Browsing by Author "Fawcett, Liam"

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    Characterizing the Changes to Protein Sorption to Photodegraded Polyethylene (2021-04-09)
    (2021) Fawcett, Liam; University of Minnesota Duluth. Department of Chemistry and Biochemistry
    Aft er their entry into the environment, plastics are exposed to a multitude ofabiotic environmental factors that change both their physical and chemicalcharacteristics. While the initiation of biotic degradation on pristine polymershas been reviewed, it is generally accepted that biotic degradation is enhancedon polymers that initially have undergone some sort of abiotic degradation,particularly photodegradation. This work seeks to understand the intricacies ofbacterial interactions with plastics by investigating the interaction of proteins topolymers with increasing extents of photodegradation, which should giveinsight into the potential attachment and biofilm formation on plastic debrismaterials. Using bovine serum albumin (BSA) as a model protein, we haveinitially investigated the changes in structural characteristics and fluorescenceof the model protein as it adsorbs onto the surface of irradiated polyethylene.Changes to the secondary structure characteristics of BSA were monitoredthrough circular dichroism and preliminary data has shown that with anincrease in irradiation time, there is a characteristic shift of the 3.6 ?-helices tomore tightly wound 3.10 ?-helices. This is likely due to the increasedhydrophilicity of photodegraded polymers causing the hydrophobic residues towind more tightly. Fluorescence of the tryptophan’s in BSA shows a decreasewith exposure to the polymers regardless of irradiation time, indicating potentialfluorescence quenching from the surface of the polymer. Overall, these resultsindicate that an increase polyethylene irradiation time causes an increase ininteraction strength between the polymer and protein, which may explain howbiotic degradation is increased with abiotically degraded polymers. Ultimatelythis work will contribute to our understanding of the fate of plastics in theenvironment.
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    Understanding and Quantifying the Role of Polyethylene Photodegradation in Altering Protein Adsorption.
    (2021-08) Fawcett, Liam
    Due to its desirable physical and chemical characteristics and low production costs, plastics have become an extremely desirable product for both industrial and consumer purposes. However, due to these same desirable characteristics and improper disposal avenues, plastics have become an environmental concern, particularly their impact on ecosystems. Once plastics enter the environment, there are synergistic driving forces that cause weathering. While many of the degradation pathways of polymers in the environment are well documented the interplay between abiotic and biotic degradation are not well understood. In this work, the role of polyethylene’s photodegradation on protein adsorption are investigated. Protein adsorption is a key step in biofilm formation and biotic degradation of polymers. This work specifically focuses on the model protein BSA and its adsorption to PE. Through investigative spectroscopic techniques (i.e., fluorescence and circular dichroism), it was shown that an increase in hydrophilicity caused by photodegradation of the polymers’ surface, caused less perturbation of the local environment of the tryptophan residues. It was also observed that there was larger structural frustration and rearrangement of the protein upon binding to PE at points during photodegradation, where there were significant changes in the chemical and physical properties. Depending on the inherent protein stability, larger structural changes upon surface binding indicate an increase in adsorption strength. Environmentally, this signifies an increase in biofilm strength at the transition points in polymer photodegradation leading to a potential increase in the rate of biodegradation.