Theses and Dissertations at Montana State University (MSU)
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Item Role of the P-cluster and FeMo-cofactors in nitrogenase catalysis(Montana State University - Bozeman, College of Letters & Science, 2017) Keable, Stephen Michael Keable; Chairperson, Graduate Committee: John W. Peters; Andrew J. Rasmussen, Karamatullah Danyal, Brian J. Eilers, Gregory A. Prussia, Axl X. LeVan, Lance C. Seefeldt and John W. Peters were co-authors of the article, 'Three structural states of the nitrogenase P-cluster revealed in MOFE protein structures at poised potentials' submitted to the journal 'Biochemistry' which is contained within this thesis.; Jacopo Vertemara, Karamatullah Danyal, Andrew J. Rasmussen, Brian J. Eilers, Oleg A. Zadvornyy, Luca De Gioia, Giuseppe Zampella, Lance C. Seefeldt and John W. Peters were co-authors of the article, 'Acetylene interaction with the nitrogenase femo-cofactor investigated by structural and computational analysis' submitted to the journal 'Biochemistry' which is contained within this thesis.; Dissertation contains two articles of which Stephen Michael Keable is not the main author.Biological nitrogen fixation has been extensively researched for over four decades, yet due to the complex nature of this process, numerous questions still remain regarding the catalytic mechanism, and investigation of this system has relevance across a number of disciplines. Nitrogen is a fundamental element to all biological systems, primarily occurring in proteins and nucleic acids. However, most nitrogen on Earth is found in the form of nitrogen gas, a form that is biologically unavailable to most organisms owing to the strength of the triple bond between the two nitrogen atoms. The limited abundance of biologically accessible (or fixed) nitrogen has driven an anthropomorphic thrust to supplement the nitrogen cycle with nitrogenous fertilizers, thereby boosting agricultural output. The primary industrial method to produce these fertilizers, derived from the Haber-Bosch synthesis, is an energy intensive process that consumes approximately 1- 2% of the world's energy portfolio. This process utilizes metal iron catalysis, high temperatures and high pressures, along with hydrogen usually obtained from reformed fossil fuels, to reduce atmospheric nitrogen gas to ammonia. Aside from the environmental consequences that arise from the production of nitrogenous fertilizers, long-term agricultural application may also have disastrous ecological ramifications, such as eutrophication. Additionally, biological nitrogen fixation supports more than half the human population, and having a more complete understanding of this complex process has the potential to displace some of the demand for fertilizer production. The aforementioned reasons are clearly enough to warrant serious investigation into biological nitrogen fixation, however, the fascinating intricacies and comparative relevance to other biochemical systems further motivates the study of this system. The enzyme committed to this task, nitrogenase, orchestrates an elegant unidirectional multiple electron reduction and activation of the nitrogen triple bond. Historically, mechanistic characterization of this enzyme has been difficult for a number of reasons; however, studies to date have revealed many aspects of the process as biochemical techniques have improved. Nitrogenase is an oxygen sensitive, complex two-component enzyme that is mechanistically pertinent to many other biochemical processes. Presented here are studies revealing insight into substrate binding and the unique gated electron transfer mechanism of this fascinating enzyme.Item Biological redesign of virus particles for a new era of catalytic materials(Montana State University - Bozeman, College of Letters & Science, 2016) Jordan, Paul Campion; Chairperson, Graduate Committee: Trevor Douglas; Dustin P. Patterson, Kendall N. Saboda, Ethan J. Edwards, Heini M. Miettinen, Gautam Basu, Megan C. Thieleges and Trevor Douglas were co-authors of the article, 'Self-assembling biomolecular catalysts for hydrogen production' in the journal 'Nature chemistry' which is contained within this dissertation.; Joseph C-Y Wang, Ethan J. Edwards, Heini M. Miettinen, Amanda L. Le Sueur, Megan C. Thielges , Adam Zlotnick and Trevor Douglas were co-authors of the article, 'Redesign of a virus particle for NADH-driven hydrogen production' which is contained within this dissertation.; This dissertation contains one article of which Paul Campion Jordan is not the main author.Biology has designed a suite of compartments and barriers that confine fundamental biochemical reactions. Such barriers include the membrane-bound organelles but also a suite of protein-based compartments that architecturally and chemically integrate catalytic processes. These compartments co-polymerize from multiple protein subunits to form polyhedral structures that spatially separate enzymatic processes. Protein compartments confine volatile intermediates, trap toxic reaction products, and co-localize multiple enzymatic processes for catalytic enhancements. The protein-based compartments represent, advantageously, a combination of form and function that has inspired the synthesis of new, designer materials. The self-assembly of cage-like structures, the structures of which are reminiscent of the compartments, has been used for the directed encapsulation of active enzymes. We have used the capsid from bacteriophage P22, as a nanocontainer for directing the encapsulation of a variety of gene products, including active enzymes. The P22 capsid assembles from a coat protein (CP) and a scaffold protein (SP) which templates its assembly. Using the simplicity of the P22 expression system, a strategy was developed and implemented for the directed encapsulation of an active, [NiFe] hydrogenase. We hypothesized and proved the enzyme active site needed to be matured by accessory proteins found within the expression host. A two plasmid expression system was designed, where the hydrogenase cargo was under the control of a different inducer than the P22 CP. The [NiFe]-hydrogenase is a heterodimer and each enzyme subunit was fused to different SP. The resultant packaging of the two SP fusions, with the hydrogenase large and small subunits fused to them stabilized a weak heterodimeric structure. Remarkably, the stabilizing effects of the capsid allowed us to probe the infrared signatures associated with the hydrogenase active site. Finally, the progress made here in developing a virus capsid for H2 production left room to build increased complexity into the P22-Hydrogenase system while also taking inspiration from the innate, biological function of the hydrogenase. We incorporated a cytochrome/cytochrome reductase pair to drive H 2 production using NADH. These designs, built at the molecular level, represent inherently renewable catalysts that pave the way for a new era of catalytic materials synthesized entirely by biology.Item Stabilization of metallic catalyst microstructures against high-temperature thermal coarsening(Montana State University - Bozeman, College of Engineering, 2016) Driscoll, David Robert; Chairperson, Graduate Committee: Stephen W. Sofie; Clay D. Hunt, Julie E. Muretta and Stephen W. Sofie were co-authors of the article, 'Thermally stabilized nickel electro-catalyst introduced by infiltration for high temprature electrochemical energy conversion' in the journal 'Transactions of the Electrochemical Society' which is contained within this thesis.; Cameron H. Law and Stephen W. Sofie were co-authors of the article, 'Design and synthesis of metallic nanoparticle-ceramic support interfaces for enhancing thermal stability' in the journal 'Ceramic transactions' which is contained within this thesis.; Stephen W. Sofie was a co-author of the article, 'Stabilization of nano-scale metallic microstructure against thermal coarsening' in the journal 'Ceramic transactions' which is contained within this thesis.; Melissa D. McIntyre, Martha M. Welander, Stephen W. Sofie and Robert A. Walker were co-authors of the article, 'Enhancement of high temperature metallic catalysts : aluminum titanate in the nickel-zirconia system' in the journal 'Applied catalysis A: general' which is contained within this thesis.; Thesis contains two articles of which David Robert Driscoll is not the main author.; Melissa D. McIntyre, Martha M. Welander, Daniel E. Perea, Robert A. Walker and Stephen W. Sofie were co-authors of the article, 'Aluminum oxide processed as a beneficial additive in SOFC anodes' submitted to the journal 'Journal of the electrochemical society' which is contained within this thesis.; Clay D. Hunt, Daniel E. Perea, and Stephen W. Sofie were co-authors of the article, 'Diffusion caging : thermodynamic arrest of Ostwald ripening' submitted to the journal 'Advanced Materials' which is contained within this thesis.The size and shape of metal particulate at high temperature is dictated by surface energy. In systems containing very small metal particles, smaller particles shrink and disappear as they grow into larger particles in a process referred to as coarsening. Coarsening causes irreversible degradation in a number of important systems including automotive catalytic converters and solid oxide fuel cells (SOFC) through a loss of catalyst (metal) surface area. This phenomenon is exemplified by nickel metal catalyst that is supported on ytrria-stabilized zirconia (YSZ) which represents a materials system critical to the function of SOFCs. It has been demonstrated that additions of aluminum titanate (ALT) to the Ni-YSZ system with subsequent thermal treatment can act to stabilize the geometry of Ni on YSZ. In demonstration SOFCs, ALT has increased the time required for the first 10% of degradation by a factor of 115. This work has sought to elucidate the mechanisms by which ALT imparts increased stability. The work contained here demonstrates that ALT easily decomposes to Al 2O 3 and TiO 2. During thermal treatment, the alumina reacts with NiO to form nickel aluminate and the titania interacts with the YSZ where it can form Zr 5Ti 7O 24 -- a mixed ion electron conducting phase. In this way, the Al and Ti components of ALT have been determined to act independently where alumina appears to be dominant in microstructural stabilization. During cell operation, the nickel aluminate decomposes to nickel metal decorated with alumina nano-particulate. This geometry forms the basis of 'diffusion caging' as a stabilization mechanism which is the subject of Chapter 8. The role of titania appears to be less important except when processing occurs in a way that facilitates formation of the MIEC phase. However, Ni-YSZ cermets have also shown a strength enhancement when doped with ALT. This strength enhancement is likely due to the influence of titania (Chapter 7). Future work has the potential to extend concepts discussed here to a number of high temperature catalytic systems.Item In operando spectroscopic studies of high temperature electrocatalysts used for energy conversion(Montana State University - Bozeman, College of Letters & Science, 2016) McIntyre, Melissa Dawn; Chairperson, Graduate Committee: Robert Walker; John D. Kirtley, David M. Halat, Kyle W. Reeping and Robert A. Walker were co-authors of the article, 'In situ spectroscopic studies of carbon formation in SOFCS operating with syn-gas' in the journal 'Electrochemical Society transactions' which is contained within this thesis.; Daniel M. Neuburger and Robert A. Walker were co-authors of the article, 'In operando raman spectroscopy studies of temperature dependent carbon accumulation on SOFCS operating with syn-gas' submitted to the journal 'The journal of the Electrochemical Society' which is contained within this thesis.; John D. Kirtley, Anand Singh, Shamiul Islam, Josephine M. Hill and Robert A. Walker were co-authors of the article, 'Comparing in situ carbon tolerances of Sn-infiltrated and Bao-infiltrated Ni-YSZ cermet anodes in solid oxide fuel cells exposed to methane' in the journal 'The journal of physical chemistry C' which is contained within this thesis.; David R. Driscoll, Martha M. Welander, Josh B. Sinrud, Stephen W.Sofie, Robert A. Walker were co-authors of the article, 'In situ formation of multifunctional ceramics : mixed ion-electron conducting properties of zirconium titanium oxides' submitted to the journal 'The journal of materials chemistry A' which is contained within this thesis.; Thesis contains an article of which Melissa Dawn McIntyre is not the main author.Solid-state electrochemical cells are efficient energy conversion devices that can be used for clean energy production or for removing air pollutants from exhaust gas emitted by combustion processes. For example, solid oxide fuel cells generate electricity with low emissions from a variety of fuel sources; solid oxide electrolysis cells produce zero-emission H2 fuel; and solid-state DeNO x cells remove NO x gases from diesel exhaust. In order to maintain high conversion efficiencies, these systems typically operate at temperatures > or = 500°C. The high operating temperatures, however, accelerate chemical and mechanical cell degradation. To improve device durability, a mechanistic understanding of the surface chemistry occurring at the cell electrodes (anode and cathode) is critical in terms of refining cell design, material selection and operation protocols. The studies presented herein utilized in operando Raman spectroscopy coupled with electrochemical measurements to directly correlate molecular/material changes with device performance in solid oxide cells under various operating conditions. Because excessive carbon accumulation with carbon-based fuels destroys anodes, the first three studies investigated strategies for mitigating carbon accumulation on Ni cermet anodes. Results from the first two studies showed that low amounts of solid carbon stabilized the electrical output and improved performance of solid oxide fuel cells operating with syn-gas (H 2/CO fuel mixture). The third study revealed that infiltrating anodes with Sn or BaO suppressed carbon accumulation with CH 4 fuel and that H 2O was the most effective reforming agent facilitating carbon removal. The last two studies explored how secondary phases formed in traditional solid oxide cell materials doped with metal oxides improve electrochemical performance. Results from the fourth study suggest that the mixed ion-electron conducting Zr 5Ti 7O 24 secondary phase can expand the electrochemically active region and increase electrochemical activity in cermet electrodes. The final study of lanthanum strontium manganite cathodes infiltrated with BaO revealed the reversible decomposition/formation of a Ba 3Mn 2O 8 secondary phase under applied potentials and proposed mechanisms for the enhanced electrocatalytic oxygen reduction associated with this compound under polarizing conditions. Collectively, these studies demonstrate that mechanistic information obtained from molecular/material specific techniques coupled with electrochemical measurements can be used to help optimize materials and operating conditions in solid-state electrochemical cells.Item The examination of chiral X-type ligands in Pd(II)-catalyzed enantioselective oxdiatative transformations(Montana State University - Bozeman, College of Letters & Science, 2015) Aebly, Andrew Henry; Chairperson, Graduate Committee: Trevor J. RaineyPalladium catalysis has been utilized extensively in organic chemistry for the synthesis of complex molecules. Despite its abundant use and many successful applications, there remain challenging transformations, specifically with developing new chiral centers. The aim of this research was to explore the underdeveloped, weakly coordinating X-type ligands and their applicability in enantioselective reactions. The electrophilic catalyst, generated by the coordination of sulfonic or phosphoric acid ligands, was utilized to explore underfunctionalized starting materials, such as unactivated alkenes and aryl C-H bonds. Herein we report two Pd II-catalyzed enantioselective transformations: oxidative amination and 1,2-carboamination. The Wacker-type oxidative amination was accomplished with good yields and modest enantioselectivity in the synthesis of chiral indolines and a cyclic carbamate. Substantial loss in enantioselectivity was seen with ortho-substituted anilines. The 1,2-carboamination coupled a mild, directing group facilitated C-H activation on a series of aryl ureas with a subsequent chiral C-N bond formation. Electron-rich, para-substituted aryl ureas provided the highest consistent yields and enantioselectivities. Electron deficient substrates provided little reactivity and substitutions at the ortho- and meta-positions gave inconsistent results. To our knowledge these transformations mark the first enantioselective examples of Pd II-catalyzed oxidative transformations utilizing chiral sulfonic acid ligands.Item Mechanistic and spectroscopic investigations of the radical SAM maturases HydE and HydG for [FeFe]-hydrogenase(Montana State University - Bozeman, College of Letters & Science, 2015) Betz, Jeremiah Nathanael; Chairperson, Graduate Committee: Joan B. Broderick; Nicholas W. Boswell, Corey J. Fugate, Gemma L. Holliday, Eyal Akiva, Anna G. Scott, Patricia C. Babbitt, John W. Peters, Eric M. Shepard and Joan B. Broderick were co-authors of the article, '[FeFe]-hydrogenase maturation: insights into the role HydE plays in dithiomethylamine biosynthesis' in the journal 'Biochemistry' which is contained within this thesis.; Thesis contains article(s) of which Jeremiah Nathanael Betz is not the main author.While biochemical, spectroscopic, and analytical investigations helped classify multiple phylogenetically distinct hydrogenases it was not until 2004 that Peters et al. gave the world a look at the non-proteinaceous component of the active site of a hydrogenase enzyme. The active site (H-cluster) of [FeFe]-hydrogenase was found to possess a typical [4Fe-4S] cluster bridged by the sulfur of a cysteinyl group to an iron of a uniquely decorated 2Fe subcluster that serves as the site of molecular hydrogen synthesis and oxidation. The subcluster contains two irons bridged by a dithiomethylamine (DTMA) group and a carbon monoxide ligand. In addition each iron is coordinated by a carbon monoxide and cyanide ligand. Posewitz et al. in 2004 were the first to shed light on the syntheses of these non-proteinaceous ligands when through an insertional mutagenesis study of a hydrogen producing green alga they found two radical SAM enzymes, HydE and HydG, that were required for the maturation of [FeFe]- hydrogenase. HydG has been extensively studied and been shown to produce the diatomic ligands of the H-cluster from tyrosine. In this work the substrate specificity and active site of HydG was investigated. These investigations led to a refinement of the location and mechanism of H-atom abstraction of the substrate HydG and support the identity of the C-terminal FeS cluster as a [4Fe-4S] cluster that is responsible in the later steps of diatomic production. While several crystal structures of HydE have been published, the work reported herein is the first to propose a substrate and reaction mechanism for HydE. The results point to commonly biologically available low molecular weight thiols such as L-cysteine, L-homocysteine, and mercaptopyruvate as likely substrates. More recent work has implicated mercaptopyruvate as the substrate given glyoxylate was produced under turnover conditions. Our proposed mechanism involves formation of thioformaldehyde from mercaptopyruvate. Two thioformaldehyde units may be condensed with ammonia forming the DTMA precursor. While many details remain unsolved regarding the maturation of [FeFe]-hydrogenase, our findings regarding HydE and HydG are important steps forward in the understanding of biological catalysts of hydrogen production.Item Effect of pressure on catalytic polyforming of gas oil(Montana State University - Bozeman, College of Engineering, 1950) Ennenga, Benard A.Item Catalytic hydrotreating of shale-oil coker distillate(Montana State University - Bozeman, College of Engineering, 1955) Holecek, Russell J.Item The catalytic hydrodesulfurization of fuel oils(Montana State University - Bozeman, College of Engineering, 1954) Hooper, Howard C.Item Catalytic hydrodenitrogenation in the presence of chlorides(Montana State University - Bozeman, College of Engineering, 1966) McCandless, Frank Philip