Date of Award


Document Type


Degree Name

Master of Science (MS)


Biomedical and Chemical Engineering and Sciences

First Advisor

Shaohua Xu

Second Advisor

Melissa A. Borgen

Third Advisor

James R. Brenner

Fourth Advisor

Manolis M. Tomadakis


The aggregation of proteins to form fibrillar deposits is a hallmark of numerous medical conditions, including Alzheimer’s Disease (AD). Protein monomers aggregate to form amyloid fibers, followed by these fibers further aggregating to form larger structures such as fiber bundles and hydrogels. Previous studies into protein aggregation were mostly done under dilute solutions that poorly reflect the crowded nature of the tissue environment. Can a liquid solution truthfully represent what is going on in a solid tissue? Utilizing lysozyme as a model protein and two different polysaccharides as crowding agents, dextran and hyaluronic acid (HA), the effects of macromolecular crowding on the formation of lysozyme amyloid fibers, fiber bundles, and hydrogels were examined. Samples containing lysozyme, along with varying concentrations of dextran and HA, were monitored for fiber formation and gelation. Amyloid fiber formation was quantified by thioflavin T assay. Resulting hydrogels were examined for fiber bundles via light microscopy, and the dimensions of bundles synthesized under different conditions were compared. Dextran / HA slowed the formation of lysozyme fibers and hydrogels, and also appeared to promote the formation of slightly shorter fiber bundles. These mentioned effects are analyzed in the crowding agents’ potential (1) as kosmotropic agents to promote hydrophobic interactions and inhibit lysozyme unfolding, (2) as viscosity-inducing agents to reduce the collision of monomers and colloids and thus their aggregation, and (3) as charged polyanions to form HA and lysozyme complexes via ionic interactions.


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