Seeding Induced Assembly of Ionic-Complementary Peptide EAK16-II

I herby declare that I am the sole author of this thesis. This is a true copy of the thesis, including any required final revisions, as accepted by my examiners. I understand that my thesis may be made electronically available to the public. iii ABSTRACT Seeding is an important variable in controlling or directing the assembly of peptides. The presence of impurities, responsible for creating a 'dip' in the surface tension versus peptide concentration profile, is used to determine the critical aggregation concentration (CAC). This phenomenon is investigated to differentiate crude and high purity EAK16-II peptide. The purified peptide did not show this 'dip' and clearly indicated a critical aggregation concentration for EAK16-II at 0.09 mg/mL by surface tension measurements. Conversely, a surface tension 'dip' is clearly observed for the crude EAK16-II peptide. Atomic Force Microscopy imaged the nanostructures of aggregates. The presence of impurities induces fibre formation below the CAC. This study provides information about the seeding effect of peptide assembly at low concentrations as well as the modification of surface activity of assembled peptide particles. Alanine, glutamic acid and lysine were used as model seeding agents to simulate the seeding phenomenon and better understand the nucleation mechanism of peptide assembly. All amino acid monomers were able to induce fibre formations at low peptide concentrations. However, only glutamic acid and lysine were able to produce the surface tension dip profile observed in the crude peptide. This information may be of importance in understanding fibrillogenesis occurring in conformational diseases and other biomedical applications including drug delivery. iv ACKNOWLEDGMENTS