Date of Award
Master of Science (MS)
Daryl K. Eggers
Alzheimer's Disease, Circular Dichroism, Huntington's Disease, Protein Aggregation, Sol-gel, Xerogel
Biochemistry; Biophysics; Chemistry
Protein aggregation has been linked to many debilitating neurological diseases. In each case, a specific protein is thought to have a region of intrinsically disordered structure that seeds the aggregation. Highly cooperative in nature, protein aggregation is difficult to investigate. The current study aims to characterize two aggregation-prone peptides involved in Huntington's disease, polyglutamine (polyQ, D2Q15K2), and Alzheimer's disease, amyloid-beta (A&beta). A protocol was developed to encapsulate the peptides by the sol-gel technique. Generated from a liquid state, the silica matrix is presumed to isolate the soluble peptide, preventing aggregation. In addition, the porosity of the glass allows the solvent conditions to be altered. The peptides were characterized by circular dichroism spectroscopy (CD). In solution, both peptides were most aggregation-prone when they contained the least amount of secondary structure. Encapsulated polyQ showed unique pH-dependent spectra not seen in solution. A&beta was able to take on both a random coil and an apparent beta structure in 5% hexafluoroisopropanol (HFIP), depending on the prior solvent, indicating two semi-stable states of similar energy. The results for both peptides show that (1) the encapsulated peptides can adopt a significant amount of helical secondary structure, (2) the secondary structure can be altered by varying the solution, temperature, and pH, and (3) most changes in structure appear to be reversible. These results are consistent with the absence of aggregation in the encapsulated samples.
Birtwhistle, Nathan James, "Analysis of Sol-Gel Encapsulated Aggregate-Prone Peptides by Circular Dichroism" (2012). Master's Theses. Paper 4122.