Theses and Dissertations at Montana State University (MSU)
Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/733
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Item The biofilm matrix in sulfate-reducing bacterial biofilms: potential roles for electron mediators and large proteins(Montana State University - Bozeman, College of Letters & Science, 2019) Krantz, Gregory Peter; Chairperson, Graduate Committee: Matthew Fields; Kilean Lucas, Erica L.-Wunderlich, Linh T. Hoang, Recep Avci, Gary Siuzdak and Matthew W. Fields were co-authors of the article, 'Bulk phase resource ratio alters carbon steel corrosion rates and endogenously produced extracellular electron transfer mediators in a sulfate-reducing biofilm' in the journal 'Biofouling' which is contained within this dissertation.; Peter J. Walian, Marty Boyl-Davis, Kara De Leon, Judy D. Wall and Matthew W. Fields were co-authors of the article, 'Large extracellular proteins sense hydrodynamic force and drive biofilm formation in Desulfovibrio vulgaris' which is contained within this dissertation.; Marty Boyl-Davis, Kara De Leon, Judy D. Wall and Matthew W. Fields were co-authors of the article, 'Characterization of extracellular biofilm mutants cultivated on 1018 carbon steel in Desulfovibrio vulgaris Hildenborough' which is contained within this dissertation.Sulfate-reducing bacteria grow and form biofilms in soil and benthic environments across much of the Earth's surface. Formation of these prevalent biofilms requires the secretion of an extracellular polymeric substance (EPS) to allow the cells to stick together, as well as adhere to a surface. The specific interactions that occur between EPS components of an SRB biofilm are poorly understood. The data presented in this dissertation suggest the presence of two extracellular mechanisms utilized in these communities. The first mechanism was observed in a study altering the lactate (electron donor) and sulfate (electron acceptor) ratios to create limiting nutrient conditions in Desulfovibrio alaskensis G20 (G20) biofilms. G20 was grown under two conditions: electron donor limited (EDL) and electron acceptor limited (EAL) conditions. When grown on a 1018 carbon steel substrate, the G20 consumes all of the available lactate, and once limited, it turns to the high energy electrons in the Fe 0 for growth. Corrosion rates in the steel increased two fold compared to the EAL condition. Global metabolomic analysis revealed increased lumichrome levels under the EDL condition, which suggested higher flux through the riboflavin/FAD biosynthetic pathway. Previous research showed that synthetically adding riboflavin and FAD increases the corrosion rate of a SRB biofilm on 1018 carbon steel, and paired with these results, suggest G20 produces a flavin-based extracellular electron transfer molecule endogenously, and uses it to harvest high energy electrons from Fe 0 when limited for electron donor. The second mechanism was observed in Desulfovibrio vulgaris Hildenborough (DvH) biofilms grown on glass. Two proteins, DVU1012 and DVU1545 were found to be the most abundant extracellular peptides in a DvH biofilm. Single deletion strains for these proteins grew biofilm similar to the wild type strain, but a double deletion strain had decreased ability to form biofilm, demonstrating that at least one of the peptides must be present in order to form a biofilm. Exposure to increased shear force caused an large increase in wild-type biofilm biomass, yet eliminated the double mutant biofilm. These proteins are required for a DvH biofilm to respond to shear force.Item When a lectin binds a sugar, and other sweet tales(Montana State University - Bozeman, College of Letters & Science, 2019) Bernhard, Samuel Pruitt; Chairperson, Graduate Committee: Mary J. Cloninger; Mackenzie S. Fricke was an author and Katharina Achazi, Paul Hillman, Willy Totten, Rainer Haag and Mary J. Cloningerwere co-authors of the article, 'The toxicity, uptake, and impact on galectin-3 mediated apoptosis of lactose functionalized dendrimers' submitted to the journal 'Biomolecules Special Issue: Moving Forward with Dendrimers' which is contained within this dissertation.The current state of chemotherapy and cancer treatment leaves much to be desired. Treatment is generally non-specific and relies on high dosage to achieve therapeutically relevant concentrations at target sites. Glycopolymer-drug conjugates, featuring targeting molecules and therapeutic prodrug on a water-soluble polymeric scaffold, offer a solution to these contemporary problems. Here, the complexity of glycopolymer design is explored through the lens of a biologically significant carbohydrate-binding receptor. In particular, galectin-3 is a complex Beta-galactoside binding lectin that experiences altered expression in many cancer pathologies and is implicated in metastasis, angiogenesis and poor overall prognosis. Galectin-3 mediates undesired cancer promoting processes through carbohydrate binding and oligomerization. A more complete understanding of the role galectin-3 plays in cancer progression will guide development of methods in the therapeutic intervention of these processes. In the interest of understanding galectin-3 and using it as a targeted receptor, its binding characteristics have been assessed through fluorescence lifetime and dynamic light scattering measurements. Employment of carbohydrates and glycopolymers including mannose, lactose, and lactose functionalized poly(amidoamine) (PAMAM) dendrimers, dendritic polyglycerols (dPG), and linear polymers (LP) provided insight into the carbohydrate binding avidity of galectin-3 and its propensity to oligomerize or form micron scale aggregates. A relationship between scaffold size and receptor recruitment was observed, which sheds light into multivalent binding motifs initiated by these glycopolymers and establishes a threshold for minimum requisite lactose functionality on lactose functionalized dendritic polyglycerols. In vitro cell based glycopolymer studies with AlexaFluor 647 and lactose functionalized PAMAM dendrimers revealed size-dependent uptake and demonstrated that accumulation occurs within the lysosome. Cellular aggregation experiments revealed that lactose functionalized LPs and dPGs influence galectin-3 mediated homotypic cellular aggregation and, in fact, augment this aggregation through receptor recruitment and cross-linking. The results reported here have provided a more fundamental understanding of galectin-3 binding interactions and have laid the groundwork for optimized glycopolymer-drug conjugate design.Item Toward the design and characterization of a dynamically similar artificial insect wing(Montana State University - Bozeman, College of Engineering, 2019) Reid, Heidi Elita; Chairperson, Graduate Committee: Mark JankauskiMicro air vehicles (MAVs) are a useful tool for numerous tasks, such as environmental mapping, search and rescue, and military reconnaissance. As MAV applications require them to operate at smaller and smaller length scales, traditional propulsion mechanisms (e.g. fixed wings, rotating propellers) cannot meet these demands. Conversely, flapping wing micro air vehicles (FWMAVs) can to realize flight at sub centimeter-lengths. However, FWMAVs face design challenges that preclude autonomous flight, including inefficient energetics and reliable on-board sensing. A comprehensive understanding of flying insect biomechanics may provide valuable design insights to help overcome the challenges experienced by FWMAVs. Insect wings have biological sensors that provide feedback to control attitude and wing deformation improves both inertial and aerodynamic power economy. Consequently, the insect wing can guide the design FWMAV-employed artificial insect wings. The present work aims to (1) dynamically characterize real insect wings via experimental modal analysis, and (2) develop dynamically similar artificial wings to be used on FWMAVs or in controlled studies. To our knowledge, no existing artificial insect wing models are isospectral and isomodal with respect to their biological counterparts. Isomodality and isospectrality imply they have identical frequency response functions and vibration mode shapes, and thus will deform similarly under realistic flapping conditions. We measured the frequency response function and vibration modes of fresh Manduca sexta forewings using an electrodynamic shaker and planar scanning vibrometer and estimated the wings' mass distribution via a cut-and-weigh procedure. Based upon our results, we designed and constructed the artificial wings using fused filament fabrication to print a polylactic acid vein structure, based upon the actual vein size and arrangement present in biological wings. Thin polymer films were manually layered over the vein structure and trimmed to fit the wing boundaries to produce a flat wing structure. We determined that the biological and artificial wings have nearly identical natural frequencies, damping ratios, gain, and shape for the first vibration mode. The second mode exhibited complex modal behavior previously unreported in literature, which likely has significant implications to flapping wing aerodynamics. We demonstrate the feasibility of fabricating economical, realistic artificial wings for robotic applications moving forward.Item The development of superresolution spectroscopic techniques and characterization of microscale exciton diffusion in organic semiconducting polymers(Montana State University - Bozeman, College of Letters & Science, 2018) Massaro, Eric Stephen; Chairperson, Graduate Committee: Erik Grumstrup; Andrew H. Hill and Erik M. Grumstrup were co-authors of the article, 'Superresolution structured pump-probe microscopy' in the journal 'ACS Photonics' which is contained within this thesis.; Andrew H. Hill, Casey L. Kennedy and Erik M. Grumstrup were co-authors of the article, 'Imaging theory of structured pump-probe microscopy' in the journal 'Optics Express' which is contained within this thesis.; Erik M. Grumstrup was a co-author of the article, 'Label-free saturated structured excitation microscopy' in the journal 'Photonics' which is contained within this thesis.; Erik M. Grumstrup was a co-author of the article, 'Exceptionally fast nanoscale exciton diffusion in donor-acceptor polymer thin films' which is contained within this thesis.; Erik M. Grumstrup was a co-author of the article, 'Toward direct imaging of sub-10 nm carrier diffusion lengths by differential detection pump-probe microscopy' which is contained within this thesis.Disordered semiconducting materials offer cost effective, solution processable alternatives to highly crystalline semiconducting materials for utilization in a variety of optoelectronic devices. However, characterization of these complex materials systems using bulk spectroscopic methods is heavily influenced by chemical and morphological heterogeneity inherent to the material. The experiments described in this thesis are designed to improve the fundamental understanding of the photophysical processes in disordered solution processed semiconducting materials by developing and utilizing high spatial resolution spectroscopic methods. Chapters 2-4 will outline the experimental and theoretical development of two superresolution spectroscopic techniques. First (chapters 2 & 3), structured pump-probe microscopy (SPPM) utilizes a structured excitation profile along with a diffraction limited probe pulse to achieve ~100 nm spatial resolution. Using SPPM it is also possible to collect time resolved spectroscopic data from a sub-diffraction limited volume. Second (chapter 4), label-free saturated structured excitation microscopy (LF-SSEM) is theoretically developed. LF-SSEM is experimentally similar to SPPM but exploits the saturation of the absorption process to achieve even greater resolution enhancement. Here, simulated LF-SSEM is shown to achieve ~33 nm spatial resolution. Chapter 5 demonstrates the utilization of PPM to investigate exciton transport in the organic semiconducting polymer (OSP), poly [N-9''-hepta-decanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)] (PCDTBT). Although OSPs have shown great promise for use in a variety of optoelectronic applications, much remains un-known about their excited state dynamics. The data reported here represents a significant contribution to the rapidly growing wealth of knowledge pertaining to OSP systems. Specifically, the microscale exciton diffusivity observed in PCDTBT thin films using PPM is found to reach 3.2 cm 2/s. Chapter 6 examines a technique in the early stages of development and optimization that is able to detect excited state carrier diffusion with increased sensitivity and accuracy compared to PPM. Differential detection pump-probe microscopy (DDPPM) uses two probe pulses to selectively eliminate the signal of carriers that have not diffused beyond the boundaries of the initial excitation. The experiments described within this dissertation are diverse, yet the common goal is to increase and improve the knowledge of photophysical properties in disordered semi-conducting materials. This goal takes two forms in the development of novel spectroscopic methodology and the characterization of complex materials using PPM. The singular result is the advancement of basic science pertaining to complex semiconducting materials systems.Item Developments in electrically conductive bio-composites for use in additive manufacturing(Montana State University - Bozeman, College of Engineering, 2019) Arroyo, Jesse Whitney; Chairperson, Graduate Committee: Cecily Ryan; Cecily Ryan was a co-author of the article, 'Incorporation of carbon nanofillers tunes mechanical and electrical percolation in PHBV:PLA blends' in the journal 'Polymers' which is contained within this thesis.With the growth of rapid production methods, such as additive manufacturing, petroleum derived plastics are becoming ever more prevalent in consumer homes and landfills. As the industry grows, research into a more circular approach to designing and using materials is critical to maintaining sustainability. Bioplastics such as poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) and poly(lactic acid) (PLA) provide material properties comparable to petroleum derived plastics and are becoming more common in the additive manufacturing field. Biobased fillers, such as bio-derived cellulose, lignin byproducts, and biochar, can be used to modify the thermal, mechanical, and electrical properties of polymer composites. Biochar (BioC), in particular, is of interest for enhancing thermal and electrical conductivities in composites, and can potentially serve as a bio-derived graphitic carbon alternative for certain composite applications. In this work, we investigate a blended biopolymer system: PLA/PHBV, and addition of carbon black (CB), a commonly used functional filler as a comparison for Kraft lignin-derived BioC. We present calculations and experimental results for phase-separation and nanofiller phase affinity in this system, indicating that the CB localizes in the PHBV phase of the immiscible PHBV:PLA blends. The addition of BioC led to a deleterious reaction with the biopolymers, as indicated by blend morphology, differential scanning calorimetry showing significant melting peak reduction for the PLA phase, and a reduction in melt viscosity. For the CB nanofilled composites, electrical conductivity and dynamic mechanical analysis supported the ability to use phase separation in these blends to tune the percolation of mechanical and electrical properties, with a minimum percolation threshold found for the 80:20 blends of 1.6 wt.% CB. At 2% BioC (approximately the percolation threshold for CB), the 80:20 BioC nanocomposites had a resistance of 3.43x10 8 Omega as compared to 2.99x10 8 Omega for the CB, indicating that BioC could potentially perform comparably to CB as a conductive nanofiller if the processing challenges can be overcome. Investigations into alkaline and dealkaline lignin sources have shown that alkaline lignin experiences a significant effect on the thermal stability of PHBV eluding that alternate sources of lignin may provide a solution to the processing challenges mentioned. This work has helped to develop a understanding of the factors that aid in creating sustainable materials sourced from PLA,PHBV, and BioC.Item Subnanosecond emission from model DNA oligomers characterized through time-correlated single-photon counting spectroscopy(Montana State University - Bozeman, College of Letters & Science, 2017) Skowron, David John; Chairperson, Graduate Committee: Robert Walker; Yuyuan Zhang, Ashley A. Beckstead, Jacob M. Remington, Madison Strawn and Bern Kohler were co-authors of the article, 'Subnanosecond emission dynamics of AT DNA oligonucleotides' in the journal 'Journal of chemical physics and physical chemistry' which is contained within this thesis.Exposure of DNA to UV radiation creates electronic excited states that can decay to mutagenic photoproducts. Excited states can return to the electron ground state through deactivation pathways, preventing photochemical damage. Understanding has significantly advanced over the last decade through the applications of time-resolved techniques capable of picosecond and femtosecond time-resolution. While significant strides have been made towards understanding monomeric deactivation pathways, unraveling the complex photophysics of base multimers still presents a significant challenge. This report uses time-resolved fluorescence and ultrafast transient absorbance to analyze model DNA oligomers to understand how fundamental interactions between monomeric constituents influences the dynamics of base multimers. Model single- and double-stranded DNA oligomers were investigated using the time correlated single photon counting technique to address the uncertainty over how to compare results from time-resolved fluorescent and transient absorption techniques. Emission lifetimes ranging from 50 to 200 ps quantitatively agree with lifetimes measured from transient absorption experiments indicating emission observed on timescales greater than a few picoseconds is the result of excimer or charge recombination luminescence. In attempts to further characterize the time-resolved emission from model oligomers adenine oligomers consisting of 2 and 18 base constituents were examined in aqueous water and heavy water solutions. Differences in dynamics between the two oligomers revealed the average number of bases present within a stacked domain influence the dynamics of these systems. Lifetimes of the emission decays were assigned excimer-like states with various degrees of charge-transfer character. Finally, to further demonstrate the importance of base stacking domain length on the dynamics of these systems, time-resolved emission and absorption of the adenine dinucleotide and 18-mer where examined at temperatures ranging from 7 °C - 80 °C. It was observed that the kinetics between the oligomers was noticeably different at lower temperatures, but not at higher temperatures. It was concluded the domain length of the 18-mer was similar to the domain length of the dinucleotide at high temperatures, but not at low temperatures, demonstrating the domain length significant impacts theS photophysics of DNA.Item Characterizing molecular dynamics of polymer glass and gel phase transitions as a function of time, temperature, and concentration using nuclear magnetic resonance(Montana State University - Bozeman, College of Engineering, 2016) Dower, April Marie; Chairperson, Graduate Committee: Joseph D. SeymourPolymers can be used for a variety of applications and impact many aspects of our lives. This thesis investigates the dynamics of polymer gel and glass transitions over different times, temperatures, and concentrations using nuclear magnetic resonance (NMR) with the goal of further understanding these important systems. A polymer/solvent system, hydroxypropylmethylcellulose acetate succinate (HPMCAS) and acetone, was examined using magnetic relaxation correlation and exchange experiments to characterize domains of different molecular mobility over various temperatures and concentrations. Diffusometry was employed to support the results of the 2D relaxometry experiments. A simple relaxometry method to determine glassiness was verified, and characteristic length scales of a polymer solution at different temperatures were quantified using both relaxation exchange methods and diffusion data. Glasslike dynamics were observed in gelled polymer systems above their glass transition temperatures. The thermal gelation properties of colloidal polymer dispersions and the effects of different formulations on dry film formation of a polymer mixture were studied as well. Aging and plasticizer effects were examined in the colloidal polymer dispersions using magnetic relaxation correlation experiments along with diffusion experiments to understand molecular dynamics, and it was concluded that pre-gelation particle aggregates were necessary for the systems to thermally gel. The final polymer study aimed to determine why a formulation using differently-substituted polymer produced dry films with dissimilar mechanical properties than another. Using relaxometry data and quantitative length scales acquired through relaxation exchange, it was found that one mixture retained larger domains of water upon dry film formation, allowing the film to be less brittle.Item Parametric study of cyclic loading effects on the creep behavior of polymers and polymer based composites(Montana State University - Bozeman, College of Engineering, 2000) Schumacher, Shane ChristianItem The adsorption of the mussel adhesive proteins of the marine mussel, Mytilus edulis, to polymer films(Montana State University - Bozeman, College of Engineering, 1995) Baty, Ace M.Item Modeling and analysis of thin-film, piezoelectric actuators(Montana State University - Bozeman, College of Engineering, 2000) Childs, Ashley Erin