Matching Items (4)
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- All Subjects: electrochemistry
- All Subjects: Separations
- Creators: Hayes, Mark A.
Description
Bioparticles comprise a diverse amount of materials ubiquitously present in nature. From proteins to aerosolized biological debris, bioparticles have important roles spanning from regulating cellular functions to possibly influencing global climate. Understanding their structures, functions, and properties provides the necessary tools to expand our fundamental knowledge of biological systems and exploit them for useful applications. In order to contribute to this efforts, the work presented in this dissertation focuses on the study of electrokinetic properties of liposomes and novel applications of bioaerosol analysis. Using immobilized lipid vesicles under the influence of modest (less than 100 V/cm) electric fields, a novel strategy for bionanotubule fabrication with superior throughput and simplicity was developed. Fluorescence and bright field microscopy was used to describe the formation of these bilayer-bound cylindrical structures, which have been previously identified in nature (playing crucial roles in intercellular communication) and made synthetically by direct mechanical manipulation of membranes. In the biological context, the results of this work suggest that mechanical electrostatic interaction may play a role in the shape and function of individual biological membranes and networks of membrane-bound structures. A second project involving liposomes focused on membrane potential measurements in vesicles containing trans-membrane pH gradients. These types of gradients consist of differential charge states in the lipid bilayer leaflets, which have been shown to greatly influence the efficacy of drug targeting and the treatment of diseases such as cancer. Here, these systems are qualitatively and quantitatively assessed by using voltage-sensitive membrane dyes and fluorescence spectroscopy. Bioaerosol studies involved exploring the feasibility of a fingerprinting technology based on current understanding of cellular debris in aerosols and arguments regarding sampling, sensitivity, separations and detection schemes of these debris. Aerosolized particles of cellular material and proteins emitted by humans, animals and plants can be considered information-rich packets that carry biochemical information specific to the living organisms present in the collection settings. These materials could potentially be exploited for identification purposes. Preliminary studies evaluated protein concentration trends in both indoor and outdoor locations. Results indicated that concentrations correlate to certain conditions of the collection environment (e.g. extent of human presence), supporting the idea that bioaerosol fingerprinting is possible.
ContributorsCastillo Gutiérrez, Josemar Andreina (Author) / Hayes, Mark A. (Thesis advisor) / Herckes, Pierre (Committee member) / Ghrilanda, Giovanna (Committee member) / Arizona State University (Publisher)
Created2011
Description
Dielectrophoresis (DEP) is a technique that influences the motion of polarizable particles in an electric field gradient. DEP can be combined with other effects that influence the motion of a particle in a microchannel, such as electrophoresis and electroosmosis. Together, these three can be used to probe properties of an analyte, including charge, conductivity, and zeta potential. DEP shows promise as a high-resolution differentiation and separation method, with the ability to distinguish between subtly-different populations. This, combined with the fast (on the order of minutes) analysis times offered by the technique, lend it many of the features necessary to be used in rapid diagnostics and point-of-care devices.
Here, a mathematical model of dielectrophoretic data is presented to connect analyte properties with data features, including the intercept and slope, enabling DEP to be used in applications which require this information. The promise of DEP to distinguish between analytes with small differences is illustrated with antibiotic resistant bacteria. The DEP system is shown to differentiate between methicillin-resistant and susceptible Staphylococcus aureus. This differentiation was achieved both label free and with bacteria that had been fluorescently-labeled. Klebsiella pneumoniae carbapenemase-positive and negative Klebsiella pneumoniae were also distinguished, demonstrating the differentiation for a different mechanism of antibiotic resistance. Differences in dielectrophoretic behavior as displayed by S. aureus and K. pneumoniae were also shown by Staphylococcus epidermidis. These differences were exploited for a separation in space of gentamicin-resistant and -susceptible S. epidermidis. Besides establishing the ability of DEP to distinguish between populations with small biophysical differences, these studies illustrate the possibility for the use of DEP in applications such as rapid diagnostics.
Here, a mathematical model of dielectrophoretic data is presented to connect analyte properties with data features, including the intercept and slope, enabling DEP to be used in applications which require this information. The promise of DEP to distinguish between analytes with small differences is illustrated with antibiotic resistant bacteria. The DEP system is shown to differentiate between methicillin-resistant and susceptible Staphylococcus aureus. This differentiation was achieved both label free and with bacteria that had been fluorescently-labeled. Klebsiella pneumoniae carbapenemase-positive and negative Klebsiella pneumoniae were also distinguished, demonstrating the differentiation for a different mechanism of antibiotic resistance. Differences in dielectrophoretic behavior as displayed by S. aureus and K. pneumoniae were also shown by Staphylococcus epidermidis. These differences were exploited for a separation in space of gentamicin-resistant and -susceptible S. epidermidis. Besides establishing the ability of DEP to distinguish between populations with small biophysical differences, these studies illustrate the possibility for the use of DEP in applications such as rapid diagnostics.
ContributorsHilton, Shannon (Author) / Hayes, Mark A. (Thesis advisor) / Borges, Chad (Committee member) / Herckes, Pierre (Committee member) / Arizona State University (Publisher)
Created2019
Description
Metal-organic frameworks (MOFs) are a new set of porous materials comprised of metals or metal clusters bonded together in a coordination system by organic linkers. They are becoming popular for gas separations due to their abilities to be tailored toward specific applications. Zirconium MOFs in particular are known for their high stability under standard temperature and pressure due to the strength of the Zirconium-Oxygen coordination bond. However, the acid modulator needed to ensure long range order of the product also prevents complete linker deprotonation. This leads to a powder product that cannot easily be incorporated into continuous MOF membranes. This study therefore implemented a new bi-phase synthesis technique with a deprotonating agent to achieve intergrowth in UiO-66 membranes. Crystal intergrowth will allow for effective gas separations and future permeation testing. During experimentation, successful intergrown UiO-66 membranes were synthesized and characterized. The degree of intergrowth and crystal orientations varied with changing deprotonating agent concentration, modulator concentration, and ligand:modulator ratios. Further studies will focus on achieving the same results on porous substrates.
ContributorsClose, Emily Charlotte (Author) / Mu, Bin (Thesis director) / Shan, Bohan (Committee member) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2016-12
Description
Oxidoreductases catalyze transformations important in both bioenergetics and microbial technologies. Nonetheless, questions remain about how to tune them to modulate properties such as preference for catalysis in the oxidative or reductive direction, the potential range of activity, or coupling of multiple reactions. Using protein film electrochemistry, the features that control these properties are defined by comparing the activities of five [FeFe]-hydrogenases and two thiosulfate reductases. Although [FeFe]-hydrogenases are largely described as hydrogen evolution catalysts, the catalytic bias of [FeFe]-hydrogenases, i.e. the ratio of maximal reductive to oxidative activities, spans more than six orders of magnitude. At one extreme, two [FeFe]-hdyrogenases, Clostridium pasteuriaunum HydAII and Clostridium symbiosum HydY, are far more active for hydrogen oxidation than hydrogen evolution. On the other extreme, Clostridium pasteurianum HydAI and Clostridium acetobutylicum HydA1 have a neutral bias, in which both proton reduction and hydrogen oxidation are efficient. By investigating a collection of site-directed mutants, it is shown that the catalytic bias of [FeFe]-hydrogenases is not trivially correlated with the identities of residues in the primary or secondary coordination sphere. On the other hand, the catalytic bias of Clostridium acetobutylicum HydAI can be modulated via mutation of an amino acid residue coordinating the terminal [FeS] cluster. Simulations suggest that this change in catalytic bias may be linked to the reduction potential of the cluster.
Two of the enzymes examined in this work, Clostridium pasteurianum HydAIII and Clostridium symbiosum HydY, display novel catalytic properties. HydY is exclusively a hydrogen oxidizing catalyst, and it couples this activity to peroxide reduction activity at a rubrerythrin center in the same enzyme. On the other hand, CpIII operates only in a narrow potential window, inactivating at oxidizing potentials. This suggests it plays a novel physiological role that has not yet been identified. Finally, the electrocatalytic properties of Pyrobaculum aerophilum thiosulfate reductase with either Mo or W in the active site are compared. In both cases, the onset of catalysis corresponds to reduction of the active site. Overall, the Mo enzyme is more active, and reduces thiosulfate with less overpotential.
Two of the enzymes examined in this work, Clostridium pasteurianum HydAIII and Clostridium symbiosum HydY, display novel catalytic properties. HydY is exclusively a hydrogen oxidizing catalyst, and it couples this activity to peroxide reduction activity at a rubrerythrin center in the same enzyme. On the other hand, CpIII operates only in a narrow potential window, inactivating at oxidizing potentials. This suggests it plays a novel physiological role that has not yet been identified. Finally, the electrocatalytic properties of Pyrobaculum aerophilum thiosulfate reductase with either Mo or W in the active site are compared. In both cases, the onset of catalysis corresponds to reduction of the active site. Overall, the Mo enzyme is more active, and reduces thiosulfate with less overpotential.
ContributorsWilliams, Samuel Garrett (Author) / Jones, Anne K (Thesis advisor) / Hayes, Mark A. (Committee member) / Trovitch, Ryan J (Committee member) / Arizona State University (Publisher)
Created2020