Theses and Dissertations from UMD

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New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM

More information is available at Theses and Dissertations at University of Maryland Libraries.

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    PROBING BIOPHYSICAL PROPERTIES OF THERAPEUTIC PROTEIN AGGREGATES WITH INTERFEROMETRIC SCATTERING MICROSCOPY
    (2021) Wong, Nathan A; Woehl, Taylor J; Chemical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    A growing biopharmaceutical market increases the importance of therapeutic proteins, of which monoclonal antibodies (mAb) are the largest category. Protein aggregation in biopharmaceutical production has important consequences in mAb immunogenicity. Submicron (100-1000 nm) protein aggregates in particular are a key challenge due to their higher immunogenicity and the relative lack of analytical methods capable of characterizing them. We propose the use of interferometric scattering (IFS) microscopy as a simple and potentially high-throughput orthogonal characterization method of submicron aggregates. We demonstrate its utility by testing two variants of IFS microscopy: (1) Correlative IFS and fluorescence microscopy (2) hyperspectral interferometric scattering (h-IFS) microscopy. Using correlative IFS and fluorescence microscopy, we characterize the size and surface structure of a stirred protein aggregate sample. We find that smaller protein aggregates (~100 nm) have higher surface concentrations of Fc domains and hydrophobic regions. Then, we demonstrate the usage of h-IFS microscopy to differentiate and quantify protein aggregates and contaminants in biologic drugs.  
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    Nature of Mesoscopic Aggregates in Solutions of Lysozyme
    (2018) NIKFARJAM, SHAKIBA; Woehl, Taylor J; Anisimov, Mikhail; Chemical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    An anomalous class of mesoscopic aggregates have previously been observed in solutions of lysozyme. These aggregates are thought to play an important role in nucleation of protein crystals and ordered protein aggregates, like amyloid fibers. Mesoscopic aggregates are currently thought to be in thermodynamic equilibrium with the protein solution, where transient oligomers of partially unfolded lysozyme monomers are thought to be the formation source of these aggregates. However, there is little experimental evidence to back up this proposed formation mechanism and thermodynamic behavior. Specifically, the effects of temperature on these aggregates and their thermodynamic reversibility have not been systematically tested. In this thesis, we investigate the equilibrium nature and the formation source of mesoscopic aggregates in solutions of model protein, lysozyme. We tested the effects of temperature on aggregate size and concentration and the aggregate reversibility after removal by systematic filtration. We used light and x-ray scattering and chromatography to experimentally characterize the aggregates during this study. Our findings indicate that mesoscopic aggregates are minimally sensitive to temperature changes and do not reform after removal by filtration. Together, these results indicate that mesoscopic aggregates are not in thermodynamic equilibrium with protein monomers or oligomers in solution. Overall, our experimental results contrast the current accepted formation mechanism of these mesoscopic aggregates and suggest they instead form due to contaminants present in solution or a sub-population of partially unfolded proteins.