The thermally induced reaction of halogenated ethylenes on the α-Cr₂O₃ (101̅2) single crystal surface results in the formation of gas phase hydrocarbons including acetylene, ethylene, butadiene, and dihydrogen, and deposition of surface chlorine adatoms. No surface carbon or combustion products are observed in any reactions indicating no thermally induced C-C bond cleavage occurs and surface lattice oxygen is not incorporated into surface intermediates. Thermal desorption spectroscopy indicates that in all halogenated ethylene reactions acetylene is the major product, regardless of the reaction scheme. The surface reactions of halogenated ethylenes are proposed to proceed through C-X (X=halogen) bond cleavage to form surface halogen adatoms and surface C2 hydrocarbon fragments. Halogen adatom deposition affects reaction barriers to hydrocarbon formation, and eventually shuts down surface chemistry. Photoemission and near edge x-ray absorption fine structure spectra show that all studied reactants undergo some C-X bond cleavage upon low temperature adsorption forming adsorbed C2 fragments and halogen adatoms. Photoemission for each reaction system shows at least two C1s features (283.0-286.0 eV) and two Cl2p features (2p_3/2=198.0-201.0 eV) with higher binding energy features associated with molecularly intact halogenated ethylenes and lower binding energy features associated with dissociated surface species. Near edge x-ray absorption fine structure spectra taken, corresponding to photoemission spectra, indicate the occurrence of C1s→π∗ transitions, indicating intact π-systems are present. Heating the surface results in a reduction in intensity of higher energy photoemission and near edge x-ray absorption fine structure indicative of a decrease in surface C-X bonds. / Ph. D.

Proteomics is defined as a tool to explore how proteins control and regulate important molecular and physiological processes. Further, peptide-centric approaches, or bottom-up methods, provide more comprehensive coverage of a proteome compared to whole-protein approaches. This body of work assesses the technical feasibility of several bottom-up proteomics technologies applied to Arabidopsis thaliana, including gel-based methods, those that require peptide derivitization, and those that do not. Selected-reaction monitoring (SRM) for targeted proteomics, and data-independent acquisition (MSE) was also evaluated. In addition to assessing the capabilities of these technologies, we then applied them to the context of uncovering new insights into the flavonoid biosynthetic pathway and the auxin and ethylene signaling pathways. Chapter one provides background information related to secondary metabolism, phytohormone signaling, and the status of proteomics in plants. In Chapter 2 and Appendix A, we establish the methodology to apply traditional and DiGE-based 2D-GE strategies to global proteomics in Arabidopsis. Our results suggest that while 2D-GE is applicable to Arabidopsis, there are practical and conceptual limitations that must be understood. Further, our results suggest that pertubations in the flavonoid pathway do not affect the abundance of proteins in Arabidopsis seedlings, roots, or flowers that can be studied using 2D-GE and DiGE. Additionally, we demonstrated the first parallel comparison of the effects of auxin and ethylene on the Arabidopsis root proteome and observed no overlap among the proteins regulated by the two phytohormones, at least for the most abundant proteins observed by 2D-GE. Chapter 3 explores the efficacy of selected reaction monitoring for relative peptide quantification in Arabidopsis roots. Our results suggest that while the technology parallels application in yeast and humans, there are substantial analytical challenges that much be addressed. In Chapter 4 we explore the MSE data acquisition scheme for global proteomics in Arabidopsis. We observe that treatment with exogenous auxin affects the abundance of many proteins representing diverse biological processes. Interestingly, we observe minimal overlap among genes and proteins regulated by exogenous auxin. Appendix B explores the efficacy of iTRAQ labeling for relative peptide quantification in Arabidopsis roots. / Ph. D.

A report that the ethylene oxide fumigation of animal diets reduced their nutritive value has prompted a more detailed study of the reactions of this commercially-used fumigant. It has been demonstrated that the 24-hour fumigation of commercial casein, egg albumin and lactalbumin with ethylene oxide greatly reduced the ability of these proteins to support the growth of weanling rats when the proteins were fed as 9% of a purified diet as the sole source of amino acid nitrogen. Thorough drying of the proteins reduced the extent of subsequent fumigation damage. The nutritional quality of the three proteins was completely restored by the supplementary feeding of L-histidine-HCl, DL-methionine, and L-lysine-HCl, or, in some cases, only one or two of these amino acids. Microbiological assay confirmed a reduction in the biological availability of 11% to 83% of the histidine, 6% to 55% of the methionine and 51 to 92% of the lysine, depending on the protein and the amount of moisture present during fumigation. Histidine was generally the most labile amino acid and lysine the least labile. Additional amino acids appeared to be affected when an hydrolysate of casein was fumigated. The ethylene oxide fumigation of soybean alpha protein improves its growth-promoting quality for the rat. Evidence is presented that fumigation inactivates the heat-labile proteinaceous growth inhibitor, long recognized as a component of soybean protein. Chemical justification for the destructive action of ethylene oxide on the biological value of histidine, methionine, and certain B-vitamins was sought by reacting model compounds in aqueous solution with the fumigant and identifying the products. At 25°C. and atmospheric pressure ethylene oxide readily hydroxyethylates tertiary as well as primary and secondary amine nitrogen and also the sulfur of thioethers. Imidazole and histidine yield the 1,3-bis-(2-hydroxyethyl)imidazolium derivatives; nicotinamide, nicotinic acid, and pyridine yield the corresponding N-(2-hydroxyethyl)pyridinium compounds; and N-acetylmethionine is converted to s-(2-hydroxyethyl)-N-acetylmethionine, thetin. The reaction of ethylene oxide with amino acids results in hydroxyethylation of the primary amino groups but no esterification of carboxyl groups was observed. The extent of ethylene oxide-imidazole reaction in fumigated proteins could be determined colorimetrically. In the presence of ethylene oxide the mercapto group of cysteine appears to become doubly alkylated to produce a sulfonium compound which causes a flaccid paralysis, respiratory failure and death when injected subcutaneously into weanling rats. The structure of the compound bears certain similarities to other synthetic spasmolytics. Evidence is presented that the reaction of ethylene oxide with pyridoxine, riboflavin and folic acid involves the hydroxyethylation of tertiary heterocyclic nitrogens. A striking resemblance was observed between the alkylating capacity of ethylene oxide and the sulfur and nitrogen mustards. New compounds described are 1,3-bis-(2-hydroxyethyl)imidazolium chloride; N¹-(2-hydroxyethyl)nicotinic acid, betaine; and N-(2-hydroxyethyl) nicotinic acid chloride. N-(2-hydroxyethyl)nicotinamide chloride was also crystallized and its melting point found to be 14 degrees centigrade higher than previously reported in the literature. Other reaction products were studied in solution or as solid adducts of reinecke's salt or phosphotungstic acid. The proteolytic activity of chymotrypsin was progressively reduced by exposure of the cystalline enzyme to ethylene oxide vapor or by treatment of the enzyme in aqueous solution with the fumigant. However, treatment of chymotrypsin in aqueous solution with ethylene oxide did not impair its ability to hydrolyze p-nitrophenyl acetate. Likewise, the imidazole groups of native chymotrypsin appear to be protected from the hydroxyethylating action of ethylene oxide. Denaturing the protein in 8 M urea uncovered the imidazole groups and permitted reaction with the fumigant. On the basis of these studies it is felt that the effect of existing commercial ethylene oxide fumigating processes on the nutritive value of foods and feedstuffs bears closer investigation. / Ph. D.

Poly(ethylene terephthalate) (PETE) packaging is becoming an increasingly popular choice of packaging material for milk, but has the disadvantage of releasing odorous acetaldehyde into food matrices. Sensory detection group thresholds for acetaldehyde in whole, low fat and nonfat unflavored milks were 3939, 4020, and 4040 ppb respectively with no significant difference due to fat level. Chocolate flavored milk and spring water showed detection thresholds levels for acetaldehyde of 10048 and 167 ppb respectively. This information assisted in determining if acetaldehyde migration from the package to the product would influence the flavor of the product. Whole milk was packaged in glass, high density polyethylene (HDPE), amber PETE, clear PETE, and clear PETE with UV light block and was exposed to fluorescent light of 1100-1300 lux (100-120 FC) at 4oC for 18 days. Sensory and chemical analysis and was done on milk from all containers over a period of 18 days. Emphasis was on oxidation, acetaldehyde and lacks freshness off-flavors and byproducts. All volatile flavor compounds studied (acetaldehyde, pentanal, dimethyl disulfide, and hexanal) were increased in light-exposed milk samples. Amber PETE showed the least amount of oxidation off-flavor, while clear PETE with UV block showed significantly less oxidation off-flavor than glass, clear PETE or HDPE on day 7 and 18. Acetaldehyde was not detected by sensory analysis in either light-exposed or light-protected samples. Chemical analysis showed relative acetaldehyde levels in glass (2220 ppb), HDPE (1265 ppb), amber PETE (3397 ppb), clear PETE (2930 ppb), and clear PETE with UV light block (1754 ppb) were all below concentrations found for human flavor threshold. / Master of Science

Ethylene adsorption was studied by use of DFT/B3LYP with basis set 6-31G(d,p) in Gaussian&lsquo / 03 software. It was found that ethylene adsorbs molecularly on the Ni13 nanocluster with &amp / #960 / adsorption mode. &amp / #960 / adsorption mode is studied for the Ni10 (1 1 1), Ni13 (1 0 0) and Ni10 (1 1 0) surface cluster as well. Relative energy values were calculated as &amp / #8722 / 50.86 kcal/mol, &amp / #8722 / 20.48 kcal/mol, &amp / #8722 / 32.44 kcal/mol and &amp / #8722 / 39.27 kcal/mol for Ni13 nanocluster, Ni10 (1 1 1), Ni13 (1 0 0) and Ni10 (1 1 0) surface cluster models, respectively. Ethylene adsorption energy was found inversely proportional to Ni coordination number when Ni10 (1 1 1), Ni13 (1 0 0) and Ni10 (1 1 0) cluster models and Ni13 nanocluster were compared with each other. DFT/B3LYP and basis set of 86-411(41d)G in Gaussian&lsquo / 03 was used to investigate Ni55 nanocluster. Ethylene adsorption on Ni55 nanocluster was studied by means of equilibrium geometry calculations with &amp / #960 / adsorption modes for two different coordination numbers as 6 and 8. The related adsorption energies were approximately found as -22.07 and -14.82 kcal/mol for these coordination numbers of surfaces, respectively. In addition, the binding energies stated in literature that are for Ni2 dimer and Ni13 nanoclusters were considered together with our binding energy results for Ni55 nanocluster. Accordingly, when a correlation line was drawn and the intercept of binding energies was obtained against the value of &amp / #8213 / n&amp / #8722 / 1/3&amp / #8214 / where n is the number of atoms in the cluster / the result of interception gives a good estimation for bulk nickel binding energy at infinite &amp / #8213 / n&amp / #8214 / . This interception result was found as 4.58 eV/atom where the experimental value is reported as 4.45 eV/atom for bulk in the literature. Ehtylene hydrogenation mechanisms were also investigated in terms of the resultant geometries and total energy required for the related mechanism steps.

Novel poly(ethylene isophthalate) (PEI) and poly(ethylene terephthalate) (PET) polymers containing terminal units derived from sodio 3-sulfobenzoic acid (SSBA) were synthesized using catalyzed melt polymerization techniques. Various concentrations of the ionic end group, SSBA, were successfully incorporated in a telechelic fashion. For comparison, polyesters containing telechelic alkyl groups with controllable molecular weights were also synthesized. Furthermore, ionic copolymers of dimethyl isophthalate and trans-cyclohexane dicarboxylate, dimethyl isophthalate and dimethyl terephthalate were synthesized to study the influences of polarity and rigidity of the polymer chain backbone on material properties. Novel branched polyester ionomers using trimellitic anhydride were also prepared. In addition to modifying the polymer compositions, PET ionomers were blended with zinc stearate to investigate the effect of plasticizer on the melt processibilty of the ionomers. FTIR spectroscopy, which was used to quantify the sulfonate end groups for all of the ionomers, indicated an absorbance peak for the S-O stretching mode between 600-700 cm⁻¹. ¹H NMR spectroscopy was used to confirm the structure of the ionic and non-ionic polyesters, as well as to verify the presence of the terminal groups. By systematically varying the chemical structure of these ionomer model systems (i.e., altering the contents of ionic functional groups), detailed characterizations were carried out, wherein the ionic interactions/aggregations in the ionomers were found to play an important role in the resulting material properties. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) measurements were performed to study the effects of ionic groups and oligomer composition on the thermal properties of the polyesters. The glass transition temperatures of the ionomers revealed that the ionic interaction helped to maintain the structural integrity of the polymer chains, thus limiting their mobility. The dilute solution viscosity behavior of the ionomers exhibited upward curvature, which is a key characteristic of an ionomer. In PEI ionomers, the ionic aggregates formed at lower temperatures (<150 °C), while at higher temperatures (>150 °C), the ionic aggregations dissociated and behaved similarly to oligomers with lower molecular weights. Dodecanol was used as an effective end-capper to control the molecular weight of the non-ionic polyesters. In addition to telechelic ionic PEI and PET homopolymers, copolymers of poly(ethylene isophthalate-co-trans-1,4-cyclohexane dicarboxylate) (PEI-co-trans-CHDC) and poly(ethylene isophthalate-co-terephthalate) (PEIT) telechelic ionomers were also synthesized and characterized. Introducing trans-1,4-cyclohexane dicarboxylate into PEI ionomers decreased the polarity and packing regularity of the polymer chains. Also, the kinked-structure of dimethyl isophthalate reduced the regularity of the polymer chains in PET ionomers, thus reducing their propensity for rapid crystallization. Crystallization kinetics were studied for both ionic and alkyl telechelic polyesters, and resulting data revealed that the nature of the endgroup had a dramatic effect on crystallization from the melt state. The catalyst residue in the polymers also affected the crystallization rate for both ionic and non-ionic polyesters. With regard to the ionomers, antimony catalyst interacted with ionic aggregates, further increasing the crystallization rate. Branched PEI and PET ionomers showed an increase in melt strength. After blending with zinc stearate, the melt viscosity of the PET ionomers dropped dramatically. / Master of Science

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No description available.

In this work the morphology, crystallization and melting behavior of novel Dow Chemical propylene-ethylene copolymers were investigated. The incorporation of ethylene units into a polypropylene chain resulted in the decrease in crystallization, melting and glass transition temperatures and overall crystallinity. Based on the shape of heat capacity curves and the dependence of the melting temperature offset on ethylene content, it was concluded that copolymers prepared using different catalyst systems exhibited different ethylene sequence length distributions. The behavior of Dow Chemical propylene-ethylene copolymers was compared to that of copolymers prepared using traditional metallocene and Ziegler-Natta catalysts. The catalyst system used in the preparation of these new copolymers is similar to a metallocene catalyst system. It was demonstrated that ethylene defects are partially included in the polypropylene crystal. The thermodynamic heat of fusion at the equilibrium melting temperature decreased by 44% with an increase in ethylene concentration from 0 mol% to 21.2 mol%. On the basis of calorimetric and density data, the inclusion model based on the Sanchez-Eby crystallization theory was shown to be applicable for the evaluation of the degree of crystallinity. At the same time, inadequacies were found in application of the rigid amorphous fraction model to these copolymers. The formation of gamma-phase crystals was shown to be favored by both an increase in the ethylene content and a decrease in the crystallization rate. Increase in the ethylene content was shown to lead to a decrease in the density, length and thickness of alpha-phase crystals. It was also demonstrated that the cross-hatching morphology is present in all propylene-ethylene copolymers. / Ph. D.