This report describes a kinetic study of the thermal decomposition of methyl disulfide. The study was made as a contribution to the chemistry of organic sulfur compounds. The homogeneous decomposition was studied by the static method in an all-glass apparatus. It was followed by observation of the accompanying pressure changes and by analysis of the reaction mixture at various stages of the reaction. Several new analytical methods were developed for this analysis. The experimental conditions were varied by varying the temperature of the decomposition, the pressure of the reactant, and the surface to volume ratio of the reaction vessel, and by adding various substances to the reacting system. The experimental results show that the reaction is composite: (1) Initially a fraction of the reactant disulfide adsorbs on the surface of the pyrex reaction vessel at a rate which agrees with the theoretical rate for a collision mechanism. (2) There follows an induction period during which the disulfide does not decompose. (3) The first decomposition is into methyl mercap-tan and a non-volatile product believed to be a thiofor-maldehyde polymer. The suggested overall reactions are: CH₃-S-S-CH₃ → CH₃SH + CH₂=S n CH₂=S → (-CH₂-S-)n (4) A later, competing, process produces hydrogen sulfide, ethylene, free sulfur and polysulfides. It is possible that the carbon disulfide formed is produced by this reaction, and it is probable that the thioaldehyde polymer is decomposed. The overall unbalanced reactions may be written: CH₃SSCH₃ + ((CH₂S)n?) → H₂S + C₂H₄ + S + (CS₂?) + (?) CH₃-S-S-CH₃ + Sₓ → CH₃-Sₓ -CH₃ (5) Secondary reactions continue long after the disulphide has been used up. The major process appears to be the degradation of the postulated polythioformaldehyde to hydrogen sulfide and possibly to carbon disulfide and ethylene. Degradation of the polysulfides appears to occur also, and there may well be further secondary reactions. The nature of the various component processes have been discussed in some detail, and lines of further research have been suggested. The structure of disulfides and polysulfides and the bonding of organic sulfur compounds have been discussed. / Science, Faculty of / Chemistry, Department of / Graduate

High intensity mercury arc light sources were constructed for the investigation of Raman spectra. Raman tubes for liquids and gases were made and used for the study of the Raman Effect in liquid and gaseous carbon disulfide. The spectrum of liquid CS₂ was obtained using exposure times ranging from three minutes to two hours. The two principal Raman bands and one companion line for each band were observed and measured to an accuracy of within±0.5 cmˉ¹. The values found for the frequency shifts agree, within experimental error, with those of Langseth, Sorensen and Neilsen( 24). The spectrum of gaseous CS₂ was obtained with the gas at three atmospheres pressure and exposure times of twelve to thirty hours. Three previously unreported lines were observed in addition to the band reported by Imanishi(20) at 655 cmˉ¹. Their frequencies are compared below with those observed in the spectrum of liquid CS₂. (Formula omitted) / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Thesis advisor: Abhishek Chatterjee / Thesis advisor: Eranthie Weerapana / EGF signaling activates multiple pathways within the cell that lead towards proliferation, rendering this pathway of interest for cancer therapy. Recent studies focused on triple-negative breast cancer have shown that EGF-induced tumorigenesis strongly correlates with the up-regulation of FABP5, which shuttles fatty acids from the cytoplasm of cells to the nucleus. Our work began with the identification of redox active cysteine residues upon EGF activation in situ using a caged electrophile to perform live cell labeling. In these studies, the C120 residue of FABP5 was identified as a cysteine with high redox activity and thus became a subject of further interest. The characterization of redox active cysteine residues yields important information about protein structure and function. We have confirmed these results via in-gel fluorescence and developed fluorescence assays to probe the significance of C120 and C127 in FABP5. Two fatty acids were chosen based on their conformation in the FABP5 binding pocket. Upon the addition of a fatty acid, wild type protein showed a decrease in fluorescence indicating that the fatty acids were outcompeting the fluorophores used. Future studies will investigate both wild type and mutant versions of FABP5 with emphasis on determining potential disulfide bond formation via phosphoproteomics and western blotting techniques. / Thesis (MS) — Boston College, 2016. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

Disulfide bonds play crucial roles to predict the three-dimensional structure and the function of a protein. This thesis develops two algorithms to predict the disulfide bonding state of each cysteine in a protein sequence. These methods are based on the multi-stage framework and the multi-classifier of the support vector machine (SVM). The first algorithm achieves 94.0% accuracy of cysteine state prediction for dataset PDB4136, but in some datasets the results are not as good as our expectation. Thus the second algorithm is designed to improve the predicting ability for the proteins which have oxidized and reduced cysteines simultaneously. In addition, a new training strategy is also developed to increase the prediction accuracy. It appends the probabilities which are obtained from the SVM to the existing features and then starts a new training procedure repeatedly to get better performance. The experiments are performed on the datasets derived from well-known databases, such as Protein Data Bank and SWISS-PROT. It gets 94.3% accuracy for predicting disulfide bonding state on dataset PDB4136, which gets improvement 3.6% compared with the previously best result 90.7%.

£\-Bungarotoxin (£\-Bgt), a £\-neurotoxin from Taiwan banded krait (Bungarus multicinctus), consists of a single polypeptide chain of 74 amino acid residues cross-linking with five disulfide bonds. In order to explore the structural dependence of the disulfide bonds in the toxin molecule, the mutants with deleting one out of the five disulfide bonds were prepared by site-directed mutagenesis. The mutated and wild-type cDNAs were subcloned into the expression vectors pET14b as well as pET32a(+), and then transformed into Escherichia coli, BL-21(DE3). The recombinant proteins derived from pET14b expression system were isolated from inclusion bodies of E. coli, and refolding into their folded structure in vitro. Alternatively, the proteins derived from pET32a(+) system were expressed as a fusion protein and purified on a His-Bind resin column. Moreover, the recombinant proteins were further purified using a reverse phase column, and the homogeneity of recombinant proteins was determined by SDS-PAGE analyses. Noticeably, the refolding reaction was beneficially achieved by deleting the disulfide bond Cys29-Cys33. Although SDS-PAGE analyses showed that the recombinant proteins were homogeneous in molecular weight, several disulfide isomers appeared in each protein preparation as revealed by native gel analyses. These observations suggest that the formation of disulfide bonds and folding of£\-Bgt may pass through multiple pathways.

This work has studied several aspects of the physiology of the animal-colonizing species Campylobacterjejuni, Helicobacter pylori. Wolinella succinogenes and Arcobacter butzleri. C. jejuni and H pylori were found to be obligate microaerophiles and W.succinogenes an anaerobe. A. butzleri was found to be an aerobe able to grow anaerobically. Comparative analyses of the responses of C. jejuni, H pylori and W. succinogenes to various oxygen concentrations were investigated using transcriptomics and genes differentially expressed at higher oxygen concentrations were identified. At the time of this study no microarrays were available for A. butzleri. These comparative studies provided a better understanding of bacterial adaptation to and interaction with their environment. Several enzymes involved in oxireduction processes, including disulfide reductases, were upregulated under oxidative stress. Disulfide reductases of host-colonizing bacteria are involved in the expression of virulence factors, resistance to drugs, and elimination of toxic compounds. CXXC and CXXC-derived motifs are present in the active sites of disulfide reductases and are essential for the catalysis of these redox reactions. Large-scale genome analyses of 281 prokaryotes identified CXXC and CXXC-derived motifs in each microorganism. The total number of these motifs showed correlations with genome size and oxygen tolerance of the prokaryotes. Specific bioinformatic analyses served to identify putative disulfide reductases in the four Campylobacterales species. The project investigated the involvement of these enzymes in resistance to the antibiotic metronidazole, cadmium detoxication and pathogenesis. The activities of disulfide reductases were modulated by the presence of metronidazole, and its reduction was inhibited by the presence of disulfide reductase substrates. In addition, proteins involved in oxireduction of the low redox potential ferredoxin were downregulated in metronidazole resistant strains, suggesting that ferredoxin is involved in the resistant phenotype. Cellular processes and pathways regulated under cadmium stress included fatty acid biosynthesis, protein biosynthesis, chemotaxis and mobility, the tricarboxylic acid cycle, protein modification, redox processes and heat shock response. Notably, the data provided evidence for a role of oxireduction processes in the development of metronidazole resistance and the detoxication of cadmium. Furthermore, a method was developed to identify thiol disulfide oxidoreductases in the four Campylobacterales. The results suggested that H pylori contained a novel disulfide bond formation system. Investigation of their potential involvement in virulence or colonization indicated that the putative thiol disulfide oxidoreductases HP0231 and HP0595 are related to the colonization efficiency ofH pylori. Finally, the only known disulfide reduction system in Campylobacterales, the thioredoxin system, was investigated in more detail. Phylogenetic analyses of the thioredoxin reductases TrxB1 and TrxB2 of the four bacteria were performed. The phylogenetic features of the TrxB2 suggested a special role for this enzyme in the physiology of these bacteria; thus, the enzyme was investigated further in H pylori. TrxB2 was found to be an NADPH reductase, possibly involved in important oxireduction processes within the cell.

Thesis (M. Phil.)--University of Hong Kong, 1997. / Includes bibliographical references (leaf 95-97).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1983. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

The objects of this research were twofold: 1. To develop apparatus and experimental techniques to shorten the exposure times in the study of the vibrational Raman effect of liquids and liquids in the solid state. 2. To use the above in the investigation of the vibrational Raman spectra of the liquid and solid states of Carbon Disulfide. Concurrently, other workers were investigating the infrared absorption spectrum of CS2. The two projects, when integrated, should give a reasonably complete basis for the description of the CS2 molecule. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The infrared absorption spectrum of carbon disulphide in the vapour state has been remeasured in the region from 2 to 15 microns. A total of six bands were measured in the region less than 15 microns. They were located at 3.38, 3.51, 4.29, 4.58, 6.52, and 11.4 microns. The measurements were made with a Perkin-Elmer spectrometer with a D.C. breaker type amplifier and Brown recorder. Cell lengths up to 100cm were employed. The wave lengths of the observed absorption hands are given in a table, and graphs are shown of the percentage transmission over the wave drum setting of the spectrometer. Phase shifting thyratron circuits, suitable for the accurate control of conditions of the absorbing media, are discussed. Of interest are the measurements of the structure of the Ʋ ₃ band at 1535 cmˉ¹. The side band located at the long-wave length side of the Ʋ₃ band is due to the isotopic effect produced by C¹³. The bands obtained are such as to support the conclusion that carbon disulphide is a linear triatomic molecule. / Science, Faculty of / Physics and Astronomy, Department of / Graduate