This paper deals with the problem of setting up an infrared spectrometer and recorder under suitable conditions, and in applying the instrument to the absorption spectrum of CS₂ in the vapor phase. Six absorption bands, corresponding to the fundamental vibration V₃ at 1535 cm⁻¹, the difference band V₃ - V₁, at 877 cm⁻¹, and the four combination bands V₁ + V₃ at 2185 cm⁻¹, V₃ + 2V₂ at 2332 cm⁻¹, V₃ +2V₁ at 2838 cm⁻¹, and V₁ + V₃ + 2V₂ at 2959 cm⁻¹ have been examined. Using this value for V₃, a better agreement between the force constant of the C S bond, calculated from V₃, with that calculated from V₁, is obtained. The work is to be continued. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

No / Methodology for the efficient and facile synthesis of glycosyl disulfides is reported. A one-pot procedure employing mild conditions using diethyl azodicarboxylate is described to synthesise a series of glycosyl disulfides in excellent yields.

Thesis advisor: Eranthie Weerapana / Disulfide-bonding cysteine residues perform critical roles in the structural stabilization and redox regulation of protein function. Secreted proteins are often enriched for structural disulfide bonds conferring conformational stability in the oxidizing extracellular environment. The controlled formation of disulfide bonds in secreted proteins is regulated in the endoplasmic reticulum (ER) by the protein disulfide isomerase (PDI) family. To investigate disulfide-bond formation in the ER, quantitative chemical-proteomic methods were coupled to subcellular-fractionation-based ER enrichment. Cysteine reactivity studies identified highly reactive post-translationally modified cysteine residues including disulfide-bonding cysteines. Upon discovering a highly reactive population of traditionally oxidized cysteines, the percentage of oxidation for cysteines localizing to the ER was determined. Next, ER function was chemically perturbed to evaluate changes to cysteine oxidation following upregulation of the unfolded protein response (UPR). Disulfide bond formation was specifically disrupted in the ER by CRISPR-Cas9-mediated PDIA1 and PDIA4 knockout. The effects of PDI knockout on cancer cell phenotype and changes to cysteine oxidation states were evaluated. Finally, in vitro studies were performed to evaluate PDIA4 oxidase activity and identify potential PDIA4-selective inhibitors. In the future, the platforms developed within may be applied to profiling changes to cysteine oxidation in other biological systems such as other organelles and disease states. / Thesis (PhD) — Boston College, 2019. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

published_or_final_version / Chemistry / Master / Master of Philosophy

No description available.

?The body of this work spans both fundamental organometallic chemistry and the application of previously studied catalyst systems to produce new polymeric materials. The cone angle of triphenylphosphite was estimated to be 128 degrees by Tolman in the late 70s; however, metal complexes bearing this ligand undergo cis/trans isomerization via a mechanism indicative of greater steric requirements. X-ray crystallographic studies coupled with data compiled from the Cambridge Crystallographic Database, were used to more accurately calculate the steric demand of this wieldy used ligand to be approximately 140 degrees. Additionally, in depth kinetic studies of the interaction of furan ligands with electron deficient manganese and chromium metal centers were performed. Data collected from timescales ranging from minutes to microseconds was utilized to calculate the bond dissociation energy of both 2,3-dihydrofuran (DHF) and furan. The aromatic furan ligand was found to bind to the both metals 7-10 kcal mol-1 weaker than DHF. Additionally, the more electron rich chromium center was found to bind both ligands ?weaker than the manganese center implying a minimization of the M-L pie -back bonding interaction. Solution studies coupled with DFT calculations were utilized to estimate the extent that the furan ligand is dearomatized by approximately 50% upon interaction with the metal center. Application-based studies of the separation of polymer catalyst mixtures were also undertaken. The addition of the 1000 Dalton poly(isobutylene) arms to the salen ligand in (salen)CrCl complexes yielded a catalyst that could be extracted from the reaction mixture containing poly(cyclohexene carbonate) via the addition of heptane. Another approach, not requiring catalyst modification, utilized a secondary amine to facilitate the purification of the polymer product. The reaction of an amine with CO2 to form an ionic liquid resulted in the precipitation of the polymer while the catalyst and byproducts remained in the liquid carbamate phase. Both approaches provided improvements over the long standing method of precipitating the polymer using methanol and strong acid. Lastly, the previous work of the Darensbourg group utilizing (salen)CrCl catalyst to produce polycarbonates from CO2 and epoxides was employed to synthesized sulfur rich poly(thiocarbonate)s. The effects of both CS2 loading and temperature on the copolymerization of CS2 and cyclohexene oxide were studied. Optimal conditions of 1 equivalent of CS2 and 50 degrees C were found to selectively produce the desired polymeric material. The observation of multiple thiocarbonate as well as carbonate functionalities, led to a detailed study of the reaction byproducts to gain insight into the copolymerization process.

Sulfur-containing organic solvents or carbon disulfide have been used extensively in semiconductor, TFT-LCD, and synthetic fiber (viscous rayon) industries in the last decades. These compounds can easily be converted into reduced-sulfur ones which exhibit low odor threshold characteristics and arise public complaints once releasing into environments. This paper intended to oxide these compounds by both chemical and biological approaches for the purpose of odor reduction. The first topic was investigations on the oxidation of aqueous DMS (dimethyl sulfide) by using sodium hypochlorite as an oxidant. Results indicated that with an initial DMS concentration of 100 mg/L, it required only 0.75 min or 45 s to convert the DMS completely into its final oxidation product, DMSO2 (dimethyl sulfur dioxide). The required dosage of the oxidant was a little less than the theoretical value. In addition, it was found that initial pH of the batch reaction liquid be kept at around 8.2 for achieving a neutral final solution which emitted only a trace of gaseous chlorine and hydrochloric acid odors. The second one was a trail investigation on the biodegradation of gas-borne hydrogen sulfide and carbon disulfide by a trickling-bed biofilter packed solely with fern chips. Glucose and milk powder were used as main nutrients for microbial film development and enhancer for the biodegradation of sulfides. Results indicated that after an acclimation period of around two months, approximately 99 and 86% of the influent hydrogen sulfide (10-20 ppm) and carbon disulfide (20-60 ppm), respectively, could be removed with an empty bed retention time of around 63 s for the gas in the packed bed. Both neutral or acidic environments were suitable for the biodegradation reaction and the metabolites (mainly, sulfuric acid) could easily be removed from the chips by washing them with water. In the future, efforts should be done to increase the removal capacity of carbon disulfide.

Thrombospondin 1 (TSP1) is a 450 kDa homotrimeric multidomain glycoprotein with fundamental roles in many cell-cell and cell-matrix interactions. These varied, and sometimes conflicting, functions are mediated by specific domains in TSP1. One region with diverse biological roles is the Ca2+ binding loops (or type 3 repeats). The biological activity of this region is determined through a complex assembly of disulfide bonds linking structure and function. Disulfide interchange in a protein is usually very specific and quite slow, unless catalysed. I have found that protein disulfide isomerase (PDI) is expressed on the surface of platelets and endothelial cells in a reduced active conformation. The presence of enzymatically active PDI on the surface of TSP1-secreting cells suggests PDI is well positioned to catalyse disulfide interchange in, and regulate the structure/function relationships of, TSP1. PDI was observed to form disulfide-linked complexes with TSP1. Moreover, incubation of platelet or fibroblast TSP1 with PDI enhanced binding of an isomer-specific anti-TSP1 antibody whose epitope is in the Ca2+ binding loops. These findings suggest that PDI may mediate disulfide bond rearrangement in both the soluble and extracellular matrix-bound forms of TSP1. TSP1 is a tight-binding competitive inhibitor of neutrophil cathepsin G; however, incubation with PDI increased the Ki for the interaction ???10-14-fold. TSP1 bound platelet-derived growth factor (PDGF) tightly in the region of the Ca2+ binding loops and supported binding of PDGF to its receptor. PDI-mediated disulfide interchange in TSP1 ablated PDGF binding, indicating that PDI-catalysed disulfide interchange in TSP1 may modulate PDGF-TSP1 complex formation and the biological activity of PDGF. Finally, PDI-catalysed isomerization of TSP1 potently affected its cell adhesive properties. Treatment of TSP1 with PDI enhanced adhesion and spreading of endothelial cells through the ??v??3 integrin receptor to TSP1, by exposure of a cryptic RGD sequence. Thus, endothelial cell surface PDI may be a physiological regulator of RGD-dependent binding to TSP1. These data suggest that cell-surface PDI may regulate the disulfide-bonded structure and certain biological functions of TSP1. In conclusion, I propose a novel mechanism for the post-translational regulation of TSP1 structure/function, which in turn may regulate certain aspects of TSP1 in vascular biology.

Tübingen, Univ., Diss., 2003.

Disulfide bond formation is an essential process for the folding and biological activity of most extracellular proteins; however, it may become the limiting step when the production of these proteins is attempted in heterologous hosts such as Escherichia coli. The rearrangement of incorrect disulfide bonds between cysteines that do not normally interact in the native structure of a protein is carried out by disulfide isomerase enzymes. The disulfide isomerase present in the bacterial secretory compartment (the periplasmic space) is the homodimeric enzyme DsbC. The objective of this dissertation was to understand the key features of how DsbC catalyzes disulfide bond isomerization. Chimeric disulfide isomerases comprising of protein domains that share a similar function, or are homologous to domains of DsbC were constructed in an effort to understand the effect of the domain orientation in the dimeric protein, and the need for a substrate binding region in disulfide isomerases. We successfully created a series of fusion enzymes, FkpA-DsbAs, which catalyze in vivo disulfide isomerization with comparable efficiency to DsbC. These enzymes comprise of the peptide binding region of the periplasmic chaperone FkpA, which is functionally and structurally similar to the binding domain of DsbC but share no amino acid homology with it, fused to the bacterial oxidase DsbA. In addition, these chimeric enzymes were shown to assist in the initial formation of disulfide bonds, a function that is normally exhibited only by DsbA. Directed evolution of the FkpA-DsbA proteins conferred improved resistance to CuCl₂, a phenotype dependent on disulfide bond isomerization and highlighted the importance of an optimal catalytic site. The bacterial disulfide isomerase DsbC is a homodimeric V-shaped enzyme that consists of a dimerization domain, two α-helical linkers and two opposing catalytic domains. The functional significance of the existence of two catalytic domains of DsbC is not well understood yet. The fact that identical subunits naturally dimerize to generate DsbC has so far limited the study of the individual catalytic sites in the homodimer. In chapter 3 we discuss the engineering, in vivo function, and biochemical characterization chapter 3 we discuss the engineering, in vivo function, and biochemical characterization of DsbC variants covalently linked via (Gly3Ser) flexible linkers. We have either inactivated one of the catalytic sites (CGYC), or entirely removed one of the catalytic domains while maintaining the putative binding area intact. Our results support the hypotheses that dual catalytic domains in DsbC are not necessary for disulfide bond isomerization, but are important in terms of increasing the effective concentration of catalytic equivalents, and that the availability of a substrate binding region is a determining feature in isomerization. Finally, we have carried out initial studies to map the residues and sequence motifs that are recognized in substrate proteins that interact with DsbC. Although the main putative binding region of DsbC has been localized within the limits of the hydrophobic cleft that emerges from the interaction of the N-terminal domains of this enzyme, and, a few native substrates have already been identified, no information on the features of substrate proteins that are recognized by the enzyme has been reported. To address this problem, we have screened two different, 15 amino-acid random peptide libraries for binding to DsbC. We have successfully isolated several peptides with high affinity for the enzyme. Possible consensus binding motifs were identified and their significance in substrate recognition will be examined in future studies. / text