has been shown to associate with an FeS cluster protein, Nar1. Nar1 is a CIA factor that plays an unknown role in cluster transfer. Little information is known about the structure of the CIA targeting complex its mechanism of FeS cluster protein recognition. In this thesis, I investigate the architecture of the CIA targeting complex as well as the role each subunit plays in identification of apo-proteins and iron-sulfur cluster insertion. Previous proteomic and cell biological studies from the Lill lab propose that the CIA targeting complex exists as a mixture of discrete complexes in vivo. Each of these complexes is responsible for recognizing a distinct subset of targets. Herein, we utilize affinity co-purification and size exclusion chromatography investigate connectivity of the targeting complex, identify stable subcomplexes, and define their roles in recognizing our two model targets Rad3 and Leu1. We determine the CIA targeting complex contains one Met18, two Cia1, and four Cia2 polypepides. This complex is required to recognize Leu1. Our experiments reveal the formation of the stable subcomplexes Cia1-Cia2 and Met18-Cia2, which is sufficient to identify to Rad3. We also interrogate the role of Nar1 in binding to targets and cluster transfer, excluding the model that it acts as an adapter for cluster transfer. Furthermore, using site directed mutagenesis, combined with our co-purification and in vivo assays, we map the key interfaces required to form the targeting complex and investigate how their mutations impacts CIA function in vivo. We identify the binding site of Cia1 on Cia2, as well as the general region in which Cia2 binds to Met18. Through these experiments, we shed light on the role these subunits of CIA targeting complex and Nar1 play in FeS target recognition and FeS cluster transfer.

by Lui Ka Man. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (leaves 143-166). / Abstracts in English and Chinese. / Acknowledgements --- p.i / List of Abbreviations --- p.ii / Abstract --- p.iv / 摘要 --- p.viii / List of Tables --- p.xi / List of Figures --- p.xii / Contents --- p.xvii / Chapter CHAPTER 1 --- INTRODUCTION / Chapter 1.1 --- Sulfur-Containing Amino Acids --- p.1 / Chapter 1.2 --- Metabolism of Sulfur-Containing Amino Acids --- p.3 / Chapter 1.2.1 --- The Metabolic Pathways --- p.3 / Chapter 1.2.2 --- Metabolic Regulation of Homocysteine --- p.7 / Chapter 1.3 --- Sulfur-Containing Amino acids and Health --- p.10 / Chapter 1.3.1 --- Sulfur-Containing Amino Acids and Renal Diseases --- p.11 / Chapter 1.3.2 --- Sulfur-Containing Amino Acids and the Nervous System --- p.13 / Chapter 1.3.3 --- Sulfur-Containing Amino Acids and Heart Diseases --- p.16 / Chapter 1.3.4 --- Sulfur-Containing Amino Acids and Liver Diseases --- p.20 / Chapter 1.4 --- Vitamin C (Ascorbic Acid) --- p.21 / Chapter 1.4.1 --- Biosynthesis 、 --- p.23 / Chapter 1.4.2 --- Vitamin C Transport System --- p.24 / Chapter 1.4.2.1 --- Uptake of Ascorbic Acid --- p.25 / Chapter 1.4.2.2 --- Uptake of Dehydroascorbic Acid --- p.26 / Chapter 1.5 --- Vitamin C and Health --- p.28 / Chapter 1.5.1 --- Vitamin C and Heart Diseases --- p.28 / Chapter 1.5.2 --- Vitamin C and Renal Diseases --- p.29 / Chapter 1.5.3 --- Vitamin C and Brain Diseases --- p.30 / Chapter 1.5.4 --- Vitamin C and Liver Diseases --- p.31 / Chapter 1.6 --- The Aims of Project --- p.33 / Chapter CHAPTER 2 --- MATERIALS AND METHODS / Chapter 2.1 --- Materials --- p.35 / Chapter 2.2 --- Preparation of Materials --- p.37 / Chapter 2.2.1 --- Mobile Phase for Ascorbic Acid Analysis --- p.37 / Chapter 2.2.2 --- Mobile Phase for Amino Acid Analysis --- p.37 / Chapter 2.2.3 --- Reagents for RNA Extraction and Reverse Transcription- Polymerase Chain Reaction (RT-PCR) --- p.38 / Chapter 2.2.4 --- Sense and Antisense Primers --- p.38 / Chapter 2.2.5 --- Reagents for Electrophoresis --- p.40 / Chapter 2.3 --- Animals --- p.40 / Chapter 2.4 --- Experimental Studies --- p.41 / Chapter 2.5 --- Methods --- p.41 / Chapter 2.5.1 --- Ascorbic Acid Analysis --- p.41 / Chapter 2.5.1.1 --- Extraction of Ascorbic Acid --- p.41 / Chapter 2.5.1.2 --- Chromatography --- p.42 / Chapter 2.5.2 --- Amino Acid Analysis --- p.45 / Chapter 2.5.2.1 --- Sample Preparation --- p.45 / Chapter 2.5.2.2 --- Chromatography --- p.45 / Chapter 2.5.3 --- Determination of RNA Expression by RT-PCR Analysis --- p.50 / Chapter 2.5.3.1 --- RNA Isolation --- p.50 / Chapter 2.5.3.2 --- Measurement of RNA Yield --- p.51 / Chapter 2.5.3.3 --- Reverse Transcription --- p.51 / Chapter 2.5.3.4 --- Polymerase Chain Reaction (PCR) --- p.52 / Chapter 2.5.3.5 --- Separation of PCR Products by Agarose Gel Electrophoresis --- p.52 / Chapter 2.5.3.6 --- Quantification of Band Density --- p.53 / Chapter 2.6 --- Statistical Analysis --- p.53 / Chapter CHAPTER 3 --- RESULTS / Chapter 3.1 --- Effects of Sulfur-Containing Amino Acids and Leucine on Ascorbic Acid Distributions in Mice --- p.54 / Chapter 3.1.1 --- Effects of Sulfur-Containing Amino Acids and Leucine on Ascorbic Acid Concentrations in the Plasma --- p.55 / Chapter 3.1.2 --- Effects of Sulfur-Containing Amino Acids and Leucine on Ascorbic Acid Concentrations in the Kidney --- p.57 / Chapter 3.1.3 --- Effects of Sulfur-Containing Amino Acids and Leucine on Ascorbic Acid Concentrations in the Liver --- p.59 / Chapter 3.1.4 --- Effects of Sulfur-Containing Amino Acids and Leucine on Ascorbic Acid Concentrations in the Brain --- p.61 / Chapter 3.1.5 --- Effects of Sulfur-Containing Amino Acids and Leucine on Ascorbic Acid Concentrations in the Heart --- p.63 / Chapter 3.1.6 --- Summary --- p.65 / Chapter 3.2 --- Time-Response --- p.66 / Chapter 3.2.1 --- Effects of Sulfur-Containing Amino Acids and Leucine Administration for Various Periods on Ascorbic Acid Concentrations in the Plasma --- p.67 / Chapter 3.2.2 --- Effects of Sulfur-Containing Amino Acids and Leucine Administration for Various Periods on Ascorbic Acid Concentrations in the Kidney --- p.69 / Chapter 3.2.3 --- Effects of Sulfur-Containing Amino Acids and Leucine Administration for Various Periods on Ascorbic Acid Concentrations in the Liver --- p.71 / Chapter 3.2.4 --- Effects of Sulfur-Containing Amino Acids and Leucine Administration for Various Periods on Ascorbic Acid Concentrations in the Brain --- p.73 / Chapter 3.2.5 --- Effects of Sulfur-Containing Amino Acids and Leucine Administration for Various Periods on Ascorbic Acid / Chapter 3.2.6 --- Summary --- p.77 / Chapter 3.3 --- Effects of Sulfur-Containing Amino Acids and Leucine on SVCT and GLUT3 Gene Expressions --- p.78 / Chapter 3.3.1 --- Effects of Sulfur-Containing Amino Acids and Leucine Administration on SVCT mRNA Expression in the Kidney --- p.79 / Chapter 3.3.2 --- Effects of Sulfur-Containing Amino Acids and Leucine Administration on SVCT mRNA Expression in the Liver --- p.89 / Chapter 3.3.3 --- Effects of Sulfur-Containing Amino Acids and Leucine Administration on SVCT and GLUT3 mRNA Expression in the Brain --- p.98 / Chapter 3.3.4 --- Effects of Sulfur-Containing Amino Acids and Leucine Administration on SVCT mRNA Expression in the Heart --- p.109 / Chapter 3.3.5 --- Summary --- p.115 / Chapter 3.4 --- Sulfur-Containing Amino Acids Concentrations in the Plasma --- p.117 / Chapter 3.4.1 --- Effects of Administration of Sulfur-Containing Amino Acids and Leucine on Methionine Concentrations in the Plasma --- p.117 / Chapter 3.4.2 --- Effects of Administration of Sulfur-Containing Amino Acids and Leucine on Cystine Concentrations in the Plasma --- p.119 / Chapter 3.4.3 --- Effects of Administration of Sulfur-Containing Amino Acids and Leucine on Taurine Concentrations in the Plasma --- p.119 / Chapter 3.4.4 --- Effects of Administration of Sulfur-Containing Amino Acids and Leucine on Leucine Concentrations in the Plasma --- p.122 / Chapter 3.4.5 --- Summary --- p.124 / Chapter CHAPTER 4 --- DISCUSSION AND CONCLUSIONS / Chapter 4.1 --- Effects of Sulfur-Containing Amino Acids and Leucine on Ascorbic Acid Concentrations in Mice --- p.126 / Chapter 4.2 --- Effects of Sulfur-Containing Amino Acids and Leucine on SVCT and GLUT3 Gene Expressions --- p.131 / Chapter 4.3 --- Sulfur-Containing Amino Acids Concentrations in the Plasma --- p.136 / Chapter 4.4 --- Conclusions --- p.140 / REFERENCES --- p.143

Constituents of the wine matrix, including ethanol, affect adsorption of sulfur volatiles on solid-phase microextraction (SPME) fibers, which can impact sensitivity and accuracy of volatile sulfur analysis in wine. Several common wine sulfur volatiles, including hydrogen sulfide (H2S), methanethiol (MeSH), dimethyl sulfide (DMS), dimethyl disulfide (DMDS), dimethyl trisulfide (DMTS), diethyl disulfide (DEDS), methyl thioacetate (MeSOAc), and ethyl thioacetate (EtSOAc), have been analyzed with multiple internal standards using SPME-GC equipped with pulsed-flame photometric detection (PFPD) at various concentrations of ethanol, volatile-, and non-volatile-matrix components in synthetic wine samples. All compounds exhibit a stark decrease in detectability with the addition of ethanol, especially between 0.0 and 0.5%v/v, but the ratio of standard to internal standard was more stable when alcohol concentration was greater than 1%. Addition of volatile matrix components yields a similar decrease but the standard-to-internal-standard ratio was consistent, suggesting the volatile matrix did not affect the quantification of volatile sulfur compounds in wine. Non-volatile wine matrix appears to have negligible effect on sensitivity. Based on analyte:internal standard ratios, DMS can be accurately measured against ethyl methyl sulfide (EMS), the thioacetates and DMDS with diethyl sulfide (DES), and H₂S, MeSH, DEDS, and DMTS with diisopropyl disulfide (DIDS) in wine with proper dilution. The developed method was then used to quantify sulfur compounds in 21 various California wines. H₂S and MeSH were found in higher concentrations in white varietals, while DMS was slightly higher in red varietals, particularly cabernet sauvignon and merlot. Trace amounts of DEDS and MeSOAc were found in almost all wines. DMS and DMTS were found in all wines, in some instances above reported thresholds. / Graduation date: 2012

This thesis is the use of commercially available methyl 2-iodobenzoate as the starting material and was prepared into iodine - oxazoline compound 118. Then, we undergo copper-catalyzed cross-coupling reactions of compound 118with thiols, and were readily facilitated to afford the corresponding desired products 127¡B136 in good to excellent yields. This method not only modified short- comings of that adding strong base to synthesis of sulfur-oxazoline ligands in past years but also has a good yield performances, the yield is 70 -87%. And we will use this strategy to undergo one pot reaction of carbon-sulfur coupling in future. In the end, we used new sulfur-oxazoline ligands127¡B128 in the Pd-catalyzed asymmetric alkylation of 1,3-diphenyl-2-propenyl acetate with dimethyl malonate. and reaction ee% were high, with the best result of 99% and 93% conversion.

Iron-sulfur (Fe-S) clusters are critical protein cofactors found in all life forms. In eukaryotes, a well-conserved biosynthetic pathway located in the mitochondria is used to assemble Fe-S clusters. Although proteins required for Fe-S cluster biosynthesis have been identified, their precise function and mechanism remain elusive. In this study, biochemical and biophysical methods are applied to understand molecular details for the core components of the human Fe-S cluster biosynthesis: Nfs1, Isd11, Isu2, and frataxin (Fxn). Nfs1 is a cysteine desulfurase that converts cysteine into alanine and transfers the sulfur to a scaffold protein Isu2 for Fe-S clusters. Fxn depletion is associated with the neurodegenerative disease Friedreich’s ataxia (FRDA), and results in a complicated phenotype that includes loss of Fe-S clusters. The results presented here provide the first in vitro evidence for a stable protein complex that exists in at least two forms: an inactive complex with Nfs1, Isd11, and Isu2 (SDU) components and an active form that also includes Fxn (SDUF). Fxn binding dramatically changes the catalytic efficiency (kcat/KM) of Nfs1 from 25 to 10,100 M-1s-1 and enhances the rate of Fe-S cluster biosynthesis 25 fold. Oxidizing conditions diminish the levels of both complex formation and Fxn-based activation, whereas Fe2 further stimulates Nfs1 activity. Mutagenesis coupled to enzyme kinetics indicate that one of the three conserved cysteines (C104) on Isu2 accepts the sulfane sulfur from Nfs1 and that this transfer event likely requires prior binding of Fxn. In vitro interrogation of FRDA I154F and W155R and related Fxn variants revealed the binding affinity to SDU followed the trend Fxn ~ I154F > W155F > W155A ~ W155R. The Fxn variants also have diminished ability to facilitate both sulfur transfer and Fe-S cluster assembly. Fxn crystallographic structures reveal specific rearrangements associated with the loss of function. Importantly, the weaker binding and lower activity of the W155R variant compared to I154F explains the earlier onset and more severe disease progression. Finally, these experimental results coupled with computational docking studies suggest a model for how human Fxn functions as an allosteric activator and triggers sulfur transfer and Fe-S cluster assembly.

Air pollution by sulfur dioxide is of great concern due to its harmful effects on environment, human beings, fauna and flora. Fossil-fuel-fired power plants are one of the major sources of SO2 emissions. Typically the concentration of SO2 in the flue gases of these plants is in the range of 2000 to 20000 ppm. Flue gas desulfurisation is one of the widely practiced strategies to control SO2 emissions. Aqueous phase oxidation of sulfur dioxide catalysed by carbonaceous particles is an attractive alternative to the conventional processes for flue gas desulfurisation because, amongst other reasons, sulfuric acid, the product of aqueous phase oxidation, finds extensive application in industry. In the literature it has been reported that sulfuric acid affects the solubility of sulfur dioxide and that activated carbon catalyses aqueous phase oxidation. However there is hardly any report on the systematic evaluation of the mechanism of the heterogeneous aqueous phase oxidation of sulfur dioxide which takes into account among other factors, the effect of sulfuric acid on the solubility of SO2 (particularly, at low levels of SO2 and sulfuric acid concentrations). Therefore the objective of the present work is to evaluate systematically the aqueous phase oxidation of SO2 in ppm levels with activated carbon as catalyst in a three-phase agitated slurry reactor and to model rigorously the solubility of SO2 in ppm levels in dilute sulfuric acid solutions and to estimate the concerned parameters experimentally. Strong effect of dilute concentrations of sulfuric acid on the solubility of SO2 is analyzed in terms of the influence of the acid on the equilibrium concentrations of the ionic species (HSO3¯ and SO4¯2 formed from the hydrolysis of SO2 (aq) and the dissociation of H2SO4 respectively) in SO2 - dil. H2SO4 systems. The analysis leads to a general expression relating the partial pressure of SO2 in the gas phase to the concentration of total dissolved SO2 and the concentration of sulfuric acid in the solution. Simple equations are obtained from the general expression for the cases of zero and high concentrations of sulfuric acid in the system, which in turn lead to direct experimental determination of the parameters, Henry's law constant and the equilibrium constant of hydrolysis of SO2 (aq). The developed model predicts the present experimental data as well as the data reported in the literature very closely. The dissolution of SO2, the hydrolysis of SO2 (aq) and the dissociation of H2SO4 are found to be instantaneous. From the dependency of the parameters on temperature, the heat of dissolution of SO2 is determined to be -31.47 kJ mol"1 and the heat of hydrolysis to be 15.69 kJ mol"1. The overall heat of solubility of sulfur dioxide is therefore -15.78 kJ mol"1. Preliminary reaction experiments have clearly indicated that SO2 (aq) does not react and HSO3¯ is the only reactant for aqueous phase oxidation of sulfur dioxide catalysed by activated carbon. The non-reactant SO2 (aq) deactivates the oxidation reaction by competing with HSO3¯ for adsorption on the active sites of the catalyst particles. However the catalyst particles become saturated with SO2 (aq) beyond a certain value of its concentration (saturation limit), which depends on temperature. A mechanism is proposed based on these observations to develop a rate model. The rate model also takes into account the effect of the concentration of the product sulfuric acid on the solubility of sulfur dioxide. The model predicts first order in HSO3¯ , half order in dissolved oxygen and a linear deactivation effect of 5O2(ag). The oxidation reaction is evaluated experimentally at various levels of the operating variables such as temperature and the concentrations of sulfur dioxide and oxygen in the inlet gas. In all experiments a pseudo steady-state region is observed where the gas phase concentration of SO2 reaches a steady value but the concentrations of HSO3¯ and total S (VI) in the liquid phase continue to change. Pseudo steady-state considerations lead to the determination of the initial estimates of the parameters of the rate model namely, the rate constant and the deactivation constant. These parameters are estimated from the transient profiles of the product (sulfuric acid) by solving the model equations by Runge-Kutta method along with Marquardt's non-linear parameter estimation algorithm. The predictions of the model with the estimated parameters match very well with the experimentally observed concentration profiles of S(VI) and HSO3 in the liquid phase and SO2 in the gas phase. The deactivation constant in the saturation range is independent of temperature and is 0.27, which indicates that the intrinsic rate constant is about four times greater than the observed rate constant. From Arrhenius equation-type dependency of the parameters on temperature, the activation energy for the oxidation reaction is determined to be 93.55 kJ mol"1 and for deactivation to be 21.4 kJ mol"1. The low value of activation energy for deactivation suggests a weak dependency of the deactivation on temperature, which perhaps is due to the weak nature of the chemisorption of SO2 (aq) on carbon.