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Title: Investigation of amyloid aggregate formation in various protein systems
Author: Cannon, D.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2011
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This thesis investigates the self assembly of rod-like aggregates termed amyloid fibrils and higher ordered spherical aggregates known as spherulites in various protein systems. The overall theme is to develop an understanding of the mechanism of formation of these structures using in vitro proteins for models. Four proteins in total were studied for comparison: insulin, β-lactoglobulin, hen egg white lysozyme and amyloid-β. Studies on β-lactoglobulin and hen egg white lysozyme showed that the formation of amyloid aggregates occurred on the same time scale as the degradation of the protein molecules. Defined fragment masses were observed and increased in number with increasing incubation time of the proteins. This has lead to the observation that protein degradation may play a key role in amyloid formation. Stirring insulin, β-lactoglobulin, and hen egg white lysozyme samples during incubation altered the phase state of the in vitro fibrils via modification of the fibril aspect ratio. Higher stirring rates led to shorter fibrils and lower amounts of liquid crystallinity. This technique can prevent spherulites from forming and instead form aligned amyloid fibrils producing liquid-crystal like regions. Amyloid-β(1-40) and (1-42) has the ability to form spherulites in vitro under very specific conditions. This is the first observation of spherulites in this peptide which resemble those that readily form in insulin, β-lactoglobulin and hen egg white lysozyme which show the characteristic Maltese cross pattern when viewed between crossed polarisers. Finally, the secondary structure of spherulites formed in insulin, β-lactoglobulin and amyloid-β(1-40) was studied using Raman spectroscopy. This has shown direct similarities between insulin and amyloid-β(1-40). Both show a core which contains a higher proportion of amorphous material, with fibrils that grow radially from the core. BLG spherulites have a less well defined core, the fibrils which twist as they radiate from the centre.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available