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In underground oil reservoirs, Hydrogen sulfide is usually found coexisting with the oil due to bacteria reduction over a long period of time. The amount of H2S in the oil varies from place to place around the globe. When the oil extraction process begins, the presence of Hydrogen sulfide becomes noticeable as drilling tools, piping and other equipment suffer from sulfide stress cracking, electrochemical corrosion and corrosion fatigue. For this reason, the oil industry invests millions of dollars per year trying to find better ways to reduce the amount of H2S in oil. An important part of the current investigations deals with brine (sea water)/oil mixtures. The reasons are two-fold: 1) one way of extracting the petroleum from the reservoir is by injecting brine into it and since it has a higher density than oil, the latter will be ejected up to the surface. Taking into account the complex fluid flow occurring within the reservoir it is easy to understand that some brine will also be present as part of the ejected fluid; 2) brine is already present in the reservoir, so independent of the extraction method used, there will be a brine/oil mixture in the ejected flow. When brine and oil have absorbed H2S under pressure in the reservoir and then suffer a decompression during the extraction process, a certain amount of H2S is released from the liquid phase. In order to have a better prediction of how much Hydrogen sulfide can be liberated a good understanding of H2S absorption by these liquids is necessary. The amount of gas a solvent absorbs is a function of pressure, original gas concentration and temperature as described by Henry's Law. The purpose of this thesis is to experimentally analyze how much of the corrosive gas is absorbed into different brine/oil mixtures, and brine and oil, separately. In order to find sufficient data for a thorough analysis, different reservoir simulation scenarios were created. The liquids were mixed from pure brine to pure oil, resulting in 33% and 66% water cuts. Data were obtained at 2 pressures of 20atm and 70atm at room temperature. H2S concentration was also a variable, changing the original gas concentration through different values: 50, 100, and 300ppm. These experiments were conducted in an autoclave system and will better explain the hydrostatic process that occurs inside the reservoir. It was found that throughout all the water cuts, the role that total pressure plays in the absorption phenomena is of less importance as the original H2S concentration is increased. In the same manner it was observed that the highest mass-absorption ratios are always found between 50 and 100ppm and the lowest at 300ppm, this is observed for all water cuts and total pressures. Another important finding was that the ability to absorb the corrosive gas decreases as the original H2S concentration increases and this proves to be true for all water cuts and system pressures. After conducting these different reservoir scenarios, tests were conducted to simulate 300m of the horizontal section of the pipe that connects the head of the well with the platform. This was done with a high pressure 300-meter long loop. It was found that the corrosive gas is absorbed at a higher rate when there is a flow, opposite to a hydrostatic case. Henry's Law constant was identified for each water cut and each pressure, however, the test procedure could not be validated since the gas being studied was not in its pure form. Understanding the absorption phenomena of Hydrogen sulfide in different water cuts will definitely be of great help to the oil industry to make better forecasts of H2S concentrations being ejected from each well.

Self-assembly is a fundamental process in the field of nanotechnology, where molecules organize into complex structures spontaneously or induced by environmental factors. Peptides, short chains of amino acids, can self-assemble into many types of nanostructures. The self-assembly of peptides is governed by noncovalent interactions, including electrostatic interactions, hydrogen bonding, hydrophobic interactions, aromatic-aromatic interactions, and van der Waals forces. By varying the amino acid sequences and manipulating environmental parameters, these interactions can be modulated to obtain diverse supramolecular nanostructures, exhibiting a wide range of physical, chemical, and biological properties. Furthermore, the ability to control these properties opens up a world of possibilities in biomedical and biocatalytic applications. From drug delivery systems to enzyme mimics, as well as cancer treatments, the potential of these self-assembling peptides is vast and continues to be a vibrant area of research. Exploiting this potential, this dissertation delves into the design, synthesis, and investigation of self-assembling peptides for a range of applications. The introductory chapters of this document lay the groundwork, providing a comprehensive overview of self-assembly and its potential in biocatalytic and biomedical domains. The focus shifts in the later chapters to drug delivery applications, particularly in the delivery of hydrogen sulfide (H2S), and its implications in cardioprotection and cancer treatment. Finally, this document details an evaluation of self-assembled peptides in the context of biocatalysis using a combined experimental and computational approach. Chapter 3 discusses the design and synthesis of peptide-H2S donor conjugates (PHDCs) with an unusual adamantyl group. Several of PHDCs studied in this chapter self-assembled into novel nanocrescent structures observed under both conventional transmission microscopy (TEM) and cryogenic TEM (cryo-TEM). By varying the C-terminal amino acid with cationic, nonionic, or anionic amino acids, the PHDC morphologies remained unaffected, offering a robust peptide design for crescent-shaped supramolecular nanostructures. Chapter 4 discusses an extension of this project, introducing a cyclohexane in PHDCs instead of an adamantyl group. In this work, we designed and fabricated four constitutional isomeric PHDCs, which self-assembled into nanoribbons with different dimensions and large nanobelts. These morphologies exhibited varying cellular uptake and in vitro H2S release amounts, influencing their protective effects against oxidative stress induced by H2O2. With the knowledge of the impact of subtle changes in PHDC structures, Chapter 5 discusses our further design of three more PHDCs with the variation of side chain capping group, from an aromatic phenyl ring to a cyclohexane unit, to an aliphatic n-hexyl chain. In this chapter, we studied how changes in the hydrocarbon tail can influence the supramolecular nanostructures and their potential ability for colon cancer treatment. A final aspect of H2S delivery in Chapter 6 involves the creation of a stable PHDC with an extended H2S release profile. By integrating the H2S donor into a β-sheet forming peptide sequence with a Newkome-like poly(ethylene glycol) dendron, this PHDC self-assembles into spherical or fibril nanostructures with or without stirring. The H2S release was further studied by triggering release with various charged thiol molecules. Finally, another facet of this document focuses on three constitutional isomeric tetrapeptides containing a catalytic functional amino acid, His. Chapter 7 discusses these tetrapeptides, which self-assembled into nanocoils, nanotoroids, and nanoribbons based on the position of the His residue in the peptide sequence. Computational studies simulating the self-assembling process revealed the distribution of His residues and hydrophobic pockets, reminiscent of natural enzyme binding sites. A tight spatial distribution of His residues and hydrophobic pocket in nanocoils provided a picture for why this morphology exhibited the highest rate enhancement in catalyzing a model ester hydrolysis reaction. This study demonstrated how subtle molecular-level changes impact supramolecular nanostructures and catalytic efficiency. The final chapter details conclusions on all the research in this dissertation and discusses further directions of self-assembling peptides in the application of drug delivery and design of catalyst mimics. / Doctor of Philosophy / Self-assembly is a fascinating process in nanotechnology, where molecular building blocks come together to form complex structures. Peptides, which are short chains made up of amino acids, can play a crucial role in this process. They can organize themselves into various shapes due to different forces acting between their amino acid building blocks. By changing the arrangement of amino acids and adjusting the environment, scientists can create a wide range of nanoscale structures with unique properties from peptides. These self-assembling peptides have enormous potential in fields like medicine and catalysis. This dissertation describes how to design and make self-assembling peptides for various uses. Chapter 1 describes the general structure of the document, and Chapter 2 discusses the basics of self-assembly and how it can be applied in medicine and other areas. Chapters 3-6 focus on using self-assembling peptides to deliver hydrogen sulfide (H2S), a noxious gaseous molecule that is now recognized as a vital signaling molecule involved in various physiological processes. Several classes of peptide-H2S donor conjugates (PHDCs) are discussed in these chapters, including PHDCs that form nanoscale crescents, twisted ribbons, fibers, and other structures. These nanostructures show promise in protecting cells from harmful substances or can act as drugs in cancer treatment. We also investigate how different modifications affect their performance in biomedical applications. The final research chapter, Chapter 7, involves using self-assembling peptides as catalysts, molecules that speed up chemical reactions. By arranging the amino acids in different ways, peptides that form nanoscale coils, toroids, or ribbons-like structures were created. These different shapes influenced how well they catalyzed reactions. Computational modeling studies helped explain how small differences in molecular design led to big impacts on their catalytic abilities. The final chapter discloses conclusions on all the research in this dissertation and discusses the further directions of self-assembling peptides as medicines and catalysts.

Yes / Adsorbents are developing in the various separation industries; these adsorbents can use to sweeten natural gas and remove hydrogen sulfide. Many commercial adsorbents are not regenerable when exposed to hydrogen sulfide because hydrogen sulfide is highly reactive. For removal, the main challenge when using surface adsorbent, is the dissociation adsorption of and non-regenerability of adsorbent. In this study, ultra-stable Y (USY) zeolite, was chosen to adsorb hydrogen sulfide due to its unique physical and chemical properties. To accurately model the adsorption isotherms, experimental adsorption data were measured in high pressure up to 12 bar for hydrogen sulfide and 21 bar for carbon dioxide, methane, and nitrogen as other natural gas components. The experiments were performed at three temperatures of 283, 293 and 303 K. Toth model fitted the experimental data very well, and the capacity of hydrogen sulfide adsorption on USY at the temperature of 283 K and pressure of 12 bar is 4.47 mmol/g that is noticeable. By performing ten cycles of adsorption and regeneration of hydrogen sulfide on USY, the regenerability of the adsorbent was investigated and compared by conducting a similar test on commercial 13X adsorbent. USY is found to be completely regenerable when exposed to hydrogen sulfide. The Isosteric adsorption heat of hydrogen sulfide on the adsorbent is 18.1 kJ/mol, which indicates physical adsorption, and the order of adsorption capacity of tested compounds on USY is H2S > CO2≫CH4 > N2.

Yes / The adsorption of acid gas, including hydrogen sulfide and carbon dioxide, by superhigh silica ZSM-5 was investigated. Equilibrium adsorption isotherms of high-purity hydrogen sulfide and carbon dioxide were measured experimentally using this new sorbent. In addition, methane and nitrogen adsorption isotherms on this MFI-type zeolite were also measured as representative of other natural gas components. To enhance the reliability of the results, the adsorption pressure has been selected up to 20 bar at three different temperatures. Superhigh silica ZSM-5 for the adsorption of hydrogen sulfide shows an impressive result of 3.04 mmol·g–1 at 12 bar and 283 K. This value was 2.69 mmol·g–1 for carbon dioxide at 21 bar and 283 K. The adsorption capacity of H2S on the ZSM-5 is the highest, and N2 is the lowest; the order of the adsorption capacities of components is H2S > CO2 > CH4 > N2. The adsorption heat of different adsorbates is calculated: 13.7 and 29.5 kJ·mol–1 for H2S and CO2, respectively. Physical adsorption has occurred on high-silica ZSM-5, especially for hydrogen sulfide, and this is a great advantage. By increasing the temperature, the adsorption capacity of components on the ZSM-5 decreases, but due to differences in the adsorption heat of the adsorbate, the ideal selectivity for hydrogen sulfide increases. There is a challenge in the choice of the best condition for H2S removal, as, by increasing the temperature, the adsorption capacity of hydrogen sulfide reduces, but the selectivity of the hydrogen sulfide increases as compared to other gases. This phenomenon is not true for the selectivity of other components.

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In the early 2000s, hydrogen sulfide (H₂S) was added to the family of molecules known as gasotransmitters, a class of endogenously produced and freely diffusing biological signaling molecules. Since this discovery, biologists and chemists have sought to understand the physiological roles of H₂S and to elucidate the potential benefits of exogenous H₂S delivery. As a result, many synthetic small molecule donor compounds have been created to deliver H₂S in response to various biologically relevant stimuli. Furthermore, macromolecular and supramolecular H₂S donor systems have been created to protect donors in the biological milieu, extend release kinetics, or control H₂S release conditions. Thus, H₂S-donating nanostructures with precisely tuned release rates provide invaluable tools for further investigating the biological roles and therapeutic potential of H₂S. This work describes two polymer micelle systems for the controlled delivery of H₂S. The first system is based on H2S-releasing polymer amphiphiles with varying degrees of a plasticizing comonomer incorporated into the core-forming block. The glass transition temperature of the core-forming block varied predictably with incorporation of the plasticizing comonomer. Accordingly, the half-life of H₂S release decreased from 4.2 h to 0.18 h with increasing core-forming block mobility. The second system is based on H₂S releasing polymer amphiphiles with varying degrees of crosslinking in the core-forming block. The crosslinked system was designed to achieve control over H₂S release rate with minimal dilution of donor in the core-forming block. The half-life of H₂S release increased from 117 min to 210 min with increasing crosslink density in the core-forming block, further demonstrating that H₂S release rates can be precisely controlled by tuning micelle core mobility. Beyond control over H₂S release rate, further study of the biological roles of H₂S requires donor systems with precisely triggered release. To this end, this dissertation also discusses efforts to investigate fundamental micelle–unimer relationships. This section includes an evaluation of the impact of core-forming block mobility on micelle–unimer coexistence utilizing a model polymer amphiphile system. Unimer populations correlated with glass transition temperatures of the core-forming block, suggesting the need to consider micelle core mobility when discussing polymer chain phase behavior of amphiphilic block copolymers. Finally, this work discloses new methods for the radical polymerization of poly(olefin sulfones) with control over molecular weight. POSs are a unique class of polymers with great potential for stimuli-responsive depolymerization to generate sulfur dioxide (SO₂), a signaling gas related to H₂S. / Doctor of Philosophy / Hydrogen sulfide (H2S) is commonly known for its pungent odor and toxicity. Despite this negative stigma, H2S has been revealed as a vital signaling molecule in both plants and animals. This discovery has prompted the coordination of biologists and chemists in an effort to better understand the roles of H2S in the body. Driven by this motive, great interest has centered around the development of finely tuned molecules designed to generate H2S in the body, termed H2S donors. A variety of synthetic H2S donors have been reported with various conditions enabling release. Building on this work, the development of polymeric H2S donors with tunable release rates will enable investigation into the complex behavior of H2S in the body. The first half of this dissertation focuses on the design and synthesis of two polymeric H2S donor systems for the controlled release of H2S. These systems take advantage of sequestering the H2S donating species inside a polymeric nanostructure in water called a micelle. Because H2S release requires a triggering molecule to enter the polymeric nanostructure, release rate can be tuned by modifying the mobility of the structure. The first system discussed demonstrates this concept by increasing the flexibility of the micelle core. As expected, H2S release rates increased with increasing flexibility. The second system discussed advances this idea by limiting mobility within the micelle core, rather than increasing flexibility. Accordingly, H2S release rates decreased with decreasing mobility within the micelle core. The latter half of this dissertation broadly explores the development of polymeric signaling gas delivery vehicles with triggered release conditions. We first investigate the impact of polymer chain flexibility on the formation of micelles in water. Polymer chain flexibility significantly impacted the balance between micelles and unassembled polymer chains in solution, suggesting the need to consider this characteristic when designing donor systems for precise release conditions. Lastly, we discuss the development of controlled polymerization techniques for poly(olefin sulfones). We envision that poly(olefin sulfones) will be a useful class of polymers in the design of donor systems relying on triggered depolymerization for release of the signaling gas sulfur dioxide.

Hydrogen sulfide (H₂S) was recognized as a critical signaling molecule in mammals nearly two decades ago. Since this discovery biologists and chemists have worked in concert to demonstrate the physiological roles of H₂S as well as the therapeutic benefit of exogenous H₂S delivery. As the understanding of H₂S physiology has increased, the role(s) of other sulfur-containing molecules as potential players in cellular signaling and redox homeostasis has begun to emerge. This creates new and exciting challenges for chemists to synthesize compounds that release a signaling compound in response to specific, biologically relevant stimuli. Preparation of these signaling compound donor molecules will facilitate further elucidation of the complex chemical interplay within mammalian cells. To this end we report on two systems for the sustained release of H₂S, as well as other sulfur signaling molecules. The first system discussed is based on the N-thiocarboxyanhydride (NTA) motif. NTAs were demonstrated to release carbonyl sulfide (COS), a potential sulfur signaling molecule, in response to biologically available nucleophiles. The released COS is shown to be rapidly converted to H₂S in the presence of the ubiquitous enzyme carbonic anhydrase (CA). A synthetic route that affords NTAs with reactive functionalities was devised and the functional "parent" NTAs were successfully conjugated to a variety of substrates, ranging from small molecules to polymers. These functional NTAs provide a platform from which a library of NTA-based COS/H₂S may be readily prepared convergently in an effort to move towards H₂S-releasing drug and polymer conjugates. Additionally, preliminary in vitro cytotoxicity studies indicate that NTAs are noncytotoxic at concentrations above 100 µM. The second system discussed in this dissertation leverages the 1,6-benzyl elimination reaction (or self-immolative reaction) to facilitate the release of a persulfide (R–SSH) from a small molecule prodrug platform as well as a separate system that releases COS/H₂S from a polymer. The self-immolative persulfide prodrug was designed to be responsive to reactive oxygen species (ROS) and demonstrates efficacy as an antioxidant in vitro. Furthermore, the polymeric COS/H₂S self-immolative system was designed to respond to reducing agents, including H₂S itself, and shows promise as a H₂S signal amplification platform. / Doctor of Philosophy / Hydrogen sulfide (H₂S) has long been recognized as a malodorous and toxic byproduct of industrial chemical processes. However, the discovery of H₂S as a key signaling molecule in mammals has drastically shifted the paradigm of H₂S research over the last two decades. Research into the production and roles of H₂S in the body is ongoing, but has pointed to the implication of changes in H₂S production to the onset of a variety of disease states, including cardiovascular disease and Alzheimer’s. As alterations in the body’s production of H₂S have been correlated to certain disease states, collaborative research efforts among biologists and chemists have demonstrated the utility of H₂S-based therapeutics in helping to alleviate these disease states. Our understanding of the roles of H₂S in the body, and potential benefits derived from H₂S-releasing drugs, can only continue to advance with the development and improvement of H₂S releasing compounds. The first portion of this dissertation focuses on the synthesis of a new class of H₂S-releasing compounds, termed N-thiocarboxyanhydrides (NTAs). NTAs release H₂S through an intermediate sulfur-containing molecule, carbonyl sulfide (COS), which may have signaling properties independent of H₂S. The COS that is released from the NTAs is rapidly converted to H₂S by the action of the ubiquitous enzyme carbonic anhydrase. A variety of functional NTAs were synthesized, which in turn were used to prepare a small library of NTA-based COS/H₂S releasing compounds. This work informs the preparation of H₂S-drug or H₂S-polymer conjugates. The second portion of this dissertation examines a class of compounds broadly termed self-immolative prodrugs. The self-immolative prodrug platform was leveraged to release H₂S, or persulfides (R–SSH), another class of sulfur-containing molecules of biological interest. The self-immolative persulfide prodrug system was designed to be responsive to reactive oxygen species (ROS), a harmful cellular byproduct. The persulfide donor was successful in mitigating the harmful effects of ROS in heart cells. Independently, a polymeric self-immolative H₂S releasing system was designed to depolymerize in the presence of H₂S, resulting in the generation of 6-8-fold excess of H₂S upon depolymerization. We envision the self-immolative H₂S-releasing polymer will show promise in biological applications where a vast excess of H₂S is needed rapidly.